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Item No: 7G Meeting Date: October 10, 2011 Type of Business: Council Business Administrator Review: ____ City of Mounds View Staff Report To: Honorable Mayor and City Council From: Nick DeBar, Public Works Director Item Title/Subject: Resolution 7838, Authorizing Barr Engineering Company to Perform a Sediment Survey and Prepare an Evaluation Report for Silver View Pond Background: As a requirement of the Storm Water Pollution Prevention Program (SWPPP), Public Works is responsible to operate and maintain the various components that make up the City’s stormwater system. The SWPPP is a requirement of the Municipal Separate Storm Sewer System (MS4) general permit. This permit is mandated by the federal regulations under the Clean Water Act and administered by the Minnesota Pollution Control Agency (MPCA). The MS4 permitting program gives owners or operators of municipal separate storm sewer systems approval to discharge stormwater to lakes, rivers, and wetlands in Minnesota. Discussion: Silver View Pond was created by excavation in 1982 to provide stormwater storage for developments proposed within its 146-acre drainage area. The pond is approximately 9.3 acres in surface area and is located in Silver View Park. The pond was designed and constructed with three distinct arms (or basins) with narrow connections between each to slow the movement of sediment and nutrients toward the outlet (located near Long Lake Road). The permanent pool in the pond provides water quality treatment, while the storage ability above this permanent pool elevation provides rate control for flood protection. The MPCA recommends that stormwater ponds like Silver View Pond be evaluated for sediment removal when the permanent pool volume is reduced to 50% by sediment storage. The timeframe for sediment to build up to this level varies depending on many factors, but a rule of thumb is roughly 30 years. Excess sediment in the pond can decrease its ability to treat stormwater runoff to acceptable water quality levels. There has only been one known study of Silver View Pond. In response to neighborhood and City concerns, the City commissioned the development and preparation of a management plan around 1989. This plan focused on four objectives: 1) improved water quality, 2) wildlife habitat enhancement; 3) creation of a viable fishery; and 4) improved aesthetics. At that time, the pond was functioning properly. City staff solicited an engineering proposal from Barr Engineering Company to provide the necessary tasks to determine the current and future performance of Silver View Pond. The scope of work includes data gathering (sediment survey), basin maintenance computations and prioritization, and preparation of a basin maintenance summary report. Barr’s fee for this work is on a time and material basis not to exceed $9,950. A copy of their proposal is attached. The 2011 adopted Budget includes $10,000 under the stormwater enterprise fund (245-4415- 3030) for this work. Recommendation: City staff recommends that the City Council consider adopting the attached resolution authorizing Barr Engineering Company to perform a sediment survey and prepare an evaluation report for