FIELD DOCUMENTS AND WORK PLANS 2004-2014

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State of California—California Environmental Protection Agency Department of Toxic Substances Control 4. Create 10 in-situ linear reactive treatment barrier zones strategically placed in accessible locations across the plume to address movement of impacted groundwater via the observed plume migration trends and natural groundwater flow.This concept allows enhancement of remedial actions despite the access limitations posed by the existing development of areas overlying the plume. Reductant solution will be injected using rotary sonic rig drilling technology to create each reactive barrier in a similar manner and spacing as the Phase It pilot study, Casings are advanced to the bottom of the speOied interval (beginning with the shallowest) and then raised 8 feet to expose the interval of the borehole for injection, The reductant solution Is transferred through hoses from mixing tanks into pumps and through the drill casing into the subsurface. Shallow injections will be advanced across multiple contiguous 8 foot vertical intervals from approximately 55 to 85 feet to treat the shallow groundwater. Deep injections will be advanced from approximately 55 to 115 feet to treat both the shallow zone and 100-foot sand zone, 5. For the most severely impacted areas such as the core of the plume with concentrations in excess of 5,000 micrograms of chromium per liter (ug/L), direct treatment in a grid injection approach to eliminate this principle source of contamination. The cleanup level for chromium is 0.050 milligrams per liter(mg/L). 6. Characterize the site lithologic heterogeneity to ensure optimum usage of treatment chemicals, areas targeted for reductant injection following the same approach used during the pilot study to evaluate the lateral and vertical distribution of chromium in high and low permeable zones. Soil borings will be advanced using a Cone Penetrometer Testing rig which pushes rods into the subsurface. Parameters will be measured to quantify soil characteristics and hydrologic zones.Depth-discrete groundwater samples will be collected using a hydropunch, or equivalent method. 7. Modify the compliance and monitoring program to incorporate other analytes of interest (e.g. arsenic) and to monitor the performance of the remediation. If monitoring suggests elevated concentrations of arsenic greater than 500 ug/L persist beyond a one (1)-year period, contingency measures will be implemented including continued or renewed extraction of groundwater to capture the soluble arsenic. The federal Maximum Contaminant Level (MCL) for arsenic is 10 ug/L in drinking water. Current arsenic concentrations are below the MCL of 10 ug/L. Evaluation of groundwater sampling analytical results will be performed after each quarterly groundwater sampling event to monitor the distribution of reductant solution within the aquifer. Upon completion of the in-situ injection treatment, evaluation of groundwater sampling results will assist in determining whether any additional in-situ treatments are necessary to treat remaining hot spots. Due to the heterogeneity of the site lithology, it is possible that supplemental injections may be necessary in areas of the site where hot spot concentrations remain. Lithologic zones comprising finer grained material (silts and clays) that are less permeable may retain chromium and require additional dosing to effectively reduce concentrations. If after evaluating the available date, additional injection locations are necessary, the proposed injections, depth of injections, and specific solution blending details (solution strength)will be presented for regulatory approval prior to additional injection implementation. 8. Continue the groundwater treatment system operation until remediation cleanup goals are achieved. The proposed work on the Franklin school site will be performed during periods when school will not be in session. Work will be scheduled when school is out of session and the athletic field has reduced usage. After field activities are completed, surface completion will be restored to like original condition. The area of the proposed field activities will not interrupt the listed services. The project is expected to occur in the spring/summer 2007 and take approximately 12 months to complete. A notification to interested parties is expected to be sent out prior to the start of field work. BACKGROUND/HISTORY: in 1943, MCTC purchased the South Yard and began wood milling and cooling tower fabrication operations using pre-treated components purchased from vendors and shipped to the site. Wood preserving operations began in 1966 when the North Yard facilities were constructed. The facilities constructed included pressure vessels used for wood treatment (retorts), a retention pond constructed to impound and collect surface water run-off, a series of catch basins, and aboveground building structures.Wood products were treated with a copper/chromium/arsenic treating solution between 1966 and June 1982. to June 1982, the solution was replaced with an acid/copper/chromium solution. Wood treating operations continued until 1991. Chemicals used in these operations were released to the ground resulting in contamination of the soil and underlying groundwater. The Site has been the subject of investigation and remedial action since the mid 1980"s to address this contamination. In June 1990, a RAP was approved and remedial actions were implemented. Surface soils contaminated with arsenic, copper and/or chromium have been covered to prevent direct contact and the pipes/culverts/ditches area on or near the South Yard have been cleaned. An electrochemical precipitation system (high levels) and ion exchange DTSC 1327(1106106)