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AR—DEN HILLS CITY COUNCIL—May 26, 2009 7 Civil Engineer Giga stated that the Staff would have increased the size of the rain garden in the City right-of-way or talk to those residents that had not attended the meetings about possibly having a rain garden. City Engineer Bloom stated that if there had not been enough interest in the rain gardens then other alternatives would have been explored. She explained that a rain garden was a shallow depression behind the curb that is planted with native vegetation that allows rainwater runoff the opportunity to be absorbed into the soil. Councilmember Holmes asked how big the rain gardens were. City Engineer Bloom stated that this would depend on the volume of water directed at it. Councilmember Holmes asked for the average size. Civil Engineer Giga stated that the average size was about 200 square feet. Councilmember Holmes asked if these were located right next to the street. Civil Engineer Giga stated that there is a three foot buffer between the curb and the rain garden. This buffer helps to protect the rain garden during the winter from the sand and salt. Councilmember Holmes asked what would be considered native vegetation. Civil Engineer Giga stated that native vegetation would be either grasses or flowers that have a deep root system that would allow them to maintain their water supply when there is little or no rain. City Engineer Bloom stated that rain gardens cost about $1800.00 for an average 200 square foot garden. The City looks for volunteers for these gardens because it offers the City an opportunity to partner with the residents and it is also a less expensive alternative for the City to provide infiltration and bio-filtration. Other options to provide infiltration and bio-filtration would be to purchase land to build a pond, to put a pipe underground or a bio-filtration trench. Anytime the sub-grade is worked on then Rice Creek Watershed requires infiltration and bio-filtration methods to be in place in order to acquire a permit. The Maintenance agreement is also a requirement in order to acquire the permit. Councilmember Holmes asked if the property owners would be required to sign something stating that they would be responsible for these rain gardens.