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3 �� Cardno®
<br /> Well Destruction Report ATC
<br /> Former Cheaper Store No.37 Shaping the Future
<br /> December 12,2013
<br /> In September 2010,ATC conducted a soil gas study to evaluate the potential for soil vapor intrusion into the
<br /> existing commercial structure located on-site. The results indicated that neither the released non aqueous phase
<br /> liquid (NAPL) present in the vadose zone or the dissolved hydrocarbons in the groundwater posed a risk to human
<br /> health.
<br /> In October 2011, ATC submitted a Case Closure Request at the request of the EHD. Clarification was requested
<br /> by EHD in January 2012 and provided by ATC in March 2012 in the form of a proposal to conduct indoor air
<br /> sampling.
<br /> In a letter dated January 16, 2013, EHD relayed the information that they had received a No Further Action
<br /> Required Concurrence letter from the CVRWQCB, dated December 18, 2012. The EHD directed the destruction of
<br /> the monitoring wells used in the investigation.
<br /> Cardno ATC's"Workplan for Destruction of Groundwater Monitoring Wells, Former Cheaper Store No. 37, 15 East
<br /> Grant Line Road, Tracy, California 95376-2720"dated March 22, 2013 was approved by EHD on April 1, 2013.
<br /> WELL DESTRUCTION ACTIVITIES
<br /> Cardno ATC abandoned groundwater monitoring wells MW1, MW2, MW3, MW4, MW5, MW6, MW7, and MW8.
<br /> The locations of the groundwater monitoring wells are shown on Figure 2.
<br /> Wells Abandonment Procedures
<br /> On June 20, and 21, 2013, Cardno ATC supervised the destruction of MW5, MW6, MW7, and MW8. Due to site
<br /> conditions and well construction details, destruction of MW1, MW2, MW3, and MW4 was delayed. These
<br /> remaining wells were destroyed on August 28, 29, and 30, 2013. Well destruction activities were carried out by
<br /> Woodward Drilling of Rio Vista, California(State C57 license no. 710079).
<br /> The groundwater monitoring wells MW3, MW4, MW5, MW6, MW7, and MW8 were abandoned by over-drilling.
<br /> Where the casing could be removed whole, it was extracted from the well either using a stinger in the auger or the
<br /> winch line on the drill rig. The sand pack and any remaining casing were then over-drilled to the depth of the
<br /> installed well.An 8-inch diameter hollow-stem auger was used on MW3, MW4, MW4, MW5, MW6, and MW7, and a
<br /> 12-inch diameter hollow-stem auger was used on MW8. Once the over-drilling process had been completed, the
<br /> boreholes were backfilled with a neat cement grout slurry mix from the base of the annulus to the surface using a
<br /> tremmie pipe. Groundwater displaced to the surface during grout installation was pumped out of the excavation,
<br /> collected, and containerized for proper disposal. Any remaining soil voids at the surface were backfilled,
<br /> compacted, and resurfaced to match the surrounding surface completion.
<br /> Groundwater monitoring wells MW1 and MW2 were abandoned via grouting due to the proximity of above-ground
<br /> structures or trees that would not allow a drill rig to auger out the bore holes. The bottoms of the casing were
<br /> punched out to provide a route to the bottom of the well installation, and the casing was slowly extracted as the well
<br /> was filled with neat grout using the casing as a tremmie pipe. The casing was completely removed in both cases.
<br /> Prior to the abandonment for protection of the annular seal at the ground surface, the well boxes and locking plugs
<br /> were removed and a minimum 24-inch diameter hole was excavated around each well box location to a depth of
<br /> approximately 36 inches. The grout used to fill the wells was made to overflow into the excavation to form a
<br /> minimum 24-inch diameter"mushroom cap" like seal. Any remaining soil voids were back-filled, compacted and
<br /> resurfaced to match the surrounding surface completion.
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