Reclamation Research

Minnesota Department of Natural Resources is responsible for resource development (e.g. mining) by state constitution, school and university trust fund responsibilities (MN Statute 127A.31). We require mining practices that to the extent practicable minimize adverse impacts on water quality, dust generation, erosion, and watershed hydrology. Since the late 1970s, the Division of Lands and Minerals has conducted research related to environmentally sound mining of nonferrous and ferrous minerals, peat, and dimension stone. Research has been conducted in cooperation with University of Minnesota, industry, US Environmental Protection Agency, US Bureau of Land Management, US Army Corps of Engineers, and Western Governors' Association.


Cooperative Research

Cooperative Research for Environmentally Sound Mining (CR ESM)
The State Iron Ore Cooperative Research and Cooperative Environmental Research programs, with a mining industry match, provided funding to the Division of Lands and Minerals (LAM) to report results of environmental research projects. The Division has been conducting laboratory and field dissolution studies since the mid-1970s. Several studies have been in progress recently, but reporting was interrupted by environmental review responsibilities and retirements of key personnel. These studies include dissolution tests on rocks and tailings associated with nonferrous deposits in Minnesota and methods of mitigation applicable to both nonferrous and ferrous mine wastes.

Controlling mercury in taconite stack emissions
The taconite processing industry is Minnesota's second largest emitter of mercury to the atmosphere, surpassed only by coal-fired power generation. For Minnesota to reach its mercury reduction goals, the taconite industry will need to find ways to decrease mercury emissions from its ore processing facilities. The DNR has conducted and funded a variety of research projects on mercury reduction from the taconite industry.

Sulfate released from mining regions
Iron mining is a source of sulfate to nearby watersheds and has recently become a concern because sulfate reduction processes can increase methylmercury production under certain conditions. Methlymercury accumulates in fish tissues and is responsible for fish consumption advisories in the St. Louis River and in many other lakes and rivers across the state. Beginning in 2007, the DNR began investigating sulfate effects on methlymercury by sampling a wide variety of streams and rivers.

Humidity Cell Array

Humidity Cell Array

Why are we doing this research?
Until the late 1980's, little research had been done regarding environmentally sound management of wastes from hard rock mines. Due to interest in copper-nickel mining in Minnesota during the 1970s, the Copper-Nickel study was initiated to investigate this topic. This research was subsequently adopted by Lands and Minerals and continued in order to inform decisions regarding mine waste management. To some extent, research conducted at mines in other locations can be applied to mining in Minnesota, therefore literature work and site visits are helpful. However, many aspects of environmental problems related to mining are site specific, and must therefore be assessed under conditions occurring in Minnesota (e.g. geology, mining methods, climate, geography, hydrology, and socioeconomic conditions). That is, there are some aspects of environmentally sound mining that are best researched under the conditions expected in Minnesota. In addition, some long-term concerns can only be addressed by long-term experiments and governmental agencies are best suited to conduct studies of such duration. It should be noted that pertinent information can also be gained from monitoring of mine sites and provide insight on operational scale of mine waste management techniques.

Minnesota Department of Natural Resources, Division of Lands and Minerals performs research for the following purposes:

  1. Prediction of mine waste drainage quality
  2. Assessment of potential impacts of mining, associated mineral processing, and mine and mineral processing waste drainage, and
  3. Mitigation of mine and mineral processing waste drainage, and other contaminant release.

This research helps to provide a technical foundation for decisions regarding the environmental review and permitting of nonferrous and ferrous mines.

What have we done?

Field prediction of drainage quality from archean greenstone waste rock

Field prediction of drainage quality from archean greenstone waste rock

Drainage Quality from Mine Wastes
Minnesota has an extensive taconite mining industry. The mines, tailings, and waste rock produced during this mining cover more than 184 square miles (as of 2009). Despite the vast amount of these wastes, drainage quality problems have been minimal. Studies have been conducted to quantify the sulfate released with drainage from a tailings basin and to evaluate ground water quality impacts of disposing taconite tailings in existing open pits.

Potential for base and precious metal deposits are located in Northeastern Minnesota in a geological terrain called the Duluth Complex, which is composed of dark colored igneous rocks and geologic terrain called the Archean greenstone, composed of volcanic and sedimentary rocks. The Duluth Complex holds potential for development of copper-nickel, titanium, platinum group elements (PGE) and dimension stone resources. Related exploration activity for copper-nickel and PGE is also occurring in East Aitkin County in a geological unit that is related to the Duluth Complex. For more information, visit the MGS mineral potential webpage. Field drainage quality data have been collected from Duluth Complex waste rock in operational stockpiles, small scale test piles, and dimension stone quarries. Extensive laboratory testing has been conducted to better understand dissolution of Duluth Complex rock and tailings, generated by its processing. The greenstone belts are potential sources of base and precious metals. Dissolution of greenstone rock has been studied in the field and laboratory, in which dissolution of gold mine tailings from greenstone belts has also been examined. Dissolution testing of rock types outside of Minnesota has also been conducted with funding from the US Bureau of Land Management.

Evaluation of Predictive Tests
Several static and kinetic tests have been developed for predicting mine waste drainage quality. Static tests base predictions on solid phase analyses, while kinetic tests use data from dissolution tests on mine waste samples. Insight into static and kinetic test accuracy and interpretation has been gained as part of MN DNR testing of Duluth Complex rock and rock and tailings from greenstone formations. Studies on other rocks have further contributed to our understanding of these tests.

Creating Wetlands on Tailing Basins

Creating Wetlands on Tailing Basins

Mitigation Techniques
Mitigation techniques include methods to prevent mine drainage problems as well as treatment methods for water impacted by mining operations. The degree of mitigation required for mining wastes depends directly upon the potential for problematic mine waste drainage quality at a site. Appropriate methods of mitigation can be designed and optimized based, in part, upon the predicted drainage quality. Methods to prevent mine drainage problems include under water disposal of waste rock and tailings, creating wetlands over tailings, co-disposal of tailings and waste rock, adding alkaline materials to mine waste, and coating reactive surfaces to prevent reaction (microencapsulation).

Treatment can include the use of standard water treatment technologies (active treatment) or newer, lower maintenance options that use natural processes (passive treatment). Minnesota Department of Natural Resources, Division of Lands and Minerals designed a small active treatment that treats water from the research site while minimizing operation and maintenance.

Passive Systems

The Division of Lands and Minerals has also studied passive systems including wetland treatment, sulfate reducing bioreactors, alkaline treatment beds and the use of covers and liners to control the quantity of water entering or leaving mine waste facilities.

Wetland treatment system

Wetland treatment system

Improving Reclamation with Waste Products

This is a preferred option for sulfide-bearing mine wastes because it limits access of oxygen to the sulfide minerals present and therefore the reaction of these minerals. The Division of Lands and Minerals has examined this strategy, and modifications of it, in both laboratory and field tests. These experiments have focused on both empirical documentation of sulfide oxidation rates, but also interpretation of these rates in terms of known rates of oxygen diffusion through water.

Coarse taconite tailings without biosolids

Coarse taconite tailings without biosolids

Coarse taconite tailings with biosolids

Coarse taconite tailings with biosolids

Subaqueous disposal

This is a preferred option for sulfide-bearing mine wastes because it limits access of oxygen to the sulfide minerals present and therefore the reaction of these minerals. The Division of Lands and Minerals has examined this strategy, and modifications of it, in both laboratory and field tests. These experiments have focused on both empirical documentation of sulfide oxidation rates, but also interpretation of these rates in terms of known rates of oxygen diffusion through water.

Subaqueous disposal of sulfide bearing waste rock

Subaqueous disposal of sulfide bearing waste rock

Alkaline Solids

The mixing of alkaline solids with acid-producing mine wastes is intended to neutralize acid produced within the mine waste disposal facility. The Division of Lands and Minerals has examined this strategy in laboratory tests initiated in 1988 and in more recent field studies.

Please see the Reclamation Sections' list of publications This is a PDF file. You will need Adobe Acrobat Reader to download it. (249 kb) for more information on the research we have done.