Abandoned Mine Workings in Western USA – Legal, Organisational and Technical Challenges

There is an old saying that “mining is not a one-man operation”. This is borne out by the ongoing dialogue that is needed across the disciplines to manage the environmental issues associated with the mining life cycle at a local and wider level. Given the global nature of the mining industry we now need to develop a productive outcome by looking beyond national boundaries in order to gain a deeper understanding of the challenges that are facing countries other than our own.

Introduction

Dealing with the legacies of the mining industry is a task that varies enormously according to location and regional specifics will always have a huge role to play. The ISO is currently working on a new standard headed “Managing Mining Legacies” that is aimed at standardising the global approach to the inherited liabilities of the mining industry by laying down minimum requirements and ensuring real transparency. The contents of the new standard will be available for discussion in more detail once its final revision has been completed. It should be noted at this point that in 2020 the second-named author of this paper was appointed chairman of the DIN Mirror Committee on Post-Mining.

Tackling the challenges posed by abandoned mine workings and the post-mining era in a targeted and cost-effective manner calls for a level of expertise that in many respects can only be provided by ongoing exchange between scientists and practitioners from every corner of the globe. It is against this background that the writers of this paper have used a research residence completed by the first-named author at the Research Center of Post-Mining (FZN) at TH Georg Agricola University (THGA), Bochum/Germany, in order to further expand on this theme.

The USA (see map extract) can look back on a long history when it comes to the mining and extraction of raw materials. It may be assumed that in the western part of the country mineral resources such as turquoise, coal and clay were already being mined a thousand or more years ago. Indeed the indigenous peoples were mining copper even before the Spanish conquerors appeared in the region in the 16th century. The arrival of the Spanish also led to an upturn in mining activity (1, 2).

The extraction of natural resources on an industrial scale only commenced after the Mexican-American War of the 1840s. At this point the focus was on metal resources, such as gold, silver and copper, and on coal and iron for the fast-developing railway network. These long-forgotten mining activities have left behind a legacy that for many years has posed a significant risk for the environment and for public safety and security in certain regions of the country. In fact cases are being reported even today of people being fatally injured as a result of falling into abandoned mine shafts and unprotected mine workings.

In 2013 the U.S. Department of the Interior (DOI), as represented by the Bureau of Land Management (BLM), responded to this situation by adopting the Abandoned Mine Lands (AML) programme (3) whose aim was to increase public safety around abandoned mine workings in western USA and also to eliminate, or at least to minimise, the impact of former mining activities on water, air and soil quality. The Office of Surface Mining, which operates within the DOI, has also developed a programme to manage abandoned open-pit workings that have been left by the hard coal mining industry (4).

Abandoned mine workings in western USA

The AML operated by the BLM covers the eleven western U.S. States of Alaska, Arizona, Colorado, Idaho, California, Montana, Nevada, New Mexico, Oregon, Utah, and Washington (Figure 1). In these States mining permits for operations on public lands have always been issued by the BLM. For the eleven western U.S. States the BLM maintains a number of cadasters or registers that record all the abandoned mining sites that exist on public lands, these being the property of the USA. Most of these consist of old ore mines in solid bedrock.

In the other States metal ore mining is mainly associated with freehold property and so mining liabilities of this kind are not generally accounted for in State-managed registers.

There is a general concentration of thousands of old mine sites in the mining regions of the Rocky Mountains in the western States and also in the Appalachians to the east of the country (Figure 1).

Figure 2 presents a graphical overview of the abandoned mine sites that are managed by the BLM. By 2017 the BLM had identified some 52,300 sites in the western States of the USA, this representing a total of 97,900 attributes such as mine shafts, adit entrances, surface cave-ins, water outlets, spoil tips and the remains of mineral processing and surface facilities (5).

The BLM has stated that only about 20 % of these sites have been remediated or secured in such a way that no further stabilisation or recultivation measures are required (these sites are assigned to the categories “Action Completed” and “No Action”). The remaining 80 %, which represents more than 40,000 abandoned mining sites, are in need of further investigation or are presently in various stages of restoration (“Maintenance and Monitoring”, “In Progress”, “Final Closeout” and “Planned”). A stocktaking exercise is required at more than 36,000 of the sites (“Needs Analysis”) before any further decisions can be taken. The data held in the AML Site and Attributes Inventory are provisional in nature and are currently being updated. In addition to the BLM registers there are also similar records held by the individual States which in some cases also include abandoned mine workings on private and on government-owned property. This often results in contradictory or disputed case numbers.

Legal situation

In the USA the BLM now grants mining permits for government-owned property by way of public auction. This also applies to licences for the extraction of oil and gas. In addition to federal lands there are also many areas that are in the ownership of individual States, local counties, community authorities and private companies. Particularly worth mentioning in the last-named group are the railroad companies that in the 19th century were given land by the national government in order to develop their railway network. These “Land Grants” take the form of areas each measuring one mile square (about 259 ha) that were assigned to the railroad companies in blocks measuring 20 to 50 miles in length (32 to 80 km) and interchangeably to the right and left of the railway track.

Because of the multi-layered terms of reference of the various bodies involved the circumstances that apply tend to be very inconsistent from a mining legislation point of view and mine operators are required to obtain official permits from a number of different authorities. In addition to those agencies that grant licences for exploiting the deposits there are various other bodies with responsibilities in this area, e. g.:

• State and Federal Environmental Protection Agencies (EPA), particularly for the control of dust emissions;
• the U.S. Army Corps of Engineers (USACE), which is responsible for waterways, receiving waters and dams;
• the Mine Safety and Health Administration (MSHA), which is responsible for occupational safety and accident prevention;
• the U.S. Forest Service (USFS);
• the U.S. Fish and Wildlife Service (FWS);
• the U.S. Department of Transportation (DOT);
• various other state, county and local authorities;
• state and federal radiation protection authorities that oversee the mining of radioactive minerals; and
• state mining authorities and the Federal Office of Surface Mine Reclamation and Enforcement (OSMRE).

These diverse authorities with their bewildering and at times overlapping responsibilities make the mine licensing process very difficult indeed. Federal legislation prescribing the recultivation of open-pit mining sites, the “Surface Mining Control and Reclamation Act” (SMCRA), was only introduced in 1977 (6). Prior to this date, the so-called “pre-law status”, there was generally no obligation to rehabilitate and reclaim mines in the USA. Mine operators simply walked away from their exhausted or unworkable deposits – hence the huge number of discarded and abandoned mining installations. The adoption of the SMCRA led to the establishment of the Office of Surface Mine Reclamation and Enforcement (OSMRE) whose three main functions are as follows:

1. Regulating active coal mines;
2. reclaiming abandoned mine lands; and
3. providing technical support, instruction and technology development.

According to the SMCRA the OSMRE covers five areas of responsibility:

1. Guideline setting competence for the quality of the recultivation measures;
2. licensing procedures for surface mining;
3. monitoring of financial recultivation provisions;
4. mining supervision and policing powers; and
5. ensuring that mining interdiction rules are being met at particularly sensitive sites, e. g., national parks.

The SMCRA lays down a number of important principles as far as recultivation is concerned. According to these, recultivated areas and similar have to be restored in such a way that their usage quality is an improvement on that which existed before mining commenced (“higher and better post-mining land use”). This transformation of the landscape can hardly be implemented in desert areas, among other places, where climate conditions are such that any plant growth would be difficult to achieve even after the recultivation phase. Another basic requirement involves the restoration, as far as possible, of the original topography (approximate original contour – AOC). This effectively prohibits the established practice of bulldozing hilltops and depositing the overburden into adjacent valleys, a practice referred-to as “mountaintop removal mining”.

The SMCRA also set up a fund whose purpose is to pay for the clean-up of abandoned mines that were closed down prior to 1977. These are known as “Pre-law mining liabilities” (7). This fund is financed by a fee that is levied on each tonne of coal extracted.

BLM work programme for closed and abandoned mines (the AML programme)

By the late 1990s the BLM had made a huge amount of progress in the identification of potentially dangerous mining installations, such as open mine shafts and adit entrances, surface cave-ins and harmful emissions of contaminated mine water (Figure 3).

There is no doubt that accidents in and around abandoned mine workings and cases of environmental damage lent a degree of urgency to the activities of the BLM. The erosion of public confidence in the level of responsibility displayed by mining companies and authorities could only be effectively addressed by creating transparency and a system of risk management, along with goal-oriented action and a well-directed public relations effort.

In this context it is well worth seeking out a U.S. Government website that carries the title “A threatening legacy” (9). This details the risks to human health and safety and to the environment that are posed by no fewer than 500,000 abandoned mine workings and decommissioned mining sites in the USA.

Particular mention should also be made of measures aimed at cleaning-up those drinking-water catchment areas that have been affected by disused mine workings. Also interesting from a German perspective are the efforts being made to establish partnerships with public institutions, local administrations, indigenous peoples and environmental organisations with a view to reducing the risks posed by abandoned mining legacies. Attention should also be drawn to the “best practice” procedures to which the BLM attaches considerable significance.

In addition to the efforts of the BLM all manner of interest has been displayed by private and non-governmental organisations in safeguarding and securing AML or preparing such sites for after-use projects. This includes, e. g., using mining-affected streams and lakes as fishing venues, transforming abandoned mining sites into hunting areas and developing recreational parks for walkers, cyclists and skiers. Given the current legal situation, however, there is a danger that a third party – namely one that is involved in recultivating, improving or even slightly altering mining legacy holdings for own use purposes – may be held legally and financially responsible for the consequences resulting from such an intervention as heir to the inherited burden and its reclamation. Proposals are now being drawn up for a “good Samaritan” ruling that would restrict the scope of this legal responsibility in order to promote private-sector initiatives for recultivation projects. However, the legislative process has still not made much progress in this direction.

Prioritisation of AML liabilities

The BLM puts the cost of rectifying some 22,000 or more sites that present a risk to public safety at over 400 M US$ (BLM, 2013). About 10 % of this sum alone is taken up as estimated expenses for the stabilisation and support measures that will be required. The BLM has laid down the following safety-relevant priorities for the abandoned mine sites according to their proximity to populated areas or major tourist locations (3):

1. High priority: locations that lie within a quarter of a mile (400 m) of a populated area or a school that is in active use. This involves nearly 600 sites.
2. Medium priority: locations that lie within 400 m of a previously populated site, e. g., a mining ghost town, a historic school or a venue with a strong visitor turnout. This involves about 650 sites.
3. Low priority: locations that are more than 400 m away from a populated area. This applies to the remaining 21,000 sites.

At the same time, special significance is also attached to mining liabilities that constitute a sizeable risk to public safety or to the environment and for which no legally responsible organisations or persons can be traced. These inherited liabilities are designated as “Superfund sites” in that a Superfund endowed with large sums of money has been set aside for recultivation measures. These Superfunds also cover industrial sites that have no historic connection with the mining industry.

Superfund sites are regulated under law by the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), which falls within the competence of the Environmental Protection Agency (EPA). The role of the EPA is to trace legally responsible persons, or their legal successors, who can be held accountable for the Superfund charges. This has proved successful in about 70 % of cases. The Superfund then provides for the remaining 30 %, this being financed from tax revenues. There are some 40,000 Superfund sites in all, about 1,600 of which have been given national priority (10). The latter figure includes 143 former mines, processing plants and smelters.

Other abandoned-mine and post-mining challenges

The individual characteristics of the inherited liabilities presented in Figure 2 are compiled in Table 1 (5). In total the BLM register contains nearly 98,000 individual attributes.

Abandoned-mine and post-mining tasks from the perspective of the mining companies and authorities

One obvious outcome of the 2020 Annual Conference of the Society for Mining, Metallurgy and Exploration (SME) was that the mining companies were ready to recognise the significance of the Social License to Operate as part of the entire mining life cycle (11). It was clear from many of the papers presented at the Conference, which was held in Phoenix, Arizona, and from the accompanying trade exhibition, that the mining industry was now taking very seriously its responsibility for the orderly restoration and reclamation of the various sites it had been using for mineral extraction.

The visit to the Conference was followed by a research trip through southern USA and the Federal States of Arizona, New Mexico, Texas and Louisiana. The total area of land covered by these four States is more than four times larger than that of Germany, while their combined population is only about half of that of the latter. The population density in the four named States is therefore some eight times less than that of Germany, amounting to around 30 inhabitants per km². These figures serve to reinforce the personal impression of the region. The availability of land with a low utilisation factor shapes the manner in which the open spaces are used. On the edge of the former mining town of Bisbee in the south of Arizona, e. g., there stands an abandoned open-pit copper mine where problems with mine water, earth slips and dust are clearly evident (Figure 4a), while close to Silver City in New Mexico it is possible to see active copper mining areas that also show signs of a successful and ongoing recultivation process (Figure 4b). However the dry climate in this area effectively prevents much vegetation growth.

This paper has already highlighted the confusing administrative structure and the complicated legal situation as far as mining operations are concerned. This has also meant that individual States may adopt a distinctly different approach to the problem of abandoned mines and post-mining recovery and may even act on quite dissimilar statistical information.The Arizona State Mine Inspector, as part of his remit working for the Federal State of Arizona, e. g., has specified a figure of some 100,000 abandoned mines. The BLM, for its part, has recorded more than 200,000 individual entries for disused mines in Arizona, of which only around 20,000 are located on public land (2, 5).

Austin, Texas, is home to the Railroad Commission of Texas (RRC), which is the competent authority for abandoned-mine and post-mining issues in this U.S. State. The RRC, which has around 30 employees, is also responsible for the exploration and production phase and for all post-mining matters arising throughout Texas. The main post-mining problems concern mine water, surface water and final closure plans. Given the significant resource potential of the State of Texas it is no surprise that the main focus of activity of the RRC is on oil and gas extraction and on pipeline operations (12).

In this context it is interesting to note the two massive sinkholes that developed close to the town of Wink in western Texas. The oil that is extracted in this area is graded as West Texas Intermediate (WTI), while the region also produces gas by means of the fracking process. The two sinkholes are up to 200 m in diameter and as much as 30 m deep. Their formation is related to the subrosion of salt formations due to water inflow via natural or anthropogenic rock fractures or well bores (13). The ground movements have also been investigated by radar interferometry.

The Department of Natural Resources in Baton Rouge, which is the capital of the U.S. State of Louisiana, is also responsible for the challenges arising during the post-mining phase. As in other U.S. States, Louisiana operates an so-called Abandoned Mine Land Program, in which information on abandoned mining sites is collected, evaluated and used to minimise hazards and for revitalisation. The Programme has registered more than 1,100 non-hard coal mines, around one half of which pose a potential risk to man and the environment (14).

A quite special phenomenon exists in southern Louisiana, which is home to the wetlands of the Mississippi Delta. In this region brine is extracted from the existing salt domes, caverns are created and hydrocarbons are stored in them. The geology of the salt domes is a complex one. In 2012 a sinkhole appeared near the community of Bayou Corne whose final dimensions were estimated to be more than 10 hectares (15). The incident, which had a massive impact on the people living in this extremely flat wetland area, was preceded by ground movements and seepages of gas on the surface of the water. This event shows how important it is to have meaningful monitoring measures in place together with a profound understanding of the processes taking place below ground.

Summary and Outlook

The USA is home to tens of thousands of abandoned mine workings, the majority of which have to be recultivated and restored to post-mining use at the taxpayers’ expense. This is partly due to the fact that prior to 1977 there was no legal requirement for mine operators to undertake any restoration of the land and facilities that had been used for mining activities. According to the BLM registers there are more than 50,000 former and now abandoned mining sites on federal land alone, mainly in western USA, with nearly 100,000 individual attributes that in some cases present a risk to public safety and the environment and need to be stabilised and restored as a matter of priority. The restoration and recultivation measures are hampered by the fact that a multitude of regulatory competencies have to be taken into account and that public funds can only be released when no legal successor to the originator can be identified – a process that can often involve many years of searching. The complex legal situation also makes it difficult for non-governmental organisations (NGOs) and voluntary aid agencies to engage in the recultivation and renovation work, the end result being that the USA will probably have to live with the problem of inherited mining liabilities for many years to come.