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PROJECT DESCRIPTION McDONALD ISLAND GAS STORAGE FIELD ENVIRONMENTAL COMPLIANCE PROJECT As PG&E' s largest gas storage field, McDonald Island is capable of supplying up to 369 of the systems peak day demand require- ment. The field consists of three injection/extraction stations : McDonald, Whiskey Slough and Turner Cut. During the natural gas extraction process , production liquids are separated from the natural gas and, until recently, were dis- posed of in unlined evaporation ponds, except for McDonald sta- tion where this waste water was stored in tanks for off-site dis- posal . The ponds were also used for the disposal of rainwater runoff from the processing and control platforms at Whiskey Slough and Turner Cut which may contain inseparable chemical wastes , oil and grease . These ponds were operated under Waste Discharge Requirements issued by the California Regional Water Quality Control Board -Central Valley Region (CRWQCB) , Order Num- ber 74-372 . The typical volume of production liquids and rain water, run-off is approximately 400 , 000 gallons per year, most of it generated during gas withdrawal and the rainy season. The peak volume is usually achieved during the month of January. Because of recent changes in the law regarding disposal of such wastes , the evaporation ponds no longer meet the design require- ments which were established by Subchapter 15, Title 23 of the California Administrative Code. The CRWQCB inspected the ponds in early 1986 and, due to design and operation deficiencies, ordered PG&E to stop discharging this waste water into the ponds . Since that time, two existing 10 , 000 gallon storage tanks at Whiskey Slough and Turner Cut have been used as a temporary means to col- lect the production fluids and rain water run-off together for off-site disposal . Concurrently, studies have been conducted for Whiskey Slough and Turner Cut to determine and evaluate alterna- tives to the existing evaporation ponds which would be acceptable to the CRWQCB. Based on these studies , the most effective solution was to pro- vide separate and permanent collection/storage tank systems for the production fluids and rain water run-off and to transport the wastewater off-site for disposal in approved injection wells . The two existing tanks at Whiskey Slough station and Turner Cut sta- tion will continue to store production fluids for transport and off-site disposal . The project for which development plan approval is sought consists of the installation of three 11 , 000 gallon storage tanks which will store the rain water run-off water collected from the platforms and the truck loading facility sump. Containment around the tanks will consist of a concrete slab and dike in case of an accidental spill . The tanks will include level indicators and high level alarms . The truck loading facility will be modified to accommodate the new piping. All proposed facili-