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• CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD CENTRAL VALLEY REGION MONITORING AND REPORTING PROGRAM NO. 5-01-S77 FOR PACIFIC GAS AND ELECTRIC COMPANY LATHROP NATURAL GAS DEHYDRATOR STATION SAN JOAQUIN COUNTY Pacific Gas and Electric Company's (PG&E) California Gas Transmission Division has operated a natural gas gathering system since the 1940s. The gas gathering system receives wellhead gas from nearby natural gas producers. PG&E then treats the natural gas prior to delivering it into the gas transmission system. The treatment processes may include dehydration, odorization, and compression. The Lathrop Dehydrator Station is at Undine and Willow Glemz Roads in the San Joaquin Delta area. Soil and groundwater are contaminated with benzene, toluene, ethylbenzene and xylene, and total petroleum hydrocarbons (TPH). Groundwater is found between six to nine feet below ground surface and contains up to 24 µg/1 of benzene and 120,000 pg/l of TPH as diesel. This Monitoring and Reporting Program (MRP) is issued pursuant to Section 13267 of the California Water Code and is designed to delineate groundwater contaminant plumes and determine whether remediation efforts are effective. The Discharger shall not implement any changes to this MRP unless and until a revised MRP is issued by the Executive Officer. This MRP replaces the requirements listed in revised MRP No. 96-807, which was issued on 29 September 1997. Prior to construction of any groundwater monitoring or extraction wells, the Discharger shall submit plans and specifications to the Board for review and approval. Once installed, all new wells shall be added to the monitoring program and shall be sampled and analyzed according to the schedule below. GROUNDWATER MONITORING As shown on Figure 1, there are 12 monitoring wells. The groundwater monitoring program is for MW-1 through MW-10, MW-11A and 11B, and any wells installed subsequent to the issuance of this MRP. Monitoring wells with free phase petroleum product or visible sheen shall be monitored for product thickness and depth to water only. When free phase petroleum product is present, the monitoring reports shall include the employed remedial strategy for its removal. If PG&E begins extracting groundwater as part of a remedial action plan, then the monitoring reports shall also include the volume of groundwater extracted. Sample collection and analysis shall follow standard EPA protocol.