2021-09-16_HYDROLOGY - M2012032

• Permit No: M2012032
• IBM Index Class Name: HYDROLOGY
• Doc Date: 9/16/2021
• Doc Name: Substitution of TOC
• From: Ouray Silver Mines
• To: DRMS
• Email Name: LJW
• Media Type: D
• Archive: No

Ouray Silver Mines, Inc.
1900 Main St. Unit 1
PO Box 564
Ouray, CO 81427
To: Colorado Division of Reclamation, Mining& Safety
1313 Sherman Street, Rm 215 SEP 1 ��21
Denver, CO 80203 DIVISION OF r"7C
LA
From: Todd Jesse, Environmental Specialist O MINING AND SAFEMTYATION
Date: September 6, 2021
Subject: M2012032 TR15 Substitution of TOC for Division Requested Xanthate Analysis During
Mill Commissioning
Dear Mr. West,
In the approval for TR15 for mill commissioning and certification the Division of Reclamation, Mining
and Safety (DRMS)requested analysis for Xanthate, Creosol, and Ethyl Glycol data during
commissioning for baseline characterization:
1. Process Water within the Mill Circuit
a. Submit two samples taken from within the mill circuit as a baseline characterization.
i. Samples will be collected from each of the two circuits and the process water tank
twice during mill commissioning, once early in the introduction of ore, and once
late in the commissioning process to evaluate mill water quality.
b. Analytes will include the currently approved constituents for groundwater and
underground water quality as well as Xanthate, Cresol and Ethyl Glycol.
OSMI has discussed xanthate analysis with several labs, including ACZ, Pace Analytical, Test America,
Eurofin and Colorado laboratories, none of whom are able to perform xanthate analyses. OSMI
understands that the intent of the requested analysis is to characterize mill chemical concentrations in
tailings for disposal considerations. OSMI has not been able to identify a lab to perform the requested
analysis, nor has OSMI been able to identify what standards the results might be compared against. There
are no standards for xanthates, glycols, or creosol in in Colorado Regulation 41 (The Basic Standards for
Groundwater)nor in Regulation 31 (The Basic Standards and Methodologies for Surface Water).
Given the difficulty in finding a laboratory to perform these analyses,the lack of regulatory thresholds
surrounding the glycol and xanthate, and the DRMS desire to evaluate mill fluids for the presence of mill
chemicals,OSMI proposes that total organic carbon be used as a substitute. Total organic carbon(TOC)
in the mill water is expected to be low prior to the addition of organic chemicals during beneficiation.
During pre-feasibility scale metallurgical testing, pan rinsate was analyzed for total organic carbon
(results attached)with concentrations ranging from 6.5 mg/L in zinc cleaner tailings (sample ID 235688
WW)to 27.9 mg/L rougher tailings(sample 235689 WW), with 14.72 mg/L in lead cleaner concentrate
tailings(sample 236163 WW). Total organic carbon is an indicator of process fluids, however TOC does
not indicate whether or not a substance will need to be disposed of in a hazardous waste facility. Given
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