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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 FLOODWAY/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. I 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 20`h day of October, 2008, by the following vote: City A AYES: Barrett, Harris, Nau, O'Brien, Vice Mayor Rabbitt, Mayor Torliatt NOES: None ABSENT: Freitas ABSTAIN: None ATTEST: _ City Clerk M Resolution No. 2008-200 N.C.S. as to Page I 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 License Number City Clerk APPROVED AS TO FORM: Taxpayer I.D. Number Petaluma Business Tax Certificate Number City Attorney APPROVED: Department Director APPROVED: Risk Manager APPROVED: Administrative Services Director Resolution No. 2008-200 N.C.S. Page 2 WEST Amho, CONS ULTANTS, INC. SCOPE OF WORK 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) A two-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 overbaak of the Petaluma River from the confluence with Willow Brook Creek to Corona Road will be evaluated with the _2D-module.—Both-areas-comprise-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. A field survey will be conducted to obtain more accurate bankline elevations along portions of Willow Brook Creek where LIDAR 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. 2/008-200 N.C.S. Papc 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 of this proposal, but are subject to change based on quotes from potential aerial survey subcontractors. WEST will update the GIS ground surface data and XP-SWIVIM cross section data in the Denman Flat area based on the revised topography. Task 3 XP-SVVMM 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 of portions of Kelly and Thompson Creeks into underground storm drains will be added to XP- SWN M based on as-builts provided by the City. In addition, after upgrading the XP-SV0V1M license to 1000 nodes, the Kelly and Thompson Creek model 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 Creek to 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 the hydraulics (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 estimating 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 infiltration parameters, runoff method catchment shapes, and Manning's n 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=SWMM. Therefore, —WEST -will -reconfigure the 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 I 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, Nanning's n values, and weir/culvert flow assumptions. The I 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 (NUIRW) elevation of 6.34 feet NAVD88. The higher of the routed 100-year (or 500-year) hydrograph in XP-SWMM based on the M. -IU-IW 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 (LOMR) 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 FIRMs, 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 Willow 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 LOMR 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 of the required data to complete the project tasks and submit the LOMR package to FEMA for review. hcsoiution No. 2008-200 N.C.S. Page 5 I6870 West Bernardo Drive Suite 34C 91 Y San Diego, CA 92127-1671 (B5B) 487-9376 VLTCONS ITA NT6,INC. (859)487-9448fax C1"eat(M Name City of Petaluma Petaluma FEMA mapping with 2D, Amendment No. 1 COST ESTIMATE September 12, 2008 Emily Assn©ate 179.00 Project Manager 141,00 Staff Engineer 87.00 Hydro- lo& 93.OD Clerical/ Twaniie 43.D0 Tote] Tesk Hmas COST It LABOR COSTS TASK No. DESCRIMM 1 Expand Model to include 2D —esge from Vk' low Brook to Corona Rand rHodes' Devdopmad (a) ld 7ocadO to tie-in on tributaries 241 12 1 36 4,428 (b) Create models for l D- and 50.ycar events to ttydate FIS discharge tahl le plow 48 48 6,76 (c) Rtvise tadvw data in model to match st y of road and low chords 40 40 9 ) A Evaluate with and with" floodwall scenarios far 100- and 500-y7 events for A99 40 16 7,128 2 Subtotal Update Model Too hy in Deon an Flat 0 152 52 16 p 64 27,444 no additional tasks 3 Subtotal 3LP-SiVMM Modd Runs 0 0 0 0 D 4ddid nal FToodxwy Tana (a) Determine sn'otnmg of floodway fr® DFIRM work by otbtas 40 40 9 } (b) Ovtziay existing floudway Iin =-nib XP cross section rvarbes and set limits to av&cmditim 24 8 4,1281 (c) Reduce 2D model a#cot to CVent ovnrlap widTfloodway 16 2 (d) Camven 5na) model from 2D to I for submittal to FEMA 50 16 9,536 (a) A5den flu dway upstream of Corona Road in reflect. and recluse 60 76 9 g57 f3DDdway upstnam of Petaltmza Blvd due to b2b ground in left ovetbmk 4 ' Subtotal P are FEIAA Latter of Map Recision 0 190 16 64 p 3-4,134 LOMR Rfporf (a) Add] time for preparsticni ofreport and appenclicics 4 40 20 20 20 104 10,61 (b) Additional meetings/coordinationwith /C unty&MMA 48 48 6,766 (c) 13 v6ap st® for suss ser;tion labeling m FIRMs 1 24 16 41 5,051 (d) Assist City v7ffi tedmical parbons of A99 ppbwom 4 40 20 2 B4 9,95 (e) Add1 time for oases to FEMA camw=ts, 1st rotnd (as needed) 60 24 40 1''4 14,269 (f) Add] time for reiqmacs To FEMA comments, 2nd round (as needed) 40 16 16 72 8,52 (g) Final rt—isims - 2 24 ]6 24 76 62 B4OS e O!Hugo Brook Brcukoat from Z—A0 m AE (BFF�) (h) Prepare revised 100- and 5Da-yr dam ford atm then zero for breakout 16 7 6 2,26 0) Create water surface grids for 1 OD-, and 500-yr events iu vicinity of bmakoia 16 B 2 3,000 0) Create BFEs for breakout 6 15 24 7 _ 616 (k) Post-prvccss 1 DO -)rear 13- lain to move =0 islands S 4 12 1,500 (1) Update MT-2 forms, --% print aff—d -ap panels 21 16 16 6L6!71 4,360 5 Subtotal Coordioatioo end Report 13 340 96 160 42 77,165 D£]R ]rer�oas (a) M=g, Feb 2D07 tmace/dmentim model data urith a root 2D model 15 16,1 (b) 3dentify nodes to r®ove to -Did a -seeding 1000 nodes 5 5 705 (c) Run 7 D0.year srmiir anon wnt� tmaces and det.-man 30 4 — -- 34 4,65 (d) Perfmm one iteration of terrace/detention ounce after evaluann results g 4 4 26 . 3,75 Subtotal TOTAL HDURS TOTAL LABOR COST 0 75 0 8 0 BS UX, 13 757 164 266 q2 63g 5750,062 B. DIRECT COSTS COST Travel for Meetings ttiih Cotatty/City/FEA!A (2 days - air. rental car, hotel, meals) ],) 0()Add3tional W cbFx mcctmg 20 TOT4L DIRECT COST [_ 57,300 TOTAL FOH.4LL T.4STi.5' S757,361 Resolution No. 2008-200 N.C.S. Page 6