By Hung Nguyen Lime Treatment of Acid Mine Drainage at Leviathan Mine, California

Content 1. SITE DESCRIPTION1. Site Description 2. History of Contaminant Release 3. Lime Treatment Solution 4. Evaluation Results 5. Summary

1. SITE DESCRIPTION 1. Site Description  Location -The Leviathan Mine site is at about 2200m above sea level, on the eastern slope of the central Sierra Nevada Mountains in Alpine County,California, USA -The site occupies approximately 102 hectares.  Activity -The Leviathan Sulfur Mine is a former copper and sulfur mine. -Mining operation scheme 1860s Active 1872 Inactive 1935Active intermittently 1951 Converting underground workings into an open pit mine operation => 22m tons waste rock 1962inactivenow

1. SITE DESCRIPTION 2. History Contaminant Releases - Hazardous substances which are released directly from The Leviathan Mine property included Acid Mine Drainage (AMD) from the floor of mine pit flowing west into Leviathan Creek and Acid Rock Drainage(ARD) from Delta Seep, Aspen Seep into Leviathan and Aspen Creeek respectively. - Historically, the concentrations of five primary target metals, aluminum, arsenic, copper, iron, and nickel in the AMD and ARD released to Leviathan and Aspen creeks have exceeded EPA discharge standards up to 3,000 fold.

1. SITE DESCRIPTION 2. History Contaminant Releases - Major environmental damage occurred at the mine during the period of open pit mining ( ). - Snowmelt, rain, and groundwater interact with the waste rock, creating sulfuric acid - The concentrations of toxic metals resulted in fish and insect kills in Leviathan Creek, Bryant Creek, and the east fork of the Carson River - Various efforts were made between 1954 and 1975 to characterize the impacts of Leviathan Mine on water quality

1. SITE DESCRIPTION 3. Lime Treatment Solution - A simple chemical process where low pH AMD/ARD neutralized by using lime to precipitate dissolved iron, the main component of AMD and ARD. - In the active lime treatment system, the precipitation process is either performed in a single stage (monophasic mode), or two stages (biphasic mode). Ca(OH)2 (s) + Me2+/Me3+ (aq) + H2SO4  Me(OH)2/Me(OH)3(s) + CaSO4 (s) + H2O Where Me2+/Me3+ = dissolved metal ion in either a +2 or +3 valence state

1. SITE DESCRIPTION 3. Lime Treatment Solution Active Lime Treatment System Monophasic Schematic

1. SITE DESCRIPTION 3. Lime Treatment Solution Active Lime Treatment System Biphasic Schematic

4. Evaluation Results - The treatment systems were evaluated independently, based on removal efficiencies for primary and secondary target metals, comparison of effluent concentrations to EPA-mandated discharge standards. Removal Efficiencies for the Active Lime Treatment System - Monophasic Operation Target Metal Number of Sampling Events Average Influent Concentrat ion (μg/L) Average Effluent Concentrat ion (μg/L) Average Removal Efficienc y (%) Range of Removal Efficiencies (%) Aluminum7107, to 99.8 Arsenic73, to 99.9 Copper72, to 99.7 Iron7456, to Nickel72, to 99.3 Secondary Water Quality Indicator Metals Cadmium to 99.7 Chromium to 99.8 Lead to 89.8 Selenium to 94.4 Zinc to 99.6

4. Evaluation Results Target Metals Maximum (a) (μg/L) Average (b) (μg/L) Primary Target Metals Aluminum4,0002,000 Arsenic Copper2616 Iron2,0001,000 Nickel84094 Secondary Water Quality Indicator Metals Cadmium Chromium Lead SeleniumNo Standard5.0 Zinc210 Target Metal Number of Sampling Events Average Influent Concentra tion (μg/L) Average Effluent Concentra tion (μg/L) Average Removal Efficienc y (%) Aluminum12/1381,0001, Arsenic12/12, Copper12/12, Iron12/1461, Nickel12/17, Cadmium12/ Secondary Water Quality Indicator Metals Chromium12/ Lead12/ Selenium12/ NC Zinc12/11, Removal Efficiencies for the Active Lime Treatment System - Monophasic Operation EPA Discharge Standards

5. Summary - Lime treatment is applicable to any waste stream containing metals - Metals typically treated include aluminum, arsenic, cadmium, chromium, copper, iron, lead, nickel, and zinc. - Active lime treatment appears to be applicable in situations where flow rates are high and the treatment season is short. The system can be operated in house with a structure heated to temperatures above freezing. - However, lime treatment systems are maintenance intensive and have to be monitored regularly to maintain proper operating conditions.

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