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FROM A3NBERG 8: ASSOCIATES FAX NO. : 952 473 4435 Nov. 21 2003 02:41PM P2 <br /> GRONBERG &ASSOCIATES, JNC. <br /> SURVEYING, ENGINEERING AND LAND PLANNING <br /> 445 N, WILLOW DRIVE <br /> LONG LAKE, MINNESOTA 55356 <br /> 952-473-4141 <br /> FAx: 952-473-4435 <br /> r <br /> November 21, 2003 <br /> Thomas Deveau <br /> Proposed Culvert Summary <br /> The drainage calculations we did on August 7,2003 show that Area 1,the south swale, <br /> has a runoff of 1 CFS for the one year storm, 3 CFS for the ten year storm and 6 CFS for <br /> the 100 year storm. <br /> To handle the 3 CFS for a ten year design, the culvert should be a smooth walled pipe <br /> such as HDPE and have a slope of at least 0.6% for a 12 inch diameter pipe. We have <br /> shown a proposed 42 foot long 12 inch HDPE pipe at 2.0%. Riprap should be placed at <br /> the downstream end. <br /> Sincerely, <br /> Gr,onbergg&DAssociates <br /> Marr S. Gronberg, P.E. &L.S. <br />