The URL can be used to link to this page

Home My WebLink About4-27-2015 Complete WRAB Packet WATER RESOURCES ADVISORY BOARD MEETING MEETING DATE: Monday, 27 April 2015 MEETING TIME: 7:00 p.m. MEETING LOCATION: Municipal Services Center, 5050 Pearl St., Boulder, CO 80301 Agenda Highlights: 1.Call to Order (7:00 p.m.) 2.Approval of 16 March Meeting Minutes (7:01 p.m.) 3.Swearing In/Election of Officers (7:05 p.m.) 4.*Public comment (7:15 p.m.) 5.*Public Hearing and Consideration of a Recommendation to City Council Regarding the Gregory Creek Mitigation Study (7:30 p.m.) 6.Information Item 2016 Capital Improvement Program Overview (8:15 p.m.) 7.Matters from Board (9:30 p.m.) 8.Matters from Staff (9:40 p.m.) 9.Discussion of Future Schedule (9:50 p.m.) 10.Adjournment (10:00 p.m.) *Additional Information Items: Bear Canyon Creek Informational Memo Drought Response and Water Supply Memo * Public Comment Item Agenda item times are approximate. Information: Please contact the WRAB Secretary email group at: WRABSecretary@bouldercolorado.gov Packets are available on-line at: http://www.bouldercolorado.govA to ZWater , Resources Advisory Board (WRAB), Next Water Resources Advisory Board Meeting CITY OF BOULDER, COLORADO BOARDS AND COMMISSIONS MEETING MINUTES Name of Board / Commission: Water Resources Advisory Board Date of Meeting: 16 March 2015 Contact Information of Person Preparing Minutes: Andrea Flanagan 303.413.7372 Board Members Present: Vicki Scharnhorst, Mark Squillace, Dan Johnson, Lesley Smith, Ed Clancy Board Members Absent: None Staff Present: Jeff Arthur, Director of Public Works for Utilities Bob Harberg, Principal Engineer-Utilities Annie Nobel, Flood and Greenways Engineering Program Coordinator Bret Linenfelser, Water Quality and Environmental Services Manager Kurt Bauer, Engineering Project Manager Kristin Dean, Utilities Planner Christin Shepherd, Civil Engineer Andrea Flanagan, Board Secretary Cooperating Agencies Present: Craig Jacobson, Consultant with ICON Engineering, Inc. Brian Ledoux, Consultant with ICON Engineering, Inc. Shea Thomas, Urban Drainage and Flood Control District Meeting Type: Regular Agenda Item 1 Call to Order [7:00 p.m.] Agenda Item 2 Approval of the 23 February 2015 Meeting Minutes: [7:01 p.m.] Motion to approve minutes as amended from February 23 as presented. Moved by: Seconded by: Squillace; Johnson Vote: 5:0 Agenda Item 3 Public Participation and Comment [7:05 p.m.] Public Comment: Carl Norby Resident of Frasier Meadows. Provided a letter to board secretary that he read aloud to the Board. August 28 th, 2014 the supervisor for C&L to install the last section of sewer line for Frasier Meadows lining project. Carl showed the inspector the ground water level line, which is 22 inches below the basement floor in his home. The inspector said he would replace the line but not cure it until he was certain that the basement would not flood. The pump was turned on and working every few minutes in order to maintain the 17 inch water level The ground water level has been stable for the past 40 years. He has experienced minimal moisture in the basement area since flood event. It was recently discovered that groundwater is leaking into the base of a nearby manhole due to the increased groundwater levels, causing the water level to rise another five inches. entered between wall and floor. Seems logical for something like this to happen again. He requests that a Hydrologist evaluate the groundwater in the Frasier Meadows area. Fleet White Basement flooded a week ago. No question in his mind based on behavior of sump pump that ground water has risen significantly since last summer. Likely cause is lining of neighb system. He attributes rise in groundwater to this. With recent rapid melt of heavy snow, they had dramatic rise in groundwater, as clearly indicated by operation of sump pump. His understanding is that there was no analysis or study on what the hydrological impact would be in the area with the lining of the sanitary sewer. Suggests that the city look into this issue further. Lining the sewer to the homes will likely will have further impact on level of ground water. Requests city give consideration to this impact. He has a deep basement and will experience flooding again in the future. Rick Mahan Representing South Boulder Creek Action Group sentation. Primary goal is to prevent issues to the health and public safety to residents with regard to US36. Extends invitation to board WRAB Minutes 16 March 2015 Page No. 1 members to viethat discusses the overtopping in 2013 at US36 and addresses health and public safety concerns. again in the future. Agenda Item 4 [7:12 p.m.] Public Hearing and Consideration of a Recommendation to City Council regarding the Upper Goose Creek and Twomile Canyon Creek Floodplain Mapping Update Kurt Bauer and Utilities staff presented the item to the board. Executive Summary from the Packet Materials: The purpose of this memorandum is to provide a brief summary of the history and revised results of the Upper Goose Creek and Twomile Canyon Creek floodplain remapping study and request a motion from the WRAB to recommend to City Council to adopt the mapping. The study includes the area located west of Folsom Street to the city limits as shown by the blue areas in the figure below: The Upper Goose Creek and Twomile Canyon Creek floodplain mapping update began in 2011. The initial draft revised mapping was presented to WRAB in May 2013. Based on a WRAB recommendation, the mapping was remodeled using the new city LiDAR topographic mapping information and presented to WRAB on November 17, 2014. The maps have been further revisited and revised to address issues raised by the public and the WRAB including changes to the High Hazard Zone, Conveyance Zone and limited changes to the 100-year floodplain. As a result of these changes, no structures would be located in the revised draft High Hazard Zone, 13 structures would no longer be added to the Conveyance Zone and 15 structures would no longer be added to the 100-year floodplain. The proposed Upper Goose Creek and Twomile Canyon Creek floodplain mapping would result in a net: Decrease of 130 structures identified in the 100-year floodplain; Decrease of 97 structures identified in the Conveyance Zone and; Decrease of 64 structures identified in the High Hazard Zone. The WRAB review of the floodplain mapping update does not require board members to verify the analysis and calculations, but accepts the overall mapping study process and that results are reasonable and acceptable. The WRAB is being asked to make a recommendation to City Council on whether to adopt the mapping update and forward it for consideration by FEMA. WRAB Discussion Included: Re Questioned if GIS and standard approaches were used to make selections without doing onsite mapping. Asked whether or not fences are mapped. Commented that surprised that the models were one-dimensional and asked if that is the recommended approach to mapping for regulatory purposes. Curious about changes with Crestview and Foothills Elementary School and what that means for the school with regard to expansion. WRAB Minutes 16 March 2015 Page No. 2 Reminded audience that the 2013 flood event was a very different scenario then what is being mapped in the current study. Questioned related to policy updates that would include the new technology and modeling and what that would look like. Questioned whether the model includes the berm in front of Foothills and Crestview Elementary Schools. Questioned whether additional input was received from other firms and incorporated into the study. Requested clarification on changes to the high hazard zone with regard to Blue Bell and Gregory Canyon models and if they were in fact 1-D models? Questioned if it is likely for a 2- D model to be requested as well. Commends staff and feels that the continuous discussions about Twomile Creek mapping has been productive and staff has been very responsive throughout this process. These discussions have put us in a much better place to make better informed decisions regarding these important changes. Questioned how the city should proceed with providing information about flood risk, even if they are no longer in the floodplain Question about Urban Drainage and if other agencies have experience using the 1-D vs. 2-D model responses. Question about suggestion by audience member about adding sidewalks on Juniper, Kalmia and Linden Ave. and about the possibility of using streets as conveyances? Requests also doing this on Evergreen, if so. Stated that there are multiple ways that residents can collaborate with staff regarding the process of tweaking individual site parcels. Public Comment: Len Berg Has been following procedures over the past 2 years. Property is not in new flood zone. Impact financially is significant. Has spent $17,400 on flood insurance over the past 14 years. Considering the scientific research that has been conducted, he implores the Board to get this approved and on to Council so he can move on. He is interested in updating his 16-year old house, but he is experiencing restrictions as to what he can do to update it due to this designation. Jonathan Hager Is part of the 275 residents who are being removed from the floodplain mapping. Excited because there is light at the end of the tunnel. His employer uses LiDAR mapping on transmission lines, which is incredibly accurate and cutting edge. He feels intuitively that his home is not in the floodplain and feels it would be unfair to pay flood insurance, so he appreciates Board taking burden off of these 275 residents. Kirk R. Vincent, PhD Has experience as hazard geologist and hydrologist. States that the Two-mile Creek area, west of Broadway, between Linden and past Juniper is unique area in town and most resembles an un-urbanized state because it does not have any sidewalks or culverts. Uncertainty in knowing where floodwaters will actually go. The results could most resemble terrible flood of 1909, as well as in 2013. Floodwaters took up a much larger area than what was depicted on the map. Objection is that the section of the acting channel between Kalmia and Broadway is being excluded from the floodplain. Feels that this would be a nationally unprecedented policy change. Encourages the city to designate Linden, Kalmia and Juniper to be the flood overflow channel and shunt the water to Broadway, rather than letting floodwater flow Peter Mayer Spoke to Board in November. Home was touched by water in 2013 and then removed from high hazard zone in the reanalysis. Feels this is a much more fair assessment and is very grateful for the revision. Feels that there is still a discrepancy with what he observed in 2013 from what was mapped. Did WRAB Minutes 16 March 2015 Page No. 3 research on 1-dimensional modeling verses 2-dimensional and urges city to utilize both models. Does not feel there are fatal flaws and does not feel this is ever going to be a perfect process. John Gerstle Has had a variety interactions with staff with regard to this process. House remained completely dry during the flood. Was interested to find out how their home would be classified in the revised modeling. Staff visited in February and maps were provided showing the status of his house in relationship to the floodplain and conveyance zone. He was pleased with the findings, but then in March, they were told that the status had changed and that his home was now in the floodplain again. Not enough time to act, as he was out of town. Feels it would be premature to adopt these plans now without the ability for those affected to have more interaction with staff about these revisions. Requests the option be considered for these residents to have more time. Steve Silberman Feels the revised maps are fantastic and his home is now being removed from high hazard and conveyance zones. Residents have not had a chance to talk about the event with each other. Debris blocked easement during the flood. Residents dug channel so water could drain, which it did once cleared. Water then drained within hours. Concerned that conveyance drawn for Alpine is too broad on these mapsthe grading in this area and take this into consideration. Tim Martin Lives behind Columbine Elementary. Received letters in 2013 that their home fell in flood zone. Did not observe flooding in the areas of 19 th, Floral and 20 th during the 2013 event. Based on his experience, his home is not in the flood zone. Thanks the Board for volunteering for this effort. It is important that people know accurately whether or not they fall in the flood zone. Read comments on previous minutes and questions whether or not those comments have been addressed. The majority of the people affected want to move forward. Concerned that FEMA may take up to 3 years to approve this data. Recommends moving it forward quickly. Heart goes out to residents whose homes are now in the flood zone. Luciano Mazzaro Was in the 100-year floodplain. Thanks everyone for being honest, as it is very important to say where we were before and where we are now. As an engineer, he knows that this simulation is just a model that will never be perfect. Has no hesitation that a 2-D model would be better than a 1-dimensional model. States that residents should feel good that this process has happened. This is about safety and he appreciates all that the Board has done throughout this process. Patrick Cameron Thanks Board and Kurt for their efforts. Deck was originally mapped in high hazard zone. Resident feedback was very helpful to help mitigate issues on property. The recent decision to remove the deck from the high hazard zone makes sense and is impactful. Julia Hicks Huge amount of repairs were done to home due to flood damage. Experienced massive river in backyard and in street, which is partially due to high grade of backyard. Home is now out of flood zone, er that their home actually did flood during this event. Jane Monson Home was in high hazard zone in the 2014 zoning map. Received notice right before Christmas that they were removed from the high hazard zone as a result of models not correlating. Would like to remind the Board that Wright Water did a study after the flood event and even though this was close-to a 100-year flood, their home experienced nothing close to what would be a high hazard experience on their property. Very happy to hear that high hazard was taken off property and urges Board to approve this motion. Motion by: ; Seconded: JohnsonSquillace WRAB Minutes 16 March 2015 Page No. 4 Vote: 5:0, Motion Passes Motion to recommend that City Council adopt the Upper Goose Creek and Twomile Canyon Creek floodplain mapping update. Agenda Item 5 Matters from the Board: [8:33 p.m.] Board Member Smith brought up the below matter(s): States that happy the issue was brought up about sewage back- and happy that lining process was sped up as a result of these issues. Expressed that pleased to hear that liaison is being hired to explor concerns. Requested clarification on when open houses will take place for community engagement. Discussed questions that were asked when recently presenting at Colorado Foundation for Water Conservation. Discussed that every citizen should know how much water they use and how to read their utility bill. Suggested that further articulation should be made about the structure that is trying to be developed. Board Member Squillace brought up the below matter(s): Stated that it was useful to learn about when it is valuable to do additional analysis. Stated that had the city delayed the analysis, the Board may have made a different decision, even if it were known that the water table was going to rise as a result of sewer lining efforts. Discussed that going forward, we look ahead at potential consequences and available alternatives. Requested further clarification on overall purpose of rate structure changes. Board Member Johnson brought up the below matter(s): Requested additional information on rate structure for stormwater. nd Commented that on March 2, met with South Boulder Creek Action Group. Discussed issues that the group are facing and listened to presentation. Feels that it was a productive meeting. Questioned why the city is choosing to do the rate restructure assessment now? Questioned the importance and timing of community engagement regarding rate structure changes. Board Member Clancy brought up the below matter(s): Requested that sump pumps be added to future agenda. how to better manage groundwater issues and education about sump pumps. Questioned if the city gives incentives to residents to get sump pumps? Requested confirmation that July is when someone would be hired to assist with community engagement. Questioned whether area near Frasier Meadows where pipes appear to be draining and causing rise in water table are being targeted. Questioned whether sewer manhole covers supposed to be sealed? Sees at all. Questioned how Urban Drainage helps financially towards projects and if we are receiving additional income for those. Agenda Item 6 Matters from Staff: [8:48 p.m.] March 17, Council will hold elections for newly appointed WRAB member. Douglas Sullivan will become Acting Principal Engineer for Water, Wastewater, and Stormwater and Annie Noble will become Acting Principal Engineer for Flood and Greenways Discussion on future scheduled WRAB meetings and upcoming availability. WRAB Minutes 16 March 2015 Page No. 5 Eric Ameigh approached board about public engagement process and requested feedback from Board about memos that were sent in February. Two open house events will be scheduled, with the intention of gathering feedback from the public about their utility bills, as well as other general feedback. An additional opportunity for obtaining feedback online for residents who cannot attend open houses will be provided. Agenda Item 7 Future Schedule [9:18 p.m.] Due to a high volume of information items projected for the next couple of months, some items will be presented only as memos and questions will be discussed under matters. April: Annual drought status and water supply update will be presented in the form of a memo Presentation on Capital Improvements Overview Board recommendation on Gregory Creek Mitigation Bear Creek Mitigation will be presented in the form of a memo April will be first meeting for new board member Board will be contacted to determine if a quorum will be met for forthcoming spring and summer meetings, otherwise may need to reschedule meetings. Adjournment [9:22 p.m.] There being no further business to come before the Board at this time, by motion regularly adopted, the meeting was adjourned at 9:22p.m. Motion to adjourn by:; Seconded by: SquillaceSmith Motion Passes 5:0 Date, Time, and Location of Next Meeting: Monday, 27 April 20157:00 p.m.,City's Municipal The next WRAB meeting will be at at the Services Center, 5050 Pearl St., Boulder, CO 80301 APPROVED BY: ATTESTED BY: _______________________________ __________________________________ Board Chair Board Secretary _____________________________ ___________________________________ Date Date An audio recording of the full meeting for which these minutes are a summary, is available on the Water Resources Advisory Board web page. https://bouldercolorado.gov/boards-commissions/water-resources-advisory-board-next-meeting-agenda-and-packet WRAB Minutes 16 March 2015 Page No. 6 Draft Draft Draft Draft Draft Draft Draft Draft Draft K K K ? '300)+) K ? K K K MEMORANDUM Alternative Analysis Memorandum CityofBoulder PREPARED FOR: UrbanDrainageandFlood COPY TO: ControlDistrict CH2MHILL PREPARED BY: March18,2015 DATE: 482330 PROJECT NUMBER: InSeptember2013,theCityofBoulderexperiencedanintenserainfalleventbetweenSeptember9and September18,approximately10days.ThisrainfalleventgeneratedfloodinginandaroundtheCityof Boulder,includingtheareaalongandadjacenttoGregoryCanyonCreek.GregoryCanyonCreekisaright adway.Duringthestormeventof2013,manyresidents banktributarythatentersBoulderCreekwestofBro experienceddamagetotheirpropertyduetohighfloodwatersaswellasobservedfloodinginpublic roadways.TheextentsoftheobservedfloodingisdocumentedinFigure1. CH2MHILLwasretainedbytheCityofBouldertoevaluatepote ntialalternativestohelpalleviateflooding alongGregoryCanyonCreek.ThepurposeofthisAlternativeAnalysisMemorandumfortheGregoryCanyon CreekMajorDrainagewayPlan(Study)istopresentthefindingsofthehydraulicanalysis,defineproblem areas,anddeveloppreliminarycategoriestomitigatefloodhazardswithinthebasin. Project Location GregoryCanyonCreekwatershedislocatedintheCityofBoulder(City)andBoulderCounty.GregoryCanyon CreekoriginatesinBoulderCountyOpenSpaceinBoulderMountainPark.Asflowbecomesmore concentratedawelldefinedchannelisvisibleupstreamofFlagstaffRoad.AtFlagstaffRoad,GregoryCanyon CreekisconveyedintotheCityofBouldervia60inchRCPthatislinedwithaϱϰ͟PVCliner.Fromhere, GregoryCanyonCreekislocatedentirelywithintheCityofBoulderandisboundedbyresidentialdevelopment untiltheconfluencewithBoulderCreek.TheprojectwatershedandstudyareaaredepictedinFigure2. GregoryCanyonCreekgenerallyflowstothenortheastdirectionthroughdevelopedneighborhoods.The creekisconveyedthroughmanycrossings,bothpublicallyandprivatelyconstructed.Veryfeweasementsare dedicatedtotheCityofBoulderthroughoutthechannelcorridor,withanumberofcrossingsbeingowned andmaintainedbyprivatepropertyowners.Inaddition,asGregoryCanyonCreekexistsonprivateproperty, homeownersareresponsibleforthechannelmaintenance.Thelowerportionsofthechannelarebounded bymoredenseresidentialhousing,includingmultifamilydevelopment.DownstreamofArapahoeRoad,the oulderCreek. channelhasrecentlybeenimprovedandappearstobestablepriortotheconfluencewithB Description of Data Obtained TheCityofBoulderprovidedCH2MHILLwithcurrentGISdata,topographyinformation,reports,andasbuilt plansforGregoryCanyonCreekandsurroundingareas.Thisinformationwasusedintheanalysispresented inthememorandum.ForacompletelistofdataprovidedpleaseseeTable1intheattachedtechnical appendix. Acknowledgements ThismemorandumwascompletedwiththesupportandinputfromvariousindividualsattheCityofBoulder andUrbanDrainageandFloodControlDistrict(UDFCD).Thekeyparticipantsinthedevelopmentofthis memorandumareshowninTable2. 20150415_ALTERNATIVEANALYSISMEMO_FINAL/ 1 ALTERNATIVE ANALYSIS MEMORANDUM TABLE2 ProjectContributors ProjectTeamMembersAffiliationRole KatieKnappCityofBoulderProjectManager AnnieNobleCityofBoulderStakeholder KristinDeanCityofBoulderStakeholder/UtilitiesPlanner ChristinShepardCityofBoulderStakeholder/GISAnalyst SheaThomasUDFCDStakeholder AlanTurnerCH2MHILLProjectManager MorganLynchCH2MHILLProjectEngineer FransLambrechtsenCH2MHILLStaffEngineer Hydrology AhydrologicanalysiswasnotperformedbyCH2MHILLaspartofthismasterplan.Theinformationusedin thismasterplanwasderivedfromtheprevioushydrologicanalysisperformedforGregoryCanyonCreek.To date,onereporthasbeenpublisheddocumentingthehydrologyofGregoryCanyonCreek.Thehydrologic studyisdescribedindetailinthefollowingsubsectionsandisreferencedinthecurrentBoulderCountyFlood InsuranceStudy(FIS)asthesourcefortheFEMAeffectivehydrology. Previous Studies InaccordancewithanagreementwithUrbanDrainageandFloodControlDistrict(UDFCD),theCityofBoulder, andBoulderCounty,Greenhorne&K͛DĂƌĂ͕Inc.,completedaMajorDrainagewayPlanningStudyʹBoulder andAdjacentCountyDrainagewaysfor11drainagewaysintheBoulderarea,includingGregoryCanyonCreek, datedMay1987.Asapartofthestudy,Greenhorne&K͛DĂƌĂcompletedfutureconditionshydrologyforthe 2,5,10,50,and100yearstormevents.TheColoradoUrbanHydrographProcedure(CUHP)wasusedto determinetherunoffhydrographsforeachstormevent.Thesehydrographswerethenroutedthroughthe USArmyCorpofEngineers(USACE)HydrologicEngineeringCenter(HEC)model,HEC1.Itwasdocumented inthereportthattherainfalldatareflectedthe1982guidelinesstatedintheUrbanStormDrainageCriteria Manual.ThestudywatershedforGregoryCanyonCreekwasapproximately2.29squaremileswitha100 hBoulderCreek.Thepeakdischargesfromthisstudy yearpeakdischargeof2,092cfsattheconfluencewit aredocumentedinthecurrentFEMAFIS,datedDecember18,2012,andhavebeenthebasisforeach subsequentstudycompletedfortheCityofBoulderforGregoryCanyonCreek. Summary of Peak Discharges HydrographsfromtheCUHPandHEC1analysis(Greenhorne&K͛DĂƌĂ͕1987)wereextractedfromoutput foruseinthetwoʹdimensionalhydraulicanalysisthatwasperformedaspartofthisstudy.TheFEMA effectiveflowsidentifiedinthe2010LetterofMapRevision(LOMR)(BeltCollinsWest,2010)wereusedfor theoneʹdimensionalHydrologicEngineeringCenterRiverAnalysisSystem(HECRAS)hydraulicmodeling. Hydraulics Forthismemorandum,itwasconcludedthatadetailedlookatthehydraulicfunctionofGregoryCanyon Creekwasneededtobetterunderstandthenaturalflowpaths.ThroughthisunderstandingtheCityof BoulderformulatesandCH2MHILLanalyzedimprovementelementsintocategoriestodecreasethefloodrisk topropertiesaspartofthedeliverableforthethisanalysis.Thesecategoriesaredescribedindetailin subsequentsections. 2 GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM ALTERNATIVE ANALYSIS MEMORANDUM Previous Studies InadditiontothehydrologicanalysisdocumentedintheMajorDrainagewayPlanningStudyʹBoulderand AdjacentCountyDrainageways,sixotherstudieshavebeendonealongGregoryCanyonCreek.Themost recenthydraulicanalysiswascompletedbyBeltCollinsWest(2007)toanalyzethe100yearfloodplain,the 0.5ftrisefloodway,andthehighhazardzonefortheCityofBoulder.Thestudywasbasedonthe1987 hydrologycompletedbyGreenhorne&K͛DĂƌĂaspartoftheMajorDrainagewayPlanningStudyʹBoulder andAdjacentCountyDrainageways.TheoriginalhydraulicstudywasperformedusingHEC2butwasnever adoptedbyFEMA.BeltCollinsWest(2007)usedHECRASversion3.1.3toupdatethefloodplainsalong GregoryCanyonCreek.Thisanalysisincorporatedupdatedtopography,dated2007.Debrisblockageat bridgesandculvertswereappliedtothehydraulicanalysisandamodelforthesplitflowreachthatwas identifiedatMarineStreetwasdevelopedtobetterdefinethefloodplaininthisarea.Thisstudywaslater updatedin2009todefinethestructuresinoradjacenttothehighhazardzonewithadditionalcrosssections and1ftgroundsurvey.Alternativestoremovesevenstructuresfromthehighhazardzoneweredocumented ThefloodplainandfloodwayidentifiedbyBeltCollinsGregoryCanyonCreekLOMR inthe2009report. DeterminationDataReconciliationinthe2010analysisreflectstheeffectiveconditionspublishedinthe BoulderCountyFIS,datedDecember18,2012.Theeffectivestudiesaswellastheotherstudiesperformed alongGregoryCanyonCreekaredocumentedinTable3. TABLE3 PreviousStudies DocumentTypeSourceDescription MajorDrainagewayPlanningStudyGreenhorneandK͛DĂƌĂ͕1984BoulderandAdjacentCountyDrainageways͞WŚĂƐĞ͟ MajorDrainagewayPlanningStudyGreenhorneandK͛DĂƌĂ͕1987BoulderandAdjacentCountyDrainageways͞WŚĂƐĞ͟ FloodHazardAreaDelineationGreenhorneandK͛DĂƌĂ͕1987BoulderandAdjacentCountyDrainageways HydraulicMitigationAnalysisBeltCollinsWest,2009GregoryCanyonCreekHighHazardZoneReanalysisʹMini MasterPlan 10GregoryCanyonCreekLOMRDeterminationData LOMRDeterminationBeltCollinsWest,20 Reconciliation(ApprovedbyFEMA,2010) HydraulicMitigationAnalysisWHPacific,2012GregoryCanyonCreekMitigationAnalysis AlternativeAnalysisCityofBoulder,2014PennsylvaniaAvenueFloodRepair/ImprovementAlternative Analysis Evaluation of Existing Facilities TheexistingconveyanceinfrastructurewithintheprojectareawasevaluatedusingtheHECRASversion4.1.0 andFLO2Dtodeterminethecapacityoftheinfrastructure.Inaddition,EPASWMMversion5.0wasusedto th evaluatethecapacityofthe7StreetculvertandtoanalyzethestormdrainsystemonWillowbrookRoad TheFEMAeffectiveHECRAShydraulicmodelwasusedasthebaselinehydraulicconditionforthisanalysis. ThismodelwasupdatedbasedoncrossinginformationthatwasgatheredonasitewalkperformedonJuly 17,2014.ThetopographyofGregoryCanyonCreekhadbeenalteredslightlybythestormeventinSeptember 2013,howeveritwasagreedthatthetopographyreflectedinthe2010LOMRwasthebestinformation available.CityofBoulderStaffcollectedmeasurementsforeachpubliccrossing.Themajorityofcrossing infrastructuregatheredinthefieldwasreflectedinthebaselinestudy,howeverseveralcrossingswere lectcurrentfieldconditions.AsummaryoftheexistingcrossingsarelocatedinTable4.The updatedtoref geometryforthecrossingswasupdatedintheHECRASmodeltoreflecttheconditionsidentifiedinthefield maintainingtheblockageassumptionthatwasappliedtothebaselinehydraulicmodel.Thiswasdoneby reducingtheareaofthecrossingbytheassumedpercentblockage.Thesechangestothecrossingshad negligibleimpactstothesplitflowreachandthemodelasawhole.AcomparisonbetweentheEffective ModelandtheupdatedExistingConditionsModelsislocatedinTable5inthetechnicalappendix.Noother GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM 3 ALTERNATIVE ANALYSIS MEMORANDUM changesweremadetothebaselinemodeltocreatetheexistingconditionsHECRASmodelforthepurpose ofthisanalysis. Table4 ExistingCrossingSummary LocationPercentBlockageBeltCollinsGeometry,UpdatedGeometry 2010 Assumption FlagstaffRd 50%ϳϯ͘Ϯ͟diameterϱϰ͟diameter PrivateDriveatOldBaseline100%Ϯϯ͟diameter Road PedestrianBridgeat0%NotModeled WillowbrookRoadCuldesac PrivateDriveatNWCornerof50%ϱϮ͘ϴ͟diameter WillowbrookRoadCuldesac (705WillowbrookRoad) PrivateDriveatWestSideof50%ϭϮϬ͟xϲϬ͟bridge WillowbrookRoad(777 WillowbrookRoad) WillowbrookRoad50%ϭϬϴ͟xϲϬ͟boxculvert PedestrianBridgeat0%NotModeled WillowbrookRoad PrivateDrive550Aurora0%ϭϵϮ͟xϴϰ͟boxculvert AuroraCrossing#10%ϯϲ͟diameter AuroraCrossing#20%ϲϬ͟xϭϮϬ͟boxculvert EuclidAvenue100%ϰϴ͟diameter CollegeAvenue50%62.4͞ǆϳϮ͟archculvertϳϮ͟xϳϴ͟archculvert PrivateDriveWoodBridgeDS75%OpenArea=77.4sq.ft. ofCollegeAvenue PennsylvaniaAvenue50%ϱϲ͘ϰ͟xϯϲ͟archculvert 7thStreet50%ϰϴ͟diameter WeirSplitFlowBoxDSof0%NotModeled AndersonDitch 704PleasantStreetPatio30%ϲϲ͟xϯϰ͘ϴ͟archculvert PleasantStreet20%ϵϲ͟xϰϴ͟archculvert UniversityAvenue50%ϳϮ͟xϲϬ͟archculvert 8thstreetandAlley50%ϲϲ͟xϯϴ͘ϰ͟archculvert rt 810MarineStreet50%ϰϴ͟xϯϲ͟boxculvertϳϱ͟xϱϰ͟boxculve MarineStreet50%ϵϲ͟xϰϴ͟boxculvertϭϬϰ͟xϰϴ͟boxculvert AlleyBetweenMarineand50%ϲϮ͘ϰ͟xϰϮ͟archculvert Arapahoe ArapahoeAvenue50%ϭϮϬ͟xϯϲ͟boxculvertϭϬϴ͟xϯϲ͟boxculvert PrivateDrivewayToOld50%ϰϮ͟diameter ϰϴ͟diameter School 4 GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM ALTERNATIVE ANALYSIS MEMORANDUM Detention Evaluation AnevaluationofdetentionalongGregoryCanyonCreekwasperformedtoidentifypossibleareaswhere detentionfacilitiescouldhelpimproveflowsbyattenuationorothermeans.Thefollowingareaswere reviewedforpotentialdetention: ImmediatelyupstreamofFlagstaffRoad; SmithPark; andFlatironsElementarySchool. DetentionUpstreamofFlagstaffRoad Onefootcontoursfromthe2013LiDARsetwereutilizedtodevelopanAreaStoragerelationshipforthis location.Figure7inthetechnicalappendixshowstheAreaStoragecurve.Theproposeddetentionpond wouldhold0.42acrefeet.Usingthiscurveanddetentionvolume,aSWMMmodelwasdevelopedusingthe existingculvertaspipeconduitattheinvert,andanoverflowweirelevationthatmatchedtheroadelevation. ThisminorattenuationinflowsistheresultofstoragevolumeupstreamofFlagstaffRoadbeingfilledonthe risinglimbofthehydrographpriortothepeakdischargearrivingatFlagstaffRoad,atwhichpointthepeak flowsovertoppedtheroad.Toachieveadditionalattenuation,earthworkwouldneedtobecompleted includingexcavationupstreamonOpenSpaceandMountainParkspropertywhichisnotdesired. Additionalconsiderationforthissiteincludestherequirementofageotechnicalanalysisandpotential reconstructionofFlagstaffRoadtoactasadam.Flagstaffroadisgreaterthan10feetaboveGregoryCanyon Creekthalwegwhichwouldcausethedetentionfacilitytobeclassifiedajurisdictionaldamandsubjecttothe regulationoftheColoradoStateEngineersOffice(SEO).ThiswouldrequirethecompletionofaHazard Reporttoclassifythehazardofthestructureandincreasedregulatoryapprovalandoversight Classification throughallphasesofthedamdesign,constructionandoperationwhichwouldsignificantlyincreasethecost ofthedesign,constructionandongoingoperationsandmaintenanceforafacilitythatwouldprovidelimited benefittoreducingpeakflowsdownstream DetentionatSmithPark TheslopeofSmithParkdropsapproximately30feetfromGilbertStreetonthewesttotheGregoryCanyon CreekChannel.ToaccommodateanofflinedetentionfacilityatSmithPark,a10footexcavationwouldbe requiredtoprovidestoragevolume.Thiswouldextendtoϭϴ͛deeponthewestsidesofthedetention facility.Thisareawouldprovideapproximately1.59acft.ofstorageandwouldfillduringa10yearstormin approximately3minutesprovidingverylittleattenuationtoflowratesinthedownstreamdirection.Figure 8inthetechnicalappendixshowstheAreaStoragecurve.Duetotherelativecostforconstructionand earthworkandtheminimalbenefitsthisfacilitywouldprovideitwasnotmovedforwardforfurther consideration. DetentionatFlatironsElementarySchool Theopenfieldsonthesouthwestcorneroftheschoolweresuggestedasapotentialsitefordetentionof flowsfromGregoryCanyonCreek.Thissitecouldpotentiallyprovideamaximumof2.89acftofstorageon theschoolopenspaceatadepthof6feetdeep.Figure9inthetechnicalappendixshowstheAreaStorage curve.Thispondwouldfillinapproximately6minutesduringa10yeareventandholdflowsforupto48 hoursafteranevent.Thiswouldagainprovideverylittleattenuationofthepeakflowsdownthemainstem ofGregoryCanyonCreekasthepondwouldfillduringtherisinglimbofthehydrograph.Inaddition,thissite eapproximately400feetofRCPpipestodeliverflowfromGregoryCanyonCreektothepond wouldrequir andupto450feetofpipetoreturntheflowtoGregoryCanyonCreek. Thissitecouldcontinuetobeusedforaplaygroundfortheschoolbutwouldfillandbefuupto48hours llfor inafloodingsituationandcouldposeaflashfloodhazardtotheschoolduetotheproximityofthepondto GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM 5 ALTERNATIVE ANALYSIS MEMORANDUM theschool.Duetothepotentialsafetyissues,costofexcavationandpipingandlimitedbenefitsfromthe pond,thispondalternativewasnotconsideredfurther. DuetotherelativeexpenseandlimitedimpactsoffulldetentiononthepeakflowsalongGregoryCanyon Creek,detentionwasdeterminedtobeaninfeasiblealternativeforthebasin.However,thesesitesandother smallopenareascanprovideopportunitiesforsedimentanddebristrapswhicharediscussedbelow. Sediment Traps Oneoftheissuesseenduringthe2013stormeventwassignificantamountsofsedimentanddebrisbeing transportedbyfloodwaters.TheCityrequestedthatananalysisbeperformedtodeterminethefeasibilityof sedimenttrapsbeinginstalledalongthechannelcorridor.Potentiallocationsforsedimenttrapsinclude: UpstreamoftheWillowbrookRd.culvert UpstreamofAuroraAvenueculvert th BetweenPennsylvaniaAve.and7St. th Theopenareaatthecornerof7StreetandPennsylvaniaAvenuewasanalyzedtodeterminethe effectivenessofasedimenttrap. AsedimentationstudypreparedbyMoser&Associates,inthenearbyFourmileCanyon,wasconductedin th 2008forUDFCDtitleSedimentAnalysisReportʹFourMileCanyonCreekDownstreamof30Street.This reportalongwithDƵůůĞƌ͛ƐreportEvaluationofFourmileCanyonCreekSedimentBasinAlternativescompleted in2012fortheCityofBoulderarethefoundationforthisanalysis.Accordingtothesereports,sedimentbasins areusefulfor2yearflowswhensedimentloadsarethegreatest.Whenconsideringasedimentbasin, stothefloodplainshouldalwaysbekeptinmindsoastoavoidincreasesintheregulatory potentialimpact floodplain. Moser&Associates,intheir2008report,statedthatsedimentloadsforFourmileCanyonwereonthe magnitudeof100tonspersquaremileperyear.WhilethestudywasdevelopeourmileCanyonCreek, dforF GregoryCanyonCreekislocatedinasimilargeographicregionandmayseesimilarloads.Underthis assumption,100tonspersquaremileperyearforGregoryCanyonCreekequaledasedimentloadof229tons peryear.Thisequatesto116cubicyards. Withapproximately10,000squarefeetavailablethreesedimenttrapalternativesareproposed.Oneinline basinof1,100squarefeet,andtwoofflinebasinsof1,700and2,500squarefeet.Theefficiencyofthebasin isafunctionofthe2yearpeakflowandthesurfaceareaofthebasin;largeflatbasinsaremoreefficient.The efficiencies,amountofsedimenttrapped,andestimatedcostsareshownforthe2yearpeakflowof161cfs inTable6.CostassumptionscamefromDƵůůĞƌ͛Ɛreportasanaveragecostpercubicyardofapproximately $898.00percubicyardtrapped.TheGregoryCanyonCreekMasterPlancontingencyusedforothercosts developedinthisstudywasappliedandincreasedthecostpercubicyardto$1,616.00.Notethatcostfor sedimentbasinsareafunctionoftheiroverallefficiency.Aconsiderationforimpactstopropertyshouldalso beconsidered.Ifspaceoreasementacquisitionislimited,aninlinebasinmaybemoreeffective.Figure10in thetechnicalappendixshowstheseproposedalternativesatthislocation. TABLE6 SedimentTrapAnalysis Willowbrook Alternate7thStAlt17thStAlt27thStAlt3EuclidAvenue Road 25001100170017001200 SurfaceArea 21221 n(1=inline,2=offline) Vs(settlementvelocity,0.0590.0590.0590.0590.059 finesand) 0.530.290.420.420.31 R(efficiency) 6 GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM ALTERNATIVE ANALYSIS MEMORANDUM TABLE6 SedimentTrapAnalysis Willowbrook Alternate7thStAlt17thStAlt27thStAlt3EuclidAvenue Road SedimentTrapped12166969670 (Ton) 9049717152 SedimentTrapped(CY) $80,677.01$43,762.94$63,765.36$63,765.36$46,526.23 EstimatedCost($) FLO-2D Evaluation DuringthestormeventthatoccurredinSeptember2013,manyresidentsalongtheGregoryCanyonCreek corridorwitnessedflowsalongstreetsadjacenttoGregoryCanyonCreek.Togetabetterunderstandingof theflowdistributionoutsidethelimitsofthechannelcorridor,CH2MHILLdevelopedatwodimensional hydraulicmodel,usingtheFLO2DV2009model,tobetterunderstandtheflowpathsoflargerstormevents. Agridwasbuiltusing2013LiDARdataprovidedbytheCityofBoulderfortheprojectarea.DĂŶŶŝŶŐ͛ƐN valueswereadjustedbasedonthesurroundinglanduseasrecommendedbythedocumentationintheFLO 2Dreference,seeTable7forallDĂŶŶŝŶŐ͛ƐNassumptionsfortheFLO2Dhydraulicmodel.Asummaryofthe HEC1peakdischargesandtheirapproximatelocationinthetwoʹdimensionalanalysisarelocatedinTable 8. TABLE7 DĂŶŶŝŶŐ͛ƐNDocumentation LanduseDescriptionDĂŶŶŝŶŐ͛ƐNValue Developed,MediumIntensity0.7 Developed,LowIntensity0.8 OpenSpace0.6 Grassland0.35 ForestedArea0.4 DevelopedOpenSpace0.25 Streets0.02 TABLE8 PeakDischargeSummary ReturnInterval(years),PeakDischarge(cfs) Location 2yr5yr10yr50yr100yr ApproximatelyϭϱϬ͛upstreamofFlagstaffRd321683289371270 1/3ofdischargeatAuroraAve,with2/3placedonthe 1682694859591179 localhighpoint OncetheFLO2Dgeometrywascreated,thehydrographsfromtheHEC1Model(Greenhorne&K͛DĂƌĂ͕ 1987)weredistributedattheappropriateflowchangelocationsforthe2,5,10,50,and100yearstorm eventsasdocumentedinTable8.Theresultsoftheexisting100yearstormeventareshowninFigure3in thetechnicalappendix.TheresultsoftheFLO2Danalysisconfirmedwhatwasobservedbyhomeowners GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM 7 ALTERNATIVE ANALYSIS MEMORANDUM duringtheSeptember2013stormevent.AcomparisontotheSeptember2013eventisalsoshowninFigure 4. Flood Hazards TheCityofBoulderandCH2MHILLstaffconductedasitewalkonJuly17,2014.Citystaffwasabletoconvey toCH2MHILLobservationsduringthefloodeventofSeptember2013andidentifypotentialareasfor improvements.Someofthepropertiesthathadbeendamagedbyfloodwatershadalreadybeenrestoredto prefloodconditionsorhadimprovementsconstructedsuchasfloodwallstohelppreventfutureflooding. Theobjectiveduringthesitewalkwastoidentifyalternativestohelpmitigateflooding.Thesealternatives arediscussedindetailinthesubsequentsections.Thepotentialimprovementsidentifiedduringthesitewalk arelocatedinTable9. TABLE9 PotentialImprovementSummary LocationProposedImprovementNumberofPropertiesImpacted UpstreamofWillowbrookRoadCuldeSacBankStabilizations3 PrivateCrossingon711WillowbrookRoadCulvertImprovements2 CrossingatWillowbrookRoadTrashRack/CulvertEntrance0 WillowbrookRoadatGregoryGulchReconfigureDrainageInlets3 CrossingatAuroraAvenueCulvert/ChannelImprovements3 Adjacentto6 th StreetChannelImprovements1 6 th StreetNorthofAuroraAvenueIncreaseRoadwayConveyanceVariesResidentialDrives EuclidAvenueCulvertImprovements2 7 th StreetPastRoseHillDriveIncreaseRoadwayConveyanceVariesʹResidentialDrives CrossingatCollegeAvenueMaximizeCulvertCapacity/Alignment4 th 11006StreetSidewalkRepair1 CrossingatPennsylvaniaAvenueCulvertRepair/RemovalVariesʹPotentialRerouteof Traffic th 7StreetatAndersonDitchMaximizeRoadwayConveyanceandMultiplewithStreet PipeIrrigationDitch construction/Locatedadjacent toschool BetweenPleasantStreetandUniversityBankStabilization2 Avenue UniversityAvenuetoMarineStreetIncreaseCulvertCapacity/ChannelMultiple Improvements AlleyBetweenArapahoeRoadandMarineIncreaseChannelCapacity/Replace5 StreetAgingCulvert NorthofArapahoeRoadUpsizeCulvert/ConstructBridge1 7 th StreetatArapahoeAvenueIncreaseRoadwayConveyanceVariesResidentialDrives Inadditiontotheproposedimprovementsidentifiedduringthesitewalk,documentedinTable9,CH2MHILL noticedotherdeficienciesalongGregoryCreekCanyonthroughdetailedhydraulicmodeling.Thechannel geometrybetweenEuclidAvenueandCollegeAvenueisoneoftheexistingsectionsthatisunabletoconvey the10ʹyearstormeventwithoutcausinginfrastructuredamage.Anothersectionisthechannelupstream 8 GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM ALTERNATIVE ANALYSIS MEMORANDUM ofEuclidAvenueforapproximately200feet.Inaddition,thecrossingatArapahoeRoadisunabletoconvey the10ʹyearstormeventthatisbeingconveyedfromtheupstreamchannelsection.Thesethreeareaswere alsoconsideredforpotentialimprovementsduringthealternativeanalysis. Alternative Analysis FloodhazardswithintheGregoryCanyonCreekwatershedareprimarilyduetoundersizedchannelgeometry andculvertcrossings.Thewatershedisconsideredtobefullydevelopedwiththechannelcorridorlocated almostentirelyonprivateproperty.Thenarrowchannelcorridor,lackofdrainageeasements,andnarrow rightofway,limitsthefloodcontrolelementsthatcanbeproposed.Knowingtheseconstraints,theCityof BoulderdirectedCH2MHILLtolookatcategoriesofimprovementsthatcouldmitigatefloodingriskswhile workingwithinthehorizontalconstraintsoftheexistingchannel.Inadditiontotheseconstraints,criteriathat wereconsideredwhiledevelopingtheproposedalternativesaredocumentedinTable10. TABLE10 DesignCriteria SourceDocument CityofBoulderDesignandConstructionStandardsʹStormWater Design,2005 CityofBoulderDesignandConstructionStandardsʹ TransportationDesign,2009 UrbanDrainageandFloodControlDistrictUrbanStormDrainageCriteriaManualʹVolume2, 2008 DuetothehorizontalandverticalconstraintsalongGregoryCanyonCreekproposedimprovementswilllikely requireeasementsandimpactadjacentpropertyowners.TheCityofBoulderstaffrequestedthatCH2MHILL evaluatetwodifferentcategoriesofelements CategoryOneʹChannelandCulvertImprovements; CategoryTwoʹ/ŵƉƌŽǀĞŵĞŶƚƐOutsideoftheChannel. TheintentoftheproposedcategoriesistomitigatefloodingriskwithCategoryOnebeingconfinedalongthe mainchannelcorridorandCategoryTwoincludingimprovementstoaccommodatespillflowsthatescapethe channel.ItisrecommendedthattheCityofBoulderworkwiththeresidentsandpropertyownersalong GregoryCanyonCreektoclearchannelbrushanddebrislocatedinthefloodwayandstabilizechannelbanks. Thefollowingdescribesthecategoriesofelementsthatwereevaluated.DesignCriteriaandassumptionsfor thedevelopmentandanalysisofthealternativesandcategoriescanbefoundinTABLE17inthetechnical appendix. CategoryOneʹChannelandCulvertImprovements.Thiscategorywasenvisionedtoprovide recommendationsforimprovementsalongthecreekcenterlinealongwithbrushanddebrisclearing.The existingculvertinfrastructurewasreviewedtorecommendreplacementsandimprovementstotheaging infrastructurealongGregoryCanyonCreektoensurethattheculvertcrossingscouldpassflowcontained withintheGregoryCanyonCreekchannelandidentifyrequiredmodificationstothechannel.Duetothe currentconditionoftheseculverts,itisassumedthatculvertreplacementalongGregoryCanyonCreekmay occurtoreplaceanydamagedoraginginfrastructure.Hydraulicallythechannelcapacityislimitedto approximatelythe10yearflowrate.Culvertsweresizedinthiscategorytopassthetenyearflowrate. Channelimprovementsintheimmediatevicinityofnewculvertswouldbeneededtoaccommodatethelarger culvertsize,andareincludedintheprojectscopeofeachindividualculvert.Inaddition,channeldeficiencies werenotedinareaswithseverelyreducedcapacitythatdidnotmeetthe10yearcriteriabythemajorityof thechannelorthesurroundinginfrastructure.Inaddition,ifalargerculvertscouldbeconstructedbasedon GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM 9 ALTERNATIVE ANALYSIS MEMORANDUM visualhorizontalandverticalconstraintstheselargerculvertsizeswereanalyzed.Thesemaximumculvert sizesandconstraintsareinTable11inthetechnicalappendix.TheimprovementsassociatedwithCategory OneareillustratedinFigure5inthetechnicalappendix. CategoryTwoʹ/ŵƉƌŽǀĞŵĞŶƚƐOutsideoftheChannel.Forthepurposesofthisanalysis,CategoryTwobuilds onthechanneloptimizationoftheGregoryCanyonCreekchannelpresentedinCategoryOneandseeksto maximizethefloodconveyanceofthemajoroverflowpathswhileadheringtothelocalcriteriaand constraints.CategoryTwoincludesproposedroadwaysectionstoproactivelyconveyfloodwaterthatexceed theGregoryCanyonCreekchannelinidentifiedroadways.DuringthestormeventinSeptember2013, thth floodwaterswereobservedinvariousroadwayswithprimaryconveyancepathsbeing6Street,7Street th and8Street.Theseflowpathswereidentifiedaspotentialoptionsforconveyinglargerstormeventsin placeswhereGregoryCreekisphysicallyconstrainedbyadjacentstructures.AFLO2Dmodelwasdeveloped tounderstandhowthestreetsconveyedflowduringlargerstormevents.Theseflowpathsareshownin ththth Figure3.Basedonthesemodels,6Street,7Street,8StreetandWillowbrookwereidentifiedasmajor watercoursesandwerethenformalizedandoptimizedasdrainageroutes.Itbecameclearthattheoverflows fromGregoryCanyonCreekintotheroadsystemduringthe100yeareventcouldexceed350cfsfortheroads ththth identifiedforconveyance.As6Street,7Streetand8StreetapproachBoulderCreek,thegradesofthe roadsflattenfromalmost6%gradeintheupperwatershedtocloserto1%inthelowerwatershed.Theflatter slopewasusedtounderstandthemaximumflowthatcouldbeachievedinthestreetsectionswithout ximumachievableflowis exceedingtheĐŝƚǇ͛Ɛ12ʹinchesmaximumfloodcriteria.NearBoulderCreekthema 193cfswhichisapproximately50%ofthemodeled100yearflowsinthestreet.Thisconveyancecapacityis achievedbyinstalling30footwideroads,6inchcurbandgutter,afourfootsidewalkwithanadditional6 inchcurbonthebackend.Thiscategory,whilenotsolvingthe100yearfloodingproblemcouldgoalongway tohelpalleviateflooddamage. ItisrecommendedthattheCityworkwithlocalemergencyagenciestoidentifysafetyandaccessissuesalong theseroutesduringfloodeventsandtoprovidesignagetoindicatethattheroadsaredesignedasflood conveyancefacilities.Theroadwayfloodconveyancewasassumedtohaveatypicalgutterdepthof6inches foreachresidentialstreet.FlowswerenotallowedtoexceedtheŝƚǇ͛Ɛ12inchmaximumrequirementof depthofflowinthestreet.TheimprovementsassociatedwithCategoryTwoarelocatedinFigure6inthe technicalappendix. AfterthePublicOpenHouseandWRABmeetingonOctober20,2014whichprovidedpublicinputonthe categories,thecitystafforganizedtheelementsinto15alternatives.ThesealternativesareidentifiedinTable 12below.Thealternativeswereusedtodevelopbenefit/costrelationshipstohelpunderstandthemostcost effectivealternativeinthebasintohelpimprovepublichealthandsafetyandminimizeflooddamages.Ofthe 15alternativesthefollowingalternativeswereanalyzedforthebenefitcostanalysisbecausetheyreflected theeffectsofalltheinfrastructureimprovementsontheGregoryCanyonCreekSystem. 10YearCulvertandChannelImprovements. Includes10YearculvertandchannelimprovementsfromCategory1 MaximumCulvertImprovementswithlocalizedchannelimprovements. IncludesmaximumculvertsandchannelimprovementsfromCategory110YearCulvertandChannel Improvementswithoverflowpathimprovements Includes10yearculvertandchannelimprovementsfromCategory1,withroadwayandoverflow pathimprovementsfromcategory2 MaximumCulvertImprovementswithlocalizedchannelimprovementsandroadwayconveyance IncludesmaximumculvertsandlocalizedchannelimprovementsfromCategory1,withroadway andoverflowpathimprovementsfromcategory2 10 GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM ALTERNATIVE ANALYSIS MEMORANDUM Theremainderofthealternativesidentifiedbycitystaffareintendedtoreflectphasingofthealternatives tofurtheranalyzethesystem. TABLE12 GregoryCanyonCreekAlternatives LowerReachMiddleReachUpperReach CulvertandCulvertandCulvertand ChannelChannelChannel StreetStreetStreet ImprovementsImprovementsImprovements Conv.Conv.Conv. 10yrMax10yrMax10yrMax Alternative1x Alternative2x Alternative3xx Alternative4xx Alternative5xx Alternative6xx Alternative7xxxx Alternative8xxxx Alternative9xxx Alternative10xxx Alternative11xxxxxx Alternative12xxxxxx Alternative13GregoryGulchPipe Alternative14PipingAndersonDitch AllofthedefinedalternativeswerebuiltintotheeffectiveHECRASmodelstodeterminethedepthofflow throughoutthesystemwhichwasusedtodeterminebenefits.Allfiguresandtablesinthetechnicalappendix havebeenupdatedtocapturetherevisedalternatives.Table13isasummaryofthealternativesandtheir respectivecosts.LineitemsforGregoryGulchPipeatWillowbrookRoadandthepipingofAndersonDitchare includedseparately. GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM 11 ALTERNATIVE ANALYSIS MEMORANDUM TABLE13 SummaryofAlternativeCosts AlternativeCostNotes Includes:10yearculvertimprovements,adjacentchannel $4,692,167.00 10yearimprovementsforculverts,andchannelimprovementsin otherareastoincreaseto10yearcapacity. Includes:10yearculvertimprovements,adjacentchannel improvementsforculverts,channelimprovementsin 10yearWithOverflow$8,505,643.00 otherareastoincreaseto10yearcapacity,andstreet Conveyance conveyanceincriticalareas.AlsoincludestheGregory Gulchpipe. Includes:Maximumculvertimprovements,adjacent $7,876,974.00channelimprovementsforculverts,andchannel Maximum improvementsinotherareastoincreaseto10year capacity. Includes:Maxculvertimprovements,adjacentchannel improvementsforculverts,channelimprovementsin MaxWithOverflow$11,690,450.00 otherareastoincreaseto10yearcapacity,andstreet Conveyance conveyanceincriticalareas.AlsoincludestheGregory Gulchpipe. AndersonDitchPipe$23,450.00Includes:PipingofAndersonDitch. Benefit Cost Analysis Abenefitcostanalysiswasperformedtoanalyzethealternativesasoutlinedabove.Thefollowingfour primaryalternativeswereanalyzed: 10yearculvertimprovements 10yearculvertimprovementswithstreetconveyanceimprovements Maximumculvertimprovements Maximumculvertimprovementswithstreetconveyanceimprovements Data Collection TheprimaryresourceforallocatingdatatodevelopthebenefitcostanalysiswastheFederalEmergency ManagementAgency(FEMA)HAZUSʹMHcomputerprogramandtheFEMABCAtool.AHAZUSMHdatabase producedbyFEMAthatcategorizedthestructures,foundationtypes,firstfloorelevationidentification number,structurevalueandcontentsvaluecreatedinresponsetothe2013flood,providedthebase informationtodeterminebenefitsforeachofthealternatives.Thisdataincludedinformationonthefirst floorelevationvalue,foundation,type,structuretype,andthenumberofstories.Additionaldataincluded assessordatafromBoulderCountywhichincludedadescriptorofthebasementtypetohelpidentifyhowto modifythelowestadjacentgradetocomputefirstfloorelevation. Methodology Inordertodeterminethebenefitcoststotheproposedalternatives,ananalysiswasperformedusingwater surfaceelevationsbasedontheHECRASmodelsdevelopedforeachalternative.Lowestadjacentgradesfor 12 GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM ALTERNATIVE ANALYSIS MEMORANDUM thehomeswereinterpolatedfromasurfacebasedon1ftcontoursusingArcGIS,andfirstfloorelevations wereassignedbasedonthecountyassessorinformationwithspecificattentiongiventobasementtype.The lowestadjacentgradesweremodifiedbasedonbasementtypeusingthevaluesinTable18intheAppendix. Ifabasementtypewas͞ƵŶĨŝŶŝƐŚĞĚ͟thenthestructurewasassumedtoactasaslabongradestructure.This elevationwascomparedagainstthewatersurfaceelevationsforthe10,50,100,and500yrrecurrence intervalstormstodevelopthedepthoffloodingrelativetothefirstfloorelevationofallimpactedstructures. Thisanalysisresultedinalistofstructureswithinthefloodplainforeachstormevent,andeachalternative. DepthdamagefunctionswerepulledfromtheBCATool5.1programdevelopedbyFEMA.Thesefunctions provideadamagepercentageofboththestructurevalueandcontentsvalueofastructurebasedonthedepth offloodingexperiencedatthestructure.BothstructureandcontentsvalueswereincludedintheBCAanalysis. ThestructureinformationacquiredfromFEMAincludeddifferingcategoriesofstructures.Theseincluded Structuretype Residential Commercial Industrial Governmental Education Numberofstories FoundationType Basement Crawlspace Slabongrade BasementType Walkout(finished/unfinished) Subterranean(finished/unfinished) Garden(finished/unfinished) Thesestructurecategoriesformedauniqueidentifierthatcorrespondedtoaspecificdepthʹdamagefunction fromtheBCAToolmodel.AseparatedepthdamagefunctionwascreatedseparatelyforGardenand Subterraneanbasementstomodifywhendamagebegantooccur.Alookuptablewassetuptomatch structure,withtheassignedwaterdepth,todeterminethepercentageofdamageforeachreturnperiodand aredtoexistingconditionsdamagestodeterminethe alternative.Damagesforeachalternativewerecomp benefitsofeachalternative. Averageannualdamagesweredeterminedforeachalternativebymultiplyingthedamagesbytheprobability ofrecurrence.Inaddition,allcostsforthealternativeswereconvertedaverageannualcosts.Thiswasdone bytakinga7%amortizationrateandassumingafiftyyearprojectlifespanpertheguidancefromtheFEMA BCAguidance. Table14presentsasummaryofthedamagescalculatedforexistingconditionsandthealternatives.Table15 presentsasummaryofthebenefitcostratios.Table16,inthetechnicalappendix,providesamoredetailed viewofthedamagesperalternative. GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM 13 ALTERNATIVE ANALYSIS MEMORANDUM TABLE14 SummaryofDamages(StructureandContents)forExistingConditionsandAlternatives DamagefromStormEvent Storm Probability Event Existing10yr10yrw/StreetMaxMaxw/Street 0.25yr$0.00$0.00$0.00$0.00$0.00 0.110yr$39,885,504$28,624,736$28,624,736$26,807,549$26,532,135 0.0250yr$44,871,121$36,296,256$35,953,292$35,388,630$34,657,034 0.01100yr$45,713,907$37,709,166$36,703,945$36,511,272$35,407,533 0.002500yr$50,081,200$41,610,872$41,289,544$41,132,626$39,726,175 TABLE15 SummaryofAnnualizedDamageCosts,Benefits,AlternativeCosts,andBenefitCostRatios ConditionsExisting10yr10yrw/StreetMaxMaxw/Street Annualizeddamage$4,430,766.00$3,521,538.00$3,492,949.00$3,415,439.00$3,345,260.00 Benefit$909,228.00$937,817.00$1,015,327.00$1,085,506.00 AnnualizedAlternativeCost(7% $339,994.00$616,318.00$570,764.00$847,088.00 Amortization,50yrLifeSpan) BenefitCostRatio2.671.521.781.28 Engineers Recommended Plan Introduction TheŶŐŝŶĞĞƌ͛ƐRecommendedPlantominimizetheidentifiedfloodingissuesalongGregoryCanyonCreekis the10yearalternative(RecommendedPlan).ThisRecommendedPlanisofferedforconsiderationbasedon feedbackfrompublicmeetings,projectstakeholders,staffinputandpreliminarydiscussionswithWRAB. TheŶŐŝŶĞĞƌ͛ƐRecommendedPlanisonlythefirststepintheadoptionprocess.Severaladditional endorsementorapprovalsmustbesecuredbeforeanyimplementationisinitiated.Ateachstep,adjustments totheRecommendedPlanmaybeidentifiedthataddressspecificconcernsexpressedbythereviewingentity ortheRecommendedPlancanbedismissedinfavorofanotheralternative.Attheendoftheprocess,thecity maychoosetoadoptasingleplanthatconsolidatestherefinementsorselectsanentirelydifferentoption, eitherstudiedaspartofthisMitigationPlanningStudyordevelopedbasedonothercriteria. TheŶŐŝŶĞĞƌ͛ƐRecommendedPlanhasbeenpresentedtocitystaff.Commentsbythegrouphavebeen addressedandrefinementsincorporatedintotheRecommendedPlanasnecessary.TheRecommendedPlan, oncereviewedandapprovedbycitystaff,isnowreadytobepresentedtoWRAB.Itisalsoexpectedthata 14 GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM ALTERNATIVE ANALYSIS MEMORANDUM presentationwillbemadetothepublicandotherstakeholdersthatdescribestheplanningprocessandthe elementsoftheRecommendedPlan.Inadditiontothesepresentations,theteamintendstopresentthe RecommendedPlantoCityCouncilforformalconsiderationandadoption.Oncetheplanhasbeenadopted, CityPublicWorksUtilitiesstaffwillincorporatetherecommendationsintoalongtermCapitalImprovements Program. Plan Description TheRecommendedPlanfocusesonalleviatingfloodingalongGregoryCanyonCreek,withoutaffecting adjacentstructures,minimizingRightʹofʹwaytakeswhileprovidingthegreatestlevelofservice throughoutthecorridorinthemostcosteffectivewaypossible.Thisalternativefocusesonmakingchannel improvementstoconveythe10yearstormeventandreplacingculvertsalongthechanneltoalsoconvey the10yearstormevent.Theseimprovementswillprovideadditionalprotectionfrommorefrequent floodingeventsbutwillnoteliminatethe100yearfloodhazard.Additionaloptionscouldbeincludedatthe ŝƚǇ͛Ɛdiscretionincludingsedimentanddebristraps,improvementstoirrigationfacilitiesorimprovements toroadsthatcouldhelpcontainandconveyhigherfloweventsalongtheroadswithinthebasins. OtherFeaturesoftheRecommendedPlan TheRecommendedPlanalsorecognizestheŝƚǇ͛Ɛconsiderableeffortstomanageandcontrolfloodhazards. TheCityhasanextensivebodyoffloodplainandfloodwayprotectionsbuiltintothezoning,landuseand developmentregulations.Physicalinfrastructuretowarncitizensofanimpendingfloodthreatexists throughsirensandotherwarningmechanismsandanimpressivebodyofmasterplanningexistsformanyof theĐŝƚǇ͛Ɛdrainageways. Inaddition,theCityalsohasregulationsthatareinplacetoprotecttheenvironmentalvaluesthe communityfindssovaluable.Stormwaterqualityregulationshavebeenadoptedtoassurethatfuture constructionactivitiesdonotcreateadverseenvironmentalimpacts.Existingstormwaterdischargepermits issuedunderthe^ƚĂƚĞ͛ƐStormwaterNPDESprogramalsoincludeprogramsthatpromotepubliceducation andcontrolothersourcesofpollution.Theseareintendedtoremaininplaceandareimplicitlyincorporated intotheRecommendedPlan. Basis for Selection Theprimaryobjectivedefinedattheoutsetofthestudywastoreducethefloodimpactsonproperties alongGregoryCanyonCreekwithaslittledisturbancetoprivatepropertiesaspossible.TheRecommended Plandoesreducethefloodhazardthroughoutthewatershedfor40structuresforthe10yrconditionand 18structuresforthe100yrcondition.Thisreducedhazardprovidesmuchbetteraccessforemergency vehiclesduringfloodevents. TheRecommendedPlanhasthehighestbenefitcostratioamongtheplansevaluated.Thismeansthatthe ŝƚǇ͛Ɛinvestmentininfrastructuretoaddressfloodinggeneratesafavorablereturnbyreducingtheaverage annualflooddamagesbyafactorof2.67overtheinvestmentcost. TheRecommendedPlandoescreatesomeunavoidableimpactstoprivateproperties.However,the elementsoftheRecommendedPlanhavebeenlaidouttominimizetheseimpacts. GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM 15 List of Figure and Tables Figures....................................................................................................................................................17 Figure1:September2013FloodExtents...........................................................................................................18 Figure2:AreaofInterest...................................................................................................................................19 Figure3:Existing100ʹyear2DAnalysisFloodplain.......................................................................................20 Figure4:ComparisontoSeptember2013Event...............................................................................................21 Figure5:CategoryOneʹChannelandCulvertImprovements....................................................................2224 Figure6:CategoryTwoʹImprovementsOutsideoftheChannel................................................................2527 Figure7:FlagstaffRoadDetentionStageStorageCurve..................................................................................28 Figure8:SmithParkStageStorageCurve.........................................................................................................29 Figure9:FlatironsElementarySchoolStageStorageCurve..............................................................................30 th Figure10:7StreetSedimentTrapAlternatives...............................................................................................31 Figure11:FlowmasterOutputʹTieredCurb....................................................................................................32 Tables....................................................................................................................................................33 Table1:DataReceivedFromCityofBoulder....................................................................................................34 Table5:EffectiveandExistingHydraulicOutput..............................................................................................36 Table11:CulvertImprovements.......................................................................................................................42 Table16:DamageAssessment.........................................................................................................................44 Table17:DesignCriteriaandAssumptions.......................................................................................................45 Table18:LowestAdjacentGradeBasementTypeModifierValues..................................................................46 AcronymsandAbbreviations...................................................................................................................47 Technical Appendix Figures JAY JAY (ft)Stage (ft)Stage (ft)Stage Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community, Esri, HERE, DeLorme, MapmyIndia, © OpenStreetMap contributors LEGEND Creek Centerline 1' Contours (2013) CountyParcels Sediment Trap AlternativesGregory Canyon Creek Drainage Area = 2.29 sq. miles 2-year Q = 161 cfs Alt 1 - Offline Sediment Load = 229 Tons (116 CY) Alt 2 - Inline Alt 3 - Offline Alt 1 Area - 2500 sq. ft, 2' deep, 53% Efficiency (Fine Sand) Alt 2 Area - 1150 sq. ft, 3' deep, 29% Efficiency (Fine Sand) $ Alt 3 Area - 1700 sq. ft, 2' deep, 42% Efficiency (Fine Sand) Sediment Trap Analysis (DRAFT) 02550100 Gregory Canyon Creek MDP Feet UNK G:\498924_GREGORY_CREEK\03_GIS\MAPFILES\2015.02.12 UPDATED FIGURES\FIG10_ SEDIMENT TRAP ALTERNATIVES.MXD FLAMBREC 2/12/2015 6:52:46 PM Cross Section for Tiered Curb - Irregular Section - 1 Project Description Friction MethodManning Formula Solve ForDischarge Input Data 0.01000 Channel Slopeft/ft 1.00 Normal Depthft 193.06 Dischargeft³/s Cross Section Image Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries1) [08.11.01.03] 2/12/2015 2:40:31 PM27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666Page1of1 Technical Appendix Tables HEC-RAS Plan: Multi-profil River: RIVER-1 Reach: Reach-1 Profile: 100-year ReachRiver StaProfileQ TotalMin Ch ElW.S. ElevCrit W.S.E.G. ElevE.G. SlopeVel ChnlFlow AreaTop WidthFroude # Chl (cfs)(ft)(ft)(ft)(ft)(ft/ft)(ft/s)(sq ft)(ft) Reach-1600 100-year1450.005750.205756.855756.855758.450.03888010.98175.5060.170.82 Reach-1590 100-year1450.005718.235735.875730.315735.920.0008762.53973.97161.140.11 Reach-1585 Culvert Reach-1580 100-year1450.005717.805729.905729.905735.890.04025119.6473.8288.341.00 Reach-1560 100-year1450.005684.475694.475693.185694.750.0112425.70419.85133.660.36 Reach-1555 Culvert Reach-1550 100-year1450.005683.105690.535690.535693.070.00964814.73168.7148.501.02 Reach-1540 100-year1450.005660.985668.235668.235669.920.02460311.70156.4146.951.04 Reach-1530 100-year1450.005652.105660.015660.015661.830.01862510.93141.5546.240.94 Reach-1520 100-year1450.005645.525658.505657.665658.860.0030286.00528.70144.840.31 Reach-1515 Culvert Reach-1510 100-year1450.005643.575654.015654.015654.540.0034676.31339.6880.770.36 Reach-1508 100-year1450.005640.035646.625646.625648.300.03764910.49146.3049.620.98 Reach-1507 100-year1450.005639.215645.295645.295646.870.03323010.35158.9854.520.95 Reach-1505 100-year1450.005638.275644.005644.005645.410.03248010.18185.6375.130.94 Reach-1500 100-year1450.005625.605635.375634.975636.390.0224169.78276.81125.140.55 Reach-1495 Bridge Reach-1490 100-year1450.005624.405634.005634.005635.060.0264369.96264.01125.710.57 Reach-1470 100-year1450.005607.685621.075614.065621.420.0038235.22439.53128.910.26 Reach-1465 Culvert Reach-1460 100-year1450.005603.335612.655612.655617.290.02084217.2883.9296.841.00 Reach-1455 100-year1700.005596.395604.215604.215606.380.02829911.84148.3339.920.98 Reach-1450 100-year1700.005590.815599.195599.195600.780.02679210.27182.25106.220.93 Reach-1440 100-year1700.005587.695593.975593.975595.250.0238369.76254.43136.040.89 Reach-1436 100-year1700.005578.635584.235584.235585.080.0165629.62410.40224.640.78 Reach-1431 100-year1700.005571.705581.245578.805581.770.0060216.76494.40217.070.40 Reach-1425 Culvert Reach-1420 100-year1700.005571.105578.205578.205581.680.02249814.97113.58124.360.99 Reach-1410 100-year1700.005565.615573.365570.925573.990.0075206.39266.9859.280.50 Reach-1405 Culvert Reach-1400 100-year1700.005563.355568.135566.975569.130.0120788.04211.3659.640.67 Reach-1398 100-year1700.005563.395566.675566.675568.180.05592012.44216.2689.811.33 Reach-1395 100-year1700.005555.005560.985560.985562.730.03726610.61161.0848.301.01 Reach-1390 100-year1700.005551.405556.735556.735557.870.03582010.19257.62108.500.98 Reach-1389 100-year1700.005550.005554.695554.695555.840.04047210.35249.04105.651.04 Reach-1385 100-year1700.005537.755541.855541.855542.850.08241711.83240.83115.581.35 Reach-1380 100-year1700.005529.505537.315536.865537.730.0119166.26389.63203.440.56 Reach-1375 Culvert Reach-1370 100-year1700.005527.685534.135534.135534.570.0068555.88465.53213.820.46 Reach-1360 100-year1700.005511.805518.905518.905520.810.03472211.20162.1349.180.95 Reach-1352 100-year1700.005507.305515.915514.425516.760.0097008.62308.02138.430.56 Reach-1351 100-year1700.005506.805513.845513.845516.230.03824912.41140.0163.470.97 Reach-1350 100-year1700.005503.405510.385510.385512.430.03690811.49147.9936.511.01 Reach-1342 100-year1700.005494.955501.695501.695503.950.03986013.71182.4053.931.08 Reach-1340 100-year1700.005493.145500.025500.025500.920.0211128.73341.61219.500.75 Reach-1334 100-year1700.005488.115496.035497.340.0179289.62232.1685.620.72 Reach-1330 100-year1700.005485.845495.235495.075496.170.0184338.72331.63179.630.66 Reach-1325 Culvert Reach-1318 100-year1900.005485.275493.735493.735494.510.02443610.31420.16211.850.70 Reach-1304 100-year1900.005484.405491.105489.245491.690.0078396.33357.61178.900.48 Reach-1303 Bridge Reach-1302 100-year1900.005483.055487.955487.955489.290.03203310.47254.2790.820.93 Reach-1301 100-year1900.005479.085484.815484.815486.170.0226819.81258.28121.680.82 Reach-1300 100-year1900.005475.105479.935479.935480.860.0310598.66318.58168.210.90 Reach-1295 100-year1900.005470.265474.885474.885475.760.0392668.31314.26211.210.98 Reach-1291 100-year1900.005468.095472.495472.495473.340.0266109.41396.31222.860.87 Reach-1290 100-year1900.005464.325470.485470.485471.360.0189039.14411.06248.010.75 Reach-1285 Culvert Reach-1280 100-year1900.005461.705467.895467.895468.210.0094716.37578.03218.680.53 Reach-1270 100-year1900.005451.445458.045458.045459.110.0122609.60381.62187.380.72 Reach-1265 Culvert Reach-1260 100-year1900.005438.865447.505444.675448.110.0040716.42361.09113.910.43 Reach-1255 Culvert Reach-1250 100-year1900.005438.245446.485445.295447.110.0068306.86400.50154.290.53 Reach-1231 100-year1900.005434.975444.405444.405445.820.03296112.40287.9799.550.73 Reach-1230 100-year1900.005434.905443.565443.565444.920.02617211.89302.1299.930.74 Reach-1225 Culvert Reach-1220 100-year1900.005433.655440.675440.675441.570.02906410.50376.40177.340.80 Reach-1219 100-year1900.005431.605437.715437.715438.590.0415529.33318.30162.350.99 Reach-1200 100-year1900.005420.595427.245427.245428.760.0395809.91192.7566.661.01 Reach-1190 100-year1900.005414.105423.335420.315423.540.0047393.67596.46310.940.36 Reach-1185 Culvert Reach-1180 100-year2092.005410.575420.015420.015420.110.0032143.181217.59674.140.30 Reach-1175 100-year2092.005408.705415.835415.835416.400.0306517.26483.53374.880.85 Reach-1170 100-year2092.005404.975411.475409.065411.710.0036194.38828.55481.650.34 Reach-1165 Culvert Reach-1160 100-year2092.005398.605404.815405.040.0036374.21732.13281.540.34 Reach-1152 100-year2092.005396.425403.725403.725404.480.0274758.45435.92262.550.84 Reach-1151 Culvert HEC-RAS Plan: Multi-profil River: RIVER-1 Reach: Reach-1 Profile: 100-year (Continued) ReachRiver StaProfileQ TotalMin Ch ElW.S. ElevCrit W.S.E.G. ElevE.G. SlopeVel ChnlFlow AreaTop WidthFroude # Chl (cfs)(ft)(ft)(ft)(ft)(ft/ft)(ft/s)(sq ft)(ft) Reach-1150 100-year2092.005393.635401.775401.775402.530.02950910.54468.31242.770.67 Reach-1130 100-year2092.005393.485401.195401.195401.770.0157328.97667.32476.010.60 Reach-1125 Culvert Reach-1120 100-year2092.005389.005398.535398.535399.540.0256968.70358.11229.030.80 Reach-1119.9 Lat Struct Reach-1110 100-year2092.005387.395394.365394.365395.460.02704210.34365.31167.320.88 Reach-1100 100-year2078.555383.005390.525390.525391.420.02058610.43454.21234.730.73 Reach-195 Culvert Reach-190 100-year2078.555383.145388.975388.975389.950.02593310.61392.68183.540.86 Reach-189.9 Lat Struct Reach-160 100-year1020.475374.505381.275379.675381.810.0081896.30241.21135.420.48 Reach-155 Culvert Reach-150 100-year1020.475372.705378.875378.875379.490.0133447.46235.7497.870.56 Reach-149.9 Lat Struct Reach-145 100-year883.315369.495375.465375.465376.580.0259558.72124.7275.980.82 Reach-140 100-year866.485363.575372.925370.775373.140.0049364.09303.93153.240.36 Reach-135 Culvert Reach-130 100-year866.485362.315370.775370.775370.930.0022043.22308.31130.740.26 Reach-110 100-year866.485356.305361.425360.205362.110.0110736.77141.3544.000.58 HEC-RAS Plan: MP Exist 072014 River: RIVER-1 Reach: Reach-1 Profile: 100-year ReachRiver StaProfileQ TotalMin Ch ElW.S. ElevCrit W.S.E.G. ElevE.G. SlopeVel ChnlFlow AreaTop WidthFroude # Chl (cfs)(ft)(ft)(ft)(ft)(ft/ft)(ft/s)(sq ft)(ft) Reach-1600 100-year1450.005750.205756.855756.855758.450.03888010.98175.5060.170.82 Reach-1590 100-year1450.005718.235735.895730.315735.940.0008682.52977.51161.260.11 Reach-1585 Culvert Reach-1580 100-year1450.005717.805729.905729.905735.890.04025119.6473.8288.341.00 Reach-1560 100-year1450.005684.475694.475693.185694.750.0112425.70419.85133.660.36 Reach-1555 Culvert Reach-1550 100-year1450.005683.105690.545690.545693.070.00961514.71169.0048.601.01 Reach-1540 100-year1450.005660.985668.235668.235669.920.02460311.70156.4146.951.04 Reach-1530 100-year1450.005652.105660.015660.015661.830.01861010.92141.6046.250.94 Reach-1520 100-year1450.005645.525658.565657.675658.900.0029275.91537.13145.290.31 Reach-1515 Culvert Reach-1510 100-year1450.005643.575654.015654.015654.540.0034706.31339.4880.690.36 Reach-1508 100-year1450.005640.035646.635646.635648.300.03752510.48146.4649.640.98 Reach-1507 100-year1450.005639.215645.295645.295646.870.03329310.36158.8754.520.95 Reach-1505 100-year1450.005638.275644.005644.005645.410.03248010.18185.6375.130.94 Reach-1500 100-year1450.005625.605635.375634.975636.390.0224269.78276.75125.140.55 Reach-1495 Bridge Reach-1490 100-year1450.005624.405634.005634.005635.060.0264369.96264.01125.710.57 Reach-1470 100-year1450.005607.685621.135614.065621.460.0037195.16446.33129.140.25 Reach-1465 Culvert Reach-1460 100-year1450.005603.335612.655612.655617.290.02084217.2883.9296.841.00 Reach-1455 100-year1700.005596.395604.215604.215606.380.02833011.85148.2739.910.98 Reach-1450 100-year1700.005590.815599.195599.195600.780.02679210.27182.25106.220.93 Reach-1440 100-year1700.005587.695593.985593.985595.250.0237979.75254.63136.180.89 Reach-1436 100-year1700.005578.635584.235584.235585.080.0165629.62410.40224.640.78 Reach-1431 100-year1700.005571.705581.245578.805581.770.0060216.76494.40217.070.40 Reach-1425 Culvert Reach-1420 100-year1700.005571.105578.205578.205581.680.02249814.97113.58124.360.99 Reach-1410 100-year1700.005565.615573.365570.925573.990.0075206.39266.9859.290.50 Reach-1405 Culvert Reach-1400 100-year1700.005563.355568.135566.975569.130.0120788.04211.3659.640.67 Reach-1398 100-year1700.005563.395566.675566.675568.180.05592012.44216.2689.811.33 Reach-1395 100-year1700.005555.005560.985560.985562.730.03726610.61161.0848.301.01 Reach-1390 100-year1700.005551.405556.745556.745557.870.03576110.19257.78108.530.98 Reach-1389 100-year1700.005550.005554.695554.695555.840.04047210.35249.04105.651.04 Reach-1385 100-year1700.005537.755541.855541.855542.850.08235711.82240.89115.591.34 Reach-1380 100-year1700.005529.505537.375536.865537.760.0109566.07401.46203.840.54 Reach-1375 Culvert Reach-1370 100-year1700.005527.685534.135534.135534.570.0068725.88465.00213.790.46 Reach-1360 100-year1700.005511.805518.905518.905520.810.03473411.20162.1149.180.95 Reach-1352 100-year1700.005507.305515.915514.425516.760.0097008.62308.02138.430.56 Reach-1351 100-year1700.005506.805513.845513.845516.230.03824912.41140.0163.470.97 Reach-1350 100-year1700.005503.405510.385510.385512.430.03690811.49147.9936.511.01 Reach-1342 100-year1700.005494.955501.695501.695503.950.03986013.71182.4053.931.08 Reach-1340 100-year1700.005493.145500.025500.025500.920.0212168.74340.76219.420.75 Reach-1334 100-year1700.005488.115496.055495.565497.350.0176889.58233.7186.020.72 Reach-1330 100-year1700.005485.845495.165495.075496.170.0198438.97319.14178.290.68 Reach-1325 Culvert Reach-1318 100-year1900.005485.275493.735493.735494.510.02452310.32419.54211.790.70 Reach-1304 100-year1900.005484.405491.105489.245491.690.0078396.33357.61178.900.48 Reach-1303 Bridge Reach-1302 100-year1900.005483.055487.955487.955489.290.03203310.47254.2790.820.93 Reach-1301 100-year1900.005479.085484.815484.815486.170.0226819.81258.28121.680.82 Reach-1300 100-year1900.005475.105479.935479.935480.860.0310598.66318.58168.210.90 Reach-1295 100-year1900.005470.265474.885474.885475.760.0392668.31314.26211.210.98 Reach-1291 100-year1900.005468.095472.495472.495473.340.0265369.40396.74222.910.87 Reach-1290 100-year1900.005464.325470.485470.485471.360.0189039.14411.06248.010.75 Reach-1285 Culvert Reach-1280 100-year1900.005461.705467.895467.895468.210.0094946.37577.50218.600.53 Reach-1270 100-year1900.005451.445458.045458.045459.110.0122609.60381.62187.380.72 Reach-1265 Culvert Reach-1260 100-year1900.005438.865447.505444.675448.110.0040706.42361.15113.910.43 Reach-1255 Culvert Reach-1250 100-year1900.005438.245446.485445.295447.110.0068306.86400.50154.290.53 Reach-1231 100-year1900.005434.975444.405444.405445.820.03296112.40287.9799.550.73 Reach-1230 100-year1900.005434.905443.565443.565444.920.02617211.89302.1299.930.74 Reach-1225 Culvert Reach-1220 100-year1900.005433.655440.675440.675441.570.02903010.49376.58177.360.80 Reach-1219 100-year1900.005431.605437.715437.715438.590.0415529.33318.30162.350.99 Reach-1200 100-year1900.005420.595427.245427.245428.760.0394999.90192.9166.701.01 Reach-1190 100-year1900.005414.105423.335420.315423.530.0047663.67594.82307.970.36 Reach-1185 Culvert Reach-1180 100-year2092.005410.575420.015420.015420.110.0032253.191215.94673.860.30 Reach-1175 100-year2092.005408.705415.835415.835416.400.0306517.26483.53374.880.85 Reach-1170 100-year2092.005404.975411.475409.065411.710.0036194.38828.55481.650.34 Reach-1165 Culvert Reach-1160 100-year2092.005398.605404.815405.040.0036374.21732.13281.540.34 Reach-1152 100-year2092.005396.425403.725403.725404.480.0274758.45435.92262.550.84 Reach-1151 Culvert HEC-RAS Plan: MP Exist 072014 River: RIVER-1 Reach: Reach-1 Profile: 100-year (Continued) ReachRiver StaProfileQ TotalMin Ch ElW.S. ElevCrit W.S.E.G. ElevE.G. SlopeVel ChnlFlow AreaTop WidthFroude # Chl (cfs)(ft)(ft)(ft)(ft)(ft/ft)(ft/s)(sq ft)(ft) Reach-1150 100-year2092.005393.635401.775401.775402.530.02950910.54468.31242.770.67 Reach-1130 100-year2092.005393.485401.265401.265401.820.0150668.84701.86486.330.59 Reach-1125 Culvert Reach-1120 100-year2092.005389.005398.535398.535399.540.0256968.70358.11229.030.80 Reach-1119.9 Lat Struct Reach-1110 100-year2092.005387.395394.365394.365395.460.02702810.34365.40167.330.88 Reach-1100 100-year2078.555383.005390.525390.525391.420.02058610.43454.21234.730.73 Reach-195 Culvert Reach-190 100-year2078.555383.145388.975388.975389.950.02593310.61392.68183.540.86 Reach-189.9 Lat Struct Reach-160 100-year1016.685374.505381.295379.625381.810.0080066.24243.47136.790.48 Reach-155 Culvert Reach-150 100-year1016.685372.705378.875378.875379.480.0132777.44235.5097.860.56 Reach-149.9 Lat Struct Reach-145 100-year878.355369.495375.455375.455376.570.0260498.71123.7675.730.82 Reach-140 100-year864.895363.575372.905370.775373.120.0050084.11301.39152.950.36 Reach-135 Culvert Reach-130 100-year864.895362.315370.775370.775370.920.0022003.21307.99130.670.26 Reach-110 100-year864.895356.305361.425360.205362.110.0110336.76141.3544.000.58 HEC-RAS Plan: Multi-profil River: RIVER-1 Reach: Reach-1 Profile: 100-year ReachRiver StaProfileQ USQ Leaving TotalQ DSQ WeirQ GatesWr Top WdthWeir Max DepthWeir Avg DepthMin El Weir FlowE.G. US.W.S. US.E.G. DSW.S. DS (cfs)(cfs)(cfs)(cfs)(cfs)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft) Reach-1119.9 100-year2092.0013.452078.5513.4518.510.940.475389.585399.545398.535391.425390.52 Reach-189.9 100-year2078.551061.021020.471061.02192.002.971.925380.405389.955388.975381.815381.27 Reach-149.9 100-year1020.47153.44866.48153.44175.572.170.445372.505379.495378.875373.145372.92 HEC-RAS Plan: MP Exist 072014 River: RIVER-1 Reach: Reach-1 Profile: 100-year ReachRiver StaProfileQ USQ Leaving TotalQ DSQ WeirQ GatesWr Top WdthWeir Max DepthWeir Avg DepthMin El Weir FlowE.G. US.W.S. US.E.G. DSW.S. DS (cfs)(cfs)(cfs)(cfs)(cfs)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft) Reach-1119.9 100-year2092.0013.462078.5513.4618.520.940.475389.585399.545398.535391.425390.52 Reach-189.9 100-year2078.551066.951016.681066.95192.002.971.935380.405389.955388.975381.815381.29 Reach-149.9 100-year1016.68150.41864.89150.41175.572.170.435372.505379.485378.875373.135372.90 ($)Damage GregoryCanyonCreekCriteriaandAssumptions GregoryCanyonCreek Table17 Parameter Criteria/Assumption PertheCity'scriteria,maximumallowabledepthis12"at Flowdepth thedeepestpoint. Streetimprovements,whereproposed,wereonlydeemed necessaryatintersectionswheretheslopewasgreater ImprovementLocation than4%.Streetimprovementsforthelengthofthestreet wereproposedforslopeslessthan4%. Themostconservativeslopeof1%foundinthebasinwas Slope usedtodeterminethemaximumsafestreetconveyance CostsforculvertandpipesweredevelopedusingtheUrban Culverts DrainageMasterplancostestimationspreadsheet. Aunitcostof$0.26perlengthofchannelperdischargewas Channel usedforchannelimprovements. Costforstreetimprovementsweredevelopedusingunit Streets ratespulledfromUrbanDrainage'sBidTabs. Perthe City'sdirection,ablockageassumptionof20%was CulvertBlockage usedtomodeltheculvertimprovements. FlowratesfortheFLO2DmodelwerepulledfromtheHEC Flowrates 1dataprovidedforbasins212and213. Terraindatausedforthe2Dmodelingwasdevelopedfrom Terrain the2013LiDARdataprovidedbytheCity. FLO2D Roughnessvaluesforthe2Dmodelingweredeveloped Manning'sn usingacombinationoflanduseandstreetlocations. Thecostforthesedimenttrapsisanaverageofthecosts CostprovidedinMuller'sSiteSourcereportonFourmile Canyon. ThemodelingofthedetentionupstreamofFlagstaffRoad Sediment ModelingusedtheblockageassumptionfortheFlagstaffculvertfrom Trap theEffectiveFEMAmodelof50%. Thewidthofchannelgradingimprovementswasassumed tobethewidthofproposedculverts.Itisassumedthat Widths Detention retainingwall/wingwallswouldbeusedtolimitthe encroachmentonadjacentproperties. Channelimprovementlengthswerebasedonthefollowing assumptions: 1.UpstreamofCulvertbarrelsanexpansionof4:1was usedtotransitionfromtheexistingchanneltothe Channel ExpansionandContraction 2.Downstreamoftheculvertsacontradictionof1:1was Grading usedtomovefromtheculvertbarrelstotheexisting channel. TheseratiosweretakingfromHECRASmodelingguidance. ALTERNATIVE ANALYSIS MEMORANDUM Acronyms and Abbreviations BCABenefitCostAnalysis cfscubicfeetpersecond CUHPColoradoUrbanHydrographProcedure FEMAFederalEmergencyManagementAgency FISFloodInsuranceStudy HAZUSMHHazardsUnitedStates(FEMA)MultiHazard HECHydrologicEngineeringCenter HECRASHydrologicEngineeringCentersRiverAnalysisSystem LOMRLetterofMapRevision UDFCDUrbanDrainageandFloodControlDistrict USACEU.S.ArmyCorpsofEngineers WRABWaterResourcesAdvisoryBoard GREGORY CANYON CREEK ALTERNATIVE ANALYSIS MEMORANDUM Gregory Canyon Creek Mitigation Study Open House March 30, 2015 Summary of Public Comments Received Purpose of Meeting Summary of Open House Comments: Gregory Canyon Creek Flood Mitigation Study March 30, 2015 Open House March - April 2015 Online Questionnaire Public Comments 1. Are you supportive of the City of Boulder Staff Recommended Plan? a.Yes, overall. I am relieved to see channel improvements proposed in the lower creek, as well as prioritized HHZ properties to acquire. I have lots of questions about the details, but I understand those are not well-defined yet. (J. Jimenez) b.The comments I made to the 15 people doing the walk were lost. My idea is to make the storm intake across Willowbrook cover the same area north of the culvert as well as above the culvert. (J.Imig) c.I think it is a well researched, well intentioned plan. I support the efforts but understand that individual property owners (myself included) will draw conclusions based on impact to their own properties. (K. Campbell) d.Yes. (L. McGowan) e.Yes. (M. Moench) f.Yes. (J. Butcher) g.Yes. (D. Schouten) a.Yes. We attended the open house on March 30, and appreciated the opportunity to talk with staff about the draft proposal. Since my home is next to the Anderson Ditch, I support making that a pipeline, running below ground. During the flood, it filled to the top with silt next to my home. (R. Roser) 2. What other improvements do you suggest? b.Spoke to Christen Shepard and Franz to explain the idea (also on a blue sticky note). (J. Imig) c.Signs on potential risk on streets where flow is likely to be high in 10 year or 100 year events. (M. Moench) d.Continued vigilance of Willowbrook culvert. (J. Butcher) e.1. Bury overhead lines along 7th St. which would also prevent downed lines in big snow storms. 2. Raise the retaining wall in the Flatirons School parking lot, north side next to my property. (R. Roser) 3. Do you have comments about specific improvements proposed? a.I would like personal feedback as to whether this idea will be considered and a detailed explanation of why or why not. (J. Imig) b.I suggest contacting the owners of HHZ properties that the city desires to acquire, as they may not be aware of this. Chances are a couple of them might be interested in selling to the city in the next couple of years, and that may open up more options in specific areas. (J. Jimenez) th c.I would like to point out that the property owner at the NW corner of 6 and Aurora has constructed a fence across the creek channel. If this was permitted by the city, I would like to ask, why? If it was not permitted, I would ask the city to investigate. (K. Campbell) d.Thank you for all your hard work. Looks great. (L. McGowan) e.All makes sense. (M. Moench) f.I continue to be impressed with the professionalism & creativity of the staff. (J. Butcher) g.I would be pleased to discuss sharing costs of retaining wall (or solid fencing) of the school parking lot on the property line. (R. Roser) Gregory Canyon Creek Mitigation Study Open House and WRAB Meeting October 20, 2014 Summary of Public Comments Received Purpose of Meeting The purpose of the October 20, 2014 Open House and Water Resources Advisory Board (WRAB) meeting was to present the preliminary alternatives for the Gregory Canyon Creek Flood Mitigation Study and to receive feedback from the public and board members. City staff and the project consultants are assimilating the comments and suggestions received at these meetings, as well as additional comments received by the public, in order to continue to refine and identify the best alternatives. Summary of Open House Comments: We live in a beautiful city. We are fortunate to live near running water, but everything has a price! I think we should start whatever we end by deciding to do from Boulder creek going south. The culverton highland school land is 36"!! Since Canyon Blvd. is going to be impassable during a Boulder Creek 100 year flood, we need to ensure that Arapahoe is passable. Hence we need to expand the Arapahoe culvert first, and hopefully when we do others. As a stakeholder, I am willing to walk with Citystaff, grant aneasement, be taxed or whatever it takes to finish the project & help the Civic Area designers glam our Gregory Creek is not going to be forgotten. How are the alternatives going to be chosen? How will city decide when or how to purchase identified properties in hazard area? How does the city decide how big to make the different box culverts? The 31'x6' culvert at Euclid is a major concern to us. This is a major physical intervention that would impact us visually, aesthetically, and in the way we use our property in a significant way. I am concerned with the accuracy of the modeling. At no time was the culvert at 6th and Euclid, which is presently ~ 4ft diameter, at capacity in the 50-75 year event of 2013. Water flowed primarily down 6thand Euclid and down from Edward Smith Park. I don't see any attempt at mitigation of the Smith Park overflow. To truly utilize a 31' wide culvert at 6th and Euclid one would need to deepen the creek. That would destroy the deer/fox habitat along with removal of significant trees and vegetation. Occasional flooding would be preferred to this kind of destruction. BOTTOM LINE: the engineers have addressed lots of issues that I and neighbors have been thinking. Putting in large box culvertswill be a big improvement and "buy insurance"against rock/vegetation clogs. Modifying road grades/crowns (eg directing flow down 7th street) is exactly right. Good job at making the effort to reach out and educate the neighborhoods. Consider the following financing proposal: There may be home owners who are retired and thus "asset rich" and "income poor". They may be willing to make improvements to their properties, but not be able to afford them from current income. This could be accommodated by a grant to the owner for the improvements and a lien on the property to be paid off when the owner moves or by their estate. This would fit in the philosophy of "public-private partnership". All three alternatives seem viable and reasonable. However no particular improvement has increased priority, nordo the recommendations align with the 2001 Belt Collins problem areas. The 2012 mitigation suggestions or the actualobservations from Sept. 2013. Summary of Open House Suggestions: The storm drains in front of 833 Marine are old, and are inadequate for the kind of debris that cover them up. We've been cleaning up the drains for 60 years because they are too small. It appears that the SECOND culvert under Euclid Ave, about 30'-40' tothe west of the proposed 31'x6' culvert has been overlooked in the study. It likely should be considered as part of any flood mitigation- maybe two smaller culverts? What about the 100 year trees that border the creek? What care would the city take to maintain their health? A) The city shouldbeaware that a high flow event down 7th street (Univ. - Arapahoe) will destroy the paving and curbs. This is not against doing the redirection, just a heads up on future repairs. B) As a property owner, I have invested in flood mitigation measures. The ones I did prior to 2013 worked well. I believe that this is a "private" or "public project"not just a city project. 1.) Strongly suggest purchasing the property in the high hazard at 1655 9th street. There are 2 houses, one of which is 2ft from the creek channel and should be the highest priority. 2.) The culvert enlargements should be considered at the same time as the up-and downstream channel enlargement. I liked the Pennsylvania roadway removal plan that was considered. Summary of WRAB Meeting Comments: Lives near Flatirons Elementary School, really appreciates where city is going with their plan and agrees that conveying a 100 year flood out of the question. Read study in its entirety. Alternatives proposed do not necessarily match what actually happened on the ground during the flood. Problematic area during this event that may not adequately be addressed at 7th. Does not have a strong feeling on option three in the roadway. Feels that spending money to make the roads convey without hurting propertyis money well spent. People are open to having flood mitigation done on their properties, but there are possible challenges there. Impressed with how accurately earlier studies match up with what was seen during the flood event. May be able to leverage earlier studies going forward. Lives midway on creek and has specific question regarding two maps and noticed there is a chart in attachment A that shows different culverts and what improvements would look like in a 10-year plan or maximum culvert (35x6).The 10 and 50 year maps only show maximum 50-year extent. Comments were heard during open house questioning this finding showing 35 foot culverts on the 10-year map, which isn’t actual benchmark for 10-year event. Requests clarification whether the mapsreflect 10-year or maximum numbers and asks if maps need updating. Wants to thank the board for hearing the neighborhood last year and putting neighborhood’s name out there for potential for growth, which shows a lot of thought. Concerns about map showing 35-foot culvert and hopes that Board will take closer look at document from CH2M Hill to address and consider street conveyance. Appreciates Board taking a closer look at this creek and looks forward to the future. Didn’t have problems like University and 7th. Suggests putting energy into conveyance because Mother Nature is going to decide, not what planners decide. Water went back into Gregory Creek because a car diverted it. This area is packed with cars and not enough parking. Lives on College and appreciates looking into this issue. Mentioned culvert at College Avenue, which was filled with fences and BBQ grills that were piled into culvert, forcing water to run over the creek onto other properties. Suggests looking at this issue and better advising people not to put objects in the creek bed. Mentioned 22-foot wide culvert at Aurora and feels that a 35-foot culvert is too excessive. Lives on College, family built house in 1950. At height of flood, banks took all the flood waters, bank to bank and held a 1.5 – 2 feet of water before touching his foundation. Some of the street did have water conveying and he built diversion with 2x4’s which diverted water down College, past Flatiron Elementary School. According to charts – what happened on College is being compared to what happened on Pennsylvania, which are not comparable. Stone bridge on his property has weathered 3 major storm events in his lifetime, which is a good model. Lives below Anderson Ditch. Asks what kind of incentive programs are being considered for property owners to keep stream beds clean? Lives at 7th and Pleasant and thinks that street conveyance is a good idea. With some work on 7th, a lot of the damage could have been avoided. East side was severely damaged. Could make a difference in the future with better street conveyance. From:Pearen, Keith L To:Knapp, Katie Subject:Gregory Canyon Alternatives Analysis Date:Tuesday, October 21, 2014 3:12:20 PM Katie, First, great job last night. Well thought out presentation. I thinkyour line of thinking on how to go about this projectis spot on! I think your approach to get the WRAB involved early and often is great. Totally agree that it is not feasible to upgrade all for 100yr flows and a 10yr approach is reasonable. My impression, the culvert widths with 10yr flow and 20% blockage are still large (14’ to 20’) relative to the stream bed (12’ max) and Sept ’13 demonstrated need. I had a few more thoughts after listening to the full discussion last night: First, Is it possible to update the % blockage for some of the existing structures (Table 5 and ‘Improvements in Public Right of Way’ Table) that performed adequately in the Sept ’13flood? It makes little sense to prioritize those structures that performed well in Sept ’13. If we revise the th Blockage %down from 50% to 20% or 0% can they (Aurora, College, Pleasant, University, 8, Marine, Arapahoe) be shown to accommodate the 10 year flow? If we can show them by analysis to be good for 10yr, then perhaps money can be focused elsewhere. Second, it makes sense to Utilize a phased approach to Gregory Creek Improvements: Phase 0: Obtain easements that are necessary for Phase 1 improvements Obtain easements for: o Private Drive at Old Baseline Private Drive at NW Corner of Willowbrook Cul-de-sac Drive to School North of Arapahoe Have easements obtained prior to WRAB reconvene – Project is a non-starter without o them Phase 1: High Need improvements in public right of way and in easements obtained in Phase 0 Focus on structures that are unable to convey 10yr flow and experienced issues o during the Sept ’13 event Private Drive at Old Baseline Willowbrook improvements (culvert and regrade) Euclid Culvert Pennsylvania Road Removal (Pedestrian Bridge) th 7 Avenue Drive to School North of Arapahoe th The following were all OK during Sept’13 (Aurora, College, Pleasant, University, 8, o Marine, Arapahoe) Phase 2: Street Conveyance Measures Implement proposed street conveyance measures o Willowbrook street mods and new pipe thth 6 street from Euclid down (or Rosehill to 7 as shown in the mini-master, but th this makes less sense because of flow combination with 7 at Anderson Ditch) Either way, Euclid should be identified as a creek to surface street transition. This is not shown in the CH2M report and should be added. th 7 street from Anderson Ditch down th 8 street from Pleasant down (Questionable cost/benefit with numerous major changes) Phase 3: Debris traps, Channel Enhancements, Property Acquisition and Re-mapping Obtain easements for channel enhancements in areas that will not convey 10yr flow o Install debris traps Bank stabilization Property acquisition for High Hazard Properties o Re-Mapping o Thanks, Keith From:Keith Pearen To:Knapp, Katie Subject:Re: Gregory Alternatives Date:Thursday, October 09, 2014 2:27:32 PM Katie, Thanks again for keeping us in the loops as this process progresses. I had a chance to read the report and have some comments in addition to your comment on the proposed removal of Pennsylvania Ave culvert (thanks!): 1.Page 1, Paragraph 1: Gregory creek is identified as a "left bank" tributary of Boulder Creek. Should be right or south. These things are assigned looking downstream. 2.Table 3: the location of "1/3 of discharge at Aurora Ave, with 2/3 placed on the local highpoint" makes no sense. 3.Table 3: Should confluence with Boulder creek be included in this table (2092 cfs with 100 yr return interval)? 4.Table 3: Consider a more readable format with location in the first column and return intervals of 2, 5, 10, 50 and 100 as columns 2 - 6. 5.Page 3, Hydraulics Section: Mixed tense and "deliverable for the this analysis." makes no sense. 6.General: LOMR is never defined. 7.Table 8: Good list of potential improvements. No indication that they were evaluated at any point in this report. Are some recommended? All? 8.Page 7: "Channel Geometry between Euclid and College is unable to convey the 10 – year storm event without causing infrastructure damage." Really? Haven't seen a model, but this seems like one of the larger channel sections. Surprising Conclusion! This is not consistent with Sept '13 observations. 9.Figures 5 - 7: Red, green, and blue boxes mean? CH2M Recommendations? 10.Figures 5 - 8: Potential improvements listed in Table 8 are largely ignored. If not included, why not? Were they evaluated? 11.Figure 5: "Install a 23' x 6' box culvert" under 7th street near flagstaff Elementary is inconsistent with physical geometry of site. Existing culvert is at least 100' in length. 12.Figures 6 and 7: Please remove the improvements that were already proposed in Figure 5 (Option 1) from these figures. 13.Figure 6: "5-ft channel bottom 4.5-ft depth 2H: 1V side slopes" proposed between Euclid and College already exists. 14.Table 2a and 2b: Map needed to correlate river stations used in the tabular data. 15.Table 2c and 2d: Discussion of the "Lateral Weir" seems to be missing entirely from test. These tables are never referenced in text. 16.Table 10: Is it possible to prioritize these Culvert Improvements or determine an order of operation in which these are to be done so the least capacity conveyance is always highest priority? I know it is an initial draft, but I would expect a little better from CH2M (I used to work for them)... Thanks again for keeping us in the loop, Keith On Wed, Oct 8, 2014 at 4:36 PM, Knapp, Katie <KnappK@bouldercolorado.gov> wrote: Hi Keith, There is a link to a “very” draft alternatives analysis on the upper right corner of the project website. I have already provided the engineering consultant with a list of comments, so this will be revised prior to the meeting. One of my comments was to include the pedestrian bridge option, which they do not currently show. Please feel free to provide comments at any time or at the meeting. Katie From: Keith Pearen Sent: Friday, October 03, 2014 12:24 PM To: Knapp, Katie Subject: Gregory Alternatives Katie, Is there something that shows the potential alternatives for Gregory Creek that we can see prior to the meeting on Oct 20th? I checked the website and it has been updated to show the Oct. 20th meeting, but didn't see any new proposed alternative. Thanks, Keith From:Laz Nemeth To:Knapp, Katie Subject:Gregory creek Date:Tuesday, October 14, 2014 1:18:55 PM You want to put in multiple 30 feet by 6 feet box culverts? the concrete really ugly ones? laz From:Laz Nemeth To:Knapp, Katie Subject:Re: Gregory creek Date:Tuesday, October 14, 2014 1:28:53 PM oh yeah and please explain how the math on the last table makes sense. specifically 7th, pen, college and euclid culverts of multiple different sizes are claiming 100-50% blockage, to me it reads like enron accounting. laz From:Helen El Mallakh To:Knapp, Katie Cc:Dean, Kristin Subject:Re: Incorrect reporting of Willowbrook Rd Culvert Dimensions on the Alternative Analysis Memorandum Date:Friday, January 23, 2015 12:36:26 PM Hi Katie, I think that you are wrong about the width times height. That may be what was supposed to be done in this memorandum, but these numbers make no sense. So I want to make sure that I understand this recommendation for Willowbrook Rd., the recommendation is for a culvert 18 feet wide by 7 feet high? That is not physically possible given where the home on the intake portion of the culvert would be. Moreover, the recommendation is for a 40-foot wide culvert at 6th and Aurora? There is utterly no need for these recommendations to be even brought forward. This is completely questionable. For the Willowbrook and Aurora culverts, the culverts far exceed the width of the creek beds on the properties. Where does Gregory Creek even approach 40-feet in width inside the city limits? No where. Whether these are low probability projects or not- they aren't feasible without absolutely ruining people's property. The fact that no new hydrological analysis was undertaken is also undermining the memorandum's recommendations. What is so disturbing is that there are areas along Gregory Creek that are in DIRE need of flood control improvements. These neighborhoods want projects. We didn't need a larger culvert during the last flood at Willowbrook. We needed a different trash rack, but what we really needed was for the city to remove the trash rack about 24 hours before it did. Helen El Mallakh 850 Willowbrook Rd. On Jan 23, 2015, at 8:59 AM, Knapp, Katie <KnappK@bouldercolorado.gov> wrote: Hi Helen, The call-outs do not indicate past projects, but what could be constructed at each location. The culvert dimensions are width x height, and do not show lengths. Because there have already been improvements constructed at Willowbrook and Aurora, I don’t anticipate that improvements at those locations will be high priorities. The next submittal from CH2MHill will include benefit/cost ratios that will help us come up with a recommended plan. Katie From: Helen El Mallakh [mailto:elmallak@swbell.net] Sent: Friday, January 23, 2015 4:49 AM To: Knapp, Katie; Dean, Kristin Subject: Incorrect reporting of Willowbrook Rd Culvert Dimensions on the Alternative Analysis Memorandum Hi Katie and Kristin The culvert on Willowbrook is already 18' by 9' (length by width) and it is 5' in height. So I believe that a mistake was made on figure 5 (3 of 3) page 17 which has written "18' by 7' box culvert" . Suggested change: culvert dimensions from "18' by 7'" to "18' by 9'" I would assume that this is a mistake and that the suggestion is not to place a smaller culvert in place on Willowbrook. I think that there's also a problem with the legend and that the red-bordered text boxes are projects that have already taken place. You will find that the culvert at Aurora and 6th street "Install 40' by 6' Box Culvert" was installed in 1995/96. The legend is not clear enough and the wording could confuse the public. I would recommend using "installed" instead of "install." Perhaps it would be useful to indicate to the public that these were past flood upgrades. Thanks Helen El Mallakh 850 Willowbrook Rd. Boulder, CO 80302 303-442-4014 From:Helen El Mallakh To:Knapp, Katie Cc:Dean, Kristin Subject:Re: Easement at 850 Willowbrook Road Date:Thursday, January 22, 2015 5:08:43 PM Hi Katie Last question for you and Kristin is on page 17, under Category 1 of Channel and Facility Maintenance, there are two text boxes on our property: "Channel Grading to Accommadate Larger Culvert" and "18' by 7' Culvert box." Does this mean that we would be getting a new larger culvert on our property, because I think that our existing culvert is 18' by 7'? Also, our property already have some of the deepest channel grading along Gregory Creek. Can you guys please explain this? I think it might have been what took place in the 1996/97 Flood Control? Thanks Helen From: Sent: To: Cc: Subject: From:Helen El Mallakh To:Dean, Kristin;Knapp, Katie Subject:Re: Credibility Issue with this process Date:Wednesday, March 25, 2015 5:18:25 AM Dear Kristin, Regarding the Gregory Creek Feb. 13 Revised Alternative Analysis, the consultants still have not put in the HEC-RAS variables and their parameters that they used to make the suggestions on the culvert sizes. Can you please have them send these variables and parameters to me so we can have them for our neighborhood organization - even if they are not included in the analysis itself? Also, the maps in the Feb. 13 Revised Alternative Figures are not drawn to scale in regards to the size of the culverts. This causes confusion and is misleading. Lastly, given that so many of the sewer lines broke going into people's houses, there is no mention of what the city is doing related to this problem. Regards Helen El Mallakh 850 Willowbrook Rd. Boulder, CO 80302 303-442-4014 Hi Kristin Having used HEC-RAS, I find that the underlying variables and assumptions are critical. It is fundamentally driven -as is all modeling software - on the validity, scope, and rigor of the inputs. Since many of us have had to hire our own hydrologists, I think that in the memorandum the key variables, their parameters, underlying assumptions, and various cases/scenarios that were fed into the model should be listed. This information would be useful for our hydrologists. Moreover, the sediment assumptions are very important for this particular creek. This should not be very difficult to add to the updated report. Thanks Helen El Mallakh From: Sent: To: Subject: From: Sent: To: Subject: From:Helen El Mallakh To:Knapp, Katie;Dean, Kristin Subject:Engineers Preferred Alternative -new storm inlet in front of 850 Willowbrook Road Date:Thursday, March 26, 2015 7:51:45 AM Attachments:1996-Willowbrook-Culvert-Replacement.pdf Dear Katie and Kristin I just reviewed the Engineers Preferred Alternative for Gregory Creek. Please be advised that the location as drawn for the new storm inlet in front of 850 Willowbrook Rd. would interfere with our sewer line connection. In fact, the idea of a storm inlet in front of 850 Willowbrook Road was already evaluated and deemed as infeasible because of the sewer line issues in the 1996 Willowbrook Road Culvert Replacement project as part of flood control. Moreover, due to the somewhat odd connection angle with our sewer line coming into the city sewer line(due to the culvert and 1996 flood control project), there have been numerous problems, including its breaking in the 2013 flood event. You should probably speak with public works as they have more detailed records of this including having to repair issues. Regards Helen El Mallakh 850 Willowbrook Rd. Boulder, CO 80302 303-442-4014 From:Helen El Mallakh To:Knapp, Katie Cc:Dean, Kristin Subject:Re: Engineers Preferred Alternative -new storm inlet in front of 850 Willowbrook Road Date:Thursday, March 26, 2015 8:43:17 AM Hi Katie and Kristin I wanted to give you the contact at Public Works who had to fix our sewer line/inspect it. His name is David Garcia and his phone number is 303-441-3350. He can better explain the issues around the sewer line connection. I really would not want the city to do anything that would further compromise the sewer line connection unless David Garcia was consulted first. Regards Helen El Mallakh 850 Willowbrook Rd. Boulder, CO 80302 303-442-4014 From: Sent: To: Subject: From:Helen El Mallakh To:Dean, Kristin;Knapp, Katie Subject:Re: Concerns regarding proposed storm inlets on Willowbrook Road Culvert - Gregory Creek Draft Staff Recommended Plan Date:Monday, March 30, 2015 8:13:40 AM (1) SEDIMENT & CARRYING CAPACITY CONCERNS: (2) ENGINEERING PROBLEMS WITH EXISTING SEWER CONNECTIONS AND SEWER LINE BREAKS: (3) INEFFECTIVE IN DIVERTING FLOOD WATERS OFF OF THE STREETS: (4) POTENTIAL TO DO MORE HARM WITH LIMITED UPSIDE (5) EASEMENT ISSUES: (6) FUNDS ARE BETTER SPENT ON OTHER PARTS OF GREGORY CREEK: From:Helen El Mallakh To:Dean, Kristin;Knapp, Katie Subject:Storm Inlets cannot be placed in front of driveways - Draft Proposal for Gregory Creek Date:Monday, March 30, 2015 10:05:16 AM From:noreply@bouldercolorado.gov To:Dean, Kristin Subject:Gregory Canyon Creek Flood Mitigation Study Form Submission Date:Wednesday, April 01, 2015 5:42:44 AM support_draft_plan:no draft_plan_comments:IdonotsupporttheproposedstorminletsontheWillowbrookculvertinfrontof445 ChristmasTree&850WillowbrookRd.Oneofproposedinletisinthedrivewayof850Willowbrookandinlets aren'tsupposedtobeplacedinfrontofdriveways.Additionally,storminletsfillquickly.Thus,thereislimited upsidetothisproposal.Aftertheflood,anewtrashrackwasalreadyinstalledonthisculvert.Thisnewtrashrackat theWillowbrookculvertshouldaddresstheproblemswehadduringthe2013flood. other_improvements:TheCity'ssewerlinesandproblemsaren'treallyaddressedinthisproposal.However,I supportrelocatingthesewerlineoutoftheGregoryCreekGulchwhereitisnowsituatedandrelocatedoutofthe gulchpath.Inthelastflood,thesewerlinewashedoutintheGregoryCreekGulchandmanypropertieswere adverselyaffectedbysewerlinebreaksupstream(damagespaid100%bythepropertyowners). specific_improvements:Inthefloodplan,itshouldbeindicatedwhathasalreadybeendonetoaddressissues.For example,wehaveanewtrashrackontheWillowbrookCulvert,butthatisn'tindicated.Ithinkit'snecessarytonote whereimprovementshavealreadybeenmade. name:HelenElMallakh address:850WillowbrookRd. email:elmallak@swbell.net From:Knapp, Katie To:Jack Jewell Cc:Dean, Kristin Subject:RE: Email list - FW: Gregory Canyon Creek Mitigation Study Open House Date:Tuesday, January 27, 2015 9:58:55 AM Hi Jack; Thanks for contacting us and providing your comments, questions, and observations. Your input is very helpful and appreciated. In response to your questions: Table 5 illustrates what is shown in the current floodplain model for Gregory Canyon Creek. This model was developed by Belt Collins, was adopted in 2010 and is what the current floodplain boundaries are based on. Our records show that there are 2 different crossings at Aurora: a smaller 36” diameter pipe (Crossing #1) and a big double box culvert (Crossing #2). Figure #1, the 2013 flood extents, is based on information collected in the field, aerial imagery, and personal accounts of what was observed. We have received conflicting information in some locations and understand that there are discrepancies. We continue to revise and refine this data as we are able to verify information. The detailed mapping you th provided was very helpful in putting together this mapping and we will reassess the 6 St. area above Aurora. The different alternatives being evaluated include improvements to street sections that could help convey flood spills down streets instead of across private properties. Included in this evaluation is also a new pipe alignment that would collect flood waters that flow down Willowbrook Road and enter your property. This option includes a drainage inlet at the Willowbrook bend and a pipe that would convey water under the Gregory Gulch and under Aurora, back to Gregory Creek on the downstream side of Aurora. We are expecting to receive a more complete evaluation of the costs and benefits of the different alternatives from CH2MHill soon and will be updating the website. We will then work on developing a preferred alternative based on costs, benefits and input from the neighborhood. I hope you will be in town for one of the site walks and/or the open house. The input from you and your neighbors is so important in helping us develop a successful mitigation plan to guide future improvements. Please feel free to contact me to further discuss the study. Katie Katie Knapp, P.E., CFM Engineering Project Manager City of Boulder, Public Works - Utilities 303-441-4077 From: Dean, Kristin Sent: Monday, January 26, 2015 9:41 AM To: Jack Jewell Cc: Knapp, Katie Subject: RE: Email list - FW: Gregory Canyon Creek Mitigation Study Open House Hello Mr. Jewell, I did some research and found that you are on the city’s Boulder Flood Info email list, but that you were not on the email list for the Gregory Canyon Creek Mitigation Study list. I have now added you to that list. I have cc’d Katie Knapp, the project manager for this project, on this email. She can answer the questions you posed below. I assure you that we will not be walking on your property during the site walks. We do hope you can attend one of them, though. We anticipate receiving refinements to the alternatives analysis in the very near future and will post the updated proposal on the web once they are received. Please do not hesitate to contact me with any further questions. Best Regards, Kristin Dean, AICP Utilities Planner City of Boulder, Public Works - Utilities 303.441.4289 From: Jack Jewell [mailto:jack@greenvcsel.com] Sent: Saturday, January 24, 2015 2:37 PM To: Dean, Kristin Subject: Email list - FW: Gregory Canyon Creek Mitigation Study Open House Date: Friday, January 23, 2015 at 3:43 PM To: Jack Jewell <jack@greenvcsel.com> Subject: Fw: Gregory Canyon Creek Mitigation Study Open House GCC regory anyon reek Flood Mitigation Study Opportunities for Public Involvement Site Walks with City Staff City Staff welcomes you to join us as we walk Gregory Canyon Creek and discuss the recommendations for flood mitigation. We plan to conduct these walks on two separate dates in an effort toaccommodateeveryone's schedule. Come join us for the entire walk or just your area of interest: Monday, Feb. 9 at 3 p.m. Tuesday, Feb. 10 at 11 a.m. We will start at the Willowbrook Rd. cul-de-sac and then walk the creek to its confluence with Boulder Creek. If you cannot attend either of these dates, staff may be available to set up individual meetings. For more details, please contact Kristin Dean at 303-441-4289 or deank@bouldercolorado.gov Open House An Open House to review the revised alternatives for the mitigation plan will be held on March 30, 2015 from 4:30 to 6:00 at the Flatirons Elementary School Library Water Resources Advisory Board This project will be reviewed at the April 20, 2015 Water Resources Advisory Board (WRAB) meeting at 7 p.m. City Municipal Services Center, 5050 Pearl St. Forward this email Forward this email Thisemailwassenttoelmallak@swbell.netbydeank@bouldercolorado.gov| |RapidremovalwithSafeUnsubscribe™|PrivacyPolicy. UpdateProfile/EmailAddress CityofBoulder|1739Broadway|Boulder|CO|80301 From:Marjorie K. McIntosh To:Knapp, Katie;Dean, Kristin Cc:Dick McIntosh Subject:Thanks Date:Wednesday, February 04, 2015 8:39:47 AM Good morning, ladies. Thanks for coming to our house yesterday to talk about plans for flood mitigation work along this section of Gregory Creek. We were relieved to hear that the pipe option is not being considered seriously and that you do not intend to encourage water at the top (cul-de-sac) end of Willowbrook Road to come up onto the road, rather than staying in its normal bed as long as possible. We continue to feel that getting as much water as possible back into the creek bed immediately below the main culvert under Willowbrook Road, before it gets to the bottom of the road, makes excellent sense. It seems worth considering ways to channel water back into the creek bed across a distance of no more than 20 feet, as opposed to figuring out what to do with it once it reaches the bottom of the road, where it has to cover the full stretch between Willowbrook and Aurora, going through our and Jack's properties. Yes, of course some of the water will do that, but we hope strenuously it will be no more than happened in 2013. We hope you will also bear in mind our suggestion about turning our property into a publicly owned area that could be landscaped to slow the flow of water, though a series of large steps across the entire front of the property, and then allow it to settle along the back before moving on down towards Aurora. Would it be worth just asking Curt about this idea? Jack left his jump stick with Dick, who will get another one, transfer the relevant movies and photos onto it, and have it ready for Kristin at the Walk next Monday. We are fortunate to have people like you in charge of this process, willing to listen to local property owners' concerns. with thanks, Marjorie 1 To: Katie Knapp, as Project Manager for Mitigation Planning for Gregory Creek From: Marjorie K. and J. Richard McIntosh, 870 Willowbrook Road, Boulder Re: The proposed street-based plan for Gregory Creek at the north end of Willowbrook Road Date: January 26, 2015 A. The Damage to Our Property and a Sewer Line Caused by the 2013 Flood Our house and yard were badly damaged by the 2013 flood. After the culvert under Willowbrook Road became blocked, much of the water that came down the lower section of the street crossed over into our yard. It ate away the dirt around the foundations of our house on the south and southeast sides, undermined two 60-ft Spruce trees, and dug a trench 10 feet deep at its lowest. The foundation plate of our house was exposed, and for a while it was not clear that the building could be saved. Some of the water coming down Willowbrook Road from the blocked culvert flowed into the driveway of our neighbors to the east before it reached our yard. From their driveway, that water went immediately back into the normal creek bed. What came through our yard was only part of the total volume of Gregory Creek. The water going through our yard flowed directly above a sewer line that extends along the eastern boundary of our property from the street to ourNE corner.At the backof the yard, it destroyed a concrete manhole and a segmentof the sewer line itself. These had to be repaired on an emergency basis by a city crew while the rain was still coming down, and a permanent replacement was installed later. The entire lower level of our house’s interior was flooded, to a depth of 3 feet, and had to be rebuilt from scratch. Because water also flowed rapidly around the west and north sides of the house, all the surveyor’s marks at the corners of our property were washed away. Since the flood, we have paid for three visits from a structural engineer to see whether any permanent damage was done to the foundation or walls of the house. His final opinion is that the house is still structurally sound, but only because the house was so solidly built in the 1950s. B. The Steps We Have Taken To Protect Our Property in the Event of a Future Flood In developing a plan that is likely to protect our house in the case of a future flood, we worked with a water engineer (Curtis Stevens), a hydrologist, a surveyor, and a landscaper, and we sought legal advice from our attorney. The resulting plan was based upon the volume and speed of the water (measured as cubicfeet per second) that came through our yard in the 2013 flood. We paid a substantial amount of our own money to install the walls, concrete channel, detachable fencing, and landscaping needed to implement that plan. 2 C. The Plans Produced by the City’s Consultant for Gregory Creek The consultants hired by the City to produce various plans for mitigating future damage in the Gregory Creek area never contacted us. No one from the City has ever spoken with us about those plans. When we saw the three plans on the website, we assumed that the street-based version that shows all of Gregory Creek’s water coming down Willowbrook Road and through our yard was so ludicrous that the City would immediately discard it. We therefore paid little attention to it. We were shocked to receive the recent notice about a walk led by a City officer through this area, following the street-based plan. D. Problems with the Street-Based Plan from Our Perspective The plan shows all the flood water being diverted onto Willowbrook Road at the top of the cul-de-sac, rather than remaining in its normal bed until the culvert. It does not show any water passing down our neighbor’s driveway and back into the normal creek bed. Instead, the entire volume of water would come straight down Willowbrook Road, picking up speed as it passed over the smooth paved surface, until it hit the curve at the bottom of the hill. At that point, the map shows the entire flow going through our yard. The water moving through our yard according to this plan would be larger in quantity and faster in speed than was the case in 2013, when the water had come down the road for a shorter distance, and some of it had already been diverted. Because the foundation of our house barely survived the 2013 flood, any additional volume and speed of water flowing past it is likely to cause the building to fail. The additional amount and velocity of water flowing down through our yard are likely to do even more damage to the underground sewer line that lies beneath that route. Increased flow and speed of the water as it exits our yard at the NE corner will have seriously detrimental effects for the two property owners directly downhill from us: Jack Jewel, on the th SW corner of Aurora and 6Streets, and Jane Butcher on the NW corner. E. Our Response During the 2013 flood and its aftermath, City officials were consistently helpful in addressing the problems that resulted. We have been strong defenders of your response, in the face of disgruntled neighbors who were furious with the City for failure to keep the culvert open and thereby protect their property. But we are utterly unwilling to give the City permission to use our property as the designated watercourse for the entirety of Gregory Creek in the event of another flood. Any such plan would place us, our house, and our possessions at grave risk and would lower the value of our property dramatically. 3 The legal implications of the City’s proposed plan are obvious. We hope that action of that kind will not become necessary. Copied to: Curtis Stevens, The Sanitas Group Constance Eyster, esq., Hutchison, Black, and Cook Pennsylvania Avenue Flood Repair Public Comments 05.12.2014 Purpose Pennsylvania Avenue was damaged during the September 2013 flood and the City of th Boulder is evaluating different options for repairs of the section of road between 6 and th 7 streets, where Gregory Canyon Creek crosses the roadway. We asked members of the community to choose one of three alternatives or share another alternative with us. Alternative 1: Replace the existing culvert (drainage pipe) and rebuild the o roadway to pre-flood conditions. Alternative 2: Remove the culvert and roadway above the creek, close the road to o through traffic and build a pedestrian bridge over the creek. Alternative 3: Remove the culvert and construct a new roadway with a o significantly larger culvert or a vehicular bridge over the creek. Summary of Public Comments General Comments Alternative 1: 4 in favor Traffic on the road and school access is better mitigated on option 1. Option 2 o looks like it would cause more blockage. There would be through traffic, less congestion, a paved road, and less mud. o School parking traffic will be decreased if back to pre-flood conditions. There would be less speeding traffic to suddenly stop at the closed road and dead end to turn around. Alternative 2: 114in favor Alternative two is much better for our neighborhood. o The culvert will continue to get clogged and spill over. o This has the greatest opportunity to mitigate future property damage from o structure blockage and volume. The culvert narrowing the creek bed at Pennsylvania caused the flooding west of o the creek; Therefore if it is restored as it was there will be a problem of liability. It also seems that option two is less expensive. Regardless of the alternative, the type of maintenance upstream to the head o waters is critical for safety. The flood in September 2013 highlighted the limitations of culverts. Alternative two is consistent with City Council’s goals of encouraging pedestrian traffic as opposed to vehicular traffic. I would like the peaceful space and green belt. There would be calmer traffic o during school when kids are walking and a significant water flow improvement during flood episodes. It’s very nice to see the creek again from the bridge. We can manage very well o without this street and have been doing so since mid-September. Thank you for finding some funding to get started on the Gregory Creek flood plain mitigation. We know there are lots of mitigation needs elsewhere, but please don’t forget that Gregory Creek needs more attention sometime in the future. Adequate access exists without Pennsylvania. Why rebuild it? o The chance of the road washing out again will be lessened. A pedestrian bridge o would be nice for the neighborhood. We walk our dog in the neighborhood a lot. Option two is a safer alternative. The children at Flatiron Elementary will have to contend with less traffic on Pennsylvania. Option one would risk rocks getting caught in the culvert again. If option two is selected, please move the west-side cul-de-sac further west. o Great for habitat/wildlife restoration and a safe route for bikes, pedestrians and o flood mitigation. Use the east side of the bridge area as a family meeting area for walking and o thth cycling families. Pennsylvania can be a riding route to 6. 6 should be a marked bike route to University and down to the Boulder Creek Path. Benches and bike racks should be provided. Thanks! th This will not eliminate future flooding. The culvert under 7gets blocked every o time we have a severe thunderstorm. The grate catches debris and blocks very quickly. Pedestrian friendly. o Better neighborhoods. o This street hardly has any traffic to begin with. The pedestrian bridge close to o the school would be a great addition! Option #2 sounds like a much better fit for the neighborhood! o This would be so nice for walking my kids to school! o This culvert caused my house to flood! Rebuilding it the same way is just plain o stupid! Having a pedestrian bridge and cul-de-sac is the best idea I have heard from the city in years! I think a pedestrian bridge here would be a great addition for no extra cost! o These kinds of options continue to make Boulder the special place it is. It seems like option 2 is clearly the right solution. Why rebuild something that o will be blown out again? Let the stream run naturally as it was intended. Thanks for the opportunity to provide this input. I visit the neighborhood often and would enjoy walking over the foot bridge and o seeing the stream below. There doesn't seem to be enough traffic to warrant rebuilding the road/culvert. Having seen firsthand the devastation that the clogged culverts caused o throughout Boulder with the floods in September, I'm inclined to say where there is an opportunity to allow water to flow in a more natural manner and still allow access to communities, this is the appropriate way to proceed. I am a fan of anything to improve pedestrian access to our beautiful creek. o As someone who grew up in the neighborhood and still lives in town I like the o second idea. Seems to be a much better idea for flood control and the idea of an open creek bed through there seems kind ofnice. If it floods again you’re going to have the exact same problem if you build it back. Let the stream flow! o The pedestrian bridge option is a great one for this neighborhood! o Pennsylvania Ave has a number of issues that make for an accident waiting to o happen. These issues include: Icy conditions - due to lack of snow removal and direct sunlight, steep grades - west side, blind corners - Dean Pl. Reducing the amount of traffic by replacing the culvert with a foot bridge would lessen the risk of an accident on this street. I live on Pennsylvania and Gregory Creek goes under my deck. I would LOVE o Option 2 with a pedestrian bridge. I think it offers a safe route to school for students walking or biking as well as slows down and/or lessens the traffic impact before and after school. In terms of emergency vehicles, since Pennsylvania only runs between 6th and 7th, it is already confusing and difficult to find so improved mapping and signage could effectively bring attention as to how to reach us on the West side via 6th or Dean Place. I also really like that this option allows for better wildlife and habitat restoration along with flood mitigation, in particular for the folks downstream. I am a big proponent of Alternative Two. I think any chance to restore a stream o corridor should be capitalized on. There are ecological/habitat benefits, safety benefits regarding flood control and aesthetic benefits for those living there. I'm all for number 2! Very hopeful that we can begin a small step of prioritizing people traffic over car o traffic. This is a really great opportunity to decrease flood risk while re-building! The o extra cost of a pedestrian bridge is absolutely worth it for the downstream flood reduction. This seems like a great opportunity to increase multi-use pathways in Boulder. I o have been in this area often and agree that drivers often speed through, even though there is a school nearby. It is such a beautiful area, would love to see it become more pedestrian friendly. I live at 637 Pennsylvania Ave and would like the pedestrian bridge please o Given the proximity to the school building I think it makes sense to reduce some o traffic in this area. Option #2 would improve the pedestrian character of the neighborhood and o provide important flood relief that could not easily be obtained by a culvert. It seems like an option to take into account future flooding would be a good o idea. Does local traffic require a bridge? Option 2 is a nice compromise. Flood improvements for future storms but at o more than half the cost of a vehicular bridge. #2 has the most positive attributes. o great job with some good alternatives --thanks staff o Versus option 1, Option 2 seems like the better long-term compromise that's o potentially a good investment capable of preventing damage otherwise in the future. With flooding though, it's a zero-sum game---every link of the chain would need to be more robust in order to prevent problems. Making one link stronger may have little net positive effect to the city. If this is one of the weakest links, then by all means, please treat as such. As a parent of students at Flatirons Elementary, I love the idea of closing this o dangerous street to vehicles and walking my kids to school over a pedestrian bridge. It is imperative to our neighborhood that Alternative TWO is implemented, since o the pre-flood condition is the one which enabled the flooding in the first place. The cost to restore our home is now close to $50,000, and we know that others in our area have spent as much or more. We are asking the city in good conscience and good faith to help us to keep this from happening again. It is option number two which is most beneficial to our neighborhood, as it o would allow more flood conveyance AND, very importantly, would interrupt the speeding and dangerous driving on Pennsylvania. The school already has good access on nearby streets, and the pedestrian bridge would be available for everyone. Thanks for your work on this. I live adjacent to the existing culvert and am in strong support of increasing the o flood conveyance capacity. Option 2 is the most reasonable cost option that accomplishes this. Alt. 2 has, by far, the strongest support from those effected by this problem - o those who were directly flooded by the breech of Penn. Ave. It does feel like the estimate for this repair could be greatly reduced by looking at simpler options for the bridge. Perhaps a use of pressure treated lumber beams instead of metal. The city cannot really choose Alt. 1 since that would put it in the position of intentionally creating a greater risk of flood and the possible liability. And since it is 7 months since the flood and nothing has been done, I see no value at this point of its being the fastest fix. That time is long past. It also seems the estimate for this job is way too low. Alt. 3 is too expensive and there is no good reason to do it. A final cheapest alternative would be to simply remove the ton of gravel that the city dumped in the hole, which raised the likelyhood of further flooding, and fence the whole creek gap off on both sides at Penn. Ave. and have no access. Yes to a pedestrian bridge! o Pedestrian Bridge seems wonderful! o I hope this can still be received. I live on Pennsylvania and think this option is the o best solution; for pedestrian/bike safety and access, wildlife habitat and flood mitigation. Alternative 3: 7 in favor Car bridge or better yet, a draw bridge. o Square opening (rock wall exposed in flood) with roadway over (open to cars). o Build a vehicular/pedestrian bridgeor street and keep flow way open. o Car bridge. o Re-engineer the culvert to convey flow consistent with expected flow from o culverts above and open street to vehicle traffic as well as pedestrian traffic. Flatirons Elementary School has been open well over 50 years and will be most affected by the decision. It is considered by Flatirons staff that closing the street would have a negative effect on the traffic flow relative to school operations. The biggest push to close the street thus far has come from a resident who o moved in to the neighborhood 8 months ago and has stated he was "tired of having cars from the school park on Pennsylvania" and was going to try to get the street shut down. I actually prefer alternative 2 EXCEPT the fact that Flatirons Elementary School is o located in the area. Students with special needs, combined with the occasional presence of bears and mountain lions, makes it critical for fast emergency response times. I support alternative 3 because it is the most comprehensive and it is the best for o the nearby elementary school due to the access for emergency vehicles (which is negatively impacted by alter #2). This culvert was supposed to be replaced in 1996, but the project ran out of money. It is long overdue. Also, given that mountain lions have begun to hunt around gregory creek in town, it is a bad idea to create an ""attractive"" environment for wildlife as suggested by alter. 2. Due to the school and the number of small children, we must put public safety first and select option 3. The price is commensurate with the benefits. Otheroptions: 4 in favor Reduce parking on east side of stream. Turn that area into a gathering place for o kids and parents. Allow residents to access their drives, but reduce traffic and parking. I'm not advocating for any particular solution, but do have the following concern: o if the capacity at Pennsylvania is increased, does that just mean that the flooding as the Creek goes under 7th will be that much worse? Or further down, as it goes under Pleasant? Or University? Or Eighth? It seems to me that having the creek top over and go sluicing down broad streets during a flood is not the worst solution -- it keeps the flood shallow enough not to drown anyone, or to cause major structural damage (just wet basements, which one can recover from.) alternative 2 is probably best, but i would like a draw bridge. o alternative two or alternative 3 with a drawbridge. o APPENDIX REACH INVENTORIES, PROJECTS AND OPPORTUNITIES Stream: Gregory Canyon Creek Reach: 1 (GRC 05, 06, 07, 08, 09, 10) Location:Boulder Creek to College Avenue Habitat conditions: Vegetation structure: Excellent to good Native plant habitat: Poor Bird habitat: Poor to very poor Aquatic habitat: Fair to poor Primary (streambed): Fair to poor Secondary (channel morphology): Poor Tertiary (bank stabilization): Fair Vegetative bank stability: Fair Other conditions: Creek runs through residential yards Creek is narrow and channelized Most of reach is deeply entrenched with vertical walls Opportunities: Flood Management: Significant split flows occur at University Avenue and Marine Street causing several properties to be added to the floodplain. th Arapahoe Avenue, Marine Street, 8 Street, University Street, Pleasant Street, Pennsylvania Avenue and College Avenue are all overtopped by 100-year discharge. Channel is small, incised and located on private property $FTXLUHSURSHUWLHVLQWKH+LJK+D]DUG=RQHDFFRUGLQJWRWKHFLW\¶VSUHIORRG acquisition program. Outreach to adjacent neighborhoods to raise awareness of flood hazards Habitat protection: Low priority for restoration due to location in residential yards Homeowner education to improve conditions for native species coupled with an incentive program or technical assistance Revegetation / re-channelization downstream of University Avenue Water quality: Develop and implement stream habitat improvement matching grant program for adjacent properties Educate adjacent neighborhoods to encourage backyard management to protect habitat, wetlands and enhance water quality APPENDIX REACH INVENTORIES, PROJECTS AND OPPORTUNITIES Stream: Gregory Canyon Creek Reach: 2 (GRC 01, 02, 03) Location:College Avenue to city limits Habitat conditions: Vegetation structure: Very good Native plant habitat: Good Bird habitat: Very good to good Aquatic habitat: Fair to poor Primary (streambed): Fair to poor Secondary (channel morphology): Fair to poor Tertiary (bank stabilization): Excellent to poor Vegetative bank stability: Excellent to poor Other conditions: Creek runs through residential yards Creek is narrow and channelized '\HU¶V:RDGRFFXUUHQFHLQ6PLWK3DUN Opportunities: Flood management: Flagstaff Road, Willowbrook Road, Aurora Avenue and Euclid Avenue are overtopped by 100-year discharge. 100-year floodplain has less split flow and is located in proximity to the channel in this reach. There are a few structures in this reach that are highly impacted by the High Hazard Zone. Acquire properties in the HiJK+D]DUG=RQHDFFRUGLQJWRWKHFLW\¶V pre-flood acquisition program. Outreach to adjacent neighborhoods to raise awareness of flood hazards Habitat protection: Landowner and homeowner education about the threat of exotic ornamentals Brunnera, Vinca minor, Vinca major) ( Russian Olive removal (UDGLFDWH'\HU¶V:RDGRFFXUUHQFHLQ6PLWK3DUN Some planting of native cotton woods might restore the balance of species composition Water quality: Develop and implement stream habitat improvement matching grant program for adjacent properties Educate adjacent neighborhoods to encourage backyard management to protect habitat, wetlands and enhance water quality Wetland Evaluation Wetland #: 40502 Former #:14T_R_S:T1NR71WS36 Investigator:A. Carpenter, C. BrowneDate of Visit:7/2/2004Obs. Method:Viewed from property boundary General Location:Gregory Creek east of Mountain Parks and south of Boulder Creek Description:Steep, rocky intermittent stream that flows northward along eastern edge of a Pierre shale bedrock formation, draining into Boulder Creek. Characterized by generally narrow active channel with fairly steep gradient. Precipitation in foothills to the west supports seasonal flows in creek. (Includes tributary to Gregory Creek which flows in from the west along the north edge of Smith Park, between Aurora and Euclid Streets.) Wetland Origin:NaturalPrimary Water Source:Creek Hydroperiod:Intermittently floodedMax WaterDepth (ft):1.5 Major plant communities present% of wetland area% Vegetated:90 narrow leaf cottonwood/ mixe herbacousd35% Bare ground:5 urban tree/ mixed herbacous60 % Water:5 open water5 FUNCTION AND VALUE ASSESSMENT Ratings: 5 = very high, 4 = high, 3 = medium, 2 = low, 1 = noConfidence in rating: c = high, b = medium, a = low Groundwater 1bGeohydrologic map indicates groundwater recharge or discharge are possible. Effectiveness of the recharge Recharge function is limited by impermeable bedrock near surface, narrow channel, and intermittentflows. Uncertain the extent to which infiltration into fractures recharges water in deeper formations. Groundwater 2bLocal discharge of rainwater infiltration into creek likely but the thin overburden limits opportunity. Discharge Flood Storage / 2bRough streambed slows flows somewhat and small pools in lower section offer minor storage benefits. Floodflow Alteration Shoreline Anchor. / 3bFairly dense understory and tree cover along banks, though rocks are significant factor in erosion control. Stabilization Sediment Trapping / 2bHigh velocity flows likely to transport sediments through the system, though small pockets of short residence Retention sediments were observed in pockets along the bank and in pools. Nutrient Retention 2bAbundance of trees and understory (long-term) Nutrient Retention 2b (short-term) Food Chain Support 3bGood supply of leaf litter from overhanging vegetation and good export flows. Grates and control structures may (export) trap some of larger material. Food Chain Support 3b (within basin) Fish Habitat / Aquatic 1b Diversity Wildlife3bdeer observed and diversity of trees and understory offers food and shelter, but narrow buffer reduces Habitat effectiveness Active 1b Recreation Passive Rec / 3b Heritage Value Comments:Gregory Creek runs though residential back yards starting at edge of Mountain Parks and flows north to Boulder Creek (access to the creek was generally limited to where it intersected with city streets) CITY OF BOULDER WATER RESOURCES ADVISORY BOARD AGENDA ITEM MEETING DATE: April 27,2015 AGENDA TITLE: Information Item --Preliminary Draft 2016Utilities Budget (Water, Wastewater and Stormwater/ Flood Management) including the 6-year Capital Improvement Program (CIP). PRESENTERS: Jeff Arthur, Director of Public Works for Utilities Ken Baird, Utilities Financial Manager Annie Noble, Acting Principal Engineer for Flood and Greenways Douglas Sullivan, Acting Principal Engineer for Water, Wastewater and Stormwater EXECUTIVE SUMMARY: -year planning budget, this year for the time period of 2016through 2021. The Water Resources Advisory Board (WRAB) role in this process is defined in the Utilities staff has formulated initial revenue and expenditure projections for each of the three utility funds through the year 2021. Within the budget process,City Council approves and appropriates funds only for the first year, 2016. In addition to the six year CIP described above, Utilities staff develops a 20-yrCIP. The purpose of the 20-yr CIP is to look at long range needs for all three utilities. The 20-yr CIP is a valuable mechanism to look at upcoming regulatory requirements, asset management needs for aging facilities, and the associated debt service for existing bonds. This agenda item provide CIP. Input from WRAB will guide staff in preparation of a draft CIP for discussion by WRAB at the May meeting. WRAB will be asked to make a recommendation to City Council regarding the 2016-2021CIP at its June meeting. The Planning Board will review the complete city CIP, including utilities, in July. City Council generally plans for two study sessions in September, prior to adopting the 2016 budget. This packet contains preliminarydraft information concerning the 2016 Utilities Budget and the Attachment A draft 2016-2021Utilities CIP. The fund financials ()have been updated to reflect actual revenues and expenditures for 2014,and the revised budget for 2015. These fund financials incorporate recommended changes to the CIP. There will be other,likely less significant, guidelines on April 20. Fiscal Impacts :in increased investment in Utilities infrastructure with 2015 rate increases of 5% in Water, 30% in Wastewater and 75% in Agenda Item 6 Page 1 Stormwater/flood Management. Future rate increases were also identified to maintain this level of service, and for 2016 the projected rate increases were 8% in Water, 5% in Wastewater and 4% in Stormwater/Flood Management. The preliminary update to the Fund Financials and CIPs reflect that these rate increases will provide sufficient revenues, subject to the deferral of some projects, for the recommended budget. Public Feedback : A public hearing and recommendation is scheduled for the June WRAB meetings. At the June meeting, staff will request that the WRAB provide a final recommendation onthe proposed 2016-2021 CIP to City Council and associated rates changes. BACKGROUND and ANALYSIS: CIP projects are any major projects requiring the expenditure of public funds (over and above operation expenditures) for the purchase, construction, or replacement of the physical assets of the community. Projects are typically over $50,000 in total project cost, and result in a durable, long lasting asset, with a useful life of at least 15 years. Capital Improvement Program projects are divided into five categories: Capital Enhancement - result in the expansion or significant improvement of an existing facility or asset. Capital Maintenance - result in the repair, replacement, or renovation of an existing asset with a useful life of at least 5 years. Capital Planning Studies - result in the development of a study or plan which is intended to identify, plan, or prepare for the construction or acquisition of capital assets or capital program. Land Acquisition - result in the acquisition of real property, such as land, mineral or water rights, or permanent easements. New Facility or Infrastructure result in the construction or acquisition of a new asset or additional square footage of an existing asset. The city developed nine CIP Guiding Principles to create a city wide understanding of which projects are chosen to be included in the CIP and shape capital planning decisions made throughout the CIP process. The CIP Guiding Principles also ensure individual department priorities for CIP funding are aligned with city goals. The CIP Guiding Principles are included Attachment B. as During the annual CIP and budget process, individual projects are identified as requiring a Community and Environmental Assessment Process (CEAP). The purpose of the CEAP is to assess potential impacts of conceptual project alternatives in order to inform the selection and refinement of a preferred alternative. The CEAP provides the opportunity to balance multiple community goals in the design of a capital project by assessing a project against the policies outlined in the Boulder Valley Comprehensive Plan (BVCP) and departmental master plans. The criteria for projects requiring a CEAP include a project that could have: significant impact on an environmental, social or cultural resource; community controversy; more than one possible alternative or a requirement of internal or external permitting. All CIP projects are reviewed by an inter-departmental staff group to determine whether a CEAP will be required. Agenda Item 6 Page 2 primary focus is to provide quality water services, as desired by the community, in a manner which emphasizes efficient management of fiscal and natural resources, wastewater and stormwater/flood management) is a separate enterprise fund established to services while maintaining designated reserves and meeting debt service requirements. Revenues generated from monthly utility bills are the largest source of revenue for each utility, in 2014accounting for about 66% of revenues in the Water Fund, 84% in the Wastewater Fund, and 78% in the Stormwater/Flood Management Fund. Other significant sources of funds include development fees (Plant Investment Fees), hydroelectric revenues, funding from the Urban Drainage and Flood Control District (UDFCD) and interest earnings. Approximately fifty-five percent of the Utilities expenditures are allocated for rehabilitating and improving the capital infrastructure either through the capital improvements program (cash financed) or through annual debt payments for revenue bonds that have been issued to fund capital improvements. This percentage was forty-five percent last year before the 2015 Budget rate increases. Maintaining existing infrastructure is critical todelivering safe and reliable services to our customers. Investment into maintenance of existing infrastructure is less costly in the long run. Other significant uses of funds include water treatment operations, wastewater treatment operations, system maintenance and water quality operations. Revenues The revenue forecasts have been updated and incorporated into the fund financials. Forecasted revenues from Plant Investment Fees (PIFs) have been adjusted up in the Water and Wastewater Funds to reflect recent private development activity. Hydroelectric revenues have also been adjusted with the current estimates based on projected generation and energy sales. The preliminary draft 2016 budget provided with this memorandum reflects the following billed revenue increases:8% Water, 5% Wastewater, and 4% Stormwater/Flood Management. The following table summarizes the 2015 adopted increase and preliminary projections for 2016- 2018. The preliminary 2016 increases are in bold. Table 1 Proposed Rate Increases 2015201620172018 Water5%8%8%8% Wastewater30%5%5%5% Stormwater/Flood Management75%4%8%8% Agenda Item 6 Page 3 The revenue increase represents the amount of additional revenue to be generated from the monthly utility charges. The actual rate increase (e.g. $ per 1,000 gallons) may or may not be equal to the revenue increase depending on whether any changes in consumption or use are factored in when calculating the actual rates. For example, if there were a projected decrease in consumption, in order to generate 8 need to increase greater than 8% to generate the needed revenue requirements. Utility Bill Comparisons Estimated single-family residential Attachment C compared with other Colorado Front Range communities. shows the water bill comparison, and an8% Water increase puts Boulder in the middle for single-family residential Attachment bills. The bill comparison for a 5% increase in the Wastewater Utility is shown in DAttachment E shows the Stormwater/Flood annual bill and the impact of the 4% increase, which remains the highest of the group. With it numerous drainageways, topography, and proximity to the foothills, The City of Boulder has the highest flood danger for any municipality in the State of Colorado. Since 2016rate proposals are not yet available for the other cities, the survey uses their 2015 rates. Attachment F Afourth chart,shows the annual bill comparison when all three utility fees are included. Of the fifteen communities in the survey, Boulderwould be the fifth highest of the fifteen Front Range Communities surveyed. Construction Cost Inflation Construction cost inflation is tracked using the Engineering News Record (ENR) Cost Index for Denver and the Colorado Department of Transportation (CDOT) Colorado Construction Cost Index. The ENR index is a composite index based on costs for: 1) local portland cement, 2) local 2x4 lumber, 3) national structural steel, and 4) local union wages plus fringes for carpenters, bricklayers and iron workers. The CDOT index is a composite index based on costs for 1) unclassified excavation, 2) hot bituminous pavement 3) concrete pavement, 4) structural steel and 5) reinforcing steel. The ENR index is more reflective of equipment and building construction such as projects that occur at the treatment plants. The Colorado Construction Cost Index is more reflective of heavy civil construction such as roadway and major drainageway work. Based on this information and recent City bids, it is recommended that capital improvement construction costs continue at a rate of 4% during the planning period. Customer Bill Impact The proposed preliminary 2016revenue increases (8%-5%-4%) would increase a typical monthly utility bill by $4.98, or an increase of $59.88 annually.The following table provides a breakdown of the potential increases by utility. Agenda Item 6 Page 4 Table 3 Average Monthly Bill Impacts MonthlyBill MonthlyBill Monthly 2015Rates2016RatesDifference Water$36.59$39.48$2.89 Wastewater$30.23$31.78$1.55 Stormwater/ Flood Mgmt$13.46$14.00$0.54 Total$80.28$85.26$4.98 Impact of Rate Changes The impact of a 1% increase in revenue varies substantially across the three funds: Table 4RateImpact 1%2%3% Water$235,000$470,000$705,000 Wastewater$185,000$370,000$555,000 Stormwater / Flood Mgmt$100,000$200,000$300,000 Also, as a point of reference for budgeting future bonds, $100,000 provides for debt service coverage on a bond of approximately $1,000,000. So a revenue reduction of $100,000 could mean reduced funding for a one-time capital expense or capital bond project by $1,000,000. ANTICIPATED REVENUE BONDS: The current 2016-2021utility fund financials reflect several bond issuances (and associated debt payments) to fund the following capital projects: Water: 1.Betasso Water Treatment Plant Improvements ($24million in 2016) to fund improvements to maintain compliance with federal Safe Drinking Water Act regulations 2.Southern Water Supply Pipeline II (Carter Lake Pipeline) and the 2018 Waterline Replacement budget ($37.6 million in 2018) 3.Barker Dam Outlet and Boulder Reservoir Water Treatment Facility ($10.3 million in 2020) to fund repairs to the outlet works Wastewater: 1.Sanitary Sewer Bond ($10 million in 2015) to fund replacement of large diameter interceptor pipe 2.WWTF Improvements ($18.5million in 2020) to fund phosphorus treatment to meet Regulation 85 requirements : Stormwater and Flood Management 1.Wonderland Creek and Four Mile Canyon Creek projects ($23million in 2015) 2.South Boulder Creek Improvements ($25million in 2018) to fund improvements designed to mitigate flood hazards in the South Boulder Creek West Valley area Agenda Item 6 Page 5 The following table summarizes the debt obligations of the utilities, the year the debt is retired and the average annual debt payment. Items shown in italics are projects that are anticipated to be funded by issuing bonds. Table 5 Debt Obligations Year Debt Approximate Annual UtilityProjectsis RetiredDebt Payment WaterBoulder Reservoir WTF2016$858,000 Improvements Multiple Projects including Silver 2019$2,522,000 Lake Pipeline, Barker Purchase Lakewood Pipeline2021$2,066,000 Betasso WTP Imp. (2016)2036$1,920,000 Carter Lake Pipeline and Waterline 2038$3,568,700 Replacement (2018) Barker Dam Improvements and2040$983,773 Boulder Reservoir WTP Imp.(2020) WastewaterWWTP Improvements2025$3,500,000 WWTP Improvements 2030$674,000 Sanitary Sewer Pipe (2015)2035$800,000 WWTP Improvements Reg 85 2040$1,757,500 (2020) Storm/Flood Multiple projects including Goose 2018$385,000 Creek Improvements Wonderland Creek and Four Mile 2035$1,725,000 Canyon Creek Imp. (2015) South Boulder Creek Imp. (2017)2037$437,000 SouthBoulder Creek Imp. (2021)2041$1,425,000 *Projects shown in italics are proposed bonds The Water U debt related to the Windy Gap project. This debt will be retired in 20 debt payment is approximately $1,650,000. The utility continues to maintain a high credit rating, most recently Aa1from AAA from . This is due to sound financial practices, one of the most important of which is maintaining sufficient reserves. CAPITAL IMPROVEMENT PROGRAM Attachment G See for the proposed 2016-2021Water, Wastewater, and Stormwater/Flood Utility CIP. Agenda Item 6 Page 6 Water Utility Source Water Facilities: As with any long standing water supply system, significant portions of the Source Water Infrastructure Facilities are over 50 years old and many are already over 100 years old or contain significant elements that are over 100 years old. In addition to source water facilities owned and operated by the Northern Colorado Water Conservancy District, the city owns and operates 14 source water storage dams/reservoirs along with approximately 29 miles of water supply transmission pipelines with 4 source water hydroelectric/pressure reducing facilities (and four treated water hydroelectric/pressure reducing facilities). Source Water Storage Facilities: Storage (AF*) Dam/Facility Initial Construction and Repair Dates /Length & Pressure Green #1 175 +/- 1910 A Green #2 333 +/- 1910 A Green #3 285 +/- 1910 A Green #4 116 +/- 1910 Green #5 74 +/- 1910 Albion 1,111 1910 - 1913 Goose 1,036 1908, 2000 repair Island Lake 334 1900, 2010 repair Silver Lake 3,987 1887, 1907, 1927, 1956, 1966 (final raise) B Lakewood 42 1906, 1996 full rehabilitation Skyscraper 146 1940 1909, 1947 upstream repair, 1980 spillway modification, Barker 11,686 B 1985 post-tensioned anchors for stability 1909, 2011 downstream stability berm and toe drain repair, Kossler 120 B 2015 upstream embankment face repairs pending Boulder Reservoir 13,300 1955 B 3.6 miles Silver Lake Replaced 1997-1998 Pipeline 660 psi max. Agenda Item 6 Page 7 Storage (AF*) Dam/Facility Initial Construction and Repair Dates /Length & Pressure 10.8 miles Lakewood Replaced 1994-2004 Pipeline 800 psi max. 11.7 miles 1905-1910 original with assorted Barker Gravity Gravity plus 90 psi Line pipe repairs since 2001 max. in siphons 10,000 feet Boulder Canyon Original construction 1909-1910 Penstock 800 psi max. 2,900 feet 1964 ,CML added- 1985, Replaced 2010 Betasso Penstock 900 psi max. Source Water NA (Betasso 1987, Silver Lake 1998, Lakewood Hydroelectric 2004, Boulder Canyon 2013) Facitlities *Acre feet A Restricted Storage Level by State Dam Safety Branch B - High Hazard Dam Designation Four of the source water storage dams are also rated as high hazard potential due to downstream loss of life in the event of a theoretical failure, which requires the facilities to meet more stringent dam safety requirements. The city has been implementing repairs on a priority basis according to operational needs and also in general agreement with the 2009 Source Water Master Plan. Updated priorities and schedules for the projects identified in the master plan are reflected in the 2015 CIP. The Treated Water System Includes: Two water treatment facilities Over 460 miles of distribution and transmission lines associated with over 6,500 valves, 28,000 meters, 5 water quality monitoring stations, 4,600 fire hydrants and various other venting, draining and corrosion protection devices Agenda Item 6 Page 8 Three pump/pressure reducing stations Six treated water storage tanks Four treated water hydro facilities and one pressure reducing station Betasso Water Treatment Facility was put into service over 50 years ago with various modifications and additions over the years. Much of the original equipment is still in use. In some cases the original equipment has served the City beyond its predicted useful service life. The need to replace aging equipment and bring facilities up to current best practices for water treatment is the main driver for the 2016 plant improvement project. underwent major improvement projects over the past 15 years to bring the treatment process up to current standards. Some original equipment is still due for replacement and is the main driver for the money budgeted in 2020. The annual distribution main replacement program has been in place for over 15 years and has focused on the that makes up the majority of the system. Recent funding and program development has begun for the transmission mirrors growth patterns in the years old still in service. The three pump/pressure reducing stations that are critical in moving water between east and central Boulder underwent complete overhauls in 2010. The original installations date back to the construction of the Boulder Water Treatment Facility. The six treated water storage tanks range in age from over 110 years old to 20 years old. Kohler Reservoir is due for a roof replacement in 2016 and the rest are subject to regular maintenance and inspection. From 1986 to 1999 the four treated water hydroelectric facilities and the pressure reducing station at the mouth of Boulder Canyon were constructed. While these facilities are relatively more and more maintenance. Installation of new power generation equipment is proposed for the 101 Pearl pressure reducing station in the six year CIP. 2014Accomplishments 1.The city completed its FERC license exemption process in September 2014 for the Boulder Canyon Hydroelectric Project based on receipt ofa US Forest Service Special Use Permit for the Barker Gravity Pipeline. The SUP was required for pipeline access road segments thatcross USFS lands. 2.ROW purchasing and environmental studies continued in 2014 for the Carter Lake Pipeline Project. An agreement with the NCWCD provides for the preliminary design and ROW acquisition along the designated and permitted total alignment including those Agenda Item 6 Page 9 sections in Boulder County. Final design and construction is proposed in the CIP for 2017 and 2018 respectively. 3.The annual maintenance repair program continued on the Barker Gravity Pipeline. Pipeline sections repaired in 2014 include: a.An emergency repair of a 90 foot long section at risk of slope failure just upstream of Siphon No. 7 in the alignment segment closest to Barker Dam. The repair included placing rock anchors and a pipe stability concrete saddle support to rock at the undermined section along with welded steel pipe across the section where the pipe bench was at risk of sliding. b.Concrete grouting of the deteriorating pipe sections in the segment from Siphon No. 7 to the P Grouting repairs and drain pipe / valve re-setting were also completed to eliminate significant leakage from upstream of the Measuring Weir Structure to the outlet tunnel. c.New Manhole Access and Drain Valve Vaults were installed on Siphon No.2 and Siphon No.3 after completing emergency repair on the Siphon No. 2 drain valve leak (i.e. new valve assembly installed). d.Grouting repairs were completed from Tunnel No. 1 to Siphon No. 1 at the damaged, misaligned and deteriorated pipe sections within the segment. 4.Silver Lake Watershed Dams: In 2014 an existing access path that previously only allowed ATV and foot traffic was improved so that four-wheel-drive pickup trucks and construction equipment can access the crest of Albion Dam. The road work was done in advance of the outlet system repairs, dam rehabilitation studies and construction activities. The valve house piping assembly and valves at Goose Lake Dam were scraped down to bare metal and repainted with epoxy paint to prevent further corrosion. The solar powered instrumentation system at Silver Lake Dam was initialized and tied into the data reporting channel of the new radio transmitter system. At Green Lake No. 3, the broken actuator gearing was repaired and the stem coupling lowered to allow operation from a newly installed platform at ground level. 5.A contract for the Barker Caretaker Residence was awarded and permitting as well as agency coordination continued. 6.The Betasso Hydroelectric Relay Project was completed in 2014. 7.The access bridge to the Boulder Canyon Hydroelectric Facility was rehabilitated and is now load rated for 20 tons. 8.Preliminary design and facility assessment for the Betasso Water Treatment Facility Project and completion of several preliminary studies. 9.Replacement of over 22,000 feet of water distribution main. Agenda Item 6 Page 10 10.Installation of new effluent mag meters at both water treatment facilities. 11.Hydraulic model updates that included updates to the pipe roughness coefficients, demands and inclusion of hydrant laterals. 12.Completion of flood restoration projects on treated water transmission mains. 13. 14.Post filter flash mix improvements and MIOX scrubber removal at the Boulder Reservoir Water Treatment Facility. 15.Gunbarrel Tank painting and structural steel rehabilitation. Projects Anticipated for Completion in 2015 1.Sunshine Pipeline inspection and replacement of 2,200 feet of transmission line between th Sunshine Hydro and 4/Mapleton. An access road will also be re-established along the length of the pipeline. 2.Preliminary investigation of transmission line replacement from Sunshine Hydro south to Chautauqua Reservoir. 3.Kossler Reservoir Concrete Facing Rehabilitation including re-establishment of freeboard for the PMF, spillway modification for the PMF, and repairs to the severely deteriorated concrete at the Outlet Structure 4.Barker Gravity Pipeline Repairs ongoing repairs in order of priority and availability 5.Barker Dam Outlet Gate Test ongoing plan to test / inspect gates as reservoir level allows 6.Albion Dam Assessment and Rehabilitation Alternatives Study this funding will be shifted/used in 2015 for reinforcing the temporary outlet repairs that were installed by divers in 2013. This will require draining of the reservoir which will depend on water supply and catchment conditions at the end of the summer/early fall. The rehabilitation analysis study will be shifted into 2016 with construction to quickly follow as the concrete face and the overall condition of the dam is continuing to deteriorate. 7.A full inspection of the Silver Lake Dam outlet conduit and control valve systems, required by State Dam Safety regulations, is scheduled for May 2015. In coordination with water supply and seasonal run-off periods, the dam is being lowered by supplying WTP demand to allow for the full inspection. 8.Barker Caretaker Residence is to be completed in 2015 9.The Sixth Internal Inspection of the Lakewood Pipeline is to be completed with a recommendation of potential pipe serviceability taking into account the type of pipe welding flaws previously discovered and corrosion rates documented to date. 10.Refurbishment of the Silver Lake Hydroelectric Bypass Valve (by city hydro staff and technical representatives from Mokveld Valve Inc.) 11.Replacement and installation of approximately 25,000 feet of water distribution main. Agenda Item 6 Page 11 Several thousand of those feet will be funded by a CDPHE grant to help flood affected properties annexing along Old Tale Road. 12.Final design and permit application for the Betasso Water Treatment Facility project. 13. 14.Integration work at the Orodell hydroelectric facility. 15.Meter and building improvements at Kohler and Maxwell hydroelectric facilities. Highlights of 2016-2021 Projects 1.It is recommended that the city continue its annual maintenance program of the Barker Gravity Line by prioritizing pipeline repair projects. In terms of condition assessment and importance to water supply, the gravity line is the highest priority in the source water system. The planned maintenance program for the gravity pipeline includes pipe replacement or lining in small segments over a number of years with a test section planned in 2016. Costs and installation rates for the test section will be used to update the 15 year rehabilitation/replacement plan for the Barker Gravity Pipeline starting in 2017. The 2017 to 2032 CIP costs in the present CIP Plan have been modified to reflect city pinion of likely construction costs from experience to date. It is recommended that capital funding be allocated in 2016to fund the Betasso Water 2. Treatment Facility Improvements project.The construction improvements are estimated at $24M. This is a s6-yr CIP estimate for a $12M bond in 2016. Last -yr CIP included major investment for future Betasso WTF projects in 2021 ($6M) and 2026 ($14M). numerous Betasso projects into a larger single project in 2016. The future projects would be removed from the CIP. This approach will utilize the large project economies of scale, meet the various CDPHE requirements, and also take advantage of favorable bond rates available at this time. A $2M project for the Boulder Reservoir WTF is identified in the 2020 CIP to address filter valves, a wash water recovery tank, and various site improvements. This project was originally identified in the CIP as a $5M project that also included significant pretreatment improvements. The pretreatment improvements will not be necessary if the Carter Lake pipeline project is completed. The Carter Lake pipeline would provide a better influent water quality eliminating the need for the pretreatment facilities. 4.Funding for the final design of the Carter Lake Pipeline is identified in 2017 and construction is identified in 2018. The Carter Lake Pipeline (also referred to as the Southern Water Supply Pipeline II) would be funded by project participants, including Boulder, and constructed, operated and managed by Northern. Project costs were updated with a new construction estimate provided by the Northern in 2014 and the previously forecasted costs have increased. The pipeline is considered the best long-term solution to water quality, operational and security vulnerability issues related to drawing water directly from either the Boulder Feeder Canal or Boulder Reservoir. The September 2013 flood event reinforced that the pipeline could also mitigate the potential for future problems in delivering water from the Boulder Reservoir WTP during future Agenda Item 6 Page 12 disaster events. The pipeline would potentially provide an opportunity to develop a new hydroelectric facility. Funding for construction of this facility is proposed in 2020. 5.CIP funding has been added for Boulder Reservoir in 2016 to inspect the Main and Auxiliary Outlet. To avoid draining the reservoir, this activity will require an underwater diving/inspection contractor. Due to corrosive water chemistry, potential relining or structural replacement of the auxiliary outlet steel conduit may be required once the conditions are documented (i.e. an alternatives analysis and design may have to be undertaken). 6.The Barker Dam outlet facilities are over 100-years old and in need of significant rehabilitation. However, as a result of the recent successful testing of a lower gate in typical condition and the inspection of Gates No. 1 through Gate No. 7 (30-inch) to confirm apparent readiness for service, funding has been delayed by an additional 2 years for final design (now 2019) and construction (now 2020) of the rehabilitation project. The outlet facilities would also provide an opportunity to develop a new hydroelectric facility and funding for construction of this facility is now allocated in 2024.Continued good reviews from operations for the stepped outlet gates (Gates No. 1 through No. 9) may allow a further delay of the outlet rehabilitation project subject to further evaluation of the mechanical reliability of the system. The 1910 spillway gates (dual 36-inch) are already showing signs of requiring replacement with the electrical geared actuator replacement as a priority. The downstream pipe segments encased adjacent to the spillway are leaking at the joints (i.e. infiltration present when not flowing full) thus most likely requiring a structural re-lining. The 2016 CIP budget was increased to allow for new actuators on the spillway gates with other future repairs to wait (if possible) until the outlet system rehabilitation study results. 7.In 2016 and 2017, CIP budget has been added for a study on the type of investigation required to evaluate the post-tensioned anchors at Barker Dam and to repair the grouted pads on top of the anchors in a two phased approach. The results obtained from the first phase repair on the dam crest will be used to determine if it is necessary to continue with replacing the grout pads on the downstream face, as these are much more difficult to access. 8.Due to previously documented issues with concrete deterioration and continued risk of plugging the outlet system at Albion Dam; the planned study, design and rehabilitation construction activities have been moved up in the CIP to the years 2016, 2018 and 2019 respectively. Due to this re-prioritization of the Albion Dam activities, the planned study and repair of the Green Lake No. 2 Dam has been moved out an additional year and may be moved out further if required for other priority tasks in the watershed. 9.The Kossler Dam Face Rehabilitation Project and the included concrete repairs to the Outlet Structure in 2015 has highlighted the need to also complete significant concrete and grouted riprap repairs to the Inlet Structure to the reservoir at the termination of the Barker Gravity Pipeline. $75,000 has been added to the CIP in 2016 for the Inlet Structure repairs to allow for continued operation without potential structural failure of Agenda Item 6 Page 13 retaining walls and grouted riprap. Once initial critical repairs are completed on the Inlet, both the Inlet and Outlet Structure will require replacement within approximately 10 years due to the condition of the concrete and the nature of the temporary repairs. A placeholder estimate has been entered in the year 2023 with design and permitting in advance by a year. 10.The CIP budget for the Silver Lake Hydroelectric Facility has been increased in 2016 through 2018 for PLC upgrades and replacement of the turbine needles/seats. 11.The CIP budget for the Betasso Hydroelectric Facility has been increased in years 2017 and 2018 for replacement of the HPU and transformer. The HPU is scheduled for replacement and City Hydro Staff has noted overheating issues at full capacity on the transformer. The transformer oil has been tested and will be monitoring closely to allow for a delayed replacement in 2018. 12.In 2017, the Boulder Canyon Hydroelectric Facility will require a 5-year inspection and CIP funds have been added. 13.A new CIP item has been added starting in 2016 for the Source Water Facilities Rehabilitation Program. This program, which is presently forecasted at $150,000/year, will allow for funds to be available for the non-forecast activities (i.e. unexpected emergency repairs, designs, permitting and or studies) which are typically required in keeping the city source water infrastructure systems in reliable condition. 14.Funding for treated water transmission infrastructure includes both assessment and replacement of critical pressure zone 3 pipes. During the summer of 2013 several transmission mains experienced failures that were repaired and revealed the need to replace certain pipe segments sooner than anticipated. 15.Evaluation and potential installation of hydroelectric generation equipment at 101 Pearl. Currently no power generating equipment exists at this facility. Wastewater Utility The September 2013 flood event highlighted numerous vulnerabilities in the wastewater collection system. The 2015 budget included a significant rate increase to fund new programs and projects to address the collection system rehabilitation. 2014Accomplishments 1.A City-wide inflow and infiltration (I&I) study of the wastewater collection system was completed in 2014. The purpose of this study was to quantify the rainfall induced I&I component entering the collection system. This I&I study was scheduled May through July 2014 to take advantage of the historically high groundwater that remained following the 2013 September flood event. The study utilized 58 temporary flow meters at locations throughout the system. The Agenda Item 6 Page 14 wastewater collections system hydraulic model for the 2014 Master Plan Update. 2. interceptor sewer. This project was a comprehensive condition assessment process that utilized TV inspection, laser and sonar technologies for the section of interceptor sewer from South Boulder Rd to the WWTF. The inspection revealed severe levels of corrosion and structural degradation in the downstream half of the interceptor system. 3. areas which had severe wastewater backups during the 2013 flood. No significant quantity of flood debris was identified. 4.Utilities staff continued the annual cured in place pipe (CIPP) lining program and lined approximately 10,000 over previous years because part of the funding for this program was reallocated to the inspection and flow monitoring projects. Projects Anticipated for Completion in 2015 1.IBM Lift Station construction project 2.WWTF Nitrogen Upgrades construction project st 3.61Street Interceptor Replacement construction project 4.WWTF Process Automation System (PAS) Phase I implementation 5.Annual CIPP lining contract 6.Medium diameter sanitary sewer condition assessment 7.Wastewater collection system condition assessment and debris removal 8.Wastewater collection system permanent flow monitoring Highlights of 2016-2021 Projects 1.The Wastewater collection system Condition Assessment Program is new in 2015. Utilities will complete a comprehensive wastewater collection system condition assessment over the next four years (2015-2018). This assessment will involve cleaning and TV inspection of approximately 360 miles of sanitary sewer. This program will help prioritize the wastewater collection system rehabilitation program. 2.The Sanitary Sewer Rehabilitation program has significantly increased funding that began in 2015. The projected annual budget is estimated at $2,250,000 in an effort to accelerate the lining program. This new funding level will permit the lining of the entire collection system in approximately 20 years. 3.The city received a new discharge permit for the 75th Street wastewater treatment facility (WWTF) with an effective date of May 1, 2011. City of Boulder staff negotiated a 6-year compliance schedule with CDPHE to allow for the design, construction, start-up and funding of the new facilities. Utilities will bid the Nitrogen Upgrades construction project in 2015. This project will include improvements to meet new permit regulations for total inorganic nitrogen (TIN) and daily maximum ammonia limits, which go into Agenda Item 6 Page 15 effect December 1, 2017. This proj will be completed in 2015/2016. 4.New CDPHE regulations concerning nutrient criteria, specifically Regulation 85 and Regulation 31, were adopted by the Colorado Department of Public Health and Environment (CDPHE) in March 2012. The criteria will pose serious treatment challenges for the WWTF and will have significant financial impacts. City staff has estimated approximately $18.5 million of funding in 2020 to address the phosphorus treatment improvements required to address Regulation 85. Regulation 31 contains much more stringent provisions and funding for this regulation is identified in the 20-year CIP with $11 million in 2029. 5.The Process Automation System (PAS) Strategic Plan was completed in 2013 and identified approximately $6,000,000 in instrumentation and controls (I&C) recommendations to be completed at the WWTF. Funding for these improvements is estimated at $600,000 per year (escalated at 4% annually) for the next 10 years. The PAS recommended Tier 1 (critical priority) projects will be completed in 2015/2016 at an estimated construction cost of $1,100,000. 6.The IBM Lift Station improvements project will be bid in 2015. The project will include various civil, mechanical, electrical, and instrumentation & controls upgrades to meet CDPHE requirements. The upgrades will involve modifications to expand the wet well capacity, new submersible pumps, an influent ogee weir, an intermediate floor with new -by emergency pump. The estimated construction cost is $1,000,000. The construction duration is estimated at nine months. 7.A comprehensive list of WWTF rehabilitation projects has been identified from the Wastewater Utility Fund Asset Management tool, and included in the 20-year CIP based on staff input, engineering studies and the asset management database. For the current 6- year CIP, funding for the rehabilitation projects has been allocated to various WWTF components as shown in the detailed CIP list. Stormwater and Flood Management Utility The city has a comprehensive flood management program designed to identify flood risks along the major drainageways, reduce those risks, minimize loss of life and property damage, and support recovery following major flood events. The overall process for meeting these objectives includes: updating the Flood Insurance Rate Maps (FIRMs), developing mitigation plans to identify feasible opportunities to reduce the risk of flooding and programming flood mitigation projects into the CIP. As a result of the September 2013 flood, funding was added in the 2015-2020 CIP as a placeholder for the design and construction of improvements along the various drainageways in anticipation of completing mapping studies and mitigation plans. Much of the funding shown in the 2016-2021 CIP was carried forward from , as many of these studies are still on-going. Agenda Item 6 Page 16 Flood mitigation plans are currently being developed for the following creeks: Bear Canyon Creek Gregory Creek Boulder Creek South Boulder Creek In anticipation of completing flood mapping studies this year, flood mitigation plans will be initiated in 2016 for the following creeks: Upper Goose and Twomile Creeks Below is a list of the schedule for each drainageway shown in the CIP and the changes in funding levels from the 2015-2020 CIP to 2016-2021 CIP. The current draft of the South Boulder Creek Mitigation Plan is anticipated to be presented to the WRAB in May and to City Council in August.The South Boulder Creek Phase I project cost is $10M was allocated to the project in 2018 to fund a regional detention facility at U.S. Hwy 36. This $10M figure assumed that the remaining $15 million would be funded through a grant. In th funding in 2018 based on a less optimistic expectation of receiving grant funding for this project. hown in 2016-2021. On-going funding was also shown in the 2015-2020 CIP for improvements along Wonderland and Fourmile Canyon Creek based on the 2011 Mitigation Plan recommendations. The Wonderland Creek Foothills to Winding Trail Greenways project will be bid this summer, and is currently estimated to cost $22.5M to construct. Last year the construction cost was estimated to be $20M, with the CIP including a $16 million bond and the assumption that the remaining $4M would be cash financed with carry over funds from 2014 to 2015. Funding previously budgeted for the Wonderland Creek project was used to cover costs ($5.1 million) for the September 2013 post-flood recovery work. While not reflected in the 2016-2021 CIP, the 2015 bond amount will be increased from $16M to $23M to cover the additional $2.5 million, as well as take advantage of favorable interest rates to cover a greater portion of the Wonderland project, th and the Fourmile project at 19Street that were originally intended to be cash financed. thnd Design of improvements along Fourmile Canyon Creek between 19and 22 Streets was put on hold following the September 2013 flood. The design work is now moving forward, with construction anticipated next summer. A CEAP was completed in 2012 for this project. This project has been added to the 2015 bond issuance for Wonderland Creek and funds carried over from last year will be used for future projects. A CEAP is also currently underway for flood th mitigation and Greenways improvements along Fourmile Canyon Creek upstream of 19Street. The CEAP will be reviewed by the Greenways Advisory Committee and provided to WRAB as an information item at the end of this year. On-going funding from 2016-2021has been included in the draft CIP to design and construct these improvements. Agenda Item 6 Page 17 Status and Funding Changes for the Major Drainageway Projects DrainageMapping Mitigation PlanFunding Changesfrom 2015-2020 Studyto CouncilPlannedto 2016-2021 Bear Canyonupdated1 st Quarter 20162015, 2016none th Gregoryupdated4Quarter 20152015, 2016none st Boulder CreekSubmitted to 1Quarter 20162015, 2016, Reduced by $250kin 2016 FEMA2017 Skunk, Bluebell, Anticipate to Initiate in 20162017,2018none submit early 2016 Upper Goose, TwomileAnticipate to Initiate in 20162017, 2018none submit early 2016 South Boulder CreekupdatedOn-going2018Added $15MBondin 2018 Fourmile -19 th to 22ndupdatedcompleted2015Bonding $2Min 2015, 2014 carry over funds revert to fund balance Fourmile upstream of updatedcompleted2016-2020Added $500k in 2021 th 19(Upland to Violet) Wonderland Foothills updatedcompleted2015Added $2.5M Bondin to Winding Trail2015 The September 2013 flood event identified the need for increased analysis and rehabilitation in the storm water drainage system. Additional funding was allocated in the 2015 budget process to supplement existing funding. The additional funding will be used to rehabilitate existing storm sewer infrastructure and to construct local drainage improvements projects throughout the city. The prioritization of these projects will be based on recommendations from the Stormwater Master Plan (SMP) Update, which will be completed in 2015. 2014Accomplishments 1.Significant flood recovery work was completed in 2014 including removing approximately 720 tons of debris and 46,000 cubic yards of sediment from the major draiangeways, in addition to repairing drop structures, areas of erosion and channel infrastructure. A survey and analysis of the damage to private properties from the September 2013 flood was conducted, as well as an analysis of the amount of rainfall and associated runoff for each major drainageway in order to estimate the flood recurrence interval. An analysis was also completed on the Fourmile Canyon Creek mapping to evaluate the spill flows to Wonderland Creek,based on the flood extents of the September 2013 flood. The analysis confirmed the effective mapping adopted in 2007 to be correct. 2.Flood mapping updates were reviewed and recommended for approval by WRAB and City Council and submitted to FEMA for Bear Canyon Creek (from Colorado Avenue to Agenda Item 6 Page 18 Boulder Creek) and Boulder Slough (Broadway to 30th Street). th 3.A Council Study Session was held on September 30to provide Council with agenda items including flood mapping and mitigation studies. An extensive Flood Management Overview was provided including maps and information about the cit major drainageways, flood regulations, and the floodplain mapping and mitigation process. The study session concluded with a presentation on the South Boulder Creek flood mitigation study for feedback from Council. 4.As a result of the additional 2015-2020 CIP funding, two new positions were budgeted in the Flood and Greenways work program (Utilities Planner and Flood and Greenways Project Manager). The Utilities Planner position was hired in July and the Flood and Greenways Project Manager position was hired in December. A Flood and Greenways Civil Engineer I was hired in December to fill a vacant GIS position. 5.In 2014 the City focused on the repair of existing storm sewers and expansion of existing storm sewers to address localized drainage issues. The City utilized contractors to repair or replace damaged storm sewers at 30th St & Colorado, Baseline Rd & 10th St, 4th St & Kalmia, 4th St & Juniper, 6th St & College Ave, Ithaca Dr & Wildwood Rd, Goose Creek along Edgewood Dr, Bear Creek at Wildwood Dr, and Two Mile Creek at Spring Valley Dr. A contractor also excavated the detention basins at the intersection of Foothills Hwy and Baseline Rd to restore their design capacity and establish a low-flow channel. Approximately 800 ft of storm sewer on 14th St from College Ave to Euclid Ave was also lined using cured in place pipe. Projects Completed or Anticipated for Completion in 2015 1.The Wonderland Creek - Foothills to Winding Trail project, which includes flood mitigation and a multi-use path connection is proposed to be bid in June and will have a two year construction schedule. This project is being funded by multiple sources including federal Transportation Improvement Program funds (TIP), the Urban Drainage and Flood Control District and the ci funding. Flood Utilities funding for the construction of these improvements will be bonded in 2015. 2.It is anticipated that the Upper Goose and Twomile Canyon Creek Mapping Update and Skunk Creek, King will be presented to City Council in July. 3.The Gregory Creek Mitigation Plan is expected to be taken to City Council for review and approval in the fall. 4.The Bear Canyon Creek and Boulder Creek Mitigation Plans are anticipated to be completed and presented to WRAB by the end of this year. Agenda Item 6 Page 19 5.Additional alternatives for detention at U.S. 36 for flood mitigation of South Boulder Creek are currently being evaluated to identify alternatives that have less environmental impact. These alternatives will be presented to the Open Space Board of Trustees and the WRAB in May and City Council in the summer or fall. 6.Utilities will complete an update to the 2007 Stormwater Master Plan (SMP) in 2015. The purpose of this update is address city-wide water quality issues, analyze underserved storm sewer infrastructure areas, and to incorporate the September 2013 flood inundation data. 7.Utilities staff will be inspecting 40,000 ft of storm sewers in the University Hill district as part of the storm sewer condition assessment program. Recent inspections of these sewers have confirmed that some sections are in a deteriorating condition. The inspection results will be used to define the scope of a storm sewer rehabilitation and replacement program which will begin in the fall of 2015. This program will utilize the 2015 Stormwater drainage Utility funding. Minor local drainage improvements to address citizen drainage complaints will also be implemented. Highlights of 2016-2021 Projects thnd 1.Improvements along Fourmile Canyon Creek, 19to 22Streets that include 100 year th flood mitigation at 19Street, a multi-use path and an emergency access connection from thth 19 Street to Tamarack Avenue and a bicycle and pedestrian underpass at 19 Street are expected to be bid in 2016.Carry over funds budgeted in previous years for this project will be returned to the fund balance for use on future projects in order to take advantage of favorable interest rates. Cash funding is shown for additional improvements along Fourmile Canyon Creek between Upland and Violet in outlying years. 2.Funding through bonding was increased from $10 to $25 million in 2018for construction of improvements along South Boulder Creek. 3.Funding continues to be shown for Bear Canyon Creek, Gregory Creek and Boulder Creek in 2016 and will be based on the recommendations of the mitigation planning studies. Funding in 2016 for Boulder Creek was reduced from $2.5 million to $2.25 million in order to maintain sufficient reserves in the fund financial. 4. Twomile and Upper Goose Creeks is shown starting in 2017 and will be based on the updated mapping and a mitigation planning effort. 5.Funding is also shown for the design and construction of localized drainage improvements throughout the city. These improvements include storm water collection and conveyance facilities designed to address the 2-year and 5-year storm events. Agenda Item 6 Page 20 BUDGET SUPPLEMENTAL REQUESTS, CHANGES Some additional needs have been identified subsequent to adoption of the 2015budget and are being proposed to City Council as budget adjustments. WRAB generally does not make a recommendation on mid-year budget adjustments and is not being asked to make a recommendation on these proposed changes. An additional $200,000 for a filter rehab project at the Betasso Water Treatment Plant. Performance issues were identified in filter #6 and problems with the filter underdrain system were discovered. Plant capacity is currently reduced by 15% with Filter 6 unavailable and failure of any of the other filters could strain the overall system ability to meet water demands during peak periods. And additional $595,000 is appropriated from additional grant revenue for re-routing a st portion of the 61Street interceptor pipe. The September 2013 flood exposed a vulnerable section of this pipe, and the City was awarded grant funds from the Colorado Department of Public Health and Environment for design and construction of re-routing. RATE STUDIES Staff are in the early stages of conducting a review of the Utility rate structures. It has been over nine years since comprehensive rate studies have been completed for the Water, Wastewater,or Stormwater/Food Utilities. The results of this rate study will inform any adjustments for 2017 budget development. BUDGET SCHEDULE: The current schedule of major budget milestones is provided below. Elements involving the WRAB are highlighted in bold italics. Milestone Date WRAB Preliminary Draft CIP Budget Discussion April 27, 2015 Budget Guidelines to Departments April 20,2015 WRAB Draft CIP Review May 18, 2015 Proposed Budget Submittal to City Manager May 29,2015 WRAB Recommendation on CIP/Budget June 22, 2015 Departmental Budget Review by City Manager May/June 2015 Planning Board Recommendation on CIP July 2014 City Council Study Session on CIP August 11,2015 City Council Study Session on Budget September 8and 22,2015 City Council Consideration/Adoption of Budget October 6and 20,2015 NEXT STEPS: Staff is seeking feedback on the preliminary draft CIP, updated financial information, and potential rate impacts. This feedback will be considered by staff in developing a draft CIP for WRAB discussion at the May 18, 2015meeting. At the June 22, 2015WRAB meeting, staff will request that WRAB provide a final recommendation concerning the proposed 2016-2021 CIP to Planning Board and City Council. Agenda Item 6 Page 21 Attachments: A: Preliminary 2016Fund FinancialsWater, Wastewater, Stormwater/Flood Management B : CIP Guiding Principles C: Colorado Utility Bill Comparison Water D: Colorado Utility Bill Comparison Wastewater E: Colorado Utility Bill Comparison Stormwater/Flood Management F: Colorado Utility Bill Comparison Combined Utilities G: Preliminary 2016-2021 CIP, Water, Wastewater, Stormwater/Flood Management H: Betasso 2016 Project Cost Estimates and Identified Alternatives Agenda Item 6 Page 22 Attachment B CIP Guiding Principles The City of Boulder develops a Capital Improvement Program (CIP) that addresses the ongoing major business needs and maintenance and repair of city assets as well as enhancements and expansion called for in the Boulder Valley Comprehensive Plan. The CIP is a strategic document that assures that the municipal organization maintains a strong bond rating, implements community values, and has fiscal integrity. The city prioritizes its investments both across and within funds based on the following guiding principles: 1. Capital Improvement Programs should be consistent with and implement Council accepted master plans and strategic plans. 2. Capital Improvements should achieve Community Sustainability Goals: Environmental sustainable materials, construction practices, renewable resources, etc. Social enhancements that improve accessibility to city services and resources provided to the community Economic effective and efficient use of public funds across the community. 3. As potential capital investments are identified, the city must demonstrate in the CIP process that there are sufficient funds to operate and maintain the project or program. 4. Capital Improvement Programs should provide enough capacity and flexibility in our long-term planning to be able to respond to emerging, unanticipated needs. 5. Capital Improvement Programs should maintain and enhance the supporting city-wide long term. 6. Capital Improvement Programs should sustain or improve maintenance of existing assets before investing in new assets. 7. Capital improvements should: Meet legal mandates from federal, state, or city levels Maintain or improve public safety and security Leverage external investments Promote community partnerships Reduce operating costs and improve efficiency. 8. Capital programming should maximize efficiency of investments demonstrated by measurable cost/benefit analyses and coordination of projects across departments within and across funds. 9. The Capital Improvement Program should provide sufficient reserves to allow for a sound fiscal foundation with benefits that include: A strong bond rating The ability to address emergencies and natural disasters. Page 1 Attachment G - DRAFT WATER CIP AHIJKLMNO 1 20-Apr-15CITY OF BOULDER 2 DRAFT 2016-2021 CAPITAL IMPROVEMENT PROGRAM 3 WATER UTILITY FUND 4 5 6 Assumed Inflation Rate20142015201620172018201920202021 7 PROJECT NAMEACTUALREVISEDPROJECTEDPROJECTEDPROJECTEDPROJECTEDPROJECTEDPROJECTED 8 9 Treated Water Pressure Reducing and Hydroelectric Facilities 10 Kohler Hydro/PRV Facility$0$50,000$0$0$0$0$0$0 11 Maxwell Hydro/PRV Facility$0$50,000$0$0$0$0$0$0 12 Orodell Hydro/PRV Facility$0$0$75,000$0$0$0$0$0 13 Sunshine Hydro/PRV Facility$0$0$0$271,875$0$0$0$0 14 Pearl Street Hydro/PRV Facility$0$0$0$0$24,333$243,331$0$0 15 Subtotal - Treated Water PRV and Hydro$0$100,000$75,000$271,875$24,333$243,331$0$0 16 17 Water Treatment Facilities 18 Betasso WTF$413,974$1,108,318$900,000$0$0$0$00 19 Betasso WTF - Bond Proceeds$0$0$24,000,000$0$0$0$0$0 20 Bond Issuance Costs$0$0$240,000$0$350,000$0$100,000$0 21 Boulder Reservoir WTF$203,296$7,100$164,000$0$0$0$2,000,000$0 22 Boulder Res WTF - Bond Proceeds$0$0$0$0$0$0$0$0 23 Subtotal - Water Treatment Facilities$617,270$1,115,418$25,304,000$0$350,000$0$2,100,000$0 24 25 Treated Water Pump Stations 26 Cherryvale Pump Station$0$0$0$0$0$0$0$0 27 Boulder Reservoir WTF High Service Pump Station$0$84,289$0$0$0$0$0$0 28 Iris Pump Stations$0$0$0$0$0$0$0$0 29 Subtotal - Treated Water Pump Stations$0$84,289$0$0$0$0$0$0 30 31 Treated Water Storage Tanks 32 Gunbarrel Storage Tank$644,449$39,746$0$0$0$0$0$0 33 Maxwell Storage Tank$0$0$0$0$0$0$0$0 34 Booten Storage Tank$0$0$0$0$0$0$0$0 35 Devil's Thumb Storage Tank$0$50,000$0$0$0$0$0$0 36 Kohler Storage Tank$64$103,487$799,875$0$0$0$0$0 37 Chautauqua Storage Tank$0$0$0$0$0$0$0$0 38 Betasso Storage Tank$0$0$0$292,465$0$0$0$0 39 Boulder Reservoir Storage Tank$0$0$0$0$0$0$0$0 40 Subtotal - Treated Water Storage Tanks$644,513$193,233$799,875$292,465$0$0$0$0 41 42 Treated Water Distribution System 43 Zone Isolation Valves$0$0$0$0$0$0$0$0 44 Cathodic Protection$0$0$0$0$0$0$0$0 45 Waterline Replacement$3,293,113$3,522,017$3,352,960$3,487,078($0)$3,771,624$3,922,489$4,079,389 46 Subtotal - Treated Water Distribution System$3,293,113$3,522,017$3,352,960$3,487,078($0)$3,771,624$3,922,489$4,079,389 47 48 Treated Water Transmission System 49 Sunshine Transmission Pipe$568,313$2,259,938$0$0$0$0$0$0 50 Boulder Canyon - Orodell to Fourmile Pipe$0$0$0$0$0$0$0$0 51 Mountain Transmission Pipes$0$0$0$0$0$0$0$0 52 Zone 1 Transmission Pipes$0$0$0$0$250,000$0$0$250,000 53 Zone 2 Transmission Pipes$0$0$0$250,000$0$0$250,000$0 54 Zone 3 Transmission Pipes$0$0$1,200,000$0$0$250,000$0$0 55 Subtotal - Treated Water Transmission System$568,313$2,259,938$1,200,000$250,000$250,000$250,000$250,000$250,000 56 57 Source Water Transmission System 58 Lakewood Pipeline$0$530,400$0$0$0$316,330$0$0 59 Silver Lake Pipeline $0$0$0$0$0$0$0$0 60 Source Water Transmission Pipe Inspections$0$73,653$0$0$0$0$0$0 61 Subtotal - Source Water Transmission System$0$604,053$0$0$0$316,330$0$0 62 63 Barker Water System 64 Barker Gravity Pipeline Repair$305,389$475,882$667,416$1,169,859$1,216,653$1,265,319$1,315,932$1,368,569 65 Barker-Kossler Penstock Repair$0$0$0$116,986$0$0$0$0 66 Barker Dam Outlet$00$100,000$175,000$0$835,551$0$0 67 Barker Dam Outlet - Bond Proceeds$0$0$0$0$0$0$8,355,509$0 68 Barker Dam and Reservoir$2,625$495,174$65,000$50,000$0$0$0$0 69 Barker Hydro System Integration$0$0$0$0$0$0$0$0 70 Barker Relicensing$25,377$0$0$0$0$0$0$0 71 Barker Instream Flow Release$0$6,052$0$0$0$0$0$0 72 Barker Residence$78,481$214,799$0$0$0$0$0 73 Betasso Penstock$0$0$0$0$0$0$0$0 74 Kossler Dam$56,204$135,738$75,000$0$0$0$0$0 75 Subtotal - Barker Water System$468,076$1,327,645$907,416$1,511,844$1,216,653$2,100,870$9,671,441$1,368,569 76 77 Raw Water Storage Reservoirs 78 Albion Dam$0$80,000$125,000$0$341,636$3,416,361$0$0 79 Silver Lake Dam$0$75,000$0$0$100,000$0$0$0 80 Island Lake Dam$0$0$0$0$50,000$0$0$0 81 Green Lake 1 Dam$0$0$0$0$0$0$0$0 82 Green Lake 2 Dam - Bond Proceeds$0$0$0$0$0$0$0$0 83 Green Lake 2 Dam $0$24,719$0$0$0$0$75,000$486,773 84 Green Lake 3 Dam$0$0$0$0$0$0$0$0 85 Goose Lake Dam$0$20,000$0$0$75,000$0$0$0 86 Boulder Reservoir$0$0$50,000$0$0$0$118,434$0 DRAFT WATER CIP Attachment G - DRAFT WATER CIP AHIJKLMNO 1 20-Apr-15CITY OF BOULDER 2 DRAFT 2016-2021 CAPITAL IMPROVEMENT PROGRAM 3 WATER UTILITY FUND 4 5 6 Assumed Inflation Rate20142015201620172018201920202021 7 PROJECT NAMEACTUALREVISEDPROJECTEDPROJECTEDPROJECTEDPROJECTEDPROJECTEDPROJECTED 8 87 Lakewood Dam$0$0$0$0$124,707$0$0$0 88 Skyscraper Dam$0$0$0$0$0$0$0$171,071 89 Wittemyer Ponds$0$0$0$0$0$100,000$492,685$4,926,849 90 Subtotal - Raw Water Storage Reservoirs$0$199,719$175,000$0$691,343$3,516,361$686,119$5,584,692 91 92 Other Raw Water Facilities 93 Farmer's Ditch$0$0$0$0$0$108,160$0$0 94 Anderson Ditch$0$0$0$0$0$0$0$0 95 Source Water Facilities Rehab Program$150,000$150,000$150,000$150,000$150,000$150,000 96 Watershed Improvements$78,886$146,357$80,000$0$0$0$100,000$0 97 Nederland WWTP$0$0$0$0$0$0$0$0 98 Instream Flow Structures and Gaging$0$48,428$0$0$0$0$0$0 99 Como Creek Diversion Structure $0$0$0$0$0$0$0$0 100 Lakewood Diversion Structure $0$0$0$0$0$0$0$0 101 Silver Lake Diversion Structure$0$0$0$0$0$0$0$0 102 NCWCD Conveyance - Boulder Feeder Canal$25$61,271$0$0$0$0$0$0 103 NCWCD Conveyance - Carter Lake Pipeline$250,000$500,000$850,000$2,036,322$0$0$0$0 104 NCWCD Conveyance/Waterline replacement - Bond Proceeds$0$0$0$0$37,565,263$0$0$0 105 Subtotal - Other Raw Water Facilities$328,910$756,056$1,080,000$2,186,322$37,715,263$258,160$250,000$150,000 106 107 Source Water Pressure Reducing, Pumping and Hydroelectric 108 Lakewood Hydroelectric/PRV$0$0$130,000$0$0$300,000$0$0 109 Silver Lake Hydroelectric/PRV$0$150,000$25,000$50,000$80,000$0$0$0 110 Boulder Reservoir Intake and Pumping$0$0$0$0$0$0$0$0 111 Betasso Hydroelectric / Pressure Reducing Facility$134,404$0$0$380,000$480,000$0$0$0 112 Barker Dam Hydroelectric$0$00$0$0$0$0$0 113 Barker Dam Hydro$0$0$0$0$0$0$0$0 114 Boulder Canyon Hydroelectric$100,755$33,641$0$0$0$0$0$0 115 Boulder Canyon Hydro - Grant$0$0$0$0$0$0$0$0 116 Boulder Canyon Hydro - Grant$0$0$0$0$0$0$0$0 117 Carter Lake Hydroelectric$0$0$0$0$50,000$250,000$0$0 118 Carter Lake Hydro$0$0$0$0$0$0$2,500,000$0 119 Source Water Pressure Reducing, Pumping and Hydroelectric Facility Rehabilitation$0$0$0$0$0$0$193,472$201,210 120 Subtotal - Source Water PRV, Pumping and Hydro$235,159$183,641$155,000$430,000$610,000$550,000$2,693,472$201,210 121 122 Water Distribution System Expansion 123 Annexation Related Water System Expansion$0$2,551,700$2,500,000$0$0$0$0$0 124 Subtotal - Water Distribution System Expansion$0$2,551,700$2,500,000$0$0$0$0$0 125 126 Water System Monitoring and Metering 127 Automated Meter Reading$0$0$0$0$0$0$0$684,285 128 Water System Security/Quality Improvements$13,996$150,000$150,000$150,000$150,000$90,000$0$0 129 Source Water Monitoring and Protection$0$100,000$100,000$100,000$100,000$100,000$0$0 130 Distribution System Water Quality$14,100$0$0$0$0$0$0$0 131 Data Communications System$0$0$0$0$0$0$0$0 132 September 2013 Flood Disaster Recovery$860,072$304,301$0$0$0$0$0$0 133 Yards Master Plan Implementation$13,553$86,321$0$0$0$0$0$0 134 Utility Billing Computer System$0$100,000$0$0$0$0$125,000$0 135 Subtotal - Water System Monitoring and Metering$901,722$740,622$250,000$250,000$250,000$190,000$125,000$684,285 136 137 TOTAL CAPITAL USES OF FUNDS$7,057,076$13,638,331$35,799,251$8,679,585$41,107,591$11,196,676$19,698,520$12,318,145 DRAFT WATER CIP Attachment G - DRAFT WASTEWATER CIP AHIJKLMNO 1 20-Apr-15CITY OF BOULDER 2 DRAFT 2016 - 2021 CAPITAL IMPROVEMENT PROGRAM 3 WASTEWATER UTILITY FUND 4 5 6 Assumed Inflation Rate20142015201620172018201920202021 7 PROJECT NAMEACTUALREVISEDPROJECTEDPROJECTEDPROJECTEDPROJECTEDPROJECTEDPROJECTED 8 9 Wastewater Treatment 10 WWTF Pumps$0$0$150,000$0$0$0$0$0 11 WWTF Permit Improvements$438,080$4,194,112$150,000$0$750,000$1,500,000$0$136,857 12 WWTF Nutrient Management Grant$144,485 13 WWTF Permit Improvements - Proj. Bond$0$0$0$0$0$0$18,500,000$0 14 WWTF Laboratory$25,163$0$50,000$0$0$0$0$0 15 Lower Boulder Creek Enhancement$0$0$0$0$0$0$0$0 16 WWTF Headworks$0$0$0$0$0$0$0$0 17 WWTF Headworks - Proj. Bond$0$0$0$0$0$0$0$0 18 WWTF Instrumentation/Control$0$1,127,477$0$674,918$701,915$729,992$759,191$0 19 WWTF Electrical$0$0$120,000$1,200,000$0$0$0$0 20 WWTF Activated Sludge$0$389,376$0$58,493$0$0$0$0 21 WWTF Primary Clarifiers$0$0$0$0$0$0$0$0 22 WWTF Secondary Clarifiers$0$0$0$0$0$0$0$0 23 WWTF UV Disinfection$2,356$2,998$0$0$0$0$0$0 24 WWTF UV Disinfection - Proj. Bond$0$0$0$0$0$0$0$0 25 WWTF Permit Improvements - 2010 Bond$15,148$1,198$0$0$0$0$0$0 26 WWTF Rehabilitation$0$0$0$0$0$0$150,000$375,000 27 Valmont Butte$0$0$0$0$0$0$0$0 28 Biosolids Processing & Dewatering$110,044$0$0$0$0$0$0$0 29 WWTF Biosolids Digester$20,000$0$0$0$0$0$0$0 30 WWTF Biosolids Digester - Proj. Bond$0$0$0$0$0$0$0$0 31 WWTF Cogeneration$0$39,995$0$0$0$0$184,481$0 32 WWTF Digester Complex$0$0$0$0$0$200,000$2,000,000$0 33 September 2013 Flood Disaster Recovery$453,442$606,987$0$0$0$0$0$0 34 WWTF Digester Cleaning$0$0$0$0$0$0$0$0 35 Bond Issuance Costs$0$125,000$0$0$0$0$125,000$0 36 Subtotal - Wastewater Treatment Plant$1,208,718$6,487,143$470,000$1,933,411$1,451,915$2,429,992$21,718,672$511,857 37 38 Marshall Landfill 39 Marshall Landfill$0$0$100,000$0$0$0$0$0 40 Subtotal - Marshall Landfill$0$0$100,000$0$0$0$0$0 41 42 Wastewater System Monitoring and Metering 43 Yards Master Plan Implementation$6,777$36,046$0$0$0$0$0$0 44 Automated Meter Reading$0$0$0$0$0$0$0$0 45 Utility Billing Computer System$0$50,000$0$0$0$0$65,000$0 46 Subtotal - Monitoring and Metering$6,777$86,046$0$0$0$0$65,000$0 47 48 Collection and Conveyance System Rehabilitation 49 Collection System Monitoring$338,636$3,426$0$0$0$0$0$0 50 Condition Assessment Program$780,000$811,200$843,648$877,394$912,490$948,989$986,949 51 Sanitary Sewer Rehabilitation$403,808$3,000,161$2,758,080$2,868,403$2,983,139$3,102,465$3,226,563$3,355,626 52 Sanitary Sewer Rehabilitation - Bond - 10,000,000 - - - - - - 53 Sanitary Sewer Manhole Rehabilitation$51,186$208,000$216,320$224,973$233,972$243,331$253,064$657,966 54 IBM Pump Station$79,395$1,235,402$0$0$0$0$0$0 55 Tier 1 Boulder Creek 2 Master Plan Project$0$0$0$0$0$0$0$0 56 Tier 1 Goose Creek 1/1A Master Plan Project$0$0$0$0$0$0$0$329,278 57 Tier 1 Goose Creek 3 Master Plan Project$0$0$0$0$0$0$0$0 58 Tier 1 Goose Creek 5 Master Plan Project$0$0$0$0$25,000$647,590$1,346,988$1,400,867 59 Tier 2 Boulder Creek 1 Master Plan Project$0$0$0$0$0$0$0$0 60 Tier 2 Boulder Creek 3 Master Plan Project$0$0$0$0$0$0$0$0 61 Tier 2 Boulder Creek 4 Master Plan Project$0$0$0$0$0$0$0$0 62 Tier 2 Goose Creek 4 Master Plan Project$0$0$0$0$0$0$0$0 63 Tier 2 Gunbarrel 1 Master Plan Project$0$0$0$0$0$0$0$0 64 Tier 2 Gunbarrel 2 Master Plan Project$0$0$0$0$0$0$0$0 65 Tier 2 South Boulder Creek 1 Master Plan Project$0$0$0$0$0$0$0$0 66 Subtotal - Sewer System Rehabilitation$873,024$15,226,990$3,785,600$3,937,024$4,119,505$4,905,875$5,775,604$6,730,686 67 68 Wastewater System Expansion 69 Annexation Related WW System Expansion$0$0$0$0$0$0$0$0 70 Subtotal - Wastewater System Expansion$0$0$0$0$0$0$0$0 71 72 TOTAL CAPITAL USES OF FUNDS$2,088,519$21,800,178$4,355,600$5,870,435$5,571,420$7,335,867$27,559,277$7,242,543 DRAFT WASTEWATER CIP Attachment H City of Boulder | BWTF CIP Preliminary Phase 1 Project Descriptions and Cost Estimates Memo Wednesday, April 08, 2015 Date: Project:Capital Improvements Preliminary Design Project Betasso Water Treatment Facility Steve Buckbee, P.E., Utilities Project Manager To: Tom Settle, Water Treatment Coordinator From: Gary Fuller, P.E., Brian Daw, P.E. and Jenn Stillman P.E. Preliminary Phase 1 Project Descriptions and Cost Estimates Subject: Introduction In September 2014, the City of Boulder Utilities Division (the City) initiated the Betasso Water Treatment Facility (BWTF) Capital Improvements Project (Project) with the primary objectives of: Identifying improvements required to achieve a 40 million gallon per day (mgd) treatment capacity at the BWTF Developing a 20-year Capital Improvement Plan (CIP) for the BWTF Prioritizing asset repair and replacement at the BWTF Identifying Phase 1 improvements for implementation in 2016-2017, and Completing preliminary design of the proposed Phase 1 improvements Table 1 outlines the Project’s major tasks and the scheduled completion of each milestone. The project team is currently working on Task 500 – Capital Improvement & Implementation Plan which will result in a CIP report outlining proposed improvements for the BWTF over the next twenty years. Table 1. Summary of Project Tasks Task Description Status Task 100 Project Coordination In progress Task 200 Data Collection & Review October 2014 Task 300 Facility Assessment January 2015 Task 400 Alternatives Analysis March 2015 Task 500 Capital Improvement & Implementation Plan In progress – Apr 2015 Task 600 Preliminary Design of Phase 1 Improvements June 2015 hdrinc.com 1670 Broadway, Suite 3400, Denver, CO 80202-4824 (303) 764-1520 1 Attachment H City of Boulder | BWTF CIP Preliminary Phase 1 Project Descriptions and Cost Estimates This memorandum provides general descriptions of the major CIP projects proposed for the Phase 1 improvements and a summary of the preliminary cost estimates. CIP Project Descriptions A workshop was conducted with City staff on March 31, 2015 to review CIP project descriptions and recommendations for prioritizing the projects. Based on results of the discussions during the workshop, the project team developed a proposed list of projects to be implemented in the Phase 1 improvements at the BWTF. The proposed improvements consist of the seven (7) major projects listed below: Pretreatment Basin Improvements Pretreatment Building Addition Filter Improvements Filter Valve Replacement Improvements Residuals Handling Improvements Power Reconfiguration Improvements Outdoor Tanks Improvements In addition to the major projects listed above, a number of miscellaneous projects were also identified for Phase 1 implementation. These miscellaneous projects are referred to as the “balance of Phase 1 projects” and are organized by facility area. Pretreatment Improvements Project The pretreatment system at the BWTF consists of rapid mix, flocculation, and sedimentation. The entire pretreatment process will be upgraded to enhance the BWTF’s treatment capacity. New pretreatment trains will be constructed using existing Sedimentation Basin Nos. 2 and 3 by installing new concrete walls and floor slabs within the basins, with a new center wall dividing each basin into two separate sedimentation basins. Plate settlers will be installed into each basin resulting in four new high-rate sedimentation basins with each basin rated at 10 million gallons per day (mgd). Rapid mix chambers will be constructed for each pair of basins, with new three-stage flocculation zones installed in each basin. New sludge collector systems will be installed below the plate settlers to remove settled solids. Access walkways with handrail will be installed above the treatment basins for mounting flocculator motor drives and providing access for operation and maintenance. Existing basin influent and effluent piping and valves will be reconfigured to distribute raw to and settled water from the basins. Pretreatment Building Addition Project A building enclosure is proposed to be constructed above the new pretreatment basins. The proposed building footprint will only cover the plate settler zone with the rapid mix chambers and flocculation zones remaining open to the environment. The building enclosure would prevent the formation of ice on the surface of the water in the vicinity of the plate settlers and would also provide safe access to the plate settlers for cleaning during inclement weather. The new building will match the architectural style of the existing site architecture and consist of masonry walls, concrete double tee roof, skylights and windows for natural lighting, interior lighting, and 2 Attachment H City of Boulder | BWTF CIP Preliminary Phase 1 Project Descriptions and Cost Estimates access doors. The project team will also evaluate the cost impact of using alternative building materials to enclose the entire pretreatment basins. Furthermore, the team is also considering layouts that will connect the existing filter building and provide covered access to the DAF building along with the new residuals handling building. Filter Improvements Project The BWTF’s eight gravity filters were constructed in two phases – four with the initial construction of the facility in 1962 and four during capacity improvements in 1976. The underdrains in the second generation of filters, Filter Nos. 5 through 8, are in good condition and suitable for continued service based on observed filter performance and investigation of Filter No. 6 completed in October 2014. The underdrains in the first generation of filters, Filters Nos. 1 through 4, are also assumed to be in good condition and will be further assessed in the fall of 2015. Under this premise, the filter improvements project will mainly consist of modifications that will extend their service life and maintain their treatment capability. The modifications consist of: Applying new protective concrete coatings to the filter walls and troughs to repair concrete deterioration and prevent further damage from low alkalinity water Replacing filter media including gravel, sand, and anthracite Replacing the surface wash arms and piping inside the filters Adding weir plates to the concrete backwash troughs At some point in the future, the existing clay tile underdrains will need to be replaced in all of the BWTF filters and are recommended to be converted to gravel-less design with air scour with new backwash troughs. The future work will be included in the 20-year CIP planning for the BWTF. Filter Valve Replacement Project The BWTF’s Pipe Gallery contains a number of process valves and actuators that have reached the end of their service lives and are no longer providing the level of reliability required for the BWTF treatment process. The process valves and actuators that will be replaced are largely comprised of butterfly type valves with piston type pneumatic actuators used for operating the filters. Approximately fifty (50) valves ranging in size from 6 inch to 36 inch are proposed to be replaced. New pneumatic actuators will be provided for all valves providing open/close service and electric actuators will be provided for all valves providing modulating service. The compressed air system used to operate the pneumatic valves has also reached the end of its service life and will be replaced in its entirety including new air compressors, receiving tanks, air dryers, and compressed air piping. Residuals Handling Project The residuals handling strategy at the BWTF has evolved from the initial objective of thickening residuals (sludge) to an emphasis on dewatering residuals for hauling and disposal. The change in approach is primarily due to considerations for implementing dewatering at the site in the future and the recent consolidation of two of the City’s liquid waste hauling contractors and the subsequent increases to hauling and disposal costs. The project team is currently refining 3 Attachment H City of Boulder | BWTF CIP Preliminary Phase 1 Project Descriptions and Cost Estimates the scope of the residuals handling project to include consideration of type of mechanical dewatering equipment, its location, onsite drying and storage options, and ultimate disposal. For the purposes of the preliminary cost estimate, the conceptual design of the residuals handling system is based on a new combination gravity belt thickener (GBT)/ belt filter press (BFP) installed in a new building located adjacent to the SBE Basin. The GBT/BFP can thicken sludge prior to routing to the lagoons/drying beds, or dewater residuals that can be hauled offsite for disposal. The new residuals building is assumed to be masonry construction with the following provisions: A combined GBT/BFP unit A buried equalization tank to receive underflow from the pretreatment basins An interior parking bay for a roll-off container or end-dump trailer for hauling dewatered residuals Storage areas for ancillary equipment, i.e. polymer mixing and feed systems, sludge pumps, etc. Transfer piping to the existing drying beds and lagoons to provide a backup discharge location to allow for operating the GBT portion of the unit (i.e. thickening only and not dewatering) or direct discharge to the lagoons Power Reconfiuration Project g One of the primary recommendations resulting from the project’s Facility Assessment is to reconfigure the overall power distribution system for the BWTF to eliminate equipment past the end of its useful life and to increase the reliability of the overall facility. The power reconfiguration project will consist of the following modifications: Remove electrical equipment that is at the end of its service life Use the DAF switchgear as the primary plant electrical distribution point, with radial feeders to motor control centers (MCCs) distributed through the facility Modify feeders to some MCCs to reduce “daisy-chain” power feeds and improve reliability and maintainability Provide a new diesel generator with capacity to power the entire facility Provide for a future means to deliver power from the hydropower plant into the water plant electrical distribution system Outdoor Tanks Improvements Project The BWTF site has a number of large outdoor above-grade steel tanks. Three of the tanks are in need of repairs including the two clearwells and the Wash Water Tank. The scope of outdoor tank improvements consists of the following: Sand blast and paint exterior of Clearwell No. 1 Sand blast and paint interior and exterior of Clearwell No. 2 Sand blast and paint exterior of Wash Water Tank Replace up to 20 percent of the steel roof rafters in Clearwell No. 2 4 Attachment H City of Boulder | BWTF CIP Preliminary Phase 1 Project Descriptions and Cost Estimates Cost Estimates Table 2 summarizes the cost estimates for the proposed Phase 1 improvements. The estimates are organized into two categories, which are the major Phase 1 projects and the balance of Phase 1 projects (organized by facility area). The preliminary prioritization for the major Phase 1 projects is reflected in the table below in descending order. The estimated construction cost of the major Phase 1 projects is $20.9 million with the balance of Phase 1 projects estimated at $1.5 million. The total estimated construction cost for the Phase 1 improvements is $22.4 million. Estimates only reflect capital costs and do not currently reflect the City’s administrative, legal, engineering design, and construction administration costs that should be considered in developing total project costs. Table 2. CIP Prioritization Summary Prioritized Phase 1 Projects Estimated Cost Pretreatment Basin Improvements $ 10,508,000 Filter Improvements $ 1,562,000 Power Reconfiguration Improvements $ 2,500,000 Residuals Handling Improvements $ 2,500,000 Outdoor Tanks Improvements $ 800,000 Filter Valve Replacement Improvements $ 1,660,000 Pretreatment Building Addition $ 1,406,000 Total$ 20,936,000 Balance of Phase 1 Projects by Estimated Cost Facility Area General $ 100,000 Chemical Building $ 64,000 DAF Building $ - Filter Room $ 396,000 Floc/Sed Basins $ - Operation and Maintenance $ 68,600 Outdoor Equipment $ - Outdoor Tanks $ - Pipe Gallery $ 485,400 Pump Building $ - Site Civil $ 385,000 Total $ 1,499,000 5 INFORMATION PACKET MEMORANDUM To: Water Resources Advisory Board From: Jeff Arthur, Director of Public Works for Utilities Annie Noble, Acting Principal for Flood and Greenways Ward Bauscher, Engineering Project Manager Kristin Dean, Utilities Planner Christin Shepherd, Flood and Greenways Engineer Date: April 27, 2015 Subject: Information Item: Bear Canyon Creek Flood Mitigation Plan EXECUTIVE SUMMARY: Bear Canyon Creek currently has no adopted master flood mitigation plan. Although much of the drainage has been significantly improved to convey 100-year flood flows, the 2013 flood event raised performance concerns about areas in the drainage way. The Flood Management and Greenways group, as part of a comprehensive mitigation study, initiated the Bear Canyon Creek Mitigation Plan in 2014. The purpose of this memorandum is to update WRAB on the mitigation plan progress and describe the overall study approach. This study focuses on three distinct areas based on performance concerns during the 2013 flooding event: Reach 1: City Limits to Lehigh Street Reach 2: Lehigh Street to Broadway Reach 3: Moorhead Avenue to Baseline Road Bear Canyon Creek Informational Memo 1 The city retained AMEC Foster Wheeler (AMEC) in December 2014 to help identify mitigation needs and evaluate potential alternatives to alleviate future flooding along Bear Canyon Creek in the selected stream reaches. Bear Canyon Creek Informational Memo 2 The study will be comprised of 3 phases with distinct goals. Phase 1 : consists of creating baseline hydraulic and loss models to help identify problem areas and inform mitigation alternative choices for consideration. Mitigation alternatives will be broadly identified. Phase 1 summary memos from the consultant are attached and summarized within. Phase 2 : utilizes the baseline models created in Phase1. Alternatives will be analyzed and incorporated into the models to determine their benefit. A Cost- Benefit analysis will be performed to help rank the feasibility of alternatives. (Information item and presentation to WRAB scheduled for August 2015) Phase 3 : refines the alternative measures. The recommended alternatives will be compiled as a recommended Flood Mitigation Plan. This plan will be presented to WRAB with a request for a recommendation to City Council. (Action item November 2015) The Phase 1 (Draft) Flood Mitigation Master Plan for Bear Canyon Creek Conceptual Attachment A Alternative Development memo . This is analysis describing existing conditions and considerations for the preliminary alternative recommendations. Additionally, AMEC has provided a memo describing their baseline model for the study area. This memo entitled Phase 1: Flood Loss Attachment B Estimation Technical Memorandum is attached as . BOARD AND COMMISSION FEEDBACK The Bear Canyon Creek Mitigation Plan is in the preliminary phase and has had no board or commission feedback. PUBLIC FEEDBACK An Open House was held on July 1, 2014 to introduce this mitigation plan. Approximately 45 people attended this meeting, where the initial study parameters and th extents were discussed. Additionally, another open house is scheduled for April 27, 2015 directly prior to the WRAB meeting. Poster boards will be presented for discussion, outlining the study reaches and potential mitigation options. Public notification post cards about this WRAB meeting and the preceding Open House were sent to all property owners in the study area and a project web site has been developed to provide information and receive comments, with 24 comments received via the website comment tool to date ( https://bouldercolorado.gov/flood/bear-canyon-creek- Additionally, posters notifying the neighborhood of the meeting flood-mitigation-project). and open house were posted at various visible locations along the creek. Emails have been sent to all interested parties who have signed up for email notifications and to all parents of children attending Bear Creek Elementary School. BACKGROUND Bear Canyon Creek Informational Memo 3 Bear Canyon Creek originates in City of Boulder Open Space and has a drainage area of 5.3 square miles. The creek is 6.3 miles long. Much of the Bear Canyon Creek basin within the Boulder City limits and early 1960s. Channel infrastructure along Bear Canyon Creek has been thth overwhelmed during flood events on May 7 1969, May 1995, August 15 2007 and September 2013, among others. Since the initial development, this major drainage way has undergone numerous improvements and benefits from a formal maintenance plan, however the flooding of September 2013 brought to light some key issues which contributed to property damage and safety concerns. In general, problems stemmed from poor conveyance capabilities, debris blockage at major crossings and lack of effective flow return zones. Much of the Bear Canyon Creek ecosystem consists of non-native species that do not do well during extreme flood events in the foothills. These species create large amounts of debris as compared to more native species and this debris can be transported downstream creating blockages to flow. Although the channel is relatively stable during normal flows, unstable channel conditions contribute to the generation and transport of sediment during extreme events. In the upper reaches of Bear Canyon Creek, a steeper channel gradient encourages sediment transport. The sediment typically deposits at culverts or shallower sections, reducing their capacity. During the 2013 flood, sediment deposition blocked many of the culverts completely and caused flows through surrounding neighborhoods and streets. This study focuses on 3 distinct areas better described below. Reach 1 The reach is defined from the City Limits to Lehigh Street and consists of City Open Space, medium density suburban, and high density townhome use. Major constrictions occur at Wildwood Road, a pedestrian bridge connecting Bear Creek Elementary school to Bear Mountain Drive, and an old boiler tank (as a culvert) crossing the stream at Wildwood and Ithaca. Although the regulatory floodplain is narrow in this area, Reach 1 had significant flooding and property damage during the September 2013 flood. Much of the damage was caused by flows created as the channel dammed with debris. Locations with potential for debris mitigation, floodplain storage and stream stabilization requirements will be identified. Reach 2 Reach 2 is divided into two sections, Reach 2A and Reach 2B. Reach 2A extends from the crossing at Lehigh to the crossing at Broadway, while reach 2B extends from Broadway to Moorhead Avenue. Although the mitigation study will only examine alternatives in Reach 2A, Reach 2B is included because it will benefit from the upstream mitigation measures and should be included in the benefit cost analysis. Reach 2A is an urban transportation zone, with the floodplain mainly confined to Table Mesa Drive and the creek situated within the parkway. The stream channel is designed to Bear Canyon Creek Informational Memo 4 contain the 25-year event with drop structures and crossings sized for stability and conveyance, while the Parkway itself forms the floodplain. Residential structures would be minimally impacted by flooding, however, commercial properties at the downstream limits of the reach are susceptible to damage in larger events. The Harvard lane culvert in particular has insufficient capacity to pass flood flows, especially with debris blockage, which causes spill flows downstream in Reach 2B, where substantial damage results. Reach 2B passes through Martin Park and a small residential area until it reaches Moorhead. This area has 100-year flood mitigation improvements that were constructed in the 1980s and 1990s, but saw damages during the 2013 flood event from spill flows at the Harvard Lane culvert. It became clear that this area (Martin Acres), which was previously excluded from the scope, needed to be included as improvements in reach 2A could benefit this area. Reach 3 Reach 3 is also separated into a study reach, Reach 3A and an impacted reach, Reach 3B. Reach 3B sees diverted flows originating from Reach 3A. Reach 3A begins at US Highway 36 and extends through the University of Colorado Williams Village Campus to Baseline Road. This reach is currently undeveloped except for the lower limits, and consists of disturbed land and low flow crossings. The channel has insufficient capacity for any flows above the 2 year event, and is overgrown with invasive species. Poor outlet conditions at the US Highway 36 culvert exacerbate flooding upstream and create a spill situation across highway 36 in extreme events. The private drive of St. Andrews Presbyterian Church at the downstream limits of the reach just upstream of Baseline Rd., contributes to spills across Baseline Rd, severely limiting the effectiveness of the Bear Canyon Creek culvert under Baseline Rd. This church location demarks the northern end of the study area for this mitigation plan. Reach 3B begins at Baseline Road and continues to Mohawk Drive. It was included for cost benefit analysis only. The remainder of the drainage has had significant improvements up to the confluence of Bear Canyon Creek and Boulder Creek which occurs just to the north of Arapahoe Rd. and east of Foothills Parkway. Bear Canyon Creek Informational Memo 5 ANALYSIS Typically, flood mitigation plans are developed with the intent to adequately convey a 100-year storm event. Designing major drainage way systems to transport the 100-year event is a policy standard included in the Boulder Valley Comprehensive Plan, the Comprehensive Flood and Stormwater Utility Master Plan and the UDFCD Drainage Criteria Manual and is applicable to new development in the city. Due to the existing residential development and previous channel mitigation in several reaches of the creek, this mitigation planning effort covers only 3 specific sections of the drainage, Reaches 1, 2, and 3 which were described in detail in the Background section of this memo. To understand the full implications of mitigation alternatives, three steps were taken to provide the analysis for Bear Canyon Creek Mitigation Plan - Phase 1: 1.A baseline conditions model was created, 2.The potential property damage during a 100-year storm event in the baseline conditions model were analyzed, and 3.Mitigation improvements were identified based on this baseline model and observations from the 2013 flood event. These mitigation alternatives will be modeled and analyzed in Phase 2 of the study. Bear Canyon Creek Informational Memo 6 Development of the Baseline Conditions Model Best Available Information Model In order to accurately analyze flows and potential improvements in the area of Bear Canyon Creek, a complete hydraulic model needed to be created. In April of 1985, a Flood Insurance Study (FIS) was conducted that produced detailed hydrologic and hydraulic information for the City of Boulder and its vicinity. In May of 1987, and delineated flood hazard areas for Bear Canyon Creek. These reports did not result in a complete hydraulic model for the entire stretch of Bear Creek (from City Limits to its confluence with Boulder Creek). Segments of Bear Canyon Creek had been analyzed and smaller hydraulic models developed for each area but they did not seamlessly connect as one cohesive model. In order to fully analyze the potential mitigation efforts along this major drainage way, a complete HEC-RAS model of the entire stream was needed. The City and the Urban Drainage and Flood Control District (UDFCD) transferred all available modeling data to AMEC who developed a Best Available Information model to produce the 10-year flood (10% annual chance), 50-year flood (2% annual chance), 100-year flood (1% annual chance), and 500-year flood (0.2% annual chance) events under existing conditions as a baseline model. UDFCD has informed the city that, when no complete model exists, a Best Available Information model is acceptable to use for planning and mitigation purposes. Potential Damages Incurred During 100-year Flood Event in Baseline Model Hazus--based natural hazard property damage estimation tool, was initially used to perform a flood loss estimation within the three study reaches. Site- specific building information for each of the study areas was provided by the FEMA Region VIII via the City. This data required some coordination to accurately represent on the ground scenarios. The second input into the model was a depth grid, which is a grid-based GIS file that indicates the depth of flooding at a particular grid cell. Flood depth grid data provided by FEMA was limited to the effective 100 year (1% annual chance) return period. The building data was formatted and imported into the Hazus regions for loss analysis using the 100-year FEMA depth grid. The building point layer was overlaid onto each depth grid in GIS and a spatial join was performed to determine the depth of flooding at each structure for each return period. The tabular database was incorporated into the modified Benefit Cost Analysis (BCA) spreadsheet to perform the property damage loss calculations. Per FEMA guidance, loss curves from the Army Corps of Engineers were used during this analysis. Each reach has been modeled for the 2-, 10-, 50-, 100- and 500-year event. Reaches 2 and 3 have risk to losses during the 100 and all reaches have losses during a 500-year event but only reach 3 has risk during the 50 year event. Reach 1 has the lowest risk to flooding of the 3 reaches and does not result in flood loss from the 100-year event. The 500-year event affects 35 residential structures, with a total damage of $1.1M. While there is no modeled risk during the more frequent interval Bear Canyon Creek Informational Memo 7 floods, it should be noted that debris and culvert blockage during the 2013 flood (estimated to be a 25 year event) caused flooding in the 500-year floodplain in this reach. Reaches 2A and 2B have the most buildings of the three reaches, including the most commercial structures. The commercial structures are associated with the Table Mesa Shopping Center at the intersection of Table Mesa and Broadway. Reaches 2A and 2B have the greatest risk from the 100 and 500-year floods. The majority of this damage is associated with reach 2B east of Broadway. The 100-year flood analysis results in less than $400k in damages between Lehigh and Broadway in reach 2A, and $1.1M associated with the 500 year event. When losses in the 2B reach are included, estimated losses are closer to $5.5M and $8.5M for the 100 and 500-year events respectively. Reaches 3A and 3B have 213 residential structures, and several religious institutions at risk to flooding. This reach is the only reach to have some risk to the more frequent 50- year flood event (8 structures total). Reach 3A has substantial risk to the 500-year flood event. Total estimated damages across all study reaches for the theoretical 50 year flood event is estimated at $335,000; the 100- year and 500-year total estimated damages are $6.9M and $18.7M respectively. Proposed Improvements and Their Affect on Potential Losses The purpose of this analysis was to explore mitigation strategies aimed at reducing damage from flood events and to create a with mitigation alternatives analysis in Phase 2 of the study These alternatives fall into three categories: non-structural measures, structural improvements, and debris management. Non-structural alternatives: These will target vegetation management and maintenance. The riparian zone will be evaluated for vegetative debris production, transport and control. Structural alternatives: These will consist of stream restoration strategies, floodplain creation or modification and capacity improvements to stream crossings. The feasibility of debris control structure solutions will be evaluated as well as improvements to pedestrian crossings. Debris management: Sediment and debris catchment areas will be evaluated for storage potential, location relative to downstream crossings and maintenance access. Reach 1 Vegetation management and debris control are crucial to improving the capacity of the channel. Invasive species should be controlled and the channel stabilized to reduce channel degradation. Several opportunities exist for debris mitigation, including areas immediately upstream of Wildwood and Lehigh. Another opportunity exists for a larger area immediately adjacent to the Bear Creek Elementary School within the Bear Creek Bear Canyon Creek Informational Memo 8 Park. These areas could be graded to receive debris deflected into them with strategically placed rock structures in the stream, and maintenance access provided to remove the accumulated debris periodically. The area immediately adjacent to Wildwood above Ithaca is currently degraded and full of invasive species, both willow and elm trees. This area could be re-graded to connect the floodplain and be stabilized with non-structural treatments such as root wads and faschines (bundles of straw staked with native willow and seeded with a riparian seed mix). The area could then be replanted and managed as a riparian corridor per the Greenways Master Plan. The Wildwood culvert should be assessed for improvements to hydraulics and debris control. These improvements may consist of maintenance near the up and downstream face of the structure for sediment and vegetation, modifications to the structure including beveling of the top section, placing fins or a debris deflector in front of the entrance or increasing the cell size or number. The pedestrian bridge (shown in the attached map as CR-R1-2) was replaced after the 2013 flood, however, the channel approaches up and downstream are severely incised and should be stabilized. The old boiler section culvert will be recommended for removal, and the sharp bend below assessed for stability. A map outlining planning level potential mitigation alternatives is included below. Bear Canyon Creek Informational Memo 9 Reach 2 While much of this channel functioned well during the 2013 flood event, there are mitigation alternatives that could improve key functions of the reach. Minimizing street flooding in this reach could benefit the access and egress in the nearby neighborhoods. An alternative exploring an enlarged channel capable of conveying up to the 100-year event without impacting the travel lanes of Table Mesa Drive could be beneficial. This enlarged channel section could include a multi-use path within the channel. Culverts downstream of Broadway have already been improved in this manner, and the crossing at Lehigh would benefit greatly from enlarging the structure to accommodate both foot traffic and flood flows. As part of a federal grant application for the Transportation Improvement Program (TIP), a preliminary feasibility analysis and conceptual level design for an underpass across Table Mesa at the Harvard Lane intersection was explored. Reach 2B extends from Broadway to Moorhead Avenue. This reach performed well during the 2013 flood, with the exception of damage caused by spill flows from upstream. Bear Canyon Creek Informational Memo 10 Reach 3 Since reach 2B is included for property loss purposes only, a small section has been included in the mitigation study for Reach 3A. The area immediately downstream of Moorhead Avenue is inundated by flows during a 100-year storm, some contributed by Skunk Creek from the north upstream of US Highway 36, as well as the culvert from the highway itself. Much of the storm water accumulation in this area may be solved by altering the outlet conditions for the Highway 36 culvert. This culvert could be improved by re-grading the area immediately downstream and reconfiguring the pedestrian path as it connects to the pedestrian bridge to the north of Highway 36. Currently, the separation wall for the path effectively limits flows in the culvert to only one of the two cells. It may also be necessary to install a third cell at this crossing to insure passage of higher flows given debris blockage and pedestrian path considerations. Downstream of the pedestrian bridge, the floodplain opens up to the Williams Village Campus of the University of Colorado (CU). CU has a master plan for this area that includes residential/institutional use (family student housing) and incorporates a stream crossing for access. Vegetation management and grading to create floodplains are two possible strategies that could be beneficial in this reach. Finally, the private drive for the church located immediately upstream of Baseline Road severely limits the capacity of the Baseline culvert. This undersized culvert at the church diverts flows on to Baseline Road instead of allowing them to flow through the Baseline culvert. During the 2013 event, this split flow caused damage at and around the church as well as into reach 3B. Reach 3B begins at Baseline and extends downstream to Mohawk Drive. The channel in Reach 3B functions relatively well with some exceptions. Damages in this area are mainly influenced by spills upstream of the reach, and thus no mitigation measures are planned for this reach as a part of this study. Bear Canyon Creek Informational Memo 11 COST BENEFIT ANALYSIS During Phase 2 of the study, a cost benefit analysis will be conducted after a full list of alternatives is developed. NEXT STEPS: Following public input from the April Open House and WRAB meeting, staff and the consultants will continue to prepare a draft Mitigation Plan. Phase 2 of the plan will consist of a feasibility analysis of mitigation alternatives. AMEC and city personnel will develop these alternatives into a complete plan for comparison and public comment. Potential environmental impacts, as well as legal and Right of Way issues will be identified for further analysis by city staff. Phase 2 of the mitigation study is scheduled to be presented to WRAB at the August 2015 meeting. Phase 3 of the study will include a set of alternatives which will be presented to WRAB in November 2015 with a request for a recommendation to approve the mitigation plan. If approved, the plan will be presented to City Council for consideration. ATTACHMENTS Attachment A: Conceptual Alternative Development memo Attachment B: Phase 1: Flood Loss Estimation Technical Memorandum Attachment C: Open House Figures (5) Attachment D: Master Plan Guidance and Policies Bear Canyon Creek Informational Memo 12 Attachment A: Conceptual Alternative Development Memo Phase 1: Flood Mitigation Master Plan for Bear Canyon Creek Conceptual Alternative Development Background The current conditions along Bear Canyon Creek do not represent a natural ecosystem. Currently, many non-native species are present that negatively contribute to the functioning of the system. Species diversity is low, consisting of primarily non-native crack willow (Salix fragilis), Russian olive (Elaeagnus angustifolia), and Siberian elm (Ulmus pumila). Crack willow specifically is highly susceptible to breaking branches during extreme weather events, and likely contributed to the clogging of culverts and subsequent overland flooding. In urbanized neighborhoods, constrained channels undermine the root systems of species such as Siberian Elm, resulting in large woody debris transported downstream during an extreme event. In addition, unstable channel conditions contribute to the generation and transport of sediment. In the upper reaches of Bear Canyon Creek, channel slope in excess of 5 to 7 percent create excessive potential energy which results in high velocities and channel shear stress. The stream transitions from its headwaters as a cascading gully in the sandstone of the Fountain Formation which make up the Flatirons to an alluvial floodplain across the Pierre shale to the east, passing through the uplifted sandstone layers of the Dakota sandstone making up the first hogback west of boulder. The changes in gradient result in an imbalance of energy which seeks equilibrium through picking up and transporting sediment. This high energy gradient passes through the softer alluvium formed by natural erosive forces forming meanders until the stream meets a constriction, either from the hard underlying sandstone or by an anthropomorphic feature such as a bridge or culvert. As flows pass through a constriction, the head loss is translated upstream as a slowing in velocity and the sediment load is deposited, while the cleaner water then accelerates through the constriction. In an extreme event, such as the 2013 flood, deposition at these constrictions actually block the channel and flows overtop whatever feature has formed the constraint. In the case of a culvert or bridge, these overtopping flows then find their way back to the natural stream valley via roadways and neighborhoods, picking up more debris from damaged structures and creating more deposition zones where smaller constrictions develop. Typically, the culverts and bridges are designed for a 10-25 year event considering debris blockage. In the 2013 event, characterized as a 25-50 year peak flow over the Bear Canyon Creek watershed, the actual precipitation distribution was on the order of a one thousand year event. This resulted in saturated soils and friable (easily transported) debris in the floodplain which created a slurry flow as the peak runoff occurred. Culverts and bridges were completely blocked by debris, and the resultant overtopping condition resembled a 100 year flooding event. This resemblance however, is only in the pathways seen by the floodwaters. An actual 100 year event would produce greater depth along these pathways, creating far more damage to structures and utilities. Bear Canyon Creek Informational Item1 Attachment A: Conceptual Alternative Development Memo Flood Mitigation Master Plan for Bear Canyon Creek Phase 1: Conceptual Alternative Development The purpose of this study is to explore mitigation strategies aimed at reducing damage from flood events. The creek in general has been described as being relatively stable during baseflow conditions and smaller events, requiring only routine maintenance. Conceptual level alternatives have been developed here which address the problems associated with larger events, but must also take into account the underlying morphology and ecology of the stream. These alternatives fall into three categories: non-structural measures, structural improvements, and debris management. Non-structural alternatives will target vegetation management and maintenance. The riparian zone will be evaluated for vegetative debris production, transport and control, while the maintenance program will be assessed and suggestions made for improvements. Structural alternatives consist of stream restoration, floodplain connection and capacity improvements to stream crossings. The feasibility of debris control structure solutions will be evaluated as well as improvements to pedestrian crossings. Finally, debris catchment areas will be evaluated for storage potential, location relative to downstream crossings and maintenance access. They will also be evaluated as either public or ecosystem amenities depending on ownership and designated use. Reach 1 Reach 1 extends from the upstream limit of the study area at the corporate limits to just upstream of Lehigh Street. The reach consists of City open space, medium density suburban, and high density townhome use. Major constrictions occur at Wildwood Road, a pedestrian bridge connecting Bear Creek Elementary school to Bear Mountain Drive, and an old boiler tank crossing the stream at Wildwood and Ithaca. The stream itself transitions from a high gradient,cascading gully section upstream of Wildwood to a V-shape section below Wildwood which becomes deeply incised downstream of Ithaca. Vegetation management and debris control are crucial to improving the capacity of the channel. Invasive species should be controlled and the channel stabilized to reduce channel degradation. Several opportunities exist for debris mitigation, including areas immediately upstream of Wildwood and Lehigh. Another opportunity exists for a larger area immediately adjacent to the Bear Creek Elementary school within the Bear Creek park. These areas could be graded to receive debris deflected into them with strategically placed rock structures in the stream, and maintenance access provided to remove the accumulated debris periodically. The area immediately adjacent to Wildwood above Ithaca is currently degraded and full of invasive species, both willow and elm trees. This area could be regraded to connect the floodplain and stabilized with non-structural treatments such as root wads and faschines (bundles of straw staked with native willow and seeded with a riparian see mix). The area could then be replanted and managed as a riparian corridor per the greenways master plan. The Wildwood culvert should be assessed for improvements to hydraulics and debris control. These improvements may consist of maintenance near the up and downstream face of the structure for sediment and vegetation, modifications to the structure including beveling of the top section, placing fins or a debris deflector in front of the entrance or increasing the cell size or number. The pedestrian bridge (CR-R1-2) was replaced after the 2013 flood, however the channel approaches up and downstream are severely incised and should be stabilized. The old boiler section will probably need to be removed, and the sharp bend below assessed for stability. Reach 2 Amec Foster Wheeler Environment & Infrastructure, Inc. Page| Ϯ 1002 Walnut Street Boulder, CO 80302 Tel (303) 443-7839 .amecfw.com www Bear Canyon Creek Informational Item2 Attachment A: Conceptual Alternative Development Memo Flood Mitigation Master Plan for Bear Canyon Creek Phase 1: Conceptual Alternative Development Reach 2 is divided into two sections. Reach 2A extends from the crossing at Lehigh to Broadway, while reach 2B extends from Broadway to Moorhead. The upstream limits of these reaches are technically at the upstream face of these crossings so that the downstream mitigation impacts can be assessed. Reach 2A is an urban transportation zone, with the floodplain mainly confined to Table Mesa Drive and the creek situated within the parkway. The stream channel is designed to contain the 25 year event with drop structures and crossings sized for stability and conveyance, while the Parkway itself forms the floodplain. Residential structures are minimally impacted by the flooding source, however commercial properties at the downstream limits of the reach are susceptible to damage in larger events. The Harvard lane culvert in particular has insufficient capacity to pass flood flows, especially with debris blockage, and overland flows are translated to Reach 2B, where substantial damage results. Debris management is limited in this area to the catchment immediately upstream of Lehigh described earlier, and a small catchment upstream of Yale Road. The catchment at Yale receives flows from a significant tributary area, and could be important in mitigating debris downstream. A great opportunity exists to combine an enlarged channel through this reach capable of conveying up to the 100 year event with a pedestrian path system. Culverts downstream of this area have already been improved to this degree, and the crossing at Lehigh would benefit greatly from enlarging the structure to accommodate both foot traffic and flood flows. This could be combined with a structural channel section downstream to Harvard with at grade crossings in between to minimize cost. The crossing at Harvard Lane and Broadway has already undergone a preliminary feasibility analysis and conceptual level design, but must include a more comprehensive consideration of the hydraulics involved. Reach 2B extends from Broadway to Moorhead Street. This reach performed well during the 2013 flood, with the exception of damage caused by spill flows from upstream. The area immediately downstream of Moorhead is inundated by flows contributed by Skunk Creek from the north upstream of US Highway 36, as well as the culvert from the highway itself. For this reason, the areas of flooding immediately upstream and extending downstream are included in Reach 3. No opportunities for flood mitigation as part of this plan are identified in Reach 3B. Reach 3 Reach 3 is also divided into two sections for the same reasons identified in Reach 2. Reach 3A begins at US Highway 36 and extends through the University of Colorado South Campus to Baseline Road. This reach is currently undeveloped except for the lower limits, and consists of disturbed land and low flow crossings. The channel has insufficient capacity for any flows above the 2 year event, and is overgrown with invasive species. Poor outlet conditions at the US Highway 36 culvert exacerbate flooding upstream and create a spill situation across highway 36 in extreme events. A private drive at the downstream limits of the reach just upstream of Baseline contribute to spills across Baseline, severely limiting the effectiveness of the Bear Canyon Creek culvert under Baseline Road. The outlet conditions for the Highway 36 culvert could be greatly enhanced by regarding the area immediately downstream and reworking the pedestrian path. Currently, the separation wall for the path effectively limits flows in the culvert to only one of the two cells. By extending the path approach farther to the east, perhaps incorporating this into improvements with the Amec Foster Wheeler Environment & Infrastructure, Inc. Page| ϯ 1002 Walnut Street Boulder, CO 80302 Tel (303) 443-7839 .amecfw.com www Bear Canyon Creek Informational Item3 Attachment A: Conceptual Alternative Development Memo Flood Mitigation Master Plan for Bear Canyon Creek Phase 1: Conceptual Alternative Development pedestrian bridge immediately downstream, the hydraulic efficiency of the Highway 36 crossing may be enough to pass extreme events. It may also be necessary to install a third cell at this crossing to insure passage of higher flows given debris blockage and pedestrian path considerations. Downstream of the pedestrian bridge, the floodplain opens up to the South Boulder Campus of the University of Colorado. A master plan has been developed for this area that includes residential/institutional use (student housing) and incorporates a stream crossing for access. Vegetation management could enhance the conveyance capabilities in this area and reduce floodplain width. It is anticipated however, that this measure will not provide sufficient gains to eliminate flooding which impacts downstream areas adjacent to Baseline Road. A strategy which incorporates a complete restructuring of the riparian corridor through this reach including grading to reconnect the floodplain (FC-R3-1), stabilization of the stream, and a careful design of any crossings could provide benefits to both the property owner (CU) and residential and commercial interests downstream. Finally, the private drive located immediately upstream of Baseline Road severely limits the have sufficient capacity to convey the channel discharges during spring runoff events. This drive may benefit from a much larger culvert, a combination culvert low water crossing, or by abandoning the crossing altogether. This crossing would require investigation in conjunction with both improvements upstream aimed at confining the floodplain, and consideration of containing resultant flows to downstream reaches. Reach 3B begins at Baseline and extends downstream to Mohawk Drive. This area is greatly influenced by the dynamics of flooding upstream. Spills which occur above baseline are transmitted overland through residential neighborhoods to the confluence area immediately upstream of Foothills Highway. This is a complicated confluence zone influenced by both South Boulder Creek to the south and east, and Skunk Creek to the west. The channel itself in Reach 3B functions relatively well except for a sharp bend to the right immediately upstream of Mohawk. Damages in this area are mainly influenced by spills upstream of the reach, and thus no mitigation measures are planned for this reach as a part of this study. The capacity and stability of the channel will, however be assessed as part of containing flows from upstream. Amec Foster Wheeler Environment & Infrastructure, Inc. Page| ϰ 1002 Walnut Street Boulder, CO 80302 Tel (303) 443-7839 .amecfw.com www Bear Canyon Creek Informational Item4 Attachment B Memo March 30, 2015 dŽ͗Ward Bauscher, Engineering Project Manager, City of Boulder Public Works - Utilities &ƌŽŵ͗Jeff Brislawn, Hazard Mitigation Lead/Associate ͗Joel McGuire, Project Manager ZĞĨ͗Flood Mitigation Master Plan Bear Canyon Creek ZĞ͗Phase 1: Flood Loss Estimation Technical Memorandum This report summarizes a study that estimated the building damage impacts from flooding on existing development in three stream reaches along Bear Creek in the City of Boulder, Colorado. The results and additional details on the methods follow in this technical memorandum. DŽĚĞůĞĚ&ůŽŽĚ>ŽƐƐĞƐ ĂĐŬŐƌŽƵŶĚ Hazus--based natural hazard loss estimation tool, was initially used to perform a flood loss estimation within the reaches. Site-specific building information for each of the study areas was provided by the FEMA Region VIII via the City. Inspection of the databased revealed that the building dataset was missing point locations for several buildings within the 100 or 500 year floodplain. At least 452 points were missing, including one of the Bear Canyon townhomes that was flooded in 2013. Amec Foster Wheeler staff identified the missing parcels and City staff was able to assist with developing point data for these parcels and populate 8 columns of attributes to match up to the FEMA point data. We also developed additional points so that individual condos/townhomes and business were represented in the model. Many of these were represented by one point for large commercial parcels such as the Table Mesa Shopping Center. Additionally, the provided attribute data needed additional processing steps to prepare it for import into Hazus, including adding content value, estimated first floor height based on building type, and latitude longitude. The second input into the model was a depth grid, which is a grid-based GIS file that indicates the depth of flooding at a particular grid cell. Flood depth grid data provided by FEMA was limited to the effective 100 year (1% annual chance) return period. The building data was formatted and imported into the Hazus regions for loss analysis using the 100 year FEMA depth grid. Default reports to display Hazus results do not work well with user-defined data, so the loss data needed to be aggregated outside of Hazus in a spreadsheet. QC of the results revealed that the depth damage curves were not being applied appropriately by Hazus and thus the loss estimation was underestimated. This is a known bug in Hazus. In order to fix this we had to use a spreadsheet developed for a previous project as a work around to ensure that the appropriate depth damage curve was being applied. Attachment B Flood Mitigation Master Plan for Bear Canyon Creek Phase 1: Flood Loss Estimation Technical Memorandum On February 25 the City provided an email that suggested the FEMA Benefit Cost Analysis (BCA) methodology should be used instead of Hazus for a more comprehensive and accurate loss analysis. The BCA module also uses Army Corp of Engineers (Corp) - developed depth damage curves as opposed to the National Flood Insurance Program Flood Insurance Administration curves in Hazus. The Corp curves are considered more appropriate and are also used by UDFCD in master planning studies. Subsequent conversations with the City suggested we should use the Corp curves and consider doing a Further analysis of the 2013 flood event damage data and flood extent (including GIS and YouTube video information) revealed that losses outside of the 100 year flood plain occurred in the Martin Acres reach between Broadway and US 36. These losses were due to split flows near the Table Mesa Broadway intersection that diverted flows down streets and into the neighborhood and flooded homes in the 500 year floodplain. From this analysis it became clear that the area between Broadway and US 36 (Martin Acres) that was previously excluded from the scope needed to be included, as improvements in reach 2 could benefit this area. A similar conclusion was reached for the area downstream of reach 3 north of Baseline Rd. Additional building data was collected in these areas for analysis. The following figure displays the study area and the limits of the 3 reaches and sub-reaches analyzed. >ŽƐƐƐƚŝŵĂƚŝŽŶDĞƚŚŽĚŽůŽŐǇ The methodology utilized shifted from Hazus-based to an initial planning-level BC analysis. A spreadsheet provided by FEMA was used to aggregate building loss information. This was developed by FEMA for input of detailed structure information into the FEMA BCA tool for drainage projects. Amec Amec Foster Wheeler Environment & Infrastructure, Inc. Page| Ϯ 1002 Walnut Street Boulder, CO 80302 Tel (303) 443-7839 www.amecfw.com Attachment B Flood Mitigation Master Plan for Bear Canyon Creek Phase 1: Flood Loss Estimation Technical Memorandum Foster Wheeler used this spreadsheet tool moving forward. The spreadsheet was modified to include depth damage curves for commercial properties as these properties are present in the study area. This method utilizes estimated first floor heights based on the following building relationships from the Hazus technical manual. ^ŽƵƌĐĞ͗,ĂǌƵƐZŝǀĞƌŝŶĞ&ůŽŽĚdĞĐŚŶŝĐĂůDĂŶƵĂů The majority of the structures in the watershed are Pre-FIRM (constructed prior to the adoption of the first Flood Insurance Rate Map on July 17, 1978) residential structures with a mix of slab and basements. A grant-level BC analysis would require additional analysis, possibly including surveyed first floor elevations or analysis of LiDAR data to refine the estimate of these. A grant-level BCA may also require gathering additional benefit information to produce a benefit cost ratio of 1 or greater. A best available information model was developed to produce the 10-year flood (10% annual chance), 50-year flood (2% annual chance), 100-year flood (1% annual chance), and 500-year flood (0.2% annual chance) events. Due to the complex nature of the flooding source, certain assumptions had to be made in the modeling process. Overtopping occurs at several major crossings, most notably Broadway Street and Baseline Road. Spills from these areas become hydraulically disconnected from the main channel, flow overland through streets and neighborhoods and then rejoin the floodplain downstream. Boundaries for these flows were manually delineated in the original FHAD study, and digitized as part of the current DFIRM. For the purposes of this analysis, areas outside of the main AE zone, yet within the 500-year floodplain were assumed to have a flooding depth of 2 feet for the 500-Yr analysis, 1 foot for the 100-Yr analysis, and zero for the 50-Yr analysis. These areas were joined to the calculated depth grid for areas within the main AE Zone for each corresponding recurrence interval. The building point layer was overlaid onto each depth grid in GIS and a spatial join was performed to determine the depth of flooding at each structure for each return period. The tabular database was incorporated into the modified BCA spreadsheet to perform the loss calculations. Depth damage functions in the BCA spreadsheet were applied to create a detailed loss estimate for buildings in the reaches for the various flood events. The following figure is a snapshot from reach 3B that illustrates Amec Foster Wheeler Environment & Infrastructure, Inc. Page| ϯ 1002 Walnut Street Boulder, CO 80302 Tel (303) 443-7839 www.amecfw.com Attachment B Flood Mitigation Master Plan for Bear Canyon Creek Phase 1: Flood Loss Estimation Technical Memorandum the depth grid and flooded structures and how depth values were used in the spreadsheet to calculate building damage, based on depth-damage curves within the spreadsheet tabs. Results Results of the analyses are presented in the following table, which is followed by a discussion of the results by reach. Amec Foster Wheeler Environment & Infrastructure, Inc. Page| ϰ 1002 Walnut Street Boulder, CO 80302 Tel (303) 443-7839 www.amecfw.com Attachment B Flood Mitigation Master Plan for Bear Canyon Creek Phase 1: Flood Loss Estimation Technical Memorandum dĂďůĞϭƐƚŝŵĂƚĞĚ&ůŽŽĚ>ŽƐƐďǇ^ƚƌĞĂŵZĞĂĐŚ ^ƚƌƵĐƚƵƌĞƐƵŝůĚŝŶŐŽŶƚĞŶƚƐŝƐƉůĂĐĞŵĞŶƚ ZĞƚƵƌŶWĞƌŝŽĚdŽƚĂůĂŵĂŐĞƐ ĂŵĂŐĞĚĂŵĂŐĞĂŵĂŐĞĂǇƐ Reach 1; US Study Limit to Lehigh 500-year Flood35$ 816,208$ 330,054$ 1,146,2620 Days 100-Year Flood0 Days $ -$ -$ - 50-Year Flood0 Days $ -$ -$ - Reach 2A; Lehigh to Broadway 500-year Flood20$ 722,622$ 386,778$ 1,109,400315 Days 100-Year Flood11$ 252,533$ 67,119$ 319,6520 Days 50-Year Flood0 Days $ -$ -$ - Reach 2B; Broadway to Moorhead 500-year Flood143$ 5,738,407$ 1,717,123$ 7,455,5297560 Days 100-Year Flood117$ 4,006,369$ 1,139,296$ 5,145,6644455 Days 50-Year Flood0 Days $ -$ -$ - Reach 3A; Moorhead to Baseline 500-year Flood144$ 4,918,883$ 1,781,786$ 6,700,6682070 Days 100-Year Flood43$ 991,125$ 302,847$ 1,293,97290 Days 50-Year Flood7249,852$ $ 79,161$ 329,013180 Days Reach 3B; Baseline to DS Study Limit 500-year Flood70$ 1,700,570$ 624,577$ 2,325,147540 Days 100-Year Flood593,737$ $ 32,540$ 126,2760 Days 50-Year Flood13,913$ $ 1,878$ 5,7910 Days Total Damages for Study Area by Return Period 500-year Flood412$ 13,896,690$ 4,840,317$ 18,737,00610485 Days 100-Year Flood176$ 5,343,763$ 1,541,801$ 6,885,5644545 Days 50-Year Flood8253,765$ $ 81,039$ 334,804180 Days The table displays losses by stream reach and sub-reach for the 50, 100, and 500 year flood events. There was no risk of structure flooding to the 10 year event risk within any reach, thus no losses are shown. All reaches have risk to the 100 and 500 year events. Only reach 3 has risk to the 50 year event. Total damages across all reaches for the 50 year event is estimated at $335,000; the 100 year and 500 year total estimated damages are $6.9M and $18.7M respectively. Reach 1 has the lowest risk to flooding of the 3 reaches and does not result in flood loss from the 100 year event. The 500-year event affects 35 residential structures, with a total damage of $1.1M. While there is no modeled risk to the more frequent interval floods, it should be noted that debris and culvert blockage during the 2013 flood (estimated to be a 25 year event) caused flooding in the 500 year floodplain in this reach. Reach 2A and 2B has the most buildings of the three reaches, including the most commercial structures. The commercial structures are associated with the Table Mesa Shopping Center at the intersection of Table Mesa and Broadway. This area has the greatest risk from the 100 and 500 year floods. The Amec Foster Wheeler Environment & Infrastructure, Inc. Page| ϱ 1002 Walnut Street Boulder, CO 80302 Tel (303) 443-7839 www.amecfw.com Attachment B Flood Mitigation Master Plan for Bear Canyon Creek Phase 1: Flood Loss Estimation Technical Memorandum majority of this damage is associated with reach 2B east of Broadway. The 100 year flood analysis results in less than $400k in damages between Lehigh and Broadway in reach 2A, and $1.1M associated with the 500 year event. Reach 3A and 3B has 213 residential structures and a church at risk to flooding. This reach is the only reach to have some risk to the more frequent 50 year flood event (8 structures total). Reach 3A has substantial risk to the 500 year flood event. /ŶĐŽŵĞZĞůĂƚĞĚ>ŽƐƐĞƐĂŶĚĞďƌŝƐ'ĞŶĞƌĂƚŝŽŶƐƚŝŵĂƚĞƐ Hazus has utility in estimating Income related losses and debris (building related as opposed to soil and woody debris), and these losses were calculated based on the Census block based inventory associated with a Level 1 Hazus flood run, but utilizing the user-defined depth grids. These losses were modeled to capture additional losses due to business interruption and debris estimates. Income related losses include a one-time flood disruption cost, rental income losses, and capital income losses. A single Hazus study area was created to encompass all three reaches. Total income losses were estimated at $130,000 for the 100 year and $146,000 for the 500 year event. Debris generation was estimated at 1,150 tons for the 100 year and 1,303 tons for the 500 year event. These values, in addition to the structure loss estimates previously discussed, can be used as a baseline for comparison as flood mitigation alternatives are modeled in future phases of the project. Amec Foster Wheeler Environment & Infrastructure, Inc. Page| ϲ 1002 Walnut Street Boulder, CO 80302 Tel (303) 443-7839 www.amecfw.com Attachment D Master Plan Guidance and Policies The Boulder Valley Comprehensive Plan(BVCP), the Comprehensive Flood and Stormwater Utility Master PlanGreenways Master Planand the Urban Drainage and Flood Control District (UDFCD) Drainage Criteria Manualall contain policies related to floodplain preservation, development, and mitigation. These documents guide the flood mitigation master planning. The following applicable policies are included in the BVCP: 3.19 Preservation of Floodplains Undeveloped floodplains will be preserved or restored where possible through public land acquisition of high hazard properties, private land dedication and multiple program coordination. Comprehensive planning and management of floodplain lands will promote the preservation of natural and beneficial functions of floodplains whenever possible. 3.20 Flood Management The city and county will protect the public and property from the impacts of flooding in a timely and cost-effective manner while balancing community interests with public safety needs. The city and county will manage the potential for floods by implementing the following guiding principles: a) Preserve floodplains b) Be prepared for floods c) Help people protect themselves from flood hazards d) Prevent unwise uses and adverse impacts in the floodplain e) Seek to accommodate floods, not control them. The city seeks to manage flood recovery by protecting critical facilities in the 500-year floodplain and implementing multi hazard mitigation and flood response and recovery plans. 3.21 Non-Structural Approach The city and county will seek to preserve the natural and beneficial functions of floodplains by emphasizing and balancing the use of non-structural measures with structural mitigation. Where drainageway improvements are proposed, a non-structural approach should be applied wherever possible to preserve the natural values of local waterways while balancing private property interests and associated cost to the city. 3.22 Protection of High Hazard Areas The city will prevent redevelopment of significantly flood-damaged properties in high hazard areas. The city will prepare a plan for property acquisition and other forms of mitigation for flood-damaged and undeveloped land in high hazard floodareas. Undeveloped high hazard flood areas will be retained in their natural state whenever possible. Compatible uses of riparian corridors, such as natural ecosystems, wildlife habitat and wetlands will be encouraged wherever appropriate. Trails or other open recreational facilities may be feasible in certain areas. 3.23 Larger Flooding Events The city recognizes that floods larger than the 100-year event will occur resulting in greater risks and flood damage that will affect even improvements constructed with standard flood protection measures. The city will seek to better understand the impact of larger flood events and consider Master Plan Guidance and PoliciesPage 1 Attachment D necessary floodplain management strategies including the protection of critical facilities. The CFS contains the following guiding principles for flood management: 1.Preserve Floodplains (Preservation); 2.Be Prepared for Floods (Preparedness); 3.Help People Protect Themselves from Flood Hazards (Education); 4.Prevent Adverse Impacts and Unwise Uses in the Floodplain (Regulation); 5.Seek to Accommodate Floods, Not Control Them (Mitigation). More detail about each of these guiding principles can be found in Chapter 3 of the CFS. The fifth principal, as listed above, is directly related to mitigation and, in the CFS, more completely states: Seek to accommodate floods, not control them through planned and monitored system maintenance, nonstructural flood proofing, opening non-containment corridors, overbank land shaping to train flood waters, and limited structural measures at constrained locations. Possible tools for implementation include: Update mitigation master plans to emphasize nonstructural measures. R Re-evaluate mitigation priorities to eliminate bottlenecks, acquire land to avoid R channel improvements, provide non-structural overbank grading, target limited flood protection improvements for high hazards, and research alternative mitigation approaches. Assess any need for structural improvements with evaluation of multiple R alternatives. Focus on mitigating high hazard locations citywide and give priority to areas of R the greatest risk. The UDFCD Drainage Criteria Manual contains the following basic policies: The major drainageway system shall be capable of conveying water without flooding buildings and shall remain relatively stable during a 100-year flood. Public safety is fundamental to the major drainageway system. Public acceptance of the major drainageway system depends on a multitude of factors such as public perception of flood protection, channel aesthetics, right-of-way, open space preservation, and channel maintenance. Identify areas with potential for recreational use. Consider environmental impacts and benefits and examine the advantages and disadvantages. Open channels are more desirable than underground conduits in urban areas because they are closer in character to natural drainageways and offer multiple use benefits. Consider two-stage channels. In some cases, it may be desirable to balance the 100-year flow between a formal channel and the adjacent floodplain. The purpose of the Greenways Program is to extend the stewardship of the city to important riparian areas along the tributaries of Boulder Creek. The Greenways Master Plan includes the following objectives: Master Plan Guidance and PoliciesPage 2 Attachment D To protect and restore riparian, floodplain, and wetland habitat; To enhance water quality; To facilitate storm drainage and mitigate floods; To provide alternative transportation routes or trails for pedestrians and bicyclists; To provide recreation alternatives; To protect cultural resources. The intent of the flood mitigation plan is to mitigate flood damage and facilitate storm drainage. Improvements along this creek corridor could also include enhancements to water quality and riparian areas. These various master plan guiding principles and policies, specifically those related to mitigation, have provided the foundation for developing the Bear Canyon Creek Mitigation Plan. The initial alternatives under consideration include structural improvements, debris management alternatives by improving the quality of the stream ecosystem and sediment control through various measures including improving and connecting floodplain configurations. Master Plan Guidance and PoliciesPage 3 INFORMATION ITEM MEMORANDUM To: Members of the Water Resources Advisory Board From: Jeff Arthur, Director of Public Works for Utilities Joe Taddeucci, Water Resources Manager Bret Linenfelser, Water Quality Manager Kim Hutton, Water Resources Engineer Craig Skeie, Water Resources Facilities Manager Russ Sands, Watershed Sustainability & Outreach Supervisor MaryAnn Nason, Water Conservation & Outreach Coordinator April 27, 2015 Date: Drought Response Overview and Water Supply Update Subject: EXECUTIVE SUMMARY: determination procedures as set forth in the Drought Plan (Attachment 2). BACKGROUND: The Drought Plan consists of two separate volumes and is intended to provide guidance for recognizing and responding to droughts that will affect water supply availability. Volume I categorizes drought alert levels according to severity and also includes actions that might be taken to respond to each drought alert level. Volume II contains detailed technical supporting information. During development of the Drought Plan, the city est system using hundreds of years of tree-ring based historical hydrology. The storage index is basically a ratio of key storage parameters divided by projected demand. Staff applies the formula each year in early May when key water supply information becomes known. The drought alert levels corresponding to various storage index values are shown in Table 1. The Drought Plan identifies water use reduction goals and response options for each stage of conditions and is reviewed in conjunction with other appropriate data and operating experience. While early May is a decision point in analysis, staff is continuously Information Item Page 1 monitoring trends in snowpack, precipitation, runoff, reservoir filling and water system administration throughout the year. Table 1: Suggested drought response triggers for May 1 (City of Boulder Drought Plan, Volume 1) Projected Drought Alert Storage Index (1) Stage Greater than 0.85 None Between 0.85 and 0.7 I Between 0.7 and 0.55 II Between 0.55 and 0.4 III Less than 0.4 IV (1)Projected storage index = (projected usable Boulder mountain storage + 40% of -drought years. ANALYSIS: North and Middle Boulder Creeks) and Colorado Big Thompson (CBT) water sources (Attachment 1). As of April 1, 2014, water With the exception of Silver Lake Reservoir, which is currently being partially drained for a spring outlet works inspection, mountain reservoir storage levels in the North Boulder Creek basin are roughly full. On the Middle Boulder Creek side, Barker Reservoir is about 75% full while Kossler Reservoir is mostly drained for a spring and summer construction project. Despite the dam safety and construction work, staff anticipates that all reservoirs will fill this year. Snowpack is about average for this time of year. As of April 1, 2015, snow water equivalent measurements were average for the Boulder Falls Snow Course and University Camp Snotel Sites. If the March dry trend continues through April, May 1 needs. Initial indications from the Northern Colorado Water Conservancy District are that the 1 Colorado Big Thompson (CBT) 2015 allocation will be 70%. A 70% allocation represents 14,709 acre-feet of water available to the city. The annual CBT allocation is typically about 70%. May 1 is the time of year when the key city water supply factors are the most informative because the snowpack has usually fully developed by this time, and allotment for the year is known. Those two items combined with current reservoir storage levels provide a storage index calculation is still a few weeks away, it is unlikely that a drought response will be triggered. 1 The city water utility presently owns 21,015 units of CBT water. A 100 percent quota provides one acre-foot of water for each unit for that year. The historical average for the annual quota is about 70 percent or 0.7 acre-foot per unit. Information Item Page 2 NEXT STEPS: Staff continuously monitors water supply conditions and will perform the storage index calculation in early May. As in every year, staff will continue to inform the public of the status of the water supply and encourag helps coordinate outreach efforts locally and regionally, working with Water Resources to monitor supply conditions and increase outreach efforts if hot, dry conditions are expected. ATTACHMENTS: 1 City of Boulder Source Waters 2 City of Boulder - Drought Plan (electronic links) Information Item Page 3 Attachment 2 City of Boulder Drought Plan (electronic links) DROUGHT PLAN - Volume I Drought Planning and Response Plan DROUGHT PLAN - Volume II Technical Information and Analysis Information Item Page 5