Laserfiche WebLink
L <br /> Chevron U.S.A. - Page b <br /> 5.0 METHODOLOGY <br /> Drilling was performed utilizing a truck mounted drill rig equipped with <br /> flight hollow-stem auger. A Dames & Moore geologist was present during drilling <br /> to assist in obtaining relatively undisturbed samples of the subsurface <br /> materials, to maintain a log of borings, to field screen samples with a device <br /> capable of detecting volatile organic hydrocarbons as a trace gas, and to make <br /> observations of the site conditions. i <br /> Subsoils were sampled at approximate 5 foot intervals, commencing at an j <br /> i <br /> approximate depth of five feet below the existing grade. Samples were obtained by <br /> means of a California Modified sampler which was lined with brass sleeves. The <br /> sampler was advanced by blows from a 140 pound hammer falling 30 inches. Upon <br /> retrieval, samples were retained for visual observation and interpretation. Those <br /> i <br /> samples retained for chemical analysis were capped with a plastic cap over a <br /> teflon seal, and taped at each end. The samples were placed .into a cooler chest <br /> under proper chain of custody protocol for shipment to the analytical laboratory. <br /> Between sampling attempts, the sampler was dissassembled and washed in a <br /> trisodium phosphate (TSP) solution, rinsed twice with purified water, and <br /> reassembled with brass rings to minimize the potential of spreading contaminants <br /> .; among samples, if any were present. Soils were classified according to the <br /> Unified Soil Classification System (Plate 5) . <br /> The ground water monitoring wells were installed in each soil boring through <br /> the center of the hollow-stem auger. Each monitoring well was constructed using <br /> Ir 4-inch diameter flush-thread pvc schedule 40 well pipe. Screened intervals were <br /> DAMES & MOORE <br />