ARCHIVED REPORTS_XR0003968 - Laserfiche WebLink

Home Browse Search

10 foot sample. Toluene, ethylbenzene, and xylenes were also detected in the 10 foot sample at concentrations of 9.6, 62 and 865 ppm, respectively. TPHg was detected at a concentration of 51 ppm in the 15 foot sample. Toluene, ethylbenzene, and xylenes were also detected in the 15 foot sample at concentrations of 2.4, 4.1, and 25 ppm, respectively. Benzene was not detected in either sample above the laboratory reporting limit. Lead was detected in the 10 and 15 foot samples at concentrations of 15 and 20 ppm, respectively. Following completion of sampling, the excavation was subsequently backfilled to the surface. In May 1991, SEACOR advanced four soil borings in the vicinity of the former USTs to further evaluate the lateral and vertical extent of fuel hydrocarbons in subsurface soil. Chemical testing results for soil samples collected from these borings indicated that gasoline released from the USTs had apparently migrated vertically to a depth of approximately 35 to 40 feet below ground surface. The highest concentration of TPHg detected was 5,100 ppm at a depth of 19 feet below ground surface. Soil sample results also indicated that significant lateral migration of gasoline had not ' occurred. One of the soil borings (MW-1A) located within the extent of the former UST excavation was subsequently converted to a groundwater monitoring well. Initial groundwater sample results revealed the presence of TPHg at a concentration of 1 ppm and BTEX concentrations up to 130 parts per billion (ppb). SEACOR has collected and chemically analyzed groundwater samples from well MW-1A on a quarterly basis since May 1991. TPHg and BTEX concentrations reported in groundwater samples collected from well MW-1A consistently decreased during each subsequent quarter, and TPHg has not been detected above the laboratory reporting limit during the last three consecutive sampling events. In November 1991, SE4COR installed a vapor extraction well (EW-1) approximately 5 feet from existing monitoring well MW-1A(see Figure 2). In early April 1992, SEACOR installed a soil vapor ' extraction system at the Site. The as-built system consists of vapor extraction well EW-1, a trailer- mounted regenerative blower with a 200 cubic feet per minute (CFM) capacity, and two in-line granular activated carbon vapor phase treatment vessels (2,000 pound and 200 pound capacity). The vapor extraction and treatment equipment are all housed within a paved and fenced compound. SEACOR began operating the soil vapor extraction system on April 15, 1992. As of December 31, 1992, an estimated 1070 pounds of gasoline had been removed from the subsurface soils through jvapor extraction. Influent vapor stream concentrations have decreased to below 50 ppm total hydrocarbons (methane equivalent). Based on the decreased influent concentrations, SEACOR recommended drilling a confirmatory soil boring to evaluate hydrocarbon concentrations remaining in subsurface soils. SEACOR shut the vapor extraction system down on January 15, 1993 pending the results of the confirmatory soil sampling described in this report. MARDEE.RPT 50014-003-01 MD04 2 v