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S E C ® R
<br /> Mr Michael Infurna— SJCEHD
<br /> January 29, 2003
<br /> Page 2
<br /> event conducted in December 1998 revealed all four wells contained reportable concentrations of
<br /> dissolved BTEX, TPHg, and methyl-tert-butyl ether (MtBE) (Table 3) No reportable concentrations
<br /> of tertiary butanol (TBA), diisopropyl ether (DIPE), ethyl-tert-butyl ether (EtBE), and te rt-amyl-m ethyl
<br /> ether (TAME) were detected in 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) and
<br /> two continuous core borings (SB-1 and S13-2, Table 2) Soil samples collected from GP-2, SB-1, and
<br /> 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 site
<br /> MW-5, MW-6, MW-7, MW-8, and MW-9 (Table 2) Sod samples collected during monitoring well
<br /> installation did not contain reportable concentrations of BTEX, TPHg, or MtBE (Table 1) Sod
<br /> 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 samples
<br /> collected from V-1, V-2, V-3, and AS-1 contained elevated concentrations of BTEX, TPHg, and MtBE
<br /> (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 Based
<br /> on analytical results of water samples collected from the three CPT borings, vertical distribution of
<br /> gasoline range petroleum hydrocarbons dissolved in groundwater between the former UST pit and
<br /> DW-3 and DW-4, and east of the site across South Santa Fe Road, has been defined
<br /> Sod Vapor Extraction & Air Sparge Feasibility Testing
<br /> In October 2000, SECOR conducted a two-day sod 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 1 9 pounds,
<br /> respectively Based on the induced vacuum response (0 2 inches of water at 40 feet) and the slight
<br /> rise in groundwater levels in off setting monitoring wells, the SVE radius of influence was estimated
<br /> to be 40 feet Although the air sparging did not result in an immediate increase in TPHg vapor
<br /> concentrations, the increase in dissolved oxygen concentration and slight rise in the water table in
<br /> offsetting wells indicates a radius of influence of approximately 30 feet Details related to the
<br /> feasibility test are presented in SECOR's Problem Assessment Report, dated November 8, 2000
<br /> a
<br /> Final Remediation Plan
<br /> SECOR submitted a Final Remediation Plan (FRP) on March 2, 2001, which was approved by the
<br /> California Regional Water Quality Control Board, Central Valley Region, (RWQCB) in a letter dated
<br /> March 26, 2001
<br /> Due to an expansion of the remedial objectives, SECOR submitted a Work Plan for Remedial
<br /> Approach and Well Installation dated May 2, 2002 The RWQCB approved the work plan in a letter
<br /> Riverbank-02 40 doc SECOR intemational Incorporated
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