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URS
<br /> Mr. Robert McClellon
<br /> April 30, 2007
<br /> Page 3
<br /> Methane concentrations in the vapor extraction wells ranged from 3.4%to 8.9% in EW-1 and from 2.8%
<br /> to 12.6%in EW-2. Methane concentrations in the passive vents ranged from 2.8%to 6.3%in VP-1, from
<br /> 5.1%to 9.1%in VP-2, from 4.8%to 7.4%in VP-3, and from 3.9%to 10.6%in VP-4. Oxygen
<br /> concentrations measured at all sample locations during the quarter ranged from 0%to 21.2%. Carbon
<br /> dioxide concentrations at all sample locations measured during the quarter ranged from 0.5%to 23.5%.
<br /> Results for each probe, each extraction well, and passive vent are summarized in Table 1.
<br /> Groundwater. A groundwater contour map was prepared using the data collected on March 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 and December 15, 2006 was
<br /> shown to be from southwest to the northeast. However,the groundwater flow direction on September 29,
<br /> 2006 was shown to be from the northeast to the southwest,which is in the opposite direction as the
<br /> June 29, 2006,December 15,2006, and March 14,2007 groundwater flow directions.
<br /> VOC constituents were not detected above the analytical laboratory reporting limits in the groundwater
<br /> sample collected from MW-1. Only acetone at 6.1J(estimated)micrograms per liter(µg/L)was detected
<br /> in the groundwater sample collected from MW-2. Only chloroform was detected at 1.3 µg/L in the
<br /> groundwater sample collected from MW-3. Acetone and chloroform are known to be common laboratory
<br /> contaminants.
<br /> Of the two reported VOC constituents,primary maximum contaminant levels(MCLS) are established for
<br /> only one(chloroform at 80 µg/L by EPA and 100 µg/L by California Department of Health Services
<br /> [DHS]).For the remaining constituent,the taste and odor threshold(TOT)value for acetone is
<br /> established at 20,000 µg/L. VOC analytical results for each well are summarized in Table 2.
<br /> The following metals were not detected above the report limit of the analyses: aluminum, cadmium,
<br /> lead,mercury, selenium, silver, and thallium.The highest concentration of the remaining 10 metals are
<br /> 0.0194 milligrams per liter(mg/L) for arsenic(MW-1), 1.29 mg/L for barium(MW-2), 0.00471J mg/L
<br /> for chromium(MW-3), 0.00895)mg/L for cobalt(MW-1),0.00260J mg/L for copper(MW-1),
<br /> 4.84 mg/L for iron(MW-2), 5.14 mg/L for manganese(MW-1), 0.0131 mg/L for nickel (MW-1),
<br /> 0.0174 mg/L for vanadium(MW-3), and 0.0202 mg/L for zinc(MW-1). Of the 10 reported metals
<br /> constituents,primary MCLS are established for five constituents(arsenic at 0.01 mg/L by EPA and
<br /> 0.05 mg/L by DHS,barium at 2 mg/L by EPA and 1 mg/L by DHS, chromium[total] at 0.1 mg/L by
<br /> EPA and 0.05 mg/L by DHS, copper at 1.3 mg/L by EPA and DHS, and nickel at 0.1 mg/L by DHS).
<br /> For the remaining five metal constituents, secondary MCLS are established for three(iron at 0.3 mg/L by
<br /> EPA and DHS,manganese at 0.05 mg/L by EPA and DHS, and zinc at 5 mg/L by EPA and DHS). For
<br /> one of the two remaining constituents,the CSALDW is established for vanadium at 0.05 mg/L.For the
<br /> remaining constituent,the agricultural water quality limit is established at 0.05 mg/L for cobalt.The
<br /> dissolved metal results are summarized in Table 3.
<br /> The highest concentration of the following general mineral constituents are 350 mg/L for calcium
<br /> (MW-2); 141 mg/L for magnesium(MW-1); 33.2 mg/L for potassium(MW-2); 281 mg/L for sodium
<br /> (MW-2); and 2,210 mg/L for TDS (MW-2). The field measurements for pH ranged from 6.46 to 6.65
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