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(YA A S S O C I A T E S I N C On September 24 and October 2, 1996, Smith Technology conducted an additional subsurface investigation at the site. A total of nine soil borings were advanced to depths up to 15 feet below ground surface (bgs). Soil, soil vapor, and groundwater samples were collected from the borings. Analytical results of the soil and groundwater samples indicated the general extent of total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, and xylenes (BTEX), and methyl tertiary butyl ether(MTBE) in soil and groundwater under the site. Analytical results for geochemical parameters in soil and groundwater indicated bioremediation is occurring in the plume of petroleum hydrocarbons in groundwater beneath the site. Analytical results of soil vapor samples indicated the availability of oxygen, carbon dioxide, nitrogen and methane in the vadose zone. Also, results of laboratory geophysical testing on soil samples from the site indicated that the potential receptor on- site, the water supply well, would not be affected by the plume of petroleum hydrocarbons in groundwater within the next 20 years, in the worst case. On March 9, 1999, ATC supervised the installation of three groundwater monitoring wells, MW-4, MW-5, and MW-6 (Figure 2). During installation of the monitoring wells, soil samples were collected from the borings. On March 11, 1999,ATC developed and sampled monitoring wells MW- 4, MW-5, and MW-6. Analytical results of the soil and groundwater samples collected at the site indicated the lateral extent of impacted soil and groundwater had been defined. Refer to ATC's Summary Report Additional Subsurface Investigation, 7675 West Eleventh Street, Tracy, California, dated May 12, 1999,for additional information. Based on historical data and a verbal discussion with Mr. Ron Rowe of EHD, ATC submitted a closure report request dated June 27, 2000. EHD did not formally respond to the report but instead requested that ATC perform another monitoring event. In a letter dated October 2, 2001, Ms. Dot Lofstrom of the EHD requested computer modeling of the groundwater plume be conducted. ATC evaluated contaminant migration potential of affected soil and groundwater at the site using the EPA's BIOSCREEN (v.1.4) software program. The results of the computer modeling indicated the petroleum impacted soil and groundwater at the site do not appear to be an immediate and significant threat to human health or the environment. The computer modeling results are presented in ATC's Addendum to Additional Site Evaluation and Request for No Further Action for Fayette Manufacturing Corporation, dated November 4, 2002. In April 2004, ATC conducted additional investigation activities to evaluate the vertical extent of impacted soil in the vicinity of the former USTs and to evaluate the potential presence of petroleum impacted groundwater between MW4 and MW5. The results of the additional investigation activities indicate the lateral and vertical extent of impacted soil was adequately defined. Petroleum impacted groundwater was identified in the vicinity of the former USTs and between MW4 and MW5. Refer to ATC's Summary Report of Additional Subsurface Investigation, 7675 West Eleventh Street, Tracy, California, dated August 11, 2004, for additional information. s:\17861\reports\wellinstwkpin.doc 2