SITE INFORMATION AND CORRESPONDENCE

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i PUBLIC HEALTH SERVILES SAN JOAQUIN COUNTY z -F ENVIRONMENTAL HEALTH DIVISION Karen Furst, M.D., M.P.H., Health Officerp 304 East Weber Avenue, Third Floor • Stockton, CA 9520 � FORii\ 209/468-3420 C 0or DALE STEELE JUL 2 4 1997 CALTRANS PO BOX 2048 STOCKTON CA 95201 Re: Caltrans Stockton Maintenance Facility Site Code: 1018 1604 South "B" Street, Stockton CA 95205 San Joaquin County, Public Health Services, Environmental Health Division (PHS/EHD) has completed review of the following reports: Groundwater Monitoring Report - Third Quarter 1996 dated August 1996; Groundwater Monitoring Report - Fourth Quarter 1996 dated November 1996; Problem Assessment Report and Corrective Action Plan dated December 1996. PHS/EHD has prepared the following comments for your consideration and response. Groundwater monitoring reports must be submitted quarterly so that PHS/EHD can evaluate and respond to information that may reflect site changes. As PHS/EHD has indicated on a number of occasions, PHS/EHD must be notified prior to any field activity. PHS/EHD was notified of the May 1997 groundwater sampling event, the first sampling event of 1997. The resultant quarterly report should be submitted immediately. The analytical results of the July 2 and 3, 1996 and October 23 and 24, 1996 groundwater sampling events continued to evidence significant concentrations of petroleum hydrocarbon contaminants in the groundwater. Please note that Table 1 of the "Fourth Quarter 1996" report erroneously indicated that 3.6 ppb toluene was detected in the sample collected from MW1 1, when in fact 3.8 ppb toluene was detected according to the Advanced Technology Laboratories report which was included. The groundwater samples collected from VW2 on October 23, 1996 were analyzed for methyl tertiary butyi ether (MTBE) using EPA Method 8020 and 8260, confirming the presence of MTBE at 14 ppb rather than 43 or 36 ppb as had EPA Method 8020. PHS/EHD has prepared a well completion summary in attachment for your information so that possible dilution affects associated with the groundwater level increases may be evaluated. It is generally thought that samples are diluted when collected from wells with submerged screened intervals or from wells with screens of greater length than 20 feet within groundwater. The corrective action plan (CAP) which was submitted failed to fulfill the criteria stated in the California Code of Regulations, Title 23, Division 3, Chapter 16 12725(d). The CAP failed to include the potential migration in water, soil, and air of the contaminants. The CAP failed to evaluate alternatives to restore and protect the potential beneficial uses of the groundwater that have been affected by the release. The CAP failed to include cleanup levels for groundwater and to propose at least two alternative to achieve numerical objectives which have been designated in the Central Valley Regional Water Quality Control Plan. The CAP failed to demonstrate that the selected alternative, vapor extraction was the most cost effective alternative and to propose how its effectiveness will be adequately monitored. The CAP stated that approximately 1,500 cubic yards of soil was impacted. PHS/EHD questions this estimate since the vertical extent of the contamination has not been determined, nor has the distribution of petroleum hydrocarbons within the soil plume been characterized. A Division of San Joaquin County Health Care Services