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tion, flocculation/clarification, filtration, and also pre-treat- <br /> ment of city water. <br /> In 1990, Exceltrans performed a partial closure of the WWTF area. <br /> This included thorough cleaning of all process equipment . Since <br /> that time, all of the equipment has been removed from the site. <br /> 3 . SOIL BORINGS <br /> ' 3 . 1 Selection of Boring and Sampling Locations <br /> Borings S-1 and S-2, with a total depth of five feet, were posi- <br /> tioned in the former WWTF area. They are located alongside a <br /> drainage trough (ditch) in the slab, and on cracks which cross <br /> the ditch. This ditch carried rinse water from wash-down of the <br /> ' treatment facilities, and possibly spilled process waters . The <br /> concern was that some solutions bearing metals or cyanide may <br /> have leaked through the cracks into the underlying soils . <br /> Borings B-1 through B-4 had total depths of 28 to 30 . 5 feet, and <br /> their locations and samples served differing purposes, as de- <br /> scribed below: <br /> B-1 . Placed to sample soils at three depths and also ground- <br /> water near the acid loading area (Area 11) , where stains have <br /> been observed on the concrete surfaces of the vault, adjacent <br /> to the former holding tanks . <br /> ' B-2 . Initially selected as a control point for groundwater <br /> flow direction, it was later selected as an upgradient sam- <br /> pling point for background groundwater quality. <br /> B-3 . Placed to sample groundwater adjacent to the former <br /> cyanide tanks in the vault of Area 10 . <br /> ' B-4 . Selected to sample groundwater downgradient from chemi- <br /> cal storage and WWT process areas . <br /> 3 .2 Drilling and Sampling of Soils <br /> Drilling was performed by Soils Exploration Services on October <br /> 20 and 21, 1994 . For the four deep borings (total depth 28 or <br /> 30 . 5 feet) , a CME-55 drill rig with 8-inch hollow-stem augers was <br /> used; for the two five-foot borings, a hand auger was used. <br /> Sampling for the sole purpose of preparing boring logs was con- <br /> ducted with a standard penetration sampler (SPT) ; soil samples to <br /> be packaged and shipped for analysis were obtained with a Cali- <br /> fornia-modified split-spoon sampler (CAMSS) with diameter of 2 .5 <br /> inches, lined with brass sleeves 2 inches in diameter and 6 <br /> 2 <br />