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Remeldial Action Plan June 14, 2017
<br /> Project#Z054000052 Page 5
<br /> extraction test, groundwater pump and treat and SVE technologies were capable of removing high
<br /> concentrations of hydrocarbons from soil and groundwater beneath the site (Park, 1999).
<br /> A soil vapor and groundwater extraction and treatment system was started on April 26, 2001. The remediation
<br /> system was connected to soil vapor extraction (SVE) wells VW-1, VW-2 (A, B), VW-3, VW-4 (A, B, C), VW-5
<br /> (A, B, C), and VW-6 (A, B, C). The system operated until November 2007, when it was shut down for the
<br /> fourth quarter 2007 sampling, UST removal, and well destruction activities. The system conveyance lines were
<br /> reconnected and the system was restarted in April 2008. GHC upgraded the soil vapor and groundwater
<br /> treatment system in September 2008. The system pad was expanded to include a 350-gallon batch tank, a
<br /> bag filter, a 1 HP transfer pump, four 1,000 pound granular activated carbon liquid-phase vessels, and a
<br /> groundwater extraction system control panel. The upgraded system was designed to extract vapor from wells
<br /> VW-1, VW-3, VW-4, VW-5, and VW-6, and extract groundwater from wells MW-11R and MW-12R. The
<br /> system was restarted in December 2008. The groundwater extraction (GWE) system was never re-started
<br /> following completion of the system upgrade activities. The GWE system extracted and treated 582,804 gallons
<br /> of groundwater from the subsurface. The SVE system was subsequently shut down on March 19, 2009 for
<br /> repairs and remained off-line as negotiations between Thrifty and ConocoPhillips regarding the transfer of site
<br /> responsibility were conducted. As of March 19, 2009, 210,156 pounds of hydrocarbons had been removed by
<br /> the SVE system (GHC, 2009).
<br /> In July 2007, GHC performed an ozone sparging bench scale test. Results indicated that the site petroleum
<br /> hydrocarbons in soil and groundwater were successfully destroyed with ozone treatment. Ozone sparging,
<br /> however, generated concentrations of chromium VI and bromate that exceeded the California maximum
<br /> contaminant levels (MCLs) for these compounds. Based on the results, ozone sparging was determined to not
<br /> be a feasible method of groundwater treatment (GHC, 2008b).
<br /> In July 2010, Stantec performed a 5-day SVE system shake down and ROI test. Results indicated that there
<br /> was no longer a need for vapor extraction at the site related to vadose zone treatment. Stantec subsequently
<br /> submitted an Interim Remediation Action Plan, dated August 27 2010, that was approved by the SJCEHD on
<br /> September 2, 2010. The IRAP proposed to run the groundwater extraction system on MW-11 R until site
<br /> demolition activities began at the site. However, due to an accelerated redevelopment schedule, interim
<br /> remediation was postponed in preparation for the site demolition. The remediation system has been removed
<br /> and the conveyance piping has been cut at the well boxes in preparation for the recently-completed
<br /> redevelopment activities. No remedial equipment is currently present at the site.
<br /> In ATC's Site Conceptual Model and Human Health Risk Assessment, dated September 30, 2011, ATC
<br /> recommended the completion of additional soil and groundwater delineation and soil vapor sampling activities
<br /> be performed at the site prior to proposing any additional remedial activities. The additional site assessment
<br /> activities were performed during first quarter 2012; and a report documenting the findings was submitted in
<br /> July 2013. On January 14, 2014, Cardno ATC submitted a Corrective Action Plan and recommended a
<br /> remediation strategy consisting of a combination of air sparging and soil vapor extraction.
<br /> Cardno ATC submitted Air Sparge/Soil Vapor Extraction Pilot Test Work Plan dated July 7, 2014, and
<br /> implemented the work in the first quarter 2015. The pilot testing indicated that vapor extraction and air
<br /> sparging were viable methods for remediating impacted soil and groundwater at the site. Results were
<br /> summarized in Cardno ATC's Pilot Test Summary Report dated August 4, 2015.
<br /> 2.4 SENSITIVE RECEPTORS
<br /> In November 1992, SSB Environmental Consultants, Inc. (SSB) performed a well survey within a '/z-mile radius
<br /> of the site. Results indicated that the City of Stockton well No. 11 was located at the corner of Inglewood and
<br /> Leslie Avenues approximately 2,100 ft southeast of the site. In addition, a number of private wells were
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