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There is no indication of springs or large seeps in this area suggesting that recharge to <br />these formations is dominated by the Dolores River Valley. <br />Based on the deep well drilled in Section 35 (T44N, R19W), the Wingate Formation west <br />of the river in an artesian aquifer. This data indicates that recharge for the Wingate <br />occurs along the flanks of the Dolores River /Lisbon Valley anticline to the southwest of <br />the site. <br />8.4 Groundwater Monitoring <br />Monitoring groundwater quality to specifications of Resource Conservation and <br />Recovery_Act LRCRA) or requirements of the DRMS is difficult. Simple concepts of up- <br />gradient and down - gradient monitoring wells at locations that could provide early <br />warning system were problematic at best and not representative of subsurface conditions <br />at worst. Cotter instructed crews drilling exploration holes for delineation of ore deposits <br />to note zones of "moisture." Figure T2 shows a 3 -D diagram of the site topography and <br />geology including the location of exploration borings that targeted the ore - producing <br />zone in the Salt Wash Sandstone. <br />This moisture data provides valuable insights on the hydrogeology of the region. The <br />upper surface of Figure T2 shows the topography of the site. The middle layer is the ore <br />zone within the upper sandstone unit of the Salt Wash Member of the Morrison <br />Formation, and the lower layer is the Entrada Sandstone based on structural contours <br />shown on the Geologic Map for the Horse Range Mesa Quadrangle (Cater, 1955). These <br />test borings were drilled with air rotary drilling rigs and the drillers were instructed to <br />note wet or moist zones based on observations of the drill cuttings. While this is a <br />subjective observation and the results are not indicative of saturated conditions, it does <br />indicate where water, under either saturated or unsaturated conditions, is located in the <br />subsurface but provides no indication of the mobility of the groundwater. These "moist" <br />zones based on the drill logs are shown on Figure T2 as blue ovals. <br />While the exploration holes targeted the ore zone, several borings continued through the <br />ore zone and into the upper portion of the Salt Wash Formation. The majority of the <br />exploration holes are dry. However, there are a few "moist" zones located above the ore <br />horizon in the Brushy Basin Formation and below the ore zone in the Salt Wash <br />Formation. One boring encountered a moisture zone located within the ore horizon. <br />During active mining, no moisture was detected from this moist zone. <br />In hydrogeologic terms, the Brushy Basin member is defined as an aquitard - a term <br />coined to describe the less - permeable beds in a stratigraphic sequence (Freeze and <br />Cherry, 1979). This is a classic definition of a geologic unit incapable of providing a <br />pathway for environmental exposure or recharge for the underlying Salt Wash <br />sandstones. As previously noted, the Brushy Basin is a rock unit dominantly comprised <br />of bentonitic shales (impermeable) with discontinuous lenses of low- permeable <br />sandstones and conglomerates. Any water in this formation would cause the bentonite <br />shales to swell and isolate lenses of sandstone and conglomerate where water could <br />O'Connor Design Group Inc. T - 14 <br />