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' Fourth Quarter,2002 Quarterly Groundwater Monitoring Report
<br /> Boyett Petroleum,419 S.Main,Manteca,CA
<br /> Page 3
<br /> Table 2
<br /> Groundwater Elevation Data(December 27, 2002)
<br /> Monitoring Well I TOG Elevation Screened Depth to Groundwater
<br /> Interval b s Groundwater Elevation
<br /> MW-1 36.16 13-33 19.33 16.83
<br /> MW-2 35.97 15-25 19.16 16.81
<br /> MW-3 36.18 15-25 19.68 16.50
<br /> MWA 35.38 9-24 18.62 16.76
<br /> MW-5 35.93 10-30 DRY NM
<br />' MW-6 36.07 10-25 19.06 17.01
<br /> MW-7 36.42 10-25 19.98 16.44
<br /> MW-8 36.43 10-25 1 19.85 16.58
<br /> MW-9 3 5.95 40-501 18.83 1 17.12
<br /> 'TOC Elevation: Elevations are referenced to NAD83 datum by post-processing the base station against the Condor Stockton (CNDR)CORS
<br /> Station NGS Benchmark HS 4486,elevation 35.03 feet.
<br /> 'Groundwater Elevation:Elevations are measured from the top of the well casings and are referenced to the benchmark indicated above.
<br /> All measurements are in feet.
<br />' NM=Not measured
<br /> The groundwater elevation contours (Figure 3, Attachment A) estimated using depth to water
<br /> measurements from monitoring wells MW-1, MW-2, MW-3, MW-6, MW-7, and MW-8 and well survey
<br /> data collected by Condor indicate a relatively gentle groundwater gradient to the north/northeast. An
<br /> estimated groundwater gradient of 0.0036 ft/ft towards the northeast was calculated using water level data
<br /> from monitor wells MW-2, MW-6, and MW-8. The current north/northeast gradient represents a reversal
<br /> . from that reported in the Third Quarter Monitoring Report, dated January 16, 2003. Historic groundwater
<br /> gradients reported for the site have been highly variable (Table 3, below).
<br /> Table 3
<br /> Historic Groundwater Gradients
<br /> Date Approximate Flow Direction Monitor Wells Utilized for Groundwater
<br /> and Groundwater Gradient Gradient Calculations
<br /> September 1, 1999 0.002 ft./ft.—Northwest
<br /> December 10, 1999 0.0010 ft./ft.-Northwest MW-1, MW-2,MW-3
<br /> March 27,2000 0.0 16 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 /> 1 December 20001•* 0.0021 ft./ft.—West/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.—West(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 /> ' Date inferred
<br /> 1 Z— Condor began conducting quarterly groundwater monitoring at the site
<br /> '— Well collars surveyed;elevations are referenced to NAD83 datum by post-processing the base station against the Condor Stockton(CNDR)
<br /> CORS Station NGS Benchmark HS 4486,elevation 35.03
<br /> "- Condor recalculated gradient
<br /> LABORATORY ANALYTICAL RESULTS
<br /> w. A11111111k Tl1P arrnindvArstPr cmm�lPc 1vPYP nnnN�7.-r1 f N 11an�ana tn1.,P.,R I.o, �o.,v
<br /> -- O'--"-'— ---- --'-'t--•• .•—-- a-1.1`--- +va V...a...m-, �va�wv�iv, —.7. v�.a1c.�.i1�., [ Aµ LV iGil 4%j ll.•11L.7 `L 11.:.AJ
<br /> � and selected gasoline oxygenates/additives by EPA Method 8260B, and total petroleum hydrocarbons
<br /> quantified as gasoline (TPH-G) by Method 8015M by Argon Laboratories, Inc. of Ceres, California. The
<br />' selected oxygenates/additives included methyl tert butyl ether (MTBE), ethanol (EtOH), tertiary-butanol
<br /> a CONDOR
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