ARCHIVED REPORTS_2019 SOIL MGMT PLAN (JULY-REVISED)

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Brusca File No. 137-002 Page 6 May 23, 2018 Murphy Parkway Property Waste Materials Reuse Workplan verification soil sampling beneath the area of removed wastes also are included. For reference, hazardous waste criteria and screening levels are included on the summary data tables. The laboratory reports and chain-of-custody documentation are presented in Appendix A. As outlined in the EMMP, samples stockpiled materials from WU1 containing the highest concentrations of total metals were analyzed for soluble Title 22 metals by the Waste Extraction Method (WET) by EPA Method 1311 using deionized water (DI) as the extractant; this element of the testing program was required by the CVRWQCB for the purpose of evaluating potential future leaching impact to groundwater posed by the waste materials. A total of 11 samples was selected for the DI WET metals testing, including samples from each of the five stockpiles. 5.0 WU1 MATERIALS REUSE EVALUATION Per the provisions of the approved EMMP, the laboratory data from the samples of stockpiled materials removed from WU1 have been evaluated to determine whether these materials are acceptable for onsite reuse in engineered fills during upcoming site development. As shown on Tables IV, VI, and VII, none of the 49 samples of the stockpiled materials from WU1 contained total metals, petroleum hydrocarbons, PCBs, SVOCs or dioxins/furans at concentrations above the commercial/industrial screening levels established in the EMMP (or in the case of arsenic, above the site-specific background concentration of 8.6 milligrams per kilogram established in the EMMP). Additionally, none of the results exceed hazardous waste criteria established in the California Code of Regulations (CCR) Title 22, Division 4.5. As such, these results indicate that the stockpiled materials from WU1 are acceptable for onsite reuse. Additionally, the project geotechnical engineering firm (Raney Geotechnical, Inc.) has observed the stockpiled materials and have determined that the materials are acceptable for onsite reuse form a geotechnical standpoint. Materials reuse evaluation has included consideration of the potential for future impact to groundwater as a result of possible leaching of metals from the materials. As shown on Table V, the DI WET concentrations from the tested samples for the majority of the Title 22 metals do not exceed California Maximum Contaminant Level (MCL) drinking water concentrations. However, the concentrations of DI WET arsenic, chromium and lead concentrations detected in most of the samples exceed the MCL values. We note that several groundwater samples have been collected and tested beneath the WU1 area as a part of past site assessment work, and none of the groundwater samples from this area have contained lead or chromium at concentrations above their respective MCL values, despite the fact that waste materials were handled and stored in this area for several decades starting in the 1960s (and during operation of the PNA facility, much greater volumes of wastes were stored in this area than were removed during the recent waste management work). As such, it does not appear likely that the chromium and lead in the removed/stockpiled waste materials represents a significant threat to groundwater quality. It is noted that elevated concentrations of arsenic (above the MCL value) have been detected in groundwater at various locations beneath the subject property, including beneath the WU1 area. However, in general, the distribution of elevated concentrations of arsenic in groundwater beneath the site is somewhat erratic, and some of the past groundwater samples collected beneath WU1 in the past have not contained elevated concentrations of arsenic. It is known that naturally-occurring elevated concentrations of arsenic exist in groundwater in other areas of San Joaquin County, and the arsenic detected in groundwater beneath the subject property may also be naturally occurring.