Laserfiche WebLink
r .y ► <br /> a <br /> Mr. Jerry Lile (DTSC) <br /> Page 3 of 7 <br /> The samples were analyzed for total copper by EPA Method 6010B with the addition of total <br /> lead and total chromium by EPA Method 6010B and hexavalent chromium by EPA Method <br /> 7196A for three selected samples. After reviewing the results and consulting with DTSC, <br /> additional analysis was performed. Samples 0/3 S/SURF, 151E/3S and 166E/3 S were analyzed <br /> for soluble copper by DI-WET extraction and EPA 6010B analysis. Sample 0/3S/SURF was also <br /> analyzed for soluble copper and soluble lead by citric acid-WET (STLC) extraction and EPA <br /> 6010B analysis. The analytical results for all post-excavation soil samples are summarized in <br /> Table 2. <br /> Risk Evaluation <br /> A Human Health Risk Evaluation was conducted in a manner consistent with the procedures set <br /> forth in the Preliminary Endangerment Assessment Guidance Manual("PEA" -DTSC, 1994). <br /> It was determined that the concentrations of contaminants in soil at the site would not present a <br /> significant toxicity hazard to potential residential occupants (Hazard Index <1 and blood lead <br /> concentration <10 ug/dl), nor a significant incremental increase in lifetime cancer risk (< one <br /> chance in one million). <br /> We concluded that the extremely low solubility of the copper in the site soil (less than 1%) and the <br /> actual DI-WET leachate concentrations (which were at least an order of magnitude below drinking <br /> water standards) indicated that no significant threat to groundwater, surface water, or the <br /> environment exists. <br /> ADDITIONAL SOIL SAMPLING <br /> The California Regional Water Quality Control Board (RWQCB) expressed concern to DTSC <br /> that the water-soluble concentrations of copper in the DI-WET leachate from the three samples <br /> analyzed in November 2003 [0.08 to 0.12 mg/1 (ppm)] exceeded the aquatic toxicity criteria of <br /> the National Toxics Rule (NTR), California Toxics Rule (CTR) and the National Recommended <br /> Water Quality Criteria to Protect Freshwater Aquatic Life (US EPA, 2000 and 2002). For <br /> surface water in the San Joaquin River near Stockton (hardness ranging from 35-135 ppm) the <br /> standard for continuous concentration would be between 0.004 and 0.012 ppm and the standard <br /> for maximum concentration between 0.005 and 0.018 ppm. <br /> Since the DI-WET analysis was only run on samples exhibiting elevated concentrations of total <br /> copper, DTSC requested an investigation to determine the water-soluble copper concentrations in <br /> background soil at the site. <br /> G:\GROUNDZE\MARINA\VillageWest\Aquatoxrpt.doc <br />