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! A <br /> The post-Eocene sediments yield fresh water to wells in all but the <br /> extreme western part of the San Joaquin Valley. Most of the wells <br /> in the valley draw from the deeper formations, sarticularly the <br /> are generally <br /> Mehrten and Laguna Formations. These silt and clay <br /> recharged from the Quaternary age sand, gravel, , <br /> deposits of active stream channels. <br /> Mean sea level elevation in the vicinity of Collegeville is <br /> approximately 57 feet. The topography at the site is very flat <br /> with a gently sloping surface gradient to the west. The site <br /> hydrogeology has been interpreted from exploratory soil boring logs <br /> B1 and B2. The boring logs are presented in Appendix B. Cross <br /> section A - A' (Figure 4) has been constructed from the boring logs <br /> to illustrate the stratigraphy beneath the site. The location of <br /> the cross section is shown in Figure 2. <br /> Although the upper 25 feet of material n the two borings <br /> ring BI consists Of <br /> compacted fill, the remaining stratigraphy between <br /> appears to be relatively uniform and consistent across the site. <br /> The uppermost soil horizon from just below grade consists of fine- <br /> grained clayey silt to a depth of approximately 5 feet. This fine- <br /> grained unit is underlain by a sequence of silty sands, poorly <br /> graded sands and silts to a depth of at least 51 feet below ground <br /> r <br /> surfLce. Groundwater was not encountered in either boring. Based <br /> on the State of California Department Resources Agency <br /> publication <br /> entitled "Historic Ground water Levels in San Joaquin County" the <br /> 1990 water levels in wells in the vicinity of Collegeville ranged <br /> from 90 to 120 feet below ground surface. <br /> 5.0 IMPACT TO BE14EFICIAL USES OF GROUNDWATER <br /> The site is located on the northeast corner of the intersection of <br /> Mariposa and Jack Tone Roads. Land use in the area is mixed <br /> agricultural and residential. The area around the site is occupied <br /> ~ by a secondary public school to the west, a residential family <br /> dwelling to the north and vacant fields to the east and south. <br /> The nearest body of surface water is Mormon slough, approximately <br /> - ... y_,._.._g_ <br /> --... - -. <br /> �# miles _north of_the.......site.-._....__ ��resent.l raundwater in usable <br /> 9 <br />