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24323 Hwy 99,Acampo,CA 6353233ES411 -9— Each borehole was abandoned/filled with hydrated granular bentonite,and restored to pre-drilling condition via applying patching materials. 4.1.3 Methodology Geophysical Survey On December 6, 2012, a geophysical survey was performed in three areas of the parking lot and area of reported former underground storage tank (UST), and dispensers. The purpose of the survey was to locate and identify, insofar as possible,the existence of any underground storage tanks(USTs),backfilled excavations,piping,conduit, and other buried features that may exist within the survey boundaries. The survey was completed Cruz Brothers, Scotts Valley, California. A combination of electromagnetic induction (EM), magnetometry, and ground penetrating radar(GPR)were applied to the search. A utility locator with line tracing capabilities was also brought to the field and used where risers exist onto which a signal could be impressed and traced. An EM anomaly was detected within the survey boundaries located in the northwestern portion of the property (Figure 3);this anomaly area is between 3-4 feet deep and described as a possible debris pit with metal shard mixed in. An anomaly was detected within the same area(Figure 3);this anomaly area is between 7-8 feet deep. A third anomaly was detected within the survey boundaries located in the southwestern portion of the property; this anomaly is described as possible old oil tank location reportedly removed.The boundaries of these anomalies were marked on the ground cover based on EM and magnetic instruments as GPR penetration. Because of these findings the number and location of proposed borings was modified to better investigate the area of concern. Boring locations were marked in white paint,and Underground Service Alert was notified of the intent to excavate. Soil Boring and Sampling On December 13 and 14, 2012, seventeen (17) borings (B 1 through B 17) were advanced using a truck mounted Geoprobe drilling rig by Soil Probe, Inc., Tulare, California. At each location, the asphalt or surface cover was drilled or cored and the borings were advanced to the proposed target depth. Soil samples were collected from the soil borings with the Geoprobe Large Bore Sampler that measures 2 feet by 1.5 inches capable of recovering discrete samples that measures up to 320 mL in volume contained inside removable liners from specified locations. The liner is a thin-walled tube that fits inside the Bore sample tube and facilitates retrieval of the sample and may be used for storage when applicable. No headspace is present in the tube once the sample is collected. Both ends of soil samples in tubes were then immediately covered with teflon rounds,capped with polyethylene lids,and packed in ice chest(with ice for maintaining 4 Centigrade preservation temperature)to minimize potential volatilization prior to delivery to the laboratory. The collected samples were labeled with the boring number, the sample number (the samples were numbered sequentially with increasing depth from the top for each boring),and the sampling depth. Care was taken throughout to avoid contamination of both the inside and outside of the sample container and its contents. Soil samples were collected for descriptive purposes, and field screened via Photoionization Detector. The sample descriptions(soil characteristics,color,moisture,density/stiffness)were recorded on the field log. Soil boring logs are included in Appendix C. All collected soil samples were preserved in ice chest with ice to keep 4 Centigrade sample preservation temperature until shipment of samples within the same day of sample collection to a State Certified Hazardous Waste Laboratory, for analysis. U.S.Environmental Protection Agency approved chain-of-custody records was kept to track the possession of samples from the time they were taken in the field until the time they were analyzed. ODIC Environmental.