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February 13, 1998 Page 3 former used oil UST (GTI, June 28, 1994). Thirty seven soil samples collected from the borings were analyzed. The maximum concentrations of TPH-g and benzene (15,000 and 160 ppm) were reported in a sample from boring SB-4, in the former UST pit. Groundwater was reported at a depth of 43 feet bgs. In November and December 1995, GTI drilled four borings (SB-6, SB-7, SB-9, and MW-7), obtained groundwater "grab" samples from borings MW-7 and SB-9, and installed one groundwater monitoring well (MW-7)to further define the extent of hydrocarbons in soil and groundwater(GTI,January 25, 1996). GTI reported maximum concentrations of TPH-g and benzene (640 mg/kg and 1.4 mg/kg, respectively) in a soil sample from 40-1/2 feet bgs boring SB-9. Results of groundwater grab sampling indicated 1,900,000 ppb TPH-g in MW-7 and 260,000 ppb in boring SB-9. Benzene was reported as nondetectable in both groundwater grab samples. In October 1997, PACIFIC installed two wells (MW-8 and MW-9)to define the extent of gasoline hydrocarbons in groundwater downgradient of the site and vertically adjacent to the former UST complex. PACIFIC reported maximum concentrations of TPH-g and benzene (6,200 ppm and 110 ppm) in a soil sample from 35 feet bgs in Well MW-9. Maximum reported concentrations of TPH-g and benzene in soil from 65 to 75 feet bgs in Well MW-9 were 8.1 and 0.063 ppm, respectively. Soil results from Well MW-8 reported nondetect TPH-g and BTEX concentrations. Well MW-8 was completed with a screened interval of 22 to 42 feet bgs to assess the downgradient extent of gasoline hydrocarbons within the shallow groundwater zone. Well MW-9 was completed with a screened interval of 52 to 57 feet bgs within a saturated silty sand layer. Initial groundwater samples were collected from Well MW-8 and MW-9 on October 6, 1997. Concentrations of TPH-g and benzene in Well MW-8 were reported at 370 and 19 ppb, respectively. Concentrations of TPH-g and benzene in Well MW-9 were reported at 130,000 and 20,000 ppb, respectively. MtBE was reported as nondetectable. QUARTERLY MONITORING Quarterly monitoring has been ongoing at the site since March 1991. Historical groundwater gradient has been generally consistent to the south-southeast. Water levels have fluctuated in the wells from approximately 27 feet bgs recently to 47 feet bgs in 1992. Generally, groundwater levels have risen at the site since 1994. Blaine Tech Services, Inc. (Blaine) began monitoring at the site in November 1994;prior to that GTI performed the quarterly sampling. Nondetectable to low concentrations of hydrocarbons in Wells MW-3, MW-4, and MW-6 suggest that the hydrocarbon plume in groundwater has been defined in the areas north, northwest, and west of the former USTs. Hydrocarbon concentrations in Well MW-1, located west of the former USTs, have declined significantly over time and are now low to nondetectable. Hydrocarbon concentrations in Well MW-5, southeast of the site, have been relatively consistent over 7G007-013-01/workplan