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i N6vember 6, 1998 Mr. Jeffery C. Wong San Joaquin County Public Health Services Environmental Health Division 304 East Weber Avenue Stockton, CA 95202 0 SECOR International Incorporated PAYMENT VCEIVEQ Nov 101998 SAN JLJAQUIN COUNTY PUBURE: Workplan, Collection of Progress Soil and Groundwater Sam le RONM HEALTH SERVICES p g P SENVIRONMENTAL HEALTH DIVISION PG&E McMullin Gas Dehydrator Station San Joaquin County, California Dear Mr. Wong: PG&E is performing an R&D soil and groundwater remediation project at PG&E's McMullin Gas Dehydrator Station located about 5 miles south of Manteca on Airport Road (Figure 1). To date, this remediation project has included the installation of eight groundwater monitoring wells (MW -1 through MW -8), the injection about 3,000 lbs of Regensis® Oxygen Releasing Compound (ORC) in both the vadose zone and below the water table SECOR International Inc. (SECOR), on behalf of PG&E, presents this work plan for drilling up to 20 soil borings and collecting soil and grab groundwater samples to monitor the progress of the ORC remediation project over the next ± 9 months. The proposed soil borings will be located adjacent to borings ORC-113, ORC-313 and ORC-513 as shown on Figure 2. Several soil borings and groundwater monitoring wells previously installed at the site are also shown on Figure 2. The progress soil borings will be advanced and sampled to a depth of about 14 feet using a Geoprobe rig. Discrete soil samples will be collected at a depths of 6 to 8 feet below grade surface (bgs) and 12 to 14 feet bgs for chemical analytical testing. After each borehole has been advanced to the total depth, 1 -inch diameter PVC well screen and casing will be lowered into the borehole to facilitate the collection of grab groundwater samples. Following the collection of soil and groundwater samples, the well screen and casing will be removed and each borehole will be tremie grouted with neat cement to grade. Detailed drilling and sampling procedures are included in Attachment 2, Field Investigation Methods. The soil and groundwater samples will be transported under chain -of -custody to a state of California certified chemical analytical laboratory. Soil samples will be tested for total petroleum hydrocarbons as gasoline (TPHg) and total extractable petroleum hydrocarbons as kerosene, diesel and motor oil (TPHk, d, and mo) by modified EPA Method 8015, and benzene, toluene, ethylbenzene and xylenes (BTEX) by EPA Method 8020. The groundwater samples will also be submitted for carbon dioxide by EPA method 4500. A description of the quality control/quality assurance procedures that will be followed during this investigation is included in Attachment. 9912 Business Park Drive, Suite 100, Sacramento, CA 95827 (916) 369-1880 (916) 364-1889 FAX www.secorcom