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Old Snelling Avenue Geotechnical Recommendations <br />October 7, 2020 <br />Page 2 <br /> <br /> <br />Table 1 – Pavement Thickness <br /> <br />SUBSURFACE CONDITIONS <br />Fill was encountered below existing grade in all borings with the exception of Boring B-10. The fill varied <br />in depth from 1.5 feet to 11.5 feet below the surface. The fill was typically classified as clayey sand (SC). <br />Sometimes the fill is described as having trace organics, trace gravel, and/or pieces of bituminous <br />pavement. Underlying the fill is glacial till typically classified as clayey sand (SC) and sandy lean clay <br />(CL). The fines content varied between 41% to 62% for the samples tested in glacial till. Borings B-1, <br />through B-3 and B-5 terminate in glacial outwash typically classified as poorly graded sand (SP). The top <br />of the sand is between 7 to 11.5 feet below the surface. Boring B-8 encountered a layer of peat between <br />the fill and the glacial till at a depth of 7 to 9 feet. The peat is described as rather stiff with trace gravel <br />and a moisture content of 235%. <br />Apparent hydrocarbon odor was detected and documented at some samples in a majority of the borings <br />during drilling. The apparent odor was documented in the boring logs. The odor was encountered in the <br />samples from the fill, glacial till, and glacial outwash. This memorandum only addresses the geotechnical <br />recommendations for the project. It is recommended to consult with qualified personnel to provide <br />recommendations with respect to contaminated soil or groundwater. <br />GROUNDWATER CONDITIONS <br />Groundwater was observed at borings B-1 and B-12 during drilling operations at a depth of 14 feet below <br />the surface. The groundwater elevation at B-1 is 878 feet and 900 feet at B-12. It was assumed that the <br />groundwater at B-12 is perched and that the groundwater elevation across the site will be at the Lake <br />Johanna surface water elevation. <br />Groundwater depths recorded during drilling can be unreliable because of the short time period of the <br />observation. In silty, clayey, or organic soils, longer duration observations within the borehole are typically <br />necessary to obtain a more accurate measurement of the water table. Perched water and fluctuation of <br />the groundwater elevation should be expected during periods of precipitation and snow melt above clay <br />Boring <br />Top <br />Pavement <br />Thickness <br />(in.) <br />Aggregate <br />Base <br />Thickness <br />(in.) <br />Bottom <br />Pavement <br />Thickness <br />(in.) <br />Total <br />Pavement <br />Thickness <br />(in.) <br />B-1 3 9 7 19 <br />B-2 3 8 10 21 <br />B-3 7 11 6 24 <br />B-4 3 17 8 28 <br />B-5 3 11 8 22 <br />B-6 5 13 9 27 <br />B-7 4 11 11 26 <br />B-8 4.5 24 0 28.5 <br />B-9 5 24 0 29 <br />B-10 4.5 20 0 24.5 <br />B-11 3 10 9 22 <br />B-12 4.5 20 0 24.5 <br />B-13 11 6 0 17