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Environmental Protection Plan, Schwartzwalder Mine <br />9-41 <br />(iv).1 Evaluation of Changes in Mine Water Quality with Depth <br />Depth profiles of temperature, pH, ORP, and specific conductance have been prepared for the flooded <br />shafts to evaluate the chemistry of mine water with depth (Whetstone, 2007). Profiles for the initial <br />flooding of the mine between 2001 through 2003 indicate that the water column was generally well mixed <br />with weak to moderately oxidizing ORP (83 to 517 mV) at depths of several hundred feet below the surface <br />of the mine pool. Profiles of pH for the same period of time showed slight variation and were near neutral. <br />Profiles of specific conductance and temperature displayed greater fluctuation than pH, and appear to have <br />been affected by currents on levels intersecting permeable structures. <br />Depth profiles for the upper 40 feet of the mine pool were also prepared for data collected on November <br />12, 2007 when the water level was at 6,576.9 feet elevation. The 2007 profiles indicate that the ORP has <br />decreased substantially from the initial filling flooding period. ORP was measured to be 52.8 mV at a <br />depth of 4 feet and decreased to 22.8 mV at 40 feet. The pH of the water was near neutral (6.77 to 6.85). <br />Temperature (17.43 to 17.48 C°) and electrical conductivity (3,443 to 3,446 µS/cm) varied insignificantly <br />with depth (Figure 9-6). <br />2 <br />0- <br />4109C.090807 Whetstone Associates