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<br /> VkT4;
<br /> ATC Associates Inc.
<br /> 1117 Lone Palm Avenue, Suite 201
<br /> Modesto, California 95351
<br /> 209-579-2221
<br /> Fax:209-579-2222
<br /> ASSOCIATES INC .
<br /> encountered at a depth of approximately 15-16 feet below ground surface (bgs). During the
<br /> advancement of the soil borings, soil samples were collected at a depth of 4-5 feet above static
<br /> water and submitted for laboratory analysis. Samples were found to contain petroleum
<br /> hydrocarbons. Laboratory analysis of groundwater samples collected from the developed wells
<br /> indicated that gasoline constituents were present in groundwater above laboratory method
<br /> detection limits. In March of 1992, groundwater elevations measured within the monitoring
<br /> showed that groundwater flow direction was towards the south. A detailed discussion of the
<br /> initial subsurface investigation can be found in RESNA's "Interim Problem Assessment Report,
<br /> Soil and Groundwater Contamination", dated June 8, 1992.
<br /> Pursuant to SJCEHD correspondence dated June 11, 1992, RESNA investigated an unused on-
<br /> site water production well. The well was located north of MW1 as shown on Figure 2. On July
<br /> 16, 1992, a video logging performed on the well revealed that the 8-inch diameter well extended
<br /> to a total depth of approximately 155 feet bgs with casing extending from the surface to
<br /> approximately 102 feet bgs. On December 1992, the well's overlying concrete pad and
<br /> associated fill were excavated to verify the condition of the annular seal. No annular seal was
<br /> observed (at the surface) and the casing was observed to be in generally poor condition. Due
<br /> to the lack of well construction data and uncertainty in condition of the well seal, it was
<br /> recommended the facility well be abandoned and destroyed. On February 2, 1993, the well was
<br /> destroyed under the supervision of SJCEHD staff in accordance with State guidelines for well
<br /> destruction.
<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 characterize subsurface
<br /> conditions. Groundwater samples collected from these additional wells contained no detectable
<br /> petroleum hydrocarbons. A detailed discussion of the subsurface investigation can be found in
<br /> RESNA's "Summary Report, July 1994 Investigation," dated August 26, 1994.
<br /> In March 1995, the SJCEHD granted permission to sample wells MW3, MW4, MW5, MW6, and
<br /> MW7 on an alternating semi-annual basis. Wells MW1 and MW2 were to be sampled every
<br /> quarter, conditions permitting.
<br /> On February 29, 1996, Smith Technology supervised the advancement of four soil borings, SB-
<br /> 1, SB-2, SB-3, and SB-4, to depths of approximately 16 to 26 feet bgs to evaluate the extent of
<br /> residual soil contamination near the former UST. Total petroleum hydrocarbons as gasoline
<br /> (TPHg), benzene, toluene, ethylbenzene, and xylenes (BTEX) were detected at low to moderate
<br /> concentrations in samples collected at depths between 10 and 15 feet bgs in borings SB-1, SB-
<br /> 2, and SB-3. A detailed discussion of this subsurface investigation can be found in Smith
<br /> Technology's "Subsurface Investigation Report", dated April 30, 1996.
<br /> In June 2001, five soil borings, SB-11, SB-12, SB-13, SB-14, and SB-15, were advanced using
<br /> truck-mounted GeoprobeO narrow diameter, direct push technology to evaluate the extent of
<br /> impacted soil and groundwater at the site. Borings SB-11, SB-12, and SB-15 were advanced to
<br /> first encountered water, at depths between 5 to 19 feet bgs, and soil borings SB-13 and SB-14
<br /> were advanced to depths of approximately 26 to 27 feet bgs. Petroleum hydrocarbon
<br /> constituents including TPHg, total petroleum hydrocarbons as diesel (TPHd), benzene, ethyl
<br /> benzene, and xylenes were detected in soil samples collected from boring SB-11 at 5 feet bgs
<br /> and in boring SB-14 at depths of 8 and 20 feet bgs. Concentrations of petroleum hydrocarbons
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