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Subsurface Investigation Work Plan SJC Records Retention Center Page 2 County Environmental Health Department(EHD)for approval.The work plan and permit application were approved in a letter from EHD dated February 29, 2012. On March 29, 2012, Condor and Jim Thorpe Oil (Thorpe) excavated and exposed one single-walled steel UST and associated product piping at the Site. EHD and FPD personnel were on Site to observe the UST closure activities and to specify soil sampling locations. Thorpe partially excavated the UST to a depth of approximately three to six feet bgs to confirm its location and estimate its dimensions.The top of the UST was two and a half feet bgs,four feet in length, and had a diameter of approximately four feet. The bottom of the tank appeared to be at six and a half feet bgs. The UST was a 375-gallon capacity, single-walled steel tank. Observation of the exterior of the UST indicated that the UST appeared to be in good condition with no visible holes or cracks. The piping that would have risen to the surface and dispenser had been removed and the pipe plugged with a metal fitting. The vent piping had been left connected and in place.The fill piping had been removed and left open.The UST had obvious rust corrosion, but was sound when struck with a hammer to remove loose soil and rust. Sand was observed in a conical pile inside the UST. The presence and location of the sand suggested that the UST had been previously abandoned in place by filling with sand.No petroleum hydrocarbon staining of soil was observed in the sidewalls of the excavation. Condor determined that the proximity of the tank to an active natural gas line,electrical line,and the warehouse wall foundation would make full removal of the UST challenging. Consequently,Condor recommended closure in-place in a Revised UST Removal Work Plan(dated March 20,2012).The work plan was approved by EHD in a letter dated March 29,2012. The UST was filled with cement and abandoned in-place as approved. The UST abandonment was documented in the Underground Storage Tank Closure in Place and Soil Sampling Report dated April 20,2013. 2.3 MONITORING WELL INSTALLATION AND SAMPLING During a meeting on April 4, 2013, Mr.Nuel Henderson with EHD indicated that additional groundwater investigation would be required at the Site. Condor prepared the Monitoring Well Installation Work Plan dated July 18, 2013, subsequently approved by Lisa Medina with EHD in her letter dated September 9,2013. One groundwater monitoring well(MW-1)was installed on November 18,2013.The drilling services were provided by V&W Drilling, Inc. of Stockton, California, C57# 720904. Monitoring well MW-1 was installed to a total depth of 40 feet bgs and was constructed with 20 feet of 2-inch outside diameter,Schedule 40, flush-threaded, machine-slotted PVC screen (slot size 0.010). A flush-threaded PVC bottom cap was placed at the bottom of the screen section and blank PVC casing was installed above the screen to the ground surface.A filter pack of#2/12 sand was placed in the annular space to approximately two feet above the screen while the auger was in place. To form a protective seal, approximately five feet of bentonite chips were installed above the sand as the augers were retracted.The bentonite was hydrated using potable water. A surface seal of neat cement was then tremied into the annulus extending from the bentonite to the ground surface.The monitoring well was completed with a flush-mounted traffic-rated vault box. Groundwater samples were collected from well MW-1 on a quarterly basis between December 2013 and December 2014, when groundwater sampling was reduced from quarterly to semiannually. Analytical results of groundwater samples collected from well MW-1 indicate that dissolved petroleum hydrocarbon constituents have impacted shallow groundwater beneath Site. The most recent analytical results of groundwater collected from well MW-1 (March 2018)indicate that dissolved gasoline constituents beneath the Site have been reduced by approximately 70%(TPH-G)to more than 99%(benzene and toluene). 3.0 SUBSURFACE CONDITIONS Native soil observed in the initial UST excavation consisted of reddish brown, slightly moist, stiff, lean clay. Soil above and around the UST was observed to be poorly graded sand from the ground surface to 'Lit CONDOR