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�, ;, a � i.. r TSY' .lulian Munoz !S5 Mssoc+aTES February 10, 1988 Z after the tanks were removed. Laboratory analyses indicated that the pea gravel contained hydrocarbon concentrations exceeding California Regional Water Quality Control Board - Central Valley Region cflQotion�)unt•.reated• To allowing the backfill material to remain in the treat this pea gravel WA proposed its excavation and aeration on site as described below. iAuKFILL EXCAVATION ravel, standing water was encountered in Prior to the removal of the pea g royal the open excavation at about 6 feet below ground surface• With thUtipro' s, of Larry Williams of the City of Stockton Department of Municipal the water was pumped to the sanitary sewer. Since ground water is found at :bout 17 f•�et below ground surface in three adjacent ground water monitoring in the excavation had probably drained into the excavation wells, the water from surface and/or near-surface sources. on 22 and 23 January 1989, a clamstiell crane exu,vatar removed approximately 750 cubic yards of Pea gravel from the excavation. The pea ! gravel was stockyiled an a bermed impermeable polyolifi"i liner spread over '=n he northwest corner of the Safeway fac�oity The unpaved parking area at Cediately covered with plastic sheeting prevent stockpiled pea gravel was imm this material to reduce hydrocarbon infiltration of rainwater. Aeration of concentrations will begin after the rainy season. While removing the backfill a 10-inch diameter water main for the plant red fire sprinkler system and a 14-inch diameter storm drain�ereplpesuntrend along the northern side of the excavation (Figure 1). exposed for 30 to 40 feet. The Pea gravel ex approximately east-west and were P appears to support the lines, and it may extend several feetnortperominute The storm drain was leaking clear water at about 1 gallon pipes. For - This water-ma br. the main source of the water in the excavation. — _ - - _ -ZgPm}. Y fear of desta bilizing the water pipes, no pea gravel was removed from beneath or adjacent to the pipes.