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f and groundwater analytical data is contained in Interim Status Report, Phase Illnvestigation, by WHF.
<br /> Based on the initial data, the vertical and lateral limits of contamination were not sufficiently defined.
<br /> WHY proposed the installation of four (4) additional monitor wells (MW-5 through MW4) to fully
<br /> characterize the groundwater plume. The PHS/EHD granted approval of the additional investigation on
<br /> January 19, 1994. Between March 9 and 11, 1994, WHY installed MW-5 through MW4. Moderate
<br /> concentrations of gasoline were detected in the soil from MW-6 at 50 and 55 feet bgs and from MW-7 at 50
<br /> feet bgs. Low to elevated concentrations of TPH-G and BTEX were detected in groundwater samples
<br /> collected from MW-6, MW-7, and MW-8. A summay of the soil and groundwater analytical data is
<br /> contained in Phase U Site Characterization, by WHF. The wells were surveyed and gradient calculations
<br /> indicated that a groundwater mound existed beneath the site indicating that recharge or leakage into the
<br /> groundwater in the vicinity ofMW- I and MW-2 was occurring. Three potential sources of recharge were
<br /> identified: 1 ) the car wash water recycling pit system under the building, 2) a leaking or broken sewer line
<br /> that crosses the area, and 3) a leaking water supply line. An MBAS (Methyl Blue Active Surfactants) test
<br /> was conducted on groundwater samples collected at the site in July, 1994, to investigate the presence of
<br /> detergents. MBAS was not detected in the samples.
<br /> Aquifer testing (24-hour pump test) was conducted at the site by WHF on December 22 and 23, 1994.
<br /> MW- 1 was used as a pumping well, and MW-4, MW-6, MW-7, and MW-8 were used as observation wells.
<br /> The results indicated an optimum pumping rate of 5 gpm with an effective radius of 140 feet. Aquifer
<br /> permeability was estimated at 126 gpd/ft2.
<br /> Quarterly groundwater monitoring was conducted at the site by WHF from March 1994 through June, 1995.
<br /> Historical groundwater analytical data indicated elevated concentrations of TPH-G and BTEX in MW- 1 ,
<br /> MW-2, MW-6, and MW-7. Low to trace concentrations of TPH-G and BTEX were detected in MW-3,
<br /> MW-4, MW-5 and MW-8 . Condor has been conducting quarterly groundwater monitoring at the site since
<br /> August 1996 . Analysis of groundwater samples collected from selected SVE wells (SVE-1, 2, 3 , 5, 7, 8,
<br /> and 9) indicate that high concentrations of TPH-G, BTEX, and MTBE are present in the former location of
<br /> the fuel dispenser islands. The groundwater table has risen approximately 15 feet since quarterly
<br /> monitoring of all eight site monitor wells began in March 1994.
<br /> A site investigation was conducted by Condor Earth Technologies, Inc. (Condor) on July 31 , 1996, at the
<br /> Canepas Car Wash facility. The investigation included a review of existing investigative reports and an
<br /> evaluation of the existing SVE system located at tlne site. The fieldwork was conducted in accordance with
<br /> Condor's proposal for SVE evaluation, dated April 8, 1996, and the addendum to the proposal, dated May 2,
<br /> 1996. The report was titled Soil Vapor Extraction (SVE) System Evaluation, and dated September 23, 1996.
<br /> Condor calculated that, based on the soil analytical data available for the site, the volume of hydrocarbons
<br /> present in the soil beneath the site is estimated at approximately 13,000 pounds or 2,050-gallons (634
<br /> lbs/gal). Due to unknown variations in the Iithology and contaminant concentrations, the actual volume of
<br /> hydrocarbon beneath the site may vary by an order of magnitude or more from the estimate.
<br /> Based on the results of the SVE system evaluation and site background, Condor recommended that
<br /> operation of the ICU be suspended since the system did not appear to meet APCD permit conditions (i.e.,
<br /> 95% destruction efficiency). Condor further recommended that a 150 SCFM catalytic oxidation unit (CAT-
<br /> OX) be installed at the site to extract and treat the gasoline contamination in the vadose zone. It was
<br /> determined that the configuration of the existing SVE wells appeared to be sufficient to remove a majority
<br /> of the remaining gasoline contaminants in the vadose zone.
<br /> III 2
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