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1 Corrective Action Plan Prior to the monitoring well installation, in November 1989, a soil boring designated as B-9 had been drilled adjacent to the UST. Analyses of soil samples collected during the drilling of soil tboring B-9 and the adjacent monitoring well MW-1 (now BEI-MW3) indicated the soil was impacted from near the surface to a depth of more than 20 feet bgs. The highest concentrations of TPHg were found at a depth of 15 feet bgs. Also, in both borings near the former UST, the ' elevated TPHg concentrations were evident in samples taken as high as 5 feet bgs. This occurrence indicates the petroleum release may have resulted from a leaking dispenser or piping ' most likely located in the immediate vicinity of the UST. The wells installed by Greg Drilling for Blymer were completed at a depth of approximately 30 ' feet bgs. The water table at the time of well installation was approximately 20 feet bgs. The wells were screened from 15 feet bgs to the bottom. Casing size for the Blymer monitoring wells has been reported at different times as either 2-inch-diameter or 4-inch-diarneter. Field ' observation has shown, however, that they are, in fact, 4-inch-diameter wells. The well construction data for all monitoring wells associated with the site investigations are summarized in Table 2. ' With respect to groundwater gradient and flow direction, monitoring well BEI-MW3 is considered to be located at the source, At various times during the groundwater monitoring tperiod, well BEI-MW2 has been downgradient and crossgradient. BEI-MW1 has been both upgradient and crossgradient of the source. », In November 1991, SRK installed three monitoring wells and two test borings. The monitoring wells are designated on the site plan(Figure 2) as SRK-MW1, SRK-MW2, and SRK-MW3, the t test borings as SRK-BH1 and SRK-BH2. During drilling of the wells and test borings, soil samples collected from depths of 15 feet and 30 feet bgs from each boring were analyzed. No hydrocarbon concentrations were detected in any of the samples (see Table 1). During the time t of drilling, the depth to the water table at the site was approximately 24-25 feet bgs. The wells were completed at depths of 38-39 feet bgs and were screened from 23-24 feet bgs to the bottom. The sand pack in these wells extended approximately 5 feet above the screen. The wells were 4- inch-diameter casing installed in a 10-inch-diameter boring. Well construction details are summarized in Table 2. With respect to groundwater gradient and flow direction, monitoring wells SRK-MWI and SRK- MW2 have, at various times during the monitoring period (1991 to the present), ranged between upgradient and crossgradient of the source. SRK-MW3 has generally ranged between ' crossgradient and upgradient of the source. ' In April 1996, Park installed two monitoring wells on the Union Pacific Railroad property immediately adjacent and south of the site. The wells are designated as MW-7-P and MW-8-P. Their respective locations are illustrated on the site pian(Figure 2). Soil samples collected during ' the installation of these wells were analyzed at the depths of 10, 15, and 20 feet bgs. Elevated hydrocarbon concentrations (101 mg/kg TPHg) were detected in the soil sample collected from OST 701-1-2.cap Page 5