2009-11-04 P & R Packet - Laserfiche WebLink

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Stain, Marc R From: Neprash, Randy D Sent: Friday, October 10, 2008 9:59 AM To: 'dlarsonOcentervillemn.com'; Statz, Mark R Cc: 'Meyer, John - Centerville'; Evans, Earth A Subject: Irrigation from stormwater ponds - pollutants Good moming, Dallas: I just got off the phone with Bruce Wilson, from the MPCA. Bruce runs their research work and Is one of the most capable people at the agency. The response from Bruce is not official, but I am confident of his opinion. Bruce said that the current pollution concerns (PAHs and others) are all related to particulate materials. The pollutants adsorb to solid particles. This means that they settle in ponds and reach concentrations of concern in the sediment. The system you are discussing In Centerville runs through two ponds before it is pumped out to the irrigation system. There should be ample time for settling. Bruce recommended that the pump intake be a floating device that pulls water from close to the pond surface. This would avoid picking up the settled materials and water near the bottom that may anoxic. Bruce's other recommendations included: • Make sure there are no stormwater " hotspots" in the drainage area. Hotspots are land uses and businesses that are widely recognized to be pollutant sources. The MN Stormwater Manual provides information on identifying hotspots. • Make sure there are provisions to shut down the pumping system in the event of a fuel or hazardous material spill anywhere near the drainage area. With these provisions, Bruce saw no reason to hesitate with moving ahead with the project. He thought It was a great approach to achieving volume reduction. I hope this is helpful. Thanks, Randy Neprash, PE Tel 651- 6044703 raky.neprash4bonestroo.com Bonestroo 2335 Highway 36 W St. Paul, MN 55113 Tel 651- 6364600 Fax 651 -636 -1311 www.bonestroo.com