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SAN 10 A Q U I N Environmental Health Department <br /> COUNTY <br /> 2002 Study) by Ninyo & Moore (provided as Attachment B in the Work Plan). It <br /> appears that the locations of the trenches somewhat align with the estimated extent <br /> of debris and/or refuse provided in Figure 1 of Attachment I with the following <br /> exceptions: <br /> a. Area between Trench Location 1 and the northern property boundary. <br /> b. Area along the southwestern corner near Trench Locations 26 and "ASH 1." <br /> The Work Plan should include trenching in these areas to fully delineate the extent of <br /> the waste shown in Attachment I. <br /> 2. The Work Plan states that trenching will be used to determine if buried waste is <br /> present but is unclear of how the lateral and vertical limit of waste will be confirmed. <br /> Trenching should be used to find these limits of the waste by digging both laterally and <br /> vertically until native is discovered. It is LEA understanding that Figure 1 in Attachment <br /> I represent an "estimated" extent based on interpolations of the data only. The October <br /> 2002 Study did not fully delineate the waste extent. As such, the Work Plan should be <br /> revised to describe how trenching will continue until native soil is encountered both <br /> laterally and vertically on the property so a more accurate figure can be produced. <br /> 3. The Work Plan does not propose collecting any samples for laboratory analysis. <br /> Since the trenches are in different areas from the October 2002 Study, the waste <br /> discovered should be sampled for the following chemicals that were found in the <br /> October 2002 Study using the same methods: <br /> a. CAM 17 Metals <br /> b. Soluble Threshold Limit Concentration (STLC) and STLC Deionized Water (STLC <br /> DI-WET) for specific Title 22 metals that exceeded 10 times their respective <br /> thresholds in accordance with federal and state hazardous waste criteria. <br /> c. Toxicity Characteristic Leaching Procedure (TCLP) by USEPA Method <br /> 6010/7471A for those samples containing the highest metal concentrations to <br /> evaluate whether the waste would be classified as federal hazardous. <br /> d. Reference: DTSC Hazardous Waste Classification: <br /> https://dtsc.ca.gov/tclp-and-wet-test-methods/ <br /> 4. Attachment I of the Work Plan found some organic debris and refuse within the <br /> trenches on the property. Although no landfill gases were found in the October 2002 <br /> Study in those trenches, there still exists a potential due to these contents. As such, <br /> the LEA requests that the trenching activities be monitored for methane as a health <br /> and safety precaution. Results from the monitoring should be included in the final <br /> 2 of 3 <br />