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i I THIRD QUARTER, 2003 • GROUNDWATER MONITORING REPORT JAMAR OIL DISTRIBUTION NOVEMBER 2003 Summary of Previous Investigations In 1995, a 300 gallon waste oil UST and a 500 gallon kerosene UST were excavated and removed from the site. No environmental issues were documented with the removal of these tanks. In December 1998, two 6,000 gallon and one 10,000 gallon gasoline USTs were excavated and removed from the site and replaced with a two compartment 20,000 gallon UST meeting EPA and State of California upgrade requirements. Soil samples taken in conjunction with the tank removal contained detectable concentrations of petroleum hydrocarbons and on January 27, 1999, an Unauthorized Release form was filed with the County. An additional Unauthorized Release was filed with the County on June 11, 1999. In response to a directive from the County, John P. Cummings & Associates (JPCA) conducted a subsurface investigation on September 8-9, 1999, by installing and sampling three monitoring wells (MW-1, MW-2, and MW-3). MW-1, MW-2, and MW-3 were drilled to approximately 78 feet bgs, 74 feet bgs, and 74 feet bgs, respectively and sampled every 5 feet. Groundwater samples were collected from the three wells on September 23, 1999. On August 21, 2000, JPCA did a further subsurface investigation by drilling and sampling one soil j boring (B1) and installing and sampling two additional monitoring wells (MW-4 and MW-5). The soil boring was drilled to approximately 115 feet bgs and sampled every 5 feet. MW-4 and MW-5 were drilled to approximately 75 feet bgs with soil samples collected every 5 feet. Groundwater samples were collected from MW-1, MW-2, MW-3, MW-4 and MW-5 on August 30, 2000. The results of this investigation are documented in JPCA's 2' Phase H Environmental Assessment Report dated October 25, 2000. GHH assumed environmental consulting responsibilities for the site in July 2001. In April 2002, GHH Submitted an Additional Assessment Workplan in response to County directives for additional investigation at the site. The County approved the workplan in a letter dated May 28, 2002. On January 13-16, 2003, three cone penetrometer borings (CPT) and three geoprobe borings were advanced to depths between 104-feet below ground surface (bgs) and 122-feet bgs. General lithology logs generated with a CPT computer program showed little geologic or hydrologic variation between borings. Groundwater samples collected documented that the eastern limit of MTBE- impacted groundwater was not defined. A southeastern limit to MTBE impacted groundwater was defined on the southeast comer of East Main Street and Oro Avenue. 2