Agenda - Council - 05/09/2006 - Laserfiche WebLink

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Action: Ratify ~e recommendofiott~ of tile Public Works. Committee. Case #6 Consider Alternatives to Address Ermine Boulevard Floodplain Issue Background: City Engineer Jankowsld stated last spring the City was made aware of a possible violation of floodplain regulations at 9421 Ermine Boulevard NV/'. A May 12, 2005 letter fi.om Mr. David Scheim of FEMA resulted from an investigation of a request by Mr. Joel Bums, the property owner of 9421 Ermine Boulevard NW for a letter of Map Revision in November 2003. This issue was presented to the Public Works Committee at the July 19, 2005 meeting resulting in the authorization of a proposal from the Polaris Group to verify the accuracy of the floodplain maps and to address possible solutions to this issue. Polaris has completed their work and has prepared a report, which summarizes the issue and offers a number of alternatives for providing resolution of this situation. The following alternatives were reviewed for consideration: · Alternative 1 Move Structure- Cost $90,000 to $130,000 The house and the accessory structures could be moved out of the floodway and onto an adjacent lot owned by the City immediately to the west. · Alternative 2 Property Buyout - Cost $115,000 The house would be purchased under a 50% cost share program available through the MnDNR and the house and foundation would be removed. The funding for the DNR share of this alternative is not guaranteed and there will be competition for funding. · :. Alternative 3 Regrade Ermine Street west of Property - Cost $55,000 This would allow the floodway to spill over the road as it currently does, but in a location further to the west that would allow the violating property to be outside the revised floodway. · Alternative 4 Install Twin Box Culverts - Cost $120,000 to $160,000 The existing 72 inch culvert would be replaced with two 60 foot long 10 x 7 box culverts that would allow the floodway to be revised so that the entire 100 year flood would be carded through the culvert and would no longer overtop Ermine Boulevard. In addition this alternative may require the acquisition of easements if the installation of the twin culverts cannot be confined within the OHW of Trott Brook. · Alternative 5 Combination of Culvert Replacement & Ermine Street Regrading- Cost $90,000 to $100,000 This alternative is a combination of Alternative 3 & 4. It calls for the replacement of the existing 72 inch culvert with a single 12 x 7 foot box culvert and a less extensive need to regrade Ermine Boulevard. However, this alternative would not provide enough culvert capacity to prevent the overtopping of Ermine Boulevard during the 100 year flood event. Two other elements should be considered in recommending the preferred altemative. Alternatives'4 '& 5 wou~fl both replace'the 'existing 72 'inch concrete culvert, which has open joints that are permitting soil loss fi.om the base of the road and shoulder areas. A second consideration is that alternative 4 would remove the 100 year flood from overtopping Ermine -277-