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G� Cardno® January 17,2014 3 AT Eggiman Well Destruction Report Shaping the Future Cardno ATC prepared a Case Closure Report that compared the characteristics of the release that had occurred at the site with the parameters included with the LTCP. Cardno ATC concluded that the theoretical human health risks imposed on the building's occupants could exceed acceptable levels as determined by the Johnson Ettinger Model for Subsurface Vapor Intrusion into Buildings. Cardno ATC recommended collecting soil vapor samples to evaluate actual contaminant concentrations present in the soil to better define this risk. The report stated that if the results indicate the incremental risk from vapor intrusion to indoor air and the hazard index quotient from vapor intrusion to indoor air were below acceptable levels, Cardno ATC would recommend no further action. The context for this recommendation and additional details are included in Cardno ATC's Case Closure Report, dated March 26, 2013. In a letter dated May 22, 2013, the EHD determined that the site investigation and remedial action of contamination resulting from an unauthorized release from the USTs formerly and/or currently located at the site had been completed. Furthermore, the EHD concluded that the completed corrective actions were adequate to protect public health for current land use and forwarded a Case Closure Summary to the CVRWQCB for concurrence. In a letter dated June 5, 2013, the CVRWQCB staff stated that they concurred with the EHD's recommendation for closure. In a letter dated June 13, 2013, the EHD stated it had received concurrence from the CVRWQCB with regard to the"No Further Action" request for the site and indicated all of the wells installed as part of the site investigation and remediation are to be destroyed. On July 29, 2013, Cardno ATC submitted the Workplan for Destruction of Groundwater Monitoring Wells, Eggiman Property, 1112 East Harding Way, Stockton, California 95205, to EHD. This workplan was approved by EHD in a letter dated August 12, 2013. SCOPE OF WORK 1, 6 Planning and Permits Car o ATC obtained a Well Destrttptio ermi#from EHD °r dest�rtion of monitoring wells MW1 through M 11 and remediation wells OS11 S , QS2� QSM,, 053, C�S4, and`OS5. Cardno ATC also obtained an encroachment permit from theft o tocktDrffor t 6 wells constructed within the public right of way. The Cit p Y P 9 Y Y required a Traffic Control Plan so Cardno ATC contracted with Traffic Management Inc. (TMI)to provide the required plan. The Traffic Control Plan was reviewed by the City and it was determined that a lane on Stanford Avenue should be closed during the destruction of MW8 and MW11. The City consequently required the Traffic Control Plan include advanced notification signage of the closure for area residents and the signage be posted two weeks in advance of the closure. Cardno ATC notified Underground Services Alert to locate underground utilities as required, schedule field personnel and equipment, and performed other necessary field preparation and job start-up activities. During initial well destruction activities, the driller, Cascade Drilling (California License C57 938110), observed that the placement of MW8 was located underneath some utility wires and consequently could not be overdrilled with a conventional drill rig while maintaining the necessary clearance for the mast. For safety reasons, Cardno ATC petitioned the EHD to destroy MW8 by pressure grouting and was authorized to make this change. Wells Abandoned by Over Drilling All the groundwater monitoring wells(except MW8 and MW11) and ozone injection wells were abandoned by over- drilling. The procedure involved removal of the locking plug and excavating the well box. Then an auger tool with a pilot shank was used to drill out the casing, sand pack, and other well components. The resulting borehole was then filled with a neat cement grout slurry mix from the base of the annulus to the surface using a tremmie pipe. www.cardnoatc.com