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I I
<br /> discussion of the initial subsurface investigation can be found in RESNA's "Interim Problem
<br /> Assessment Report, Soil and Groundwater Contamination,"dated June 8, 1992
<br /> In July 1994, a RESNA field geologist observed the drilling of four additional groundwater
<br /> monitoring wells (MW4, MW5, MW6, and MW7) at the site to further characterize subsurface
<br /> conditions Groundwater samples collected from these additional wells contained no detectable
<br /> petroleum hydrocarbons A detailed discussion of the Phase 2 Subsurface Investigation can be
<br /> found in RESNA's "Summary Report, July 1994 Investigation,"dated August 26, 1994
<br /> In PHS/EHD correspondence dated March 1995, regulatory approval was given to sample wells
<br /> MW3 and MW5 and wells MW4, MW6 and MW7 on an alternating semi-annual basis MW 1 and
<br /> MW2 were to be sampled every quarter, conditions permitting
<br /> To further define the extent of residual soil contamination in the vicinity of the former
<br /> underground fuel storage tank (UST), Smith Environmental supervised the advancement of four
<br /> soil bonngs (SB-1, SB-2, SB-3, and SB-4) on February 29, 1996 to depths of approximately 16
<br /> to 26 feet below ground surface (bgs) Total petroleum hydrocarbons as gasoline (TPHg),
<br /> benzene, toluene, ethylbenzene, and xylenes (BTEX) were detected above method detection limits
<br /> at low to moderate concentrations in samples collected at depths between 10 and 15 feet bgs in
<br /> borings SB-1, SB-2, and SB-3 A detailed discussion of this subsurface investigation can be
<br /> found in Smith Technology's"Subsurface Investigation Report, " dated April 30, 1996
<br /> GROUNDWATER MONITORING AND SAMPLING
<br /> Smith Technology personnel performed groundwater monitoring and sampling on December 5,
<br /> 1996 Field work consisted of measuring the depth-to-water in wells MW1, MW2, MW3, MW4,
<br /> MW5, MW6, and MW7, using an electronic water/product interface probe to determine if free
<br /> product was present, purging and sampling wells MW1, MW2, MW3, and MW5, and subjectively
<br /> evaluating collected water samples for the presence of petroleum hydrocarbon constituents
<br /> Static groundwater elevations were measured in each monitoring well on December 5, 1996
<br /> Groundwater was measured at approximately 12 feet below grade The groundwater gradient
<br /> map was created with the December 5, 1996 data using a computer kriging program The
<br /> gradient map, presented as Figure 2, depicts a southwesterly groundwater gradient averaging
<br /> 0 004 ft/ft or approximately 23 feet/mile Fluid level measurements indicate groundwater flow
<br /> direction beneath the site during this reporting period is generally consistent with historical data
<br /> Groundwater has risen an average of 0 77 feet since the previous measurements were collected in
<br /> September 1996 The electronic water/product interface probe employed at the site, with an
<br /> accuracy of 0 01 foot, did not detect measurable free product in well MW2 Groundwater
<br /> monitoring data are summarized in Table 1
<br /> On December 5, 1996 groundwater samples were collected from monitoring wells MW1, MM2,
<br /> MW3, and MW5 Samples were collected after stabilization of pH, electrical conductivity (EC),
<br /> • and temperature All wells monitored were purged and sampled according to Smith Technology's
<br /> 9433*QUAR'f LYWQR 19%DOC 2
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<br /> SMTH
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