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<br /> Affairs Publication Number 4699, dated February 2000) The fraction of organic carbon used
<br /> (0 0025) was the mean concentration for site soils in the Los Angeles area as reported by the
<br /> RWQCB in their Intenm Site Assessment & Cleanup Guidebook dated May 1996
<br /> The input parameters and model results for years 1, 2, 3, 4, 5, 10, 20, 28, 29, 40, 50, 60, 70, 80,
<br /> 90, 100, 110, 120, 130, 140, 150, 155, 156, 170, 180, 190, 200, 210, 220, 229, 230, 231, 240,
<br /> 250, 260, 264, and 265 are included 1n Appendix G As demonstrated by the output included in
<br />' Appendix G, the contaminant plume with no degradation arrives at the receptor (nearest
<br /> groundwater production well, 1,500 feet downgradient) at approximately year 156 A maximum
<br /> concentration of MTBE is observed at this receptor well at year 230 (0 263 mg/L), which is
<br />' above the maximum contaminant level (MCL) of 0 013 mg/1 At year 29, with no degradation,
<br /> the source area MTBE concentrations would be below the MCL of 0 013 mg/1 The 1st Order
<br /> Decay model results in an MTBE plume with a maximum length of 600 feet at approximately
<br /> year 100 Based on this simulation, the MTBE plume would impact the receptor well at years
<br /> 156 through 264 with no degradation and would never impact the well with the 1st Order Decay
<br /> model
<br />' The 1 st Order Decay simulation appears to be closest in agreement with actual observed
<br /> groundwater conditions, and is therefore interpreted to most accurately simulate actual site
<br />' conditions and MTBE groundwater transport at the site As demonstrated in the simulations, the
<br /> MTBE plume would never reach the receptor well, and would create a plume with a maximum
<br /> length of 600 feet at year 100
<br /> 9 0 SUMMARY OF REMEDIATION ACTIVITIES
<br /> From 1993 through the present, numerous remedial activities have been performed to reduce the
<br /> contamination levels in soil and groundwater beneath the site The following 1s a summary of
<br />' remedial activities that have occurred at the site
<br /> 9.1 Removal by Soil Excavation
<br />' On October 13, 1994, Thrifty removed the five (5) former USTs and in November 1994 replaced
<br /> them with new tanks in the northeast corner of the site In conjunction with UST
<br />' removal/replacement activities, a total of 718 09 tons of hydrocarbon-impacted soil were
<br /> removed from the site on November 17 and 18, 1994, and transported to Forward Inc Landfill in
<br /> Manteca, California, for disposal The total of 718 tons is approximately 1,436,000 pounds of
<br /> soil Given an average TPHg level of approximately 453 mg/Kg, which is derived from the
<br /> average concentration of soil samples collected from the stockpiled soil, approximately 651
<br /> pounds of hydrocarbons were removed during this activity
<br /> 9.2 Free Product Removal
<br />' In June 1993, liquid phase hydrocarbon (LPH) was detected in well MW-5 In 1993, thickness
<br /> of the LPH ranged from 0 4 to 1 78 feet Earth Management Corporation, on behalf of Thnfty,
<br /> removed a total of 3 15 gallons of LPH though weekly hand bailing efforts As of April 1994,
<br /> thickness of LPH ranged from a sheen to 0 02 feet From May 1994 on, no LPH was detected in
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