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Lammersville School District <br /> 202/799-8221 <br /> July 28. 1987 <br /> The geoIoity art the Site consists of a 100 foot thick <br /> seque,..r,e of alluvial clay, slit and sand overlying a clay layer <br /> which in turn overlies the Corcoran Clay. Thr. Corcoran Clay is <br /> a major aquitard in the San Joaquin Groundwater 13asin . <br /> Groundwater in the area is dl videei into three wxtrr hearing <br /> zones : a lower confined zone below the Corcoran Clay; an upper <br /> zone above the Corcoran rlay, which contains both confine., and <br /> unconfined aquifers ; and a shallow, unconfined zone within 25 <br /> feet of the surface. <br /> The water quality in the Tracy area is being degraded by <br /> Intrusion of sallrre connate water as a result of the over draft <br /> of deeper aquifers in the Stockton and Tracy arras . Shadow <br /> groundwater, though utilized for domestic purposes, is generally <br /> ~ poor along the western boundary of the San Joaquin Groundwater <br /> Basin. However, all groundwater i^ the. Tracy area is considered <br /> to be potential drinking water source and is treated as such. <br /> There are approximately 114 wells within a one mile radius <br /> of the site; I10 domestic, 3 municipal and 1 abandoned municipal <br /> well (see Figure 3. Well Location Map) . <br /> The soils encountered during the drilling of the borings for <br /> the monitoring wells were compor.ised mostly of silty r, lays and <br /> it d. In each well boring. several sand and clary strinl(ers were <br /> encnunLored. Depth to „roundwate:r was recorded at approximately <br /> 8 fve:t below grade . <br /> The five wells were ronitored .on June 19. June 22 and June <br /> 2-1 . 1987 for depth to water and presence of product, if any . A <br /> ..: summary of the groundwater monitoring at the "SI to is prevented in <br /> � . Table Ilased no this data , the Interpreted 1,r o it n d w a t e r <br /> 10 <br /> mass nffi��� <br />