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Lee Higgins -2- 14 February 2011 ♦ Chevron, Former Tracy Pump Stat The workplan proposes the following: • Drill one boring near TS-04 and at least four offset soil borings to a depth of approximately five feet below ground surface (bgs) to: a) collect samples at three, four and five feet bgs and submit for PAHs analysis to more accurately define the lateral and vertical extent and determine the depth of the proposed excavation; b) submit samples for waste characterization and disposal purposes. • Up to 12 contingent offset borings may be drilled to further delineate the lateral extent of affected soil and to better define the proposed excavation dimensions. • The pre-excavation information will assist in determining the lateral/vertical limits to allow immediate post-excavation backfilling to reduce the inconvenience for operating businesses near the Site. Central Valley Water Board staff has the following comments: • At least one or more of the initial borings needs to be continued to a depth of at least 10-12 feet bgs with additional samples collected to confirm the vertical extent of affected soil. • The excavation backfilling and surface repairs should be consistent with the property owners' specifications. • The summary soil removal report should include the approximate volume of affected soil excavated including an estimate of the volume of PAH and/or residual crude oil material removed. Central Valley Water Board staff concurs with the workplan provided our comments are addressed. By 15 June 2011, please submit the analytical results and the excavation soil sampling report. If you have any questions or comments, please contact Dean Hubbard at (559) 445-5179. SHELTON R. GRAY C. DEAN HUBBARD Senior Engineering Geologist Engineering Geologist P.G. No. 6357 cc: Michael Infurna, San Joaquin Country EHD, Stockton Gary Dobler, Tracy Michael Hurd, SAIC, Oakland