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t ' <br /> 4 GROUNDWATER MONITORING WELL INSTALLATION <br /> Following the completion of the borehole drilling and sampling activities, three of the <br /> boreholes were completed at groundwater monitoring wells. Murray & Associates <br /> completed the necessary workplans and obtained the appropriate permits to install the <br /> groundwater monitoring wells from the San Joaquin County Department of Health,Division <br /> of Environmental Health. The three monitoring wells were installed to a completed depth <br /> of 25 feet below ground surface. Well completion details and a lith.ologic log of each of the <br /> _ soil borings are presented in Appendix 1. <br /> 1-4 Materials used for the construction of the groundwater monitoring well included 2-inch I.D. <br /> interior/exterior flush threaded PVC Schedule 40 casing and well screen. Well screen <br /> perforations were precision machine slotted;screen slot sizes were 0.02 inches. Fifteen feet <br /> of well screen was installed into each boring, followed by 10-feet of blank casing. A sand <br /> ` pack was placed so that it extends about 2 feet above the uppermost perforations. The well <br /> was then sealed with a 2 foot bentonite pellet plug and grouted to the surface;vith a mixture <br /> of neat cement and.5 percent bentonite. Each well was completed nearly flush with the <br /> surface and enclosed within a subsurface locking christy box. Each well was also equipped <br /> ' with a locking pressure cap to avoid the possibility of vandalism. Following completion of <br /> the.wells the location and elevation of each well was surveyed relative to an established <br /> benchmark. The elevation of the water table was subsequently determined'by subtracting <br /> -i' <br /> the depth to water from the elevation of the top of the casing. As a result the direction of <br /> groundwater movement and relative gradient can be determined. Figure .4 shows the <br /> approximate elevation of the water table and the direction of groundwater movement. <br /> 4.1 Water Sample Collection <br /> Within hours of well completion, each monitoring was developed by purging a sufficient <br /> amount of water to remove all suspended material from the well. Approximately 55 gallons <br /> of water was removed from each well and contained and stored on site until an analysis of <br />--- — --- -- --- -------the water could be obtained. — -------- — -- ------- <br /> f . <br /> f` 7 <br /> iw�r <br /> iv <br />