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<br /> URS
<br /> Mr. Robert McClellon
<br /> January 31,2008
<br /> Page 3
<br /> extraction wells were 0.3% in EW-1 and 0.7% in EW-2. The methane concentrations measured in the
<br /> passive vents were 0.4% in VP-1, 3.0% in VP-2, 5.0% in VP-3,and 4.2% in VP-4. The oxygen concen-
<br /> tration measured at all sample locations during the quarter ranged from 2.2%to 20.8%. The carbon
<br /> dioxide concentration at all sample locations measured during the quarter ranged from 0.1%to 20.6%.
<br /> The results for each probe,each extraction well, and each passive vent are summarized in Table 1.
<br /> Groundwater.An interpreted groundwater contour map was prepared using the data collected on
<br /> December 13, 2007 (Figure 2). The groundwater flow direction is to the east-northeast at a gradient of
<br /> 0.00167. For comparison,the groundwater flow direction varies from the southeast to the northwest
<br /> (September 20,2007),varies from the west-southwest to the east-northeast(June 14,2007), from the
<br /> southwest to the northeast(June 29,2006,December 15, 2006 and March 14, 2007), from the northeast
<br /> to the southwest(September 29,2006).
<br /> The following metals were not detected above the analyses reporting limit: aluminum,mercury,
<br /> selenium, silver, and thallium. The highest detected concentration of the remaining 12 metals are
<br /> 0.0276 milligrams per liter(mg/L)for arsenic(MW-1), 1.37 mg/L for barium(MW-2), 0.00358J mg/L
<br /> for cadmium(MW-2), 0.00338J mg/L for chromium(MW-3), 0.00972)mg/L for cobalt(MW-1),
<br /> 0.00314J mg/L for copper(MW-2), 11.2 mg/L for iron(MW-2), 0.0354 mg/L for lead(MW-2),
<br /> 4.76 mg/L for manganese(MW-1), 0.0176 mg/L for nickel (MW-1), 0.0156 mg/L for vanadium
<br /> (MW-3), and 0.0236 mg/L for zinc(MW-1). The highest TDS concentration of 2,250 mg/L was found
<br /> in MW-2. Field measurements for pH ranged from 6.62 to 6.97, and specific conductance ranged from
<br /> 1,505 to 2,826 micromhos(µmhos).
<br /> Of the 12 reported metals constituents,primary maximum contaminant levels(MCLS)are established
<br /> for 7 constituents(arsenic at 0.01 mg/L by EPA and 0.05 mg/L by the California Department of Health
<br /> Services [DHS], barium at 2 mg/L by EPA and 1 mg/L by DHS, chromium [total] at 0.1 mg/L by EPA
<br /> and 0.05 mg/L by DHS, copper at 1.3 mg/L by EPA and DHS, lead at 0.015 mg/L by EPA and DHS,
<br /> nickel at 0.1 mg/L by DHS and thallium at 0.002 mg/L by EPA and DHS). For the remaining five
<br /> metal constituents, secondary MCLs are established for three(iron at 0.3 mg/L by EPA and DHS,
<br /> manganese at 0.05 mg/L by EPA and DHS, and zinc at 5 mg/L by EPA and DHS). For one of the two
<br /> remaining constituents,the California State Action Level for Drinking Water is established for
<br /> vanadium at 0.05 mg/L. For the remaining constituent,the Agricultural Water Quality Limit is
<br /> established at 0.05 mg/L for cobalt. Secondary MCLs are established for TDS at 500 mg/L by EPA and
<br /> DHS and specific conductance at 900 µmhos by EPA. Dissolved metal results,TDS results, and field
<br /> measurements are summarized in Table 2.
<br /> The analytical report is provided as Attachment 2.
<br /> CONCLUSIONS AND RECOMMENDATIONS
<br /> Twelve metals(arsenic,barium cadmium, chromium, cobalt, copper, iron, lead,manganese, nickel,
<br /> vanadium, and zinc)and TDS were detected above the analytical reporting limits in the groundwater
<br /> samples collected on December 13, 2007. Of these constituents, six(arsenic,barium, iron, lead,
<br /> manganese, and TDS)were above their established regulatory levels. Because five of the metal results
<br /> and TDS were above their established levels,URS plans to continue quarterly monitoring for these
<br /> metals and TDS.
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