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METHODOLOGY <br /> The field investigation portion of this study included <br /> the drilling of ten exploratory soil borings and drilling and <br /> installation of ten groundwater monitoring wells, the <br /> locations of which are illustrated on Plate 2. <br /> A monitoring well construction permit was obtained from <br /> the San Joaquin County Department of Environmental Resources. <br /> Stanislaus County permitted the drilling of ten exploratory <br /> soil borings and the drilling and installation of ten <br /> groundwater monitoring wells prior to the commencement at the <br /> field portion of the investigation. <br /> Drilling and Soil Sam in <br /> Drilling was pe.rforr.ed on March 8 and 9, 1990 and on <br /> April 2 to 4, 1990 by West Hazmat Drilling of Rancho Cordova, <br /> California, utilizing a truck-mounted drill rig equipped with <br /> flight hollow-stem auger. The exploratory soil borings were <br /> drilled using 6-inch O.D. auger, while the borings for the <br /> groundwater monitoring wells were drilled using 10-inch O.D. <br /> auger. A Dames & Moore geologist was present during drilling <br /> -•, -' to assist in obtaining relatively undisturbed samples of the <br /> subsurface materials, to maintain a log of borings, to field <br /> screen samples with an Hnu Photoionization detector to device <br /> 4 capable of detecting volatile organic hydrocarbons as a trace <br /> gas) , and to make observations of the site and surrounding <br /> area conditions. The samples obtained from the borings were <br /> classified according to the Unified Soil Classification <br /> System and relatively undisturbed samples were retained for <br /> chemical analysis. <br /> _. Subsoils were sampled at approximately 5-foot .intervals, <br /> commencing at an approximate depth of five feet below the <br /> existing grade. Samples were obtained by means of a <br /> California Modified split-spoon sampler which was lined with <br /> Pd brass sleeves. The sampler was advanced by blows from a <br /> 140-pound hammer falling 30 inches. Upon retrieval, soil <br /> samples in sleeves retained for chemical analysis were <br /> - contained with a plastic cap over aluminum fail, and taped at <br /> each end. The samples were labeled and placed into a cooler <br /> chest on 'lice" under proper chain of custody protocol for <br /> „, shipment to analytical laboratory. <br />