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September 24, 2013 <br />Mr. Leonard Linton, PE <br />City of Ramsey <br />7550 Sunwood Drive NW <br />Ramsey, MN 55303 <br />l lintonaa?,ci.ramscy.mn.us <br />LOUCKS <br />/200 Hemlock Lane <br />Suite 300 <br />Maple Grove, MN 1,5369 <br />763.424.5505 Itra0 <br />763.424.5822 t;rx <br />loucksassociares.cOnt <br />Re: Flood Elevation — Lot 4, Slack 1, VALLEY VIEW ACRES - Ramsey, MN <br />Proposed Plat of DIEHL'S ACRES <br />Dear Mr. Linton: <br />As part of the project approval for DIEHL'S ACRES the City has requested a determination of the 100 <br />year flood elevation of County Ditch No. 14. <br />The enclosed copy of the flood map from FEMA shows that the flood elevation is not established in this <br />area but is established just to the east of the site at Vanadium Street. The flood elevation at Vanadium <br />Street is 877. <br />As we discussed earlier, and with our discussion with the County Highway Department, there has not <br />been a significant flooding issue in this area in the past. The existing ditch section and the existing <br />culverts have been adequate to contain the runoff during previous flooding events. <br />The method we used to project the flood elevation to the site is a straight forward analysis of the ditch <br />slope. Starting at the flood elevation of 877 at Vanadium Street, we projected the average ditch slope <br />upstream into the site. The plan shows the flood elevations through the site. <br />We also analyzed the capacity of the ditch in relation to the upstream culvert capacity. The upstream <br />culvert is a 42" culvert under 185111 Ave. NW near Ebony Street, approximately 1.0 mile to the northwest. <br />This culvert, with its size and slope has a capacity of approximately 150 cubic feet per second (cfs). The <br />cross -sectional area of the ditch at station 17+00 provides approximately 155 cfs at a depth of 3.7 feet, or <br />at an elevation of 880.5, See enclosed calculations. At the flood elevation of 883.0 the ditch provides <br />585 cfs of capacity. Therefore, the ditch has adequate capacity to contain additional flow from a flood <br />event. <br />If you have any further questions or comments please feel free to give me a call. <br />Sincerely, <br />LOUCKS ASSOCIATES <br />--T q <br />Todd W. McLouth, PE <br />Senior Project Engineer <br />Cc: Richard Krier, Midwest Planning <br />File: 013326.OA <br />planning - civil engineering - land iurveying • land ,cai>e architecture • environmental <br />