SITE INFORMATION AND CORRESPONDENCE

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t l Ms.Mary Serra Page 4 of 6 August 10,2004 concentrations were collected from samples from boring ORC-3B located south of the former sump. Historical groundwater at the Site showed petroleum hydrocarbons in a localized area near the former sump (south of the former reboiler area). Monitoring since May 2002 showed non-detect levels of petroleum hydrocarbons in all of the offsite wells except MW-1 where TPH-d was detected (low concentrations of 1.4 mg/L and 1.0 mg/L). Soil and Groundwater Remediation In October and November 2002,approximately 1,000 cubic yards of TPH-containing soil and 185,000 gallons of water were excavated and removed off site, The excavation was extended to a total of approximately 120 feet east-west by 90 feet north-south to a depth of 16 feet bgs. The excavation was sloped as needed along the east,west and south boundaries to maintain stability of the sidewalls. Interlocking sheet piles were driven along the north boundary of the excavation to maintain the unpaved access road immediately adjacent to the excavation. Shallow groundwater entered the excavation and was pumped into a 20,000-gallon Baker tank,managed and transported to an appropriate disposal facility off site. A total of approximately 185,000 gallons of water was pumped from the excavation. A total of 23 verification samples were collected from the perimeter sidewalk and 9 samples from the bottom of the excavation to confirm that the remedial goals were met(Figure 2). Twenty-six of the thirty-two verification samples indicated non-detect concentrations of TPH and BTEX in soil. Five samples showed trace concentrations of TPH-diesel(below 16 mg/kg)and TPH-gasoline (below 1.5 mg/kg)but were below the cleanup goals. Only one bottom wall sample had TPH-gasoline at 20 mg/kg which was slightly more than the remedial cleanup goal of 10 mg/kg. Table 3 and Figure 2 summarize verification soil sample analytical results. The Remediation Completion Report for the McMullin Dehydrator Station was submitted to the CVRWQCB in January 2003. A replacement well, (MW-2R)was installed immediately north of the excavation in the vicinity of the former well MW-2. Post-Remediation Groundwater Monitoring Post-remediation groundwater monitoring has been performed for MW-1,MW-2R,PZ-1,PZ- 3, and PZ-4 to evaluate the effectiveness of the remediation activities (Figure 3). Analytical results from four continuous quarters of monitoring showed no detectables levels of BTEX j and petroleum hydrocarbons in MW-2R,PZ-1,and PZ-4. Petroleum hydrocarbons and j BTEX were not detected in MW-1 for the last three continuous sampling events (January, May and July 2004). Analytical results from for PZ-3 over four continuous quarters of monitoring showed low concentrations of petroleum hydrocarbons that appear to be fluctuating at low concentrations naturally with time. January and May 2004 concentrations of TPH-d at 95 gg/L and 58 gg/L are below the CVRWQCB Water Quality Goal of 100 gg/L. July 2004 results showed TPH-d at 220 gg/L. f I