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i Monitoring Well Destruction Report University Park 1252 Stanislaus Street,Stockton,California Page 2 Monitoring wells MW-1, MW-2, MW-3, MW-4, and MW-5 were destroyed by overdrilling from top to bottom so that all material within the original borehole, including the well casing, screen, filter pack, and annular seal were removed. The auger used to overdrill the wells was fitted with a casing reamer that kept the augers centered on the casing and shredded the PVC casing as the augers were advanced. The augers were advanced to a depth 45 feet in MW-1, MW-2, and MW-3, and to a depth of 49 feet in MW-4 and MW-5. Each borehole was then backfilled with neat cement using a truck-mounted pump hose and tremmie pipe to fill the borehole from the bottom upward to the surface. Monitoring well MW-8 was overdrilled until the rods met refusal at a depth of 53 feet. The borehole was then backfilled with neat cement following the same procedures described above and as directed by Adrienne Ellsaesser of the SJECHD. Groundwater was not displaced to the ground surface during the overdrilling activities. A minimum of six-inches of concrete was placed for surface completions. A metal ring was encountered approximately four feet below ground surface (bgs) during overdrilling activities at monitoring well MW-7. Drilling activities were subsequently halted at this location and the Condor Professional Geologist overseeing well destruction activities, contacted Ms. Ellsaesser of the SJCEHD. In email correspondence dated January 8, 2014, Ms. Ellsaesser indicated that if the well could not be overdrilled,the well must be destroyed with explosives. Cogco Wireline Services of Woodland, California, license number 582564, conducted detonation activities at MW-7 on January 9, 2014, in general accordance with specifications provided in Ms. Ellsaesser's email correspondence. The well was jetted to approximately 90 feet bgs prior to detonation activities to clear out any soil obstructions. A small-diameter PVC tremmie tube was wrapped with 80 grain detonation cord and placed in the well. The borehole was then backfilled with neat cement using a truck-mounted pump hose and tremmie pipe to fill the borehole from the bottom upward to the surface. A drum was placed over the top of the well and the cord was detonated, leaving the tremmie tube in the well. Additional cement was placed in the borehole and concrete was added to surface completion. The soil cuttings, pieces of PVC casing, traffic boxes, and grout cleanout were placed in Department of Transportation- (DOT-) approved drums and left on site pending characterization and disposal. Monitoring well destruction details including depth to water, destruction method, total depth expected, total depth actually encountered, over-drilling auger diameter, total volume of neat cement calculated to be needed to fill the borehole, and total volume of neat cement actually placed are included in Table I on ill the following page. i �I i� CONDOR i