COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

Q Limited Phase 11 Subsurface Investigation Report 902-908 East Scotts Avenue Stockton,California a ntea g ro u p Antea Group Project No. UPR82572A In order to adequately evaluate the presence of metals in shallow soil,Antea Group compared the reported metals concentrations against their natural occurrence, or typical "background" concentrations, in soils. Each metal concentration listed in Table 3 is compared to published background data for California soils. The comparison concentrations are averages from a 1996 report that established a database for 46 trace and major elements found to occur naturally in 50 benchmark soil samples collected throughout the state of California (Kearney, 1996). Although they exceed the RSLs, detections of chromium and vanadium in soil were reported at concentrations less than their respective average background soil concentrations published in the 1996 study. Arsenic concentrations are greater than the background average, but the reported concentrations fall within the range (min/max) of naturally occurring metals concentrations listed in the Kearney report(0.6 to 11.0 ppm) with the exception of two soil samples(620 at 2.0-2.5 feet bgs and B16 at 1.0-1.5 feet bgs). Antea Group reviewed the metal data to determine site-specific background trends and determine any anomalies at the site. The 1.0-1.5 feet bgs sample collected in B17,the 2.0-2.5 feet bgs sample collected in B20, and the 1.0- 1.5 feet bgs collected in B7 all had three or more concentrations of metals that appear to be significantly higher than the overall sample set.These higher metals concentrations may represent areas of environmental concern. 3.3.4 Gasoline Range Organics (GRO), Diesel Range Organics (DRO), and Motor Oil Range Organics (MORO) The laboratory tested a total of 23 soil samples for GRO and 21 soil samples for DRO and MORO. The detected concentrations were compared against the California Regional Water Quality Control Board-San Francisco Bay Region Industrial Environmental Screening Levels (ESLs) for shallow soils and the SSLs. Table 4 includes analytical summaries of soil analytical results for GRO, DRO, and MORO. For GRO, only two of the 22 samples tested had detections above the LRL; these detections were also above the ESL of 83 mg/kg. They were samples collected from 1.0-1.5 feet bgs from boring B3 and B7 and had concentrations of 2,300 and 1,700 mg/kg, respectively. Both concentrations coincide with the VOC detections also reported in those samples. Concentrations of DRO were detected above the LRL in all but two of the 22 submitted for DRO analysis. Six of the reported concentrations were above the ESL of 83 mg/kg(concentrations ranging from 280 mg/kg to 2,300 mg/kg, the highest in B7 at a depth of 1.0-2.5 feet bgs). Eight of the 21 samples submitted for MORO reported concentrations above the LRL; however, only one concentration exceeded the ESL of 2,500 mg/kg. The sample exceeding the ESL was collected from 1.0-1.5 feet bgs in B7. This soil sample also exhibited GRO and DRO detections greater than the ESLs. 3.3.5 Polychlorinated Biphenyls (PCBs) Antea Group submitted a total of 10 soil samples for PCBs. Of the samples submitted, only one concentration (0.054 mg/kg in B7 at 1.0-1.5 feet bgs) was detected above LRL, a concentration less than the RSL, ESL, and SSL. Table 4 includes a summary of the analytical data for PCBs. 8 www.anteagroup.com