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Schwartzwalder Mine -Hydrologic Evaluation of Mine Closure and Reclamation 18 <br />Table 9. Calculation of Vertical Gradients in Shallow Bedrock <br /> Elevation Mid-Point Vertical <br />Date Well Head Elevation y, -Yz HrHz Gradient <br /> H Hl-Hz / -- z <br /> MW10 7326.66 7323.51 241 <br />104 15.28 I 0.15 <br />5/27/99 MW11 731138 721927 . <br /> <br /> MW10 7322.61 7321.49 10222 17.44 0.17 <br />9/21/99 MW 11 7305.17 7219.27 <br />73ao <br />7320 <br />c 7300 <br />2 <br />O <br />F <br />a <br />w 7280 <br />J <br />W <br />J <br />W <br />7 <br />W <br />J <br />728[ <br />6 <br />3 <br />7241 <br />72z. <br />7zoo <br />Dec-98 Jan-99 Mar-99 Apr-99 Jun-99 Aug-99 9eP~9 <br />7212.3 <br />~ in~zoo <br />lan-08 Feb-00 Nov-07 <br />Figure 9. Seasonal Variation in Water Levels in Deep Bedrock Monitoring Well MW11 <br />Based on the data from Monitoring wells MW10 and MW11 it can be concluded that: <br />1. The water table in bedrock is typically within about 100 feet of the ground surface. <br />2. Shallow bedrock groundwater levels fluctuate seasonally and the thickness of the unsaturated zone <br />decreases to about 70 feet in the spring. <br />3. The hillside above the mine remains essentially saturated throughout the year. Therefore the <br />hydraulic conductivity of the bedrock must be low. <br />4. Shallow groundwater flow in bedrock is predominately vertical. The high vertical gradient (15 to <br />17 percent) indicates that vertical hydraulic conductivity is low. The vertical hydraulic <br />conductivity of bedrock, however, is probably greater than horizontal hydraulic conductivity <br />because of steeply dipping foliation and near vertical orientation of major structural features. <br />5. The specific yield of bedrock is low. Water levels in MW 11 rose approximately 50 feet during the <br />spring of 1999. If it is assumed that recharge to the system by infiltration of meteoric water is <br />about 3 inches during the spring, the drainable porosity of the rock is calculated to be 0.005, or <br />Whetstone Associates <br />4109B.071116 <br />