ARCHIVED REPORTS_XR0006749 CASE 1

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EXECUTIVE SUMMARY The objectives of this investigation were to evaluate the lateral and vertical extent of any impacted sod and/or groundwater associated with the former gasoline fueling system and to identify any sensitive ' receptors (i e , water wells) in the site vicinity To achieve these project objectives, sod and groundwater-grab samples were collected for laboratory analysis from 11 on-site soil borings, and a survey of water wells within a 2,000-foot radius of the site was conducted The nearest municipal water well is located approximately 1,500 feet southwest of the site Immediately east of the site, several residences along Raylow and Mylnar Avenues have shallow domestic water wells On September 2, 8, and 9, 1999, soil and groundwater-grab samples were collected from 11 locations using a Geoprobe One boring (SB-7)was continuously cored to a depth of 40 feet Sods observed ' in the 11 sod borings consisted of massive sand intervals interrupted by alternating thinly-bedded sequences of clay, silt and fine sand mixtures Groundwater levels measured in each of the soil borings ranged from 17 5 to 19 0 feet bgs Groundwater does not appear to be confined and ' recharge was found to be moderately strong A total of 38 soil samples, all 11 of the groundwater-grab samples, and one groundwater sample from the on-site domestic well were analyzed for TPH-as-gasoline, BTEX, MTBE, DIPE, ETBE, TAME, ' TBA, methanol, and ethanol by EPA Method 8260B In soil, the highest concentration of TPH-as-gasoline (280 mg/kg)was detected in the sample collected at 25 feet from SB-3, south of the dispensers Benzene was detected in only one of the 38 sod samples at a low concentration of 0 0056 mg/kg MTBE was detected in 13 of the 38 sod samples at a maximum concentration of 0 25 mg/kg, TBA was detected in six samples at a maximum concentration of 0 031 mg/kg, methanol was detected in one sod sample at 0 42 mg/kg, and ethanol ' was detected in the same one sample at 0 063 mg/kg Vertically, the extent of impacted soil beneath the site was defined in six of the 11 soil borings ' Laterally, the majority of the petroleum hydrocarbon mass in soil is concentrated at approximately 25 feet bgs The concentrations of MTBE detected in the deeper sod samples are present in the northeastern and northern portions of the site ' The groundwater samples from all 11 of the sod borings contained a detectable concentration of at least one of the compounds analyzed Only the groundwater sample collected from the on-site domestic well was free of detectable concentrations of TPH-as-gasoline, BTEX, and/or oxygenates ' In groundwater, the highest concentrations of TPH-as-gasoline (62,000 µg/l) and benzene (230 µg/l) were detected in SB-6, north of the dispensers The highest concentrations of MTBE (9,600 pg/l), ' TBA(180 µg/1), TAME (14 pg/1) and DIPE (3 8 µg/1)were detected in SB-10, northeast of the UST excavation Ethanol was detected groundwater in one sod boring (SB-11) at a concentration of 5 6 µg/I The lateral extent of impacted groundwater is undefined to the west, north and east of the site ' Based on the results of this investigation, Ramage Environmental recommends that a work plan be prepared, which outlines the following course of corrective action 1 Install three on-site groundwater monitoring wells at the site ' 2 Further define the vertical extent of impacted soil and groundwater using a CPT/SimulProbe 4