2005-P09263 - land alteration - Laserfiche WebLink

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�. x�y x�� Wayzata, Minnesota Project No. 95286 Our evaluation is based on a simple observation of the property. Further ass�ssment should be macie by drilling soit borings in order to evaluate t� stratigraphy of the soil wtuch compose the slope,perfornung laboratory testing of the soil in order to evaluate its strength properties with depth, obtaining a survey of the property in orde�r to identify the topography and installing field instrumentation, such as inclinas�teters, in arder to monitor for movement. . STABILIZATION In comentional geotechnical engiaeering practice the stability of a slope is expressed in terms of its factor of safety. In this approach a factor of safety less than 1.0 indicates failure, whereas a slope wauld be stable with a factor of safety gre�atrer thaa 1. In desigis, the es�gineer also inctudes a"safety fa�tor"to account for variables. The question now becomes has the movement which occun�ed changed the slope conditions resutting in a new stable condition or can movement once again occur. Ba�ed on our observatioas and t+ecent rainfall events, it appears that without mitigation and repair,the stope may indood move again. Fw�t�er study wotdd be raquired invo�ving soil borings,laboratory testing,surveying and field monitoring. Ripnp at Tce One of the first things tha�t can be done to help mitigate tho potential for further movcment would be to add riprap at t�e bottom of the slope thaz would reduce the potentiai for et+osion ax�uring during high water and add weight to the toe of the slope, We uaderstand that Concept Landscaping is accomplishing this task. Riprap has been installed tio the reporbed 100-year flaod level of 931.5 ft. We recommend that any repa�r include a drainage collectivn plan. Roof drainage, backyard drainage and aay other poteutial source of water during a rainstorm should be collectsd and rodirected away from the slope tha�t failed or pipes installed to take the drainage through the slop�. Yto-Gradc S1ope One repair option that could be done would be to remove thc slide scarp by cutting lback the top of the slope to at least a 2H:1 V to 3H:1 V grade. This reg�radi�ag would eli�minate a portion of the b�ckyard area but woald pruvidc a more stable environment near the rear of the home. An imparted granular, preferably czushed stone, soil could be repYacsd that 1�a friction angle. A crushe8 stone could bc placed that has a fricdon angle of near 40 to 45 degrees, whereas a select sand could be placed that has a friction angle near 30 to 35 degrees. Sepnentsl Blodc Ret�iag Walt(SRR� �e repair option would ��mstruct a geogrid reinforced reta�niag watl suppor�ed o� fic�ground that would ailow for the ren�ovai of the snil material in the failure area. Two option�for retaining walls would be a cast-in-place reinforc�concrete wall or a geogrid �+einforced modular block walt, such as the Anchor Highland Block. The pour�d ia�s `3ale-'T�Engia�erin�,Ia�c.,�EPTE�rIBER.,2005 4