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' • • LFR Levine-Fricke ' direct supervision of a California Professional Geologist who has expertise in stratigraphic well logging. The total depth of the boring shall be determined in the field, based on the lithology encountered. Based on lithologic and groundwater elevation data collected from other wells at the Site, it is anticipated that the total depth of the boring will be approximately 125 feet bgs. 1 3.4.2 Monitoring Well Construction and Development ' After the boring has been advanced to the desired depth, the groundwater monitoring well shall be constructed using flush-threaded, 2-inch-diameter, polyvinyl chloride (PVC) casing. The well screen shall be 0.010-inch slotted PVC casing. The length of ' the well screen shall be based on the thickness of the water-yielding sediment encountered. Based on data collected from the five existing groundwater monitoring wells, it is anticipated that the screened interval will be approximately 20 feet long with ' at approximately 5 feet above the groundwater table to accommodate seasonal fluctuations. Blank PVC casing shall be installed from the top of the screened interval to the ground surface. Figure 4 presents a typical well construction diagram. ' After the well casing has been placed inside the augers, the well annulus materials (sand, bentonite, and grout) will be added. The well annulus opposite the screened ' interval shall be filled with clean Number 2/12 Monterey sand to a height of approximately 3 feet above the top of the well screen. A minimum of 3 feet of bentonite chips shall be placed and hydrated above the sand pack to isolate the screened ' interval from material above and prevent the entrance of grout into the sand pack. After the bentonite seal has hydrated, a clean cement-bentonite grout mix shall then be placed in the annular space above the bentonite seal to the ground surface to seal the ' remainder of the borehole from the possible infiltration of surface water. The SJCEHD shall be notified before the wells are sealed so that a field inspector may witness this activity. After the well is completed, the top of casing shall be surveyed to the nearest ' 0.01 foot and tied into the elevations of the existing wells by a licensed surveyor. The well shall be completed with an above-grade, "stovepipe-type" well box with a ' locking cover to protect the integrity of the well. The well shall be installed outside the gravel pit in the northwestern boundary of the Site (between monitoring wells MW-01 and MW-05). Soil cuttings generated during well installation activities shall be spread level near the well location. The well shall be developed a minimum of 24 hours after installation by bailing, ' surging, and/or pumping to remove sediment left in the well during construction and to enhance the hydraulic communication between the well and surrounding sediments. Observations of pH, temperature, specific conductance, quantity, and clarity of water ' withdrawn shall be recorded after each well volume has been purged during development. The well shall be developed until approximately 3 to 10 well casing volumes are removed or until relatively sediment-free water is produced. At the completion of well development, a groundwater sample shall be collected for laboratory analysis. Well development purge water shall be transferred to either the ' wp-MW-06_Insall-Sep05-final-09025v2.dm:LFR Page 5