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ARDEN HILLS CITY COUNCIL—May 26, 2009 10 City Engineer Bloom stated that infiltration was required for the first one inch of rain water. Councilmember Grant stated that the National Urban Runoff Program required two inches. Civil Engineer Giga stated that the National Urban Runoff Program requirement is for ponds and infiltration requirements are different. Councilmember Grant asked what would happen in the event of a ten or fifty year rain event. Civil Engineer Giga stated that the first inch of rain is considered the first flush and everything else would bypass the gardens into the storm sewer system. The first flush is where most of the pollutants are and getting this into the rain gardens where the plants can take out the nutrients and filter the water is what the Rice Creek Watershed District is looking for. Councilmember Grant stated that along with the absorption of nutrients infiltration was also lowering the water temperature slowing algae growth. He asked if the rain garden Ms. Nelson referenced was located in the Ingerson Neighborhood. Civil Engineer Giga stated that Staff would look into this and report back to the Council. Councilmember Holmes asked how the City could be assured that the rain gardens would be properly spaced so that they would be effective. Civil Engineer Giga stated that the locations were selected based on the feasibility of rain collection. Councilmember Holmes asked Civil Engineer Giga if she thought the rain gardens were well spaced on the map. Civil Engineer Giga stated that Staff had gotten a list of those residents that were interested in having a rain garden and then went to look at the properly. Staff worked with the residents to pick the best location. The rain gardens are sized to support the amount of rain that they will get in the location selected.