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MEMORANDUM6 CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 361-5600 Sacramento, CA 95827-3098 ATSS Phone: 8-495-5600 TO: Greg Vaughn FROM: Camilla Williams Senior WRC Engineer Engineering Geologist DATE: 6 July 1990 SIGNATURE: *'1xG4i/Qul~ SUBJECT: SOIL ASSES.WENT REPORT, COMPLETION OF HYDROGEOLOGIC ASSESSMENT REPORT AND MARCH 1990 QUARTERLY REPORT, KEARNEY-KPF, SAN JOAQUIN COUNTY Soil Assessment Report The Soil Assessment Report (SAR) , dated 2 May 1990, was submitted by Hargis and Associates for Kearney-KPF. I have reviewed the SAR and have found it to be acceptable. The SAR included the results of an environmental fate analysis using the Designated Methodology to determine the threat to water quality and a risk assessment to determine the health hazards associated with potential exposures to the soils in the hazardous waste management units. The conclusions in the SAR were based on analytical and geotechnical data from 176 soil samples. Surface soil samples were analyzed for total concentrations for the health based risk assessment, and 20 percent of these samples were analyzed for soluble concentrations using both citric acid and deionized (DI) water. Subsurface soil samples were analyzed for soluble concentrations using citric acid for the acidic soil samples and DI water for the non-acidic soil samples. Statistical background concentrations were calculated for each heavy metal constituent based on the results of the total concentrations and both citric and DI water soluble concentrations. Volatile organic constituents (VOCs) were not detected in background soil samples. The analytical results per constituent of samples from areas of potential contamination were compared to their respective background concentrations. All heavy metal and VOC concentrations greater than background were evaluated to determine the potential of transport to the ground water by infiltration. All analytical soil data from previous investigations, as well as the current investigation, were used in the comparisons to determine those areas needing additional remediation. Based on these procedures, it was determined there were seven areas which should be resampled and analyzed prior to either excavation and disposal in a Class I landfill or stabilization of the areas to prevent future leaching of contaminants from the soil . It was proposed that the hazardous waste management units then be closed by compacting fill and diverting drainage away from these units. My review of the SAR is favorable. The report was thorough and well documented and as a result, I have relatively few comments. My major concern with the report is in regards to the total heavy metal concentrations for surface soil samples listed in Table 31. These samples taken from 0.0 to 0.2 feet below ground surface) were not analyzed for soluble concentrations. If the average DI water conversion factor for cadmium (Table 30) is used to convert the total concentrations to soluble concentra- tions, there are few of the surface soil samples which exceed the soluble designated level (SDL) for cadmium. The cadmium conversation factor was calculated based on results where the soluble concentrations were less than the detection limit. It is, therefore, possible that contaminated soils with cadmium concentrations greater than 1.77 milligram per kilogram (mg/kg)(the highest total concentration listed in Table 30) may have the potential to leach cadmium from the soil . There are four surface soil samples which had cadmium concentrations greater than 1.77 mg/kg. They are: PSI-8