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Mr. Robert McClellon
<br />Supervisor R.E.H.S.
<br />April 6, 2009 Page 3 of 4
<br />measured in the passive vents were 1.6% in VP -1, 4.3% in VP -2, 4.8% in VP -3, and 2.7 % in VP -4.
<br />Oxygen concentrations measured at all sample locations during the quarter ranged from 0% to 20.7
<br />percent. Carbon dioxide concentrations measured at all sample locations during the quarter ranged from
<br />0.8% to 21.9 percent. Results for each probe, each extraction well, and each passive vent are summarized
<br />in Table 1.
<br />Groundwater. An interpreted groundwater contour map was prepared using the data collected on March
<br />11, 2009 (Figure 2). The groundwater flow direction is to the northeast at a gradient of 0.0026. For
<br />comparison, the groundwater flow direction varies from the east-southeast to the west-northwest
<br />(September 10, 2008), from the east to west (June 10, 2008), from southeast to the northwest (September
<br />20, 2007), from the west-southwest to the east-northeast (June 14, 2007, December 13, 2007, and
<br />March 13, 2008), from the southwest to the northeast (June 29, 2006, December 15, 2006, March 14,
<br />2007, and December 9, 2008), and from the northeast to the southwest (September 29, 2006).
<br />The following metals were not detected above the analyses reporting limit: aluminum, cadmium,
<br />mercury, selenium and silver. The highest detected concentration of the remaining 12 metals are 0.0106
<br />milligrams per liter (mg/L) for arsenic (MW -1), 0.962 mg/L for barium (MW -2),0.00369J mg/L for
<br />chromium (MW -3), 0.00532J mg/L for cobalt (MW -1), 0.00384J mg/L for copper (MW -2), 2.35 mg/L
<br />for iron (MW -2), 0.00740J mg/L for lead (MW -2), 3.28 mg/L for manganese (MW -1), 0.0113 mg/L for
<br />nickel (MW -1), 0.00539J mg/L for thallium (MW -1), 0.0161 mg/L for vanadium (MW -3) and 0.0233
<br />mg/L for zinc (MW -2). The highest TDS concentration of 2,290 mg/L was found in MW -2. The field
<br />measurements for pH ranged from 6.59 to 6.84, and specific conductance ranged from 1,920 to 3,350
<br />micromhos (µmhos).
<br />Of the 12 reported metals constituents, primary maximum contaminant levels (MCLs) are established for
<br />seven 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,
<br />nickel at 0.1 mg/L by DHS, and thallium at 0.002 mg/L by EPA and DHS). For the remaining five metal
<br />constituents, secondary MCLs are established for three (iron at 0.3 mg/L by EPA and DHS, manganese
<br />at 0.05 mg/L by EPA and DHS and zinc at 5 mg/L by EPA and DHS). For the two remaining
<br />constituents, the California State Action Level for Drinking Water is established for vanadium at 0.05
<br />mg/L. For the remaining constituent, the Agricultural Water Quality Limits is established at 0.05 mg/L
<br />for cobalt. Secondary MCLs are established for TDS at 500 mg/L by EPA and DHS and specific
<br />conductance at 900 µmhos by EPA. The dissolved metal results, TDS results, and the 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, chromium, cobalt, copper, iron, lead, manganese, nickel, thallium,
<br />vanadium and zinc) and TDS were detected above the analytical reporting limits in the groundwater
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