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A S S O C I A T E S I N C of petroleum hydrocarbons Quarterly monitoring and sampling of the groundwater monitoring wells on site was initiated in October 1991 In September 1993, RESNA supervised the advancement of a boring that was subsequently completed as groundwater monitoring well MW-6 (Figure 2) Soil encountered during drilling was monitored for organic vapors using a PID No evidence of soil contamination was noted Analytical results of groundwater samples indicated only toluene was detected, at a concentration of 38 micrograms per liter (ug/1) In August 1995, due to infiltration of organic debris in groundwater monitoring well MW-4, Smith Environmental Technology Corporation destroyed well MW-4 by overdrilling the PVC casing and sandpack with 8-inch diameter hollow-stem augers Smith also supervised the advancement of a boring for groundwater well MW-4R to replace well MW-4 (Figure 2) Analytical results of the soil samples collected from the boring for monitoring well MW-4R indicated that petroleum hydrocarbons were detected only in the sample collected from 6 5 feet bgs In January and February 1996, SECOR advanced ten soil borings at the site Soil samples and grab groundwater samples were collected from the borings No total petroleum hydrocarbons as gasoline (TPHg), total petroleum hydrocarbons as diesel (TPHd), total petroleum hydrocarbons as motor oil (TPHmo), methyl tertiary butyl ether (MTBE), or benzene, toluene, ethylbenzene, or total xylenes (BTEX) constituents were detected above reported laboratory detection limits in any of the soil samples analyzed with the exception of soil boring SB2 Low concentrations of benzene, toluene, and total xylenes were detected in the soil sample collected from SB2 at 3 5 feet bgs Trace amounts of free product were observed in the water samples obtained from borings SB 1, S132, and SB26 Groundwater samples collected from borings SB26, located between the restaurant and store buildings, and SB1 and SB2, located between the levee and the store, contained elevated concentrations of petroleum hydrocarbons MTBE was detected in the water sample collected from boring SB26 at 130 ug/1 The water samples from SB 1 and SB2 were not analyzed for MTBE In July and August 1999, ATC advanced ten soil borings (Figure 2) to evaluate the extent of petroleum hydrocarbons and trace amounts of free product detected by SECOR Soil borings advanced along the levee, hydraulically upgradient and southwest of the location of the former USTs and the current AST location, contained elevated concentrations of TPHg, TPHd, and MTBE The extent of impacted soil was defined and generally extended along the backside of the levee, west of the store The areal extent was approximately 200 feet in length and 65 feet in width and was limited to depths between 5 and 15 feet bgs Additionally, MTBE impacted soil extended eastward, between the store and office building The groundwater plume was located generally along the eastside of the levee, west of the store Concentrations were highest in the boring adjacent to the former and current product lines The extent of TPHg in groundwater was not fully defined to the west and south but samples indicated that the borings in those directions were near the edge of the plume In April 2001, ATC drilled one soil boring to 30 feet bgs and converted the boring into groundwater monitoring well MW-7 (Figure 2) Well MW-7 is located between the levee and the on-site store where elevated petroleum hydrocarbons were detected during the previous investigations TPHg, benzene, ethyl benzene, and total xylenes were detected at 60, 1, and 2 9 milligrams per kilogram (mg/kg), respectively in the soil sample collected at 5 feet bgs MTBE was detected at concentrations of 56 and 41 mg/kg in the soil samples collected at 5 and 10 feet bgs, respectively MTBE was detected in water samples w 1625141reportslstatusreport doc 2