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, . Mr. Donald C. Mogen Page 2 August 2, 1978 Results The log of soils encountered in the borings is shown on the attached soil boring log sheets. Groundwater was not encountered in the borings. Percolation tests indicated the following percolation rates in ' minutes per inch (mpi) : Surface Test No. Elevation Hole Depth Soil at Test Depth Rate, mpi P-1 90.0 33" siity ciay (cL) 120.0 P-2 87.7 33" Silty Clay (CL) 30.0 P-3 89.3 33" Silty Clay (CL) 40.0 P-4 86.8 30" Sandy Clay (CL) 18.5 P-5 90.8 33" Silty Clay (CL) 48.0 P-6 87.6 30" Sandy Clay (CL) 30.0 Recommendations Based on the results of the soil borings and the percolation tests, it is my opinion that the soil and water condit=ons on the site are suitable for the installation of an individual sewer system with a drainfield as the soil absorption unit. It is suggested that the drainfield be designed using the average percolation rate of 47.7 mpi. For a three bedroom house constructed on the site, the recommended drainfield absorption area should be 915 square feet. Only trench bottom area is considered as being effective. With standard two foot width trench, 458 linear feet of tile line would be required. We recommend that two septic tanks be used at the site. The first should have a capacity of at least 900 gallons and the second a capacity of from 500 to 900 gallons. Recommended locations are shown on the attached figure. Detailed plans should be prepared by your contractor. Topographically, it is apparent that a slight amount of levelling will be required at the drainfield area. You indicated that the proposed house will be a rear walkout, Therefore, the secondary drainfield site is assumed to be simply expansion of the primary site to the rear of the house. This allows for gravity fall from basement facilities. Based on the results of the soil borings, it appears that ground- water levels will not be a problem at the site.