2016-08-02_HYDROLOGY - C1981018 ‎(3)‎

• Permit No: C1981018
• IBM Index Class Name: Hydrology
• Doc Date: 8/2/2016
• Doc Name Note: ‎(CO0038024)‎
• Doc Name: 2nd Quarter 2016 DMRs ‎(CO0038024)‎
• From: Blue Mountain Energy, Inc
• To: DRMS
• Annual Report Year: 2016
• Report Quarter_Month: 2
• Permit Index Doc Type: DMR’s
• Email Name: CCW
• Email Name: JRS
• Media Type: D
• Archive: No

S. Wanstedt
May 20, 2016
Page 3
The single LC50 point in Figure 1 for the Deserado Mine is at approximately 4,000 mg/L chloride;
whereas, the TRE reference toxicant LC50 values range from 3,100 to 3,500 mg/L with a mean of
3,300 mg/L. Therefore, the toxicity of the Deserado Mine sample (based on chloride) was less (i.e.,
higher LC50) than what would be expected compared to our in-house database. The lower toxicity
suggests that something else may be reducing the chloride toxicity. Since it is not prudent to draw
conclusions based on only one sample point, it would be desirable to conduct several more tests
including the 50% dilution (allowing calculation of a point estimate) using samples with known chloride
concentrations.
The chart for P. promelas is presented below (Figure 2):
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Test Dates
♦ Ref Tox 96h LC50 LCL UCL • Deserado Mine 96h LC50
Figure 2. 96h LC50 as mg/L chloride for P. promelas, reference toxicant and Deserado Mine
data
The two Deserado Mine points in Figure 2 fall within the upper and lower control limits for TRE's
reference toxicant data for chloride and fathead minnows, suggesting that chloride is the primary (and
possibly sole) toxicant in Deserado Mine samples for this species. This could be confirmed by
conducting several more tests including the 50% dilution using samples with known chloride
concentrations.
An additional option to help confirm the cause of toxicity would involve preparing a total dissolved
solids (TDS) mock effluent. With this, we could explore whether non-TDS toxicity plays a role, or if
toxicity is due to chloride and other TDS ions. This would be done by testing a TDS mock effluent,
prepared from ultrapure water to match the Deserado Mine sample concentrations of the seven
common TDS ions (Ca, Mg, Na, K, SO4 2-, Cl-, and HCO3 ). A Deserado Mine sample would be tested
concurrently. If the resultant toxicity is similar between the two studies, there would be support for our
TRE Environmental Strategies, LLC