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Color Spot, Inc. 'J March 19, 1991 (M88168F) surface aeration. Because PHS-EHD has a clean-up to non-detection policy, normal on-site remedial action techniques such as surface aeration could not be utilized (no one can guarantee absolute clean-up to nondetection limits) . Therefore, SGD recommended that removal and off-site disposal was the only practicable remediation available for the site. With the approval of PHS-EHD, SGD observed the removal of approxi- mately 160 cubic yards of material from the site during the week of January 8, 1990. The approximately 160 cubic yards included excavated material and previously determined contaminated soil piles. Following the excavation of soil which was thought to be contaminated, six verification soil samples were collected from the walls and base of the excavation. The laboratory analytical results obtained from the verification samples indicated only trace concentra- tions of toluene and xylenes at concentrations well below State of California, Department of Health Services Drinking Water Standards (DWS) and are believed to be ambient concentrations. Concentrations of benzene were not detected in any of the verification samples. With the approval of PHS-EHD, SGD conducted a supplemental site assessment at the site during the week of October 8, 1990. This assessment included the advancement of four drill holes to depths ranging from 30 to 90 f( below the ground surface. All drill holes were geologically logged and the sc.� monitored with a PID by an SGD staff geologist. A site specific technical work plan, which was approved by PHS-EHD, planned for the advancement of three drill holes to depths ranging between 60 to 80 feet bgs (dependent on water table elevation) , which were to be completed as 4-inch PVC ground water monitoring wells. The first drill hole advanced was completed as a ground water monitoring well with a total depth of 80 feet bgs. Upon discovering that the well had been set as a dry well, SGD decided to advance a second drill hole to the maximum depth allowed by the mechanical capabilities of the drill rig. This second well was advanced to a depth of 90 feet bgs (maximum drilling depth capability) , however ground water was not encountered. Because continuous field screening of soil cuttings with a PID from grade to total depths at all four drill hole locations did not indicate the presence of trace concentrations of hydrocarbon contamination, and because ground water was not encountered within the drilling depth capabilities of the drill rig employed (Mobil Drill Rig Model B-61) , SGD concluded that adequate ground water monitoring wells could not be constructed nor are they necessary at the site according to the State Water Resources Control Board (SWRCB) Leaking Underground Fuel Tank (LUFT) Field Manual. The most recent version of theWWRCB LUFT Field Manual (dated October 18, 1989)3states in Step No. 2 of Category No. 2 (page 32) "soil samples should be collected from multiple soil borings to check for lateral as well as vertical movement of contaminants in the soil." This section goes on to state "the borings should be deep enough to extend through the entire depth of contamina! 11