|
C\YZ• A S S O C I A T E S I N C
<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 Technology supervised the advancement of four soil
<br /> borings (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 (BTEX) were detected above method detection limits at low to moderate concentrations
<br /> in samples collected at depths between 10 and 15 feet bgs 1n borings 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 /> ATC personnel performed groundwater monitoring and sampling on March 12, 1998 Field work
<br /> consisted of measuring the depth-to-water in wells MW1, MW2, MW3, MW4, MW5, MW6, and
<br /> MW7, using an electronic water/product interface probe to determine if free product was present,
<br /> purging and sampling wells MW1, MW4, MW6, and MW7, and servicing the passive skimmer
<br /> placed in well MW2
<br /> Static groundwater elevations were measured in each monitoring well on March 12, 1998
<br /> Groundwater was measured at an average of approximately 9 46 feet below grade A
<br /> groundwater gradient map was created with the March 12, 1998 data using a computer knging
<br /> program The gradient map, presented as Figure 2, depicts a south-southeasterly groundwater
<br /> gradient averaging 0 03 ft/ft or approximately 158 feet/mile Fluid level measurements indicate
<br /> groundwater flow direction beneath the site during this reporting period is generally consistent
<br /> with historical data The water table has risen an average of 2 39 feet since the previous
<br /> measurements were collected in December 1997 The March 1998 measurements also indicate
<br /> groundwater beneath the site is at its highest elevation since the monitoring program was initiated
<br /> in March 1992 Groundwater monitoring data are summarized in Table 1
<br /> On March 12, 1998, groundwater samples were collected by ATC from monitoring wells MWI,
<br /> MW4, MW6, and MW7 Groundwater samples were collected from the monitoring wells after
<br /> stabilization of pH, electrical conductivity (EC), and temperature All wells monitored were
<br /> purged and sampled according to Smith Technology's Quality Assurance/Quality Control Plan on
<br /> file with the PHS/EHD A minimum of eight casing volumes of water were removed from each
<br /> sampled well A dedicated disposable bailer was used to collect each water sample Purge water
<br /> 943341Qi1ARTLYIIQR-1998 DOC 2
<br />
|