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<br /> (YVATC 1117 Lone Palm Avenue, Suite B
<br /> Modesto, CA 95351
<br /> www.atcassociates.com
<br /> 209-579-2221
<br /> ASSOCIATES I NC . Fax 209-579-2225
<br /> Environmental, Geotechnicai 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 were
<br /> collected from the boreholes of MW5 , MW6, MW7, MW8, MW9, MW10, MWl1 , and MW12 and
<br /> selected soil samples were submitted for laboratory analyses. Each well was constructed with 24nch
<br /> diameter PVC casing, with MW8, MW9, MW10, and MWl l extending to a depth of 65 feet bgs in the
<br /> shallow groundwater bearing zone, MW5 , MW6, and MW12 extending to a depth of 90 feet bgs in the
<br /> intermediate groundwater bearing zone, and MW7 extending to a depth of 121 feet bgs in the deep
<br /> groundwater bearing zone.
<br /> Monitoring wells MW5, MW6, MW8, MW9, MW 10, and MW 12 were developed on December 22 and
<br /> 23 , 2004. An obstruction encountered in MW7 at approximately 64 to 65 feet bgs prevented
<br /> development of this well. MWl l was purged dry after removing 0 .5 gallons of water. Efforts to
<br /> develop this well using a bailer revealed the presence of grout inside the well and the total depth of the
<br /> well was measured to be approximately 58 feet.
<br /> On December 22 and 23 , 2004 monitoring wells MWl through MW12 were surveyed relative to NAD
<br /> 83 and NGVD29 for position and elevation and groundwater samples were collected from MWl
<br /> through MW6, MW8, MW9, MWIO, and MW12 . Petroleum hydrocarbon constituents were detected
<br /> in soil samples collected from the boreholes of MW5 through MW9 and MW12 . Groundwater samples
<br /> were not collected from MW7 and MWII due to an obstruction in MW7 and grout infiltration in
<br /> MWII . Petroleum hydrocarbons were detected in the groundwater samples collected from MWl
<br /> through MW6, MW8 through MW10, and MW12. The results of the subsurface investigation activities
<br /> are presented in ATC's Subsurface Investigation Report, dated July 25, 2005 .
<br /> On April 7, 2005 , an ATC geologist supervised the destruction of MWII and the installation of
<br /> replacement monitoring well MW11R to a depth of approximately 65 feet bgs using 2-inch diameter
<br /> schedule 40 PVC casing. Refer to ATC' s First and Second Quarter 2005 Monitoring Report, dated
<br /> October 10, 2005 , for additional information.
<br /> From September 25 to 30, 2006, an ATC geologist supervised the installation of MW13 and MW14 to
<br /> approximately 60 feet bgs, and MW15 to approximately 151 feet bgs. To evaluate the lateral extent of
<br /> impacted groundwater in the shallow zone, MW13 was installed off-site to the west and MW14 was
<br /> installed in the northern portion of the site. Monitoring well MW 15 was installed on-site downgradient
<br /> from the source area to evaluate the vertical extent of impacted groundwater. The results of the
<br /> subsurface investigation activities are presented in ATC ' s Subsurface Investigation Report, dated
<br /> December 20, 2006,
<br /> SCOPE OF WORK
<br /> Planning
<br /> ATC will schedule field personnel and equipment, notify Underground Services Alert to locate
<br /> underground utilities as required, and perform other necessary field preparation and job start-up
<br /> S:\Environmental\28349\wkp.doc 2 ATC Associates Inc.
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