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URS • a
<br />Mr. Robert McClellon
<br />October 20, 2010
<br />Page 3 of 4
<br />the quarter ranged from 0% to 20.6 percent. Carbon dioxide concentrations measured at all sample
<br />locations during the quarter ranged from 0.5% to 30.8 percent. Results for each probe, each extraction
<br />well, and each passive vent are summarized in Table 1.
<br />Groundwater. Because the top of groundwater monitoring well MW -1 was damaged, an interpreted
<br />groundwater contour map could not be prepared at this time. Arrangements to resurvey the groundwater
<br />monitoring wells are being completed. After the groundwater monitoring wells are resurveyed, an
<br />interpreted groundwater contour map will be prepared. The groundwater flow direction results can be
<br />compared to the historical results. The groundwater flow direction historical results varies from quarter
<br />to quarter and are summarized as follows: from the northeast to the southwest (September 29, 2006),
<br />from the east to west (June 10, 2008 and September 9, 2009), from the east-southeast to the west-
<br />northwest (September 10, 2008 and December 10, 2009), from southeast to the northwest
<br />(September 20, 2007), from the southwest to the northeast (June 29, 2006, December 15, 2006,
<br />March 14, 2007, December 9, 2008, March 11, 2009, March 9, 2010, and June 8, 2010), from the west-
<br />southwest to the east-northeast (June 14, 2007, December 13, 2007, March 13, 2008, and June 10,
<br />2009).
<br />The following seven metals were not detected above the analyses reporting limit: aluminum, cadmium,
<br />copper, mercury, selenium, silver and thallium. The highest detected concentration of the remaining
<br />10 metals are 0.0202 milligrams per liter (mg/L) for arsenic (MW -1), 1.16 mg/L for barium (MW -2),
<br />0.00423J mg/L for chromium (MW -3),0.00600J mg/L for cobalt (MW -1), 0.551 mg/L for iron
<br />(MW -2),0.00783J mg/L for lead (MW -2), 3.31 mg/L for manganese (MW -1), 0.00898J mg/L for nickel
<br />(MW -2), 0.0187 mg/L for vanadium (MW -3) and 0.0126 mg/L for zinc (MW -1). The highest TDS
<br />concentration of 2,290 mg/L was found in MW -2. The field measurements for pH ranged from 6.24 to
<br />6.56, and specific conductance ranged from 1,800 to 3,400 micromhos (µmhos).
<br />Of the 10 reported metals constituents, primary maximum contaminant levels (MCLS) are established
<br />for five 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, lead at 0.015 mg/L by EPA and DHS, and nickel at 0.1 mg/L by DHS). For the
<br />remaining five metal constituents, secondary MCLs are established for three (iron at 0.3 mg/L by EPA
<br />and DHS, manganese at 0.05 mg/L by EPA and DHS and zinc at 5 mg/L by EPA and DHS). For the
<br />two 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 Limits 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. The dissolved metal results, TDS results, and the
<br />field measurements are summarized in Table 2.
<br />The analytical report is provided as Attachment 2.
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