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fbg. TPH-d was also detected in boring B-14/MW-7 at a concentration of 1.5 mg/kg at a depth of 6o fbg, and in boring B-12 at a concentration of 2.2 mg/kg at a depth of 65 fbg. TPH-g was only detected in boring B-17 at concentrations of 0.31 mg/kg at a depth of 50 fbg.All other analytes were below their respective laboratory reporting limits. Soil analytical data from the six borings did not indicate the presence of any significant residual soil impacts with the possible exception of the sample from boring B-17 collected at a depth of 50 fbg. However, this sample was collected at the approximate depth of the soil-groundwater interface and is likely more representative of groundwater conditions at that location. 3.2 Hydrocarbon-Impacted Groundwater 3.2.1 Grab Groundwater Data Results from groundwater grab samples collected from the Site are summarized in Table 3. TPH-d,TPH-g, and benzene were detected in a historic grab groundwater sample collected from boring B-1 on August 2, 1999 by URSGWC at concentrations of 94,000 µg/1, 12,000 µg/l, and 28 µg/l,respectively. URSGWC boring B-1 is located within the perimeter of the 2005 excavation (Figure 2) and the grab groundwater sample was collected from a total depth of 56.5 fbg. The total depth of the 2005 excavation was 8o fbg. During the 2oo8 soil and groundwater investigation,TPH-d was detected in grab groundwater samples collected from five of the six borings. The maximum concentration of TPH-d reported in groundwater was 1,300 µg/L in the grab groundwater sample collected from boring B-12/MW-5. TPH-g was detected in grab groundwater samples from borings B-12/MW-5 and B-17 at concentrations of 73 µg/L and 6o µg/L, respectively. Benzene was detected in grab groundwater samples from borings B-12/MW-5 and B-17 at concentrations of 0.73 µg/L and o.6o µg/L, respectively. MTBE was detected in the grab groundwater sample from boring B-17 at a concentration of 1.9 µg/L. All other analytes were below their respective laboratory reporting limits. 3.2.2 Groundwater Monitoring Data A total of seven monitoring wells were installed and subsequently monitored at the Site (MW-1 through MW-7). The locations of monitoring wells are included on Figure 2. Wells MW-1 through MW-3 were installed in August of 2000,well MW-4 was installed in August 2001, and wells MW-5 through MW-7 were installed 2oo8. Monitoring wells MW-1 through MW-4 were destroyed in June 2005 in preparation for soil excavation activities. Monitoring well boring logs are included in Appendix C. Since monitoring efforts were initiated in September 2000,TPH-g,TPH-d, TPH-mo(motor oil), benzene, 1,2-dichloroethane(DCA), and tertiary butyl alcohol (TBA) have been detected in Site groundwater. However, only TPH-d has been detected consistently at concentrations warranting ongoing monitoring. A semi-annual groundwater monitoring event was performed on July 28, 201o. The scope of work involved gauging and sampling three onsite monitoring wells(MW-5, MW-6, and MW-7). Groundwater samples were analyzed for TPH-d and TPH-mo by EPA Method 8015, and for TPH-g, BTEX, and fuel oxygenates including methyl tertiary butyl ether(MTBE) and TBA by EPA Method 826oB. Analytical results of groundwater sampling are summarized in Table 4. 5 r',