GENERAL34630 - Laserfiche WebLink

Home Browse Search

Dissolved Solids There aze no receiving stream standazds for total dissolved solids. However, the Division considered the additional total salt load on North Thompson Creek. The average (1995 through 2001) September (low stream flow conditions) concentrations of total dissolved solids in North Thompson Creek rose from 138 mg/1 above the mine azea to 222 mg/1 below the mine azea, an increase of 62%. The September 8, 2002 upstream concentration was 140 mg/1 and downstream concentration was 215 mg/1. The concentration of total dissolved solids in Mine No. 1 dischazge of September 8, 2002 was 1580 mg/1. The concentration of total dissolved solids in Mine No. 3 dischazge of the same date was 1140 mg/1. The concentration of total dissolved solids in combined portal dischazge (Outfall 001) was 1501 mg/l. Thus Outfall 001 likely contributed to the rise in concentration between the upper and lower stream monitoring stations. Derived from average flow rates and concentrations, the highest level of salt dischazge at Outfa11001 recorded from 1995 through 2002 was 0.4 tons of salt per day (1997). The 2001 contribution was 0.21 ton of salt per day to North Thompson Creek. During 2002, the average flow rate at Outfa11001 was 22.4 gpm and the average TDS concentration was 1,388 mg/1. This equates to a salt loading of 0.19 tons per day to North Thompson Creek. The CDPHE considers anything less than 0.4 ton per day as a no salt dischazge. Annual salt loading at the 2002 rate would be 69.4 tons. Depletion of Springs and Seeps Mining may cause the depletion of springs and seeps above the undermined azeas. A spring and seep survey conducted by the mine has only identified two springs within the five-yeaz mine plan azea. Both springs (designated on the mine subsidence map) flowed less than one gallon per minute, except during the spring, when site SP-2 flows of 20-40 gallons per minute were reported. Both springs flow from the Upper Sandstone and aze not adjudicated. Based on the low flow and poor quality, it does not appeaz that the springs were, or aze, a significant component of the surface water regime. On May 20, 2003, the flow of Spring 2 was estimated at 0.125 gallon per minute. Should mining have diminished Spring 2 flows, they would now re-appeaz in Mine No. 1 discharges. There would, thus, not be a significant impact to the surface hydrologic balance. Water Balance There was aone-time loss from the pre-mining hydraulic regime to impounded water of the underground reservoirs from flooding of the areas of coal extraction after pumping ceased. An estimated 363 acre feet in Mine No. 1 and 94 acre feet in Mine No. 3, are stored. Dischazges from the Mine No. 1 portal were noticed on Apri128, 1988, and from the Mine No. 3 portal on June 26, 1995. Since these times, mine inflows have been in balance with mine discharges. There maybe some increase to North Thompson Creek surface flows from diversion of upper groundwater to the portal dischazges at the expense of underground recharge of aquifers. Although it is not likely that all of the mine discharge water originates in the aquifers, even this maximum dischazge would not 29