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Arsenic Treatment Project Experience

Newmont Mining Corporation TS4 Potable Water
Treatment, Nevada

Tetra Tech RTW designed and supervised construction for a 50 gpm arsenic treatment system for potable water supply, utilizing coagulation-assisted microfiltration technology to reduce the arsenic concentration from greater than 100 ppb to below the required maximum contaminant level of 10 ppb. The system utilizes a robust SCADA package to provide a reliable, automated treatment solution requiring very little operator time and effort.

Leeville Water Treatment Plant, Newmont Mining Corp.

Tetra Tech RTW designed and installed a reverse osmosis treatment plant for potable water at a new mine in northern Nevada. The system included a state-of-the-art reverse osmosis treatment skid for removing 300 ppb arsenic and calcite filters for adding buffering capacity to plant effluent.

Queenstake Mining Corporation

Tetra Tech RTW prepared an alternative analysis and conducted bench-scale testing for a treatment system to remove arsenic and antimony from a 5,000 gpm mine dewatering flow. The proposed arsenic treatment process includes coagulation with ferric chloride and sedimentation in lines settling ponds. Bench-scale results indicated that additional treatment of a portion of the flow would be required to meet requirements for antimony discharge levels. Thus, a second process train of granular ferric hydroxide media was designed for polishing of antimony concentrations. The project is awaiting funding for construction in 2007.

Dewatering Treatment Plant, Alaska Gold Company
Nome, Alaksa

Tetra Tech RTW is presently designing a state-of-the-art water treatment plant for installation in remote Nome, Alaska. Tetra Tech RTW provided on-site bench-scale testing to help identify options to treat and remove the high arsenic and antimony concentrations found in the dewatering water from this open pit mine. Research indicated that with proper chemical addition to manipulate oxidation potential and pH, both antimony and arsenic could be treated with a single pass through microfiltration. Tetra Tech RTW is presently preparing detailed construction and permitting documents for installation of this 700 gpm treatment facility during fall 2007.

SDWA and the Mining Industry
Elko, Nevada 

Tetra Tech RTW developed and presented classroom training for water system operators and managers regarding the SDWA (Safe Drinking Water Act) regulation. The class specifically addressed arsenic regulation and mitigation techniques for small systems such as those found at remote mining sites.

TS Power Plant, Potable Water System

The design team provide permitting and construction of a 1,500 gpm water supply well to supply potable water, cooling water, and construction water to this large power plant construction project. Slightly elevated concentrations of arsenic required treatment of the water for potable use. Tetra Tech RTW identified granular ferric media adsorption as the most application technology for this remote application. Tetra Tech RTW provided complete design, permitting, construction management, and equipment procurement on this project.

Potable Water Treatment Plant, Barrick Goldstrike Mines

Tetra Tech RTW designed a 120 gpm potable water treatment plant to tackle drinking water with greater than 100 ppb arsenic at this remote mine site. Bench-scale testing and onsite pilot testing helped to identify coagulation-assisted microfiltration as the optimal treatment alternative for this site. Tetra Tech RTW designed a highly automated treatment plant to incorporate the arsenic removal with ion exchange to remove hardness and radionuclides. The system operates on a robust SCADA package that allows for remote monitoring and operation.

Arsenic Mitigation, National Park Service Wind Cave & Mount Rushmore National Parks
South Dakota

Tetra Tech RTW developed a water quality sampling plan including arsenic speciation; evaluated water quality data; and, developed water supply and treatment alternatives for these two national parks. Tetra Tech RTW subsequently developed conceptual design for the recommended alternative. Treatment concerns included the need to meet requirements of a “Groundwater Under the Direct Influence of Surface Water”, the preference to not use chemicals for treatment, minimizing residuals, minimizing water loss, handling source water hardness and corrosivity, and operating with limited staff resources.

Treatment alternatives considered included modified conventional treatment (floc-sed); granular ferric or activated alumina absorption; ion exchange; RO; and coagulation-assisted microfiltration. Evaluation of alternatives included water balance, operational requirements, and capital and life cycle cost analyses.

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