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E <br /> Effluent that infiltrates and percolates through this fine soil material (clay and silt sized particles) <br /> will undergo biological treatment of the effluent before reaching the water table (-73 ft below <br /> r grade). Biological treatment includes the destruction of bacteria and viruses. <br /> For percolation test purposes, the property was divided into three separate areas of approximately <br /> f2.07 acres each to represent three proposed parcels. These three areas are illustrated on the enlarged <br /> F. Assessor's,Parcel Map and referenced as the"West Parcel," "Middle Parcel," and "East Parcel." <br /> The remaining 1.03 acre area where the above-referenced house is located, could not be perc tested <br /> due to "distance from well"constraints. There is a domestic well and a non-functioning irrigation <br /> F, well near the house. Consequently, a 150-foot distance could not be maintained from these two <br /> wells. In addition, there are no domestic wells to the north or east of the subject property within 50 <br /> F. feet of the border, and therefore, not within 150 feet of the percolation tests. <br /> The surface and subsurface investigation of the property soils under the three proposed parcel areas <br /> began with the use of a truck-mounted drill rig. Solid stem auger and a split-spoon sampler were <br /> !' 1 used to drill the percolation test borings and to sample soil at the prescribed depths. <br /> Logs of boring for each of the three test borings are found in Appendix 4 and illustrate the <br /> subsurface soil characteristics encountered in each of the three 24.5 foot percolation test borings. <br /> A Standard Penetration Test (SPT) was conducted at the referenced depths to illustrate the physical <br /> condition of the both cohesive soils (silts and clays), and cohesionless soils (sand and gravels) <br /> " found at the deeper depths. All of the SPT test results indicate the subsurface soils to consist of <br /> dense and very dense cohesionless soils, and hard cohesive soils. <br /> The logs illustrate the variability of the strata encountered. Classification b the USDA and <br /> g Y Y <br /> Unified Soil Classification System (USCS) includes a sandy loam (sandy silt - SM), a loam (silt - <br /> ML), a clay loam (clayey silt - CL-ML), and a silty clay(ML-CL). The surface soils at the west <br /> end of the property have a lower clay content, which becomes increasingly heavier to the east of <br /> the property, as noted: The West Parcel soils contain a comparatively lower clay content soil of <br /> 14%, which increases to 28% for the Middle Parcel, and to a very high clay content of 42% for the <br /> East Parcel. The deeper subsoils show a reverse of this trend with the Middle Parcel and East <br /> f-- Parcel having lower clay content and higher sand content subsoils down to the 24-foot depth. <br /> Although the deeper subsoil clay content decreases from west to east, there still remains sufficient <br /> clay at the deeper depths to maintain biological activity. <br /> I ; A Water Well Drillers Report (Well Log) for a well drilled at 7425 Orford Road can be found in <br /> Appendix 7, along with other surrounding Well Logs. The Orford Road Well Log illustrates the <br /> underlying lithology to be clay from the surface to 64 feet. As referenced above, soil borings <br /> completed for perc testing indicate a sandy loam at the 10 to 24 foot depths at the middle and east <br /> sides of the property. From 64 feet to 70 feet, which is the near the depth of the current static water <br /> level, is a fine sand stratum. Below this stratum are intervening strata of clay and sand down to a <br /> i blue clay stratum at 250 feet. This may be the top of the Corcoran Clay layer. <br /> t Particle Size Analysis discussed above, and Nitrogen Contents for each of the tested soil samples <br /> are summarized in the following Table. . (Note: Samples from the intermediate (--12 feet) depth <br /> and the deep depth (24 feet)were not tested for the Middle Parcel since these deeper soil physical <br /> characteristics were very similar to the East Parcel). <br />� 3 <br />' <br /> F11 Chesney Consulting <br /> t <br />