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Mineral Resource Land
Nevada led the nation in production of gold and silver throughout the 1990's. Mining is especially important to rural community economies in northern Nevada where most of the large gold and silver mines are located. Production in 1999 was 8.3 million troy ounces of gold and 19.5 million troy ounces of silver, worth approximately $2.5 billion. In 2000, gold and silver production increased to 8.5 million and 23.0 million troy ounces, respectively, but the dollar value was about the same as 1999 due to lower prices for both metals. The industry employs about 11,000 people in Nevada, and pays a higher average wage than any other employment sector. Recent declines in precious metals prices have forced many companies to cut costs with layoffs or increased production. Exploration expenditures in 1999 were approximately half of the 1994 expenditures.
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Reclamation of a waste pile at a modern-day mine on the Carlin trend in Eureka County. Regulations, university and industry research, and corporate stewardship have brought about improvements in reclamation planning and practices.
A total of 2,375 acres (441 on private and 1,934 on public land) were reclaimed at large mines between 1996 and 2000 (Table 4-7). State law requires that large mine operators return mine sites to a productive use, such as wildlife habitat or grazing land. 1992 photo courtesy of Newmont Mining Company and NBMG.
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Other minerals are mined in Nevada. The recent increase in energy prices has increased demand for barite, which is primarily used for drilling mud. Industrial minerals such as silica sand (for making bottles and jars), diatomite (cat litter and filters), limestone/lime, lithium compounds, gypsum, magnesite, perlite and salt, and specialty clay continue to be mined at relatively stable rates.
Enhancements in technologies and regulations have reduced the number and magnitude of negative environmental impacts from individual mines. State and federal agencies continue to work with industry and the interested public to ensure that mining operations from design through reclamation minimize and mitigate negative impacts and return disturbed land to a productive use. Mines are subject to extensive permitting and monitoring through their entire life cycle - during start-up, operations, reclamation, and closure.
The NDEP is the state permitting agency for all mining operations and exploration projects. For a mine or exploration project taking place on public land, a plan of operation approved by the responsible federal land management agency may be substituted for the permit application. Proposed exploration projects and mines located on public land are subject to an assessment of environmental impacts and implementation of an approved mitigation plan in accordance with the National Environmental Policy Act. The state Bureau of Mining Regulation and Reclamation within the NDEP regulates 151 active mining operations through water pollution control permits to make sure the quality of water resources is not degraded. In 2000 and 2001, six percent of the regulated mining facilities were found by the Bureau to be in substantial noncompliance with permit conditions (i.e., an order or notice of violation has been issued, and enforcement activities are ongoing).
Land disturbed by mining and mineral exploration projects must be reclaimed according to federal and state law (NRS 519A). Reclamation means shaping, stabilizing, revegetating or otherwise treating the land, during or after mining and exploration activity, to return the site to a safe, stable condition that establishes a productive post-mining land use. Properly done, reclamation reduces risk of water quality problems, recreates wildlife habitat, controls slope erosion, and returns soil conditions capable of supporting native vegetative cover. Some reclamation requirements are retroactive for disturbances created after January 1, 1981.
A mining company must post a bond to ensure that funds will be available for reclamation in the event that the operator defaults. The Nevada Division of Minerals administers a bond pool that guarantees up to one million dollars of reclamation activities for small companies that have been refused help by commercial sources. Currently 253 mining reclamation operations have the required financial bonding. Ninety-eight percent of the mining reclamation operations have obtained required bonding.
Since 1989, operators of "large" mines and exploration projects (i.e., projects exceeding 5 acres of disturbance or 36,500 tons removed annually) annually report the amount of land disturbed and reclaimed to the NDEP. A project area is "reclaimed," and the bond released only after NDEP or federal agency officials have verified that the work conforms to an approved reclamation plan and guidelines. Guidelines address topsoil replacement, slope stabilization, and sustained reestablishment of plant communities representative of the project site. Between 1996 and 2000, the cumulative amount of public and private land disturbed for large mining and exploration projects increased by about 14,230 acres (Figure 4-6). Approximately 2,370 acres were reclaimed (Nevada Division of Environmental Protection, 2002).
For the same period, mining companies reported a total of 18,880 additional acres were disturbed and 1,934 acres were reclaimed on public land (Table 4-7). On private land, 6,688 more acres were disturbed and 433 acres reclaimed. A majority of the additional land disturbed and reclaimed each year occurred on public land. The totals do not include incremental disturbance or reclamation occurring at mines or exploration projects that disturb 5 or less acres or that remove 36,500 tons or less each year. About 20 percent of the disturbance is reported as monitored reclamation, meaning earthwork and seeding has been completed, but the bond has not been released
Sometimes the nature of the ore deposit requires massive excavations called open pit mines. Open pit mines that extend below the groundwater table must be de-watered to keep from flooding the operating area. In many mines, the amount of water that must be pumped exceeds the mines' consumptive use needs. Excess water from open pit operations are used beneficially in a variety of ways. A majority of the excess water is discharged to surface water systems, re-injected into aquifers, or applied to crop land, or piped to power plants. After the mining and de-watering stops, the pits will eventually fill. Open pits may be exempt from reclamation, subject to NDEP approval.
Over the long term, there is uncertainty over the potential cumulative and regional impacts dewatering of open pit mines will have on surface and groundwater resources. Other water users in the region and the public have expressed a deep concern, prompting government agencies and the industry to study the potential long-term impacts of de-watering on the hydrology of the region and water quality of the pit lakes. Most large open pit mining operations with dewatering discharges are located in the Humboldt River Basin. Mining water withdrawals initially were anticipated to remain relatively constant at about 275,000 acre-feet per year with a slight increase up to the year 2010. However, changes in mining operations are difficult to predict. More recent indications are that pumpage will decline at some major mines.
The trend of pit dewatering activities generating water volumes in excess of mine processing and consumptive needs is expected to continue. Actual mine dewatering may change if operators shift from open pit mining to underground mining, or if economics change. However, some degree of mine dewatering is expected to continue regardless of the type of production activity. Precious metal production from underground mines is slowly increasing. In 1999, about 24 percent of Nevada's gold production came from underground mines. In general, underground mines are easier to permit than surface mines because less land is disturbed.
Mining Operations and Wildlife
The mining industry and the NDOW have coordinated efforts to reduce direct mortality of wildlife at mine sites, particularly losses resulting from cyanide or other types of chemical poisoning. Since 1990, the NDOW and mine operators have worked together to implement a regulatory program to prevent wildlife mortality at heap leach ponds and mine tailings. Efforts to study and reduce wildlife mortality began in 1984, when use of the heap leach mine technology surged in Nevada.
As a result of the joint efforts and the Industrial Artificial Pond permit program, overall wildlife mortalities at mine sites decreased from over 2,000 individuals in 1986 to just over 300 in 1997 (Figure 4-7). Less than 50 percent of the 1997 mortalities were the result of contact with permitted cyanide ponds or protective measures. These measures include fencing, pond covers (e.g., netting), HDPE floating "bird-balls", floating pond covers, dilution, and chemical neutralization.
Figure 4-7 summarizes the overall decrease in mining related mortalities in Nevada since 1984. The average number of mortalities per mine decreased from over 100 individuals per mine to less than 10 individuals. A low of 3 individuals per mine occurred in both 1993 and 1997. During the 1990's, the number of permitted facilities at mines hovered around 100. About half of the increased number of mortalities from 1994 through 1996 was attributed to rodent (primarily mice) mortalities.
Waterfowl, shorebirds and big game animal deaths continued to decline during these years. The decrease in the total number of mortalities, from 1,645 in 1990 to 377 in 1997, includes a four-fold decrease in the numbers of bird mortalities during that period. Waterfowl mortalities reached an all time low of 16 individuals in 1995. Data on the distribution of mortalities by major animal groups in 1997 is presented in Figure 4-8. The program goal of zero mortality appears to be attainable. Twenty-nine active mines accomplished this goal in 1997. An additional 33 permit holders reported 5 or less wildlife mortalities over the entire year (Nevada Division of Wildlife, 1998).
Abandoned Mine Land Safety
The estimated number of potentially hazardous abandoned mine openings in Nevada is at least 50,000 (Nevada Division of Minerals, 2000). NDOM has identified 8,118. About 6,000 have been secured by NDOM, claimants, owners, or volunteers. Fencing is the most common security measure. About 1,000 have been backfilled. A priority is backfilling dangerous mines located near urban areas. The NDOM and the BLM have agreements in place to streamline the securing process. The number of new sites secured each year is expected to remain in the range of 300 to 400. Backfilling requires that properly trained scientists do biological and cultural surveys.
Backfilling may not be suitable in some instances. Mines can represent essential habitat for sensitive wildlife, especially bats. Today, the Nevada Bat Working Group is providing biological input to closure plans for the remaining mine openings. Three of Nevada's most significant bat roosts on record occupy historical mine workings. These unique resources include: the largest known big-eared bat (Corynorhinus townsendii) hibernation roost in Nevada (White Pine County); the largest known small-footed Myotis bat (Myotis ciliolabrum) hibernation roost in Nevada (Eureka County), and 3) Nevada's largest known pallid bat (Antrozous pallidus) maternity roost (Pershing County). There is considerable concern about bat roosts in mines that are, as yet, undiscovered (Bradley, 2002). Though some private and public entities continue to use total closure techniques, effective alternative mine closure methods have been designed, such as wildlife-friendly gates, to meet both safety and biological objectives.
Abandoned Mines and Water Quality
Today, mining operations are subject to water pollution control permits that ensure the mine site in the production, closure, and post-closure periods will not degrade water quality. Water quality impacts may arise if the natural metallic  compounds exposed in the mine wall or removed and stockpiled rock changes chemically and leaches into groundwater or drains to a stream. Drainage of chemical solutions from ore wastes, such as cyanide solutions, may also become a water quality concern. Inadequate precautions were taken in the past, so some abandoned mines now pose minor to significant environmental risks. Such abandoned mine sites are scattered throughout the state. In the worst cases, drinking water supplies may become unusable, or fish and aquatic insects and plants may be unable to survive.
In 1999 the Interagency Abandoned Mine Land Environmental Task Force, composed of state and federal agencies, completed a statewide study to identify abandoned mine sites that pose significant environmental threats. The Nevada Abandoned Mine Lands Report identifies and prioritizes sites based on their potential to degrade water quality and jeopardize public health and aquatic ecosystems. As a result of the extensive mining history in Nevada, at least a couple thousand abandoned mine sites exist with the potential to impact ground or surface water. Because of the enormity of the effort that would be required to evaluate so many sites, the Task Force used institutional knowledge, available data and best professional judgment to identify 33 sites that may impact ground or surface water. Six of the sites have been prioritized for reclamation. Insufficient funding is anticipated to be an obstacle to achieving remediation objectives (Nevada Interagency Abandoned Mine Land Environmental Task Force, 1999).
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