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<br /> b 1117 Lone Palm Avenue, Suite B
<br /> Modesto, CA 95351
<br /> I www.atcassociates.com
<br /> 209-579-2221
<br /> - -
<br /> J� A S S O C I A T E S I N CFax 209-579-2225.
<br /> Environmental, Geotechnical and Materials Engineers
<br /> From November 10 to November 12, 2004 and November 15 to November 17, 2004, an ATC
<br /> geologist supervised the installation of monitoring wells MW5 through MW12 . Soil samples
<br /> were collected from the boreholes of MW5, MW6, MW7, MW8, MW9, MW10, MWll , and
<br /> MW12 and selected soil samples were submitted for laboratory analyses . Each well was
<br /> constructed with 2-inch diameter PVC casing, with MW8 , MW9, MW10, and MWl l extending
<br /> to a depth of 65 feet bgs in the shallow groundwater bearing zone, MW5 , MW6, and MW12
<br /> extending to a depth of 90 feet bgs in the intermediate groundwater bearing zone, and MW7
<br /> extending to a depth of 121 feet bgs in the deep groundwater bearing zone.
<br /> Monitoring wells MW5 , MW6, MW8, MW9, MW10, and MW12 were developed on December
<br /> 22 and 23 , 2004. An obstruction encountered in MW7 at approximately 64 to 65 feet bgs
<br /> prevented development of this well. MWl l was purged dry after removing 0.5 gallons of water.
<br /> Efforts to develop this well using a bailer revealed the presence of groat inside the well and the
<br /> total depth of the well was measured to be approximately 58 feet.
<br /> On December 22 and 23 , 2004 monitoring wells MWl through MW12 were surveyed relative to
<br /> NAD 83 and NGVD29 for position and elevation and groundwater samples were collected from
<br /> MWl through MW6, MW8 , MW9, MW10, and MW12 . Petroleum hydrocarbon constituents
<br /> were detected in soil samples collected from the boreholes of MW5 through MW9 and MW 12 .
<br /> Groundwater samples were not collected from MW7 and MWl l due to an obstruction in MW7
<br /> and grout infiltration in MWll . Petroleum hydrocarbons were detected in the groundwater
<br /> samples collected from MWl through MW6, MW8 through MW10, and MW12. The results of
<br /> the subsurface investigation activities are presented in ATC ' s Subsurface Investigation Report,
<br /> dated July 25 , 2005 ,
<br /> On April 7, 2005 , an ATC geologist supervised the destruction of MWl l and the installation of
<br /> replacement monitoring well MW11R to a depth of approximately 65 feet bgs using 2-inch
<br /> diameter schedule 40 PVC casing. Refer to ATC ' s First and Second Quarter 2005 Monitoring
<br /> Report, dated October 10, 2005 , for additional information.
<br /> 2.0 METHODS AND PROCEDURES
<br /> To evaluate the lateral extent of impacted groundwater in the shallow zone, monitoring well
<br /> MW 13 was installed off-site to the west and monitoring well MW 14 was installed in the northern
<br /> portion of the site. Monitoring well MW15 was installed on-site downgradient from the source
<br /> area to evaluate the vertical extent of impacted groundwater. Field activities were performed in
<br /> general accordance with ATC ' s Subsurface Investigation Workplan, Former Stockton City Taxi
<br /> Cab Company, 2085 East Fremont Street, Stockton, California, dated, October 21 , 2005 . The
<br /> workplan was approved by SJCEHD in a letter dated November 28 , 2005 .
<br /> S:\Enviromental\28349\reports\sum.doe 2 ATC Associates Inc.
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