|
Quarterly Groundwater Sampling
<br /> As part of the groundwater monitoring program, groundwater samples were obtained from
<br /> ' monitoring wells MW-3, MW-4, MW-5, MW-6, MW-7, MW-9, MW-10, MW-11, and vapor wells
<br /> which contain water (VW-1, VW-3, VW-5A, VW-6A, and VW-6B) on February 18, 1999
<br /> Groundwater samples were obtained by Earth Management Company (EMC) and delivered in a
<br /> ' chilled state, in an ice chest, following strict Cham-of-Custody procedures to a state certified
<br /> laboratory and analyzed for volatile aromatic compounds of benzene, toluene, ethylbenzene,
<br /> and xylenes by EPA method 8020 for total petroleum hydrocarbons (TPH) by EPA method 8015
<br /> ' modified, and for oxygenates (including MTBE) by EPA method 8260
<br /> A summary of historic analytical sampling results are provided in Table 1, and copies of the
<br /> ' laboratory analytical reports for this reporting period are included in Appendix A
<br /> Highest dissolved TPH, benzene, and MTBE concentrations recorded during the 1 st quarter 1999
<br /> ' were 88,000 micrograms per liter(ug/L) for VW-3, 22,000 ug/L for VW-3, and 8,200 ug/L for VW-
<br /> 6B, respectively TPH, benzene, and MTBE distributions in groundwater during this reporting
<br /> period are presented as isoconcentration maps in Figures 3, 4 and 5, respectively
<br /> ' Since the thirduarter of 1997
<br /> q , Thrifty has sampled for the requested oxygenates ds-isopropyl ether,
<br /> ethanol, ethyl-tert butyl ethyl, methanol, tert-amyl methyl ether, tert-butanol, and methyl tert-butyl
<br /> ether (MTBE) by method 8260 Analytical results are included in Appendix A
<br /> Summary and Recommendations
<br /> ' On February 18, 1999, quarterly groundwater monitoring was performed in all existing monitoring
<br /> wells,and vapor wells which contained sufficient measurable groundwater at Former Thrifty Oil Co
<br /> Station #172 Free petroleum hydrocarbons was not detected in any of the monitoring wells, but
<br /> up to 22,000 ug/L dissolved benzene, and 8,200 ug/L MTBE were detected in monitoring wells VW-
<br /> 3, and VW-6B, respectively
<br /> On March 31 and April 1, 1999 Thrifty retained the services of The Park Corporation to complete
<br /> the following tasks as outlined in the approved workplan dated March 1, 1999, by Thrifty Oil Co
<br /> A groundwater aquifer pump test was conducted, and a groundwater monitoring well (MW-12)
<br />' installed to 73 feet below surface grade to vertically delineate hydrocarbon constituents beneath the
<br /> site Monitoring well MW-7 was resurged and bailed to create a groundwater flow into this well
<br /> Park also repaired all monitoring wells surfaces, connecting the monitoring wells to the remediation
<br /> piping within the monitoring well boxes, and bolting down the monitoring well covers
<br />' This above work was completed at the requested of the San Joaquin Public Health Services/
<br /> Environmental Health Division Mr Mike Infurna, Jr a representative of this agency, was on site
<br /> ti to witness the progress of the work
<br />
|