10-26-1994 Council Agenda - Laserfiche WebLink

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Page Three At Boring 1. the black clay surficial layer was found to be underlain by a 1' thickness of grayish brown clayey sand. We judged this to be either mixed alluvium or an extension of the fill system. Again. based on the penetration value obtained. this layer was found to be in a very soft condition. The logs indicate the presence of sandy lean clay glacial till below the surficial fill or topsoil. The approximate upper surface of this layer was at a depth of 1' toward the front and 6' towards the rear of the proposed house. Based on the penetration values obtained, the till was found to be very competent. or of firm to hard consistency. At Boring 2. the lower portion of the glacial till formation was a clayey sand material which again was found to he firm to hard. based on the N- values. Groundwater Lcvets - The bore holes were checked for the possible occurrence of groundwater during and after completion of the drilling program. During the drilling procedure at Boring 1. it was observed that the soft clay samples retrieved above a depth of 6' were wet to saturated. This suggested the presence of a perched water condition above the competent, relatively slow- draining clay. However, no standing water was encountered in the boreholes after completion of the drilling. We would anticipate the "true" groundwater level at this site to be below the bottom of the borings. based on surficial hydro9eology maps published by the Minnesota Geological Survey. tlroundwatcr levels can be expected to vary seasonally. yearly and with variations in precipitation and surface infiltration. ENGINEER I NG__ REVIEW Project _Da:ta - We have not been provided with information regarding the actual configuration of residential construction on this lot. We do understand that adjacent houses were constructed as shallow. five course basements and we anticipate that the proposed structure would most likely consist of the shallow or half basement configuration. with an attached garage. The garage floor would normally be situated about 2 -2.5' above the level of the street and the basement floor would be 3.5' below the garage floor. On this basis. the basement floor would be at about elevation 99', with respect to our benchmark. If a rear walk -out configuration is employed. the walk -out wall footing would then be at about elevation 95.5' and the remainder of the basement footings could be slightly higher, closer to floor level, while maintaining at least 42" of soil cover for frost protection. Page 50