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Quarterly Momtonng and Samphng Report(Q2 2002) 2
<br /> Ranch Market 23569-Santa Fe Road Riverbank, L Jul 8-2002
<br /> decline in total petroleum hydrocarbon as gasoline (TPHg) concentrations from 4,140 milligrams
<br /> per kilograms (mg/kg) at 20 feet bgs to 6 mg/kg at 30 feet bgs (Table 1) A grab water sample
<br /> was also collected from boring B-1 that contained elevated concentrations of benzene, toluene,
<br /> ethylbenzene, xylenes (BTEX), and TPHg (Table 2)
<br /> In November 1998, Arrowhead Consultants oversaw the installation of four groundwater
<br /> monitoring wells at the site MW-1 in the former tank pit and MW-2, MW-3, and MW-4
<br /> centered around the former tank pit (Figure 2 and Table 2) Soil samples collected during
<br /> monitoring well installation contained reportable concentrations of BTEX and TPHg (Table 1)
<br /> The first monitoring and sampling event conducted in December 1998 revealed all four wells
<br /> contained reportable concentrations of dissolved BTEX, TPHg, and methyl-tent-butyl ether
<br /> (MtBE) (Table 3) No reportable concentrations of tertiary butanol (TBA), MtBE, diisopropyl
<br /> ether(DIPE), ethyl-tert-butyl ether (EtBE), and tert-amyl-methyl ether (TAME) were detected in
<br /> the water samples collected in December 1998
<br /> In July 2000, SECOR oversaw the drilling of four GeoprobeTm soil borings (GP-1 through GP-4)
<br /> and two continuous core borings (SB-1 and SB-2, Table 2) Soil samples collected from GP-2,
<br /> SB-1, and SB-2 contained reportable concentrations of BTEX, MtBE, and TPHg (Table 1)
<br /> In August 2000, SECOR oversaw the installation of five groundwater monitoring wells at the
<br /> site MW-5, MW-6, MW-7, MW-8, and MW-9 (Table 2) Soil samples collected during
<br /> monitoring well installation did not contain reportable concentrations of BTEX, TPHg, or MtBE
<br /> (Table 1) Soil samples were not collected from MW-5 or MW-7
<br /> In September 2000, SECOR oversaw the installation of six soil vapor extraction (SVE) and 1 air
<br /> sparge (AS) well on or adjacent to the former tank pit at the site (Figure 3, Table 2) Soil
<br /> samples collected from V-1, V-2, V-3, and AS-1 contained elevated concentrations of BTEX,
<br /> TPHg, and MtBE (Table 1)
<br /> In October 2001, SECOR oversaw the installation of CPT borings CPT-1, CPT-2, and CPT-3 to
<br /> further define the lithology and vertical distribution of gasoline range petroleum hydrocarbons
<br /> dissolved in groundwater between the former UST pit and DW-3 and DW-4, and east of the site
<br /> across South Santa Fe Road (Figure 2) Water samples collected from the CPT-1 @40' and
<br /> CPT2@35 did not contain BTEX, TPHg, oxygenates, 1,2-DCA , and EDB above the laboratory
<br /> reporting limits Sample CPT-3@35' contained 0 65 micrograms per liter(ug/]L) of toluene
<br /> Based on analytical results of water samples collected from the three CPT borings, vertical
<br /> distribution of gasoline range petroleum hydrocarbons dissolved in groundwater between the
<br /> former UST pit and DW-3 and DW-4, and east of the site across South Santa Fe Road, has been
<br /> defined
<br /> Soil Vapor Extraction &_Air Sparge Feasibility Testing
<br /> . In October 2000, SECOR conducted a two-day soil vapor extraction and air sparge (SVE/AS)
<br /> feasibility test using six SVE wells and one AS well Based on the test results, the total mass of
<br /> TPHg and benzene removed during the SVE/AS feasibility test was 102 pounds and 19 pounds,
<br /> File Ranch Market\Report\Riverbank-02-2Q
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