SITE INFORMATION AND CORRESPONDENCE

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Tony Gonzales Trucking r,.� - 2 - 3 December 2008 1855 Jackson Ave., Escalc_ per Liter (ug/L, SB-1) and 29 ug/L (SB-4). Lead scavengers and fuel oxygenates were not detected in soil or groundwater. Although no monitoring wells were installed during the investigation, the reported regional direction of groundwater flow in Escalon is towards the northwest. Site lithology consists of sand, silt, and clay to 65' bgs, the total depth investigated. The 14 May 2001 Problem Assessment Report (PAR) estimated the remaining mass of TPHg as 4,550 pounds and benzene as 12 pounds. The PAR evaluated three remedial options for cleanup of soil contamination: capping the Site with asphalt to prevent infiltration of water from surface and soil leaching to groundwater, excavation of contaminated soil with off-site disposal in a hazardous waste landfill, and soil vapor extraction (SVE). The PAR concluded that SVE would be the most cost effective and technically feasible alternative, and proposed installation of two vapor wells to 42' bgs and a five-day pilot test. The SVE pilot test proposal was approved by Regional Board staff letter dated 20 June 2001, which required a Final Remediation Plan (FRP), with the SVE pilot test report (Report) by 1 October 2001. However, the FRP and Report were not received by the deadline, resulting in the 3 April 2002 Regional Board staff-issued Notice of Violation for failure to submit documents. On 12 April 2002, the consultant responded that three SVE wells had been installed in November 2001 and the four day SVE test was completed in December 2001. On 22 April 2002, the FRP was submitted, and although the data show a mass removal rate of 1.2 pounds of gasoline per day by SVE during the four day pilot study, the FRP remediation recommendation was to cap the Site with asphalt. Regional Board staff rejected the FRP recommendation as inadequate in a letter dated 1 August 2001 , and requested a fate and transport model (Model) to evaluate leaching potential for the soil contamination to the aquifer. On 18 December 2002 the SWRCB UST CUF pre- approved the cost for the Model; however, work again stopped at the Site. On 1 May 2007, Regional Board staff completed a file review and sent a letter to the Site owners that requested submittal of the approved Model, a status report of Site activities since 2002, and records of current ownership of the Site. On 13 July 2007 a Model was submitted that predicted groundwater would never be impacted by the USTs release. Since nineteen years had passed since the USTs release was discovered, and groundwater was approximately 20' below known soil contamination in 2000, the 22 August 2007 Regional Board staff letter requested a workplan for the installation of one confirmation boring to collect one grab groundwater sample near the USTs, and to also conduct a soil vapor intrusion survey to evaluate potential threats to nearby residents. The workplan was conditionally approved on 13 December 2007. Staff conducted a site inspection on 29 February 2008, observing fieldwork for the soil vapor intrusion survey, and noted the Site was still a residence with a small trucking company in the rear of the property. The 16 April 2008 Groundwater Quality Confirmation and Soil Gas Investigation reported only benzene exceeded the Region 2 Environmental Screening Levels (TIER 1) for soil vapor, and also included a Tier 2 Johnson & Ettinger Model that reported an acceptable 10-7 (one in ten million) cancer risk for the benzene. On 22 April 2008, staff requested a closure report and a list of nearby properties and owners/occupants before proceeding with public participation prior to Site closure. The 15 September 2008 Results of Public Participation and Workplan for Vapor Extraction Well Destruction reported no comments were received during the 45-day public comment period. The 18 September 2008 staff letter approved the Workplan, and on 10 October 2008, staff received an email from the SJCEHD stating that the three SVE wells were properly abandoned. Tony Gonzales Trucking has complied with the requirements of the 13267 Order. Staff concurs that the data show natural attenuation is occurring in soil, that the Model prediction stating