Laserfiche WebLink
Environmental Protection Plan, Schwartzwalder Mine 9-33 <br />(iv) Water Quality in the Underground Mine <br />Water quality data for the flooded underground mine are available from 128 samples that were collected <br />from the # 2 and #3 Shafts between June 2000 and October 2008. Water quality in the shafts was <br />monitored on a monthly basis between June 2000 and July 2001, and on a quarterly basis from July 2001 to <br />May 2003. One sample of mine water was collected from the # 2 Shaft in April of 2005 and starting in <br />June 2007, water quality monitoring of the flooded mine resumed on an approximately quarterly basis. <br />Mine water samples were collected at several depths in the flooding shafts during each monitoring event <br />between 2001 and 2003. The samples were obtained using a thief-type sampler to collect water from <br />discrete intervals below the surface of the mine pool. The sampled depths varied from 0 to about 900 feet <br />below the top of the pool depending on the distance of the shaft access point to the water surface. Starting <br />in 2005, only one sample was collected from near the surface of the mine pool during each monitoring <br />event. <br />Water quality analyses for the flooded mine indicate that the water is a strongly-buffered calcium- <br />magnesium-sodium-sulfate water with near neutral pH (median value = 7.17), and high concentrations of <br />total dissolved solids (about 3,000 mg/L). Major contributors to TDS include sulfate (520 to 2,060 mg/L), <br />bicarbonate (270 to 482 as CaCO3), calcium (71 to 413 mg/L), sodium (140 to 225 mg/L) and magnesium <br />(37 to 271 mg/L). The major ion composition of water in the mine is presented graphically on Figure 9-5. <br />Several constituents have been detected in mine water samples at concentrations above Colorado <br />groundwater standards (Table 9-1). Constituents with elevated concentrations include TDS, sulfate, <br />antimony, arsenic, iron, manganese, molybdenum, thallium, uranium, and radium 226. The state standard <br />for TDS in groundwater with background concentrations less than 500 mg/L is 400 mg/L or 1.25 times the <br />background level, whichever value is least restrictive. The TDS content of mine water samples has ranged <br />from 115 during the initial flooding of the mine to a maximum 3,420 mg/L in April 2005. Since 2001, the <br />TDS content of mine water has fluctuated near 3,000 mg//L. Sulfate is a major component contributing to <br />TDS (2.9 to 2,060 mg/L) and has been consistently elevated above the domestic water supply drinking <br />water standard of 250 mg/L since the June 2000. Dissolved manganese (<0.01 to 5.59 mg/L), molybdenum <br />(0.60 to 3.40 mg/L), uranium (0.1 to 61 mg/L), and thallium (<0.001 to 0.011 mg/L), and total radium 226 <br />(0 to 219 pCi/L) concentrations generally exceed the lowest potentially applicable standards of 0.05 mg/L, <br />0.035 mg/L, 0.03 mg/L, 0.002 mg/L and 5 pCi/L respectively. Less frequently, dissolved iron, mercury <br />and arsenic have been detected at levels above potentially applicable groundwater standards of 0.3 mg/L, <br />0.002 mg/L, and 0.01 mg/L respectively. Water quality data and summary statistics for the flooded mine <br />workings are presented in Table 9-7. <br />r <br />4109C.090807 Whetstone Associates