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<br /> Fourth Quarter 2004 Groundwater Monitoring Report
<br /> Boyett Petroleum,419 S.Main,Manteca,CA
<br /> Page 3
<br /> . Table 2: Historical Groundwater Gradients
<br /> Date Approximate Flow Direction Monitoring Wells Utilized for Groundwater
<br /> and Groundwater Gradient Gradient Calculations
<br /> Se tember 1, 1999 0.002 ft./ft.-Northwest
<br /> December 10, 1999 0.0010 ft-/ft.-Narthwest MW-1, MW-2,MW-3
<br /> March 27, 2000 0.016 ft./ft.-Northeast MW-1,MW-2,MW-3
<br /> June 23,2000 0.0021 ft./ft.- Southeast MW-1,MW-2,MW-3
<br /> September 8,2000 0.004 ft./ft.- Southeast MW-1,MW-2,MW-3
<br /> December 2000"* 0.0021 ft./ft.- Southwest MW-2,MW-6,MW-8
<br /> March 5,2001* 0.0061 ft./ft.-Northeast MW-2, MW-6,MW-8
<br /> June 4,2001* 0.005 ft./ft.-Northwest MW-2,MW-6,MW-8
<br /> September 10,2001* 0.0072 ft./ft.-Northwest MW-2,MW-6, MW-8
<br /> September 26, 2002' 0.0058 ft./ft-Southwest MW-2,MW-6,MW-8
<br /> December 27,2002 0.0036 ft./ft.-Northeast MW-2,MW-6,MW-8
<br /> March 21, 2003 0.0008 ft./ft. -South MW-2,MW-6,MW-8
<br /> June 25,2003 0.0085 ft./ft.- Southwest MW-2,MW-6,MW-8
<br /> July 22,2003 0.0094 ft./ft.- Southwest MW-2,MW-6,MW-8
<br /> August 19, 2003 0.0089 ft-/ft.- Southwest MW-2,MW-6, MW-8
<br /> September 30,2003 Not Calculated MW-2 dry; MW-6 and MW-8 purged dr
<br /> October 31, 2003 Not Calculated Lack of Data
<br /> November 26,2003 0.0315 ft./ft.- Southwest MW-3,MW4R,MW-10
<br /> December 31,2003 0.0057 ft./ft. -North MW-2,MW-6,MW-8
<br /> March 4, 2004 0.0048 ft./ft.-Northeast MW-2,MW-6,MW-8
<br /> June 24,2004 0.0217 ft./ft. -South MW-2, MW-6,MW-8
<br /> September 28,2004 Not Calculated MW-2 and MW-6 were dr
<br /> December 29,2004 0.0036 ft./ft.-North MW-2, MW-6,MW-8
<br /> • _ Date interred
<br /> 2 Condor began conducting quarterly groundwater monitoring at the Site
<br /> '- Well collars surveyed;elevations are referenced to NAVD88 datum NGS Benchmark HS 4486
<br /> *- Condor recalculated gradient
<br /> LABORATORY ANALYTICAL RESULTS
<br /> The groundwater samples collected from the monitoring wells were analyzed for benzene, toluene, ethyl
<br /> benzene, total xylenes (BTEX), and selected gasoline oxygenates/additives by EPA Method 826013, and
<br /> for total petroleum hydrocarbons quantified as gasoline (TPH-G) by EPA Method 8015M by Argon
<br /> Laboratories of Ceres, California. The selected oxygenates/additives included MTBE, ethanol (EtOH),
<br /> tertiary-butanol (TBA), di-isopropyl ether(DIPE), ethyl tertiary-butyl ether(ETBE), tertiary-amyl methyl
<br /> ether(TAME), 1,2-dichloroethane (1,2-DCA), and 1,2-dibromoethane(EDB).
<br /> The laboratory analytical results for the fourth quarter 2004 quarterly groundwater monitoring event are
<br /> presented in Table 3, on the next page. A trap presenting MTBE isoconcentration contours in
<br /> groundwater is included as Figure 5, attached.
<br /> i CONDO
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