2021-05-18_HYDROLOGY - C1981019

• Permit No: C1981019
• IBM Index Class Name: Hydrology
• Doc Date: 5/18/2021
• Doc Name: Correspondence
• From: Tri-State Generation and Transmission Association, Inc.
• To: DRMS
• Email Name: ZTT
• Email Name: JDM
• Media Type: D
• Archive: No

DocuSign Envelope ID: D07924E6-3D94-4398-A066-B683COBAB33E
4.3 Ceriodaphnia dubia Chronic Toxicity Test
TEST: 7-day chronic with Ceriodaphnia dubia OPERATORS: AW, JMS, LAG, TE, CL, JW
Start: 11/17/20 14:35
End: 11/25/20 13:40
Test Substance: 0.25 g ethanol/g SO4-treated Effluent
Client/Project: Elk Ridge Mining and Reclamation, LLC
Table 11: Summary results of C. dubia chronic toxicity test.
Treatment 0 20 40 60 80 100
% Treated Effluent
#alive/#exposed 10/10 10/10 9/10 0/10 0/10 0/10
% survival 100 100 90 0 0 0
Normalized repro/#females 21.4 29.2 28.2 0.0 0.4 0.0
exposed ±SD ±17.0 ±16.3 ±10.7 ±0.0 ±1.3 ±0.0
Dissolved 02 range 6_9 6_5 6_2 6_1 6_2 6_0
(mg/L) 6.5 5.5 5.5 5.6 5.8 6.0
pH range(SU) 8_3 8_8 8_9 8_8 9_0 8_8
8.0 8.3 8.8 8.7 8.7 8.8
Conductivity range 381 1263 2088 2841 3780 4140
(pmho/cm) 348 474 1851 2385 3396 4110
Temperature range(°C) 24.7 24.7 25.2 25.2 25.3 25.0
23.6 23.8 24.2 23.4 23.4 24.4
Statistical Analysis:
Survival:
NOEC (Fisher Exact/Bonferroni-Holm) = 40% 0.25 g ethanol/g SO4-treated Effluent
IC25(ICp Method) = 43.3% 0.25 g ethanol/g SO4-treated Effluent (95% C.I. 36.7 to
45.0)
Normalized Reproduction:
NOEC (Dunnett Multiple Comparison) = 40% 0.25 g ethanol/g SO4-treated Effluent
Approved: Smoothed IC25 (Manual Calculation) = 48.6% 0.25 g ethanol/g SO4
treated Effluent
Not Used: IC25(ICp Method) = 45.0% 0.25 g ethanol/g SO4-treated Effluent (95% C.I.
34.8 to 45.1)
GEI Consultants,Inc. 13 February 2021
Ecological Division Whole Effluent Toxicity Test Report
Stantec-Elk Ridge Mining and Reclamation,LLC