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• Sample recoveries will be checked by the introduction to the sample of 25 NG of isotopically- labeled surrogate compounds including several deuterated VOCs (acetone, benzene, chloroform, methylene chloride, toluene). Recoveries of these compounds will be measured against acceptability levels of 70 percent for acetone and 75 percent for the remaining deuterated VOCs. The soil gas samples will be tested for methane using a hand-held field instrument with a detection limit no greater than 500 ppm. Samples with elevated levels of these gases will be analyzed by GC/MS for confirmation. Based on discussions with DTSC and as specified in the scope of work, no soil gas samples will be sent to an offsite laboratory for confirmatory analysis,unless offsite methane analyses are needed. 4.2.4.3 Soil Sampling Soil sampling will be conducted using a direct-push technology (DPT) sampling rig mounted on a truck (e.g., Geoprobe) or on an all terrain vehicle. Soil samples will be collected using 2-inch diameter core barrel samplers with dedicated acetate liners or with proper sample sleeves. The DPT sampler will be driven by a hammer. As the core barrel is advanced, soil will be driven into an inner 13/a-inch diameter, 3-foot long acetate sleeve. After being driven 3 feet, the rods will be removed from the borehole. The acetate sleeve containing the soil will then be removed from the sample barrel and the lithology noted. Selected 6-inch sections will then be cut, sealed, and labeled for chemical analysis. If soil samples for VOC analysis are collected based on VOC detections in the soil gas, the soil samples will be field-preserved as soon as practically possible in accordance with the USEPA Region 9 June 23, 1999 "Regional Interim Policy for Determination of VOC Concentrations in Soil and Solid Matrices". All soil samples will be maintained in chilled coolers upon collection. An alternative to using DPT rigs will be the use of a hand auger fitted with a stainless steel bucket. The soil recovery will be placed in pre-cleaned sample containers or sample sleeves using stainless steel trowels. If this method is used, decontamination of the auger and bucket and the stainless steel trowel will be performed between every sample interval. Surface samples will be collected with decontaminated stainless steel trowels directly into sample containers or sample sleeves. During drilling operations, a photo-ionization detector (PID), such as an organic vapor monitor (OVM) model, will be used to monitor the presence and level of organic vapors in the borings and to screen soil samples. These organic vapor readings will be recorded on boring logs prepared during drilling activities. The drilling company, method of drilling, sampler size and type, total depth of the borehole, any attempts to re-sample due to subsurface obstructions, and the logger's name will be noted on each boring log. The following sampling information will be recorded on the boring logs: boring number and location; sample identification numbers; date and time; sample depth; lithologic description in accordance with the Unified Soils Classification System(USCS) including soil type, particle size and distribution, color, and moisture content; sample recovery; description of any evidence of soil contamination (i.e., odor, staining) or subsurface obstructions; and, organic vapor monitor readings. 4.2.4.4 Groundwater Sampling If groundwater is encountered during soil gas drilling, groundwater samples will be taken with the Hydropunch sampling technique (or equivalent). The Hydropunch tool will be opened and groundwater pumped to the surface through nylon tubing. The pH, conductivity, turbidity, and temperature will be Page 18 PAPEA Locke(ord\Work Plan\Locke(ord WP.doc