ARCHIVED REPORTS_XR0011956 - Laserfiche WebLink

Home Browse Search

r + Third Quarter 2005 Quarterly Groundwater Monitoring Report Stockton Center Site Authority-University park October 18,2005 Page 4 of 6 Table 3 Groundwater Analytical Results (September 1, 2005) Sample ID_ MW-1 MW-2 MW-3 Analyte Units-* /L L Benzene <0.5 <0.5 31.6 Toluene <0.5 <0.5 <0.5 Ethyl benzene <0.5 <0.5 26.1 Total xylenes < 1.0 1.0 22.4 TPH-G <50.0 105 699 TPH-D <50.0 <50.0 <50.0 TPH-MO <500 <500 724 TPH-K <250 <250 333* MTBE <0.5 <0.5 51.3 Ethanol <20.0 <20.0 <20.0 Tertiary-butanol <5.0 <5.0 15.3 Di-iso2ro2yl ether <0.5 <0.5 <0.5 Ethyl tertiary-butyl ether <0.5 <0.5 <0.5 Tert-amyl methyl ether <0.5 <0.5 1.0 1,2-dichloroethane <0.5 2.8 41.8 112-dibromoetharie <0.5 <0.5 <0.5 *=The sample chromatographic pattern does not resemble the fuel standard used for quantitation. Unit Conversions: Analytical ug/L:parts per billion(ppb) TPH-G-total petroleum hydrocarbons quantified as gasoline. TPH-K,D,and MO=total petroleum hydrocarbons quantified as kerosene,diesel,and motor oil. MTBE=methyl tertiary-butyl ether SUMMARY AND PROPOSED FUTURE WORK The laboratory analytical results for the current monitoring event are generally consistent with the historic monitoring data for monitor wells MW-1 and MW-2. Benzene, ethyl benzene, and total xylenes were detected in the groundwater sample collected from monitor well MW-3 at the highest concentrations since monitoring began in December 2001 (see historical groundwater monitoring data, attached). Total petroleum hydrocarbons quantified as motor oil was also detected for the first time in monitor well MW-3 (at a concentration of 721 gg/L). The current groundwater gradient direction (northeast) is within the historic range of groundwater gradient directions (approximately due north to approximately due south but often approximately to the east) and is more consistent with the historic mean than the groundwater gradient direction (north) indicated during the previous event in May 2005. The next groundwater monitoring event is scheduled for November 2005. Condor prepared a Soil and Groundwater Remediation Work Plan, dated March 3, 2003, at the request of David Rosso, representative for the Stockton Center Site Authority (SCSA). At that time, Site development was anticipated to proceed rapidly and the proposed scope of work for remediation was intended to facilitate the rapid Site development by quickly and aggressively cleaning up the Site with less regard to cost. The scope of work described in the Work Plan included (1) groundwater dewatering with dewatering wells, groundwater treatment, and proper disposal of treated groundwater; (2) soil over- excavation, including transport and disposal of contaminated soil; and (3) in-situ groundwater remediation utilizing ozone sparging technology. In a letter dated March 27, 2003, Mr. Nuel Henderson of the San Joaquin County Environmental Health Department (SJCEHD) approved the soil over- excavation portion of the Soil and Groundwater Remediation Work Plan as an interim remedial measure. V t� CONDOR