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Mr Chuck Carmel Project 0805-11101 September 12, 1994 Page 2 Report 30041-3) The lateral extent of residual gasoline hydrocarbons in soil was delineated at the site, except for the area near the southeast corner of the site Although trace to low concentrations of gasoline hydrocarbons were detected below 70 feet bgs, the vertical extent of residual gasoline hydrocarbons in soil appeared to be limited to between 50 and 70 feet bgs, dependent upon location and from surface grade to approximately 70 feet bgs beneath the dispenser islands RESNA performed a vapor extraction test at the site on October 14, 1991, using vapor extraction wells VW-1, VW-2, VW-3, and VW-4 (RESNA, January 31, 1992, Report 30041-2) The results of the test indicated that vapor extraction is a feasible means to remove residual gasoline hydrocarbons from the soil In December 1992, RESNA observed drilling of one soil boring (B-26) and construction of a vapor extraction well (VW-17) Residual gasoline hydrocarbons were detected in soil samples collected from the soil boring (RESNA, March 18, 1993, Report 30041-4) Groundwater was not encountered in the soil boring The lateral extent of residual gasoline hydrocarbons in soil has been delineated in all directions with the exception of the vicinity south of boring B-26 In August 1993, RESNA researched the water supply well located at the site Results of the investigation indicated the depth to first-encountered water was not indicated on the Department of Water Resources drniler's log for the water-supply well (June 26, 1969), however the log does indicate that the depth to water after development was 100 feet below surface grade (bsg) RESNA measured state. groundwater after pumping the well for 0 25 hour Static groundwater was measured at approximately 58 51 feet below the access plug Based on current vapor extraction wells drilled to 115 feet bsg, RESNA concluded that first-encountered groundwater beneath the site is below 115 feet bsg, groundwater is under confined conditions, and the top of the first saturated unit is most likely 396 feet bsg or deeper WORK CONDUCTED SECOND QUARTER 1994 AND WORK IN PROGRESS Two previous access agreements were submitted by RESNA to the property owner south of the site the first access agreement was submitted in August 1993 This access agreement was revised to address concerns of the property owner and resubmitted in April 1994 EMCON will submit a third access agreement to the property owner south of the ARCO site for drilling three soil borings and installing vapor extraction wells Once ARCO has received authorization to access property, EMCON will proceed with final assessment activlttes sA(_1pi(N)X05N0X051110 ]tai-94 pks 5