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Zoning Application #1704 <br />January 15, 1992 <br />Page 2 <br />advised that prior to the construction of the new residence <br />currently owned by Mr. Madge, there appeared to be erosion <br />problems but they were minor based on the gentler slopes adjacent <br />to the immediate spillway from the road. With the construction <br />of the residence, major changes were made in the area of the <br />drainageway resulting in severe erosion whenever it rained. Both <br />owners report the velocity of run-off is intense during an <br />average to major rainfall. <br />Mr. Madge contacted the City seeking assistance in an <br />attempt to resolve the erosion problems and was advised that if <br />the Ci^ y was to make any improvements to the drainage swale that <br />it weald involve a storm sewer improvement project. Mr. Madge <br />was then advised that he could make the necessary drainage <br />Improvements as long as they met the City's standards. <br />Mr. Madge proceeded with a riprapping project Involving <br />filter fabric and large rocks that were soon washed down into the <br />channel after the first few heavy storms of last year. Mr. <br />Madge's contractor returned to try again and now installed riprap <br />with grout that extended approximately 100' from the culvert on <br />the west side of Forest Arms Lane. This facility appears to be <br />withstanding the heavy velocities of run-off. Unfortunately, <br />this was not a method approved nor recommended by the City staff. <br />The Zoning staff met with Mr. Madge and he advised that he wanted <br />to proceed with the comprehensive improvement oi the channel area <br />because erosion was still playing havoc with the remainder of the <br />drainageway. Mr. Madge has filed a comprehensive application <br />with his immediate neighbor, Mr. Carlson, that will involve the <br />complete improvement of the drainageway. The current plan <br />requests that the current riprap grout area be allowed to remain <br />and that the remainder of the channel be altered to an 8' width <br />at a 2' depth with riprap and filter fabric to be placed along <br />the center portion carrying the majority of run-off. Review <br />Glenn Ccok's report. Exhibit G, for his review comments and <br />recommendation. Cook recommends the following: <br />1.Channel or drainageway should be constructed with Class <br />2 riprap (MnDot 3601) and filter fabric. <br />2.Work shall be completed in accordance with MnDot's <br />Specification 2511. <br />3.Riprap shall not be grouted because of the potential <br />for movement and Increase in hardcover within the <br />lakeshore protected area. <br />.ft' <br />4.Silt fence will be required between the lakeshore and <br />construction area until vegetation is re-established.