ARCHIVED REPORTS XR0001334 - Laserfiche WebLink

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August 11, 1992 �� } ARCO Service Station 2168, Stockton, California Working To Restore Nature FIELD INVESTIGATION The drilling operations, soil sampling, and well construction and development are summarized below. Our field methods are described in an attachment to this report Copies of the Chain of Custody Records and laboratory reports for soil and water samples are attached. Work was conducted in accordance according to field methods outlined in our Work Plan No. 31009-4W, dated April 7, 1992. Drilling, oil Sampling. and Well Construction 1 During April 27 through April 29, 1992, a geologist from RESNA observed Westex Drilling of West Sacramento, California, drill one 8-inch-diameter and two 10-inch-diameter soil borings (B-5 through B-7) and install two ground-water monitoring wells (MW-1 and MW- 2) During May 5 through May 7, 1992, our geologist observed Wayne Drilling of Lincoln, California, drill one 8-inch-diameter and four 10-inch-diameter soil borings (B-8 through B- 12) and install a third groundwater monitoring well (MW-3) Soil samples were collected at approximately 5-foot intervals during drilling and were identified using visual and manual methods and classified according to the Unified Soil Classification System (Plate 3) During drilling, ground water was encountered at approximately 41 to 43 feet below grade. Descriptions of the materials encountered are presented in the Logs of Borings (Plates 4 through 22) Soil beneath the site consists primarily of silt to clayey silt to a depth of approximately 33 feet bsg, with lenses of clay, silty sand, and sand Soil from approximately 33 feet bsg to ground water consists of sand and silty sand Westex Drilling installed ground-water monitoring wells MW-1 and MW-2 in borings B-5 and B-6, respectively Wayne Drilling installed groundwater monitoring well MW-3 in boring B-8 and vapor-extraction wells VW-1, VW-2, and VW-3 in borings B-9, B-10, and B- 11, respectively Well construction details are illustrated on the Logs of Borings A technician from RESNA developed the monitoring wells on May 8, 1992 Four soil samples were collected from the drill cuttings and composited into one sample in the laboratory for analyses. Results of the composite soil sample were used to evaluate disposal options of the drill cuttings. On May 20, 1992, at ARCO's request, Dillard Trucking of Byron, California, disposed of the drill cuttings at BFI Landfill, Livermore, California (verification letter enclosed) 0526=u2 31009-4