WORK PLANS - Laserfiche WebLink

Home Browse Search

Additional waste extraction tests (Di-WETs) were performed as part of the initial Phase II analysis (Table 0U8-M, soil samples 6-7, 6-8, and 6-10). WET testing was conducted for samples with relatively high concentrations of arsenic, copper, and lead. The arsenic and copper results and one lead results did not indicate high-soluble metal concentrations. One lead result did, however, indicate relatively high-soluble lead (58 ug/L). Correspondence indicates that high-soluble lead soil was removed and that sample results and excavation details were supplied to the County, and our document review has located the proposal for this work, but sample results and excavation details have not yet been located. Subsequent soil and groundwater samples were conducted during installation of Monitoring Well MW-13, which was located approximately 30 feet northwest of an OU 11 rail spur. Soil samples were collected at depths of 10 and 15 feet bgs and analyzed for CAM 17 metals (Table OU11-M, soil sample 23-1). Most results are ND, except for barium, chromium, copper, nickel, vanadium, and zinc. Concentrations are generally lower than surficial OU 11 concentrations and are generally similar to OU 1 and OU 7 concentrations. These data further indicate that OU 1 and OU 7 metal concentrations represent natural background conditions. One groundwater sample was also collected and analyzed for CAM 17 metals (Table OU11-M, water sample MW-13). Results are all ND, except for barium (260 ug/L) and vanadium (20 ug/L). The barium concentration is below the EPA Tap Water and Tier 1 Groundwater ESLs and the vanadium concentration is below the EPA Tap Water RSL of 86 ug/L but above the Tier 1 Groundwater ESL of 19 ug/L. These results are similar to Hydropunch concentrations from OU 1 (Table OU1-M, Hydropunch samples 5-1-HP and 5-7-HP), indicating that elevated metal concentrations in surf icial soil samples have not impacted groundwater. Metals: Recommendations Elevated metal concentrations are below Industrial Thresholds and proposed construction includes a concrete cap; however, metal concentrations in soil exceed Protection of Groundwater SSLs. In addition, while soluble lead encountered during Phase ll explorations is known to have been removed and disposed offsite, removal details are unknown. Kleinfelder therefore recommends collecting soil samples at the location of the removed soluble lead to confirm its removal. Kleinfelder also recommends collecting groundwater samples to confirm that elevated metal concentrations indicated by Phase II data have not impacted groundwater. Petroleum/Solvents: Existing Data Eight soil samples were analyzed for TPHd, TPH1o, TPHueh, and Semi-VOCs, including TICs (Table OU11-P, soil samples 6-6 through 6-13). These analyses yielded 624 results, of which there were 14 detections. TPHueh was detected in each of the eight samples at concentrations ranging from 1.3 to 70 mg/kg. These concentrations are below the Industrial Thresholds of 440 mg/kg but exceed the Protection of Groundwater SSL of 1.5 mg/kg. Semi-VOCs were ND, except for six TIC detections at concentrations ranging from 0.13 to 2.2 mg/kg4. These TICs do not have associated ESLs. Most laboratory reporting limits are not tabulated. TPH reporting limits, however, are tabulated. These limits are all below Industrial Thresholds. Some Semi-VOC 4 Semi-VOC Cyclo-hexanone and an unknown semi-VOC were detected at concentrations below the Industrial Thresholds and Protection of Groundwater SSLs; however, these analytes were also detected in laboratory method blanks, strongly indicating that these concentrations were caused by laboratory cross-contamination. 20173951.001A/SAC17R68420 Page 21 of 26 November 2, 2017 0 2017 Kleinfelder www.kleinfelder.com KLEINFELDER 2882 Prospect Park Dr., Suite 200, Rancho Cordova, CA 95670 p I 916.366-1701 f 1916.366-7013