SITE INFORMATION AND CORRESPONDENCE_FILE 2

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Mr. Paul Zumberge Page 2 of 3 Frontier Transportation, Incorporated 15 September 2009 425 Larch Road, Tracy, California 95376 Based on the high concentrations of MTBE detected in groundwater collected from MW-27, the monitoring well located most down gradient of the source, it appears to the EHD that an additional well, or wells, are needed to define the lateral extent of the MTBE plume toward the west. Please submit a work plan to the EHD by 01 December 2009 to complete the down- gradient assessment of your plume. Identify and sample the proximal water supply wells, especially any relatively shallow wells, during your next semiannual monitoring event. Once the hazard posed to the sensitive receptors and the likely behavior of the plume is understood and properly managed, decisions can be made on a technical basis regarding the proper pace of corrective action to best accommodate your financial resources and still properly manage the plume. While there is a concern regarding your LIAR potentially impacting the water supply wells toward the west, which must be addressed right away, your site will most likely require remediation to minimize the hazard posed by your UAR to the wells and human health and it would be wise to be ready to implement the appropriate corrective action when and where needed. The EHD has approved two extensions for submission of a work plan for an ozone bench-scale test and a work plan for performing an eight- to twelve-hour dual-phase extraction pilot test; the EHD suggests your consultant makes a recommendation of which is the more plausible of the two proposed remediation methods and perform the pilot study. The EHD also suggests performing an aquifer pumping test to see if groundwater extraction alone would be an effective remediation method. The August 28'" conference call was followed by an email and telephone call from W&A on 01 September 2009, proposing the operation of a mobile dual-phase extraction unit for eight hours each quarter at the above-subject site as an interim remediation method until the CUF resumes reimbursement. The EHD believes that operating such a unit for only eight hours each quarter would have little, if any, effect on the MTBE plume and cannot approve such a proposal; however a pilot study that includes the operation of a mobile dual-phase extraction unit for an extended period of time (at least seventy-two hours) may prove useful for determining the effectiveness of this remedial method. The EHD suggested a possible cost saving approach for ozone injection evaluation during the 01 September 2009 telephone conversation. A site at the corner of Grant Line Road and Tracy Boulevard, (574 W. Grant Line Road), Tracy, California, has been undergoing ozone injection for approximately five years. The system was put into operation prior to the start of the Central Valley Regional Water Quality Control Board (CVRWQCB) requiring testing for adverse effects to water quality due to ozone injection to evaluate the necessity to issue waste discharge requirements (WDRs); the groundwater at this site has not been analyzed for the generation of chemicals of concern that may necessitate the CVRWQCB to write WDRs. If it can be demonstrated that your site and the site at Tracy Boulevard and Grant Line Road have similar hydrogeological characteristics, the EHD recommends that you request access to their monitoring wells favorably situated to assess the impact of ozone injection to collect groundwater samples. The groundwater samples should be analyzed for the constituents of concern that the CVRWQCB needs to evaluate the need for WDRs. If analytical results indicate that groundwater quality will not be adversely affected, an ozone bench-scale study may not be necessary. This evaluation may save considerable time and expense associated with evaluation of ozone injection.