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Complete WRAB Packet 8-18-14 WATER RESOURCES ADVISORY BOARD MEETING MEETING DATE: Monday, 18 August 2014 MEETING TIME: 7:00 p.m. MEETING LOCATION: City Council Chambers, 1777 Broadway Agenda Highlights: 1.Call to Order (7:00 p.m.) 2.Approval of 21 July Meeting Minutes (7:01 p.m.) 3.*Public Comment (7:05 p.m.) 4.*Public Hearing and Consideration of a Recommendation to City Council Regarding the South Boulder Creek Major Drainageway Plan and Mitigation (7:30 p.m.) 5.Information Item - (9:00 p.m.) 6.Matters (9:30 p.m) -From the Board -From Staff 7.Future Schedule (9:40 p.m.) 8.Adjournment (9:45 p.m.) * Public Comment Item Information: Please contact the WRAB Secretary email group at: WRABSecretary@bouldercolorado.gov. Packets are available in the reference section of the Main Library and on-line at: http://www.bouldercolorado.gov - Departments, Public Works, Utilities, Water Resources Advisory Board. Agenda item times are approximate. CITY OF BOULDER, COLORADO BOARDS AND COMMISSIONS MEETING MINUTES Name of Board / Commission: Water Resources Advisory Board Date of Meeting: 21 July 2014 Contact Information of Person Preparing Minutes: Kaaren Davis 303.441.3203 Board Members Present: Vicki Scharnhorst, Dan Johnson, Mark Squillace, Lesley Smith, Ed Clancy Board Members Absent: None Staff Present: Jeff Arthur, Director of Public Works for Utilities Bob Harberg, Principal Engineer - Utilities Katie Knapp, Engineering Project Manager Kurt Bauer, Engineering Project Manager Annie Noble, Flood and Greenways Engineering Coordinator Bret Linenfelser, Water Quality and Environmental Services Manager Kaaren Davis, Board Secretary Meeting Type: Regular Agenda Item 1 Call to Order [7:00 p.m.] Agenda Item 2 Approval of the 16 June 2014 Meeting Minutes: [7:01 pm] 16 June minutes : Motion to approve minutes from June 16th as presented. Moved by: Squillace Seconded by: Johnson Vote: 4:0 Agenda Item 3 Public Participation and Comment [7:06 p.m.] Public Comment: Yael Cohen: Condo owners. FEMA insurance was inadequate to deal with flood damage. Want to make sure preventative measures are taken at this time. Show of hands shows approximately 10 . residents of the condominium development were wiped out by the flood Kathie Joyner: Significant property damage from the floods. Hopes the city can find a way to accomplish one of its goals to remove hundreds of dwellings from the floodplain. There are far reaching financial effects from the flood. Action is critical. Some did not have flood insurance, but those who did know that flood insurance is inadequate. Hopes that productive ways to mitigate future events can be found through cooperation between all of the involved agencies. Steve Karakitsios: Significant flood damage. Knows that the city has much on its plate. How do the residents track progress and budget expenditures related to the flood mitigation project ? proposals? How do we hold accountability? How can we see it and track it ourselves Jeff McWhirter: President of SE Boulder neighborhood association. We are victims of geography and ourselves. We dodged a bullet last fall, the event was not as bad as it could have been. We have hundreds of homes in the floodplain and that will be expensive to mitigate. Staff has done a good job in the past. Problems are expensive to fix but we really do need to fix them. Don Prince: Had some flooding but was not too bad. Three things could have reduced flooding. th Water going north on 9 had no route to the creek and ended up on Canyon. No ingress to Farmers th Ditch. At 17 Farmers Ditch goes under the road and there was a bottle neck there. Believes that Ditch needs to be deeper to accommodate flood waters. Diane Fritz: Goss Grove neighborhood association representative. Here to observe the conversation about mapping the Boulder Slough. Even though most of the discussion is farther Board follow up: Board requested details from staff on Osage and Quala and Quayden (South Boulder Creek). Board and staff provided information on how the public can follow up on projects and budget expenditures and keep themselves informed throughout the flood recovery, reconstruction and WRAB Minutes 21 July 2014 Page No. 1 mitigation process moving into the future. Agenda Item 4 [7:26 p.m.] Information Item Overview of Floodplain Management Program and Floodplain Mapping Studies. Jeff Arthur and Annie Noble presented the item. Executive Summary from the Packet Materials: The purpose of this memorandum is to provide a general summary of the history and progress made to date on the South Boulder Creek flood mitigation planning study. This mitigation plan was initiated in 2010 after the floodplain mapping was updated in 2007. Since the study was initiated, multiple flood mitigation alternatives have been evaluated to address flooding associated with South Boulder Creek. A consultant recommendation has been developed and is described in this memorandum. A more detailed description of the recommended alternative will be presented and a request for a motion from the WRAB will be made at a meeting scheduled on August 18. Attachment A shows the location of the study area. Hydraulic modeling indicates that a major storm event will cause water from South Boulder Creek to overtop US36 near Table Mesa Drive and result in flooding through the West Valley (area generally located west of South Boulder Creek, north of US36, east of Foothills Parkway and south of Arapahoe Avenue). The September 2013 flood event did overtop US36, causing an estimated $45 million in flood damage. A flood mitigation planning study began in early 2010 with a focus on developing and evaluating alternatives designed to mitigate flood hazards affecting structures and areas along South Boulder Creek and the West Valley within the current incorporated city limits. Conceptual alternatives were initially developed by problem area in a matrix format that included a wide range of mitigation measures. These concepts were then presented at a public meeting and subsequently combined into 15 Alternative Plans. These alternatives were evaluated and nine Best Alternative Plans were developed and presented at a second public meeting and to WRAB in late 2010. Four of the nine Best Alternative Plans were further refined and analyzed and the consultant team selected an engineering recommendation. Major components of the consultant recommended alternative include construction of a regional stormwater detention facility south of US36, a smaller detention facility at Manhattan Middle School and one at Flatirons Golf Course. The recommended alternative would provide significant flood protection within the West Valley area, including eliminating the 100-year floodplain designation that currently affects approximately 700 structures. The estimated cost of the alternative is approximately $46 million, but the project could be constructed in three phases. Construction of the project would require numerous permits, agreements with the University of Colorado and Boulder Valley School District, disposal of Open Space and Mountain Park land and would be regulated by the State as a high hazard dam. Construction of the regional detention facility at US36 would result in significant impacts to wetlands, habitat for threatened and endangered species and other environmental and aesthetic resources. WRAB Discussion Included: Clarifying questions on FEMA reimbursement rules and how this affects immediate flood recovery projects. Clarification on the scope and duration of FEMA audits on the drainage way recovery projects. Questions regarding resources available to residents to report issues and find information. Discussion on what would be required for Boulder to elevate itself from Class 5 to Class 4 in the community flood insurance program. Discussion of potential changes in how FEMA conducts flood reimbursements and flood insurance programs. Questions about how the drainage way system is handling the thunderstorms that Boulder has been having this season. Discussion of the role that Greenways paths and underpasses play in flood control. WRAB Minutes 21 July 2014 Page No. 2 No Board action was requested at this time. Agenda Item 5 [7:51 p.m.] Public Hearing and Consideration of Motions to Recommend Adoption of Floodplain Mapping Revisions for Lower Bear Canyon Creek and Upper Boulder Slough. Jeff Arthur, Bob Harberg and Katie Knapp presented the item. Executive Summary from the Packet Materials: The city has a comprehensive floodplain management program designed to identify flood risks, mitigate the risks of flooding, minimize loss of life and property damage and support recovery following a major flood the areas at the highest risk for flooding. Changes in land use, updated topographic mapping and upgrades to hydrologic and hydraulic models warrant periodic mapping updates. This memorandum presents two proposed floodplain mapping revisions: Public Comment: Rick Mahan: Severe damage from the September event. Water from his property traveled down and contributed to issues further downstream. The structures remaining in the flood zone really need to be removed, and soon. Don Prince : Potential loss of life resulting from bottle necks under bridges. Is there any chance to increase the size of the wall where the Boulder Slough starts? WRAB Discussion Included: Clarifications regarding the new High Hazard designations in the studied revisions. Questions about how the flood event of September 2013 may have changed the topography and hence the mapping. Discussion of how the assumptions that the studies are based on can be provided to the public and Discussion of reasons behind the significant changes to the mapping for the Boulder Slough. Discussion regarding how the ditches relate to floodplains, regulations etc. Motion: Motion to recommend that City Council adopt the Lower Bear Canyon Creek floodplain mapping revision. Motion by: Squillace; Seconded: Johnson Vote: 5-0 Motion: Motion to recommend that the City Council adopt the Upper Boulder Slough floodplain mapping revision. Motion by: Johnson; Seconded: Squillace Vote: 5-0 Agenda Item 6 [8:30 p.m.] Information Item Update on South Boulder Creek Floodplain Mitigation Study. Jeff Arthur and Kurt Bauer presented the item. Executive Summary from the Packet Materials: The purpose of this memorandum is to provide a general summary of the history and progress made to date on the South Boulder Creek flood mitigation planning study. This mitigation plan was initiated in 2010 after the floodplain mapping was updated in 2007. Since the study was initiated, multiple flood mitigation alternatives have been evaluated to address flooding associated with South Boulder Creek. A consultant recommendation has been developed and is described in this memorandum. A more detailed description of the recommended alternative will be presented and a request for a motion from the WRAB will be made WRAB Minutes 21 July 2014 Page No. 3 at a meeting scheduled on August 18. Attachment A shows the location of the study area. Hydraulic modeling indicates that a major storm event will cause water from South Boulder Creek to overtop US36 near Table Mesa Drive and result in flooding through the West Valley (area generally located west of South Boulder Creek, north of US36, east of Foothills Parkway and south of Arapahoe Avenue). The September 2013 flood event did overtop US36, causing an estimated $45 million in flood damage. A flood mitigation planning study began in early 2010 with a focus on developing and evaluating alternatives designed to mitigate flood hazards affecting structures and areas along South Boulder Creek and the West Valley within the current incorporated city limits. Conceptual alternatives were initially developed by problem area in a matrix format that included a wide range of mitigation measures. These concepts were then presented at a public meeting and subsequently combined into 15 Alternative Plans. These alternatives were evaluated and nine Best Alternative Plans were developed and presented at a second public meeting and to WRAB in late 2010. Four of the nine Best Alternative Plans were further refined and analyzed and the consultant team selected an engineering recommendation. Major components of the consultant recommended alternative include construction of a regional stormwater detention facility south of US36, a smaller detention facility at Manhattan Middle School and one at Flatirons Golf Course. The recommended alternative would provide significant flood protection within the West Valley area, including eliminating the 100-year floodplain designation that currently affects approximately 700 structures. The estimated cost of the alternative is approximately $46 million, but the project could be constructed in three phases. Construction of the project would require numerous permits, agreements with the University of Colorado and Boulder Valley School District, disposal of Open Space and Mountain Park land and would be regulated by the State as a high hazard dam. Construction of the regional detention facility at US36 would result in significant impacts to wetlands, habitat for threatened and endangered species and other environmental and aesthetic resources. WRAB Discussion Included: Discussion on how the current alternatives were developed and selected, as well as why other alternatives were not selected. Clarification regarding cost/benefit analysis to proposed options (including environmental impacts) NEPA requirements for multiple alternatives and the widely divergent costs of the various options. Clarification regarding the reason for a HWY 93 Detention option. Out of City limits and City unwilling to pursue an eminent domain option. What it means to have a structure regulated as a High Hazard Dam. How the detention basins would function in an event such as the September 2013 flood, which Discussion of the benefit/cost ratios for each of the alternatives. Discussion of how likely it is that the alternatives that affect endangered species would be approved. Questions as to whether there is a more modest alternative than the large detention ponds which would be less costly and have less impact on habitat. Request for a summarization of the 15 options which were originally presented to WRAB so that current board members can understand the background and development of the current options. No Board action was requested at this time. Agenda Item 7 Matters [9:04 p.m.] From the Board: Board member Clancy brought up the below matter(s): Concerned about the size of the Wastewater Treatment Plant. Has gone to the EPA to check on wet weather capacity. Interested in knowing what system infiltration rates are and whether they are reasonable. WRAB Minutes 21 July 2014 Page No. 4 From Staff: [9:07 p.m.] Flood Briefing: to Council tomorrow night. Follow-up on public outreach regarding proposed rate increases Barker Pipeline US Forest Service permitting agreement going to Council as a consent item tomorrow night. Water Treatment: Equipment issues at both plants have resulted in some difficulties treating water rd at 63, and reduction to a single point of failure system at Betasso water treatment facility. Agenda Item 8 Future Schedule [8:55 p.m.] South Boulder Creek in August. Flood studies in coming months. Adjournment [9:14 p.m.] There being no further business to come before the Board at this time, by motion regularly adopted, the meeting was adjourned at 9:14 p.m. Motion to adjourn by: Squillace; Seconded by: Johnson Motion Passes 5:0 Date, Time, and Location of Next Meeting: The next WRAB meeting will be Monday, 18 August 2014 at 7:00 p.m., in the Council Chambers, 1777 Broadway, 80302. 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. WRAB Minutes 21 July 2014 Page No. 5 C I T Y O F B O U L D E R WATER RESOURCES ADVISORY BOARD AGENDA ITEM MEETING DATE: August 18, 2014 AGENDA TITLE: Public hearing and consideration of a recommendation to City Council regarding the South Boulder Creek Major Drainageway Mitigation Plan. PRESENTER/S: Jeff Arthur, Director of Public Works for Utilities Bob Harberg, Principal Engineer - Utilities Annie Noble, Flood and Greenways Engineering Coordinator Kurt Bauer, Engineering Project Manager EXECUTIVE SUMMARY: The purpose of this memorandum is to provide a summary of the South Boulder Creek major drainageway flood mitigation planning study including the study recommendation. This mitigation plan was initiated in 2010 after the floodplain mapping was updated in 2007. The focus of the study is on developing and evaluating alternatives designed to mitigate flood hazards affecting structures and areas along South Boulder Creek and the West Valley within the current incorporated city limits. A Risk Assessment completed in 2009 estimates that a 100-year storm event would result in approximately $215 million in damages in the South Boulder Creek drainage basin. The September 2013 flood resulted in overtopping of US36 and corresponding flooding through the West Valley with reported damages of $38 million. The 2013 flood is estimated to have resulted in flows above a 50-year event but below the 100-year flow used in the Risk Assessment to estimate damages. Since the major drainageway mitigation study was initiated, multiple flood mitigation alternatives have been evaluated to address flooding associated with South Boulder Creek. The alternatives were screened from fifteen concepts down to four via the planning process. Consultants for the study recommend an alternative that would eliminate the overtopping of US36 during a 100-year event and provide flood protection for 362 structures (893 dwelling units) at a cost of $46 million. The $46 million alternative would include a 560 acre-foot regional flood detention facility, three smaller stormwater detention features at various locations ranging from 9 to 58 acre feet and piping a segment of Dry Creek No. 2 Ditch. The alternative could be constructed in phases ranging from $12 to $23 million. Construction of the project would require numerous federal, state and local permits, agreements with the University of Colorado and Boulder Valley School District, and disposal of Open Space and Mountain Park land. The regional detention facility portion of the alternative would be regulated by the State AGENDA ITEM #____IV____PAGE___1_____ as a high hazard dam. Construction of the regional detention facility at US36 would result in significant impacts to federal and city regulated wetlands, habitat for federally threatened plant and animal species agricultural resources, the South Boulder Creek State Natural Area (SBCSNA) and other environmental and aesthetic resources. Valley Improvements and components of the recommended alternative proceed to the Community Environmental component. While these measures are not as comprehensive as the full recommended alternative, it is anticipated that they could be designed, permitted, funded, and implemented in the relatively near future. Staff recommends seeking additional direction from City Council Council determines that flood mitigation benefits outweigh associated environmental impacts after considering input from the WRAB, the Open Space Board of Trustees, city separate time table. STAFF RECOMMENDATION: Staff requests Water Resources Advisory Board consideration of this matter and recommends action in the form of the following motion: The Water Resources Advisory Board recommends that City Council accept the alternative to mitigate flood risks associated with South Boulder Creek. However, the Water Resources Advisory Board recommends proceeding only recommended alternative at this time. The WRAB recommends proceeding with component of the alternative only if City Council determines that flood mitigation benefits outweigh associated environmental impacts after considering input from the WRAB, the Open Space Board of Trustees, city staff, and the public. COUNCIL FILTER IMPACTS: Economic: A total of 700 structures (442 within city limits) and approximately 1,200 dwelling units (962 within city limits) are located within the 100-year South Boulder Creek floodplain. A risk assessment completed in June 2009 estimated a 100-year event would result in $215 million in damages. South Boulder Creek (SBC) had the drainageways at $38 million. Approximately 362 structures (893 dwelling units) within the city limits would no longer be located in the 100-year floodplain if the study recommendation is constructed (approximately 80 structures would remain in the floodplain within city limits under this alternative). AGENDA ITEM #____IV____PAGE___2_____ Environmental: One of the Boulder Valley Comprehensive Plan general policies buffers to define the community. Construction of the regional detention facility at US36 portion of the study recommendation would impact OSMP land with some of the highest ecological values in the Boulder Valley. The project area on OSMP lies entirely within the SBCSNA which was designated by the State of Colorado in recognition of the state-wide significance of this exceptional riparian and floodplain ecosystem including the - tresses orchid (ULTO) habitat, tallgrass prairie, wetlands, habitat for declining grassland and riparian bird species, habitat for declining amphibians such as the Northern Leopard Frog, and habitat for declining native fish. Tallgrass prairie is considered one of the most endangered plant communities in the world and OSMP land in the project area contains some of the highest quality population is one of the largest within the entire range for this federally threatened plant species. Social: The flood hazards associated with SBC are a risk to life, property and business. Mitigating these hazards would further social sustainability goals and benefit a diverse set of community stakeholders. The areas that would benefit from mitigation contain affordable housing, senior housing, medical facilities, and numerous homes and businesses. . Construction of the study recommendation would result in temporary disruption to local residents, businesses and transportation routes that would be impacted during construction. OTHER IMPACTS: Fiscal: The study recommendation is estimated to cost $46 million. Partial funding ($12.2 million) for this study is included in the Department of Public Works Utilities division budget. The project could be constructed in phases with each phase estimated to cost from $11 - $23 million. The city would seek grant funding for this project. Staff Time: Time for completing the study is included in existing work plans. BOARD AND COMMISSION FEEDBACK: Nine conceptual alternatives were presented to WRAB in December 2010. Staff recommended five alternatives be selected for further refinement and analysis. WRAB motioned to move forward with four of the nine alternatives (a pipe alternative was eliminated) including: 1.Maintaining the status quo; 2.High Hazard Zone mitigation and critical facility protection; 3.Regional detention at US36 with downstream improvements; and 4.Distributed regional detention. Attachment A presents the 2010 WRAB memorandum and corresponding meeting minutes. During the July 21, 2014 information item meeting, WRAB requested that additional background information be presented at the August 21, 2014 agenda item meeting on the original list of nine short-listed alternatives. AGENDA ITEM #____IV____PAGE___3_____ planning process but has not been presented with the preferred alternative. A meeting with the Open Space Board of Trustees is scheduled for August 20, 2014 to present the alternatives as an information item. The Board will be asked to make a recommendation to City Council at a future meeting. PUBLIC FEEDBACK: Conceptual alternatives were initially developed by problem area in a matrix format that included a wide range of mitigation measures. These concepts were then presented at a public meeting held in March 2010 and subsequently screened from input received at the meeting, hydraulic modeling and field visits. The concepts were then combined into 15 Alternative Plans. These alternatives were evaluated and nine Best Alternative Plans were developed and presented at a second public meeting in September 2010. Forty one people responded that mitigating flood risk along South Boulder Creek was very important, eight responded it was somewhat important and three stated they had no opinion. A public open house will be conducted just prior to the August 18 WRAB meeting (5 6:45 p.m.). BACKGROUND: In the mid-1990s the University of Colorado (CU) was evaluating the purchase of land, (the South Campus) located at US36 and Table Mesa. During this evaluation, inaccuracies in the 1986 regulatory flood mapping were discovered. Studies commissioned by the city and the Urban Drainage and Flood Control District (UDFCD) revised the 100-year floodplain and estimated that a 100-year storm event would result in approximately $215 million in damages in the South Boulder Creek drainage basin. South Boulder Creek had the greatest reported property damage from the 2013 flood of (the 2013 flood is estimated to have resulted in flows above a 50-year event but below the 100-year flow used in the Risk Assessment to estimate damages). Additional background information can be found on the project web site (www.southbouldercreek.com) and in the study report (Draft South Boulder Creek Major Drainageway Plan). The South Boulder Creek Flood Mitigation Planning Study began in early 2010 and is being funded by the city and the UDFCD. A consulting team from CH2MHill was selected to perform the study. The study is focused on developing and evaluating alternatives designed to mitigate flood hazards affecting structures and areas within the Attachment A). current incorporated city limits, primarily within the West Valley area ( A draft report has been updated in July 2014 with the executive summary presented as Attachment B . Conceptual alternatives were initially developed by problem area in a matrix format that included a wide range of mitigation measures. These concepts were then presented at a public meeting held in March 2010 and subsequently screened from input received at the meeting, hydraulic modeling and field visits. The concepts were then combined into 15 Alternative Plans. The 15 Alternative Plans are summarized in tabular format as Attachment C . Concept-level sizing, configurations and costs were developed for each of these 15 Plans along with an estimate of likely benefits and environmental and social impacts. From this information, nine Best Alternative Plans were developed. These AGENDA ITEM #____IV____PAGE___4_____ alternatives were presented at a second public meeting in September 2010 and to the Attachment D WRAB in December 2010. presents the 2010 WRAB memorandum that includes a graphical summary of the nine alternatives and a summary comparison of the alternatives. At the December 2010 meeting, staff recommended that five alternatives be selected for further refinement and analysis. WRAB motioned to move forward with only four of the nine alternatives (a large diameter, multi-inlet pipe alternative was eliminated). Attachment D presents the meeting minutes documenting the discussion leading to the WRAB motion. The WRAB motion of short-listed alternatives included: 1.Maintaining the status quo; 2.High Hazard Zone mitigation and critical facility protection; 3.Regional detention at US36 with downstream improvements; and 4.Distributed regional detention. ANALYSIS: Based on further evaluation of the four alternatives recommended by WRAB in 2010, the South Boulder Creek Major Drainageway Flood Mitigation Planning Study recommendation is the Regional Detention at US36 with Downstream Improvements alternative. The alternative is estimated to cost $46 million to construct and includes the following major components: An approximately 75-acre (560 acre-feet of storage) regional flood detention facility located on University of Colorado South Campus land and Open Space and Mountain Parks land. The concept does not impact the current South Campus concept development plan. A 25 acre-foot stormwater storage facility at or near Manhattan Middle School (or alternative location), a 9 acre-foot detention storage area at the intersection of Foothills Parkway and Baseline Road and placing a segment of Dry Creek No. 2 Ditch in a 72-inch diameter pipe. A 58 acre-foot stormwater detention facility at Flatirons Golf Course by constructing earthen berms near Arapahoe Avenue. The recommended alternative would provide 100-year flood protection within the West Valley area at an estimated cost of approximately $46 million and could be constructed in up to the following three separate phases: 1.Regional detention facility at US36 ($23 million); 2.West Valley improvements ($11 million); and 3.Arapahoe Avenue detention ($12 million). Construction of all the phases of the recommended alternative would eliminate overtopping of US36 and subsequent flooding in the West Valley during a major storm event. Approximately 362 structures habitable (893 dwelling units) within city limits would no longer be located in the 100-year floodplain if the study recommendation is constructed (approximately 80 structures would remain in the floodplain within city Attachment E limits) under this alternative. presents the entire study recommendation. Construction of the regional detention facility at US36 phase would provide 100-year Attachment F flood protection to approximately 212 structures as shown in . Construction of the remaining two phases (West Valley improvements and the Arapahoe AGENDA ITEM #____IV____PAGE___5_____ Avenue detention facility) would provide 100-year flood protection to approximately 190 Attachment G habitable structures as shown in . Construction of US36 regional detention facility phase would require numerous permits, agreements with the University of Colorado, disposal of Open Space and Mountain Park land and would be regulated by the State as a high hazard dam. Construction of the regional detention facility would also result in significant impacts to OSMP resources including habitat for threatened and endange -tresses orchid) tallgrass prairie, wetlands, habitat for declining grassland and riparian bird species, habitat for declining amphibians such as the Northern Leopard Frog, and regionally significant agricultural resources and aesthetic resources. This portion of the project would also likely require National Environmental Policy Act (NEPA) compliance and a federal Environmental Assessment (EA) or Environmental Impact Statement (EIS). The city hired ERO Resources to identify likely environmental impacts and corresponding permitting and mitigation measures that would be associated with Table 1.0 constructing the US36 regional detention facility. presents a summary of their Attachment H. findings. presents a summary of the OSMP staff analysis of the impacts Assesment Proce recommended alternative, it is anticipated that they could be designed, permitted, funded, and implemented in the relatively near future. Staff recommends seeking additional City Council determines that flood mitigation benefits outweigh associated environmental impacts after considering input from the WRAB, the Open Space Board of proceed on a separate time table. AGENDA ITEM #____IV____PAGE___6_____ Table 1.0 ERO Summary of Potential Environmental Impacts and Mitigation Options ZĞŐƵůĂƚĞĚWŽƚĞŶƚŝĂů WŽƚĞŶƚŝĂůWĞƌŵŝƚƚŝŶŐͬDŝƚŝŐĂƚŝŽŶ ZĞƐŽƵƌĐĞ/ŵƉĂĐƚƐΎ Up to 9.5 acres Will likely require an Individual Permit due to impacts > 0.5 acres. Waters of the US (3.77 open water, Mitigation option: conversion of Pits D and C (city-owned gravel pits 5.72 wetlands) located on OSMP land) to wetlands would provide up to 22 acres. City-regulated Standard city wetland permit. Mitigation could require a ratio of streams, 1:1 for impacts to open water (3.77 acre) and up to 2.5:1 for high wetlands and Up to 9.5 acres functioning wetlands (up to 14.3 acres of mitigation); city-required water bodies mitigation would also satisfy federal (Corps 404) required mitigation Up to 0.9 acres of Preparation of a Biological Assessment. Relies on project team to PMJM critical set reasonable mitigation standards. Generally requires higher than Threatened and habitat and 6 acres 1:1 mitigation ratio (assumes a 3:1 ratio or 2.7 acres of mitigation Endangered of general habitat; for critical habitat; less for general habitat); mitigation for ULTO = Species assumes up to 10 avoid plants if possible, otherwise project team will work with the acres of potential Service to determine mitigation; wetland mitigation. orchid habitat Nest depredation permit for active nest removal. Avoidance of Migratory birds Up to 23 acres of active nest removal does not require a permit. Nests can be and raptors terrestrial habitat removed outside of the breeding season. *Estimates are conservative as estimated by ERO Resources based on field surveys of wetland and open water and maximum anticipated footprint of the alternative. NEXT STEPS: An open house will be conducted on August 18 from 5 6:45 p.m. to present study information to the public. A meeting with the Open Space Board of Trustees is scheduled for August 20 to present the study information OSBT will be asked to make a recommendation to City Council at a future public meeting. A study session with City Council is tentatively scheduled for September 30. ATTACHMENTS: A. Study area B. Draft South Boulder Creek Major Drainageway Plan Executive Summary C. Tabular summary of original 15 Alternative Plans D. 2010 WRAB memorandum and corresponding meeting minutes E. Study recommendation F. Flood mitigation from Phase 1 of the recommended alternative G. Flood mitigation from Phases 2 and 3 of the recommended alternative H. Open Space and Mountain Parks summary of environmental resources and potential impact AGENDA ITEM #____IV____PAGE___7_____ Attachment A - Study Area Attachment A – Study Area Attachment B - SBC Exec Summary Attachment B – Draft South Boulder Creek Major Drainageway Plan Executive Summary Attachment C - Summary 15 Original Plans Attachment C: Tabular Summary of Original 15 Alternative Plans Attachment D - 2010 WRAB Memo All Attachment D – 2010 WRAB Memorandum and Corresponding Meeting Minutes Attachment D - 2010 WRAB Memo All Attachment D - 2010 WRAB Memo All Attachment D - 2010 WRAB Memo All Attachment D - 2010 WRAB Memo All Attachment D - 2010 WRAB Memo All Attachment D - 2010 WRAB Memo All Attachment D - 2010 WRAB Memo All Attachment D - 2010 WRAB Memo All Attachment D - 2010 WRAB Memo All Attachment D - 2010 WRAB Memo All Attachment D - 2010 WRAB Memo All CITY OF BOULDER, COLORADO BOARDS AND COMMISSIONS MEETING MINUTES Name of Board / Commission: Water Resources Advisory Board Date of Meeting: 14 December2010 Contact Information of Person Preparing Minutes: Laurel Olsen-Horen; 303-441-3203 Board Members Present:Bill DeOreo, Susan Iott, Chuck Howe,Vicki Scharnhorst Board Members Absent: Kate Ryan Staff Present: Ned Williams, Director of Public Works for Utilities Bob Harberg, Engineering Project Management Coordinator Kurt Bauer, Engineering Project Manager Carol Ellinghouse, Water Resources Manager Bret Linenfelser, Water Quality and Environmental Services Coordinator Annie Noble,Greenways Coordinator Laurel Olsen-Horen, Board Secretary Consultants Present: Alan Turner, CH2MHill Project Engineerfor South Boulder Creek Mark Glidden, CH2M HillProject Manager Aaron Cook, CH2M Hill Staff Engineer Alan Taylor, consultant Ronni Sperling, Special Water Counsel to the City Meeting Type: Regular Agenda Item 1 –Call to Order [7:00p.m.] This meeting was called to order at 7:00 p.m. Agenda Item 2–Approval of the 15November2010 Meeting Minutes: [7:02p.m.] Motion to approve by: Iott; Seconded by: Howe Motion Passes; 4:0 Agenda Item 3–Public Participation and Comment [7:02p.m.] Public Comment: None Agenda Item 4–Matters from Board and Staff [7:06p.m.] Matters from Board: Howe brought up the belowmatters: Handed out a copy of an E-mail between him and Reagan Waskom. Iott brought up the belowmatters: When was the last time the city did a rate study? Staff response: the last comprehensive study was done in 2007 Matters from Staff: [7:07p.m.] The Boulder Reservoir Master Plan went to the City Council. City Council approved moving forward with option two (the same option that both WRAB and PRAB recommended). At the November WRAB meeting, the board recommendedthe drought item; however, it will not be presented to Council until February / March Agenda Item 5–Update on South Boulder Creek Flood Mapping Study and selection of short list of alternatives for further evaluation [7:15p.m.] Kurt Bauerpresented item to the board. Executive Summary from Packet Materials: The purpose of this memorandum is to present and discuss the South Boulder Creek flood mitigation alternatives, including a newly developed alternative andselect a short list of best alternatives for further evaluation and consideration. Project alternatives range from maintaining the status quo to providing 100- year flood protection. WRAB discussion included: [7:27p.m.] Clarifying questions: Attachment D - 2010 WRAB Memo All Why did staff settle with five as the final number of alternatives chosen for the short list? Staff response: five seems to give a broad enoughspectrum of possibilities. What is the nature of the disturbance to the neighborhoods with the pipeline options? Staff response: both alternatives with pipelines will cause some disruption. What are the characteristics of the diversion structures for the detention ponds? Staff response: While the specific characteristics have not been developed, the diversion structures will need to be able to divert water, still allow normal creek flow to pass through and allow trails to continue. Are the models specific enough to say what the downstream flow conveyances for the pipeline alternatives will beand how much greater that is than the retention effect we get from the regional holding areas? CH2MHill response: yes, the pipelines will convey the water much quicker to Boulder Creek than the detention alternatives. The detention alternatives are in place to make sure that no additional impacts downstream occur in terms of increased flow ratesor increased velocities in the channel. Public Comment: [7:37p.m.] Ruth Blackmore: Wants to make sure that Alternative Four is truly taken off of the option list. Ms. Blackmore is concerned with alternative five, and would like to know what the OSMP has to say in regards to the potential environmental impact (damage) with creating the berms would be. At a previousUrban Drainage meeting, a rep from Urban Drainage stated that they do not like the use of earthen levies, they do not like piping systems, they would like for the water to flow naturally across the land and that is what the City should tryto do without impacting any individual property. In the Taggart study, they suggested using the land along US 36 since it’s a low lying land. Ms. Blackmore believes that more work needs to be done, but that being said, agrees with the five alternatives proposed by staff. Gary Swanstrom: Would have been one of the properties obtained through eminent domain in alternative four, and thank you to staff for taking it off of the list. John Militzer: Would like to thank staff on their hard work. Mr. Militzer understands why the City is offering a “do nothing” option, however, he would like to see Council find a way to mitigate potential flood issues. Mr. Militzer would like to see staff from the City and the County work together to help the residents upstream and in the valley. Jeannette Hillery: Ms. Hillery would like to know how many structures are going to be taken out of the floodplain. That information would be very helpful to residents in terms of their need to carryFEMAflood insurance. Ms. Hillery would support some disturbance in her neighborhood if it meant that the flood mitigation would benefit the residents and take them out of the floodplain. Vince Wayland: None of the alternatives take Mr. Wayland’s property out of the floodplain. All of the alternatives affect Dry Creek Ditch No. 2. The first five alternatives allinclude creating a 34’ wide channel from a 7’ channel which will have a rather large impact to the homes on each side of the ditch. How does the staff justify minimal neighborhood disturbance? Jim Randa: Mr. Randa’s property abuts the Dry Creek Ditch No. 2. How deep will it be, will it be earthen, and will the expanded ditch be placed on top of the current one? How does the city justify placing a 34’ wide ditch in the place of a 7’ current one? How willthe detention pond at Manhattan Middle School be viewed by the school and usersand what does BVSD think about having a 34’ ditch ontheir property? Peter Ornstein: Would like clarification on the ditch behind Manhattan Middle School. Mr. Ornstein is in support of flood mitigation and believes the City does need to find a way to mitigate major destruction to the community. He would like to have the final FEMA flood studyput on hold pending the complete analysis from the City, so that anotherfloodplain study does not need to be conducted. Ben Binder: Mr. Binder voice disappointment with the number of public meetings offered during this project. People at the public meetings believed that the consultants spent too much time working on options that should have been removed by common sense. Also, Urban Drainage stated that the use of pipelines for flood mitigation is not a good option. Mr. Binder brought up the old Flatiron gravel pits (CU South) as a possible flood mitigation option. The costspresented for the alternatives, were they based on an asking price, or were they actually appraised. Charles Wellman: Mr. Wellman would like to make sure that the board is aware of the actual cost of the presented options. Also, keep in mind how many people the alternatives are really impacting. This needs to be thought of in the human regard, not just the material cost Joanne Turner: would like information on the proposed wall which would be erected on Baseline. Steve Craig: Mr. Craig believesthat the proposed 34’ ditch would block access to the adjacent fields and would be a major disturbance to the neighborhood. Mr. Craig is worried what the ditch Attachment D - 2010 WRAB Memo All would do to his and his neighbor’s property values. A buried pipeline would be preferred over a 34’ ditch. Lauren Noyes: The term “minimal impact” doesn’t seem to be an accurate description ofthe proposed options 3 and 5. Ms. Noyes believes that option 6 should have been kept on the option alternatives. If the 34’ ditch is implemented then Ms. Noyes would nolonger be able to allow for her children to play in the back yard. WRAB discussion: [8:05p.m.] Continuing Clarifying Questions: What is the possibility of the use of CU property to a greater extent? Was there any way we could have used the old gravel pits as a detention area? Staff response: City staff does have a proposal to use part of the CU South property, however the University has indicated that they are not supportive of notching the berm and using the balance of their property. They have other needs for that area, and would thus be considered unwilling sellers. However, alternative 3 does include some useof CU property as a detention area. What does the OSMP staff think of the proposed alternatives? Staff response: what is being presented tonight is a compilation of work done by City staff which does include OSMP, Parks and RecreationandUtilities and the BVSD during numerous discussions. How often will these areas actually contain water? CH2MHill response: the frequency of which these areas will contain water depends on where they are and which ones they are. Some of the areas, (US 36in particular) islikely to see water much more frequently since the channel there is very narrow. The same could be said of the storage at South Boulder Road and Baseline Reservoir because those are on the main channel of South Boulder Creek. As the water flows down, it has a chance to collect and thus flow slower downstream. How long it takes for those detention areas to drain will depend on the size of the flood event. Is it appropriate to delaythe FEMA study until the City completes its study? And at what point wouldthe results of a flood improvement projectget reflected in flood mapping?Staff response: in 2007 the city decided to submitthe revised flood study results to FEMA as best available information. At that time, the City also decided to start regulating thefloodplain areas according to the flood study results. At this point in time, FEMA intends to adopt that study as part of the Digital Flood Insurance Rate Map which has been delayed for a couple of years. The City’s expectation is that FEMA will formally adopt that flood study in late 2011.The results of a flood improvement project would be submitted to FEMA after the construction work was completed. How many facilities will be removed per each alternative? The numbers presented in the table belowinclude residents in both the city and the county and encompassall dwelling types. Number of Alternative Dwellings Numberremoved from floodplain Alternative 10 Alternative 20 Alternative 31,024 Alternative 41,024 Alternative 5810 Alternative 6810 Alternative 7959 Alternative 8947 Alternative 90 What is the possibility of running an underground pipeline rather than a ditch? Staffresponse: staffcould dig deeper into that option based on the recommendation from the WRAB. Why was Alt 6 taken off of the table? Staff response: city staff met with staff from Lafayette, and they are trying to do some minor improvements to Baseline Reservoirand the dam. At this time, if the City put any more water in the reservoir, the State Engineer would require massive upgrades to the Reservoirand dam. The cost for alternative 6 would have been veryexpensive, and there were also some concerns around water qualityas a result of diverting flood water into Baseline Reservoir. The proposed 34’ ditchwould be a grass bottom ditch rather than a concrete ditch with a depth of Attachment D - 2010 WRAB Memo All around four feet. 34’ is the largest width, and the size is not final. How are the monetary benefits determined?Staff response: the $215 million was not a benefit; that number came from a risk assessment from 2009 and was the estimated structural damage (homes, buildings, property) that might occur if a 100 year flood event were to occur. How deep are the Manhattan detention ponds? Staff response: they range from 1-7feet;however this is conceptual at this point. Motionby Iott:To move forward with the staff recommended five options for further evaluation; a friendly amendment by Howe to drop alternative 7 was accepted by Iott.moved byIott;seconded by; DeOreo Vote: 3:1 Scharnhorst voted against the motion stating that Alternative 7 should be included. Agenda Item 6–Final 2011 Goals letter to City Council [9:05p.m.] Susan Iott and ChuckHowe presenteditem to the board. Executive Summary from Packet Materials: At the City Council study session on Boards and Commissions on October 26, 2010, the council spoke several times about the end of year (looking forward to next year) goals and that they would like to receive goals from each of their boards and commissions. An issue that they raised is that the council sometimes receives the list of goals just before the January retreat and this gives them no time to read the goals, much less incorporate them into the work plan. As such, the City Manager’s Office has asked thateach board and commission prepare their list of goals, maybe the top three goals, that they would like council to help them accomplish in 2011 and to submit this written statement not later than January 5, 2011. The annual council retreat will be January 21-22, 2011. At the November 15 WRAB meeting, WRAB designated Susan Iott and Chuck Howe to prepare a draft letter of the goals so that it could be reviewed, revised and approved by the WRAB at the Dec. 14, 2010 WRAB meeting. WRAB discussion included: [9:20 p.m.] General Comments: Drop number 7 off of the list of priorities. Should the priorities be action items, or are they items of high interest? The list should contain both. What should the obligations of the City to those who lose property value as a result of steps taken in the broad public interest? Can Council consider cases like Cordrey Court for example? Public Comment: None WRAB supported the letter and Iott will make the changes and submit to staff. Agenda Item 7 –Update and discussion about wastewater reuse by individual customers [10:20p.m.] Carol Ellinghousepresented item to the board Executive Summary from Packet Materials: Recently, the city has had a few inquiries about possible use of on-site wastewater reuse systems by individual city water customers. These reuse systems would collectwastewater derived from the first use of water in a separate tank for the customer to reuse for a second type of use. Some systems put the wastewater to a second use with little consumption, such as toilet-flushing, and others propose high- consumptive uses, such as secondary use for irrigation. There are both benefits and drawbacks for the city if these reuse systems are installed by city water customers due to the particular configuration of Boulder’s water supply system facilities and water rights portfolio. Issues to consider include: benefits to customers due to reduced water use; possible effects on city water system drought resiliency; changes in return flows to Boulder Creek; risk to city water rights yields; effects on other water rights owners; expense of providing sufficient reusable water in the city water system; impacts of using more Western Slope water; effects on water system operations; impacts to city water revenue; and reduction in hydropower production from Boulder’s water system due to change in water sources. Attachment D - 2010 WRAB Memo All WRAB discussion included: [10:29p.m.] The board expressed concerns aboutentering into a pilot study with CU, as follows: Does the city see any issues with starting a pilot study?Staff response: no, staff believes a pilot study can be successful. Is the city conceding at the very beginning that the recirculation systems and reuse systems are officially effluent reuse, and they constitute injury? Where does the City draw the line, since it’s all domestic use? Staff response: the City has not conceded that a reuse system is injury.This is a pilot program to gather information for future decisions. The mechanical recirculation systemswithin the customer’s premise are still in the dominion and control of the customer, as it has not been returned to the system. Do the water decrees forbid customers from using whatever type of systems are available in their facilities to maximize their water use? Staff response: it’s not about dominion and control;it comes down to the definition of “single use”.When a water supply is used a second time for a different purpose, it is considered to be a reuse of the water. There is not currently any state statute, legislative direction or court decree precedence supporting a definition of a single use of water as including more than the first use for a single purpose or that would include the capture of domestic wastewater from one use for subsequent use for a different domestic purpose. However, Windy Gap water, which is what is being proposed, is decreed for reuse. The City should think about performing a depletion study rather than a pilot study. Staff response: the City has already done that. What is the flexibility of the Windy Gap, and taking it away from CU’s use? Staff response: since the university is investing a lot in the plumbing they would like some kind of commitment beyond the five year pilot study, and at this point the City is not sure what kind of commitment they can give, thus the reason for the pilot study. Could the City exchange Windy Gap water with CBT water? Staff response: there could be specific times when exchange could be possible. Public Comment: None At the current time, staff does not have an IGA to present. If staff and CU proceed with an IGA, then staff is going to recommend starting out with Windy Gap water, and try to recover the additional costs associated with using Windy Gap water. Agenda 8 –Decide on January and February 2011 meeting dates [10:17p.m.] Agenda item 8 occurred out of order on the agenda. thth WRAB selected January 20and February 24 Agenda Item 9–Discussion on Future Schedule [11:12p.m.] At the January meeting – final recommendation on the Boulder Creek Study Update on the Critical Facilities Ordinance Agenda Item 10–Adjournment [11:17p.m.] There being no further business to come before the Board at this time, by motion regularly adopted, the meeting was adjourned at 11:17p.m. Motion to adjourn by: Iott; Seconded by: Scharnhorst Motion Passes 4:0 Date, Time, and Location of Next Meeting: th The next WRAB meeting will be– Thursday, 20 January at 7:00 p.m., specialmeetingdate, at the 13 th Street, unless otherwise decided by staff and the Board. Street Conference Roomlocated at 1720 13 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. Attachment E - Study Recommendation Attachment E – Study Recommendation Attachment F - Phase 1 Attachment F – Flood Mitigation from Phase I of the Recommended Alternative Wellman Ditch Attachment G - Phase 2 and 3 Attachment G – Flood Mitigation from Phases 2 and 3 of the Recommended Alternative Wellman Ditch Attachment H - OSMP Summary Attachment H – Open Space and Mountain Parks Summary of Environmental Resources Attachment H - OSMP Summary APPENDIX H Environmental resources of South Boulder Creek and potential resource impacts of the US 36 with Downstream Improvements flood mitigation alternative A number of issues were assessed during the evaluation process of the flood mitigation alternatives in addition to the financial and flood control elements implicit in the evaluation. The Regional Detention at US36 with Downstream Improvements alternative was further evaluated by city staff and the public for impacts to resources on OSMP land. The West Valley improvements and Arapahoe Avenue detention components of this alternative will not impact resources on OSMP land. The regional detention facility at US36 component will impact OSMP land with high value ecological resources including: Wetlands that are considered to be among the best preserved and most ecologically significant in the Boulder Valley. An important population of the federally threatened Preble’s meadow jumping mouse. An important occurrence of the federally threatened Ute ladies’ tresses orchid. A population of northern leopard frog, a species experiencing marked declines along the Front Range and classified as sensitive in nine Western US states. Populations of two native fish species in decline in Colorado, plains topminnow and orange-spotted sunfish. A population Bobolink, a declining grassland nesting bird. An important remnant of the plains cottonwood riparian ecosystem. Relicts of the tallgrass prairie ecosystem. Wetlands : Extensive high-quality wetlands and riparian areas exist throughout the South Boulder Creek floodplain, including riparian forests, willow shrublands, freshwater marshes and wet meadows. These wetlands are considered to be among the best preserved and most ecologically significant in the Boulder Valley. Several of these wetland types provide refuge for rare species such as Preble’s meadow jumping mouse, Ute ladies-tresses orchid, groundnut and toothcup, while others are rare or imperiled on a statewide or global scale. A regional detention facility at US36 would impact this resource via direct burial of wetlands and the possible alteration of the hydrology of adjacent wetlands. An additional undetermined area will be temporarily impacted from construction activities. Wetland permits would be required from the city of Boulder and the US Army Corps of Engineers for this project. Mitigation would be necessary for all unavoidable impacts. Preble’s Meadow Jumping Mouse: This species is listed as threatened under the Endangered Species Act. Research by Carron Meaney (biologist with Walsh Environmental and co-author of Mammals of Colorado) and others found extremely high densities of Preble's in the South Boulder Creek floodplain (one of highest densities anywhere in their range). In recognition of the importance of this habitat for the overall conservation and recovery of this species, the US Fish Attachment H - OSMP Summary and Wildlife Service designated critical habitat as occurring 140 meters (460 feet) adjacent to the South Boulder Creek channel. In their description of the area in the Federal Register, the USFWS states "A wide floodplain, complex ditch system, and the irrigation of pastures makes the lower portions of this unit unique". In addition to the habitat included in the critical habitat area, Preble’s use areas further from the stream including irrigated fields, ditch corridors and upland grassland. PMJM has been recently trapped along South Boulder Creek and in the adjacent mesic tallgrass prairie south of US36. This area is also considered occupied habitat. A regional detention facility at US36 will directly impact Prebles habitat and may also contribute to fragmentation of remaining habitat by creating barriers to movement to and from suitable habitat. Ute Ladies’ Tresses Orchid: Ute ladies’ tresses orchid is a wetland plant designated as threatened under the Endangered Species Act. In Colorado, the orchid is restricted to low elevation valleys in wetlands, riparian areas and irrigated fields. Within these sites, it is found only in specialized conditions of soil and hydrology. The populations of the orchid on OSMP lands are among the largest and most important to the conservation of this species throughout its range. The largest populations on OSMP are found immediately south of US 36 where the mosaic formed by mesic bluestem prairie (a globally rare plant community) and wetlands occur. Monitoring by OSMP staff has documented over 3,000 orchids in this area. Smaller numbers of the orchid are found adjacent to South Boulder Creek. Thedetention facility at US36would impact this resource via direct burial of orchid plants and orchid habitat and the possible alteration of the hydrology of adjacent wetlands and mesic bluestem prairie. An additional undetermined area will be temporarily impacted from construction activities. Northern Leopard Frog: Populations of the northern leopard frog in the Western US are in marked decline, suffering local extinctions in some areas, including the Front Range. They are classified as a species of interest in nine western states as well as considered sensitive by the Bureau of Land Management and the US Forest Service. Numerous interacting threats have disrupted the frog’s ecology. These include: habitat loss and degradation, pesticide use, fungal pathogens, the spread of non-native species like predaceous fish and bullfrogs into otherwise suitable breeding habitats, changes in the hydrological regime (which allows completion of bullfrog’s reproductive cycle), and increased variability in temperature and precipitation. The decline of this species in Boulder County is well documented. Despite recent population declines, leopard frogs are still consistently found in a number of wetland and aquatic habitats on OSMP, including those along South Boulder Creek. In 2011, OSMP staff documented a northern leopard frog breeding site in wetlands near South Boulder Creek. These local populations contribute to the conservation of this species throughout its declining range. Attachment H - OSMP Summary Native fish and ground-nesting birds: Plains topminnow and orange-spotted sunfish, two native fish species in decline in Colorado and state species of special concern have been documented in South Boulder Creek in the project area. The wet meadows and tallgrass prairie adjacent to SBC provide habitat for bobolink, a declining grassland nesting bird. This species is considered “vulnerable to extirpation” (“S3B”) by the Colorado National Heritage Program and a “rare breeding species” by the Boulder County Comprehensive Plan. Habitat for these species in the SBC floodplain will likely be degraded or destroyed by a detention facility at US36. Other Environmental Values South Boulder Creek State Natural Area (SBCSNA): The Colorado Natural Areas Act established a statewide Colorado Natural Areas Program to provide a means by which specific examples of Colorado's natural features and ecological phenomena can be identified, evaluated and protected through a statewide system of designated natural areas. Designation of the SBCSNA provides statewide recognition of the important natural features in this area. The Colorado Natural Areas Council has determined that the South Boulder Creek floodplain qualifies as a state natural area because of the presence of a number of important biological resources including an importantremnant of the plains cottonwood riparian ecosystem and relicts of the tallgrass prairie ecosystem in addition to the resources listed above. Tallgrass prairie is considered one of the most endangered plant communities in the world and OSMP land contains some of the highest quality remaining tallgrass prairie in the state and the region. The project area on OSMP lies entirely within the SBCSNA. Agricultural Resources: The South Boulder Creek floodplain supports some of the richest agricultural lands in the OSMP system with cattle grazing and hay production the primary agricultural uses. Much of the land is flood irrigated with long-standing water rights. Irrigation infrastructure is common throughout the area to distribute this water efficiently across the landscape. A detention facility at US36 would destroy irrigated pasture because of the inability to continue irrigation practices. While parts of the berm could continue to be grazed, forage production would also be lower because of lack of irrigation. A berm could not be hayed due to its steep sides and hay production would be eliminated. Some irrigation infrastructure would need to be relocated and rebuilt to move irrigation water across the land efficiently. Weeds: A berm south of US36 would create good habitat for many weedy species and a difficult surface topographically for most weed treatment strategies. OSMP would likely be committed to long-term herbicide use to control weeds on the berm which would conflict with the City’s IPM policies. The berm would be a poor quality island patch that would create a long-term threat to the remaining wet meadow and mesic tallgrass habitat in the adjacent OSMP areas. Attachment H - OSMP Summary Scenic Resources: A detention facility at US36 will have scenic impacts for visitors to OSMP lands. The height of the berm will vary depending on local topography and other factors. This structure will create visual impacts due to its height, shape, linear nature and presence in an otherwise semi-natural setting. Depending on viewing perspective, views of the riparian area, agricultural fields and the mountain backdrop will be affected. The Open Space and Mountain Parks provisions in the City of Boulder Charter define specific uses for OSMP land. The potential construction of a detention facility and berm at US36 appears to conflict with OSMP charter purposes by impacting land with high ecological, agricultural, scenic and recreational values. The extent, proximity, association and significance of these rare resources are found in very few other places in the world. These potential losses are significant and may not be easily mitigated, replaced or restored. C I T Y OF B O U L D E R WATER RESOURCES ADVISORY BOARD AGENDA ITEM MEETING DATE: August 18, 2014 AGENDA TITLE: Information Item - Skunk Creek Floodplain Mapping Update PRESENTER/S: Jeff Arthur, Director of Public Works for Utilities Bob Harberg, Principal Engineer - Utilities Annie Noble, Flood and Greenways Engineering Coordinator Katie Knapp, Engineering Project Manager EXECUTIVE SUMMARY The purpose of this memorandum is to provide a general summary of the history and results of the Skunk Creek Floodplain Mapping Update. Floodplain mapping provides the basis for flood management by identifying the areas subject to the greatest risk of flooding. This information is essential for determining areas where life safety is threatened and property damage is likely and is the basis for floodplain regulations and the National Flood Insurance Program (NFIP). floodplain maps need to be periodically updated to reflect changes in the floodplain resulting from land development, flood mitigation improvements, new topographic mapping information and new mapping study technologies. The Skunk Creek Floodplain Mapping Update includes the lch, Skunk and Bluebell Canyon Creek floodplains between the city limits to east of Foothills Parkway where Skunk Creek confluences into Bear Canyon Creek as shown in red below. AGENDA ITEM #__V_____PAGE____1____ Engineering consultants provided hydraulic modeling to update the existing Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) and City of Boulder floodplains, water surface elevations, conveyance and high hazard zones. The proposed mapping of the Skunk Creek Floodplain would result in a net: Increase of 49 structures identified in the 100-year floodplain; Decrease of 25 structures identified in the conveyance zone and; Decrease of 14 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. Following input from the August WRAB meeting, any information requested about the mapping study will be presented at the September WRAB meeting. A request for a motion will also be made at the September WRAB meeting. BOARD AND COMMISSION FEEDBACK The Skunk Creek floodplain mapping update has not been brought to any Boards or Commissions prior to WRAB. Following input from WRAB, the mapping update will be presented to City Council. PUBLIC FEEDBACK Public notification post cards about the mapping update have been sent to all property owners in the study area and a project web site has been developed to provide information (https://bouldercolorado.gov/water/skunk-creek-floodplain-mapping-update). An open house meeting is being held immediately prior to this WRAB meeting to inform the public about the mapping update. A summary of public input gathered at the open house will be provided at the September WRAB meeting. AGENDA ITEM #__V_____PAGE____2____ BACKGROUND The risk of flash flooding is an important issue for the City of Boulder primarily due to its location at the mouth of Boulder Canyon and other canyon creeks. Approximately 13 percent of the city is located within the 100-year floodplains of Boulder Creek and its 14 tributaries. Floodplain Management floodplain regulations and flood insurance can be found at: Overview. The city delineates four flood zones: 500-year floodplain: The 500-year floodplain delineates the flood limits resulting from a storm that has a 0.2 percent chance of occurring in any given year. 100-year floodplain: The 100-year floodplain delineates the flood limits resulting from a storm that has a one percent chance of occurring in any given year (26 percent chance over a 30-year mortgage). Conveyance zone: The conveyance zone is defined as the areas in the floodplain that are reserved for the main passage of the entire 100-year flood flow when the 100-year floodplain is artificially narrowed until a maximum six-inch increase in flood water depth is created. This zone is delineated to allow development to occur up to the narrowed floodplain and still provide passage of 100-year storm flows. High hazard zone: The high hazard zone defines the area of the floodplain where water depth and velocity pose a threat to life and safety. This area is delineated for areas in the floodplain where water depths are four feet or greater or where the water velocity multiplied by water depth equals or exceeds the number four. Skunk Creek, Bluebell Canyon Creek, and Kings Gulch were first studied in 1987 by the consulting firm Greenhorne & O'Mara and the resulting Flood Hazard Area Delineation (FHAD) report included the delineation of the 100-year floodplain along these creeks. The Flood Insurance Study (FIS) and Flood Insurance Rate Map (FIRM) approved for these creeks were originally based on the 1987 FHAD and included a federally-regulated one foot rise floodway. Since that time, both the City of Boulder and the State of Colorado have adopted a ½ foot rise floodway, which the City refers to as the Conveyance Zone. In 1989, Love and Associates delineated the High Hazard Zone and City of Boulder Conveyance Zone (½ foot rise floodway). The delineations were based on the hydraulic models used in the 1987 FHAD. On May 6, 1991, FEMA issued a Letter of Map Revision (LOMR) for Skunk Creek to incorporate the results of a channel improvement project. The limit of the LOMR was in the Universi upstream of the confluence of Boulder Creek. AGENDA ITEM #__V_____PAGE____3____ Several road-crossing structures for Skunk Creek have been improved since the regulatory floodplain was adopted in 1991. Culverts at Broadway and at 27th Way, crossings at Anderson Ditch and the cemetery maintenance road, and the low water crossing upstream of 27th Way were not included in the 1991 regulatory model, but were incorporated into the current mapping study. The City initially contracted with Belt Collins to develop the updated floodplain maps but they closed their Boulder office in 2013. ICON Engineering provided a peer review of 1 initial study and was selected to complete the project. In 2013, the city acquired state-of-the-art Light Detection and Ranging (LiDAR) technology to produce high-resolution topographic mapping. The new LiDAR mapping was compared to the 2003 topographic base mapping and areas showing substantial differences were updated in the hydraulic models. ANALYSIS This mapping study updates the hydraulic models and flood hazard mapping for the 100- year floodplain, Conveyance and High Hazard Zones for the entire reach of Skunk Creek, including the and Bluebell Canyon Creek tributaries. A 2-dimensional hydraulic model was developed for the creek system to determine primary flow paths and split flow areas. Information from the 2-dimensional model was -dimensional hydraulic model used for the analysis. The existing 100-year floodplain Creek is primarily along the creek corridors and roadway areas with some spillage into surrounding properties. The proposed 100-year floodplain is more extensive than the existing mapping in most areas and bears resemblance to the September 2013 flood extents. The September 2013 flood extents were not used to delineate the floodplains but were used to check assumptions on flow paths. For Skunk Creek Bluebell Canyon Creek, the September 2013 flood extents are similar to the proposed floodplain mapping. The existing Conveyance and High Hazard Zone mapping for Bluebell Canyon Creek did not include a significant neighborhood area that has a history of th flooding east of 15 Street. The proposed mapping extends the Conveyance and High Hazard Zones through this residential area to their confluence with Skunk Creek along Broadway. The proposed mapping also extends the Conveyance and High Hazard Zones for Skunk Creek north of Broadway to include more roadways, split flows and other areas not previously mapped. The revised mapping indicates that the flood risk impacts more structures in the Skunk Creek Drainage Basin than was shown in the previous mapping. A majority of the th structures newly identified as being at risk are located within the bounds of 15 Street to AGENDA ITEM #__V_____PAGE____4____ the east, Broadway to the west, Baseline to the north and King Avenue to the south. This area experienced significant damage during the September 2013 flood. Attachments A through D present figures showing a comparison between existing and proposed floodplain mapping. A summary of how these changes impact existing Attachment E structures is included in . NEXT STEPS: Following input from the August WRAB meeting, any information requested about the mapping study will be presented at the September WRAB meeting. A request for a motion to approve the new mapping will also be made at the September WRAB meeting. The WRAB review of the floodplain mapping update does not require board members to verify analysis and calculations, but indicates the overall mapping study process and results are reasonable and acceptable. Following input from the September WRAB meeting, the mapping revisions will be considered by City Council. If City Council approves the map revisions, the city will submit a request to FEMA for review. During the FEMA review and approval process it is recommended that the new mapping be used for regulatory purposes by regulating to the more restrictive of the existing and proposed mapping. This would mean that development within the newly identified flood zones would be subject to the city floodplain regulations. In order to comply with FEMA requirements, development within the areas that are being removed from the floodplain would still be subject to the Following formal adoption by FEMA, the city would regulate solely based on the new mapping. ATTACHMENTS A.Existing and Proposed 100-Year Floodplain B.Existing and Proposed Conveyance Zone C.Existing and Proposed High Hazard Zone D.Summary of Impacts to Existing Structures AGENDA ITEM #__V_____PAGE____5____ 22nd St 22nd St 22nd St Attachment D Skunk Creek, Bluebell Canyon Creek and Kings Gulch Floodplain Mapping Revisions The tables below present a summary of how the proposed floodplain mapping revisions impact existing structures. Summary of Proposed Changes Skunk Creek Number of Structures 100-Year Floodplain Conveyance Zone High Hazard Zone Existing Floodplain 178 81 31 Proposed Floodplain 221 56 17 Change No Longer Affected 56 53 23 Newly Affected 108 28 9 No Change 122* 28 8 *There are (9) LOMRs which exclude structures from the 100-year floodplain