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lined with 3 brass tubes and driven by a 140 lb falling hammer. <br /> Between each part of sampling, the sample was thoroughly cleaned <br /> in SP solution and rinsed in clean and deionized water . The <br /> bottom brass tube from each sampling was immediately covered with <br /> aluminum foil, capped, labeled, placed on ice, and sent with a — <br /> chain of custody form to a California-certified laboratory for <br /> analysis. The remaining tubes were used to classify the soil, _ <br /> and were also scanned with an HNU portable photoionization <br /> analyzer for the presence of volatile hydrocarbons. <br /> The four boreholes were completed as monitoring wells. In each <br /> borehole, 20 feet long, 4" diameter 0 . 020 slot, PVC screen was <br /> installed at a depth of 30 feet (well MW4 , MW5 , and MW6 ) and 32 . 5 <br /> feet (well MW7 ) . Above the screen, up to the surface, 4" — <br /> diameter Schedule 40 blank PVC pipe was installed. Each well was <br /> secured with a cap and a water-tight cast-iron monitoring well <br /> cover. Each well was equipped with a well tag containing <br /> pertinent information such as depth, screened interval, diameter, <br /> owner ' s name, and well number. The annular space around the <br /> screen and for at least one foot above it was filled with #3 <br /> Monterey sand. To prevent clay surface infiltration into the — <br /> aquifer, the annular space above the sand pack was sealed with <br /> two feet of bentonite and cement grout up to the surface. A — <br /> simplified representation of the construction of each well is <br /> shown on the well logs (Appendix A) . <br /> After installation, each well was developed to remove fine <br /> sediment which had accumulated inside the coring and to improve <br /> hydraulic properties near the boreholes. Wells were developed by <br /> bailing to remove the sediments and pumping with a submersible — <br /> pump to remove fine particles from around the well. All wells, <br /> MW4, MW5 , MW6, and MW7 were developed. — <br /> From each on-site monitoring well samples of ground water were <br /> collected for analysis. Prior to sampling, each well was purged <br /> of five casing volumes of water. Water samples were collected <br /> 18 <br />