2C, Storm Water Ponds Maintenance Program

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DATE: November 15, 2010 TO: Honorable Mayor and City Council Members Patrick Klaers, City Administrator FROM: Terry Maurer, Public Works Director Matt Woodruff, Civil Engineer SUBJECT: Storm Water Pond Maintenance Program Background A1WFI HILLS MEMORANDUM The City's storm water collection system contains numerous catch basins, manholes, sewer pipes, ditches, and ponds that receive runoff from rainfall events. Storm water runoff becomes polluted with sediments, road salts, metals, fertilizers, pesticides, and many other contaminants. Within Arden Hills, a portion of this runoff is directed to storm water ponds which treat and improve water quality by removing the pollutants before the runoff reaches a surface water body. A surface water body includes lakes, rivers, and streams. The City of Arden Hills has numerous ponds and wetland areas that receive storm water either through the storm sewer system or by overland runoff. Many of these ponds were either constructed as part of a neighborhood development or were an existing lowland /wetland area that had storm water runoff directed to them. In either case, the constructed ponds or existing wetlands have received storm water runoff (containing the pollutants previously discussed) for many years and it is important that they be considered for maintenance. Mainly, pond maintenance includes dredging of sediment deposits, as well as addressing erosion problems and cleaning out storm sewer pipes that enter /exit the ponds. In order for storm water ponds to be an effective means of water quality improvement, they must have adequate storage volumes such that sediments and other pollutants can settle -out from the storm water before reaching the surface waters. According to City records, the City's storm water ponds have not been dredged and have received little maintenance. In accordance with the City's Municipal Separate Storm Sewer System (MS4) permit with the Minnesota Pollution Control Agency (MPCA), the City is required to inspect 20 percent of the City's storm water ponds on an annual basis. MS4 permits are administered by the MPCA to regulate the amount of sediments and pollutants that enter surface waters through a City Council Meeting P:\Admin\Council\Agendas Packet Information\2010 \1 1 -15 -10 Worksession\Packet Information\2C 11- 15- lOMemo Pond- Maintenance.doc Page 1 of 3