SITE INFORMATION AND CORRESPONDENCE

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Executive Summary The former Kearney-KPF facility is located at 1624 East Alpine Avenue, Stockton, California (site) (U.S. Environmental Protection Agency ID No. CAD981429715). Beginning in 1951, the site was developed for use in manufacturing high-voltage switching devices for utility companies.Two manufacturing processes, silver plating and galvanizing, resulted in the generation of hazardous wastes.Site assessment activities began in the late 1980s. The ponds in which waste was formerly disposed were closed in 1991. A groundwater treatment system was installed and began operation in July 1992. The treatment system was shut down from late 1998 until 2003 to construct and test an enhanced groundwater treatment system to remove 1,4-dioxane from groundwater and supplement removal of other volatile organic compounds. The treatment system was shut down from March 2012 to January 2015 to perform a rebound study. As of September 2017, when the California Department of Toxic Substances Control (DTSC) Post Closure Permit (permit) was renewed, the treatment system is being pulsed in approximately 3- month periods; it is on during Q2 and Q4, and off during Q1 and Q3. In 2018,over 36 million gallons of groundwater were extracted and treated.The average flow rate was 153 gallons per minute.The uptime of the treatment system, when it was operating in Q2 and Q4, was 100%. Kearney continues corrective action monitoring under the 1990 Interim Groundwater Remedial Action Plan and the DTSC permit.As outlined in the renewed DTSC permit,groundwater monitoring was changed from quarterly to semi- annual. In addition,the Water Quality Protection Standard concentration limits (CLs)for the site were revised. Monitoring at the site in 2018 included groundwater level measurements and water quality sampling in May and October. Concentrations of volatile organic compounds in groundwater have declined by orders of magnitude since the initiation of remediation at the site. Volatile organic compounds in deep zone wells have consistently remained below the CLs, at undetectable levels, for many years. Recent concentrations greater than the CLs in the intermediate zone are now limited to single-digit exceedances for four constituents in five wells, with the highest being trichloroethylene in KEW-3U (9.2 micrograms per liter). Concentrations greater than the CLs in the shallow zone are limited to four constituents in six wells, with the highest being tetrachloroethylene in SMW-2 (14 micrograms per liter). Comparison of October 2018 water quality results with those from October 2017 shows that the extent of CL exceedances in the shallow and intermediate zones has remained similar. D U D E K 10275-1 ix March 2019