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Former Beacon Station�o.12474 May 13, 2014 Stockton California Well Destruction Report California Well Standards Bulletins 74-81 and 74-90, and the EHD Well Destruction Standards. Well Destruction Fieldwork Horizon witnessed AWA conduct well destruction operations from 3 to 17 March 2014. Mr. John Yoakum and Mr. Ted Tasiopoulos, registered environmental health specialists with EHD observed well destruction operations. The following wells were destroyed by the over-drilling method: monitoring wells MW-1 through MW-3, MW-6 through MW-21, triple-completion vapor wells VW-1/2/3 and VW-4/5/6, vapor well VW-7 and air sparge well AS-1. The following wells were destroyed by the pressure grouting method: monitoring wells MW-4 and MW-5. Prior to destruction activity, measurements indicated that the total depth in each well casing was within 10% of the total installed depth. In the over-drilling method, well construction materials were drilled out by hollow-stem augers to the diameter of the original borehole and to the total depth of the installed well. For destruction of triple-completion wells VW- 1/2/3 and VW-4/5/6, the wells were drilled out with 8-inch diameter augers guided by the deepest casing followed by over-drilling with 10-inch diameter augers to the same depth. Neat cement grout was emplaced in the bore holes to within 3 feet of the surface as the auger string was extracted. The neat cement was topped off until the level stabilized. Approximately '/2 foot of bentonite was emplaced over the grout to create a base for the backfill material. Sand backfill was placed to within 1 foot of the ground surface. In paved areas, the upper foot of the borings were backfilled with 8 inches of compacted aggregate base and with either four inches of hot-mix asphalt or steel reinforced concrete to match the surrounding pavement surface. In unpaved areas of the Site, the upper three feet of the bore hole was backfilled with native soil. In the pressure grouting method, neat cement grout was pumped into the well casings via tremie set to within three feet of the total measured depth of the wells. The grout level was brought to the top of well casing and was topped off until the level stabilized. Air pressure of 25 pounds per square inch was applied to the top of the well casings for 10 minutes. The grout was topped off, as needed. The well materials were drilled out to a depth of approximately 3 feet to a diameter of approximately one foot larger than the original borehole. The bore hole was deepened to expose the upper 6 inches of the casing. Neat cement grout was emplaced in the bore hole to within 1 foot of the surface. The upper foot of the borings were backfilled with 8 inches of compacted aggregate base and four inches of hot-mix asphalt. All well vaults were removed and bore holes were backfilled to flush with the surrounding surface. The calculated volumes of grout required to destroy the wells and the actual emplaced grout volumes are summarized in the enclosed Table 1. Well and soil cuttings were temporarily contained in three roll-off bins. Two four-point composite soil samples were collected from the three bins for characterization and were submitted, with chain-of-custody documentation, to Kiff Analytical, Inc. (Kiff), a California 12474 Well Destruct Rpt Mayl4.doc Project No. 1474.03 2 HORIZON ENVIRONMENTAL INC.