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Mig -.' r �y�? - '�� - �'"x n i S Work Plan May 17, 1991 ARCO Service Station No. 2168,Stockton, California AGS 31009-1 w - Drilling Before drilling, we will acquire a permit from the S,1PHS for drilling a maximum of seven soil borings. Applied GeoSystems will contact Underground Service Alert at least 48 hours before drilling to delineate publiz utility lines at the site. Before drilling,we will hand auger ., each borehole to 3 to 5 feet below grade. We will observe a licensed well driller drill four 8-inch-diameter soil borings near the existing gasoline tank cavity an k cavity. A truck-mounted rig equipped with hollow-stem augers will be used. The drilling will be performed under the guidance of a field geologist. The earth materials will be logged using visual and manual methods as drilled using the Unified Soil Classification System. A photoionization detector(PID)will be used to evaluate soil samples for gasoline hydrocarbons. Field instruments such as the PID are useful for indicating relative Ievels of gasoline hydrocarbon vapors but do not detect the concentration of gasoline hydrocarbons present with the sari precision as iaboratory analyses. Any subjective evidence of gasoline hydrocarbons such as soil discoloration or obvious odor will be noted. The first boring will be drilled near the gasoline tank cavity approximately 2-1/2 feet from the edge of the existing tank area, near the fill ends of the product tanks, to 30 feet below grade, ground water, or auger refusal, whichever is encountered first. If the PID reading of the soil sample collected at 30 feet below grade is greater than 50 parts per million by volume (ppmv),we will drill until: (1) two consecutive samples collected at 5-foot intervals f produce PID readings of less than 50 ppmv, (2) until we encounter ground water, or (3) auger refusal. 7 f I ARRIped SeoSpetems