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HomeMy WebLinkAbout2.b. Comprehensive Stormwater Management Plan UpdateCITY OF ROSEMOUNT EXECUTIVE SUMMARY FOR DISCUSSION AUGUST 13, 2003 COMMITTE OF TH E WHOLE AGENDA ITEM: Comprehensive Stormwater Management Plan Update PREPARED BY: Andrew J. Brotzler, P.E., City Engineer AGE O Z 8 ATTACHMENTS: Memorandums APPROVE BY: //111� At the August 11, 2003 Utility Commission Meeting, the Commission will be reviewing a proposal received from the MCES for the over sizing of the Empire WWTP Outfall to accommodate stormwater discharge from the City of Rosemount. Following review of this item by the Utility Commission, Staff will review with Council the Utility Commission's recommendation. The Utility Commmission will also be reviewing options to move forward with the approval of the City's Comprehensive Stormwater Management Plan by Dakota County and the Vermillion River Watershed Management Organization. These options and the Utility Commission's recommendation will be reviewed with Council for discussion. RECOMMENDED ACTION NOTES: For discussion only. WSB & Associates, Inc. To: From: Date: WSB & Associates, Inc. 4150 Olson Memorial Highway, #300 Minneapolis, MN 55422 (763) 541 -4800 (763) 541 -1700 (fax) Memorandum Rosemount Utility Commission Pete Willenbring, P.E., WSB & Associates, Inc. Andrew Brotzler, P.E., City Engineer, City of Rosemount August 6, 2003 Re: Review and Analysis of Metropolitan Council Environmental Services Division Proposal WSB Project No. 1005 -55 It is the purpose of this memorandum to provide a review of the alternatives available to the City of Rosemount to carry water from the City to the Mississippi River in conformance with the City's Comprehensive Stormwater Management Plan. As you are aware, the City's Comprehensive Stormwater Management Plan anticipates the construction of a stormwater trunk line from the Bloomfield development, easterly, to the Mississippi River. As part of the construction of the outfall, the City has been investigating combining the construction of our system with the proposed MCES treated effluent outfall from the Empire plant. Based on a recent response from MCES concerning potential options for combining these two systems, we have completed an updated analysis of the alternatives that are now available to the City of Rosemount to convey water to the Mississippi River. A general listing of the alternatives that are now available, along with general highlights of these alternatives and their estimated cost are outlined below: Option 1 — Build System as Currently Proposed in City of Rosemount Plan • Project would be constructed by the City of Rosemount. Outlet will have capacity of 40 cfs at Bloomfield 5t Addition. • Outlet will have capacity of 380 cfs at Trunk Highway 52. C: IDocuntents and Settings) jjIocal SettingslTemporary Internet FilesiOLKI1080503- memo- ab.doc Rosemount Utility Commission August 6, 2003 Page 2 of 4 • Outlet will have capacity of 765 cfs at Mississippi River. • This outlet will reduce flood storage required in the City by 7,000 acre -feet when compared to other alternatives identified herein and could reduce pond construction costs by $10 to $60 million compared to other alternatives outlined herein. • This alternative will allow water to drawdown from a 100 -year snowmelt within 10 days. • The cost for this outfall project is estimated at $30 million. • This project would need to be constructed in 10 -15 years. Option 2 — Utilize Only Excess Capacity that is Available in MCES Outfall for'as Long as Possible, Build Separate City System When Needed. It is anticipated that in the near future, approximately 40 cfs of excess capacity will be available in the MCES outfall. This excess capacity will gradually be utilized by MCES, with it being anticipated that no additional capacity will be available in 2025 -2030. MCES has indicated that the City of Rosemount would need to pay MCES to utilize the excess capacity available in this line when it is used. The details of this arrangement have yet to be established. Specifics regarding this alternative are provided below: • Outlet will have capacity of 40 cfs at Bloomfield 2 °a Addition. • Outlet will have capacity of 40 cfs at Trunk Highway 52. • Outlet will have capacity of 40 cfs at Mississippi River. • This outlet will reduce flood storage required in the City by 800 acre -feet and reduce ponding costs by $1.1 to $6.6 million when compared to other alternatives identified herein. • This alternative will allow water to drawdown from a 100 -year snowmelt in about 200 days. • The cost for utilization of this system is not yet established. • An outlet would still need to be constructed in the future, but the construction project could be delayed for 15 to 25 years. C: Documents and Settings l jjlLocal Settings l Tempormy Internet Fi1esDLK1 W80503- memo- ab.doc Rosemount Utility Commission August 6, 2003 Page 3 of 4 Option 3 — Utilize excess MCES capacity in the short -term, as well as pay MCES to oversize the system so 40 cfs will always be available for stormwater runoff from the City of Rosemount. In the short-term, 75 cfs would be available, but this rate would be reduced to 40 cfs by approximately 2030. MCES has indicated that the cost to the City of Rosemount to oversize the system to accommodate this rate would be approximately $5 to $7 million. More specifics regarding the cost and benefits of the system are provided below: • Project would be constructed by MCES. • Outlet will have capacity of 40 -75 cfs at Bloomfield 5"' Addition. • Outlet will have capacity of 40 -75 cfs at Trunk Highway 52. • Outlet will have capacity of 40 -75 cfs at Mississippi River. • This outlet will reduce flood storage required in the City by 1,500 acre -feet and reduce funding costs by $2 to $12 million compared to other options. • This alternative will allow water to drawdown from a 100 -year snowmelt in about 100 days. • The cost for this project is $5 to $7 million plus excess capacity usage fees. • This project would need to be constructed by 2005. Option 4 — Oversize MCES system so the City of Rosemount would always have a capacity of 167 cfs reserved for it within the system. It is also anticipated that, in the short-ten an additional 38 cfs would also be available as excess capacity until such a time as the area develops and the treatment plant is upgraded to discharge to its anticipated peak capacity. Details regarding this alternative are provided below: • Project would be constructed by MCES. Outlet will have capacity of 40 cfs at Bloomfield 5 th Addition. C.-Documents and Settings) jjlLocal SettingslTeniporaty Internet FilesIOLKIl080503- memo- ab.doc Rosemount Utility Commission August 6, 2003 Page 4 of 4 • Outlet will have capacity of 125 - 160 cfs at Trunk Highway 52. • Outlet will have capacity of 167 - 210 cfs at Mississippi River. • This outlet will reduce flood storage required in the City by 4,000 acre -feet and reduce funding costs by $5.3 to $32 million compared to other options. • This alternative will allow water to drawdown from a 100 -year snowmelt in about 45 days. • The cost for this project is $20 million. • This project would need to be constructed in 2005 (year). Recommendation Based on a review of the above alternatives and the observations made as a result of this analysis, we would recommend that Option 3 be selected provided a suitable agreement can be worked out with MCES. Justification for this selection is based on the following observations: Outlet would be available to accommodate City's needs in the short-term, as well as possibly address longer -term needs if infiltration practices prove to be a long -tern effective measure to reduce downstream discharge rates and /or if Flint Hills Resources has a use for our water. 2. If future capacity is not adequate, a system to serve only the east side of Rosemount could be constructed at a cost that is not greater than the cost for the original City system. If you have any questions concerning this information, please do not hesitate to contact me at 763 - 287 -7188. C: (Documents and Settings) jjlLocal Settings ITemporary Internet FilesIOLKl1080503- memo- ab.doc WSB & Associates, Inc. 4150 Olson Memorial Highway, #300 Minneapolis, MN 55422 (763) 541 -4800 (763) 541 -1700 (fax) Memorandum Rosemount Utility Commission Pete Willenbring, P.E. WSB & Associates, Inc. Charlie LeFevere City of Rosemount Attorney Date: Re: August 6, 2003 Approach /Strategy for Obtaining Acceptance or Approval from the Vermillion River Watershed for the Rosemount Comprehensive Storm Water Management Plan WSB Project No. 1005 -55 As you may be aware, the City of Rosemount has been engaged in discussions with the Vermillion River Watershed Organization to obtain approval of the City's Comprehensive Storm Water Management Plan. Although many of the issues that have been brought forward by the Watershed Management Organization (WMO) have been addressed, it has proved difficult to get a formal approval action from the WMO; in large part because they are a new organization that has new managers and staff, and has not yet developed a clear prospective of their mission. Because of these limitations, it appears they are also very uncomfortable accepting the City of Rosemount's suggestion that the City be removed from the Watershed Management Organization. In light of these considerations, outlined below please find a list of options we have available that could be used to deal with outstanding issues and /or obtain acceptance or approval of the Rosemount Comprehensive Storm Water Management Plan (Plan) from the Vennillion River Watershed. Available Options /Strategies Option 1 — Cease undertaking any formal activities to secure approval for the City of Rosemount Storm Water Management Plan and simply implement the Plan as it is currently developed. Discussion: ■ Failure to obtain approval could result in the City not being able to secure grant funding from Met Council for selected activities. Implementing the Plan, which is different than the currently approval Bonestroo Plan, could create unforeseen questions or problems should property owners C: (Documents and SettingslljjlLocal Settingsl Temporary Internet FilesIOLK11080503- memo- cl.doc Rosemount Utility Commission August 6, 2003 Page 2 of 5 impacted by the implementation of our current Plan wish to oppose its implementation. Failure to obtain formal approval from the Vermillion River Watershed may allow MCES to ignore the City's request to accommodate storm water into their effluent outfall pipe. Option 2 — Send a letter to Vermillion River Watershed indicating the City's intentions to implement the Plan without asking for any formal approval or acceptance of the Plan. The City could then implement the Plan as needed. Discussion: ■ This alternative allows the City of Rosemount to provide a statement and justification for their actions relating to the implementation of the Plan but would request little, if any, approval of the Plan from the Watershed. ■ This approach would put the ball in the Watershed's court to either do nothing or provide some acceptance of the Plan. ■ Based on a review by Charlie LeFevere, this approach of sending a letter telling them what you are going to do but not ask for their approval, will likely not provide a legally defensible position, but does provide an above -board justification for our actions. Option 3 — Submit a letter to the watershed asking them for acceptance or approval of the Plan with the understanding that the City will update their Plan to be consistent with the updated Vermillion River Plan when it has been prepared and is complete. This option also would require the City to delete all references that it intends to remove the City from the WMO. It is anticipated the City would work with the County during the preparation of the Watershed Plan to address the issue of whether or not the City should be removed from the Vermillion River Watershed Organization. Discussion: ■ This option includes considerations that would snake this alternative more acceptable to the Vermillion River Watershed because they could address the boundary issue as part of their future planning process while still allowing the City to obtain approval of their Plan. This option would require the City to remain in the Vermillion River Watershed and have its residents pay toward the organization's operating expenses for a longer period of time. ■ A potential option that could be considered in the Vermillion River Watershed Plan would be to include Rosemount within the Organization, but either return the money that the City contributes to the Organization back to the City in an effort to fund the projects within the City, or to develop a different levy structure for areas C: (Documents and Settings) jjlLocal SettingslTemporary Internet FilesDLKI1030503- memo- cl.doc Rosemount Utility Commission August 6, 2003 Page 3 of 5 within the City of Rosemount that would be different than those draining to the Vermillion River. Since the law requires each City within the Seven County Metro Area to be part of a Watershed Management Organization, and the City has not yet developed a framework organization to allow this to occur, allowing the Vermillion River Watershed to review these issues as part of their plan development, as well as their need to properly define and update the hydrologic boundary for the watershed may have some benefit to the City. Option 4 — Continue to actively pursue with the Watershed staff and managers to immediately secure approval of the City's Plan and withdrawal of the City from the Vermillion River Watershed District and its taxing authority. Discussion: This alternative would likely require the City to actively pursue a boundary change for the Vermillion River Watershed, likely require the City to develop its own Watershed Management Organization (perhaps with the City's of Eagan and /or Apple Valley), and likely create some friction between the Watershed and the City, as at this time it does not appear the Watershed is prepared to make a decision regarding watershed boundaries or its tax base. History The City of Rosemount had a 1998 Comprehensive Storm Water Management Plan approved by the Vermillion River Watershed. The City updated this approved Plan to meet current storm water management issues and submitted it on July 8, 2002 to the Met Council and the Vermillion River Watershed as required in Mimzesota Rules 8410. This updated Plan was also submitted to the US Fish and Wildlife Service, DNR, BWSR, MPCA, SWCD, and the adjoining communities. The updates to the approved 1998 Plan generally related to the following: ➢ Revising the drainage system design to direct storm water to the Mississippi River rather than the Vermillion River ➢ Creating a WMO in the absence of the disbanded Vermillion River WMO ➢ Updating the City's storm water management policies to limit discharge rates from newly developing areas, require pretreatment to NURP standards prior to discharge to infiltration areas or wetlands, require storage of the 100 -year, 24 -hour event, and require infiltration for 1/12 of an acre - foot /acre /day from developing sites ➢ Identifying problem areas and corrective actions ➢ Developing an implementation plan These updates were made to be fully consistent with the old Vennillion River Watershed's Plan and generally have made the City's Plan more restrictive than the Watershed's Plan. C )Documents and Settings) jjlLocal Settings7emporary Aternet FilesDLKI 080503- memo- cl.doc Rosemount Utility Commission August 6, 2003 Page 4 of S The City of Rosemount developed their updated Comprehensive Storm Water Management Plan to meet the standards and objectives of the Vermillion River Watershed Plan that is currently in place. It is further noted that the Rosemount Storm Water Management Plan that was being updated was approved by the Vermillion River Watershed Organization in 1998, and the City of Rosemount's Plan has simply been updated to reflect more rigorous standards for rate control, treatment, infiltration, and reducing anticipated future discharges to the Vermillion River as was the objective of the organization's Plan at that time. The City believes that the updated Plan is in conformance with the goals and objectives of the old Vermillion River Watershed Plan. ■ On September 6, 2002 a letter was received from Dakota County /Vermillion River Watershed indicating the Plan was not approved. The justification for non - approval was outlined in a letter dated September 13, 2002. ■ On December 12, 2002, a draft memo was sent on behalf of the City of Rosemount categorically responding to comments that were received regarding the City's Storm Water Plan from the Met Council, Soil Water Conservation District, the City of Eagan, and Vermillion River Watershed Management Organization. This memo was used to further discuss the County's comments and come to conclusion on a number of their issues. ■ Based on the December 12 draft memo and subsequent meetings with the Vermillion River Watershed, a final memo was sent on July 1, 2003 on behalf of the City responding the to comments that were received regarding the City's Storm Water Plan. These final comments were based on previous meetings with the County to address their issues. Based on a letter dated July 18, 2003, it is understood the Vermillion River Watershed Management Organization has not completed the review of the City's July 1St memorandum. Since submitting the Plan on July 8, 2002, the City of Rosemount has needed to implement a number of significant storm water management projects in order to address storm water management needs within the City. The City is also under contract to implement a number of other projects that are outlined within the City of Rosemount's Comprehensive Storm Water Management Plan in the near future so that these systems can be constructed in a timely and cost - effective way as part of other construction taking place within the City. Since no active WMO Board was in -place from the July 2002 submittal to 2003 and the City needed to make decisions about storm water management within its borders during this time, these projects were designed based on the City's updated Plan ■ The City of Rosemount is working with MCES to upsize the Empire effluent outfall to the Mississippi River so the City can utilize this outfall to carry storm water runoff to the Mississippi River for areas within the community. An immediate decision is being C.IDocuments and SettingsV #VLocal Settings I Temporary Internet FilesDLKIW80503- memo- cl.doc Rosemount Utility Commission August 6, 2003 Page 5 of 5 requested by MCES regarding the City utilizing this outfall to the River, as well as the City committing to an expenditure of approximately $5 million to accommodate the increased costs for oversizing the system to accommodate the storm water runoff. ■ Based on conversations with the Watershed managers at their July 24, 2002 meeting, it is understood that they may not be comfortable and/or may not be able to approve the City of Rosemount's Storm Water Plan until the updated Vermillion River Watershed Plan is completed, a task that will likely not be complete until one to two years from now, or possibly longer. Recommendation Based on the above considerations, as well as input received from the Vermillion River Watershed Managers and staff, it is recommended that the City of Rosemount propose that the Vermillion River Watershed Management Organization approve Rosemount's Comprehensive Stonn Water Management Plan based on the following changes and with the following understanding: This approval is based on a review of the Rosemount Storm Water Management Plan being in substantial conformance with the previously developed Venmillion River Watershed Plan. 2. The City of Rosemount will make modifications to its proposed plan to remove any discussion or intention that the City of Rosemount will withdraw from the Vermillion River Watershed Management Organization. The City of Rosemount will update their plan to be consistent with the future Vermillion River Watershed Plan in conformance with the schedules outlined in Minnesota Statutes Chapter 103B.235. This approach will allow the Vermillion Watershed Management Organization to become used to and/or incorporate suitable boundary changes to reflect Rosemount's drainage patterns as part of their updated storm water plan. It is anticipated the City of Rosemount will be working closely with the Vermillion River Watershed to make certain that they thoroughly review and consider the City of Rosemount's position to be removed from the Vermillion River Watershed District unless other considerations prove it to be in the best interest of both parties for the City of Rosemount to remain within the District. Some considerations that may be worth discussing include utilizing the organization to undertake various NPDES implementation activities for the City of Rosemount including education, water quality monitoring, funding the City's improvements needed to divert water from the Vennillion River to the Mississippi River, etc. If you have any questions, please feel free to call me at (763)287 -7188. C: (Documents and Settings lljjlocal Settings l Temporary Internet FilesIOLK/ 1080503- nnemo- cl.doe