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Ms Julie Raining - 2 - • 4 October 2001 <br /> Georgia-Pacific Corporation <br /> 2. The results of semi-annual groundwater sampling of groundwater monitoring well BC-20 <br /> indicate that groundwater in Unit 2 is impacted at approximately 1400 feet down gradient of the <br /> waste water basin. Therefore, the selected groundwater remedy will be required to address lateral <br /> as well as vertical impacts. The Workplan should be amended to include provisions for defining <br /> lateral impacts to groundwater, and the development of a comprehensive site conceptual model. <br /> This should include soil and or groundwater sampling down gradient of monitoring well BC-20, <br /> groundwater sampling from extraction wells RW-1 and RW-2, the collection of hydropunch <br /> samples in the vicinity of dry shallow wells BC-2, BC-3, BC-4,BC-5, and BC-9, and an <br /> assessment of vertical and horizontal gradients in the impacted area. <br /> 3. Due to previous on- and off-site discharge constraints of treated groundwater, the selected <br /> remedial alternative will most likely involve an in-situ technology that will require the direct <br /> injection of a reductant to groundwater. It should be noted that the introduction of such materials <br /> into the aquifer is considered discharge of a waste to waters of the state and, as such, will require <br /> Waste Discharge Requirements.Recommendations for pilot scale testing should adequately <br /> address the following topics at a minimum; (1)what the final and byproducts, if any, maybe, (2) <br /> what other chemical changes could result from an altered PH or redox potential, (3)what the <br /> long-term ramifications of altering geochemistry could be with respect to permeability of the <br /> aquifer, and(4) a contingency plan for removing injected substrates and obtaining hydraulic <br /> control if necessary. Will the aquifer return to its previous state once the amendments are <br /> consumed? In addition, the selected remedial strategy should possess the capability of attaining <br /> the California Public Health Goal for drinking water of 1.1µg/1. <br /> Please provide an addendum to the Workplan that adequately addresses the comments listed above by 1 <br /> November 2001. In addition, please provide an Investigation Report by 17 December 2001. The report <br /> should be prepared in general accordance with attachment entitled; Items to be included in a Site <br /> Assessment Report. <br /> You may reach me at (916)5. 3411 or at tavlorb(a)xb5s.swrcb.ca.Qov with any questions. <br /> BrianTaylor f <br /> Associate Engineering eologist <br /> l <br /> Attachment: <br /> cc: Mr.Michael Infura, San Jaoquin County Department of Environmental Health, Stockton <br /> Mr. Robert L. Hammond, Acton Mickelson Environmental, Inc., El Dorado Hills <br />