Storm water management assessment memorandum

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TECHNICAL MEMORANDUM HDR ENG/NEERING, INC. Comment Item D A periodic inspection schedule should be compiled and followed. Table 3 provides a suggested maintenance and inspection schedule. Table 3— Maintenance and Inspection Schedule Maintenance Item Description Frequency Remove accumulated trash and debris from the pond side Twice per year slopes, embankments, and inflow and outflow structures. Mosquito control As necessary Storm damage/ Site spill incident As necessary, especially after extreme weather events or uncontained material spill that may flow to the pond. Remove excessive vegetation growth that impedes access to As needed during the pond structures. growing season to maintain access. Perform visual inspection of pond inlet and outlet structure. Twice per year. Remove accumulated debris that may impede the inlet or outlet flows. Perform or schedule repairs as needed. Perform an annual inspection of the pond to make sure it is Annually operating as desired. It is recommended that a digital photo reference point should be established from which annual maintenance assessment can be made and the pond condition photo-documented. The pond should be drained and the following items should be checked: ❖ embankment subsidence ❖ cracking or excessive tree growth on the embankment ❖ damage to the outlet standpipe ❖ sediment accumulation at the outlet ❖ sediment accumulation around the inlet •3 inadequacy or failure of bank or other erosion controls ❖ changes to the pond configuration ❖ changes to the contributing watershed that may affect the pond Sediment removal 5-to 15-year cycle, 10 year interval recommended 11/4/2005 HDR PRO,IECT#32560 7 HENNEPIN COUNTY,MINNESOTA ORONO TRUCK STATION FACILITY STORM WATER POND EVALUATION