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Work Plan—Additional Soil and Groundwater Investigation CSUS—Multi-Campus Regional Center October 5,2001 Page-5- analyses. The soil sampling equipment will be cleaned prior to collecting each sample using laboratory- grade,non-phosphate detergent and de-ionized water and double rinsed with de-ionized water. The drill cuttings and steam cleaning effluent will be placed in DOT-approved 55-gallon drums, sealed, labeled, and left on-site pending laboratory analyses. Disposal of hazardous materials, if any, will be the responsibility of the property owner. 4.3 MONITOR WELL INSTALLATION The monitor wells will be constructed with 15 feet of 2-inch outside diameter, Schedule 40, flush- threaded, machine-slotted PVC screen (slot size 0.020). The monitor wells will be installed deep enough to allow five feet of slotted casing to be above and 10 feet of slotted casing below the static water table level at the time of the well installation. A flush-threaded PVC bottom cap will be placed at the bottom y of the screen sections.Blank PVC casing will be installed above the screens to the ground surface. A filter pack of#3 Monterey sand will be placed in the annular space to approximately two feet above `r the screen while the auger is in place. The depth of the sand in the well annulus will be monitored with a weighted tape measure while the sand is being placed and the auger is being gradually retracted to avoid bridging. To form a protective seal, approximately two feet of bentonite pellets will be installed above the sand as the augers are retracted. The bentonite will be hydrated using potable water. A surface seal of neat cement will be pumped via a tremie pipe into the annulus and will extend from the bentonite to the ground surface. Depending on the stability of the borehole, the augers may be removed before or during emplacement of the grout. The tremie pipe will remain near the top of the bentonite seal until the pumped grout is forced to the surface.The monitor wells will be completed with locking traffic boxes. 4.4 MONITOR WELL SURVEYING,DEVELOPMENT,AND SAMPLING Condor's licensed land surveyor will determine the location and relative elevation of the well collars following the installation of the monitor wells. The well collars will be surveyed with a vertical accuracy of 0.01 foot and horizontal accuracy of 1.0 foot. The measuring point for water-level measurements will be marked on each well collar. The groundwater gradient will be estimated using the survey information v and the depth to water measurement in each well. At least 48 hours following construction, the monitor wells will be developed by surging and bailing the groundwater in each well until the discharge water is relatively free of sediment (clear to the unaided eye). The monitor wells will be purged until the temperature, electrical conductivity and pH of the water has stabilized. All well-development equipment will be cleaned prior to use in each well by washing in a solution of laboratory-grade, non-phosphate detergent and de-ionized water and double rinsing with de- ionized water. The purge water discharged from the wells during development will be placed. in 55- gallon drums, sealed, labeled, and left on-site pending results of laboratory analyses. Groundwater samples will be collected at least 48 hours following development of the monitor wells. Prior to sample collection, the static water level in each well will be measured to the nearest 0.01-foot with a battery-operated, water level meter. A disposable bailer will be lowered into each well to check for floating product, petroleum odors, and/or sheen. If floating product is present, the thickness will be measured. Laboratory samples will not be collected from wells that contain floating product. The monitor wells will be purged using a clean, disposable bailer until the temperature, electrical conductivity, and pH of the water has stabilized. At least three casing volumes of water will be purged i k6�, n L� CONDOR