SITE INFORMATION AND CORRESPONDENCE

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Ms. Kerry Heckman - 2 - 1 June 2006 2211 N. Wilson Way, Stockton, San Joaquin County The depth to water varied from 42.84 to 44.64 feet below the top of the well casings. The groundwater gradient varied from 0.01feet/feet (ft/ft) to 0.002 ft/ft. The downgradient groundwater flow direction in HU-1/2 (40-100 ft bgs) and HU-3/4 (100-150 ft bgs) varied in all directions due to mounding in the SVE extraction wells area, and in an apparent easterly and southerly direction outside of the influence of the SVE extraction wells. Deeper zone HU-5/6 (150-250 ft bgs) groundwater flowed in an apparent easterly and southerly direction. Comments: 1) Report: The lack of notice to Regional Board staff of SVE/AS treatment system stoppage and the ensuing 44-day hiatus of the SVE/AS treatment does not comply with MRP No. R5-2005-0827. The MRP requires notice to Regional Board staff within 48 hours of shutdown of the remediation system, and provides a schedule for required sampling and analyses for each quarter. I discussed the issue of notification with AGE in a meeting on 12 May 2006 and received an emailed letter of explanation (attached) on 15 May 2006. The email explanation stated that issues with PG&E over dual billing from two electrical meters for the SVE system and modifications to provide one electrical meter were the reason for the delay. AGE stated that all future unscheduled stoppages of the treatment system would be noticed promptly to Regional Board staff within 48 hours of the stoppage, per MRP No. R5-2005-0827. Note that dual billing of charges to the State Water Resources Control Board UST Cleanup Fund is prohibited. %Alk;i,. 4-ke 1AI 1,.,1.,,•, � 4r♦roc L- me-%c+ of+k,= iccl Inc rainfarl to n�nna iniartinn G� VVLJ1AJ 1C711. V Vl111e U lc VVVII-1r. 1C111 CAUUI lrOOII Iv' a Iv vv...vv •.. ..••-• ••• ----•-••, there are some elements missing from the Workplan. In future workplans for ISCO remediation (including ozone injection) please review and incorporate applicable guidance from the Interstate Technology & Regulatory Council (a workgroup that is recognized by the State of California), which may be downloaded from the Internet at http•//www.itrcweb.org/qd ISCO.asp. 3) The BST section of the Workplan is approved at this time with the modifications listed below. A). Pages 8 and 9 — The iisi of BST analyses are riot complete. Add broi mide and bromate to the list of general minerals. Analyze all constituents in a manner to provide a degradation rate if these by-products of ozone injection are detected. Note that detection limits should be low enough to compare results to the Water Quality Objectives, which can be downloaded from the website in the header of this letter. B). Total Organic Carbon (TOC) and Soil Oxidation Demand (SOD) analyses are necessary components for an ISCO remediation design. Add TOC and SOD to the list of BST analyses. C). The BST does not include a separate test to determine whether volatilization alone (air sparging) would significantly reduce the constituents of concern (COCs) at a cost savings over ozone injection. Include a BST lab analysis simulating the use of air sparging alone for petroleum hydrocarbon COCs. D). Provide an evaluation in the Geochemical Evaluation of any effects noted in the BST that would degrade water quality or that might affect aquifer characteristics when scaled up to the OPS. E). Page 10, the Geochemical Evaluation should be reviewed and signed by a geochemist or chemist familiar with soil chemistry.