|
6
<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 serm-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 Technology supervised the advancement of four soil
<br /> bonngs (SB-1, SB-2, SB-3, and SB-4) on February 29, 1996 to depths of approximately 16 to 26
<br /> feet bgs Total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, and
<br /> xylenes (BTE3) were detected above method detection limits at low to moderate concentrations
<br /> in samples collected at depths between 10 and 15 feet bgs in bonngs SB-1, SB-2, and SB-3 A
<br /> detailed discussion of this subsurface investigation can be found in Smith Technology's
<br /> "Subsurface Investigation Report, " dated April 30, 1996
<br /> GROUNDWATER MONITORING AND SAMPLING
<br /> . Smith Technology personnel performed groundwater monitoring and sampling on December 24,
<br /> 1997 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 servicing
<br /> the passive skimmer placed in well MW2
<br /> Static groundwater elevations were measured in each morutonng well on December 24, 1997
<br /> Groundwater was measured at an average of approximately 11 84 feet below grade A
<br /> groundwater gradient map was created with the December 24, 1997 data using a computer
<br /> kriging program The gradient map, presented as Figure 2, depicts a south-southeasterly
<br /> groundwater gradient averaging 0 006 ft/ft or approximately 31 7 feet/nule Fluid level
<br /> measurements indicate groundwater flow direction beneath the site during this reporting period is
<br /> generally consistent with historical data The water table has risen an average of 1 00 foot since
<br /> the previous measurements were collected in October 1997 Groundwater morutonng data are
<br /> summarized in Table 1
<br /> On December 24, 1997, groundwater samples were collected by Smith Technology from
<br /> monitoring wells MW 1, MW2, MW3, and MW5 Groundwater samples were collected from the
<br /> momtonng wells after stabilization of pH, electrical conductivity (EC), and temperature All wells
<br /> monitored were purged and sampled according to Smith Technology's Quality Assurance/Quality
<br /> Control Plan on file with the PHS/EHD A minimum of four casing volumes of water were
<br /> . removed from each sampled well A dedicated disposable bailer was used to collect each water
<br /> 943341QUARTLYI4QR-1997 DOC 2 � �
<br />
|