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HomeMy WebLinkAboutItem 06.hApril 4, 2011 4 l iilkeintle Item No, APPROVE JOINT POWERS AGREEMENT BETWEEN THE VERMILLION RIVER WATERSHED JOINT POWERS ORGANIZATION AND THE CITIES OF FARMINGTON AND LAKEVILLE FOR COST SHARE RELATED TO UPDATE OF LOCAL STORM WATER MODELS AND AUTHORIZE BARR ENGINEERING TO PROCEED WITH HYDROLOGIC MODELING FOR PHASE 1 Proposed Action Staff recommends approval of the attached Joint Powers Agreement between the Vermillion River Watershed Joint Powers Organization ( VRWJPO) and the cities of Farmington and Lakeville for Cost Share Related to Update of Local Storm Water Models and authorization for Barr Engineering Co. to proceed with hydrologic modeling for Phase 1, North Creek Subwatershed. Overview The VRWJPO has completed an existing conditions hydrologic model setting peak discharge rates on all major drainage ways at corporate boundaries throughout the watershed. The hydrology in Lakeville's Stormwater Resource Management Plan was not updated with our comprehensive plan in 2008 due to this study being undertaken by the VRWJPO. The study is now completed and discharge rates set. The VRWJPO allocated $50,000 in cost share to local communities to assist in updating storm water management models to be consistent with the VRWJPO's existing conditions model. The updates will serve as a tool to verify that peak discharge and runoff volume leaving the cities remain in conformance with the VRWJPO requirements. Barr Engineering modeled the existing conditions for the VRWJPO and will use the same model in more detail for Lakeville and Farmington, In a cost saving effort, the cities of Lakeville and Farmington jointly submitted a request to VRWJPO for 50% cost -share assistance for hydrologic modeling updates. By doing both cities together, discharge rates between cities will be in agreement, which was a selling point to the VRWJPO. The estimated cost of the updates in the Vermillion River Watershed is $284,500 with a 50% cost share of $142,250, Because the amount exceeds the $50,000 budgeted in 2011, it was decided that the update would be completed over a two year period. The cost for Phase 1 of the update is $95,400, with a VRWJPO cost share not to exceed $47,700, of which $27,750 is allotted to Lakeville and $19,950 to Farmington. Remaining phases are proposed to be completed next year subject to VRWJPO funding. Barr Engineering Co. has prepared a scope of work to update the existing surface water models, which will be integrated with the existing VRWJPO model for uniformity purposes. Phase 1, scheduled for completion in 2011, includes modeling of North Creek. Two recent storm events have caused Cedar Avenue to overtop, and this area has been identified as a priority for evaluating existing flood conditions. Phases 2 -4, to be completed in 2012, will include the South Creek, Middle Creek and Crystal Lake subwatersheds. Primary Issues to Consider Future discharge rates identified in Lakeville's current Stormwater Management Plan do not match the allowable flows adopted by the VRWJPO. Supporting Information • Joint Powers Agreement between the Vermillion River Watershed Joint Powers Organization and the cities of .rmington and Lakeville for Cost Share Related to Update of Local Storm Water Models • B. s •ineering Co, scope of work for revised hydrologic modeling, dated December 15, 2010 Ke h H. Nelson, City Engineer Financial Impact: $23,850.00 Budgeted: Yes Source: Surface Water Management Fund Related Documents (CIP, ERP, etc.): Notes: Dakota County Contract1352.8 JOINT POWERS AGREEMENT BETIP EEN THE VERMILLION RIVER WATERSHED JOINT POWERS ORGANIZATION AND THE CITIES OF FARMINGTON AND LAKEVILLE FOR COST SHARE RELATED TO UPDATE OF LOCAL. STORM WATER MODELS VVHEREAS, Minn. Stat. e 4.71.59.autnorizes local governmental units to jointly or cooperatively exercise any power common to•the contracting, parties; and VVH:EREAS, the. Vermillion River Watershed joint Powers Organization Is a watershed management. body consisting of Dakota :and Scott Counties (VRWJPID) governed by the Vet RiverWaterslied Joint Powers Board (VRVVJPB) and is Chareed with carrying out the duties set forth in Mind Stat. §:§ 103E3.211 to 1035.255 and as otherwise provided by law; and WHEREAS, the Cafes- of Farmington and (c011ecfivery referred to. as "the Cities) ore:governmentel units and oblitical Subdivisions of - the Stale of Minno.sota; and WHEREAS, the Cities desire to update their respective storm water models with , "the VRVV,IP • Watersnert P2.fl int standards; and WHEREAS., tnelCities in a collaborative effort, developed: a scope of' worido.rugdating their respective surface water mode-(Project): and WHEREAS, the Project consists:of five phases andthe Cities are seeking cost Sharelfundine-from The VR.VVJP0 for Pnase 1 of the Project; and WHEREAS, the estimated cost of Phase 1 of the Project 95,400,00; and WHEREAS, the VRVVJP0 adopted its Watersined Plan on November 3, 2005, and said Wetersnon Plan contains a Cost SharIng Policy that provides guiclance to the VR:WiFB regarding the cost sharing bee.veen the VRINJPO and potential partners fOF various watershed management efforts affectino the Vermillion River 'Aiatershed; and WHEREAS. the Cost Sloarlhg Policy sots forth.priCtIties for impfovemeritt affecting the-Vermillion River Watershcd and Phase ofihe Project qualifies for up to a 5D% cost snare; and NOW, THEREFORE, in.conSideration of:the mutual promises and benefits the the: Cities short derive from:this - Agreemerit, the VRVVJPO„throburi the VRWJPF, and trie hereby - enter into-this Agreement for the purposes:Stated ARTICLE PURPOSE The pourpcsciotthis Agres.meilt sl.° define the responsibilities and cost - snaring obligations cif the VRWJP0 and bre Mies •for Phase 1 df Project as more-WIN described in Exhibit 1, attached hereto and incorporated herein by this retefefic ARTICLE 2 PARTIES The parties to this Agreement are the Vermillion River Watershed Joint Powers Organization (VMACIPO} atttioq throogii ts ibint Powers Board (VRMIPB) and the City of Farmington, Minnesota, and the City of Lakeville, Minnesota fcbilectively "the ARTICLE 3 TERM This. Agreement shall be effceLiva thadate of the signatures of•the taints Agre.ement anti shall remain in effect until December 31, 2011, or until completion by th'e parties of their respective obligation's under this Agreement, whichever OCCUTS.first, unless -earlier terminated by law or - according to the provisions of this Agreernent. ARTICLE 4 COOPERATION The VRWJPO and the Cities agree to cooperate and use their reasonable efforts to ensure prompt implementation of the various provisions of this Agreement and to, in good faith, undertake resolution of any dispute in an equitable and timely manner. ARTICLE 5 PAYMENT The VF&,/,1P0 shall eS+,_ share with the Cities in an amount equal to 50V6 cif the total cost incurred by the Ctties for Phase 1 of the Project, but not to exceed the amount of Forty-Sever Thousand Seven Hundred and No1100 D0021S (547,700.00) (Agreement Maximum). 01 the Agreement Maximuni, $21,750.00 is allotted to the City of Lakeville for its costs incurred tor Phase 1 of the Project: and 519,950.00 is allotted to the City or Farmington for its costs inclined for Phase 1 &the Project. 52 The VRWJFO shall make payment to tne Cities after Phase 1 of the Project has boon completed and the VritiVdP0' has been provided with a final report as required by Section 6.2 below. The VR`iithiP0 shall matte paymenttolhe Cities within 46 days following receipt of the final report and receipt: of an T ctetaillng, the oasts incurred by the Cities in conducting Phase 1 of the Project 5.3 The VRW.iP0 may refusd to pay any claim that is not spec 2:uttiorized by this Agreement, Payment lot a ciaim shall nut:preclude:the VRV\IJF-'0 from questioning the propriety bf the claim, The VRVVJP0 reserves the right to offSet enV Overpayme,nt or disallowance of claim by reducing future payments. ARTICLE 5 CITY'S OBLIGATIONS 6,1 AUTHORIZED PURPOSE The cost.share funds provided undertnis may :only be used by ths.Citios, for the payment of costsiassociate.d.in:condueting Phase 1 ofthe Project as.described in Exhibit 1. 6.2 FINAL REPORT, Folizwiino cornpietion-ofPhase 1 ofthe Project-, the Cities shaltprovide to the VRVVJP0 tetehnicat memorandum tharoutlines.tbe completion.of-modeling elements as well astrierfinding's, conclusions and rocornmendations.cfiPtiaiseil efF 6.3 ACKNOWLEDGMENT. The 'Cities shall appropriatelyracknowteddethe ton.cling - assistance provided by the VRWJPD in any promotional materials, signage, reports, publications-, notices,..and ereseritations relating to the Project. This SCOW shall survive the expiration or termination of this Agreement 6,4 COMPLIANCE WITH LAWS/STANDARDS The Cities shell abide by all federal, state, oriccal laws, statutes. Ordinances, rules arul regulpticins:in conducting :the Project. ARTICLE .7 TERMINATION 7,1 IN GENERAL.. Any party may terminate 'this:Agreement:tor cause bygivinusevarcdays' written notice or without cause .hy. 30-dayS' written notice, of its intent to-terrninale, to the other parties.. Such notice. to tern*late for-ead shutl speciry the circumstances warranting terminatiortofthe:Acireement. Oauso.--snali mean a material breach:of Agreement and any supplemental agreements ame.adments thereto. N:atice. of Termination shuil bemade day certifie.d mail' or prsonal delivery tchthe' authorized •Ci).resarqaTiva.or other parties, Termination of Agreement shall not discharge. any liability, responsibility or rightof any parry, which arises from the 'Dejorrin an se a ar failure to a eq ately perform the terms of this Agreement prier to the effective date of termnation. 7.2 TERMINATION BY VRVVJPO. FOR: LACK.-OF FUNDING.. Notwithstanding any provision of this Agreement to the contra.ry., the VRVVJPO may mrn ditsiy terminate this iliorteerrie.nt it dues not obtain funding from thsrMinnesota I.. enisieture, Minnesota, Agencies, or other firiding.source, or if it's funding gannet he continued a levei sufficient to allow payment of•ho•arnounts due Agreement, Written notice of terrnination sent by the VR-V\fjP0 to the•Citie.s by facsimile ifs sufficient .notice. under this section. T.he VRWJPO not obligated to pay for any services that ere nrovicisitt after written netica.of termination for lack offuriduig. The VR will notrbe SSE,'SS8d any penalty or damages if the Agreement is terminated due to lack offunding. ARTICLE 8 GENERAL PROVISIONS 8.1 LIA8 Each. part9 to this Agreement shall be.tiabte for the 'acts Of its officers employees or acients and the results thereof to The - extent authorized by law and shall not be•resoonsible the acts of the ether - party,. it Officers, .em:pio.e.es- agents. The provision:5 of the Tort Claims Act, Minn, Stat. ch. 466 and other applicable a.i. Nubility of the V.RWW and the-Cites. This section shall survive the expiration or termination of this Agreement. 8.2 AUTHORIZED..RE.PR.ESENTATIVES, The following named per are designoted the Authorized ReuresentativeS...ofthro partia.s for purposes of this Agreement. These persons have,authoritil tebind the party they represe.nt and to consent-to modifications, except that the authorised representative-5 shall. h81/5.,-4 only tae authority spe.cifically g.e.narally granted by their respectivegoveirning boards. Notice required to be provided pursuant this shall be provided to the following named cersonshand addresses unless otherwise Stated in this Aereerinent, or tna m thisiAcreerneriti - TO THE VIRVVJPE: Joseph A. Harris or successor, Chair Vernalltion River Watershed LicintFpwers.Orgarlization 14955 iGaluxie Avenue Apple Valley, MN 55124 Teleph.cnei (952) 8i91-730 TO FARMINGTON, Todd. Larson or suose Mayor City .Of Farmington 430Ernird St. Fairrrington, N1N5.5-02 Tplephone: .(85 )-230-68.00 TO LAKEVILLE Mark Ba DWS' r successor, Mayor City br,LakeMlie 20195 Helyelte L.ake.ville, MN 55044 Teieenonei (95:4985-4420 In addition, notification to the VRVVJPO regardirici termination of this Anreernont shall he provided to the Office of the Dakota County Attorney, Civil Division, 1590 Highway 55, Hastings, Minnesota 55033. LIAISONS, To assist :the parties in the dayiiito-day performance of this Agreement and to ensure compliance and provide ongoing nonsaltatien, n ueisor shall be designatecf.by the VR and the Cities Thie VRVVJF0 and the Cities snail keep each-other coratinuaili,,t informed, ir writing dif any charade in the desion.atee lialsbe, Al the time' of execution ofiithis..Agreernent, the:foil persons .are the..designated VRWJP0 Latent Murk Zabel Telephone; (952) 891-7549 ".; Farmington Liaison: Lakeve Liaison: Kevin Scnorzmen Tele Phone: (651).280-6800 Keith Nelson Telephone: (952) 9Z.54.500 MODIFICATIONS, Any alterations., - variations, medifica. tions, -or waivers. of the - provisio - ns of this A shall only Pe valid when they nave been reduced to writini, approved by the partie.is- respective Spards, and signed hy the Autddrizeici•Fiepresertativ.es ftbn VRAAJJP and the 8.5 RECORDS REFETION.AND -A.UOTTS. Each perty's bonds, records, docitiments, papers, :accounting procedures and practices, and .dther records relevant to thisAgreen are sub:tact to tne-e„xamination, duplication., transcription and audit by the•cither party,. the LegiStatiye Auditor or State-Auditor un Minn. Stet. § 160.05 sLibb, 5, If the cost share. funds provided under this.Agireement useitederal funds 8 also subject to review by the Comptroller General of the United' States and his or her approved repre..sentative.. Following terrninatiori of this Agreement, the parties must keep these records for at feaSt years or tenger if any audit-in- progress needs a longer retention time,. DEFAULT: FORCE MAJEURE. No party shall be liable to any other party far any loss or damage, rasultirig from e delay or failure, to perform due ta unforeseeable acts or eve.nt outside the defaciting partvis reasonable. control, providing the defaulting oartvigives notice to tne other party es soon as possible. Acts and events may include acts of Gob, acts of terrorism, war, fire, flood, epidemic, acts of civil or r3 authority, end naturail disasters. ASSIGNMENT. No party may.assign any:of itc . rights under:this Agresi-ment iixithotrt th.a.ofier watten-consent of the other parties. Said - consent may be subject conditions. 8,8 G VfNMENT DATA. PRACTICES. For purposes of this Aareedient, ali data on ndft4dLieis calle.cLed, :created, MCE(Ved, maintained or disseminated shall be administered consistent with the Minnesota Government Dote Practices Act, Minn. Stat. ch. 13 GOVE LAW, JURIrSDICTION AND VENUE. This Agreement :shall henovr, by and construe in accordance:with:the -substaintiv.eiand procedural tawetof without.giVing effect to the prinCiples of- conflict of laws_ All proceedings related-1p th Agreement -shall be venued r he County of Daic State of M This section shall - sunfive the expireilibri :or te.rmination Of Mis.Aareernent. 0,1 MERGER. if his Agreement - is:the-fin - et ex of the atireernent of the .parties and tile. con and - exclusive statement ef the terms agreea.upon - and shatt supersede negotations, understanclinge, or agreements. 8,11 SEVERABILITY, The provisions of this Agreement.shail be deemed - severable. If any part of this Agteernentis rendere.tri void, invalid, orune..nforpeable,...such•re,indering.-shaill not affect thei..validlty and .enforcaability- remainder of this Agreement unless theipart or darts void...invalid or otherwi shell substantially 'impair the- value idt• the- Entire Agreement - With - re to either -party. IN WITNESS WHEREOF, the parties heratc .executed th Agreement on the clate(s) indicated ClTY OF FARMINGTON By APPROVED AS TO FORM J . A.fie .qsistoni Dakofe County Attorney Date VRtAl Res, NQ, 11-13 K-11-65 By By By . Todd Larson, Myer Date of Sl , City C;Ierk Date df Sign.ature: CITY OF LAKEVILLE Mark Bellows, Moyer Date. of Signature: City Dell> Date of i„icrial.trra VERMILLION RIVER WATERSHED JOINT POWERS BOARD joseon A. Harris., - Chair Date-of Signature: December 15, 2010 Mr. Keith Nelson City Engineer City of Lakeville 20195 Holyoke Ave Lakeville, MN 55044 Mr. Kevin Schorzman City Engineer City of Farmington 430 Third Street Farmington, MN 55024 Dear Mr. Nelson and Mr. Schorzman, resource . natu •a(iy. ord environmental consultants Subject: Revised Hydrologic Modeling for the Cities of Farmington and Lakeville Enclosed is a scope of work for the Cities of Farmington and Lakeville to develop a hydrologic model that can be integrated with the existing Vermillion River Watershed Joint Powers Organization (VRWJPO) XP -SWMM model. An updated hydrologic model would serve as a tool to verify that peals discharge and runoff volume leaving the Cities remain in conformance with the VRWJPO requirements. The updated hydrologic model for the Cities would be developed to the same level of detail that is reflected in each respective Water Resources Management Plan (WRMP). Should the Cities decide that an increased level of detail is required in the model so that additional storm sewer networks or storage areas may be evaluated, we can provide an updated cost estimate following discussion with City staff. Phased Approach Based on recent discussions, we understand that the Cities would like to complete the modeling in four phases beginning with North Creek, and ending with a fifth phase for either updating the current WRMP or preparing a technical memorandum summarizing the model revisions and results. Separate cost estimates have been developed for each phase of work. Figure 1 shows what area each of the four modeling phases will include. • Phase 1: Revise the hydrologic model for the North Creek drainage area + Phase 2: Revise the hydrologic model for the South Creek drainage area (South Creek, Marion Lake, and Farmington Outlet) .c:xine.rinr,f Co, 4700 We 77th Street, Su4e 200, Al6nocapohs, MN 55435 952.8322600 w: . con, December 15, 2010 Page 2 • Phase 3: Revise the hydrologic model for the Middle Creek drainage area • Phase 4: Complete hydrologic modeling for the remaining drainage areas with the Cities. For Lakeville this includes the Orchard Lake and Crystal Lake drainage areas in the northwest portion of the City, and for Farmington this includes the Vermillion River rnainstem and adjacent drainage areas in the southeast portion of the City. • Phase 5: Prepare a summary of the model updates completed. For the City of Lakeville this includes updating the Stormwater System District Analysis (Section 4) of the City's WRMP with results from the updated model analysis, and preparing a technical memorandum for the City of Farnmington. As discussed with the Cities, there are advantages to updating the hydrologic modeling soon after the completion of the VRWJPO modeling. Barr staff members involved with the recently completed Vermillion modeling are familiar with the City's drainage patterns as well as the recently adopted VRWJPO peak discharge and runoff volume standards. This allows for a smooth transition into updating the model to meet the needs of each City. Efficiencies and Cost Savings By working together, Lakeville and Farmington can develop a single model accepted by both communities to use for stormwater management, and potentially receive funding from the VRWJPO. Certain modeling efficiencies will be realized by partnering on this project, such as batch processing some model inputs (e.g., land use data, watershed divides). Additional cost savings will be realized in the future by a reduction in potential differences between two separate modeling efforts. These potential conflicting results would be circumvented by the proposed partnering. Unfortunately it is difficult to quantify the cost saving associated with these efficiencies. Once completed the models will be available to make future changes to the Flood Insurance Studies for Lakeville and Farmington, which may be required for new stream crossings, regional flood control efforts, or regional water quality projects. Thank you for this opportunity. Please contact me at 952- 832 -2781 or Scott Sobiech at 952- 832 -2755 if you have questions. Sincerely, Leonard J. Kremer, PE Scott Sobiech, PE, CFM Vice President Project Manager Enclosures Scope of Work: Updated Stormwater System Analysis for the Cities of Farmington and Lakeville The Vermillion River Watershed Joint Powers Organization (VRWJPO) has completed a hydrologic model for the Vermillion Watershed that defines the existing stormwater flows (using 2005 land use) at municipal boundaries in the watershed. The municipalities and townships will be required to implement stormwater hest management practices so that these stormwater flows will not increase with future development. The hydrologic model created for the VRWJPO is in the XP -SWMM format. It is recommended that updated modeling for the Cities also use the XP -SWMM format for the following reasons: An XP -SWMM model will be compatible with the modeling done by the VRWJPO (i.e., the existing VRWJPO model can be used as a downstream boundary condition for many of the City's hydrologic models) . • An XP -SWMM model will allow both Cities to combine their models to analyze how stormwater management decisions affect the rest of the system in both communities. • XP- SWiv1M. is capable of modeling to much greater detail than the current Lakeville model which uses the HEC format, or the Farmington model which uses the HydroCAD format. • The XP -SWMM mode] is not as conservative as the HEC model in terms of runoff volumes and peak discharges. • It is much easier to use GIS to input data into the XP -SWMM fonnat than it is to either the HEC or HydroCAD formats. • The XP -SWMM model provides both hydrologic and hydraulic information so including dynamically accounting for backwater impacts, it will provide peak discharges, runoff volumes, flood levels for ponds and storage areas, as well as flood profiles for stream channels. • The XP -SWMM models will be able to be used for future revisions to the Lakeville and Farnington Flood Insurance Studies that may be required for new stream crossings, the construction of regional flood control efforts or regional water quality improvement projects. The XP -SWMM models developed for the Vermillion River Watershed Management Organization are being reviewed by the Minnesota Interagency Hydrology Review Committee and will be approved in the next several weeks. Phased Approach It is recommended that the XP -SWMM. modeling be completed in four phases: • Phase 1 includes the XP -SWMM modeling of North Creek (including the North Creek drainage district in Lakeville and the Apple Valley drainage district in Farmington). Two recent storm events have caused Cedar Avenue to overtop, and it is our understanding that the City of Lakeville has identified this area as a priority for evaluating existing flood conditions. This phase also includes evaluating alternatives to reduce the flood elevations at Cedar Avenue in Lakeville. • Phase 2 includes the XP- SWMM modeling of the South Creek Watersheds (including the South Creek and Marion Lake drainage areas in Lakeville and the Lakeville drainage district in Farmington). Eau E n Bring C rr pa Pane ScO.pe of Work, Deceertbnr 2G1 • Phase 3 includes XP -SWMM modeling of the Middle Creek Watersheds (including the Middle Creek drainage district in Lakeville and Farrnington drainage districts Al through A8). • Phase 4 includes XP -SWMM modeling of the remaining watersheds within the Cities. This includes Orchard. Lake and Crystal Lake in Lakeville, and the Vermillion. River, Prairie Waterway, Biscayne, and South Branch drainage districts in Farmington. • Finally, Phase 5 includes incorporating all of the revised model results into one final document. For the City of Lakeville this includes updating the WRMP, and for Farmington this includes a technical memorandum of the modeling revisions completed. If the City of Farmington would also like their current plan updated we can provide a revised cost following discussions with City staff. Methodology An XP -SWMM model will be created for each subwatershed within the Cities representing existing (2005) land use conditions and existing storm sewer systems. Prior to creating each XP -SWMM model, we would review the current subwatershed divides in each of the Cities' respective WRMPs and make any necessary corrections. The existing land use map that was developed for the VRWJPO model will be used for this project, and information from the City's electronic storm sewer database will be used to supplement the stormwater conveyance system currently modeled in the VRWJPO XP -SWMM model. This data will be input into the models, and the models will be run for the 1 -year, 2 -year, 10 -year, 50 -year, and 100 -year, 4 -day storm events to remain consistent with the storm events used to develop the VRWJPO standards. This design event hyetograph was developed so that the peak of the storm occurs at the center with decreasing intensities building out. By design, critical storm events with lesser duration are nested in the overall 4 -day event distribution for similar drainage areas. That way only one design event is required to obtain critical flows throughout the watershed (i.e., location of a subwatershed in the drainage network is irrelevant because the critical duration storm event for each subwatershed is nested within the 4 -day precipitation hyetograph). This methodology is similar to the methodology used to develop the standard SCS Typ II, 24 -hour storm hyeto therefore, the 4 -day frequency based design storm developed for the VRW.IPO modeling has a similar peak intensity of the SCS Type II 24 -hour design event and shorter duration frequency based storms. As a result, the proposed model simulations will test all stoup durations without having to simulate storms of varying durations. Model results at the municipal boundary will be compared with results from the VRWJPO XP -SWMM model to verify that peak discharges and volumes meet current VRWJPO standards, Discrepancies between results from the two models will be addressed or discussed with the City and the VRWJPO. Proposed storm sewer alignments and planned regional basins from the Cities current WRMPs will be added to the XP -SWMM model to develop a future conditions model. The Cities future conditions (2030) land use from the Cities 2008 Comp Plan will be reviewed and adjusted if necessary to create classifications that are similar to those used in the VRWJPO XP -SWMM model. Peak discharge and total runoff volume at the municipal boundary will be reviewed to verify that model results comply with current VRWJPO standards. Future storm sewer and regional basins will be resized if needed to ensure they meet VRWJPO standards. If additional basins are required to meet VRWJPO standards, proposed locations of additional basins will be discussed with the City and will be sized to meet VRWJPO standards. Barr Eng° , "'lisp. Company Page. 2 t. of Work ascamber 2010 After the modeling has been completed, the model description and results will be provided to each City. Model results for the City of Lakeville will be integrated into the City's WRMP. In the current WRMP, the 1995 model information is contained in Section 4: Stormwater System District Analysis. This section will be replaced with updated text including a district -by- district model description, results, and recommendations. A discussion of how the City's modeling is integrated with modeling completed by the VRWJPO and all data tables and figures that changed as a result of the modeling efforts will be included as part of this revision. If new issues or implementation tasks are identified as part of the modeling effort we will discuss updating Section 6: Assessment of Issues and Opportunities, and Section 7: Implementation Plan with the city at that time. It is assumed that all updates will be deemed as minor plan revisions that only require VRWJPO staff review and the updates will not require approval from the watershed boards, the Metropolitan Council, the Lakeville City Council, or other, jurisdictions. A. draft will be submitted for Lakeville staff review and comment before it is finalized. Similarly model methodology, results, and background information will be provided to the City of Farmington in a technical memo format. Should the City of Farmington decide to update their WRMP following completion of the modeling effort a cost estimate can be provided. Phase 1: Modeling of the North Creek Subwatersheds Two recent storm events have caused Cedar Avenue to overtop, and we understand that the City of Lakeville has identified North Creek as a priority area to evaluate the existing flood conditions. The estimated cost for Phase 1 assumes that the City will authorize the proposed model revisions, and work will be completed in early 2011. Our work scope for Phase 1 includes the following tasks: Task 1 — Project Management (Lakeville $2,200; Farmington $2,200) This task includes regular email and other correspondence with the Cities during the Phase 1 work. Additionally, two meetings will be held with the Cities during this phase of work: one project kick -off meeting and a second to present initial model results. Task 2 — Review Subwatershed Divides and Develop Hydrologic Model Parameters (Lakeville $6,200; Farmington $5,900) Barr will review the current subwatershed divides for the North Creek Watershed and update the divides as necessary to reflect changes in existing drainage patterns. This task does not include subdividing existing suhwatersheds in the Cities WRMP to add additional detail to the XP -SWMM model, except as needed to more accurately evaluate the drainage characteristics and remedial measures upstream of Cedar Avenue in Lakeville. Hydrologic model parameters will be calculated for all subwatersheds following the same methodology used to develop the Vermillion River XP -SWMM model. In locations where subwatershed divides stop at the municipal boundary, the subwatersheds from the VRWSPO model will be used to account for drainage area that flows into each City. These drainage areas outside the s rr a gIn ering Company Page 3 r r of Work, December 2 01 municipal boundary will not be subdivided as part of the model update and will be modeled with the same level of detail as the existing VRWJPO XP -SWMM model. Task 3 — Develop Hydraulic Model Inputs (Lakeville $8,000; Farmington $6,000) We will create a water resources inventory, including wetlands, low areas, ditches, storm sewers, culverts, and other drainage features. This inventory will be completed using data provided by the Cities or relevant information used in the development of the VRWJPO XP -SWMM model. As part of our base map preparation, Barr will review the Cities' electronic storm sewer database to organize information for input into the XP- SWMM model and identify records that are missing the data. The City naming convention used in the database provided to Barr will be used to develop the XP -SWMM model. This map will be used to identify locations where additional storm sewer information is needed (i.e., missing from the database). As -built plans of crossings will be collected and reviewed; cross section data will be reviewed and compared to data in the VRWJPO model; and where available high water marks and rainfall data will be reviewed. The model will be adjusted to mimic observed field conditions as appropriate using available data. .It is assumed that the Cities will be able to provide the storm sewer data as plan sheets (in electronic format or as hard copies), or will conduct field surreys to collect or verify information if necessary. Task 4 — Develop Existing Conditions XP -SWMM Model (Lakeville $17,100; Farmington $12,800) Upon receipt of the necessary storm sewer data from the Cities, Barr will create the hydrologic and hydraulic model of the North Creek watershed using the XP -SWMM software. The model will incorporate existing (2005) land use, storm sewer, channel cross sections, and detention storage data. To detetuiine the cause of recent flooding along North Creek the XP -SWMM model will include subdividing watersheds where necessary, adding additional culvert or storm sewer information where necessary, or adding additional cross sections along North Creek. The XP -SWMM model is intended to be a tool for the Cities to identify locations where BMPs are needed to meet VRWJPO standards, and can be used by the Cities to verify that future BMPs are sized appropriately to meet City and VRWJPO rate and volume standards. The model will be run using the 1 -year, 2 -year, 10 -year, 50 -year, and 100 -year 4 -day rainfall events that were used to define peak discharges and runoff volumes for the VRWJPO. At the municipal boundary, the updated model will be tied to the existing VRWJPO XP -SWMM model to account for downstream tailwater conditions. Additional hypothetical design storm events (i.e., SCS 24 -hour, 10 -day Snowmelt Event, etc.) can be simulated using the XP -SWM.M model at the Cities request, and will be completed on time and expense in addition to the cost estimate provided for Phase 1. The critical elevations for the 10 -day and 30 -day snow melt events included in the existing WRMP do not need to be recalculated unless the tributary drainage area has changed. Barr End €neer cad Comp Page 4 Scope of WEuork. Dec €a -mb 2010 Task 5 — Develop Future Conditions XP -SWMM Model (Lakeville $8,200; Farmington $7,200) Following completion of the existing conditions Barr will revise the XP-SWMM model to reflect future conditions. Hydrologic model parameters will be revised to reflect changes in land use. Regional stoin, water ponds and planned storm sewer modifications described in the current WRMP will be incorporated into the future conditions model. For this analysis stormwater ponds that are required for smaller developments will not be added to the model at this time. The Cities should update the model with these at the time of development as they could potentially have an impact on the size of required regional basins. Model results will be compared to VRWJPO standards at the municipal boundary to verify peak discharge and total runoff volume standards are met. If necessary planned regional basins will be resized or added to comply with current VRWJPO standards. The model will be run using the 1 -year, 2 -year, 10 -year, 50 -year, and 100 -year 4 -day rainfall events that were used to define peak discharges and runoff volumes for the VRWJPO. At the municipal boundary, the updated model will be tied to the existing VRWJPO XP -SWMM model to account for downstream tail water conditions. The existing VRWJPO XP -SWMM model will be used for downstream boundary conditions because it is assumed that current VRWJPO standards will keep future peak discharges and runoff volumes comparable to current conditions. Additional hypothetical design stone events (i.e., SCS 24 -hour, 10 -day Snowmelt Event, etc.) can be simulated using the XP -SWMM model at the Cities request, and will be completed on a time and expense basis in addition to the cost estimate provided for Phase 1. Task 6 — Summary of Methodology and Results (Lakeville $6,200; Farmington $5,800) The modeling methodology will be summarized for each city. The North Creek subwatershed results, figures, and tables will be compiled as part of this task, and they will be formatted to be placed directly into the Cities WRMP. An electronic (PDF) draft of this document, the figures, and the tables will be provided to the Cities for review and comment. Edits to this draft will be incorporated into the final Section 4 or technical memorandum, completed as part of Phase V. Task 7 — Evaluate Scenarios for the Current North Creek XP -SWMM Model (Lakeville $7,600) Two recent storms have caused Cedar Avenue to overtop, although the 1995 City of Lakeville hydrologic model and the VRWPO model show that Cedar Avenue should not be flooded during the 100 -year storm event. The discrepancy between the "real world" flood levels and the modeled flood levels can be a result of various causes: issues with the modeling of the bridge, the channel, or the tributary watersheds, the simplified nature of previous models, or the storms that caused the overtopping of Cedar Avenue were more intense than the hypothetical event. A hypothetical storm will be run through the more detailed model to determine if it can still be concluded that the bridge will not overtop. If the model shows the bridge still does not overtop, it will be necessary to discuss what level of protection the City would like to provide at Cedar Avenue. If the model shows the bridge does Barr Enueneerin Scope of Work, Company mbe 2Ory Wages overtop, different alternatives will be evaluated in order to reduce the flood level to the 100 -year flood elevation. Three scenarios will be evaluated: constructing additional storage along North Creek, providing additional discharge capacity at Flagstaff and Cedar Avenues, and a combination of the storage and increased capacity. The results of the three scenarios will be reviewed and tabulated, and presented to the city in a brief technical memorandum. Phase 1 Cost Estimate: City of Lakeville: $55,500 City of Farmington: $39,900 Phases 2 through 4: Modeling of Remaining Subwatersheds Phases 2 through 4 will involve similar scopes of work to those described in Phase 1, Tasks 1 through 6 for the South Creek subwatershed {Phase 2), Middle Creek subwatershed (Phase 3), and the remaining portions in each City (Phase 4). However, Phases 2 -4 will not involve the increased level of detail proposed in Phase I to evaluate recent flooding along North Creek. Rather than reiterate the task descriptions in Phase 1, Table 1 provides a simplified task description and proposed task costs associated with Phases 2 -4. Table 1. Phases 2 and 3 Proposed Tasks and Estimated Costs 1 Project Management 6 Summary of Methodology and Results Phase 2 Phase 3 Phase 4 $2,900 $1,400 $2,100 Phase 2 Phase 3 Phase 4 $ _ _._ 700 __._ .._ ..._. $1,800 $2,1 2 Review Subwatershed $4,400 $2,600 $5,300 $2,600 $3,700 $5,300 Divides & Develop Hydrologic Model Parameters Develop Hydraulic $9,100 $2,800 $8,900 $2,500 $8,200 $8,100 Model inputs 4 Develop Existing $14,400 $7,000 $12,900 $5,200 $15,800 $11,300 Conditions XP -SWMM Model 5 Develop Future $7,100 $5,400 $7,500 $3,900 $7,300 $6,800 Conditions XP -SWMM Model $5,000 $2,400 $5,800 $4,000 $5,500 $4,800 Total $42,900 $21,600 $42,500 $18,900 $42,300 $38,400 Barr Epginecrine comp r y Page E+ Scope of Work, Decernber2010 Phase 5: Updating the City WRMP The work scope for Phase 5 includes the following steps: Task 1 -- Project Management (Lakeville $2,400; Farmington $2,400) This task includes regular email and other correspondence with the Cities during the Phase 5 work, as well as one meeting to discuss comments on the revised Section 4 and final technical memorandum. Task 2 — Revise Text and Figures (Lakeville $6,900; Farmington $5,300) The watershed and results summaries completed in Phases 1 -4 will be compiled as part of this task, and the comments received in the previous phases will be incorporated. We will submit a draft Section 4 to the City of Lakeville and VRWJPO staff for review and comment, as well as a draft technical memorandum to the City of F armington. As part of this task we will review the entire plan and provide a recommendation to the City on other parts of the plan that should be revised to reflect the updated model results. Task 3 — Incorporate Comments and Prepare Final Revised Section 4 (Lakeville $5,400; Farmington $2,600) The City of Lakeville and VRWJPO staff comments will be incorporated into the final revised Section 4, and City of Farmington comments will be incorporated into the final technical memorandum, We will provide the Cities with five hard copies, and one electronic copy. In addition we will provide Lakeville with one electronic copy of the entire plan with the revised Section 4 incorporated. Task 4 (Optional) — Revise Additional WRMP Sections It is possible that the model results and revisions to Section 4 may affect other sections of the City's WRMP. For example the updated modeling may show additional areas of flooding that should he discussed in another section. A detailed scope of work and cost estimate for this task will be provided upon completion of Phase 4, Task 2, when we are able to determine if, and to what extent, the updated modeling affects other sections in the current City WRMP. Phase 4 Cost Estimate, excluding optional task: Lakeville $ 14,700 Farmington 510,300 Barr Eirn941 any Page 7 Scope of Work. December 2010 Optional Phase 6- Estimate Current Treatment Efficiency of City Stormwater Ponds (Lakeville $22,400) It is our understanding that City of Lakeville staff would also like an estimate of the treatment efficiencies for each of the approximately 400 stormwater ponds located within the City of Lakeville. Treatment efficiencies for total phosphorus (TP) and total suspended solids (TSS) will be calculated for each pond as part of this optional phase. If the City elects to proceed with this option, it is assumed that the City of Lakeville will provide a GIS coverage of the 400 stormwater ponds to be evaluated. P8 watersheds pollutant loading models have been developed for several of the watersheds within the City of Lakeville that can provide estimates of the TP and TSS removal efficiencies of the modeled ponds within the watersheds. Watersheds modeled in P8 include the Lee Lake, Crystal Lake, Orchard Lake, and Lake Marion watersheds. The models for Lee and Crystal Lakes were developed as part of the Crystal, Keller, Lee, and Earley Lakes Nutrient Impairment Total Maximum Daily Load (TMDL) Study (Barr, 2010, draft) for the Black Dog Watershed Management Organization (BDWMO) & Minnesota Pollution Control Agency (MPCA). The Orchard Lake and Lake Marion PS models were developed as part of the Orchard Lake Diagnostic- Feasibility Study (Barr, 1998) and the Lake Marion District Diagnostic - Feasibility Study (Barr, 1997), respectively, for the City of Lakeville. The TP and TSS removal efficiencies for ponds located in within these watersheds will be extracted from P8 water quality modeling for average annual climatic conditions. It was assumed that approximately 100 of the 400 stormwater ponds to be evaluated would be included within the existing P8 models. For the remaining ponds (approximately 300), a more simplistic method will be used to estimate the TP and TSS removal efficiencies using long term removal efficiency curves. Field inspection will be conducted to estimate the average depth of the pond. This cost estimate assumes that City of Lakeville staff will be available to complete field inspections for each pond. If City staff are unable to assist with data collection an alternate cost estimate is provided below, Additionally, watershed characteristics, including the drainage area and the amount of impervious area, will be developed to apply the removal efficiency curves. For some ponds, the City's existing subwatershed GIS coverage may be sufficient. However, for other ponds, subwatershed delineation may be necessary. The surface area of the ponds will be based on the GIS coverage provided by the City: The summary of the P8 modeling as well as the estimates based on the long terra removal efficiency curves will provide the City with information regarding the generalized removal efficiencies of the existing stormwater ponds. The total estimated cost for this Optional Phase 6 is 822,400 assuming City staff is available to assist with pond inspections and estimating average depth. If City staff is unable to assist with field inspections then the estimated cost for this phase is $61,900. Should the City determine it is necessary to include more than 400 ponds in this investigation additional ponds can be added to the analysis at $155 per stormwater pond. If the City would like a more detailed estimate for select ponds following this initial effort, a separate cost estimate can be provide following discussions with City staff. ma aQ' y ei Work. ec ember 2910 Proposed Schedule Phase 1 Phase 2 (Tasks 1-5) Phase 3 (Tasks 1-5) Phase 4 Phase 5 $55,500 $42,900 $21,600 $42,500 $14,700 Total $177,200 $39,900 $18,900 $42,300 $38,400 $10,300 $149,800 July, 2011 December, 2011 May, 2011 September, 2011 December, 2011 I As future work phases are authorized the project schedule will be adjusted. Barr Engineering Company Page Scope: oWk. Dacenaber 2(110 C"Z O O m om C © ©G m ©m O 20 n l !