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Beacon Station No 641 December 8, 1997 .Stockton, IifQrnia m nal Subsurface v Qat RepW well, also the total drilled depth of each boring, was approximately 75 feet bsg Blank PVC well casing was installed from the top of the screened interval at approximately 50 feet bsg to the surface The annular space opposite the well screen was backfilled with # 3 Monterey sand to approximately two feet above each screened interval An approximate three-foot ' seal of bentonite was placed above the filter sand and hydrated with approximately ten gallons of fresh water Additional fresh water was added at the direction of the SJC ' PHS/EHD inspector A neat cement/bentonite grout was used to complete the annular seal to the surface The grout was pumped through grout hoses/tremmie pipes placed in each boring immediately above the bentonite seal and withdrawn with the rising grout level in one continuous operation The top of the well casing was secured with a locking water-tight ' expansion cap and a steel, water-tight, traffic box set slightly above grade with a concrete ' apron The construction details are shown on the corresponding boring logs in Appendix C Soil Vapor Extraction Well Installation - Phase, VW-1, VW-2 VW-3, and VW-4 are each 2-inch ID, schedule 40 PVC soil vapor wells constructed in 10-inch diameter soil borings Wells VW-1 and VW-2 were installed with monitoring well MW-1, as a triple completion, in the 10-inch diameter soil boring B-2 Wells VW-3 and VW-4 were installed as a dual completion in the 10-inch diameter soil boring B-1 The screened intervals are VW-1 = 44 to 54 feet bsg, VW-2 = 21 to 36 feet bsg, VW-3 = 45 to 55 feet bsg, and VW-4 = 25 to 40 feet bsg Blank PVC well casing was installed from the top of each screened interval to the surface The annular space opposite teach well screen was backfilled with # 3 Monterey sand, and a seal of bentonite was placed in the intervals between the top of the filter sand and the bottom of the screened interval of the next nested well Bentonite seals varied from 3 to 7-feet thick, as indicated on the boring logs A neat cement/bentonite grout was used to complete the annular seal from the top of ' the uppermost seal to approximately one foot bsg A PVC cap was placed on the top of each vapor well until the wells are plumbed into a soil vapor extraction system The top of each well cluster was sealed within a 24-inch diameter, water-tight, steel traffic-rated box previously installed over 18-inch PVC conductor casings The construction details are shown on the corresponding boring logs in Appendix C ' 1641-13 rpt 6 HORIZON ENVIRONMENTAL INC