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ADDITIONAL GROb..D-PATER CHARACTERIZATION Two additional monitoring wells are pla=ed for completion downgradient of the ponds between well P5 and wells P6 and P7 (Figure 1). As a result of the time hrame required to implement source control at the fatuity, i.e. subsurface injecdon and closure and/or rehabilitation of the ponds, two monitoring wcll5 will be installed to assess the potential for saline water migration in the direction of the seasonal pumping depression created by of£aite wells P6 and P7. Monitoring at the proposed location would accomplish several objectives. It will provide 2- means means to assess the hydraulic control afforded by pumping well P5. The wells will allow an assessment of the quality of the shallow and deep zones of the upper Laguna formation, and also a determination of seasonal trends in quality in these zones, at a location dowagradient of the ponds. Water levels in 'both wells would also be analyzed to determine vertical gradients during pumping and nonpumping seasons at a location away from the ponds. It is intended that the proposed wells, MW4A and MW4B, would be completed similarly to wells MW3A and MW3B, to allow monitoring at depths of approximately 150 to 160 feet, or the shallow zone of the upper Laguna, and at 200 to 210 feet, or the deep zone of the upper Laguna. The construction features of the proposed monitoring facilities are summarized below. Direr, rotary drilling methods are planned. Four inch casing is planned for installation in a minimum 12-inch diameter borehole. PVC schedule 40 flush threaded casing and screen are planned. The estimated test bole depth at the site is 220 feet; that test hole will be reamed and completed into monitoring well 413. The borehole for monitoring well 4A is estimated to be 170 feet deep. The estimated screen slot size is 0. 5; the streets in the shaLow well will be located from a depth of apprwdma a 150 to 160 feet and in the deeper well from a depth of about 200 to 210 feet. The anticipated filter pack is Lonestar 8 mesh (8 x 16) sand. Cement grout seals with five percent bentonite are planned. The shallower well will be sealed to a depth of approximately 152 feet, while the deeper well will be sealed to a depth of approximately 192 feet Bcatonite seals will be placed between the gravel envelope and the cement grout seals at approximately 152 to 155 feet in the shallow well and at aporoxitttately 192 to 195 feet in the deeper well. The wells will be developed by airlift pumping and swabbing techniques for a? minimum of six to tight hours each. The new monitoring wells will be equipped with dedicated pumping equipment Qllti'1Q0 !t9 IJJItJHJW