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BUILDING 16 FORMER USTS GROUND WATER INVESTIGATION WORK PLAN PORT WEST COMPLEX,ROUGH AND READY ISLAND,PORT OF STOCKTON Based on observations to be made in the field, additional borings C15 through C19 may be advanced to assess ground water quality approximately 500 feet downgradient from the Site (Figure 18). 3.2.1 Boring Advancement The borings will be advanced using hydraulic direct push equipment to approximately 20 feet bgs, which is anticipated to intercept ground water contained within the native silts and clays. In addition, borings C1, C9, and C10 will be advanced to approximately 35 feet. All drilling equipment will be decontaminated between each sampling location. 3.2.2 Soil Sampling In the borings, soil samples will be collected continuously and described with regard to soil type, relative moisture, and color in accordance with the Unified Soil Classification System. In addition, possible volatile organic compounds emanating from the soil samples collected near the former USTS will be screened by placing the soil sample in a sealable plastic bag (e.g., zip- lock) and using a photo-ionization detector (PID) to measure the headspace in the bag. Soil samples collected from the borings are not proposed for laboratory analysis. 3.2.3 Ground Water Sampling and Analysis Grab ground water samples will be collected from two depths within each of the borings. The first sample will be collected from within the shallow sandy fill materials by stopping the boring at the approximate base of the sandy fill. The second sample will be collected between 15 feet and 20 feet bgs, from within the underlying silts and clays. In the event that shallow sandy fill materials are not encountered, the boring will simply continue to approximately 20 feet and a grab ground water sample will be collected. Deeper grab ground water samples will be collected between 30 feet and 35 feet bgs from borings C1, C9, and C10. In all cases, coarser grained sandy lenses within the silts and clays will be preferentially targeted for sampling ground water. Upon reaching the desired depth in the boring, 5 feet of slotted PVC screen will be lowered into the boring to serve as temporary well casing. Ground water grab samples will be collected within the PVC screen using a bailer constructed of Teflon, PVC, or stainless steel. The ground water samples will be gently conveyed into laboratory-supplied containers for the appropriate type of analyses. The ground water sample containers will be sealed, labeled, and placed in a cooler containing ice immediately after collection. The samples will be transport to a state- certified laboratory under standard chain-of-custody protocols. Environmental Risk Services,Corp.