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~ ~ EN HILLS e MEMORANDUM DATE: June 19, 2006 AGENDA ITEM 2.E FROM: Mayor and City Council Kri. G- C' 'I E' V (\ Ill' ) stme Iga, IVl ngmeer r-l? ,fY\,V TO: SUBJECT; 2006 PMP Update (Rain Garden Maintenance) BACKGROUND . Rain gardens havc becn includcd as a part of the storm water improvements to the 2006 PMP Ridgewood Neighborhood project. Since the neighborhood is fully developed and also limited due to rolling topography, we were unable to size the proposed stonn water ponds to traditional National Urban Runoff Program (NlJRP) standards for treatment of the storn1 water that flows through them. URS has worked with Rice Creek Watershcd District (RCWD) to provide additional storm water treatment using other design features, including the proposed rain gardens. DISCUSSION There has been a strong interest expressed by residents and thc RCWD to include upstream infiltration by the use of infiltration rain gardens. The current design has identified 15 locations where residents have agreed to rain gardens, which would benefit the function and effectiveness of the ponds and sewer network. The use of rain gardens does not eliminate the need for a storm sewer system, but will aid in improving the water quality. . Rain gardens are areas where storm water is captured and allowed to infiltrate illto the ground. They are shallow (<32", usually <8" for residential) depressions, typically planted with water absorbing native plants, strategically located to collect, infiltrate, and filtrate rain that falls on hard surfaces like roofs, driveways, alleys, or streets to minimize negativc impacts of excessive runoff from these surfaces on lakes and streams. The rain gardens would be constructed to overflow back into thc strect, to prevent yards and homes from flooding. \\metro-inet\ardenhills\PR&PW\Operations & Maintenance\Pavement Management Program {PMP)\20OU PMP Rrdgewood Neighborhood\6-T9- 06 2006- PMP Update-Gardc!ls.doc