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i... Additional Soil and Groundwater Investigation and Monitor Well Installation Report CSUS Multi-Campus Regional Center January 11,2002 Page 6 w The soil sampling equipment was cleaned prior to collecting each sample by washing the sampling device in a solution of laboratory-grade, non-phosphate detergent and de-ionized water, and double-rinsing with de-ionized water. 4.4 MONITOR WELL CONSTRUCTION The monitor wells were constructed with 20 feet of 2-inch outside diameter, Schedule 40, flush-threaded, machine-slotted PVC screen(slot size 0.020). A flush-threaded PVC bottom cap was placed at the bottom of the screen sections. Blank PVC casing was installed above the screens to the ground surface. The monitor wells were constructed within the hollow-stem auger. Therefore, the auger itself acted as a tremic for the annular seal materials. Each monitor well was installed to a total depth of 45 feet bgs. For each well, a filter pack of#3 Monterey sand was placed in the annular space to approximately two feet 4 above the screen while the auger was in place. The depth of the sand in the well annulus was monitored with a weighted tape measure while the sand was being placed and the auger gradually retracted to avoid bridging. To form a protective seal, approximately two feet of bentonite pellets 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 poured into the annulus extending from the bentonite to the ground surface. The augers �• were gradually retracted during emplacement of the grout. Each monitor well was completed with a flush mounted traffic-rated vault box. A well construction graphic is included as part of the geologic boring log for each well (Appendix B). Table 1, below, includes construction details for the monitor wells. V Table Y Monitor Well Construction Details Monitor Well MW-1 MW-2 MW-3 w.. Date Installed 12/10/01 12/10/01 12/10/01 Well Depth(ft.) 45 45 45 Well Casing Diameter(in.) 2 2 2 Borehole Diameter(in.) 8 8 8 46- Well Screen Interval(ft.) 25-45 25-45 25-45 Filter Pack Interval(ft.) 23-45 23-45 23-45 i.. Bentonite Seal Interval(ft.) _21-23 21-23 21-23 Grout Seal Interval(ft.) 0-21 0---21 r- 4.5 MONITOR WELL DEVELOPMENT On December 12, 2001 monitor wells MW-1, MW-2, and MW-3 were developed by surging and bailing the groundwater in the well with a surge block and a stainless-steel bailer. Monitor wells MW-1 and MW- 3 were developed until the discharge water was relatively free of sediment(clear of particles visible to the unaided eye). A total of 10 well-bore volumes were removed from each of monitor wells MW-1 and MW- 3 during development. Monitor well MW-2 had approximately five feet of sediment in the bottom of the +r well. The well was bailed dry after approximately 1 '/ gallons of water were removed from the well. Monitor well MW-2 was further developed on December 14, 2001 using the same method as the previous ' development. The well again bailed dry after approximately 1 '/2 gallons of water were removed from the . well. w A + `0 CONDOR LW