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<br /> 1 1 17 Lone Palm Avenue,Suite 201
<br /> YA�� Modesto,California 1
<br /> 209-579-222-2221
<br /> Fax:209-579-2225
<br /> A E 8 0 C I A T E 6 INC.
<br /> On July 18, 2005, an ATC geologist supervised the advancement of cone penetration test (CPT) borings
<br /> CPTI, CPT2, and CPT3 to depths of 137, 78, and 91 feet below ground surface (bgs), respectively.
<br /> Groundwater samples were collected at a depth of 130 feet from CPTI; 70 feet from CPT2; and 87 feet
<br /> from CPT3. Petroleum hydrocarbons were detected in the groundwater samples collected from CPTI and
<br /> CPT3. In August 2005, ATC supervised the installation of four groundwater monitoring wells (JLM 16,
<br /> JLM17, JLM18, and JLM19). Petroleum hydrocarbons were not detected in groundwater samples
<br /> collected from these wells. Shallow groundwater flow beneath the site generally flowed in a radial pattern
<br /> towards JLM3 on August 30, 2005. Refer to ATC's Subsurface Investigation Report, dated November 7,
<br /> 2005, for additional information.
<br /> In October and November of 2008, ATC supervised the installation of seven groundwater monitoring
<br /> wells (JLM20 through JLM26). These wells were installed inside steel conductor casing to variable
<br /> depths. Observations associated with JLM21 during development activities indicated that this well was
<br /> compromised and needed to be replaced. Pursuant to a joint request from the San Joaquin County
<br /> Environmental Health Department (SJCEHD) and the CRWQCB, ATC prepared the Well Desh•action
<br /> and Installation Inside Existing Conductor Casing Workplan, dated December 8, 2008, describing
<br /> proposed methodology to destroy the compromised well and replace it with another one at the same
<br /> location. In electronic correspondence dated December 9, 2008, CRWQCB staff indicated the workplan
<br /> would be approved and authorized scheduling the work. The CRWQCB approved the workplan in a letter
<br /> dated December 10, 2008. On December 10, 2008, an ATC geologist supervised the destruction of
<br /> JLM21 and installation of replacement monitoring well JLM21. All of the monitoring wells (JLM3,
<br /> JLM4, JLM5, and JLM12 through JLM26) were sampled on December 15, 2008, as part of the fourth
<br /> quarter sampling event. Petroleum hydrocarbons were detected in groundwater samples collected from all
<br /> of the wells except JLM15, JLM17, JLM18, JLM19, JLM24, and JLM25. Shallow groundwater flow
<br /> beneath the site on December 15, 2008, generally flowed in a radial pattern towards JLM3. Intermediate
<br /> and deep groundwater flow directions beneath the site on December 15, 2008, were to the southwest and
<br /> northwest, respectively. Refer to ATC's Subsurface Investigation Report, dated February 13, 2009, for
<br /> additional information.
<br /> SUBSURFACE CONDITIONS
<br /> Geology
<br /> The vadose zone, from zero to approximately 22 feet bgs, generally consists of silty sand to
<br /> approximately 10 feet bgs that is underlain by a laterally extensive clayey silttsihy clay layer extending to
<br /> depths ranging from approximately 24 to 34 feet bgs. Interbedded layers of silts, sands, clays, and silty
<br /> sands were encountered below the afore mentioned clay layer and extended to depths ranging from
<br /> approximately 39 to 46 feet bgs, at which point a laterally extensive sandy layer was encountered. This
<br /> sandy layer extended to approximately 55 feet bgs in the southern portion of the site and approximately
<br /> 62 feet bgs in the northeastern portion of the site and was underlain by interbedded silts, clays and sands
<br /> to the depth explored for the intermediate depth wells(approximately 90 feet bgs).A clay layer extending
<br /> from approximately 87.5 feet bgs to 115 feet bgs was encountered at JLM26 and was underlain by sandy
<br /> silt to a depth of approximately 126 feet bgs. Sand was encountered to the terminal depth of 141 feet bgs
<br /> at JLM26.
<br /> Pilot Testing Workplan-J&L Market ATC Associates Inc.
<br /> 5:...\28589\Reports ATC Project No.54.28589.0001
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