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Work Plan for Additional Sit�ssessment • ARCO Facility No. 6100 Tracy,California Page 9 will be collected using a disposable bailer, transferred to laboratory supplied glass vials, and placed in an ice-chilled cooler. Samples will be forwarded to a California state- certified analytical laboratory for chemical analysis. Strict chain-of-custody procedures will be followed from the time the sample is collected until the time the sample is relinquished to the laboratory. The elevation of the top of each well casing will be surveyed to the nearest 0.01 vertical feet under the direction of a California licensed surveyor. Task 2b: Soil Borings (Hollow Stem Auger Drilling) Two soil borings (B-39 and B-40) will be advanced to approximately 100 feet bgs using a drilling rig equipped with hollow stem augers. Soil samples will be collected every five feet for soil classification and laboratory analysis. Collection of depth discreet water samples will also be attempted using a Hydropunch sampler. Efforts will be made to target permeable material or water bearing zones from which groundwater can be withdrawn using the Hydropunch sampler. The target depths will be based on existing monitoring data and the geophysical logs from the previous borings. The soil samples will be collected using a California-type, split-spoon sampler equipped with three or four pre-cleaned brass tubes. The ends of the bottom-most, intact tube from each sample interval will be lined with TeflonTm sheets, capped, and sealed. Each sample will then be labeled, placed in a resealable plastic bag and stored in an ice-chilled cooler. The samples will remain chilled until relinquished to a state-certified analytical laboratory. Strict chain-of-custody procedures will be followed from the time the samples are collected until the time the samples are relinquished to the laboratory. Soil contained in the remaining brass tubes will be screened for volatile organic compounds using field instrumentation equipped with a photoionization detector (PID). Delta will record PID readings, soil types, and other pertinent geologic data on the borehole log. Soil samples used for logging will be classified using the Unified Soil Classification System. A minimum of four soil samples from each boring will be submitted for chemical analysis, including the sample exhibiting the highest PID response, the sample from just above groundwater (if encountered), and the sample collected from the bottom of the boring. Additional samples may be collected at the discretion of the registered geologist overseeing the project. The water samples will be collected using Hydropunch sampling equipment. The Hydropunch is conveyed to the bottom of the boring using drill rods. Once on the bottom, the Hydropunch is driven approximately two feet and then opened by lifting up the drill rod thereby exposing the screen. Once the tool is opened, water enters and a sample can be collected using a small diameter bailer. The tool will remain open until a full sample is collected or up to approximately 20 minutes if yield is poor. The sample will then be transferred to a laboratory supplied glass vial and placed in an ice-chilled C:\ARCO\6100\REPORTS\6100 workplan 05-22-Ol.doe