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i <br /> ®- Engineers <br /> Planners <br /> Economists <br /> &dentists 3 <br /> August 3, 1994 <br /> BAE31604.AS.01 <br /> Gregg Drilling & Testing <br /> 42 Berry Drive 1 <br /> Pacheco,,CA 94533 <br /> Attention: Chris Christensen <br /> Subject: Addendum to Request for Bid dated July 14, 1994 <br /> As we discussed during our telephone conversation, this letter is an addendum to the <br /> Request for Bid letter dated July 14, 1994 for drilling activities in Stockton, California. <br /> This addendum specifies changes to the original scope of work and describes additional <br /> work. <br /> Changes to the July 14th Specifications <br /> t <br /> As shown by Figure 1, each sparging well shall be constructed of 2-inch diameter, <br /> schedule 40 carbon-steel for the initial 20 feet below ground surface . The remaining depth <br /> (20 to 90'feet below ground surface) shall be constructed of 2-inch diameter, schedule 40 <br /> PVC (formerly specified as 1-inch diameter, schedule 40 PVC). The carbon-steel to PVC <br /> connection shall be flush-threaded. <br /> The July 14th Specifications indicate that the ENGINEER will "continuously log" geology <br /> of both boreholes. Continuous logging shall consist of obtaining a split-spoon soil sample <br /> at each 5-foot depth interval. The ENGINEER reserves the right to obtain soil samples at <br /> shorter intervals (less than 5 feet) if necessary. <br /> Additional Scope of Work <br /> The additional scope of work includes but is not limited to drilling one borehole for the <br /> installation of four nested piezometers. A schematic diagram of the nested piezometers is <br /> shown on Figure 2. The location of the nested piezometers will be within 50 feet of the <br /> two dual-sparging/vapor extraction wells. The CONTRACTOR shall furnish all equipment <br /> and materials necessary for drilling and installation of the piezometers. A hollow-stem <br /> auger drilling rig shall be used for drilling the borehole for the piezometers; the <br /> CONTRACTOR may suggest alternative drilling techniques. <br /> t <br /> CH2M HILL 1 1 I7 Broadway,P.O.Box 72687,Oakland,CA 94604-2681 510 251-2426 Fax 510 8 93-820.5 <br />