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URS
<br /> ' Mr. James Barton Page 5 of 8
<br /> California Regional Water Quality Control Board, Central Valley Region
<br /> April 29, 2010
<br /> These measurements were used to calculate the purging volume and groundwater elevation for each
<br /> well. Table 1 presents well construction details.
<br /> Approximately three well volumes were purged from each monitoring well before sampling. Purging
<br /> ' was performed using dedicated, single-use, high-density,polyethylene bailers. As each well was purged,
<br /> temperature,pH, specific conductivity, and total dissolved solids were monitored periodically to verify
<br /> that groundwater entering the well was indicative of aquifer conditions. After the purge volume was
<br /> ' reached and when the above parameters indicated that the water in each well was representative of the
<br /> aquifer, a water sample was collected from the well. Each sample was collected by lowering a new,pre-
<br /> cleaned, dedicated bailer slowly to the water line and allowing it to fill while causing minimal agitation
<br /> to the water column. Prior to collection of domestic well samples, each domestic well was purged by
<br /> turning on a hose and letting water run onto the ground until the pump started. Groundwater samples
<br /> from treatment systems were collected from labeled sample ports into pre-cleaned, laboratory-provided
<br /> ' sample containers. Once collected, the sample containers were labeled with the time and date of
<br /> collection,project and sample identification codes, sampler's initials, type of analysis to be performed,
<br /> and preservative method.
<br /> The samples were then sealed in plastic bags and stored in an ice-filled chest at approximately 4 degrees
<br /> Celsius until delivery to the laboratory. Each groundwater sample was delivered to the laboratory within
<br /> the designated holding time and was accompanied by the appropriate chain-of-custody documentation.
<br /> The groundwater samples were submitted to Curtis&Tompkins Laboratories in Berkeley, California,
<br /> and analyzed for TPH-G and TPH-D by United States Environmental Protection Agency(EPA)Method
<br /> SW8015B, and VOCs(including BTEX,MTBE,TBA, DIPE, ETBE, and TAME)by EPA
<br /> Method SW8260B.
<br /> GROUNDWATER MONITORING RESULTS
<br /> ' Groundwater elevations are provided on Figures 2-A through 2-C, and Table 2 provides groundwater
<br /> elevation data for this quarter. Field sampling data sheets are provided as Attachment A.
<br /> In E-1, TPH-G was detected for the first time, historically, at a concentration of 85 µg/L. Benzene,
<br /> toluene, ethylbenzene, total xylenes (BTEX) were also detected in E-1, for the first time historically.
<br /> These concentrations ranged from 2.2 µg/l to 17.1 µg/L.
<br /> TPH-D was detected in wells E-1,MW-3,MW-5,MW-6, MW-13,MW-14,MW-16,MW-17, MW-19,
<br /> MW-20, RW-2, and RW-3 in concentrations ranging from 51 micrograms per liter(µg/L) and 1,300
<br /> µg/L. These results have been"J" flagged. The J flag was applied because the samples exhibited
<br /> chromatographic patterns which did not resemble the"diesel"standard.
<br /> MTBE was reported in samples from wells MW-13 (0.5 µg/L), MW-17 (0.8 pg/L), and MW-19 (1.0
<br /> µg/L). In MW-16, TPH-G was detected at 170 µg/L. TPH-G,benzene,toluene, and total xylenes were
<br /> detected at the highest concentrations since the July 2003 sampling event. TPH-G was detected at the
<br /> ' highest concentration historically in MW-17, at a concentration of 82 µg/L. In MW-17, BTEX was
<br /> detected at the highest concentrations historically.
<br /> ' H:\Wprocess\RESD\Franks One Stop\QTR 10\IQMR 10 Report.doc
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