The impacts of surface mining on stream quality result directly from the land disturbance activity. Unweathered earth materials brought to the surface during mining undergo rapid alterations due to exposure to air and water, thereby releasing many of their structural constituents into water.1 When disturbed rock and soil is exposed to precipitation (e.g., rainfall, snow, hail, dew, etc.), water running off these materials carries solid particles (also known as sediments) as well as dissolved constituents such as salts, metals, trace elements, and/or organic compounds that can pollute nearby surface waters. Water may also percolate into the disturbed materials causing movement and leaching of salts, metals, and trace elements into deeper levels causing potential groundwater quality impacts.2 The chemistry of the water is highly dependent on the overburden or earthy materials that were disturbed during the mining process.

Surface mining activities can result in disturbed lands with poor drainage unless this problem is controlled, minimized, and even eliminated by reclaiming the areas.2, 3 Reclamation of disturbed sites usually involves grading the areas to achieve a land surface that is stable and compatible with surrounding undisturbed areas, possibly replacing topsoil on the regraded surface and seeding with plants capable of controlling erosion and runoff, and to provide forage for both indigenous wildlife and/or domestic livestock.3 The Surface Mining Control and Reclamation Act (SMCRA) of 1977 specifies policies and practices for reclaiming areas after surface mining to minimize water quality impacts and to encourage the development of stable, diverse plant communities after mining.4

The Clean Water Act (CWA) of 1977 and previous water control legislation [Federal Water Pollution Control Act of 1972] require restoring and maintaining the chemical, physical, and biological integrity of our nation's water.5, 6 The intention of these laws was to establish a framework for permitting and regulating all point discharges into surface waters, with the laws particularly targeting the discharge of sewage and wastewater from communities into streams, rivers, and lakes. The CWA was designed to place limits or standards on water being discharged into the waters of the United States, but also to maintain drinking water and recreational uses of water, and to restore the quality of streams and lakes that had been degraded.7 The law has been interpreted as requiring all waters to be “fishable and swimmable.”8

Water discharged from surface mines is regulated by the CWA,5 and all mines are required to only discharge water that meets CWA effluent standards. Therefore, all water that comes from a permitted mine (whether the water was received as rainfall, snow, hail, etc. at the surface or from underground seepage) must pass through a sedimentation or treatment pond and meet or exceed discharge standards before it can be released into receiving surface waters.8

Nationwide, over 20,000 km of rivers and streams and over 75,000 ha of lakes and reservoirs are adversely affected by contaminated water draining from abandoned mines.4 The vast majority of these problem areas occur in the eastern United States where coal mine drainage is considered by the United States Environmental Protection Agency (U.S. EPA) to be the most significant non-point pollution problem. Although Wyoming is currently the leading coal producing state in the country (approximately, one-third of our nation's coal is mined in this state), Wyoming and other western United States are plagued with historic mining activities involving metal ores, such as copper (Cu), lead (Pb), zinc (Zn), and silver (Ag), with the trace elements molybdenum (Mo) and uranium (U) also mined in certain regions. In addition to surface water impacts from coal, metal, and trace element mining that can generate acid mine drainage (AMD) from oxidation of pyritic ores (e.g., iron sulfide FeS₂), other pollutants are also of concern including metals [aluminum (Al), antimony (Sb), cadmium (Cd), cobalt (Co), chromium (Cr), Cu, iron (Fe), manganese (Mn), nickel (Ni), Pb, and Zn], trace elements [arsenic (As), Mo, and selenium (Se)], radioactive elements [cesium (Cs), radium (Ra), thorium (Th), U, and vanadium (V)], and mining operation by-products [mercury (Hg) and cyanide (CN)].

Many areas in the United States and other parts of the world were disturbed prior to the enactment of any laws regulating their drainage quality and water release into streams.7 These disturbed areas may contribute significant amounts of pollutants to surface waters because they often are devoid of minimum vegetative cover and because their soil properties limit natural reclamation of the site.3 Pre-1977 mining activities were also considered in SMCRA legislation.4 Including provisions for reclaiming “abandoned” mined lands, which are surface-mining disturbances that occurred prior to enactment of the law and where no individual or company is held responsible for the damaged land. Drainage from these surface-mining operations has had and continues to have a dramatic effect on surface water quality because these “abandoned” pre-1977 sites discharge acid mine drainage into surface water bodies such as rivers, streams, creeks, and impoundments. Money generated by the “abandoned mine land reclamation fund” since 1977 goes to reclaiming abandoned areas, which aids in the improvement of water quality from abandoned mine sites (Table 1).

Table 1 Examples of surface water quality in different areas throughout the United States that have been impacted by mining activities

Location	Flow (L/min)	pH	Cond (dS/m)	Acid (mg/L as CaCO3)	Alkalinity (mg/L as CaCO3)	SO4 (mg/L)	Ca (mg/L)	Mg (mg/L)	Na (mg/L)	Al (mg/L)	Cu (mg/L)	Fe (mg/L)	Mn (mg/L)	Zn (mg/L)
Maryland	640	2.7	4950	3470	bd	3700	320	55	bd	198	na	640	10	na
Montana1	68	2.7	5970	5150	0	6000	240	110	13	325	500	450	na	5
Montana2	22	4.6	1900	815	170	1300	220	86	26	190	3	1	13	33
Nevada	15	2.2	5100	2795	bd	3670	502	382	95	152	na	595	80	18
Ohio	900	6.5	1790	134	88	985	168	35	bd	bd	na	89	2	na
Pennsylvania1	85	4.0	2340	208	bd	1070	224	70	bd	12	na	70	13	na
Pennsylvania2	38	4.8	3140	211	7	2040	325	57	323	1	na	121	2	na
West Virginia1	8	3.3	4230	920	bd	2525	232	228	bd	83	na	132	48	na
West Virginia2	136	3.6	946	516	bd	640	78	23	bd	41	na	7	20	na
Wyoming1	170	6.8	<100	bd	27	19	10	35	3	bd	5	bd	<1	<1
Wyoming2	680	8.3	1640	bd	282	836	145	64	158	23	bd	bd	<1	na