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Mr. Robert McClellon
<br />July 29, 2010
<br />Page 3
<br />Carbon dioxide concentrations measured at all sample locations during the quarter ranged from 0.7% to
<br />23.1%. 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 June 8,
<br />2010 (Figure 2). The groundwater flow direction is to the northeast at a gradient of 0.00029. For
<br />comparison, the groundwater flow direction varies from the northeast to the southwest
<br />(September 29, 2006), from the east to west (June 10, 2008, and September 9, 2009), from the east-
<br />southeast to the west-northwest (September 10, 2008, and December 10, 2009), from southeast to the
<br />northwest (September 20, 2007), from the southwest to the northeast (June 29, 2006, December 15,
<br />2006, March 14, 2007, December 9, 2008, March 11, 2009, and March 9, 2010), from the west-
<br />southwest to the east-northeast (June 14, 2007, December 13, 2007, March 13, 2008, and June 10, 2009).
<br />The following metals were not detected above the analyses reporting limit: aluminum, cadmium,
<br />mercury, selenium, silver and thallium. The highest detected concentration of the remaining 11 metals
<br />are 0.0108 milligrams per liter (mg/L) for arsenic (MW -1), 1.26 mg/L for barium (MW -2),
<br />0.00459J mg/L for chromium (MW -3), 0.0101 mg/L for cobalt (MW -2), 0.00236J for copper (MW -2),
<br />0.750 mg/L for iron (MW -2), 0.00805J mg/L for lead (MW -2), 2.87 mg/L for manganese (MW -2),
<br />0.0236 mg/L for nickel (MW -2), 0.0191 mg/L for vanadium (MW -3) and 0.0218 mg/L for zinc (MW -2).
<br />The highest TDS concentration of 2,250 mg/L was found in MW -2. The field measurements for pH
<br />ranged from 6.49 to 6.72, and specific conductance ranged from 1,730 to 3,190 micromhos (µmhos).
<br />Of the 11 reported metals constituents, primary maximum contaminant levels (MCLS) are established for
<br />six constituents (arsenic at 0.01 mg/L by EPA and 0.05 mg/L by 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 and
<br />nickel at 0.1 mg/L by DHS). For the remaining five metal constituents, secondary MCLs are established
<br />for three (iron at 0.3 mg/L by EPA and DHS, manganese at 0.05 mg/L by EPA and DHS, and zinc at
<br />5 mg/L by EPA and DHS). For the two remaining constituents, the California State Action Level for
<br />Drinking Water is established for vanadium at 0.05 mg/L. For the remaining constituent, the Agricultural
<br />Water Quality Limits is established at 0.05 mg/L for cobalt. Secondary MCLs are established for TDS at
<br />500 mg/L by EPA and DHS and specific conductance at 900 µmhos by EPA. The dissolved metal
<br />results, TDS results, and the field measurements are 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, lead, manganese, nickel, vanadium, and
<br />zinc) and TDS were detected above the analytical reporting limits in the groundwater samples collected
<br />on June 8, 2010. Of these constituents, five (arsenic, barium, iron, manganese, and TDS) were above
<br />their established regulatory levels. Because four of the metal results and TDS were above their
<br />established regulatory levels, URS plans to continue quarterly monitoring of these metals and TDS.
<br />HWprocess\25532\WorldEntetptise\Quarterly Rpt\20102Q I OQQ 10_072910.dx
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