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URS
<br /> Mr. Robert McClellon
<br /> July 13, 2007
<br /> Page 3
<br /> The methane concentration in the vapor extraction wells ranged from 3.0%to 6.7% in EW-1 and from
<br /> 9.3%to 13.4% in EW-2. The methane concentrations in the passive vents ranged from 6.7%to 8.0% in
<br /> VP-1,from 4.3%to 8.9% in VP-2, from 1.5%to 9.4% in VP-3,and from 7.2%to 9.3% in VP-4. The
<br /> oxygen concentration measured at all sample locations during the quarter ranged from 0%to 21.0%.
<br /> The carbon dioxide concentration at all sample locations measured during the quarter ranged from
<br /> 0.5%to 26.2%. The results for each probe,each extraction well,and each passive vent are summarized
<br /> in Table 1.
<br /> Groundwater. A groundwater contour map was prepared using the data collected on June 14, 2007
<br /> (Figure 2). The groundwater flow direction was shown to be from the west-southwest to the east-
<br /> northeast. For comparison,the groundwater flow direction on June 29, 2006,December 15,2006, and
<br /> March 14,2007 was shown to be from southwest to the northeast.However,the groundwater flow
<br /> direction on September 29,2006 was shown to be from the northeast to the southwest,which is in the
<br /> opposite direction as the June 29,2006;December 15,2006;March 14,2007; and June 14,2007
<br /> groundwater flow direction.
<br /> The following metals were not detected above the analyses reporting limit: aluminum, cadmium, lead,
<br /> mercury, selenium, and silver. The highest detected concentration of the remaining 11 metals are
<br /> 0.0285 milligrams per liter(mg/L) for arsenic(MW-1), 1.28 mg/L for barium(MW-2), 0.00322J mg/L
<br /> for chromium(MW-3), 0.0114 mg/L for cobalt(MW-1), 0.00260J mg/L for copper(MW-2), 0.805
<br /> mg/L for iron(MW-2), 5.57 mg/L for manganese(MW-1), 0.0127 mg/L for nickel(MW-1), 0.0149
<br /> mg/L for thallium(MW-1), 0.0164 mg/L for vanadium(MW-3), and 0.0183 mg/L for zinc(MW-2).
<br /> The highdst TDS concentration of 2,220 mg/L was found in MW-2. The field measurements for pH
<br /> ranged from 6.60 to 6.83, and specific conductance ranged from 1,554 to 3,080 micromhos (µmhos).
<br /> Of the 11 reported metals constituents,primary maximum contaminant levels(MCLs)are established
<br /> for 6 constituents(arsenic at 0.01 mg/L by EPA and 0.05 mg/L by DHS,barium at 2 mg/L by EPA and
<br /> 1 mg/L by California Department of Health Services [DHS], chromium [total] at 0.1 mg/L by EPA and
<br /> 0.05 mg/L by DHS, copper at 1.3 mg/L by EPA and DHS,nickel at 0.1 mg/L by DHS and thallium at
<br /> 0.002 mg/L by EPA and DHS). For the remaining five metal constituents, secondary MCLs are
<br /> established for three(iron at 0.3 mg/L by EPA and DHS,manganese at 0.05 mg/L by EPA and DHS,
<br /> and zinc at 5 mg/L by EPA and DHS). For one of the two remaining constituents,the California State
<br /> Action Level for Drinking Water is established for vanadium at 0.05 mg/L. For the remaining
<br /> constituent,the Agricultural Water Quality Limits is established at 0.05 mg/L for cobalt. Secondary
<br /> MCLs are established for TDS at 500 mg/L by EPA and DHS and specific conductance at 900 µmhos
<br /> by EPA. The dissolved metal results, general mineral results,and the field measurements are
<br /> summarized in Table 2.
<br /> The analytical report is provided as Attachment 2.
<br /> CONCLUSIONS AND RECOMMENDATIONS
<br /> Eleven metals(arsenic,barium chromium, cobalt,copper, iron,manganese,nickel,vanadium,thallium
<br /> and zinc)and TDS were detected above the analytical reporting limits in the groundwater samples
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