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
4.0 Results
4.1 Ceriodaphnia dubia Chronic Toxicity Test
TEST: 7-day chronic with Ceriodaphnia dubia OPERATORS: JW, TE, CL, AW
Start: 11/5/20 12:00
End: 11/11/20 12:40
Test Substance: 0.5 g ethanol/g SO4-treated Effluent
Client/Project: Elk Ridge Mining and Reclamation, LLC
Table 9: Summary results of C. dubia chronic toxicity test.
Treatment 0 20 40 60 80 100
%Treated Effluent
#alive/#exposed 10/10 10/10 8/10 9/10 5/10 0/10
%survival 100 100 80 90 50 0
Normalized repro/#females 41.7 42.1 28.9 21.5 6.8 0.3
exposed ±SD ±7.6 ±3.8 ± 13.8 ±9.8 ±4.0 ±0.7
Dissolved 02 range 7_0 6_6 6_5 6_4 6_3 6_2
(mg/L) 6.1 4.4 3.4 3.1 2.8 2.7
pH range(SU) 8_4 8_7 8_8 8_9 8_8 8_8
8.1 8.5 8.6 8.6 8.7 8.7
Conductivity range 367 1158 2347 2708 3430 3890
(pmho/cm) 341 1031 1766 2389 3040 3630
Temperature range(°C) 24.6 24.5 24.8 24.7 24.3 24.5
23.6 23.3 23.1 22.8 23.8 23.5
Statistical Analysis:
Survival:
NOEC (Fisher Exact/Bonferroni-Holm) = 80% 0.5 g ethanol/g SO4-treated Effluent
IC25(ICp Method) = 65.7% 0.5 g ethanol/g SO4-treated Effluent (95% C.I. 36.7 to
81.3)
Normalized Reproduction:
NOEC (Steel Many-One Rank Sum) = 20% 0.5 g ethanol/g SO4-treated Effluent
Approved: Smoothed IC25 (Manual Calculation) = 36.4% 0.5 g ethanol/g SO4-treated
Effluent (95% C.I. unavailable)
Not Used: IC25(ICp Method) = 36.1% 0.5 g ethanol/g SO4 (95% C.I. 28.8 to 47.1)
GEI Consultants,Inc. 11 February 2021
Ecological Division Whole Effluent Toxicity Test Report
Stantec-Elk Ridge Mining and Reclamation,LLC