ARCHIVED REPORTS_SOIL AND GROUNDWATER INVESTIGATION REPORT 2008

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' APPENDIX B: FIELD, SAMPLING,AND ANALYTICAL METHODS B.1. DRILLING From February 25 through 27, 2008, SAIC observed subcontractor RSI Drilling(C57#802334) advance seven soil borings (SB-26 through SB-29 and SB-31 through SB-33)as shown on Figure 2. The borings ' were advanced to depths ranging from 40 to 44 feet below ground surface using the Geoprobe®Systems (Geoprobe®) Dual Tube DT 21 system(2.125-inch outer rods) along with a continuous coring device used to collect soil samples. Dual Tube tooling was selected to provide a seal when sampling through ' saturated soils and to facilitate the installation of pre-packed well screens as explained in section B.3. The completion of soil borings generally conformed to SAIC Field Technical Procedure(FTP)No. 525, "Soil Sampling Using an Auger." In accordance with the approach prescribed in the Second Draft ' Revised Technical Approach to Site Evaluation and Decision Making, Old Valley Pipeline Sites (Geomatrix, 2005 update), and to the extent practicable, SAIC attempted to collect soil samples from the target depth. The samples were screened with photoionization detection equipment,using procedures consistent with SAIC FTP No. 750, "Field Measurement Procedures—Organic Vapor Detection,"to detect the presence ' of residual petroleum in soil. The soil was logged in general accordance to the Unified Soil Classification System as presented in American Society for Testing and Materials 2488-90 under the supervision of a California Professional Geologist. Additional information was entered into field logbooks to document where, when,how, and from whom any vital project information was obtained,using procedures described in SAIC FTP No. 1215, "Use of Field Logbooks." Each open borehole was plugged and abandoned according to Stanislaus County Department of ' Environmental Resources or San Joaquin County Environmental Health Department requirements following completion of the soil borings. B.2. SOIL SAMPLING Soil samples were deposited into U.S.Environmental Protection Agency(EPA)-approved containers and submitted to a California-certified laboratory,Lancaster Laboratories,Inc. (Lancaster)under SAIC chain- of-custody protocol and analyzed for the constituents of concern(COCs). SAIC also collected soil samples from less than 10 feet bgs for use in a human health risk assessment (HHSE). Soil samples collected for the HHSE were analyzed for the COCs. Refer to Appendix D,Data Usability Summary and Laboratory Reports for more information. B.3. GROUNDWATER SAMPLING The borings were advanced to total depth and then installed with pre-packed well screens. The pre- packed well screens, manufactured by Geoprobe®, were installed in general conformance with American Society for Testing and Materials Method D6725-04. The pre-packed well screens were constructed of 0.75 inch-diameter, 0.010-inch, machine-slotted polyvinyl chloride well casing packed with 20/40 mesh ' sand and encapsulated with a stainless steel screen. The external diameter was 1.4 inches. SAIC deposited grab groundwater samples into EPA-approved containers using a peristaltic pump and disposable tubing. Groundwater parameters such as temperature,pH, electrical conductivity, and turbidity were measured during purging. After purging the well casing, groundwater samples were decanted into laboratory-provided bottles, labeled, and placed in an ice-cooled chest pending analysis by Lancaster. B-1 Of::: .M/JW1JF`® ' From Science to Solutions