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2.0 Background and Assessment Methodology 2.1 Background The City of Mounds View (city) is essentially a fully developed municipality that uses stormwater detention ponds for flood control and water quality treatment. In 2011 the city started its stormwater pond assessment program in accordance with its MS4 permit with Silver View Pond (see Figure 1). Silver View Pond's current configuration was created by excavation in 1982. Though likely excavated partly for aesthetic concerns, the pond's three distinct arms serve to slow the movement of storm flows allowing sediment and nutrients to be removed before flows leave the pond. A management plan for Silver View Pond was developed around 1989. The management plan addressed four objectives for the pond; improved water quality, wildlife habitat enhancement, creation of a viable fishery, and improved aesthetics. The management plan included several recommendations: • Pre-treatment of stormwater runoff from new developments • Enacting an ordinance to limit the use of phosphorus containing fertilizers • Performing limited harvesting of aquatic macrophytes in specific areas of the pond • Reducing mowing in several areas adjacent to the pond to improve upland wildlife habitats • Converting some areas adjacent to upland nest cover plantings • Adding, additional nesting structures near the pond • Monitor the use of the pond by Canadian geese and prevent nesting • Monitor beaver activity in and around the pond and prevent colonization At this time it is unknown if the city completed or is continuing to follow the recommendations made in the 1989 management plan. Silver View Pond was selected for assessment in 2011 because there has been no sediment maintenance in the nearly 30 years since the pond was created, and it was felt that significant sediment accumulation in the pond was likely. The MPCA recommends that stormwater ponds be evaluated for sediment removal when the permanent pool volume is reduced to 50% by sediment accumulation. Without completing an assessment, it is difficult to know the amount of accumulated sediment in a pond: however, one rule of thumb indicates that accumulation of sediment to reduce the permanent pool volume by 50% occurs in roughly 30 years. The results of the 2012 assessment of P. Mpis 21 MN 6' 23h21092 Silver Vic* Pond Am ossinenI workh I e�.kepori silver View Pond.&a,vssmcnt•rina I. don 3