SITE INFORMATION AND CORRESPONDENCE

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Jerry I.ilc Occcmher 6, 000 Page 2 4) The Sacramento-San Joaquin Delta is subject to tidal flux. A tidal influence study is needed on the uppermost water bearing unit. If tidal flux is detected, then the concept of up and down gradient becomes questionable. Alternate up gradient criteria will then be needed. 5) Criteria for determining the bottom of drilling mud is missing from the report. The GSU suggests a continuously logged core followed by correlation with direct push tip data. 6) Criteria is needed to insure against cross contamination during direct push through the drilling mud. 7) The relative "weathering" of TPH-D should be assessed as well as the leaching potential of TPH to ground water. 8) The GSU recommends using citric acid for the WET test (page 3-2 at top) due to the presence of metals. 9) Direct push holes should be decommissioned with either neat Portland cement or bentonite pellets that are hydrated (when no more than 20 feet deep). 10) All missing wells should be located and properly decommissioned to prevent conduits for contamination. 1 1 ) The site should assess and measure the vertical gradients present to deeper water bearing 11111 ts. 12) All new wells should have screen/filter packs selected based on field observations only. The workplan can state the anticipated combination. Filter packs must be installed by tremmy pipe (see DTSC well drilling guidance). 13) The GSU recommends against the mixing of bentonite with Portland cement unless the driller brings a scale and weighs each component. Use neat cement. 14) The GSU recommends against the use of bailers to sample the wells. Bailers are a poor . sampling technique that can give inconclusive results. 15) Sampling of ponded surface water instead of actual runoff(page 3-7) is not recommended by the GSU. ll'vau have any questions please telephone meat (916) 255-35831.