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greatly increase the cost of the pond improvements. Therefore, we do not recommend expanding the pond beyond its original contours. Converting the pond to an extended detention basin by a simple outlet modification would not likely pose any significant permitting issues. See Section 4.4 for further discussion about extended detention basins. The MPCA has the authority to issue permits for the management of dredged materials under the National Pollutant Discharge Elimination System (NPDES) and/or the State Disposal System (SDS) permitting programs. In December 2011, the MPCA released its most recent version of "Managing Dredged Materials in the State of Minnesota." which includes specific guidance for projects involving sediment removal from municipal or urban stormwater systems. Based on this guidance, the MPCA does not require a permit or reporting of results for small maintenance projects (i.e., when project maintenance activity is less than 3,000 cubic yards (CY) of excavation and chemical sample data indicate that the dredge material meets sediment disposal category SRV I). The MPCA stresses the importance of determining, if the sediment presents a potential adverse impact to human health or the environment and indicates that proper risk evaluation, sampling protocol, and site consideration for where the sediment will be reused or disposed is necessary. The accumulated sediment volume in the pond was computed to be 45,335 CY. Since the excavation at Silver View Pond will exceed 3,000 CY, the MPCA will require that a Construction Stormwater Permit Application. Stormwater Facility Dredge Project Supplement form, and a sediment sampling plan be submitted for review. 4.4 Structure Modifications Typically water quality treatment basins have been designed with outlet structures that enable flows that reach the outlet to exit the basin quickly. And, typically, water duality treatment basins with ample dead storage volume and minimal potential for short-circuiting do a good job removing sediments and phosphorus. However there are instances when a typical open -water pond with sufficient dead storage cannot or should not be built and/or when short-circuiting decreases the basin's potential to treat runoff. Such instances include, but are not limited to: 1. Where basin construction may he too costly due to the presence of bedrock 2. When basins are sited within a mile of an airport 3. When an outlet structure needs to be constructed near a basin inlet structure 4. When [lie basin is located in a historic wetland P A1pis :3 KIN Q 21e2II 81- Sku Virs Pond Assessnrcni Workriles Report Silva Vic% Pnn.l Assesmtient-hndkiriex ? I