05-10-1993 Council Packet - Laserfiche WebLink

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I Bonestroo Rosene Anderlik & Associates Engineers & Architects A * ^ ' - 1 • • ^ i V ■ . •. ; V • • r - - . 4 • : -* • i \ . 4- i;- ■ ' • ■ i , ■ • m .• : . 4 ' • r . • . • 1 I J ^.4 4 *■ ■ > * r t ■ • A '■? *.V ■ 4,- • 4 , 4 V ' ^ ■ *. * C* ; 5 A . A A . - ; . * * , . f * :• * • \ i ” • M. V.’-f-; f''r » ■' - 4 y i- .. _ r i*.- - rv 4,' 4, ■ • *.* • » ^ ‘ t - . ■. V ! *■ . - -c ‘J ;■ •- *.* » . ^ t ^ ^ Pj ' i.* I *■• . . A = . . 4 :• • > t • ; 4 •’f I ^ . ' , , «-* : 'T .•.» . Jw ',.•<* ..W. ■'■ t • 4* , f rc , * F'-» .r -.'.'.r •. ■ «■' • V * « TiPR lI iSSo April 6, 1993 Ms. Jeanne A. Mabusth Building and Zoning Administrator City of Orono Post Office Box 66 Crystal Bay, Minnesota 55323 Re: Susan Sumey Shoreline Restoration File No. 139-1807 Dear Jeanne, . .r We have reviewed the proposed shoreline restoration proposal for Susan Sumey's property at 1330 Cherry '^lace in Section 8. The property is adjacent to the North Arm of Lake Minnetonka and has a seyerely eroded soil bank along the shoreline. The proposed restoration is not acceptable from an engineering standpoint, and we recommended the following modifications. silt fence must be installed along the perimeter of the shoreline prior to any construction to protect the lake from erosion. The fill soil should be a granular material. Clay soil is not recommended for this type of application. The fill soil should be compacted in no greater than 6 inch lifts to a minimum specified density of 95% of the standard proctor density. The proposed fill and Miragrid is proposed to be installed up to the existing failure plane, as shown on the detail. There is nothing shown to anchor the Miragrid into the existing soil bank. We be..ieve that future problems are likely at the same failure plane as before. We recommend using a system of duckbill anchors that are set into the^ existing soil bank and tied to a series of pipes or bars laid paraiie.. to the shoreline. The Miragrid could then be attached or wrapped around these pipes to anchor it to the side slope. The proposed American Excelsior Biodegradable turf reinforcement is a temporary turf restoration and will not prevent future erosion unless an adequate vegetation and root base has been established. Maintenance of the 1:1 slopes will not be possible. We recommend seeding the slopes with a low maintenance vegetation such as Crown Vetch. Crown Vetch is a spreading plant with a low profile and root base. There are several permanent turf restoration products available such as Miramat which will further increase the stability of the surface. If there is a possibility of scouring of the embankment due to wave action along the shoreline, we recommend the placement of riprap with jfilter fabric to prevent erosion and undermining. Paul. MM • 6t2-636-4600