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extended detention is typically only needed for relatively small frequency storms, these devices typically do not significantly increase the 100-year flood level. In most cases, the increase of the I00-year flood level is a few inches. As such, the costs to acquire easements are not extensive because the added easement area (if any) needed to accommodate a small increase in the I00-year flood level is typically not large. Most often we have found the increase to be within the existing pond easement. The opinions of cost for extended detention structure improvements listed in Table l do not include the cost of acquiring additional land for increased minor flooding, completing the hydrologic and hydraulic analyses, or engineering design. But they do include cast for subsurface explorationlgeotechnical analyses, and construction including foundation support. See Section 4.4 for additional details on extended detention structures. 3.5 Assessment of Need for Sediment Removal Silver View Pond was assessed for its need to have accumulated sediment removed to maintain its functionality as a water quality basin and return it to its originally constructed configuration. Due to the basin's large storage capacity and continued high pollutant removal efficiencies, Silver Vieux Pond does not require immediate sediment removal. However, since the volume of accumulated sediment in 'Silver View Pond is significant. nearly 40% of the original design volume is occupied by sediment, sediment removal should be planned for in the near future assuming such construction is within city budget. When sediment removal is performed, a watershed analysis should also be performed to identify potential sources of past and future sedimentation. Ways to minimize future sedimentation should be included in the design of the pond clean -out. Silver Vieux Pond was given an over-all moderate priority rating for major pond improvements. However. there are multiple areas of the pond which should receive maintenance more immediately. Provided an extended detention structure does not adversely impact neighboring properties, it is advisable to modify the outlel structure to prevent short-circuiting and improve water quality treatment efficiencies. Additional housekeeping maintenance needs for Silver View Pond were identified such as inlet scour, riprap deterioration, and pipe degradation. Individual maintenance items have varying impacts on infrastructure protection, water quality treatment, and flood mitigation aspects of the pond and should be prioritized by the city based on the severity of the impacts and the feasibility of the maintenance or minor modifications. A preliminary prioritization of the additional maintenance needs for the basin is found in Section 4.2. P Nlpi+?; MN Iti'_'-M_?1 1Q SiI%cr View 1'md Asnssmenl Workriles Itcport SiI%rr View Popid .A. r .onrirl-I ill aIdoc\ 17