SITE INFORMATION AND CORRESPONDENCE

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�-� RECEIVE® JUL 12 2012 \� M.+n Ronuiouer Water Boards ,IJ•,.IJ,JJ,:L., , ,.Nf„1,,,,,,J ENVIRONMENTAL HEALTH - - PERMIT/SERVICES - - - Central Valley Regional Water Quality Control Board Lo, I� r1{ <J 10 July 2012 Leon Marineau Chris L'Orange Cascades Inc. Drinker Biddle & Reath LLP 471 Marie-Victorin 50 Frembnt Street Kingsey Falls, Quebec, Canada JOA 180 San Francisco, CA 94105 DOCUMENT REVIEW, DUPACO, INC., 800 WEST CHURCH STREET, STOCKTON, SAN JOAQUIN COUNTY, REGIONAL BOARD CASE 391187 1 reviewed the Investigation Work Plan (Workplan) received 28 June 2012 from Geosyntec Consultants, the consultant for Dopaco, Inc. The Workplan proposed an engineering survey to establish physical boundaries for the Site, an initial investigation to determine the distribution of toluene in soil and groundwater as a prelude to installing four groundwater monitoring wells, sampling of the monitoring wells for extent of toluene over time, and submittal of a report of the investigation with recommendations for follow- up work and a groundwater monitoring program. Site boundaries as established in the court settlement agreement will surveyed by a California-licensed surveyor prior to the initial investigation by cone penetrometer testing (CPT) soil and groundwater sampling. A membrane interface probe (MIP) screening will run conjunctively with the CPT investigation. Initially twelve (12) undesignated CPT borings will be advanced near and around the former underground storage tanks (USTs) to a minimum target depth of 40' below ground surface.(bgs) to determine soil and engineering characteristics, and to determine up to two (2) grab groundwater sampling locations per boring. Up to three (3) additional CPTs may be advanced near the USTs if groundwater concentrations are substantially greater than prior investigations results. The MIP sensors attached to the CPT will include a photoionization detector (PID), and electron capture detector (ECD) , and a flame ionization detector (FID) to give a depth discreet distribution of volatile organic compounds (VOCs), including toluene. Initial MIP target depth will correspond to the CPT's target 40' bgs, with final MIP depths determined by PID, ECD and FID readings until a baseline response is detected. Direct correlations to VOCs concentrations in soil and groundwater are not possible with MIP; however, relative distribution of VOCs is possible when MIP is calibrated with prepared toluene standards to estimated detector response relative to known concentrations from previous investigations. Grab groundwater sample results will confirm MIP results by USEPA Method 8260B for VOCs. SU). P E nr,. I �.,..._ G. ” f. fiGC;. _ ,.., ,.r.f• 4J