COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

WGIK Southwest, Inc. earthen floor of the tank farm near the spill location was analyzed and found to contain 1,700 mg/kg of ammonia as nitrogen (NH3-N) and to have a pH of 9.4. Refer to Figure 3 for a site map depicting the location of the ruptured tank, the flow path, and accumulation area. SITE GEOLOGY AND HYDROGEOLOGY The site is located on the Delta of the San Joaquin River, approximately 2 miles east of the confluence of the San Joaquin and Calaveras Rivers. The subsurface geology consists of a thick sequence of alluvial deposits of late Tertiary to Holocene Age, overlying sedimentary rocks of Cretaceous to Tertiary Age, which in turn overlie crystalline basement rocks (Bartow and Nilsen, 1990). Data from nearby studies within the Port of Stockton area indicate a soil profile to a depth of about 20 feet below ground surface (bgs) consisting of interbedded sands and clays, mostly under reduced conditions(Sierra-Pacific Groundwater Consultants [SPGC], 1994). Lithologic data at an adjacent Port of Stockton site indicate that, in general, the interval from roughly 13 to 23 feet bgs comprises mostly silt, clayey silt, and clay. Silty sand occurs below this interval, which grades downward into loose, dark gray to greenish-gray, poorly-graded sand. This dark gray sand has been observed in nearby soil borings from approximately 30 to 41 feet bgs, the total depth explored in those borings. Data from nearby studies indicate that the current depth to groundwater in the vicinity ranges from about 5 to 10 feet bgs (SPGC, 1998, and EMCON, 1998). Seasonal fluctuations in the water table appear to range from about 3 to 5 feet, with some as much as 6 to 9 feet. Based on nearby studies (SPGC, 1998 & EMCON, 1998) groundwater flow directions in the vicinity appear to be variable, ranging from west northwest to east southeast. Flow direction changes may be due to tidal influences produced by the deep water channel to the north and the San Joaquin River to the west and southwest of the Port of Stockton complex.I According to Port of Stockton monitoring records,the groundwater pH ranges from 7.1 to 7.4. PROPOSED FIELD ACTIVITIES GROUND WATER MONITORING WELL INSTALLATION Three ground water monitoring wells (MW-1, MW-2, and MW-3) are proposed at the locations indicated on Figure 3. The proposed well locations are situated immediately adjacent to the tank farm to the south, west and north of the spill and product accumulation location. The locations are anticipated to provide gradient and delineation data for spilled ammonia hydroxide that may have reached the groundwater. ' Port of Stockton,UST Site No.3,Project Status Report of Groundwater Monitoring and Sampling,4`h Quarter 2002,pages 1 —2. 725.PRI.00 2 August 28, 2003