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at ambient air temperatures for approximately 15 minutes. At the end of this time the probe of the PID/FID will be inserted into the container and the sample OVL will be measured and recorded on the boring logs. During drilling operations, a modified split-spoon sampler (sampler) will be used to retrieve soil samples. Pre-cleaned brass sleeves are placed inside the sampler and the sampler is then driven to the desired sampling depth. The sampler is then recovered from inside the boring and the brass sleeves retrieved. The brass sleeves will be used to evaluate soil type and to measure OVLs present in the sample interval. Soil type and OVLs will be recorded on the boring logs. Procedures for PID calibration and OVL monitoring will be followed as described in the previous section. Soil cuttings, if any, will be placed in properly labeled 55-gallon drums and stored on site pending disposal. A.4 Groundwater Sampling Groundwater samples will be collected using a Hydropunch- or similar sampling device. The Hydropunch-will be pushed into the water-bearing zone by the drill rig and the water sample will be collected from the Hydropunch— using a clean, Teflon bailer and will be transferred to pre-cleaned bottles provided by the laboratory. All samples will be stored in a cooler containing ice for transport under proper chain-of-custody protocol to the laboratory. A maximum of 45 minutes will be allowed for a sufficient volume of groundwater to collect in the Hydropunch—prior to advancing to the next depth. All groundwater sampling equipment will be thoroughly cleaned prior to and following use. All decontamination water will be placed in 55-gallon drums, which will be properly labeled and left on site pending disposal. A.5 Piezometer Installation The nested piezometers will each consist of 1-inch diameter schedule 40 PVC casing with a 5-foot screen interval of 0.020-inch slotted casing. The exact depth of the screen intervals will be determined by the field geologist based on site specific lithology and constituent distribution information. Lonestar #3 sand, or equivalent, will be used as the filter pack adjacent to each screened interval and will extend a minimum of 2 feet above and G inches below the screened interval. If possible, a minimum of 10 feet of a cement/bentonite grout mixture will be tremied into the borehole to separate the shallow and deep screened zones. A bentonite seal comprised of a minimum thickness of 3 feet will be tremied into the borehole above the upper filter pack, followed by a cement/bentonite grout mixture tremied into the remaining portion of the annular space. The borehole will be completed at the surface with a traffic-rated well monument. Following completion of the piezometer installation activities,the location of the nested piezometer will be surveyed by a California-certified land surveyor. Northing and easting information, along with ground surface elevation of both piezometers will be collected. The piezometers will be developed at a minimum of 72 hours following completion of piezometer construction. A bailer will be used to remove the water and suspended sediments from the well casing. During the development, purged groundwater will be monitored for turbidity, pH, conductivity, and temperature. Purging Our ref.: Page: %%GM SANTA MRBARAIDATAV PRO S801UNOCALIC VALLMVVPS REYIPACMP2A.DOC 1 11 1 ARCADIS GERAGHTY&MILLER