SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

F, ZNA Working To Restore Nature The San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) requested additional work be performed to address residual hydrocarbon contaminated soils at the site. FIELD ACTIVITIES The work described below was performed to remove the remaining impacted soil in the vicinity of the former underground storage tanks. All field work was performed under the supervision of RESNA personnel in accordance with the Quality Assurance/Quality Control Pian (Attachment 1) and a site specific Health and Safety Plan on file with PHS/EHD. Soil Excavation, Sampling and Analytical Results 4n January 6,7, and 10, 1994, potential petroleum hydrocarbon contaminated soil was excavated from the vicinity of the former underground fuel storage tanks to a maximum depth of 30 feet below ground surface. The extent of the excavation is depicted on Plate 3. Excavation was conducted by Goins Environmental Construction (Lie. #674281) under the direct supervision of a RESNA geologist. Excavation activities were observed and approved by Ms. Pamela Violet of PHS/EHD. A Photoionization Detector (PID) calibrated to an isobutylene standard and visual and olfactory methods were utilized during excavation to assist in evaluating the lateral and vertical extent of soil impaction. PID readings ranging from 0 to 150 ppm and petroleum hydrocarbon odor indicated that residual petroleum hydrocarbon impacted soils existed in a limited centralized area beneath the area of the former central unleaded gasoline tank between approximately 13 to 29 feet below grade. Excavation continued until field evidence indicated contamination was no longer present. Following excavation, confirmation samples were collected under the direction of Ms. Violet. a total of 4 sidewall and 4 floor samples were collected from the pit. The soil sampling locations are depicted on Plate 3. Samples were collected from the excavator's bucket three inches below the surface of the soil. The samples were collected into prewashed brass liners. Each liner was sealed with Teflon sheets and plastic caps, sealed in air-tight bags, and preserved on ice pending shipment to Sequoia Analytical (DHS Cert. #1210) in Redwood City, California. Sample descriptions are included in Attachment 2. Soil samples were transported under chain- of-custody to the laboratory for analysis of benzene, toluene, ethylbenzene, and xylenes (BTEX), and TPHg by EPA methods 8020 and modified 8015, respectively. Expedited laboratory analyses of soil samples collected from the excavation pit detected no hydrocarbon analytes with the exception of one sample (sample SB/S-NCB-30') collected from the bottom of the 30 foot deep excavation. This sample contained trace levels of benzene (0.057 1500531REP0RTSIEXCV-294.FNL 2