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HomeMy WebLinkAboutResolution 2008-200 N.C.S. 10/20/2008Resolution No. 2008-200 N.C.S. of the City of Petaluma, California AUTHORIZING THE CITY MANAGER TO EXECUTE THE AMENDMENT NO. 1 TO THE PROFESSIONAL DESIGN SERVICES AGREEMENT WITH WEST CONSULTANTS, INC. FOR PROFESSIONAL CONTRACT SERVICES FOR THE COMPLETION OF THE FEMA FLOODWAV/FLOODPLAIN REMAPPING EFFORT WHEREAS, the City Council has determined that the preparation and submittal of an updated regulatory FEMA floodway/floodplain boundary to the Corps of Engineers is timely and appropriate; and, WHEREAS, the work undertaken to create and. maintain the City's XP-SWMM model has been completed under contract with WEST Consultants for the completion of the General Plan 2025 and associated Environmental Impact Report; and, WHEREAS, the continued use of WEST Consultants, through professional contract services is needed to complete the work effort begun in June 2007 to ensure that all appropriate studies are conducted for the submittal of the FEMA remapping application; and, WHEREAS, WEST Consultants, Inc. is a professional firm experienced in the preparation and completion of the FEMA remapping submittal and associated modeling studies necessary to support said remapping submittal; and, WHEREAS, the additional contract services for the FEMA remapping effort are estimated at $151,362, for a total amount of$309,416. NOW, THEREFORE, BE IT RESOLVED by the City Council of the City of Petaluma that the City Manager is authorized to execute the Amendment No. 1 to the Professional Design Services Agreement with WEST Consultants, Inc. attached hereto as Exhibit A for professional contract services for the completion of the FEMA floodway/floodplain remapping effort, in the amount of $151,362, with a contingency of $20,000. Under the power and authority conferred upon this Council by the Charter of said City. REFERENCE: I hereby certify the foregoing Resolution was introduced and adopted by the Council of the City of Petaluma at a Regular meeting on the 20t° day of October, ?008, by the following vote: AYES: Barrett, Harris, Nau, O'Brien, Vice Mayor Babbitt, Mayors orliatt NOES: None ABSENT: Freitas ABSTAIN: None ATTEST: _ City Clerk M Resolution No. 2008-200 N.C.S. City A as to Page 1 EXHIBIT A AMENDMENT NO. 1 To PROFESSIONAL DESIGN SERVICES AGREEMENT FEMA FLOODWAY/FLOODPLAIN REMAPPING EFFORT Account No. 66600 THE AGREEMENT made and entered into at Petaluma, California, on June 27, 2007, by and between City of Petaluma, a municipal corporation and a charter city (hereinafter referred to as "City") and WEST Consultants, Inc. a California Corporation (hereafter referred to as "Consultant"), is hereby amended to include the following: 1. The scope of services shall be revised to include the Scope of Work (copy attached) for modeling efforts. 2. The original cost estimate for completing the services shall be increased from $158,054 to $309,416. The proposed budget for the supplemental work included in this amendment is $151,362. THIS AMENDMENT NO. 1 is hereby executed this day of , 2008.. CITY OF PETALUMA WEST CONSULTANTS, INC. By City Manager ATTEST: Title City Clerk License Number APPROVED AS TO FORM: Taxpayer I.D. Number City Attorney Petaluma Business Tax Certificate Number APPROVED: Department Director APPROVED: Risk Manager APPROVED: Administrative Services Director Resolution No. 2008-200 N.C.S. Page 2 ~i! ,, p CONSU L7ANTS,ING. SC~r Fj ®F P~~®j~j1 City of Petaluma XP-SWMM Model Enhancement and FEMA Floodplain Mapping WEST Consultants, Inc. (WEST) has prepared this scope of work at the request of the City of Petaluma (City) to update the FEMA 100-year and 500-year floodplain and floodway boundaries for the Petaluma River to reflect the flood control project in the downtown area and floodplain changes in other areas of the City. The update will be based on more accurate topography and modeling methods. Flooding sources to be evaluated include the Petaluma River, Willow Brook Creek, Corona Creek, Capri Creek, Washington and East Washington Creeks, Lynch Creek, Kelly Creek, Thompson Creek, and Adobe Creek. Prior to submitting the request for map change to FEMA, the current city-wide XP-SWMM model will be enhanced to provide more detailed flooding information. This will be accomplished by adding the following components to the model: 1) Atwo-dimensional (2D) module to evaluate overflows from Willow Brook Creek to Corona Creek, and left overbank flows of the Petaluma River in the vicinity of Industrial Avenue (from the confluence with Willow Brook Creek to Corona Road). 2) Field survey data to obtain top of bank elevations for key areas along Willow Brook Creek. 3) Aerial survey/digital topography for the Liberty, Wiggins, Wilson, and'Marin areas (Denman Flat) to provide a better representation of flood detention for this area. 4) Bridge and culvert data based on as-built drawings per FEMA submittal requirements. The following tasks are anticipated to accomplish the above model enhancements and to prepare/submit the map change request to FEMA: Task 1 Expand model to include 2D coverage for Willow Brook Creek to Corona Rd. WEST will convert the current link node data in the left overbank of Willow Brook Creek to a 2D grid within XP-SWMM. The area to be converted will include flow paths of the Willow Brook Creek overflow as observed during the New Year's flooding (December 31, 2005). In addition, a portion of the left overbank of the Petaluma River from the confluence with Willow Brook Creek to Corona Road will be evaluated with the - 2D-module-Both-areas comer-ise-approximately-470-acres.-Each_grid-element_will_be_assigned_an.elevation based on interpolation between LIDAR data points, unless more accurate field survey data is available. In that case grid elevations would be adjusted manually. Afield survey will be conducted to obtain more accurate bankline elevations along portions of Willow Brook Creek where L1DAR coverage was poor. Approximate costs for this bankline survey work are included as part of this proposal, but are subject to change based on quotes from potential survey subcontractors. The 2D model grid elements along the stream-side boundaries will be linked to adjacent I D model nodes of Willow Brook Creek, the Petaluma River, .and Corona Creek_ The cross sections in the 1D model that are adjacent to the 2D grid will be trimmed to the edge of the 2D grid to avoid double counting the flow area. Grid elements representing blockages (buildings) or partial blockages (fences, culverts, etc.) will be incorporated in the 2D grid as necessary. Resolution No. %~?08-200 N.C.S. Pa~c 3 Task 2 Update Model Topography in Denman Flat An aerial survey subcontractor will be retained to provide 2-foot contour interval topography and aerial photography with 3-inch pixel resolution for Denman Flat (approximately 2000 acres). Approximate costs for this work are included as part ofthis proposal, but are subject to change based on quotes from potential aerial survey subcontractors. WEST will update the GIS ground surface data and XP-SW1VIM cross section data in the Denman Flat area based on the revised topography. Task 3 XP-SWMM Model Runs Prior to running the model, bridges/culverts not yet included in the model but shown on the effective Flood Insurance Study (FIS) profile plots will be added to the model based on the as-built drawings to be provided by the City. The diversions ofportions of Kelly and Thompson Creeks into underground storm drains will be added to XP- SWMM based on as-builts provided by the City. In addition, after upgradingthe XP-SWMM license to 1000 nodes, the Kelly and lfiompson Creek mode] will be combined. with the model for the rest of the City. Other areas to be added to the model include Corona Creek between Adobe Road and Ely Road, Lynch Creek from the golf course to just upstream of Bionda Road, Washington and East Washington Creeks from the golf course to just upstream of Adobe Road, and Adobe Creekto apoint just downstream ofManor Road. Adding these areas will involve revising the hydrology (subdividing subbasin areas, recalculating time of concentration, evaluating curve numbers, etc.) and thehydraulics (adding cross section data based on available topography, estimating Manning's n values, measuring reach lengths, adding culvert data, etc.). If detailed topography is not available for estuating cross section geometry, additional survey may be required. Approximate costs for this work are included as part of this proposal, but are subject to change based on quotes from potential survey subcontractors. A three-day field reconnaissance trip is proposed to verify bridge/culvert dimensions in cases where as-builts are not available, to confirm Manning's n values as necessary, and possibly to provide guidance during the bankline and cross section surveys. After updating the model, the New Year's Storm and December 27, 2005 Storm will be analyzed to verify the previous calibration. If necessary, adjustments will be made during the calibration to SCS curve numbers, SCS hydrograph shape factors, runoff method uifiltration parameters, runoff method catchment shapes, and Manning's rz values and bridge pier blockage assumptions. After calibration, the 10-, 50-, 100- and 500-year storms will be simulated. Although the 2D module will be used in the calibration and the design event simulations, FEMA has not ------ formally-approved-this-new feature of-XP=S~VMM-Therefore,-WEST-will-regionfgure Fhe revised-l-D-model to reproduce the 2D model results in the Willow Brook Creek overflow area. There is a possibility that the 1D model will not accurately reproduce the 2D model results, in which case the 1D solution will still be adopted for the FEMA submittal. In order to approximate the 2D results, links and nodes will likely be added to the 1 D model where significant flow was predicted, and minor adjustments will likely be necessary to 1 D model cross section geometry, Manning's n values, and weir/culvert flow assumptions. The ]D model would then be submitted to FEMA without. any mention of the 2D analysis to avoid complicating the review process. The downstream boundary condition for the model runs will be the Mean Higher High Water (1\~~4W) elevation of 6.34 feet NAVD88. The higher of the routed 100-year (or 500-year) hydrograph ui XP-S~VN1M based on the 1V1.I-III\~J boundary condition and the 100-year tide Stillwater elevation of 9.2 feet NAVD88 (or Resolution No. 2008-200 N.C.S. rage 4 500-year elevation of 9.4 feet NAVD88) will be the basis of the floodplain mapping for the lower Petaluma River. Task 4 Prepare FEMA Letter of Map Revision The submittal to FEMA will include all required components for a Letter of Map Revision (CONK) request, including the following: - Completed MT-2 forms for each flooding source - Floodplain workmaps showing location of cross sections, base flood elevations (BFEs), 100-year and 500-year floodplain limits, etc. - Revised Flood Insurance Rate Maps (FIRMS) showing proposed changes to the floodplain and floodway limits Due to the comprehensive change to the City's F1RMs, WEST will also revise the FIS tent and all associated tables, including the Summary of Discharges, Summary of Roughness Coefficients, and all Flood Profile exhibits. Most of the City streams are currently designated Zone AE, which includes BFEs. Portions of Willow Brook Creek, the W illow Brook Creek breakout, and Corona Creek are currently designated Zone AO (base floodplain with sheet flow, ponding, or shallow flooding where base flood depths are provided) or Zone AH (shallow flooding base floodplain where BFEs are provided). WEST will coordinate any changes to these zone designations with the City and/or Sonoma County. WEST will attempt to keep the floodway limits at their current location unless otherwise directed by the City and/or Sonoma County. One exception is the recently completed floodway in the downtown area, where the floodway limits will be reduced. Task 5 Coordination and Report WEST will summarize the analysis supporting the FEMA submittal in a comprehensive report, which will be included with the LOMR package to FEMA. The analysis for the 2D area will be summarized in a separate memorandum to the City. WEST will respond to comments by the City, Sonoma County, and FEMA regarding the LOMB submittal. Follow up of a more detailed nature, not related to any omission on our part, is not included in this scope of work. WEST will coordinate progress with the City with up to 4 web meetings. Schedule We expect that it will take approximately 6 - 7 months from notice to proceed and receipt ofthe required data to complete the project tasks and submit the LOMR package to FEMA for review. hesoiution No. ZUOi;-Z00 N.C.S. Fage ~ I6870 West Bernardo Drive y Suite 340 91 ~ . Y San Diew, CA 92127-167] (658) 487-9376 CONaU ITA NT6,INC. (658)487-9448faz CI'rotfJob Name ~Y of Petalnnw Peialama FEMA mapping with ZD, AmendmeotNo. 1 COST ESTIMATE September I2, 2008 Im...m.~ 7M7 R.n.r Hoody Asso©ete 779.00 Project Manage 141.00 Staff En¢ineer 87.00 Hydro- 3ogist 93.00 C]ericaU Techttici 43.00 Tote] Task Hotas COST LABOR COSTS TASK No. DESCRTP170N 1 Fspand MadrJ do ioclnde 2D coven from Rrli low Brook to Corona Rnad Mudd Devdnpmart (5) Id lncationa m 1]e-ln an tl]~)e6 24 ] 2 36 4,4?8 (b) G*a,. models far I D- and 50.ycar events to tt-tla>z fly discharge tahl le plow 4S 48 6,76 (c) Bruise ailvert data in model m mmnh sTa-vey of road and Iow chords 4D 40 9 ( (d) Evalvtde with and withotri floodwell scenarios far J D0. ®d 500.yr evems fm A99 4D ] 6 7,126 Subtotal 0 152 52 I6 D 84 27,444 2 D ate Mndd Too b is Deom ea Flat no addititmal tasks Subrotal ~ 0 0 0 D 3 ~7'-SIVMM Model Runs 4ddIDOaaJ F[nobwy Tana (a) Dete:®ine stati®mg of floodway from DFHtM wtn'k by oibas 40 4D } 9 (b) Overlay erasting floodway limits wilb XP cross section rtarbes ana set i~iu m ctmditimt 24 8 q l ~ (c) Reduce 2D model oSCOt m eveat overlap widTflootiway ~ ] 6 2 {d) Ctmvcrt 5aal mold from ?D m 1D for solmmitral m FEMA 50 J 6 6,536 (e) Pridea flootiway upstrema of Corona Road m reflect. ®d raluce 60 7 6 9 g57 floodw em of Pcraltmte B)vd due m his>b grtnmd m left overbmk ' Sobtotal 0 190 16 64 D 34,1 4 P are FH1viA Loner of Ma Rc~sba LOMB R on (s) AdtO time for .w of report and dicta a 40 20 20 20 7 ] 0,81 (b) Additional mee[ingslcoordinadtm with /Crnmb{FEM.4 48 48 6,766 (c) Dcvr3op st® f~ avss swtion Sabeling ®FlRMc 1 2a 76 4] S,D51 (d) Assist City with inr}mical ®-tions of A99 'cau® a 40 20 20 9,95 (e) Add] time for tnises to FEMA coIItmeuts, 1 ri rotmd (as tueeded) 60 24 40 1''4 14,266 (f) Add] time for oases m F13v1A comments, 2nd rotmd (es neodcd) 40 16 ] 6 72 6,52 (g) Fine] rt rn~ons - 2 24 ] 6 24 76 62 B,OS e q fllow Brook Brcakoar from ZaaeAO m.4E tBFFsJ (h) are revised 100. and 500. data ford atu they zero for breakout 16 7 6 Z,~ (i) Create wemr sta-face grids fot J 00., and 500.yr events in vicinity of Mtakoia 7 6 B 1 3, (j) Create BFEs for breakout B 75 24 _ 7 616 (k) Post-process ] 00.1rear fl o lain to r~ovc mtall islands S 4 12 1 $ (1) llpdam AfT-2 forms, tn~ affcclzd m ands 2 ] 6 ] 6 6 4D 4,360 Subtotal 13 340 % 160 42 671 77,155 5 Coordioatioa eod Report DEIR Jrerations (a) MQ Fcb2D07 tmacc/damtion model data u;th aurcot ?D model l5 16 ~ ~ X (b) 7deo ~ nodes m remove to a•oid a:-seeding 1000 nods ~ 5 5 706 (c) Run 7 D0.ycaT stm~it anon unto terraces and dccattion 3D a - ~ -- 34 4,60' (d) Perfm-m one iteration of terrace/detention souse afro evaluator results g 4 4 26 ~ 3,75 Subtotal 0 75 D 8 0 63 ll~19 TOTAL HDi7R5 TOT.,4L ]ABOR COST ]3 757 164 166 q2 636 5750,061 B. DIRECT COSTS COST Travel for mee~n s ~~~ih Colmty/City/f'EA!A (2 dfll~s -air. rental car, hotel, meals) 7,) 00 Addioona] W ebEa mcctinv 20 TYIT4L DIRECT COST 57,300 TOT.,SL. FOH.gLL T.4STi5' 5757,361 Resolution No. 2008-200 N.C.S. ~~l~C 6