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• October 14, 1993 Working To Restore Nature ARCO Station No 548, Sacramento, California Soil cuttings generated during drilling are stored onsite on and covered with plastic sheeting If possible, drill cuttings exhibiting subjective evidence of hydrocarbons or producing a positive response on the PID are separated from those drill cuttings exhibiting no subjective evidence of hydrocarbons Four soil samples are collected from drill cuttings and composited into one sample at the laboratory to evaluate disposal options for the soil Borings not converted to wells are backfilled to surface with a slurry of cement, bentonite, and water. Construction of Vapor-Extraction Wells Vapor-extraction wells are constructed of thread-jointed,4-inch-diameter schedule polyvinyl chloride (PVC) casing No chemical cements, glues, or solvents are used in well construction The screened portion of the wells consists of factory-perforated casing with 0 10-inch-wide slots A maximum interval of 25 feet of slotted casings is used Pea gravel is placed in the annular space opposite the screen to approximately 1 foot above the top of the slotted casing A 2-foot bentonite plug is placed above the sand pack, and a cement- bentonite slurry is used to fill the remaining annulus to the surface A traffic-rated cast- aluminum utility box with a PVC apron is placed over each wellhead and set in concrete flush with the surrounding concrete pad. This box has a watertight seal to protect against surface water infiltration and is opened with a special wrench The design of the box discourages vandalism and reduces the possibility of accidental disturbance of the well After the appropriate local and State environmental agencies indicate that remediation of soil is no longer required, the vapor-extraction wells will be removed. A drill rig is used to remove the casing and gravel pack, and the bore hole is backfilled with grout composed of cement and bentonite from the bottom of the hole to surface grade Monitoring-Well Construction Monitonng wells will be constructed in the borings with thread-pointed, 4-inch-inner- diameter, Schedule 40 PVC casing. No chemical cements, glues, or solvents are used in well construction. The screened portion of each well will consist of factory-perforated casing with 0 020-inch-wide slots The well screen will extend from the total depth of the well to approximately 5 or 10 feet above the groundwater surface This screened interval allows sampling at the air-water interface during seasonal fluctuations of the groundwater level The annular space in the well is packed with number 3 sand to approximately 1 to 2 feet above the slotted interval A 3-foot thick bentonite plug is added above the sand pack to prevent the cement from entering the well pack The remaining annulus is backfilled to grade with a bentonite cement slurry 0817ccar 30004-low