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�Bonestroo <br /> M e m o �` ��� �� p Rosene <br /> Anderlik& <br /> �Assoctates <br /> E�gl�ccrs 6 Archlcects <br /> Project Name: 1489 Shoreline Drive Clienf: City of Orono, MN <br /> To: Tom Kellogg File No: 000139-05-001-0 <br /> From: Philip J. Caswell, P.E. Date: 6/9/05 <br /> Re: Proposed Shoreline Improvements <br /> Remarks: I have reviewed the proposed repair for the shoreline slope "wash-out" submitted to the City for <br /> 1489 Shoreline Drive, and have the following comments: <br /> 1. The submitted design is not signed by a licensed engineer and has no backup calculations or other design <br /> information. This must be a condition of permit approval. <br /> 2. The proposed repair involves constructing buried timber walls, tied back into the slope with 3/8" steel cable <br /> to treated deadmen anchors. The design sketch is conceptual only, since dimensions are not provided for <br /> the anchorage cable (length), depth of deadmen anchors into the retaining soil, or the size, depth or <br /> spacing of the steel sign channels. <br /> 3. It is difficult to determine whether, conceptually, this approach wilf work. There are a number of concerns <br /> that stand out as potential problems: <br /> a. The backfill proposed is "clay fill", which exerts a higher lateral earth pressure than a granular fill <br /> material — particularly when wet. I would recommend that a free-draining granular material be use, <br /> or the higher saturated clay pressures must be accounted for in the design. <br /> b. ft does not appear that the existing slope will be modified. "Benching" the slope is recommended to <br /> reduce the potential for creating a natural slip plane below the imported fill. <br /> c. There is no provision for drain tile or other means of collecting and diverting water that may enter <br /> the fill soils and accumulate behind the walls as it percolates down the slope. This additional <br /> hydrostatic loading can be significant. <br /> d. Using ferrous (steel) and organic (wood) materials below grade can provide only a 10 — 20 year <br /> design life, as they will rust and decay over time. <br /> Without the signature of a P.E. who will take responsibility for the design of these "subterranean" walls, or some <br /> documentation to validate the design, I would not recommend allowing this repair to proceed as shown. <br /> Bonestroo, Rosene, Anderlik and Associates, Inc. www.bonestroo.com <br /> ]SL Paul OfFlcu: 0 Mllweukao OtHco: ❑Rochoslor OfNca: 0 WIIImerOtflca: ❑St Cloud OHice: ❑Llbertyvllla OHlce: <br /> 27J5 Wesl Highway 36 12075 N.Carporalc Parkway.Sle 200 1117���SVeel N[ 205 51�SVeel SW 3721 2J�^Streel S 1860 West Winchester Rd,Ste 106 <br /> Sl Paul,MN 55113 Mequon,WI 57092 Rahostor,MN 55906 Willmar,MN 56201 SL Cbud,MN 56301 Grayslake,IL 600J0 <br /> Phonc:651-6JG-A600 Phone:262•6A]-9032 Phone:507-282-2100 Phone:J20•214-9557 Phone;J20-251-455� Phone:847-54B-677A <br /> �ax:651-676-1711 Faz:7.62•241•4901 Fax:507-282-310� Fax:�20-214•9458 Fax:320-251-6252 Faz:847-54&6979 <br />