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Department Approval: REQUEST FOR COUNCIL ACTION DATE: 10/23/00 ITEM NO.: F-11 Manager Reviewed: Agenda Section: (��L,� Reports/Recommendations �'_�� Item Description: Storm Sewer Modifications --Wilson Pond Connection Background: In 1997, Roseville constructed a new regional stormwater pond to serve the west side of the Twin Lakes redevelopment area. This new pond was constructed immediately north of the e�sting Mn/Dot Wetland adjacent to I35W and north of County Road C. The new regional pond provides for the future stormwater treatment needs of the redevelopment properties that drain to it. For many years the existing Mn/Dot pond has overtopped during larger rain events and flooded a portion of Cleveland Avenue. A 10 year frequency rain event typically floods up to 1 foot on Cleveland Avenue. A 100 year storm could flood up to a depth of 4 feet. When this area was used primarily for trucking, the occasional flooding of Cleveland Avenue, while a nuisance, was tolerable. As the area redevelops to office and other higher uses, the flooding of Cleveland Avenue is no longer acceptable. Concern has been raised by Ryan Construction Company, the developer of the new Veritas headquarters. The Twin Lakes stormwater system has been reviewed to identify ways to reduce the flood elevation of the Mn/DOT Wetland and subsequently, the flooding of Cleveland Avenue. Two projects have been identified that will significantly reduce the high water level of the wetland. Wilson Pond Connection. This project includes the installation of a new 24 inch storm sewer on the east side of Cleveland Avenue that will provide an overflow from the Mn/DOT wetland to Wilson Pond. Wilson Pond is an existing pond east of Cleveland Avenue and north of County Road C-2. This improvement will lower both the flood elevation of the Mn/DOT Wetland and duration of flooding events without adversely effecting properties adj acent to Wilson Pond. It was the most effective measure analyzed and can be constructed immediately. It is estimated to cost appro�mately $80,000. 2. County Road C/I35W Ramp Ponds. This project involves the construction of new ponds and additional stormwater storage in the inside of both the east and west e�t ramps at County Road C. This project would improve both flood storage and stormwater treatment. The most appropriate time to construct this improvement would be with Ramsey County's proposed reconstruction of County Road C in 2002. The cost of this improvement is appro�mately $250,000. Staff is recommending that both improvements be constructed - the Wilson Pond Connection in the fall of 2000 and the County Road CII35W Ramp Ponds as part of the County Road C reconstruction in 2002. When the new Twin Lakes Regional Pond was originally designed, the e�sting high water elevation of the Mn/DOT wetland was not properly identified. Had the correct information been used, the proposed pipe connection to Wilson Pond would have been constructed in 1997 as part of the pond construction project. The purpose of this Request for Council Action is to gain permission and funding to construct the Wilson Pond Connection project.