HomeMy WebLinkAbout5 - Presentation and discussion of the Fourmile Canyon and Wonderland Creek Major Drainageway PlanniCITYOF BOULDER
WATER RESOURCES ADVISORY BOARD
AGENDAITEM
MEETING DATE: October 15, 2007
AGENDA TITLE:
Presentation and Discussion of the Fourmile Canyon and Wonderland Creek Major
Drainageway Planning Phase A Report - Alternative Analysis
PRESENTERS:
Eric Lessard, Engineering Project Manager
Bob Harberg, Utilities Planning and Project Management Coordinator
WATER RESOURCES ADVISORY BOARD ACTION REQUESTED:
The Phase A Report presents information regarding flood mitigation planning. City staff has
coordinated the flood mitigation planning with various internal departments and presented the
report to the Greenways Advisory Committee. An open house for the affected citizens has
been held and comments were solicited. The purpose of this agenda item is to provide an
opportunity for the public to speak to this issue and inform the board regarding the report and
consultants recommendations. Staff will return to the boazd with their recommendations at a
subsequent meeting after considering public and board comments and request a
recommendation to City Council regazding the adequacy of the report and recommendations.
FISCAL IMPACT:
The flood mitigation plan recommended by the consultant, Love & Associates, and endorsed
by the Urban Drainage and Flood Control District is estimated to have a total cost of
$45,676,000 of which $36,552,000 would be at public expense and $9,124,000 would be borne
by private property owners. Private property owners would not be required to beaz this expense
but would be encouraged to protect their property from future flood damages. Significant total
benefits of over $6Q000,000 are estimated based on a reduction in total property damage due
to future flooding.
City of Boulder
Fourtnile Canyon and Wondedand Creek Phase A Report
October 2007
EXECUTIVE SUMMARY:
The Fourmile Canyon Creek and Wonderland Creek Major Drainageway Planning - Phase A
Report - Alternatives Analysis (Phase A Report) focuses on the development, evaluation, and
recommendations of alternatives to mitigate future flooding in both the Fourmile Canyon Creek
and Wonderland Creek flood hazard azeas within the City of Boulder (City) and Boulder County.
The work was jointly sponsored by the Urban Drainage and Flood Control District (UDFCD)
and the City of Boulder, Colorado. The Phase A Report was prepazed by the consultant Love &
Associates. The Phase A Report presents information regazding flood mitigation planning. City
staff has coordinated the flood mitigation planning with other objectives of the Greenways
Program and presented the report to the Greenways Advisory Committee. An open house for
affected citizens has been conducted also. The purpose of this agenda item is to solicit any
additional comments and input on Phase A Report from the Water Resources Advisory Board
(WRAB).
The Phase A report evaluates a number of alternate drainageway planning concepts to mitigate
existing flood damages, taking into consideration the impacts of the spill flows from Fourmile
Canyon Creek to Wonderland Creek. The study is divided into two phases. The first phase
(Phase A) is the initial report that covers the hydrologic, hydraulic, and alternate evaluation
aspects of the project. The future, second phase (Phase B), will cover the preliminary design of
the selected alternates.
A complete copy of the Phase A report is available at:
http://www.bouldercolorado.eov/index.php?option=com content&task~iew&id=4976&Itemid
=2104 •
BACKGROUND:
The study area includes the Fourmile Canyon Creek floodplain from the mouth of the canyon to
its confluence with Boulder Creek and the Wonderland Creek floodplain from downstream of
Wonderland Lake to its confluence with Goose Creek. Additionally, the Fourmile Canyon Creek
spill floodplain, located between Fourmile Canyon Creek and Wonderland Creek, upstream of
Broadway approximately to 19th Street, is also included.
Major drainageway planning documents were previously developed for Fourmile Canyon Creek
and Wonderland Creek by Greenhorne & O'Mara, Inc in the mid 1980s. Due to development
that occurred in the floodplain and better floodplain information, the City of Boulder
commissioned a re-study of the Fourmile Canyon Creek floodplain and the Wonderland Creek
flood hazazds. The study is based on detailed 2003 aerial mapping and new hydrologic analysis
techniques. Love & Associates was retained by the City to prepare a Letter of Map Revision
(LOMR) submittal to FEMA for these two streams. The LOMR was developed during 2004-
2005 and approved by various City Boards and the City Council in early 2006. The LOMR was
submitted to FEMA in March, 2006 and approved in November, 2006. The new flood hazard
azeas became regulatory following the end of the public appeal period in late Mazch, 2007.
C~ty of Boulder
Fourtnde Canyon and Wonderland Creek Phase A Report
Ocrober2007
The initial flood mitigation planning effort began in June of 1999. Both a Phase A and Phase B
study were completed for Fourmile Canyon Creek. Following the review and input from the
Independent Review Panel (IRP) comprised of floodplain experts in 2000, it was recommended
that a combined Phase A Altemate Analysis report should be undertaken for both Fourmile
Canyon and Wonderland Creek. Subsequent to the completion of the LOMR, the combined
Alternate Analysis began in the Fall of 2006. Since that time, a series of internal progress
meetings have taken place to exchange information and discuss ideas and findings of the
combined study. The progress meetings were regulazly attended by representatives of the City
and UDFCD.
ANALYSIS:
The flood analysis for these two creeks indicated significant differences from the original FEMA
regulatory studies, resulting in additional properties being located within the two floodplains. Of
particulaz importance, the re-study identified reaches of Fourmile Canyon Creek west of 19th
Street, where, once the channel capacity is exceeded, flood flows overtop the south bank of the
creek and flow in a southeasterly direction towards Wonderland Creek. These "spill flows"
result in a reduction of flows in Fourmile Canyon Creek downstream of 19th Street but also
result in an increase in the flows in Wonderland Creek. During the 100-year flood event,
approximately 3,300 cubic feet per second (cfs) is in Fourmile Canyon Creek neaz the mouth of
the Canyon, of this amount approximately 1,600 cfs will overtop the south bank spill and flow
towazd Wonderland Creek. The remaining 1,700 cfs will remain in the Fourmile Canyon Creek
ChanneL Likewise, the 100-yeaz dischazge in Wonderland Creek significantly increases
downstream of the spill inflow. Some of the spill returns to Fourmile Canyon Creek near 19th
Street but the majority remains in the Wonderland Creek floodplain. Early in the study, a broad
range of alternates were identified. These alternates were screened following an analysis of each
stream and detailed discussions held during progress meetings on a reach by reach basis, for each
stream. A wide array of options were looked at as potentials for mitigation of the flooding,
ranging from a`do-nothing' status quo altemate to construction of a 100-yeaz flood channel for
each stream thereby confining the spill from Fourmile Canyon Creek.
Alternates
The altemates considered for both streams included a High Hazazd Containment and
Floodproofing of Structures alternate. Original alternates considered in the initial Fourmile
Canyon Creek Major Drainageway Master Plan also included both a 50- yeaz and 100-yeaz
channel alternate.
The 100-year channel would be designed by an inter-disciplinary team of engineers,
geomorphologists and biologists to emulate a natural channel. This alternate would eliminate
spills from Fourmile Canyon Creek to Wonderland Creek during the 100-yeaz or smaller flood
event. The channel would be designed to UDFCD and CiTy criteria with FEMA and City
required freeboard. The 50-yeaz alternate for Fourmile Canyon Creek (only) would contain the
100-year flows but would have no freeboard built into the design. T'he Urban Drainage and
Flood Control District, based on legal opinion from its counsel, has indicated reluctance to
C~ry of Boulder
Fourmde Canyon and Wonderiand Creek Phase A Report
October 2007
participate in any Altemate which includes containment or reduction of the Fourmile Canyon
Creek spill unless downstream property owners' concerns are properly addressed.
The High Hazard Zone is defined as those areas where the product number of velocity (measured
in feet per second) times flow depth (measured in feet) equals or exceeds four, or where flow
depths equal or exceed four feet. These portions of the 100-yeaz floodplain pose an unacceptably
high hazazd to human saFety. In the high hazazd zone, the construction, expansion ar
enlargement of any structure intended for human occupancy or establishment of a new parking
lot is prohibited. The High Hazard Containment alternate would remove structures identified in
either stream from the City's High Hazazd Flood Zone through direct purchase of the property,
the enlargement of road crossing structures, channel excavation, and/or floodproofing or a
combination thereof. This alternate does not eliminate the out of channel bank floodplain;
however, it reduces flood levels to those structures in the High Hazazd Zone for increased safety
when evacuating occupied buildings and allows for emergency access to residential structures.
Floodproofmg is a combination of adjustments and/or additions of physical features installed in,
on or around individual structures designed to eliminate or reduce the potential for flood damage
to the structure. Floodproofing consists of the techniques and approaches for preventing or
minimizing flood damages to a struchue and its contents in flood hazazd azeas. Floodproofing
techniques range from: the constnxction of levees and flood walls azound a structure, to installing
water-tight doors and windows, physically raising the structures elevation using fill or pilings,
measures designed to reduce water seepage and/or resist lateral pressure from flood water in the
structure, etc. Floodproofing measures may be applied to new structures as well as retrofitting
existing structures which may allow for development within the floodplain in low hazard areas.
The purpose of floodproofing is to minimize flood damages by either keeping floodwaters away
from damageable property or making the property less susceptible to damages when floodwaters
reach the structure. Floodproofing does not eliminate all flood damages but can, if done
correctly, significantly reduce damages from flooding. The City may offer guidance and
disseminate information regarding various floodproofing techniques; however, it would be the
responsibility of the individual property owner to implement this alternate for their own
individual properties.
Alternates proposed are compared to the Status Quo or Maintain Existing Conditions alternate.
Maintain existing floodplain configuration would adopt the new floodplain mapping without
proposing mitigation improvements at this time. Additional non-structural methods including
flash flood forecasting, warning systems and evacuation plans would also be recommended for
implementation. Flood insurance and floodproofing of struchues would also be recommended
(at the individual property owner's expense). Floodplain regulations would be strictly enforced.
Post flood relief would be provided. This alternate requires no new City funding, but may
sacrifice opportunities to greatly improve Fourmile Canyon Creek and mitigate flooding in the
future.
Financial Considerations
C~ry of Boulder
Fourmde Canyon and Wonderland Creck Phase A Report
October 2007
Reach by Reach cost estimates were prepared for the each of the alternates analyzed (five in the
Fourmile Canyon Creek floodplain and four in the Wonderland Creek floodplain). Each of the
alternates analyzed for both streams will still incur an expected damage during flood events.
Examples of these damages would include isolated bank erosion locations in the constructed
"natural" channel alternate or wide spread damage in the maintaining of the existing floodplain
configuration alternate.
One method commonly used to compare alternatives is the benefiUcost (B/C) ratio. In general,
the higher the B/C ratio the more cost effective is an alternate. In this study, the benefiUwst
ratio compares the total cost to implement a flood control alternative with the benefits that would
be realized if that flood control alternative were implemented.
A B/C ratio greater then one (1) indicates the benefit received is greater then the cost to
implement the alternative. A B/C ratio equal to one (1) indicates the benefit received is the same
as the cost to implement the alternative. A B/C ratio less then one (1) indicates the benefit
received is less then the cost to implement the alternative. Details of the financial analysis
including the benefit/cost analysis aze presented in the Phase A Report.
Intangible Benefits (Greenways Objectives)
There aze numerous intangible benefits that would azise from the implementation of flood
mitigation improvements. Many of these intangible benefits are related to other Greenways
Program objectives. The intangible benefits that may be realized through flood mitigation
include the following:
Improved traffic movement during floods
Improved emergency response
Improved recreation and alternative transportation
Improved public health and safety including life safety due to flash flooding
Improved environment, water quality and riparian habitat
Lower flood insurance for private property owners
Increased property values
Creation of urban open land
Creation of cultural, educational, and scientific resources
Intangible benefits have not been quantified from a monetary perspective and included in the
benefiUcost analysis. As a result, the benefiUcost ratios aze lower than what would be realized if
dollar values were placed upon the intangible benefits.
Bigger floods can and will occur. This statement holds true whether you are talking about a 10-
year, 100-year or 500-year flood event. The Fourmile Canyon Creek and Wonderland Creek
drainageways have not had a significant flood in the recent documented past. The public
awareness of the significance of the flood situation is low since many of the residents in the
floodplain have not seen the results of a disaster, or had to clean up after a flood in their
neighborhood ar experienced the injury to or loss of a family member or friend in a flood event.
C~ty of Boulder
Fourmile Canyon and Wonderland Creek Phase A Acport
October 2007
CONSULTANT RECOMMENDED ALTERNATE:
Love & Associates, Inc. has recommended a combination alternate for both Fourmile Canyon
Creek and Wonderland Creek. For each creek, the recommended alternate consists of a
combination of the 100-Year Channel, High Hazazd Containment, Floodproofing and Maintain
Status Quo. The recommended alternates were developed utilizing a reach-by reach approach.
Complete documentation is included in the study document and summarized in the Executive
Summary and Alternate Maps presented as Attachment A and B.
The Love & Associates recommendation also makes the point that it is important to realize the
Fourmile Canyon Creek and Wonderland Creek floodplains are hydraulically connected. Due to
topography and the limited channel capacity of Fourmile Canyon Creek, spills from Fourmile
Canyon Creek flow into the Wonderland Creek floodplain. Decisions made on floodplain
management and mitigation within the Fourmile Canyon Creek floodplain have a direct impact
on the Wonderland Creek floodplain. All development within the existing floodplain should be
in accordance with the City, County and Federal permitting requirements.
The flood mitigation plan recommended by Love & Associates is estimated to have a total cost
of $45,676,000 of which $36,552,000 would be at public expense and $9,124,000 would be
borne by private property owners. Private property owners would not be required to bear this
expense but would be encouraged to protect their property from future flood damages.
Significant total benefits of over $60,000,000 are estimated based on a reduction in total property
damage due to future flooding.
UDFCD SELECTED PLAN:
The UDFCD has developed a draft selected plan and presented as Attachment C. The selected
plan endorses the Love & Associates recommendations and provides additional direction to be
considered.
INTERNAL STAFF INPUT:
Utilities Planning and Project Management staff have responded to solicited input received from
other internal city departments and work groups. This information is presented in Attachment D.
OPEN HOUSE & PUBLIC INPUT:
Utilities Planning and Project Management staff have solicited input and received a number of
comments from the public during the open house conducted on September 27. This information
is presented in Attachment E. In addition, based on the number of similaz questions asked during
the Open House, staff has prepazed a Frequently Asked Questions document that is contained in
Attachment F. Finally, a newsletter was created to facilitate the public process and provide
citizens with a quick summary of activities related to the Phase A report. This document is
attachment G.
NEXT STEPS:
City of Boulder
Fourmde Canyon and Wondedand Creek Phase A Report
Ocrober 2007
The report contains a lazge amount of information. Thus, following the presentation of the Phase
A report, a second meeting with WRAB will be scheduled to follow up on discussions generated
during the presentation on October 15. A public hearing with the Planning Board and City
Council aze anticipated in early 2008.
Following the selection of the preferred mitigation plan, the Phase B- Preliminary Design will
be initiated and should be completed in 2008. The preliminary design will be reviewed as part of
the city's Community and Environmental Assessment Process (CEAP).
Money has been budgeted in the 2008-2013 Capital Improvement Program (CIP) budget to begin
to fund selected flood mitigation work. It is likely complete implementation of the selected flood
mitigation plan will take several decades to complete.
STAFF REQUEST:
Staff requests input from the WRAB on the flood mitigation plan and the selection of
recommended alternates. If you wish to provide input subsequent to the WRAB meeting, please
contact Eric Lessard via phone at 303-441-4232 or e-mail lessarde(a),bouldercolorado.gov
ATTACHMENTS:
A Phase A Report - Executive Summary
B Recommended Alternate Maps
C UDFCD Draft Selected Plan
D Internal City Staff Review Comments and Response
E Open House Public Input
F Frequently Asked Questions
G Newsletter
QTy of Boulder
Fourtnile Canyon and Wondedand Creek Phase A Report
Oc[ober 2007
FOURMILE CANYON CREEK AND
W ONDERLAND CREEK
MASOR DRAINAGEWAY PLANNING
PHASE A REPORT
ALTERNATIVES ANALYSIS
EXECUTIVE SUMMARY
The development, evaluanoq and recommendatmn of Floodplam alternatrves to mmga[e ewsnng
floodmg m both the Fourtnde Canyon Creek and Wonderland Creek floodplams wrthm Ihe Ciry of
Boulder (City) and Boulder Counry are presented m this report Th~s effort ~s ~omtly sponsored by the
Urban Dramage and Flood Con[rol D~sVic[ (UDFCD) and the C~ry of Boulder, Colorado
Puroose end Obiectives
'!he purpose of the study ~s to analyze the exatmg and future dramage wndrtions wnhm both the
Fourmde Canyon and Wondedand Creek Floodplams, develop altema[e dramageway plamm~g concepis
m mrtigate exrsnng flood damages takmg mto consideranon the impacts of the sp~ll flows from Fourtnde
Canyon Creek ro Wonderland Creek, and prepare a prehmmary design of an altemanve selected by ihe
Prqect Sponsors The study ~s drvided into two phases The first phase (Phase A) of which this report ~s
a part covers the hydrologm, hydrauhc, and altema[e evaluanon azpects of the pro~ect The second phase
(Phase B) wdl wver the prelimmary design of Me selected altema[e(s)
Plannine Process
The ~mnal plannmg effort began m lune of 1999 and both a Phase A and Phase B smdy were complered
Cor Fourmde Canyon Creek Followmg [he review and mput from the Independent Aeview Panel (IRP)
compnsed of floodplam experts m 200Q rt was recommended that m order ro develop a more complete
solut~on for floodmg on Fourm~le Canyon Creek, a combmed Phase A Altemate Malys~s report should
be undertaken as a combmed sNdy oC both Foutmde Canyon and Wondedand Creeks Th~s combmed
Alternate Analys~s began m the Fall of 2006 Smce [hat [~me, a senes of pmgress meehngs have taken
place to exchange mformatwn and d~scuss ~deas and findmgs of the combmed study The progress
meeUngs were regularty attended by representa[rves of the sponsonng agenaes Conwrtent with the
progress meetmgs, a senes of public meenngs were conducted ro diswss [he planning effort and sohcrt
public inpu[
The Pro~ect Sponsors w~ll rev~ew the Phase A report and make a dems~on on the altemative that ~s to be
swd~ed m grea[er detail m Phase B of th~s plamm~g effort In Phase B, the consWtant wdl prepare a
prel~mmary des~gn of [he al[ernanve(s) selected by Ihe Pro~ect Sponsors for both sVearns The rype, size,
locat~on of varmus ~mprovemenu w~ll be developed m greacer deta~i In the process, cos[ esnmates wdl
be refined and the relatrve pnonnes and phasmg ot these faahnes w~ll be ~dennfied A final Phase B
report wdl be pubhshed following selecbon of [he preferted altematrve. The Phase B report w~ll serve as
a plannmg tool for [he Pro~ec[ Sponsor5 and prrva[e development wrthm the Fourm~le Canyon Creek and
WondedandCreek tloodplams
Back¢round InPormafion
The smdy area mdudes the Fourm~le Canyon Creek floodplam fmm [he mouth of Ihe canyon to ns
confluence with Boulder Creek and the Wondedand Creek floodplam from dovmstream of Wonderland
Lake to rts coniluence wrth Goose Creek The Fourmde Canyon Creek sp~ll floodpla~q which is loca[ed
between the Fourmde Canyon Creek and Wonderland Creek floodplams trom upstream of Broadway to
appmxunately 191b Street, ~s mcluded in the study area
Ma~or dramageway plamm~g documencs were previousty developed for Fourmde Canyon Creek and
Wondedand Creek by Greenhome & O'Mara, Inc m 1984 and 1987 and for Wondedand Creek by Boyle
Engmeenng m 2002 Due a recent development that haz occurted m ihe iloodplam and macwrac~es m
the ongmal smd~es, the Ciry of Boulder comm~ssmned a rastudy of the Fourmde Canyon Creek
^oodplam m 1997 and the Wonderland Creek tloodplam m 2005 Love & Assoc~ares was re[amed by
the C~ry to prepare a Letter of Map Revismn (LOMR) submittal to FEMA for these nvo s[reams and [he
LOMR was approved by vanous CiTy Boards and the Qty Councd m early 2006 The LOMR was
subm~tted [o FEMA m March, 2006 and approved by FEMA m November, 2006 The new Floodplains
bewme regulatory followmg [he appeal penod m late March, 2007
The LOMR submittal for ihese two creeks mdicated sigmfican[ problems wrth [he onginal FEMA
regulamry s[udies, resul[ing m addmonal propertes being located w~thm the [wo floodplams Of
part~cular importance, the re-s[udy ~dent~fied reaches of Fourmde Canyon Creek west of 19'" SVeet,
where, once the channel capac~ry ~s exceeded, Flood flows overtop the sooth bank of the creek and flow m
a southeasterly direcnon towards Wonderland Creek 'Ihese "spol Flows" resWt in a reduction of flows m
Fourtmle Canyon Creek downsVeam of 19'" Svee[ but also resdt m an mcrease m[he Oows m
W onderland Creek Durmg the 100-year Flood event, approx~mately 3,300 cubm feet per second (cfs) ~s
m Fourtnde Canyon Creek near the mouth of the Canyoq of Uus amount appro~umatety 1,600 cfs wdl
overtop the south bank spol and Flow toward Wondedand Creek The remammg 1,700 cfs wJl remam m
the Fourmde Canyon Creek Channel. L~kewise, Ue 100-year discharge m Wonderland Creek
s~gmficantly mcreases downstream of lhe spJl mflow Some of the spol flows re[um [o Fourmile
Canyon Creek near 19'" SVeet but the ma~onry of the sp~il remams m the Wondedand Creek Floodplam
Dama¢e Analvsis
All proper[y, strucNres and mfrastruc[ure wrthm the 500-yeaz floodplam were mcluded m[he damage
analys~s wh~ch was wdertaken as a part of th~s master planning etTort The damage anatysis was
calculated usmg the UDFCD Methodobev for Evaluatmn of Feu~bd~ri Mule-Junsdict~onal Urban
Dramaee and Flood Control Proiects Flood damages were calculated for the 2-, 5-, 10-, 50-, 100-, and
500.year Flood events For the economm anatys~s, a 50-year pro~ect hfe was chosen, wh~ch corresponds
[o a typ~cal sWC[ure hfe A 6% annual m[erost ra[e was selec[ed, whmh corresponds lo the wst of
6orrowed caprtal for the ennnes mvolveA and a 3% annual rate oC mflat~on wu assumed The net
d~scount rate used m presen[ value calculat~ons was 3%
ES-I
Identifcation of Poten[ial Flood Mitieatian Alternates
Early m the study, a broad range of altemates were idennfied These altemates were screened followmg
an analysis of each sveam and detailed discussions held dunng progress meenngs on a reach by reach
basis for each sVeam A wide array of options were Iooked at as potentials for mmgat~on ofthe Flood~ng
rangmg from a'do-nothmg' staNS quo altema[e [o cons[ruchon of a]00-year Flood channel for each
sveam confimng the spill from Fourtnde m~is ovm channel
Alternates Anelvsis
A number of altema[es were reviewed as a part of this atudy The damage anatys~s and altema[e cosis for
the prev~ous Fourmde Canyon Creek (2000) and Lower Fourtmle Canyon Creek (2002) reports were
updated and benefics and costs for two addmonal altemares were 4eveloped The hvo addmonal
altemates cons~dered Por both sVeams induded a H~gh Hazard Containment and Floodproofing of
Strucmres m the spol area between Fourmde Canyon and Wonderland Creeks altemate Ongmal
al[emates cons~dered m the ~mnal Fowmde Canyan Creek Ma~os Orpmageww Maiter Plan also
mcluded bo[h a 50- year and 100-year channel al[ema[e
The 100-year channel would be designed by an mter-d~sc~phnary team of engmeers, geomorpholog~sts
and b~ologists ro emula[e a naturel channel Tha altemate would ehmmate spols from Fourmde Canyon
Creek to Wondedand Creek dunng the 100-yeaz or smaller Flood event ihe channel would be des~gned
to UDFCD and Ciry cntena wrth FEMA and Ciry reqwred freeboard The 50-year altemate Por Fourmde
Canyon (only) would con~ain the 100.year Flows but woWd have m freeboard built mto the design The
Urban Dramage and Flood ConVOI DaVict, based on legal opm~on from rts concel, has md~cated
reWctance to partic~pace m any Altemate which mciudes con[amment or reduction of the sp~ll unless
downstmam property owners' wncems are property addressed as th~s would negauvely affect
downs[ream propemes on Fourmde Canyon Creek
The High Hazard Zone ~s defined as those areas where the product number of veloc~ry (meazurod m Ceet
per second) nmes flow depth (measured m feeQ equals or exweds Cour, or where flow depths equal or
exceed four feet These portons o! the 100-year Floodplain pose an unacceptably h~gh hazard to human
safery In ihe high hazard wne, the consVUCnoq expansion or enlargement of any sVUCture intended for
human occupancy or estabhshment of a new parkmg lot is prohibrced ihe H~gh Hazard Contamment
alternate would remove strucmres idennfied m erther sVeam from the C~ty's High Hazard Flood Zone
Ihrough direc[ purchase of Ihe property, the enlargement of mad crossmg strucNres, channei excavahoq
and/or floodpmofing or a combmanon thereoE Th~s altemate does not ehmmate the out of channel bank
floodpla~q however, rt reduces Flood levels to those strucmres m the High Hazard Zone for mcreased
safety when evacuatmg occupied bwldmgs and allows for emergency access [o residentlal strucNres
Floodpmofing is a combmanon oC adJustments and/or addrtmns of phys~cal feaWres ms[alled ~q on or
around mdrndual strucmres designed to ehmmate or reduce the potennal for Flood damage ro the
swcmre Floodproofing cons~sts of the techmques and approaches for prevenung or mm~m~zmg tlood
damages to a sWcture and its contents m Flood hazard areas Floodpmofing techmques range from the
constmchon of levees and flood walls around a swcture, [o mstalhng wa[ervnght doors and wmdows,
physicalty ra~smg the swctures elevat~on usmg fill or pilmgs, measures designed to reduce water seepage
anNor resist la[eral pressure from Flood water m the swcture, e[c Floodproofing measures may be
appl~ed to new s[ructures as well as reVOfittmg existmg structures whwh may allow for development
wnhin ihe Floodplam m low hazard areas. The purpose of floodpmofing is to mm~m~ze flood damages by
either keeping floodwaters away Rom damageable property or makmg the pmperty less suscepnble to
damages when floodwa[ers reach [he sWcmre Floodproofing does not el~mmate atl Flood damages but
can, if done correctly, s~gmficantly reduce damages from floodmg 'Che Qty may offer gwdance and
d~sseminate informa[ion regardmg var~ous floodprooEng techmques; however, it would be the
responsibdiry of Ne mdmdual property owner to ~mplement this altemate for iheir own mdmdual
propertes
Altemates proposed are compared to the StaNS Quo or Mamtain Ex~sung Condrtmns al[ema[e Mam[am
exisUng floodplam configuratmn would adopt the new floodplam mappmg wrthout proposing mmganon
improvements at th~s nme Addit~onal non-strucNral methods mduding flash flood forecasting and
warmng systems and evacuanon plans would also be recommended for implementahon Flood msurance
and tloodproofing of swctwes would also be recommended (at che mdrv~dual properry owner's
ezpense) Floodplam regulatwns would be str~cHy enforced. Post flood relwf would be provided Tha
altemate reqmres na new fundmg, but may sacrifice opportumnes to greatty ~mprove Fourtmle Canyon
Creek and mingate floodmg m the fuwre A"Do Nothmg" solunon would offer no opportumry to
mmgate sp~lls and floodmg ro the south of FourmJe Canyon Croek and would oller no opportuniry ro
ehmmate Floodmg m the Waldorfor Cresrnew Elementary Schools
Reach by Reach cost eshmates were prepared for the each of the tltemates analyud (five m[he Fourm~le
Canyon Creek floodplam and four m the Wonduland Creek Ooodplaui)
Each of the altemates analyzed for both sVeams w~ll st~ll mcur an expecred damage durmg flood evenu
Examples of these damages would mclude ~solaced bank ems~on locatwns m Ihe consiructed °namraf'
channel altemate or wide spread damage m lhe mamtammg of [he ez~stmg iloodplam configuranon
altemate
One method commonly used [o compare altemauves ~s the benefiVCOSt (B/C) rnbo In general, the h~gher
the B/C rat~o the more cost ellechve ~s an altema[e In th~s study, the benefiVcost raho compares the total
cos[ m ~mplement a Flood convol altemanve with Ne benefits that would be real~zed ~f that Flood wnVOl
altemanve were ~mplemented The total cost [o ~mplement a Flood conVOl altematrve was calcWated as
the sum of the conswctwn costs, properry acqmsrtion wsts (land and strucmre), nght-of-way reqmred to
~mplemen[ [he altemate and O&M cosu The benefit that would be reahzed ~f the flood conVOl
altematrve ~s implemented was calwlated as the d~fferonce between flood darnages under exisnng
condrtions mmus tlood damages that would be mcurred after implementaGon of the altemanve
BenefiUCost Ratw = fEz~snng Flood Damaeesl - fFuture Flood Damaees wrth Altematrve m Placel
Cos[ ro Implement Altematrve
A B/C rauo grea[er then one (1) md~cates the becefit recerved ~s greater ihen the wst to ~mplement the
altemai~ve A B/C rauo equal to one (1) md~cates the benefit recerved ~s the same as [he cost m
~mplemen[ [he al[emanve A B/C rano lus Uien one (I) mdmates the benefit cecerved is less Ihen the
cos[ to ~mplemen[ [he al[ernanve
ES-2
Companson of benefits and costs must be made for the same t~me frame Benefiu stemmmg from
reduced Flood damages occurtmg annually over the hfe of the pro~ect cannot be compared direc[ly wrth
consWCtmn wsts, which generalty occur over a short penod of nme neaz the begmmng ot [he pro~ect
All benefits and wsts must be converted [o erther present value or annual amounts before compar~soq
usmg an appropnate d~scount ra[e, whsh accounts for the time value of money For ih~s study aIl cosu
were converted to presen[ value Present value calculatmns assumed a 50-year pro~ect hfe, which
cortesponds to the rypical swctural hfe, and a d~scount rare of 3% (6% ennual mterest rate mmus 3%
annual rate of mFlatlon)_
The benefiVcost rano for each altemate for [he ent~re study reach ot each creek ~s as follows
Fourmde Camon Creek
Altemate I 50•Year Channel H/C = 1 43
Altema[e 2 100-Year Channel B/C = I 34
Altema[e 3 Status Quo B/C = 0 00
Altemece 4 Floodproofing B/C= l 96
Altemate 5 H~gh Ha~ard Contamment B/C = 0 08
Wondedand Creek
Aitema[e I 100-Year Channel B/C = 1 92
Altemafe2 SfaNSQuoB/C= 000
AI[emate 3 H~gh Hazard Comamment B/C = 0 44
Altemate 4 Floodproofing B/C = 3 64
There are numerous intang~ble benefits that would az~se fmm the implementadon of flood mmgatwn
~mprovements By definitioq mtang~ble benefits are d~ffiwlt to measure and are not d~rectly quanufiable
m temis of dollar value or dollars spent for the~r usage The mtang~ble benefits that may be reahzed
through tlood mmgat~on mclude the followmg
• Improved tra~c movement dunng tloods
• Improved emergency response
• Improved publ~c healih and safery •
• Improved env~ronmen4 water quahry and ripar~an habitat
• Lower flood msurance
• Potennal for scienhfic, educanonal, hisroncal amemues
• Increased property values
• Creahon oCcW[ural, educahonal, and sc~ent~Ec resourees
Because mtangible benefits are mt d~rectly quannfiable m terms of a dollar value they are not mcluded m
[he benefidcost analys~s As a result, Ihe benefiUcost ratms are lower Ihan what would be reahzed ~f
dollar values were placed upon the m[ang~ble benefits
ln addmon to the benefiUcost rat~os presented above, a number of addmonal evaluatron factors should be
considered when choosmg a course of acnon to m~ngate flood damages withm the FourtnJe Canyon
Creek and Wondedand Creek floodplams Helow is a hst of some ofthe potennal evaluahon factors
Evaluatmn Factors
• Flood M~l~ga[ion
Life Safely
Pmperty damage
• Env~ronment
Temporary D~scurbance
Long-term beuefit
Groundwaler
• Transportat~on
Automonve
Bwycle/PeAesVian
• DevelopmenURe-Development
Growth Management
ARordable Housmg
• Aesthe4cs
• Benefit/Cost Rano
• Construc[ion Cos[
• Recreanon
• Perm~ttmg Reqwrements
• Impacts to Fourtmle Canyon Creek
• Impacts [o Wondedand Creek
• Conformance wrth o[her Plannmg Documents
• Competing Prwnnes
• Pubhc Acceptance
• Operztmn and Mamtenance
B~gger floods can and w~ll occur Th~s sta[ement holds true whether you are talkmg about a 10-year,
100-year or 500.year flood event The Fourmde Canyon Caek and Wondedand Creek Floodplains have
not had a sigmficant flood m the recent documenced past The pubhc awareness of the s~gmficance of the
flood srtuanon ~s low smce many of the res~dents m the Floodplain have mt seen the resWts of a d~saster,
or had [o clean up afler a Flood m[heir neighborhood or expenenced the m~ury ro or loss of a family
member or fnend m a Flood even[
Recommended AI[erna[e
The contract Love & Assoc~ates, Inc has wrth the Urban Dramage and Flood Contml District reqwres
that the consultant make a recommenda4on as m the best ovelall aitemate solut~oq takmg mro account a
variety of mfortnat~on developed throughout the master plamm~g process for both Fourmde Canyon and
Wonduland Creeks
ES3
The f~rtn of Love & Assoc~ates, lnc is recommendmg a combinatmn al[emate f'or both Fourtnile Canyon
Creek and Wonderland Creek [n developmg the Recommended Altemate we evalua[ed m combmabon
the altemates ut~l~zmg a reach-by reach approach
For each creek [he recommended altemate cons~sts of a combmanon of the 100-Year Channel, H~gh
Hazard Contamment, Floodproofing and Mamtam Stams Quo
In Reaches 5 and 6 of Fourmde Canyon Creek, the 100.Year Channel and 50-Year Channel altemates
resWt m a change m the spahalty vaned Flow d~str~bunon m the Floodptam which would reqwre
channeh~auon m the confluence with Boulder Creek Love & Assoaates, Inc beheves that complete
cliannehzanon o! Fourm~le Canyon Creek fmm Reach 5 or 6 to rts contluence witli Boulder Creek ~s not
a v~able optwn The Urban Oramage and Flood Con[rol D~stnc[ has mdicaced they are not wilhng [o
part~cipate m a soWnon wh~ch mcorporates contammenUchannehzanon of all Flows from upsVeam ro the
conFluence wrth Boulder Creek Smce these altemates change the flow d~stnbuuon that currently ex~sts
m the Floodplams of bo[h sveams, channehvat~on creates both habdiry and hfe safery nsks ~f b~gger
floods were [o ocwr Lands could be mundated by the inVOductwn of Flood waters where they would mt
have ex~sted prmr to the re-d~str~buhon of flood waters by erther ot these altemates Love & Assoc~ates,
Inc ~s not recommendmg either a 50 or 100-year channel alterna[e upsVeam oC the spill zone for these
reasons In some downatream reaches where the 100-year altemate resW[ed m a B/C raao greater than 1,
the 100-year altemate ~s mcommended wnh a reduced comeyanre reqwred In Reaches 26 and 4 on
Fourmile Canyon Creek the 100-year channel alHemate is recommended The 100-year channel
downsVeam of the spol zone contams the reduced Flow that remams after the spol from Fourmile Canyon
Creek to Wonderland Creek Likewise, m Reaches 4 and 5 on Wonderland Creek where the 100-year
altemate resul[ed m a B/C rat~o greater than 1, Love & Associates ~s recommendmg th~s altemate For
both creeks the 100-year channel is des~gned to contam [he 100-year d~scharge and pmvide a mm~mum
of I' of freeboard Th~s freeboard contams the 500-year Flow, makmg Floodproo(mg unnecessary m
these reaches Addmonally, m reaches where 100.year ~mprovements are implemenced, flood msurance
would also no longer be requved I[ should be noted that unless 100.year impmvements are ~mplemented
thus ehmmatmg propertes fmm the floodplam, Flood msurance is reqmred wrth all other soluhons
including a 50.year channel altemate and floodpmofing which provides a degree oC Flood pmtecnon but
does no[ remove the property from the floodplam
The H~gh Hazard Contamment AI[emate for both creeks has a benefit/cost rano of less than one p),
however, no credrt is grven m the anatys~s for hfe safety. Smce hfe safery is of pnmary concem [o th~s
consultant, [hu altema[e a the bas~s of our recommendanon The High Hazard Contamment Altemate
removes all residences from the h~gh haTard Ilood wne allowmg safe evacuaLOn and emergency access
dunng a 100-year flood event The tloodproofing alremate has a high benefiVcost rat~o and [he dollars
spent by mdmdual property owners consVUCnng ~mprovements to pmtect the~r mdrndual propertes
offer s~gmfican[ protecnon m structures and con[ents dunng flood events A combmahon of the High
Hazard Contamment and Floodproofing Altemate is recommended Cor Reaches ta, 3, 5, and 66 on
Foumi~le Canyon Geek and for Reaches 3, and 6 on Wondedand Creek Add~tmnally, the
Floodpmofing Altemate is recommended for Reach 6a on Fourmde Canyon Creek and for Reach 2 on
Wondedand Creek For mdmdual reaches on both creeks these altemates are recommended m[andem
The benefiVcost raho of [h~s combmed allemate ranges fmm 0-2 65 on Fourmde Canyon Creek, and 0-
5 34 on Wondedand Creek Wrth ~mplemen[ahon of [h~s combmed altema[e, flood msurance would shll
be requved by mosl lenders and mdrndual property owners would be sVOngly encouraged to purchase
flood msurance whether or not a mortgage on Ne~r pmperty ~s in effect
In Reaches Ib, 2a, and 6c on FourmJe Canyon Creek and for Reaches 1, 7, and 8 on Wondedand Creek,
m structures are bemg impacted For each altemate anatyzed, these reaches reqwred no work
Therefore, the Mamtam Ex~snng Altemate ~s recommended for these reaches
Tables ES 1 and ES 2 summanze the recommended altemate for each reach as well as the B/C rano and a
breakdown of pubhc and pnvate wsts for ~mplemenung ihe altemace In the tables below, it should be
noted that the dollar wsts hsted under the 'pnvate' category aze for those cos[s [ha[ would be mcurted by
mdmdual property owners ro floodprooCiheir own properties
Table ES.1
Recommeuded AI[eroate
Fourmile Canyon Crcek
B~C Cas[
Reach Altemale Raho Total Pubhc Pnvate
Reach la HHZ ContammenVFlood mofin 0 O&/0 95 S] 583,800 $I 025 000 $558 S00
Reachlb MamtamEzisnn 0 $1188000 $I I88000
Reach 2a Mamtam Ez~shn 0 $442 000 $442 000
Reach 2b 100-Year Channel 2 65 $I 283 660 $1 283 660
Reach 3 HHZ ContammenVFlood mofin 0 35/I 18 $900 200 $741 000 $159 200
Reach4 ]00-YearChannel I88 $6730,860 $6730860
Reach 5 HHZ Con~smment/Flood roofin 0 12/4 42 $798 400 $394 000 $404,400
Reach 6a Flood roofin I 68 E3 I30 600 $290 000 $2 840 600
Reach 66 HHZ ContammenUFlood roofin 0 03/4 44 $762 700 $595 000 $167 700
Reach 6c Mamtam Ez~stin 0 $ I73 000 $173 000
Total $16,993,220 $12,862,520 $4,130,700
ES-4
Table ES1
Recommended Alternate
Wonderland Creek
g~C Cost
Reach AI[ernate Ratio Total Public Pnvate
Reach l Mamtam Ex~stin 0 $61 S 000 $61 S 000
Reach 2 Flood roofm 0 6I 5539 400 $332 000 $207 400
Reach 3 HHZ Containment/FIooC roofin 0 39/l 37 $10 236 600 $7 307 000 $2 929 600
Reach 4 100-Year Channel 5 34 $7 1 LO 300 $7 110 300
Reach 5 100.Year Channel 4 75 $4,057,800 $4 057 800
Reach 6 HHZ ContammenUFlood roofin 0 51/0 52 $5,024,300 $3,168 000 $1 856,300
Reach 7 Mamtam Exislm 0 $807,000 E807,000
Reach 8 Mamtam Ex~snn 0 $289,000 $289,000
Total $28,682,400 $23,689,100 $4,993,300
Figures ES-la-e and ES-2a-c depst the specific altemate being proposed by this consW[an[ for rcs
Recommended Plan Cor each reach oFeach strearn
It ~s ~mportant m reahze the Fourtnde Canyon Creek and Wonderland Creek floodplams are hydrauhcally
connecced Due m topography and Ne hmrted channel capaciry of Foulmde Canyon Creek, spills from
Fourmde Canyon Creek Flow mro [he Wondedand Creek floodplam Dec~smns made on Floodplam
management and mmganon wrthm Ihe Fourmde Canyon Creek Floodplam have a d~rect ~mpact on [he
Wonderland Creek floodpla~rt All development withm the ex~snng floodplam should be m acwrdance
wrth the C~ty, Counry and Federal perm~ttmg reqmremen[s
ES-5
REACH 6C
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ALTERNATE FIGURE
ES-1a
PAGE
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URBAN DRAINAGE AND FLOOD CONTROL DISTRICT
FOURMILE CANYON CREEK
AND WONDERLAND CREEK RECOMMENDED
LTERNATE Fi~uRE',
ES-1c
DAIE ROMN: 2003 ••••~~~• ~•
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COLORADO
CITY OF BOULDER PAGE
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AERIAL PNOTOGRAPHY BY: NERPopC Q COMPANY ~ FOURMILE CANYON CREEK RECOMMENDED FIGURE
TOPOpiAPHIC MMPINC BY: NERPop( d COMPANY X~+~- ~~b~~~^~~ •,• URBAN DRAINAGE AND FLOOD CONTROL DISTRICT
CONTWR W1ptVAL ONE FEET ,,,,,,..,, ~~ AND WONDERLAND CREEK ALTERNATE ES-1d
o"h ~o"'": 200~ ""' """" ' °`°~ a.i CITY OF BOULDER, COLORADO PAGE
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DAIE RONN: 2003
w'.;.~:';:, """""' °`°°' w~ CITY OF BOULDER, COLORADO PAGE
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DAIE FLONN: 2003 „~,,,~°,;;, °°•"•~" ~ o,~ CITY OF BOULDER, COLORADO PAGE
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AERIAL PHOTOf~tAPHY BY: MERRIp( ~ COMPANY ~ FOURMILE CANYON CREEK
TOPOGRAPHIC MAPPING BY: MERRIpf 3 CqAPM1Y ~++~- ~ A~~«~~~ ~ URBAN DRAINAGE AND FLOOD CONTROL DISTRICT ES-2b
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DAIE FLOWN: 2003 ~~~~~ ~~~~~ ~~ """""' °~ CITY OF BOULDER, COLORADO
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TOPOCRMHIC MAPPING BY: MERRIp( h COIAPANY ~~~ ~ Apodatea,lnc. ~,., ~M URBAN DRAINAGE AND FLOOD CONTROL bISTRICT FOURMILE CANYON CREEK RECOMMENDED ES-2c
CONTWR IN7ERYAL• ONE FEET AND WONDERLAND CREEK
••~•- ~•~ •~•~ ••~••~~• ~• ALTERNATE
DAIE RONN: 2003 • ' °~ ~ CITY OF BOULDER, COLORADO PAGE
DA7lNA: HORIZONTAL - NAD83, COLORApO STAIE :.-d..~.:.;a MASTER PLAN WONDERLAND CREEK ES-13
PLANE COORD. - NOR1H, 4ERTICQ - NAVDBB ti~F~ ~~ 11/OB
H7rA~Nr~tE-NT L
URBAN DRAINAGE AND FLOOD CONTROL DISTRICT
June 26, 2007
David W. Lloyd, 6ceculive Dfrector
248~ W. 261h Avenue, Suite 1566
Denver, CO 80217-5304
Bob Harberg
City of Boulder Uriliries
Post Office Box 791
Boulder, CO 80306
Telephone 303-455-8277
Fax 303-455-7880
www.udfc:d.org
Subject: Fourmile Canyon Creek and Wonderland Creek Conceptual Prelinwiary Design Report
Selected Plan (Draft)
Deaz Bob:
Enclosed is a copy of the June 25, 2007 draft of the selected plan for the above-referenced study.
We hope this draft incorporates flie comments received from you following our discussions
tl~roughout the past yeaz. As it provides direction to the consultairt for preparing the fiual report
on r]~is study, it is very important that you review it and provide us with your comments.
Tt is my understanding from our telephone conversa6on yesterday moming that a significant
public iuvolvement process must occur before you will be able to provide me wifll the conunents
necessary to finalize this draft, aud that process will not be complete unril November of this year.
Any effort on your part to expedite this process will be greatly appreciated.
KAM/mc
Enclosure
disddfi-plan
Sincerel ,
~
/ MacKenzie, P.E.
Seiuor Project Engineer
Master Planuing Pro,g~am
Worku[9 witfvyowsi~cce 1969
DRAFT 5elected Plan for the
Major Drainageway Planning for Fourmile Canyon Creek and
Wonderland Creek Conceptual Preliminary Design Report
June 25, 2007
The Selected Plan for the Foumvle Canyon Creek and Wonderland Creek watersheds agreed upon
by City of Boulder (Boulder) and the Urban Drainage and Flood Control District (Disirict)
(hereinafter Boulder and Disfrict joinfly may be referred hereinafter as "Sponsors'~ to be shown by
Love & Associates Bngineering, Inc. (Love) in the final Fourmile Canyon Creek and Wonderland
Creek Major Drainageway Planning Concepheal Preliminmy Design Report (hereinafter called
"Final Plan") is described in general and specific terms below.
SELECTED PLAN AND DIRECTLY RELATED ISSUES
Unless specifically directed otherwise below, ttus Selected Plan to be shown in the Final Plan
essentially follows the recommendations made by Love in the Fourmile Cmryon Creek and
Wonderland Creek Major Drainageway Planning Phase A Report: Aliernatives Analysis, dated
May 2007 (hereinafter called "Alternatives ReporP~ based on the following principal elements,
goals and objectives;
• 'nimi~.r. stormwater and flood-related damages to draina~eways, public infrastiucture and
private properiy. Do this with vatue engineering and practicalities of implementation in mind.
• Balance tbe development in the watershed with stormwater management implementalion that
complements drainageway and stream stability solutions, that as a system, provide multiple
benefits that include:
o Water quality protection and enhancement;
o Water quantity resourees protection;
o Pteservation of naiural character of the waterways and their terrestrial and aquatic habitat
resource;
o Wherever possible, provide public use and access and/or trails within the corridors of identified
waterways in order to provide maintenance access that wilI also provide for active and passive
recreation ofthe public.
• Consider the needs for new and upgraded roadway crossings when such improvements aze
practicable, affordable and add significant value in relation to the cost
Love is directed to address, develop, describe and show a conceptual preliminary design based on
this Selected Plan, as well as all other items that are to be addressed in the Final Plan report as
described in the agreement beriveen District and Love for this project. Love is also directed to show
and describe all recommended facilities, costs and actions on a reach-by-reach of each tributary and
major drainageway. In general, the Final Plan shall pro'vide, show, and recommend the following:
srm.anm: ro~~4 cmy~o~vm w~.wwawrx~+aoai
1) Along all reaches that currenfly have clear presence of riparian vegetation and/or wetlands,
make it clear in the Final Plan that these reaches are not to be channelized, but pmtected &om
further vertical and lateral migration .to the maximum extent practicable unless such work in
needed for the protection of existing human occupied structures.
2) Under a section in the Finat P.lan titled "General Recommendations", recommend:
a) That the conh~Olling jurisdictiotts take steps to stabilize all major waterways when theu
watershed urbanizes, rehabilitate existing degraded reached of the waterways and their
tributaries, and to aggressively control etosion and sediment transport during conshuction
activities.
b) That Sponsors and any other jurisdiction having land use control powers in these watersheds
require new land development and significant redevelopment and publicly funded projects to
provide to the meacimum extent prectiaable runoff volume control practices (i.e., m;,,imi~e
dixecdy connected'unpervious areas aad employ infittrating BMPs) whenever site conditions
permit.
c) That the controlling jurisdictions take steps to require that all BMPs for all new
development, redevelopment, and publicly funded projects provide a Water QualiYy Captute
Volume (WQCT~ as recommended in the Urban Storm Drainage Criteria Manual - Volume
3, after accounting for volame reductions achieved using volume ~control pracrices as
recommended under Item l.b above.
d) That all jurisdictions having land use control powers in this watershed continue to
implement theu floodplain management regulations, including regulation of the 100-yeaz
floodway and floodplain.
That these jurisdictions adopt a policy, if not already done so, of preserving ihe defined
floodplains as open spaces to the maximum extent possible and that at least 1-foot freeboazd
be provided for the lbwest #loor above the 100-yeaz flood elevation shown on the latest flood
hazard area delineation or FIRM maps for all human occupied structures built adjacent to, or
within, the defined 100-year floodplains.
e) That all jurisdictions having land use confrol powers in flus watershed continue to
participate in FEMA's flood insiuance Community Rating System and public education
programs.
3) List on each plan view and profile sheet of the preliminary design, wheze appropriate, the
recommended wetlaud mitigations that will be needed to implement recommended improvements,
if any.
4) Include on each plan sheet of the preliminary desigu, the following statement: "Many activities
that occur or affect in ditches, drainages, creeks, ponds or wetlands require a Section 404 Permit
Authorization from the US Army Corps of Engineers. During preliminary design, and prior to
final design or starting work, contact the Coips' Denver Regulatory Of~ce at 303-979~120 for
appropriate pemut authority to avoid compromising and delaying the completion of the project"
5} Show on appropriate plan and pmfile sheets (and as deemed necessary) facilities to azrest the
vertical degradation of the low flow channel of natural and man-made waterways and to help
rehabilitate, as much as possible their stable function and habitat.
&lechdP/m: FwvmlkCm9onGeekmdNadv/mdGYalAmP ]001
~ Recommend rehabilitating eroded and degraded banks where needed and desired to arrest the
horizontal erosion along natural waterways using bio-engineered methods that combine buried
soil riprap and revegetation with native species of riparian and dryland vegetation.
7) Show on plan view and profile sheets the needed buttressing of critical utilities and other
structures that may be endangered by stream erosion.
8) Using the input from stakeholders and the public, work with Sponsors and affected other local
jurisdictions to prioritize the recommended facilities and actions that aze list in the Final Plan
and clearly articulate them in that document.
9) Describe the recommended type and schedule o£ maintenance activities for all unproved
facilities recommended in the Final Plan.
10) Consider the various functions of all natural waterways in the study watersheds and their
floodplains, including flood conveyance, riparian hebitat, open space, aesthetics, recreation,
urban development, water qnality, utility crossings, transportation and other features.
11) Aclmowledge in the Final Plan, that land-use changes to the contributing watersheds affect the
flood hazazd nature (i.e., runoff rates, volwnes and depths), the transport of sediment, and the
water quality of the receiving natural waterways. The Final Plan, under "General
Recommendadons" shall suggest that Sponsors and any other jurisdiction having land use
control powers in these watersheds monitor land-use changes and whenever the land-use
changes result in unperviousness ratios that exceed the projections identified in ihe Final Plan,
these jurisdiction take steps fiuther limit increases in stormwater ruuoff through the use of
additional on-site detenrion, infiltr~ating BMPs and WQCV BMPs, thereby reducing the runoff
rates, volumes and future damage potentials to the Final Plan levels.
EXECUTIVE SUMMARY
Include an Executive Summary in the Final Plan written in plain, non-technical language, which is
directed primarily at the genetal public and elected officials. This summary should, at the
m;n;mum, contain the following as well as other items listed in District's checklist for preparation
of the final outfall systems planning conceptual preliminary design report:
1. A brief summazy of the planning process including numbers of progress and public meetings.
2. A brief description of the decisions made by Sponsors during this project.
3. A brief summary of all design criteria specifically developed for this plan.
4. A brief summary of the following sections of the Final Plan: Purpose, Study Area, Altematives
Analysis, Recommendations, and Prelixninary Design.
5. A map showing the area and all recommended improvements.
6. Tabulaz and narrafive ~~mmarigS of cosfs showing costs for capital innprovements,
engineering/administrative/contingencies, and ]and values, all sorted by drainageway reach,
tributary, and outfall system, and by jurisdiction. The reach length (miles), tributary catchment
azea (square miles), and their totals should also be included in the table.
SeYctWPlm: FewmikCm~mGaekmdWoMerImWCYeekA4JP10W
Incorporate the £ollowipg notes on each drawing:
"This drawing is for mastef planning purposes'and ~epresents preliminmy and conceptual
engineering. Alternatives to this outfall system will be considered by local agencies and the
Ilrban Drainage and Flood Coritrol District provided the alternative ofjers ari equivalent
intent of the plan, including hydraulic capacity, water qudlity, stremn stability and natural
waterway features. The alternative must comply with all requirements of the [ocal
jurisdiction and the Urban Drainage and FTood Conirol District. Zn addition, there may be
State and Federal requirements that will need to be cortsidered and met. This drawing does
not provide a finad design and shall not be used for construction purposes. "
"Local CiKes, Towns, and Counties manage and regulate all lancl use change, development
and redevelopment activities within and adjacent to the 100 year floodplains in order to
prevent, to a maximum extent possible, future flood damages to buildings and s4ruatures
from the 1003~eco~ flood and to minimize damages from larger floods. The
recommendations of this plan provide a set of opHons subscribed to by Cities, Towrzs and
Counties in carrying out their flood plain management and regulatary respon.s3bilities and
ob(igations. "
ADDITIONAL DIRECTION
Unit costs should be updated to reflect the most ciurent costs available.
2. Include an Acknowledgements section listing all participants and stakeholders in this study.
Include in the list their name, organization and function in the planning process (e.g, City of
Boulder staff: provided review and input. Or, John Doe: attended two progress meetings and
provided the following input: ~.
3. Show all maintenance access routes along all reaches. To the e~ctent feasible, the alignment of
these routes shall be coordinated with existing and planned recreational trails identified using
input provided by Sponsors, special distdcts and other local stakeholders.
4. Summarize cost estimates of improvements by jurisdiction where those improvements are
located, by the reach in which the improvements aze located and overall project totals.
5. Report estimated costs for maintenance of all facilities, including detention ponds, storm sewer
outfall points, grade control structures, etc. reported in the Final Plan.
SekeudPlmr FavmiL Carym OrrF mdWwdnbd 6eeAAff1P 1001
June 26, 2007
URBAN DRAINAGE AND FLOOD CONTROL DISTRICT
G
David W. Lloyd, 6cecutive Director
2480 W. 26th Avenue, Suite 15fiB
Denver, CO 80211-5304
Bob Harberg
City of Boulder Utilities
Post Office Box 791
Boulder, CO 80306
f17TN c.N M E ti T
Telephone 303-455-6277
Fax 303-455-7880
www.udfcd.org
SuUject: Fourmile Canyon Creek and Wonderland Creek Conceptual Prelnnuiary Design Report
Selected Plan (Diaft)
Deaz~ Bob:
Enclosed is a copy of the 7une 25, 2007 draft of the selected plan for the above-referenced siudy.
We hope flus draft incorporates flie conunents received from you following oiu discussions
throughout the past yeaz. As ii provides direction to fhe consultatrt for prepazalg the final report
on tbis study, it is very important that you review it and provide us with your conunents.
It is my understanding from our telephone conversation yesterday morning that a s ~onificant
public involvemeut process must occur before you will be able to provide me with the comments
necessary to finalize this draft, aud that process will not be complete until November of this yeaz.
Airy effort on your paxt to expedite flus process will be greatly appreciated.
I{AM/mc
~nclosure
dist\dti-plan
Sincerel ,
~
I~ MacKenzie, P.E.
Senior Project L~ngineer
Master Plazming Prograni
Wnrlcu29 witlt.you~suue 1969
DRAFT Selected Plan for the
Major Drainageway Planning for Fourmile Canyon Creek and
R'onderland Creek Conceptual Preliminary Design Report
June 25, 2007
The Selected Plan for the Fourmile Canyon Creek and Wonderland Creek watersheds agreed upon
by City of Boulder (Boulder) and the Urban Drain~e and Flood Control District (District)
(hereinafter Boulder and District jointly may be refezred hereinafter as "Sponsors") to be shown by
Love & Associates Engineering, Inc. (Love) in the final Fourmile Canyon Creek and Wonderland
Creek Major Drainageway Planning Conceptual Preliminary Design Report (hereinafter called
"Final Plan'~ is described in general and specific terms below.
SELECTED PLAN AND DIRECTLY RELATED ISSUES
Unless specifically directed otherwise below, this Selected Plan to be shown in the Final PZan
essentiatly follows the recommendations made by Love in the Fourmile Cmryon Creek and
Wonderland Creek Major Drainageway Planning Phase A Report: Alternatives AnaZysis, dated
May 2007 (hereinafter called "Alternatives Report") based on the following principal elements,
goals and objectives:
. Minimize stormwater and flood-related damages to drainaoeways, public infrasmactLUe and
private property. Do tYus with value engineering and practicalities of implementation in mind.
• Balance the development in the watershed with stormwater management nnplementation that
complements drainageway and stream stability solufions, that as a system, provide mulhple
benefits that include:
o VJater quality protection and enhancement;
o Water quantity resources protecdon;
o Preservation of nahual character of the waterways and their terrestrial and aquatic habitat
resoutce;
o Wherever possible, provide public use and access and/or trails within the corridors of identified
watervvays in order to provide maintenance access tbat wilI also provide for active and passive
recreafion of the public.
• Consider the needs for new and upgraded roadway crossings when such improvements aze
practicable, affordable and add significant value in relation to the cost.
Love is directed to address, develog, describe and show a conceptual preliminary design based on
tlus Selected Plan, as well as all other items that aze to be addressed in the Final Plan report as
described in the agreement between District and Love for this project. Love is also directed to show
and describe all recommended facilities, costs and actions on a reach-by-reach of each tributary and
major drainageway. In general, the Final Plan shal] provide, show, and recomxnend the following:
Seleesd Plw.~ Fourmik Cmryorr 6eet mid Fcv~rlmd 6eek hIDP 300J
1) Along all reaches that currenfly have clear presence of riparian vegetation and/or weflands,
make it cleaz in the ~inal Plan that these reaches are not to be channelized, but protected from
furthex vertical and lateral migration.to the maximum extent practicable unless such work in
needed for ttie protection of e~sting human occupied structures.
2) Under a section in the Finat P.lan tifled "General Recommendations", recommend:
a) That the controlling jurisdictions ffike steps to stabilize all major waterways when their
watershed urbanizes, rehabilitate existing degraded reeched of the waterways and their
tributaries, and to aggressively coxYh'o1 erosion and sediment hansport during construction
activities.
b) That Sponsors and any other jurisdiction having land use control powers in these watersheds
require new land development and significant redevelopment and publicly funded projects to
pzovide to the maximum exte,nt practicable runoff volume control practices (i.e.r minimi~e
direcfly connected impervious areas and employ infiltrating BMPs) whenev,er site conditions
permit. , ,
c) That the controlling jurisdictions take steps to require that all BMPs for all new
development, redevelopment, and 'publicly funded projects pzovide a Vdater QuatiYy Capture
Volume (WQCT~ as recommended in the Urban Stoan Drainage Criteria Manual - Volume
3, after accoimting for valnme reductions achieved using volume ~control practices as
recommended under Item 1:M above.
d) That all jurisdictions having land use control powers in this watershed continue to
implement their floodplain management regulations, ~including regulation of the 100-yeaz
floodway and floodplain.
T7~at these jurisdictions adopt a policy, if not already done so, of preserving the defined
floodplains as open spaces to the maximum extent possible and that at least 1-foot freeboard
be provided for the lOwest #loor above the 100-year flood elevation shown on the latsst flood
hazazd area delineation or FII2M maps for all human occupied structures built adjacent to, or
within, the defined 100-yeaz floodplsins.
e) That all jurisdictions having land use control powers in this watershed continue to
participate in F'EMA's flood insurance Community Rating System and public education
Programs•
3) List on each plan view and profile sheet of the prelimin~y design, wheze appropriate, the
recommended wefland mitigations that will be needed to implement recommended improvements,
if any.
4) Include on each plan sheet of the preliminary design, the following statement: "Many activities
that occ~a or affect in ditches, drainages, creeks, ponds ar wetlands require a Section 404 Perttut
Authorization from the US Azmy Corps of Engineers. During preliminary design, and prior to
final design or starting work, contact the Corp's' Denver Regulatory Office at 303-97913120 for
appropriate permit authority to avoid cpmpromising and delaying the completion of the project"
5) Show on appmpriate plan and profile sheets (and as deemed nacessary) facilities to azrest the
vertical degradation of the low-flow channel of natural and man-made waternays and to help
rehabilitate, as much as possible their stable function and habitat.
y(rchdPlmr.FmvmPeC ~mCrtekmd{YwMo/mdC}akAmP]00]
6) Recommend rehabilitating eroded and degraded banks where needed and desired to arrest the
horizontal erosion along natural waterways using bio-engineered methods that combine buried
soil riprap and revegetation with native species of riparian and dryland vegetafion.
7) Show on plan view and profile sheets the needed buttressing of critical utilities and other
structures that may be endangered by stream erosion.
8) Using the input from stakeholders and the public, work with Sponsors and affected other local
jurisdictions to prioritize the recommended facilities and actions that aze list in the Final Plan
and clearly articulate them in that document.
9) Describe the recommended type and schedule of maintenance acfivities for all unproved
facilities recommended in the Final Plan.
10) Consider the various functions of all natural waterways sn the study watersheds and their
floodplains, including flood conveyance, riparian babitat, open space, aesthefics, recreation,
urban development, water quality, utility crossings, transportation and other feaiures.
11) Acknowledge in the Final Plan, that land-use changes to the conhibuting watersheds affect the
flood hazazd nature (i.e., ninoff rates, volumes and depths), the transport of sediment, and the
water quality of the receiving natural waterways. The Final Plan, under "General
Recommendations" shall suggest that Sponsors and any other jurisdiction having land use
control powers in these watersheds monitor land-use changes and whenever the land-use
changes result in imperviousness ratios that exceed the projections idenfified in the Final Plan,
these jurisdiction take steps fiuther limit increases in stotmwater runoff through the use of
additional on-site detention, infiltrating BMPs and WQCV BMPs, thereby reducing the runoff
rates, volumes and future damage potenfials to the Final Plan levels.
EXECUTIVE SUMMARY
Include an Executive Summary in the Final Plan written in plain, non-technical language, which is
directed primarily at the general public and elected ofFicials. This summary should, at the
minimum, contain the following as well as other items listed in Disirict's checklist for preparation
of the final outFall systems planning concepiual preliminary desi~ report:
1. A brief summary of the planning process including numbers of progress and public meetings.
2. A brief descriptian of the decisions made by Sponsors during ttus project.
3. A brief sununary of all design criteria specifically developed for this plan.
4. A brief summary of the following sections of the Final Plan: Purpose, Study Area, Altematives
tlnalysis, Recommendations, and Pteliminary Design.
5. A map showing the area and all recommended unprovements.
6. Tabulax and narrative swnmaries of costs showing costs for capital improvements,
engineeringJadministrative/contingencies, and land values, all sorted by drainageway ieach,
tributary, and outfali system, and by jurisdiction. The reach length (miles), tributary catchtnent
azea (square miles), and their totals should also be included in the table.
SdenedPlm. Fovrmlle Con~an G~ctm~dWarderland6eek.tmP ZOW
Incorporate the ~ollowipg notes on each drawing:
"This drawing is for .m~rster~ plcmning pzrrpases and represents preliminmy and conceptual
engineering. Alternatives to this outfall system will be coruidered by local agencies med the
Urban Drainage and Flood Coritral bistrict provided the alternative a,ff'ers ati equivadent
intent of the plan, including hydraulic capacity, water quality, stremn stability and natural
waterway features. 2'he alternative must comply with all requirements af the local
jurisdiction and the Urban Drairrage and Flood Control District. In additian, there may be
5`tate and Federal requirements that will need to be considered and met. This drawing does
not provide a final design and shall not be used for construction purposes. "
"Local Cities, Towns, and Counties mancrge and regulate all lanil use change, development
and redevelopment activities within ancl adjacent to the 100 yeat floodplains in order to
prevent, to a maximum extent possible, future flood damages to buildings and stru~tures
from the 100 year flood and to minimize damages from larger floods. The
recommendations of this plan provide a set of option.s subscribed to by Cities, Towns cmed
Counties in carrying out their,~lood plain management and regulatary responsibilities and
obligations. " ~
ADDITIONAL DItiECTION
1. Unit costs should be updated to reflect the most current costs available.
2. Include an Aclaiowledgements section fisting all participants and stakeholders in this study.
Include in the Iist their name, organization and function in the planning process (e.g., City of
Boulder staff: provided review and iaput. Or, John Doe: attended two progress meetings and
provided the following input: ~.
3. Show all maintenance access routes along all reaches. To tlxe extent feasible, the alignment of
these routes shall be coordinated with existing and planned recreational trails identified using
input provided by Sponsors, special districts and other local stakeholders.
4. S~marize cost estima#es of improvements by jurisdiction where those improvements aze
located, by the reach in which the improvements are located and overall project totals.
5. Report estimated costs for maintenance of all facilities, including detention ponds, storm sewer
outfall points, grade control structures, etc. reported in the Final Pdan.
SelrcudPlme Fovmfle Cm~wi CreetmdWwWnlmdCreek7.IDPT00)
ATTACHMENT D
Fourmile & Wonderland Creek COB Internal Review Comments
Sue Prant with Go Boulder
1) Ensure that proposed new bike facildties are more clearly called out on the map.
Response: Mapping has been made available in digital format (AutoCAD format). Bike
facilities can be identified by staff and rendered in more cleazly defined line types and
colors.
2) Make the new path connecting under Foothills Parkway and the RR a priority, as
discussed. This is a prioriry with regards to missing bike and pedestrian connections in
the City.
Response: This intersection is being given special status due to the urgent need for a
safer crossing of ihe railroad tracks. TIP funding is being sought for this project and
stormwater is funding the matching fee for this project. T1P includes 3 project sites but
this intersection is the number one priority.
Maureen Spitzer with Parks and Recreation
1) From the infarmation that you have provided, it appears that only the Violet and Elks
parcels (which are currently undeveloped) will be affected by the flood mitigation plans.
It appears that the stream channel will not be restricted (channelized) in the location of
these parcels and that flood conveyance will occur following historic patterns.
The Violet and Elks parcels are identified as future neighborhood parks in the 2006
Parks and Recreation Master Plan. Both sites are in densely populated areas that
currently do not meet the service area standards for park services. Significant areas of
both parcels appear to be located within the `High Hazard' and `Conveyance' flood
zones. Please confirm that it will be possible to develop these parcels as neighborhood
parks. Typical park development includes planting vegetation (trees and shrubs), re-
grading and contouring to support park activities, installation of irrigation, topsoil, turf
areas, play equipment areas, open air shelters, restrooms and parking areas. It is
critical that this type of typical park development can occur in order to meet the park
service standards identif:ed in the 2006 Parks and Recreation Master Plan.
It is essential to preserve the mature trees and natural features at both locations. In
particular, the tree protection at the Elks site will be extensive. Forestry staff needs to
meet with Greenways engineers/staff on site prior to the projects receiving final approval
to more thoroughly evaluate the existing trees, discuss possible construction impacts and
identify required tree protection.
It appears that the recommendations of the flood mitigation plan are compatible with the
juture development of the Violet and Elks parcels and that Parks and Recreation can
support the recommendations of the study as long as the active recreation value of the
Violet and Elks site will be preserved and these parcels can be developed in a manner
consistent with the other neighborhood park development N~ithin ihe city.
ATTACHMENT D
Response: The above assumptions aze correct and Utilities wil] work with Pazks to
develop these sites in an effective manner with regard to recreation, preservation of
existing trees and flooding.
Bob Crifasi with Open Space aad Mountain Parks
1) From the information that you provided, the only component of this project that could
affect OSMP lands is along Fourmile Canyon Creek in the vicinity of 4th and Lee Hill
road. For that area, the draft project map included a proposal to "excavate north over 2'
deep for additional channel capacity". By my brief examination of the project map, it
looks like the proposed excavation is to be approximately 300 by 100 feet in area. Since,
as you stated, this particular aspect is of generally low priority relative to the key
elements of the plan, fhe likelihood of any acfivities taking place anyiime soon seem very
low. Consequentdy, I recommend that the documents that are forwarded to the various
boards and council for approval (e.g. project approval documents, CEAP, or board
memo statements) state that this project element on OSMP land is tentatively
recommended by your o~ce pending full evaluation by OSMP staff prior to rendering
any frnal decision to implement this element of the overall plan. Further, if this plan
element remains viable, OSMP will need to evaluate whether using this land for flood
purposes would constitute a disposition of OSMP land, thus irigger a disposition review
by the OSBT and City Council.
Similarly, to the extent that new proposals emerge that involve activities on OSMP land,
complete vetting by OSMP staff will be necessary as a prerequisite to an implementation
decision. I believe that if we can get language of this nature included, we can both
minimize the need to expend significant OSMP staff time on this project and
simultaneously avoid the need to prematurely perform detailed resource evaluations that
would unnecessarily delay this important project. As a general matter, OSMP supports
the devedopment of a planned approach to various habitat improvements and struetural
elements (such as designing low impact drop structures that allow fish migration) to
enhance the ecological function of both Wonderland and Fnur Mile Canyon Creeks. The
Greenways Master Plan identifies some opportunities, and there are probabZy others that
arise in response to the specif:c actions proposed in the~lood plan.
Response: Utilities staff has recognized Bob's concerns with regazd to any future
improvements within the above identified area.
2) I recommend clarifying the map legends to avoid creatrng the false impression that
flood channel improvements will occur throughout the high hazard areas aside from the
areas specifically identified on the maps.
Response: Staff will look at updating the legend with more specific language.
Betty Solek with Public Works/Habitats
1) Maps of recommended alternates for both 4 Mile Canyon and Wonderland Creek do
not include specific references to environmental opportunities. I've hand marked these
ATTACHMENT D
maps with specific references that apply to HHZ containment and 100 year
improvements, as well as a few other areas. I've made the additions general so they'ZI
include the detailed opportunities identrfied in Chapter 7.
Response: These comments will be considered by staff and added to selected plan
schematic drawings during preliminary design.
2) HHZ Containment alternate: The legend for both ~/ Mile and Wonderland Creeks
includes a symbol to show "existing property removed from HHZ". Fourmile Canyon
maps show only 3 structures with this symbol on all the maps and 1 don't see any
structures with this symbol on Wonderland Creek maps. Is this symbol missing? If this
observation is correct, what are the benefits of the HHZ alternates? What is the basis of
the public costs shown in Table ES.1 on p. ES-r. Are there roads removed from the HHZ
to address life safety issues? The explanation on ES-4 of HHZ benefits does not explain
how many structures, roads, etc. would be improved or protected. The HHZ containment
alternate also has implications for environmental & habitat preservation. In some
reaches (ex. Reach S of 4 Mile), disturbances due to re-configuration of the channel
create opportunities to improve habitat conditions. However, in Reach IA ofFourmile,
we are lacking habitat data to understand what the potential impacts from HHZ
containment are likely to be. At a minimum, the map should reflect a recommendation to
collect habitat gualiry data to guide design of HHZ overbank excavations.
Response: The symbol is not missing. Property acquisition is only feasible for select
structures due to cost and availability. HHZ containment is intended to contain all of the
truly dangerous flood flows within the channel. A note shall be added to the plans with a
recommendation to collect habitat quality data.
3) Reach 6 Wonderland Creek: Overbank excavation is shown at the upstream end af
this reach. The Greenways MP identifies day-lighting Wonderland Creek north of
Centennial Field. Would there be flexibility in this alternate to day-light Wonderland
Creek and also achieve HHZ containment targeted by overbank excavation further
upstream? Or would it make more sense to do overbank excavation in the section where
2 structures in the HHZ are proposed to be purchased and combine that approach with
day-lightrng Wonderland Creek?
Response: This alternative will be considered and discussed during the upcoming
preliminary design phase.
4) Stormwater Management MP: Are there BMP's or stormwater system improvements
in this plan that should be incorporated into the map of alternates?
Response: Staff is processing this report as a flood mitigation study and has not analyzed
BMP's during this study.
5) In stream construction practices: If approved, the flood projects in this plan represent
a substantial ~~ork effort for many years. The Greenways MP and Chapter 7 identify the
ATTACHMENT D
use of bio-stabilization techniques and grade control as opportunities to enhance aquatic
habitat. The cover letter from UDFCD indicates that the Final Plan includes direction
on design of such design features as drop structures and bank stabilization techniques,
which are to be used for these projects. Generalized design drawings could provide the
opportunity to think thru habitat function and maintenance issues. Some direction is
provided in the notes on Figures 7-3 thru 7-5, but the conceptual design drawings would
provide more details. The Final Plan should also be more specific about habitat and
water quality opportunities that will be incorporated into the Selected Plan.
Response: Staff acknowledges this comment and will address these concerns in the
preliminary design phase. It is the intention of staff to include water quality and habitat
recommendations during this phase of design.
Betty Solek with Public Works/Habitats Additional Comments from Schematic Plan
Sheets
1) Incorporate restoration and environmental opportunities per Chapter 7
Response: Staff will consider restoration opporhxnities and include them in the
preliminary design documents.
2) Reconstruct Farmer's Ditch to remove flood and f:sh migration barrier per Chapter 7
Response: This component of the project will be investigated during the next phase of
design.
3) Preserve high quality wetlands per GWMP.
Response: The preservation of wetlands will be a strong objective during preliminary
design.
ATTACHMENTE
Comments from the Public
for the
Fourmile Canyon Creek and Wonderland Creek Flood Mitigation Update
1) Please include native plantings that enhance habitat for birds and mammals.
2) Please do maintenance to keep channels clear.
3) Please look at including bat houses to support the existing bat population and to
grow that number.
4) Improve 47~' Street culverts.
5) Improve borrow ditches in the spill azea between Fourmile and Wonderland.
6) Pay attention to Montessori pre-school on 19th and Wonderland.
7) Please look at how much water lower Fourmile can handle without impacting
county properties and build a channel on Fourmile to accommodate these flows.
8) Please keep the channel as natural as possible.
9) We would like to negotiate a conservation easement on our property to allow the
continued use of our 30 yeaz old organic garden.
10) Please provide more opportunities for input to designs from people living in the
vicinity of improvements.
11)Please include structures that will remove my property from the 100-year
floodplain.
12) Please expedite process to alleviate cost burden of property residing in the
floodplain due to financial burden of flood insurance.
13) Please include a multi-use path across 28`h at Kalmia Ave.
14) Please look at plans that keep my house out of the floodplain and provide multi-
use paths.
These comments will be considered and incorporated in the next phase of the Jlood
mitigation update (Phase B). This phase will include preliminary design of
mitigation projects and provide an opportunity for the inclusion of public comments.
ATTACHMENT F
Frequently Asked Questions
for the
Fourmile Canyon Creek and Wonderland Creek Flood Mitigation Update
1. When was the last public meeting that allowed residents to review the new
floodplain delineation?
The Fourmile Canyon Creek and Wonderland Creek mitigation update was initiated in
2004. Public process for the new mapping was initiated in 2005. The new document was
reviewed and approved by various City Boards and City Council in early 2006. An open
house was conducted in 2005 to discuss the new mapping.
2. Are the lines on the map permanent? How can I change the mapping if I think it
is not accurate? How do I take myself out of the floodplain?
The floodplain delineatrons within the report are the regulatory floodplain. FEMA does
allow individual properry owners to file a Letter of Map Amendment (LOMA) in order to
adjust the mapping for inaccuracies due to topography. FEMA has initiated an eLOMA
program to expedite the map amendment process.
3. Will Phase B allow for a more detailed analysis? Will a closer look at ground
conditions and hydrology be possible?
Phase B will entail a preliminary design of the chosen alternates for each reach.
Additional detailed information will be obtained and a closer examination of the design
elements will be conducted during this phase of the study.
4. Has a detention facility been considered?
A detention pond has been considered during the Phase A analysis. The size of such
faciliry is space and cost prohibitive. However, this mitigation strate~ will be
considered during Phase B.
5. Has a lazge channel to carry all of the flood flows been considered?
A channel to contain all flood flows would have to be very broad and deep. This makes a
single channel alternative very difficult with the urbanization of these riparian corridors.
Additionally, the cost to implement this type of mitigation would be extremely high.
6. Where is additional information on the project located?
The report is on file at the library and in pdfformat on the City ofBoulder website. The
website also contains numerous other resources to help give citizens additional
ATTACHMENTF
information on this project. Go to www.bouldercolorado.~ov and select City A-Z, F-
Flood, Projects and Programs, Fourmile/Wonderland.
7. Is the City considering wildlife habitat during the mitigation study?
The City is very concerned with providing wildlife habitat during the development of
Jlood mrtigation strategies. This a level of detail that was not studied as part of this
report. However, the Phase B preliminary analysis will actively incorporate habitat
considerations into all flood mitigation designs.
8. Does the 100-yeaz channel require the removal of my trees and shrubs?
The 100 year channel is a broad channel intended to contain the 100 year discharge and
effectively remove structures from the floodplain. The wide nature of the channel allows
engineers to manipulate the shape of the channel to limit the removal of many existing
trees. Some tree and shrub removal is inevitable but the City will make every effort to
retain the existing natural resources of the riparian corridor.
9. Why isn't the City trying to retain the spills from Fourmile Canyon Creek to
Wonderland Creek?
The City has considered this option in the past since roughly half the discharge within
Fourmi~e is spilled south to Wonderland. However, recommendations by Urban
Drainage and Flood Control District (UDFCD} and well-krrown jlood expert, Gilbert
White, have urged allowing flood flows to follow their historical path to Wonderland
Creek. This is because the downstream portions of Fourmile have historically only
received roughly half of the flows and by altering this configuration, it potentially
adversely impacts the downstream flood facilities thaJ would be overwhelmed due to the
increased volume of water. The City is following a course that allows spills to occur as
the existing topography predicates. Mitigation effort recommendations follow this
course.
10. Has the flood mapping study considered all the variables: season, ground
saturation, temperature and snow pack?
The study team attempted to incorporate as many variables as possible into the analysis.
Changes in seasonal rainfall and temperature were explored. Irrigation practices and
rainfall preceding design storms were considered. The model represents basin
conditions that are probable at the time of the storm - late spring to early summer for the
general storm and mid to late summer for the thunderstorm.
11. Have the impacts of global warming been included in the flood mapping study?
The study included the addition and analysis of regional rainfall records for the last 30
years to update the 1972 NOAA Rainfall Atlas. This additional data did not change
rainfall rates in ihe Fourmile Canyon Creek and Wonderland Creek basins and did not
ATTACHMENT F
reflect any trends that could help define the expected impacts ofglobal warming. Given
this, specific affects or adjustment factors to account for global warming could not be
included in the study with any scientific confrdence.
The study team is sensitive to and concerned with the affects ofglobal warming and
climate change. A recent draft American Meteorological Society Statement on Climate
Change, now under review by the AMS Council, has been posted to the AMS web site:
http~//www ametsoc or~olicy/draftstatements/index.html. This draft statement provides
a very good summary of current science consensus on climate change. In general it
supports the likelihood of more frequent, larger and more rntense thunderstorms in the
Western United States.
12. Can the high hazard zone be changed as part of the flood mapping study to
address structures in danger and can we call to discuss structures in question?
The high hazard zone is defined by the physical properties ofJlood depth and velocity,
and is determined without regard to individual structures affected. Changes to the high
hazard zone proposed as part of the flood mapping study or requested by members of the
public must be supported by technical data.
Questions related to specific structures and the impact of the high hazard zone may be
submitted to the project manager (Eric Lessard) or the study team via the project Web
site.
13. How are the floodplain zones (AE, X, Conveyance (Floodway), and High
Hazard) identified on the floodplain maps defined?
The flood zones are def:ned as follows
Zone X: Areas of moderate flood risk that are determined to be within the S00 year
floodplain where there is a 0.2 percent chance of being equaled or exceeded in any given
year; areas in the 100 year floodplain where average depths are less than one foot; and
areas protected from the 100 year Jlood by levees.
Zone X areas are not subject to Zocal floodplain regulations. Zone X buildings are
eligible for the Preferred Risk Flood Insurance Policy (PRP), which is a lower-cost
option for low to moderate risk Jlood areas. Insurance eligibility is based on the FIRM
that is in place on the effective date of the policy, and NFIP grandfathering rules do not
apply.
Zone AE: Areas of special flood hazard (high risk) inside the 100 year floodplain where
flood water surface elevations have been determined. A 100 year~lood event is a Jlood
that has a one percent chance of being equaled or exceeded in any given year.
ATTACHMENT F
Restrictions apply to properties located in Zone AE pursuant to IocaZ Jloodplain
regulations. All development improvements require a flood permit issued by the
appropriate jurisdiction (Crry of Boulder or Boulder County).
The purchase of flood insurance is mandatory for buildings located in Zone AE where the
structure was purchased with a federally backed mortgage. This applies to all mortgages
that are issued by a Federally-regulated lender. The purchase offlood insurance is not
regulated or required by Boulder Counry or the City ofBoulder.
Properties that may be re-designated from Zone X to Zone AE as a result of the flood
mapping study may take advantage of "NFIP Map and Zone Grandfather Rules. " The
grandfather rules recognize policyholders who have "remained loyal customers of the
NFIP by maintaining continuous flood coverage " and/or "built in compliance with the
FIRM that was in effect at the time of construction. " These rules could offer Zower-cost
Zone X flood insurance instead of Zone AE flood insurance after the flood mapping is
adopted.
Conveyance (Ftoodway) Zone: Those portions of the ftoodplain required for passage
(or conveyance) of the 100 year Jlood, based on an encroachment of the floodplain from
the edges of inundation to a point where the 100 year flood profile (or water surface
elevations) will be raised by no more than six-inches (for the city of Boulder, one foot for
Boulder Counry). This defrnition considers a reasonable expectation of blockage at
bridges and other obstructions by flood barn debris.
In the conveyance zone or jloodway, any development, encroachment, obstruction or use
that would result in any increase in the base flood elevation is prohibited. Boulder
County additionally prohibits the development ofstructures for human occupancy in the
Jloodway.
High Hazard Zone: Those portions of the 100 year~loodplain where an unacceptably
high hazard to human safety exists. This is defined as those areas where the product
»umber of velociry (measured in feet per second) times jlow depth (measured in feet)
eqzeals or exceeds four, or where flow depths equal or exceed four feet. The high hazard
zone applies only to lands annexed to city of Boulder.
In the high hazard zone, the construction, expansion or enlargement of any structure
intended for human occupancy or establishment of a new parking lot, is prohibited.
Additionally, any change in use of an existing structure intended for human occupancy
from non-residential to residential is prohibited.
14. Will the flood mapping study impact flood insurance requirements?
Yes. The flood mapping study will replace the currently adopted Flood Insurance Rate
Map (FIRM) used to set flood insurance premiums and identrfy mandatory flood
insurance requrrements. Areas idenirfied in Zone A(r. e. AE and AO) are considered
areas of special Jlood hazard (in the 100-year floodplain) and mandatory flood insurance
requirements apply in this zone. MandatoryJlood insurance is not required in X zones.
ATTACHMENTF
However, flood insurance is available in all flood zones and Jlood insurance premium
rates are adjusted accordingly.
15. What can property owners do to reduce the flood insurance impacts if their
property is determined by the flood mapping study to be in the Zone A
floodplain? Some property owners have heard about a type of "grandfathering"
for flood insurance.
A discussion about flood insurance is presented in the study. In summary, property
owners who currently have and continue to maintain a~lood insurance policy will have
the option of retaining their existing insurance rate status when the new maps are
adopted. This has been referred to as FEMA's flood map "grandfather" rules. Property
owners without flood insurance at the time of map adoption would face the mandatory
flood insurance purchase requirement based on the new floodplain designations.
For more information on the grandfather rules, go to
httn•//www fema o~v/pdf/nfin/hiilsborouQh/grndfthr sht pdf.
16. Could I build a berm to protect my house or property, and would it reduce or
eliminate flood insurance requirements?
Flood protection measures can help mitigate the impacts ofJlooding and reduce potential
losses. Such measures could be as elaborate as constructing a berm around or~lood
proofing an at-risk structure, or as simple as relocating valuable records and possessrons
above the ~lood protection elevation. Construction ofJlood protection improvements may
not adversely impact neighboring properties and must comply with building standards
and engineering practices. They also require a permrt from the City or County to ensure
compliance with floodplain ordinances.
FEMA will not recognize~lood protection or Jlood proofing measures for~lood insurance
purposes. While such measures may reduce the Jlood damage risk exposure, they wrll not
eliminate the mandatory Jlood insurance requirement or reduce flood insurance
premiums.
17. Will the floodplain analysis change if new data becomes available?
The City is committed to providing the most thorough and accurate floodplain mapping
possible. If new survey data or rainfall data becomes available, it will certainly be
incorporated in a timely manner.
18. Pve lived on this creek for 30 yeazs and never witnessed anything even remotely
close to the level of flooding yow study is suggesting. Why do I need to worry
about the 100-year flood?
The 1 DO year flood is as inevitable as rain. It will occur at some point and the City has a
responsibiliry to prepare and protect citizens living in the Fourmile Canyon Creek and
ATTACHMENTF
Wonderland CreekJloodplains. Rainfall prediction is based on historical records going
back as far as 100 years. The statistical probability of a 100 year storm event is 1% at
any time. Thrs is rather low but certainly within the realm ofpossibilities.
ATTACHMENT G
Update: City of Boulder Flood Mitigation Planning
Fourmile Canyon Creek & Wonderland Creek
As noted in the time line illustrating the work performed since 1997, the city of Boulder
continues to assemble flood information for the corridor including both Fourmile Canyon
Creek and Wonderland Creek. Previous flood mitigation planning occurred in 1999-2002
but had been suspended while the city worked to revise the flood mapping based on new
information. The Federal Emergency Management Agency (FEMA) adopted the new
flood mapping submitted by the city in eazly 2007. http://www.fema.gov
Current Status: Flood Mitigation Planning Again Moving Forward
Phase A Report - Alternatives Analysis
Flood mitigation plans to create a safer flood corridor are detailed in the new report from
flood engineers at Love & Associates (Love). Love & Associates have completed the
evaluation of various flood mitigation alternatives as part of the Phase A Report.. The
findings within the report aze supported by the Urban Drainage and Flood Control
District (UDFCD). http://www.udfcd.org The Phase A Report is available at the city's
flood utility website.
The Love recommended approach considered the creeks on a reach-by-reach basis
utilizing guidance provided by the city's Independent Review Panel (IRP), Alternatives
were defined that consider the unique topography and geometry of each section or reach
of the two creeks. This information was combined with the location and proximity of
structures to determine recommended alternatives for each reach. Based on the
alternatives defined in the Phase A Report, the best flood mitigation alternatives are to be
selected.
Alternatives Considered
Several altematives were considered in the Phase A report as described below:
Full Containment of 100-year Flood Event Containment
In some reaches of the creeks, Love is recommending constructed channel improvements
to fully contain 100-year flood waters.. Ideally, these improvements would be constructed
to replicate a natural creek, but will likely require some amount of creek stabilization in
the form of rock retaining walls and drop structures. This altemative has been
recommended by Love in areas where the benefits of reduced future flood damages
outweigh the costs of constructing the improvements. The option also has the advantage
of precluding the need for floodproofing individual structures and flood insurance
requirements for federally insured mortgages.
Containment of High Hazard Zone for 100-year Flood Event
In other reaches of the creeks, Love is recommending containment of only the high
hazard zone portion of the 100-year flood event. Again, these improvements would be
constructed to replicate a natural creek and require less creek stabilization than the full
containment option. This type of improvement is recommended in areas where the costs
of future flood damages are not as significant. Property owners near the creeks will still
be impacted by shallow flooding under the 100-year event and would be encouraged to
floodproof their individual structures and carry flood insurance.
ATTACHMENT G
Floodproofing of Individual Structures
As requested by the IRP, the late Dr. Gilbert White and Love performed an analysis of
properties that could be protected from flooding by the application of floodproofing.
Floodproofing is any action taken on-site of an "at risk" property to protect structures
from floodwaters. Floodproofing is accomplished by providing physical barriers to the
flood waters or elevating the structure. The cost of floodproofing individual structures
would be borne by the individual property owners.
Culvert Crossings at Intersecting Roadways
There are a number of culvert crossings along Fourmile Canyon Creek and Wonderland
Creek that are old or undersized. In order to prevent flooding caused by inadequately
sized culverts, the City intends to replace a number of the crossings as funding
opportunities present themselves. In addition, a multi-use underpass will be combined
with the flood mitigation projects at appropriate locations.
Property Acquisition
In some instances, the most effective remedy to reduce flood risk is to physically remove
certain structures from the flood hazard area. Several properties have been identified for
acquisition in the Phase A Report.
Coordination with Greenways Program Objectives
In order to incorporate all of the Greenways program objectives, an internal review was
completed by staff from Open Space, Parks & Recreation, Transportation, Habitats, and
Wetlands. These comments were reviewed and shall be included in the Phase 2 report.
NEXTSTEP5
It is anticipated the Phase A Report will be presented at a public heazing with the Water
Resources Advisory Boazd on October 15. Public heazing with the Planning Boazd and
City Council aze also anticipated in late 2007 or early 2008.
Provided there is consensus regazding the selected plan then the Phase B- Preliminary
Design will be initiated and should be completed in 2008. The preliminary design will be
reviewed as part of the city's Community and Environmental Assessment Process
(CEAP).
Money has been budgeted in the 2008-2013 Capital Improvement Program (CIP) budget
to begin to fund selected flood mitigation work. It is likely complete implementation of
the selected flood mitigation plan will take several decades to complete.