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. Jesse Struve <br /> From: Jesse Struve <br /> Sent: Wednesday, September 18, 2013 3:27 PM <br /> To: Melanie Curtis <br /> Cc: Christine Mattson <br /> Subject: 20130918 3227 Casco Cir#13-00728 <br /> Melanie, <br /> I have reviewed the survey revisions and letter dated 9/17/13 and have the following questions: <br /> 1. What is the velocity of the water down the slope once it discharges the pipe? While the velocity at the end of <br /> the pipe may be 1 fps, there is potential the velocity down the slope may require additional slope reinforcement <br /> to prevent erosion down the slope. <br /> 2. What type of existing vegetation is on the slope downstream of the pipe outfall? The letter dated 9/17/13 <br /> states sod is sufficient to prevent erosion. Is this slope turf grass down to the lake? <br /> 3. The turf grass will generally have chemicals applied directly on it and will not provide adequate filtering of <br /> chemicals from reaching the lake. If the applicant does not want to install a rain garden for a 10 yr event, <br /> another possibility is to install a filtration basin with under drains instead of the proposed catch basin. They can <br /> direct the water to a low point and have turf grass, but instead of it dumping directly into a catch basin, it would <br /> be required to filter through a sand medium and into the under drains prior to entering the pipe to the lake. <br /> Jesse Struve, PE <br /> Director of Public Works/City Engineer <br /> City of Orono <br /> (952) 249-4661 - Direct <br /> (952) 249-4616- Fax <br /> www.ci.orono.mn.us <br /> 1 <br />