2010-08-25 CC Packet - Laserfiche WebLink

Home Browse Search

EXHIBIT A Memorandum iL Bonestroo To: ANOKA COUNTY Project: DOWNTOWN 2335 Highway 36W PARK BOARD REDEVELOPMENT Date: 10.15.09 sc Paul, MN 55113 Tel 651- 636 -4600 From: MARK STATZ, PE Client: CITY OF CENTERVILLE Fax 651-636-1311 www.bonestroo.com Re: STORM WATER RECLAMATION File No: 616 -08167 BACKGROUND The City of Centerville has, for some time, been planning a redevelopment of their downtown. A major part of this planning effort has revolved around storm water treatment. In the past, storm water practices addressed water quality and the control of discharge rates from the site. Recent changes to the watershed district rules require not only rate and quality control, but also volume control. This new wrinkle can be quite costly, and more importantly to a downtown project, can consume valuable acreage. Therefore, the City is looking to innovative methods of meeting these requirements rather than traditional solutions such as rain gardens or pervious pavements. Specifically, we are exploring the idea of utilizing storm water runoff as irrigation water. The runoff would be stored in a traditional storm pond and then pumped out of the pond and onto a ballfield or other area in need of irrigation. After evaluating several sites, we've determined that the storm pond, built by Rice Creek Watershed District, in the Rice Creek Chain of Lakes Regional Park Reserve near the southeast corner of the park is best suited for our needs. PLANNED IMPROVEMENTS The infrastructure necessary to complete this project consists of a large concrete storm pipe coming from the downtown area and discharging into the ditch running westerly along the south side of the City's LaMotte Park. At the pond site, a pumping facility and forcemain leading back to the LaMotte Park ballfields would be installed (see attached figure). Slight modifications to the pond's outlets would be needed, but NO changes to the existing footprint of the pond would be necessary. IMPACTS TO THE PARK Impacts to the regional park would be minimal. Again, no modifications to the pond's footprint would be made. The pond's outlet would be lowered slightly to manage its high water level. During construction, there would be temporary disturbance to the north border of the site for installation of the pipe leading to the ballfields and for construction of the pumping facility. We are hoping to be able to have a pump system which is confined to an underground vault, so there will be no need to have a pumphouse style structure near the pond. HOW IT WORKS Your existing pond is about six feet deep. When a storm event occurs, the normal water level "bounces" up about 3 feet and then slowly drains out. This retention time, allows sediment and HLV