SITE INFORMATION AND CORRESPONDENCE_FILE 1

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J. R. Simplot, Lathrop -6- I August 2UU San Joaquin County a qualified professional and submitted in hard copy to this agency for review and concurrence before undertaking these types of activities. 2) The email received on 23 March 2007 was informative and briefly described the assessment and remedial work that took place in response to the ammonium sulfate release. The work plan portion of the email states: "When we get results that are about as low as we think we are going to get, we will resample and analyze them both in our lab and at a certified outside lab. We will also conduct additional background sampling adjacent to the soil contamination areas." Although, I had discussed with Mr. Yanak on the telephone what activities were planned for future assessment and remediation of the impacted areas, the actual work plan needs greater detail and justification for the planned assessment work. The work plan should include detailed figure(s) showing known areas of impact, proposed and existing soil sample locations, data table(s) showing all data collected to date (analytical results, depth of samples and amount of soil excavated). The work plan must detail how background samples are to be collected and used for defining the limits of impact and justify any future excavation work. The work plan also needs to address potential impacts to groundwater. For groundwater assessment, the work plan should propose and detail proposed assessment borings, installation of monitoring wells (three wells at a minimum) or at least grab groundwater sample analysis. Please prepare a work plan that addresses the above comments regarding ammonium sulfate release to the surface water drainages and submit it to this office by 12 September 2007. 3) The analytical results presented in the email work plan were analyzed by J. R. Simplot's laboratory. While these results are acceptable to help guide the investigation and remedial work, final soil and groundwater confirmation samples that will be used to define the limits of impact must be analyzed by a California — certified laboratory. Please indicate in the above requested work plan a statement that all soil and groundwater confirmation samples will be analyzed by a California — certified laboratory. 4) Based on nitrate studies reviewed by the Regional Water Board, soil cleanup goals for niP:rates must achieve less than either 100 milligrams per kilogram (mg/!gig) or established background levels for protection of human health and the environment. Groundwater cleanup levels for nitrate must achieve a level less than 10,000 ug/L (the Public Health Goal) and/or established background levels. Groundwater ammonium results should not exceed 1,500 ug/L (based on taste and odor) or established background levels. Ammonium soil cleanup goals can be based on either a waste extraction test method using deionized water where the extraction analysis does not exceed 100 ug/L or established background levels. J. R. Simplot must establish background levels of nitrate and ammonium in soils and groundwater, which will likely serve as the cleanup goals for the impacted area. Section 20415 of Title 27 (http://www.waterboards.ca.gov/cwphome/land/docs/t2797m.pdf) provides guidance on how to establish background concentrations.