Overview of Mine Drainage Geochemistry 

at Historical Mines, Humboldt River Basin 

and Adjacent Mining Areas, Nevada 

By J. Thomas Nash 

Chapter E of 

Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada 

Edited by Lisa L. Stillings 

U.S. Geological Survey Bulletin 2210-E

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary 

U.S. Geological Survey

Charles G. Groat, Director 

Posted online December 2003, version 1.0 

This publication is only available online at: 

http://geology.cr.usgs.gov/pub/bulletins/b2210-e/ 

Any use of trade, product, or fi rm names in this publication 

is for descriptive purposes only and does not 

imply endorsement by the U.S. Government 
Preface 

Northern Nevada is one of the world’s foremost regions of gold production. The 

Humboldt River Basin (HRB) covers 43,500 km2 in northern Nevada (Crompton, 1995), 

and it is home to approximately 18 active gold and silver mines (Driesner and Coyner, 

2001) among at least 55 significant metallic mineral deposits (Long and others, 1998). 

Many of the gold mines are along the Carlin trend in the east-central portion of the HRB, 

and together they have produced 50 million ounces of gold from 1962 (when the Carlin 

mine first opened) through April 2002 (Nevada Mining Association, 2002). Mining is 

not new to the region, however. Beginning in 1849, mining has taken place in numerous 

districts that cover 39 percent of the land area in the HRB (Tingley, 1998). In addition to 

gold and silver, As, Ba, Cu, Fe, Hg, Li, Mn, Mo, Pb, S, Sb, V, W, Zn, and industrial commodities such as barite, limestone, fluorite, sand and gravel, gypsum, gemstones, pumice, 

zeolites, and building stone, have been extracted from the HRB (McFaul and others, 

2000). 

Due to the large amount of historical and recent mining in the HRB, the Bureau of 

Land Management (BLM) in Nevada asked the U.S. Geological Survey (USGS) Mineral 

Resources Program to conduct a series of mineral-deposit-related environmental studies in the HRB. BLM required data and geoenvironmental interpretations regarding (1) 

the chemical composition of water, soil, sediment, and mine waste in the HRB, (2) the 

natural background chemistry of these materials, and (3) how mining activities may have 

altered their chemistry. The paper that follows describes one of the studies conducted by 

the USGS Minerals Program to answer these and similar questions. 

All papers within this series of investigations can be found as lettered chapters of 

USGS Bulletin 2210, Geoenvironmental Investigations of the Humboldt River Basin, 

Northern Nevada. Each chapter is available separately online. 

References Cited 

Crompton, E.J., 1995, Potential hydrologic effects of mining in the Humboldt River Basin, northern 

Nevada: U.S. Geological Survey Water Resources Investigations Report 94-4233, 2 sheets. 

Driesner, D., and Coyner, A., 2001, Major mines of Nevada 2000: Mineral industries in Nevada’s 

economy: Nevada Bureau of Mines and Geology Special Publication P-12, 28 p. 

Long, K.R., DeYoung, J.H., Jr., and Ludington, S.D., 1998, Significant deposits of gold, silver, copper, 

lead, and zinc in the United States: U.S. Geological Survey Open-File Report 98-206A, 33 p. [USGS 

Open-File Report 98-206B contains one 3.5-inch diskette]. 

McFaul, E.J., Mason G.T., Jr., Ferguson, W.B., and Lipin, B.R., 2000, U.S. Geological Survey mineral 

databases—MRDS and MAS/MILS: U.S. Geological Survey Digital Data Series DDS-52, two CDROMs. 

Nevada Mining Association, 2002, Industry to celebrate 50 millionth ounce of gold: Nevada Mining 

Association News Release, April 11, 2002. 

Tingley, J.V., 1998, Mining districts of Nevada (2nd ed.): Nevada Bureau of Mines and Geology 

Report 47d, one CD-ROM. 
Contents 

Preface ..........................................................................................................................................................III


Abstract .......................................................................................................................................................... 1


Introduction ................................................................................................................................................... 1


Climate and Geography in Mine Drainage ............................................................................................... 3


Mine Drainage Compositions ..................................................................................................................... 4


Abundance............................................................................................................................................ 4


Acidity ................................................................................................................................................... 4


Metal Concentrations ........................................................................................................................ 5


Relation to Ore Type .......................................................................................................................... 10


Evolution of Surface Waters Within Mining Areas ............................................................................... 10


National Mine Area ........................................................................................................................... 11


Hilltop Mine Area ............................................................................................................................... 11


Dean Mine Area ................................................................................................................................. 12


Galena Canyon Area ......................................................................................................................... 16


Coon Creek—An Unusual Example ................................................................................................ 18


Attenuation Mechanisms ................................................................................................................. 19


Quality of Streams Leaving Mining Areas .............................................................................................. 22


Nevada Class-A Waters in Mining Areas...................................................................................... 23


Metal Loads and Total Maximum Daily Loads .............................................................................. 24


Discussion and Conclusions ..................................................................................................................... 25


References Cited ........................................................................................................................................ 27


Figures 

1. 	 Location and character of surface water samples collected in 


northern Nevada........................................................................................................................... 2


2. 	 Relations of metal concentrations to pH in surface waters.................................................. 7


3. 	 Relations of metal concentrations in mine drainage to deposit type ................................ 12


4. 	 Evolution of mine drainage in the National mine area ......................................................... 14


5. 	 Evolution of mine drainage in the Hilltop mining area.......................................................... 15


6. 	 Evolution of mine drainage in the Dean mining area............................................................ 17


7. 	 Evolution of mine drainage in the Galena mining area ........................................................ 19


8. 	 Evolution of mine drainage in Coon Creek west of Rip Van Winkle mine ......................... 21


9. 	 Evolution of mixed mine-related waters as a function of pH, iron, 


and unreactive elements........................................................................................................... 22


10. 	 Major sources of contamination and possibly contaminated streams 


in northern Nevada..................................................................................................................... 24

V 

Photographs 

1. 	 The Buckskin National mine tunnel releases a moderate flow of water 


during spring snow melt .............................................................................................................. 3


2. 	 The Majuba mine adit releases a small amount of water with a pH of 7.4 


and low metal concentrations.................................................................................................... 4

3. 	 Rochester Creek has eroded a deep cut into the large tailing impoundment.................... 5


4. 	 Tailings from the 1930s milling of copper ore at the site of the future 


Big Mike mine collects water during rainy periods................................................................ 5


5. 	 A bulldozer cut at a mercury mine in the Antelope Springs district collects 


water with a very high Hg concentration ................................................................................. 6


6. 	 Drainage from this mine tunnel reacts with sulfidic waste to create even 


more acidic water and extremely high metal concentrations .............................................. 6


7. 	 Very acidic water collects in this cut into sulfidic mill tailings at the 


Caselton mill tailings impoundment......................................................................................... 11


8. 	 The National mine and associated mine dumps at an elevation of 1,800–


2,100 m receive substantial snow and rain, causing more mine drainage 


than in most areas in northern Nevada .................................................................................. 13


9. 	 The collapsed mine tunnel at the National mine releases acidic 


mine drainage, but the flow is only about 10–20 gallons/minute....................................... 13


10. 	 Acidic mine drainage from the National mine flows over mine waste 


and tailings, thereby accumulating even more acid and metals........................................ 14


11. 	 Mill tailings from the Hilltop mill, placed in the channel of an ephemeral 


stream, react with seasonal surface waters, adding acid and metals ............................. 15


12. 	 A series of mine tunnels in the Dean mine complex released acidic 


drainage that reacted with sulfidic waste rocks .................................................................. 16


13. 	 The creek flowing north from the Dean mine workings and dumps was 


acidic and choked with iron flocculate in 1997, but the reclamation in 


1998 produced a marked improvement in water quality ...................................................... 17


14. 	 The ocher materials shown here formed when acidic mine drainage 


in Iron Canyon evolved to higher pH, causing iron minerals (possibly 


schwertmanite) to precipitate .................................................................................................. 18


15. 	 The sulfidic mine dump in Butte Canyon is fairly typical of mine waste 


from a polymetallic vein deposit .............................................................................................. 18


16. 	 View of Rip Van Winkle mine area with tailings six ponds in Coon Creek ........................ 20


17. 	 Acidic seepage from the Rip Van Winkle tailings create thin films of 


red iron minerals on mixing with Coon Creek ........................................................................ 20


18. 	 Sulfidic mine waste at the Black Beauty mine, Independence district, 


releases acid and metals to seeps that flow into Gance Creek ......................................... 25

VI 

Tables 

1. Summary of surface-water compositions, northern Nevada ............................................... 8


2. Composition of streams leaving six mining areas in northern Nevada ............................. 23


3. Examples of metal loads from mining areas compared to Humboldt River ...................... 26

Overview of Mine Drainage Geochemistry 

at Historical Mines, Humboldt River Basin 

and Adjacent Mining Areas, Nevada 

By J. Thomas Nash 

Abstract 

Reconnaissance hydrogeochemical studies of the Humboldt River basin and adjacent areas of northern Nevada have 

identified local sources of acidic waters generated by historical mine workings and mine waste. The mine-related acidic 

waters are rare and generally flow less than a kilometer before 

being neutralized by natural processes. Where waters have a 

pH of less than about 3, particularly in the presence of sulfi de 

minerals, the waters take on high to extremely high concentrations of many potentially toxic metals. The processes that 

create these acidic, metal-rich waters in Nevada are the same 

as for other parts of the world, but the scale of transport and 

the fate of metals are much more localized because of the 

ubiquitous presence of caliche soils. 

Acid mine drainage is rare in historical mining districts 

of northern Nevada, and the volume of drainage rarely exceeds 

about 20 gpm. My findings are in close agreement with those 

of Price and others (1995) who estimated that less than 0.05 

percent of inactive and abandoned mines in Nevada are likely 

to be a concern for acid mine drainage. Most historical mining 

districts have no draining mines. Only in two districts (Hilltop 

and National) does water affected by mining fl ow into streams 

of significant size and length (more than 8 km). Water quality 

in even the worst cases is naturally attenuated to meet waterquality standards within about 1 km of the source. 

Only a few historical mines release acidic water with 

elevated metal concentrations to small streams that reach the 

Humboldt River, and these contaminants and are not detectable in the Humboldt. These reconnaissance studies offer 

encouraging evidence that abandoned mines in Nevada create 

only minimal and local water-quality problems. Natural 

attenuation processes are sufficient to compensate for these 

relatively small sources of contamination. These results may 

provide useful analogs for future mining in the Humboldt 

River basin, but attention must be given to matters of scale: 

larger volumes of waste and larger volumes of water could 

easily overwhelm the delicate balance of natural attenuation 

described here. 

Introduction 

The composition of water discharged from a mine, commonly called “mine drainage,” is largely determined by the 

ore type, host-rock lithology, and geography of the mine 

(Plumlee, 1999). Historically mined ores in northern Nevada 

are generally similar to those mined elsewhere in the Western 

United States, but local geographic factors cause mine drainage in northern Nevada to differ in important ways. Unlike 

most mining areas of the Rocky Mountains, historical mines 

in Nevada are much less likely to discharge acid waters into 

nearby streams. Acidic mine drainage in Nevada is a rare and 

local phenomenon and in northern Nevada does not reach the 

major streams. Historical mines in northern Nevada have the 

potential to create acidic, metal-rich waters, but this rarely 

happens because of the low precipitation and caliche soils 

characteristic of arid climate. 

This overview is based on hydrogeochemical studies of 

more than 40 historical mining areas in northern Nevada (fi g. 

1) that have been carried out as part of the U.S. Geological 

Survey’s investigations of the mineral resources and environmental geochemistry of the Humboldt River basin. The 

Humboldt River basin study was prompted by public concerns 

and land management issues regarding current and future 

mining in the watershed (NDWP, 2001). This investigation 

builds upon studies of Price and others (1995), who described 

and evaluated mine drainage in Nevada. Studies by the author 

from 1995 to 2000 have focused on historical mining districts 

(Nash, 2001) and collection of new hydrogeochemical data for 

the region (Nash, 2000). Many of the more complex sites were 

visited more than once to obtain more information on seasonal 

variability. No active mines were studied, and most of the 

mining areas studied have been inactive (“abandoned”) for 40 

or more years. 

In this chapter, several terms will be used collectively 

to combine similar themes. I will use the term “metal” to 

describe cations or base metals, and I also include metalloid 

elements such as Se and As that form oxyanions in water 

(selenate, arsenate). I use the term “mine waters” and “mine 

1 
2 Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada 

Lander 

Eureka 

Churchill 

Humboldt 

Basin 

+

+

+

+

+

+ +

+

Midas

National 

Potosi 

Ivanhoe 

Scraper 

Springs 

Burner 

Merrimac 

Railroad 

Cortez 

Eureka 

Austin 

Hilltop 

Lewis 

Buffalo 

Black 

Diablo 

Golconda 

Adelaide 

Bottle 

Creek 

Imlay 

Star 

Willard Rochester

Mineral 

Basin 

Safford 

Beowawe Majuba 

117° 

41° 

Modarelli 

Humboldt 

Pershing 

I-80 

I-80 

Elko 

White Pine 

North Battle Mtn 

Mountain City 

River 

Battle Mountain

Winnemucca

Eureka

Elko

Austin

Gold Circle 

Tuscarora 

Independence Mts 

Swales Mtn 

Tenabo 

Mount Hope 

Valley Battle Mtn 

Iron Point 

Awakening 

Tenmile 

Buena Vista 

Antelope Springs 

Trinity 

Seven Troughs 

Birch Creek 

Lovelock

White Pine 

Mill City 

US 95 

US 93 

N 271 

US 50 

Explanation 

0 pH values Scale in Miles 50 

+ 1.8-3.4 

X 3.5-6.4 

6.5-7.4 

7.5-9.2 

Figure 1. Location and character of surface water samples collected in northern Nevada. The limits of the Humboldt River 

basin are shown by the green dashed line. Mining districts (tan) are from Tingley (1998). 

drainage” interchangeably for waters flowing from mine adits 

or in contact with mine wastes. Broadly, without qualifi ers, 

the term mine drainage includes waters that have reacted with 

mine workings, mine waste dumps, or mill tailings. Drainage 

and other aspects of mill tailings are discussed in more detail 

elsewhere (Nash, 2003). The term “waters affected by mining” 

will be used for waters that are partly from mines, dumps, or 

tailings, but also partly from sources that have no mines or 

prospects; these stream waters are mixtures of surface, spring, 

and mine waters. Mining clearly can affect subsurface waters, 

but ground water is outside of the scope of this study because 

few wells are available for sampling. 

Methods for sampling and analysis are described elsewhere (Nash, 2000; Nash, 2001). Water samples were collected after testing for pH and conductivity with portable 

instruments. The methods are simplified from those described 

by Ficklin and Mosier (1999). The pH meter was calibrated 

several times a day using buffered solutions of pH 4.0, 7.0, 

and 10.0; calibration was checked after sample readings using 

reference solutions. Water samples for chemical analysis were 

collected by a consistent technique adopted for reconnaissance 

investigations. The water was collected with a disposable 

60-mL syringe, then pushed through a disposable 0.45-μm 

cellulose filter. The syringe and the 60- or 120-mL polyeth­
Overview of Mine Drainage Geochemistry, Humboldt River Basin and Adjacent Mining Areas, Nevada 3 

ylene bottle were rinsed twice in the sampled water prior to 

collection. Samples for cation analysis was acidified to a pH 

of about 2 at the site with 5 drops of ultrapure 1:1 HNO3 per 

60 mL. Samples for anion analysis were filtered but not acidified. Analyses of cations were by ICP-MS at a commercial lab 

for samples collected in 1996 and 1997, and by the USGS for 

samples collected in 1998 and 1999. Analytical methods and 

quality assurance are described elsewhere (Nash, 2000). 

Climate and Geography 

in Mine Drainage 

Climate and topography are important factors in the 

development of mine drainage. Three aspects need to be 

briefly highlighted. First, mine drainage can only happen 

where there is enough vertical relief to cause water to fl ow 

from mine workings. Precipitation that interacts with mined 

materials on flat terrain may enter ground water, but it would 

not be called mine drainage as defined here. In Nevada, mine 

drainage is found only in the hilly or mountainous parts of 

the region where precipitation can enter disturbed lands either 

directly or through fractures (ground-water flow) and then fl ow 

out on the surface. Mine shafts do not create surface drainage, 

but mine tunnels driven into mountains may collect ground 

water and carry it to the surface. Indeed, many mine tunnels 

were constructed originally to provide an energy-effi cient 

means of removing water from an underground mine, and after 

the mining ceases these tunnels continue to carry water (photograph 1). Water pumped from mines is geochemically similar to mine drainage, but will not be considered here. 

Second, precipitation is highly variable across distances 

as short as 1–2 km in Nevada, and these differences can be 

seen in the amount of water at a mined site. Generalized 

maps of precipitation in Nevada show the effects of elevation 

on increased amounts of precipitation, much of that as snow 

(Houghton and others, 1975). There should be no surprise 

that there is little or no mine drainage at lower elevations on 

the flanks of ranges. Orientation also is important because it 

influences the amount of exposure and evaporation. Large differences in precipitation and evaporation can be seen during 

and shortly after a spring storm. Just as aspen and fir trees tend 

to develop selectively in north-facing basins, more water is 

present in mine sites with a northerly aspect. This is evident in 

the higher amount of water in small creeks and in mine drainage of north-facing areas of the Battle Mountain, Hilltop, and 

National mining districts. 

A third feature related to climate is the development of 

alkaline waters and carbonate-rich aridsols and caliche in arid 

areas, including Nevada (Southard, 2000). The relationship of 

these soils to climate was first emphasized by Jenny (1941). 

Carbonate as caliche is a major constituent in alluvium and 

soils at lower elevations of the study area. The fi ne-grained 

and porous aspects of caliche makes the carbonate more reactive and available to ephemeral near-surface waters than calcium carbonate in limestone. Two aspects of the caliche may 

Photograph 1. The Buckskin National mine tunnel releases a moderate flow of water during spring 

snow melt. Reclamation in about 1997 created the cement trough and underground drain to minimize reactions with the mine waste dump. The pH is 3.0. 
4 Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada 

be important in mining areas. One, the surface waters have 

high alkalinity and pH values greater than 8; these waters have 

high acid-neutralizing capacity. Second, acid mine water that 

is released during wet periods of the year are is effectively 

neutralized by reactions with caliche as the waters infi ltrate 

this alluvium. 

Mine Drainage Compositions 

Abundance 

Only a small number of historical mines release mine 

drainage in amounts sufficient to be sampled. Using information from U.S. Geological Survey 1:24,000-scale topographic 

maps, such as locations of mine adits, topography, and locations of springs and streams, it was possible to anticipate 

likely sites of mine discharge. While in the field, I searched for 

signs of mine drainage, which generally can be detected from 

a distance of 100–200 m as tell-tale streaks of red iron coatings. I was able to identify only 16 mine adits with active discharge of water (sufficient to measure pH and collect a sample 

for analysis) (photograph 2). This is a very small numbered 

when compared to the thousands of mines and prospects in 

the districts that I traversed. Mill tailings interact with surface 

water (seasonal streams and ponds) at 12 sites (photograph 3; 

photograph 4). Small ponds and large puddles (> 5 m wide) 

form occasionally at nine sites (photograph 5). Mine waste 

dumps are wet from streams or mine waters at 10 sites (photograph 6). Although my reconnaissance study probably missed 

some mines that release drainage waters, I believe I found a 

representative selection of draining adits and possibly found 

most of the draining adits in the districts under study. Considering the large area studied, about 25 million acres, and the 

very large number of historical mines and prospects shown 

on the topographic maps (possibly 75,000; cf. 225,000 to 

310,000 in all of Nevada; Price and others, 1995), the number 

of wet, draining adits and mine dumps is small. From my 

observations, I estimate that less than about 0.05 –0.1 percent 

of historical mines and prospects release contaminated drainage during the wettest months of the year. This is similar to 

the estimate of Price and others (1995). The largest discharge 

was about 50 to 100 gpm during spring runoff, and most of the 

mine discharges are 5 to 10 gpm in wet seasons. The largest 

number of draining adits and associated wet dumps was in the 

Dean mine complex, western Hilltop district, and these were 

effectively reclaimed in 1998. 

Acidity 

The pH of mine discharge waters ranges from 2.1 to 

8.3 with a median value of 3.4. Some atypical mine-water 

samples, such as puddles and small ponds, have pH values as 

low as 1.7. The range of pH values and the associated metal 

concentrations are shown in figure 2. The number of highly 

acidic water samples exceeds the number of sites because 

most of those extreme waters were sampled more than once 

Photograph 2. The Majuba mine adit releases a small amount of water with a pH of 7.4 and low 

metal concentrations. It is not a problem. 
Overview of Mine Drainage Geochemistry, Humboldt River Basin and Adjacent Mining Areas, Nevada 5 

Photograph 3. Rochester Creek has eroded a deep cut into the large mill tailings impoundment. 

The creek with a pH of 8.3 picks up a relatively small amount of contamination from the tailings. 

Photograph 4. Tailings from the 1930s milling of copper ore at the site of the future Big Mike mine 

collects water during rainy periods. The water attains a pH of 3.6 and accumulates very high metal 

concentrations, in part from evaporative concentration. 

Metal Concentrations during 4 years of study. The acidic mine waters carry high to 

extremely high concentrations of metals. All but a few of these 

acid sources appear to be seasonal, according to my observa- Metal solubility and transport by mine waters is largely a 

tions of zero or low flow in September visits and comments function of pH and pE (oxidation potential). Numerous reports 

from BLM staff. describe sources of acid and the solubility relations of metals 
6 Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada 

Photograph 5. A bulldozer cut at a mercury mine in the Antelope Springs district collects water 

with a very high Hg concentration. 

Photograph 6. Drainage from this mine tunnel reacts with sulfidic waste to create even more acidic 

(pH 2.6) water and extremely high metal concentrations. The adit was plugged and the dump was 

reclaimed in 1998. 

as a function of pH (Drever, 1997; Nordstrom and Alpers, often highly to extremely concentrated (relative to water-qual1999). The compositions observed in the Humboldt River ity standards for drinking water or aquatic life; NDEP, 2002). 

basin are similar to those of most hard-rock metal-mining As in most metal-mining areas, waters released from adits, 

areas, including well-studied mining areas of Colorado (Plum- dumps, or mill tailings tend to carry high metal concentrations 

lee and others, 1999; Nash, 2002; Mast and others, 2000). At at the source, roughly in proportion to acidity (fig. 2). These 

pH values below about 4, many potentially toxic metals are compositions evolve to more neutral pH values and lower 
metal concentrations as mine waters are diluted and neutralized by natural processes in streams.

The composition of mine waters and waters affected 

by mining is summarized in table 1, which also summarizes 

waters from areas with no mining or altered unmined rocks 

(background). The mine drainage sampling describes 42 sites 

(mine adits, tailings seeps, pit lakes, or ponds); another 20 

samples characterize unusual temporary features such as puddles on mine dumps and are in a separate part of table 1. The 

median value is perhaps the best guide to typical concerns, 

whereas the maximum value shows how concentrated and 

potentially toxic these waters can be at the source. The graphs 

in fi gure 2 show that metal concentrations are highest below 

a pH of about 4. Some mine waters (adits and pits have pH 

values of 4 to 9—alkaline waters contain lower metal concentrations than acidic waters. At higher pH values, metals tend 

to hydrolyze, with a resulting decrease in concentration. Reactions with atmospheric oxygen tend to cause Fe to precipitate 

as fi ne-grained iron-oxyhydroxides (FeOx) that are capable of 

adsorbing many metals, including As, Cu, and Pb. Near-neutral-pH waters tend to carry relatively low amounts of most 

metals, but some potentially toxic metals (Zn and Cd) can be 

Figure 2. Relations of metal concentrations to pH in surface waters.

Explanation: mine waters, sampled at adit or mine dump; mixed waters, sampled in stream below mines; background water from areas having no mines

0

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

1 2 3 4 5 6 7 8 9 10

pH

ALUMINUM in PPB

0

1

10

100

1,000

10,000

100,000

1,000,000

1 2 3 4 5 6 7 8 9 10

pH

ARSENIC in PPB

0

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

1 2 3 4 5 6 7 8 9 10

pH

COPPER in PPB

BACKGROUND MIXED MINE

0.0

0.1

1.0

10.0

100.0

1000.0

1 2 3 4 5 6 7 8 9 10

pH

LEAD in PPB

0.1

1.0

10.0

100.0

1000.0

1 2 3 4 5 6 7 8 9 10

pH

SELENIUM in PPB

0

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

1 2 3 4 5 6 7 8 9 10

pH

ZINC in PPB

BACKGROUND MIXED MINE

Overview of Mine Drainage Geochemistry, Humboldt River Basin and Adjacent Mining Areas, Nevada 7
Table 1. Summary of surface-water compositions, northern Nevada. [Table shows more significant figures than are reliable in some entries. Analytical values by ICP-MS. N, number of samples. WQS (wqs), approximate water quality standard; t(with *) is recalculated as a multiple of the water quality standard] 

pH Cond Al Al* As As* Cd Cd* 

PS/cm) (ppb) (u wqs) (ppb) (u wqs) (ppb) (u wqs) 

All surface-water samples (N = 280) 

Minimum 1.7 80 0.3 0.00 0.3 0.01 0.0 0.00 Median 7.6 480 22.2 0.22 9.6 0.19 0.5 0.09 

Maximum 10 4,590 1,800,000 18,000 3,800,000 76,000 26,000 5,200 3,9

Background samples (N = 52) 

Minimum 7.0 105 0.3 0.00 0.9 0.02 0.0 0.00 Median 8.2 320 1.9 0.02 3.8 0.08 0.1 0.02 

Maximum 9.0 >2,000 44.0 0.4 18.0 0.4 2.0 0.4 

Altered rocks/baseline (N = 55) 

Minimum 2.8 80 0.3 0.00 0.3 0.01 0.0 0.00 Median 8.1 480 10.5 0.10 5.5 0.11 0.1 0.02 

Maximum 8.8 >2,000 11000 110 284 6 18 4 

Mixed mine effects (N = 48) 

Minimum 3.1 160 0.3 0.00 0.3 0.01 0.0 0.00 Median 7.6 550 31.2 0.31 8.1 0.16 0.7 0.15 Maximum 8.6 >2,000 59,000 590 299 6 728 146 

Mine dump effects (N = 43) 

Minimum 1.7 228 0.3 0.00 0.4 0.01 0.0 0.00 Median 7.2 583 36.4 0.36 10.3 0.21 3.4 0.67 

Maximum 8.8 >2,000 1,630,000 16,270 120,000 2,400 14,900 2,981 4

Mine drainage (N = 42) 

Minimum 2.1 240 1.4 0.01 0.5 0.01 0.1 0.01 Median 3.4 1,095 12,000 120.0 187.3 3.75 10.9 2.19 

Maximum 8.3 4,590 352,000 3,520 30,800 615 5,110 1,020 

Mine pits and ponds (N = 21) 

Minimum 1.9 80 4.0 0.04 3.1 0.06 0.0 0.00 Median 7.1 530 593.0 5.93 42.0 0.84 3.2 0.63 Maximum 9.7 >2,000 680,000 6,800 122,000 2,440 12,000 2,400 1,3

Miscellaneous other waters (N = 20) 

Minimum 1.8 290 10.0 0.10 6.1 0.12 0.0 0.01 Median 3.0 1,330 14,500 145.0 420.0 8.40 35.8 7.16 Maximum 9.2 2,500 1,800,000 18,000 3,800,000 76,000 26,000 5,200 3,9WQS (ppb) 100 50 5 
Table 1. Summary of surface-water compositions, northern Nevada—Continued. 

Fe Fe* Mn Mn* Pb Pb* Se Se* 

(ppb) (u wqs) (ppb) (u wqs) (ppb) (u wqs) (ppb) (u wqs) 

All surface-water samples (N = 280) 

Minimum 0.2 0.00 0.1 0.00 0.0 0.00 0.1 0.02 Median 502.8 0.50 34.1 0.03 0.4 0.01 2.2 0.44 

Maximum 32,000,000 32,000 3,600,000 3,600 5,800 116 1,340 268 2

Background samples (N = 52) 

Minimum 12.0 0.01 0.1 0.00 0.0 0.00 0.1 0.02 Median 43.0 0.04 3.0 0.00 0.2 0.00 0.6 0.12 

Maximum 2,871 2.9 29.0 0.0 1.9 0.0 27.8 5.6 

Altered rocks/baseline (N = 55) 

Minimum 0.2 0.00 0.3 0.00 0.1 0.00 0.1 0.02 Median 308.3 0.31 9.6 0.01 0.3 0.01 1.1 0.23 

Maximum 18,410 18 2200 2 42 1 151 30 

Mixed mine effects (N = 48) 

Minimum 25.0 0.03 0.1 0.00 0.0 0.00 0.1 0.02 Median 408.5 0.41 47.0 0.05 0.2 0.00 2.4 0.47 Maximum 42,000 42 8,430 8 13 0 44 9 

Mine dump effects (N = 43) 

Minimum 56.0 0.06 0.1 0.00 0.0 0.00 0.1 0.02 Median 664.6 0.66 87.2 0.09 0.7 0.01 4.0 0.79 Maximum 2,000,000 2,000 85,000 85 1,600 32 244 49 

Mine drainage (N = 42) 

Minimum 330.0 0.33 1.0 0.00 0.0 0.00 0.7 0.14 Median 37,305 37.31 3,156 3.16 1.2 0.02 8.2 1.64 Maximum 772,000 772 65,100 65 422 8 96 19 

Mine pits and ponds (N = 21) 

Minimum 35.0 0.04 7.8 0.01 0.0 0.00 0.1 0.02 Median 1,303 1.30 223.8 0.22 1.1 0.02 5.3 1.07 

Maximum 9,600,000 9,600 3,600,000 3,600 369 7 170 34 2

Miscellaneous other waters (N = 20) 

Minimum 300.0 0.30 2.8 0.00 0.2 0.00 0.1 0.02 Median 100,000 100.0 8,300 8.30 3.7 0.07 30.9 6.19 Maximum 32,000,000 32,000 3,100,000 3,105 5,800 116 1,340 268 2WQS (ppb) 1,000 1,000 50 5 
10 Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada 

carried at these pH values. Near-neutral to alkaline waters (pH 

7–9) can carry significant concentrations of metal-oxyanions 

(Mo, As, Se) and uranium, as shown in the Humboldt data and 

discussed elsewhere. 

Because the toxicity of metals varies greatly from metal 

to metal, receptor to receptor (Smith and Huyck, 1999; Kelly, 

1999) metal-concentration values may be easier to understand 

in the context of water-quality standards that are set relative 

to the health of humans and wildlife (NDEP, 2002)1

. Human 

health tends to be more sensitive to some metals than is wildlife, hence drinking-water standards are quite low for As (50 

ppb), Pb (50 ppb), and Tl (thallium, 13 ppb). Aquatic wildlife 

is more sensitive than man to other metals, including Cd (ca. 5 

ppb), Cu (ca. 10 ppb), Hg (0.01 ppb), Mo (19 ppb), Se (5 ppb), 

and Zn (ca. 50 ppb). Iron is not a health risk to aquatic wildlife until concentrations reach 1,000 ppb. Enrichment factors 

shown in table 1 express magnitudes relative to water-quality 

standards. In general terms, the metal concentrations in some 

acidic mine waters in Nevada exceed various water-quality 

standards by large factors: As 100–600×, Cd 50–1,000×; Cu 

50–>5,000×, Pb 25–400×, Se 10–100×, and Zn 25–1,500×. 

Some ephemeral ponds located on mine dumps and tailings impoundments are even more metal rich than mine drainage waters, attaining extreme compositions by collection and 

evaporation of runoff waters (photograph 7). These waters can 

contain more than 10,000 ppb of several metals, including Cu 

and Zn, and also are rich in other elements including As, Cd, 

Hg, Se, and U. Compared to commonly applied water-quality 

standards, values for these metals are 200 to more than 75,000 

times higher than the regulatory standard. These ephemeral 

ponds are not typical of mine-related waters but are mentioned 

as a special problem that needs consideration in reclamation 

because acute toxicity in short-term exposure is likely. 

Relation to Ore Type 

The mineralogy and chemical composition of metallic 

ore deposits and their host rocks would logically determine 

the composition of mine waters from those deposits (Plumlee 

and others, 1999; duBray, 1995), but in my experience the 

wide range in water compositions from a deposit type blur the 

distinctions between deposit types (Nash, 2001; Nash, 2002). 

Compositions of mine waters from northern Nevada plotted 

by deposit type on figure 3 are not as distinctive as postulated 

by others. Some trace metals of concern, such as Se and U, 

can be elevated in acidic mine waters even from deposits that 

are not normally considered to be enriched in those elements. 

1

 The biology and chemistry of toxic metals are complex topics that are 

reviewed elsewhere (Langmuir, 1997; Kelly, 1999; Smith and Huyck, 1999). 

Water-quality standards are explained by Smith and Huyck (1999) and NDEP 

(2002), including aspects such as acute and chronic exposure, and drinkingwater and aquatic-life criteria. In detail, the toxic effects of many base metals 

(eg., Cd, Cu, Pb, Zn) are inversely related to water hardness; the values cited 

here are approximate and not corrected for hardness. 

Acidic mine waters are capable of mobilizing a wide array of 

elements, including many such as Al and Ti that are often considered “immobile” by geochemists. 

The most effective predictor of metal mobilities in waters 

affected by mining is pH, which relates to the abundance of 

acid-generating minerals such as pyrite relative to acid-consuming minerals such as calcite. In many settings in Nevada, 

host-rock lithologies provide suffi cient acid-neutralizing 

capacity to dominate acid production, producing neutral to 

alkaline waters that are capable of transporting only low concentrations of most metals (but locally high concentrations of 

a distinct suite of elements that includes As, Cd, Mo, Se, U, 

Zn, and occasionally Cu). Sedimentary rocks, especially calcareous shales and limestones, commonly provide the required 

neutralizing capacity, and in other terranes caliche in alluvium 

is effective. 

Evolution of Surface Waters 

Within Mining Areas 

The composition of mine drainage waters changes downstream from the sources in response to several processes that 

generally improve water quality. The one exception is the case 

of mine waters reacting with mine dumps, which generally 

results in added acidity and increased metal concentration. In 

Nevada, attenuation of metal concentration can be observed up 

to the point at which waters infiltrate alluvium and cannot be 

sampled. Reactions continue in shallow ground water but are 

not considered here because wells generally are not available 

for sampling. In most situations, water compositions change 

over a distance of 100 m or more downstream from a mine 

source; these waters are here termed “mixed” if there is evidence for addition of other surface or spring waters and reactions, all of which raise pH and lower conductivity. The mixed 

waters have pH values in the range of 3 to 8. These mixed 

waters are of interest for both their geochemistry and their 

implications for beneficial use—they are important because 

they are much larger in volume than mine-source waters and 

provide more wildlife habitat. 

Improvements in water quality by natural processes 

involve reactions of several kinds that raise pH and decrease 

metal concentrations. Several processes can be involved: 

(1) oxidation and formation of Fe- and Mn-oxyhydroxide 

phases; (2) ion exchange, as on clays or organic materials; (3) 

adsorption, especially on fine-grained or amorphous Fe- and 

Mn-phases; (4) flocculation of colloids and sedimentation of 

particles; (5) sulfate reduction, generally mediated by bacteria; 

and (6) uptake by plants. In the study area, processes 1 and 3 

seem to be most important, whereas 5 and 6 are rare. 

Hydrous iron oxide (FeOx) phases of various compositions and red, orange, and yellow hues are typically involved 

and are important for the removal of metals such as Cu, Pb, 

and As, consistent with the theory and observations of Smith 
Overview of Mine Drainage Geochemistry, Humboldt River Basin and Adjacent Mining Areas, Nevada 11 

Photograph 7. Very acidic (pH 1.9) water collects in this cut into sulfidic mill tailings at the Caselton 

mill tailings impoundment. Metal concentrations are extremely high, in part by seasonal evaporation. 

(1999). The fact that the Nevada acid mine waters start with 

high iron concentrations makes these reactions possible. These 

adsorption reactions in nature, over the pH range of about 3 to 

7, are the basis for the concept of “self-mitigating capacity” 

(Smith, 1999). Mixing and precipitation is evident in several 

of the larger mine drainages in the study area where several 

kinds of surface and spring waters mix with mine waters over 

distances of hundreds of meters. Examples of natural attenuation and improvement of water quality in five mining areas 

will be discussed next. 

National Mine Area 

A simple example of natural attenuation is the case of 

the National mine complex (photograph 8) and evolving water 

compositions in Charleston Gulch, shown graphically in fi g. 

4. The collapsed mine adit releases a moderate fl ow (10–20 

gpm) of pH 2.8–3.1 water (photograph 9) that interacts with 

mine waste for about 125 m (photograph 10), at which point 

the main flow of mine water joins a stream from the southwest 

(a basin with small prospects). The mixed waters fl ow over 

the remains of a tailings pond and through several breached 

catch ponds. Small streams from the east and west join the 

stream about 550 to 650 m north of the adit. Probing of water 

in the area of the dump, stream inflow, and tailings (125–250 

m north) showed large local changes in conductivity and 

somewhat smaller variation in pH readings, both of which are 

considered to indicate mixing of several kinds of surface and 

shallow ground waters. The chemical analyses (fig. 4) show 

that metal concentrations increase during reaction of the acid 

mine drainage and mine waste. North of the mill tailings, pH 

values rise from less than 3 to 4.3, and conductivity values 

decrease, possibly from diffuse inflows (springs). Relatively 

small amounts of FeOx precipitate in this reach. The stream 

does not change much in appearance or pH values until two 

side inflows—each larger than the stem from the mine; this 

quadruples the volume of the stream—at which point pH 

rises to 6.0 and conductivity decreases by more than 60 percent. Metal concentrations are greatly reduced after these 

mixing reactions: Zn concentration is down to 100 ppb, and 

Cu is down to 5 ppb. The quality of the evolved water about 

a 0.6 km north of the adit has improved to approximately the 

aquatic-life standard. 

Hilltop Mine Area 

Another example, from the central Hilltop district, 

involves acidic mine drainage from a mine adit that fl ows over 

mill tailings in an unnamed small creek (photograph 11; fi g. 

5). The adit (in siliceous rocks with low neutralizing capacity) 

yields about 10 gpm of pH 2.7–2.9 water. The mine drainage 

flows into the creek, which then flows over eroded mill tailings for about 150 m. About 550 m north of the adit, the small 

stream joins the East Fork, a larger stream from a basin with 

only a few small mine prospects. The East Fork joins another 

large stream about 1,800 m north-northwest of the adit to 

become Rock Creek. Spring-fed headwaters in altered sedimentary rocks start with low metal concentrations (fig. 5). Metal 
1 

12 Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada 

10,000,000 1,000 

1,000,000

100,000 100 

Arsenic in PPB Aluminum in PPB 

10,000 

1,000 

Zinc in PPB Lead in PPB Selenium in PPB 

10 

100 

10 1 

0 

1 2 3 4 5 6

Deposit type

0 

7 1 2 3 4 5 6 

Deposit type 

1,000,000 1,000 

100,000 

100 10,000 

1,000 

10 

100 

10 

1 

1 

0 0 

1 2 3 4 5 6 7 1 2 3 4 5 6 7 

Deposit type Deposit type 

10,000,000 10,000,000 

1,000,000 1,000,000 

100,000 100,000 

Copper in PPB 

10,000 10,000 

1,000 1,000 

100 100 

10 10 

1 1 

0 0 

1 2 3 4 5 6 7 1 2 3 4 5 6 

Deposit type Deposit type 

mine mixed mine mixed 

Explanation: water types: mine waters sampled at adit or dump; mixed waters are streams sampled below mines or mill tailings. 

Deposit types: 1, acid-sulfate; 2, polymetallic vein; 3, massive sulfide; 4, skarn; 5, sediment-hosted gold; 6, epithermal vein ; 7, mercury. 

Figure 3. Relations of metal concentrations in mine drainage to deposit type. 

concentrations increase in the creek from the adit inflow, but it 

is not clear if metals are released from the tailings. Relatively 

small amounts of FeOx coat the stream channel, which could 

be explained by several kinds of mixing reactions, including 

seeps from the tailings. There is relatively little precipitation of 

iron oxides from these mixed waters compared to the examples 

described next. The unnamed creek joins the larger East Fork 

and for about a hundred meters there are thin white fi lms on 

the stream bed, probably an Al-oxyhydroxide mineral. The pH 

rises from 4.2 to 7.1–7.8, and samples collected about a hundred meters north of the junction have much lower metal concentrations and meet quality standards for aquatic life. 

Dean Mine Area 

Tunnels created during mining of sulfide-rich veins in the 

western part of the Hilltop district nearly 100 years ago were 

7 

7 
Overview of Mine Drainage Geochemistry, Humboldt River Basin and Adjacent Mining Areas, Nevada 13 

Photograph 8. The National mine and associated mine dumps at an elevation of 1,800–2,100 m 

receive substantial snow and rain, causing more mine drainage than in most areas in northern 

Nevada. 

Photograph 9. The collapsed mine tunnel at the National mine releases acidic mine drainage (pH 

2.9), but the flow is only about 10–20 gallons/minute. 

reopened for exploration in 1988–1994. These mine work- limestone released pH 7 to 7.5 waters (in detail, the pH varied 

ings, about 3 km west of the Hilltop mine, created very acidic, over a 3-year time period). The mine drainage from several 

metal-rich drainage (fig. 6) for about six years until the tun- upper adits flowed less than 50 m to a small stream, and for 

nels and mine dumps were reclaimed in 1998. The abandoned about 600 m those waters precipitated large amounts of ocher 

Dean adits created flows and pools of pH 2–3 waters (photo- FeOx on the stream bed. The mixing zone, from about 600 

graph 6, photograph 12) where the workings were in siliceous to 1,100 m north (fig. 6) involved a combination of limestone 

rocks, but a similar tunnel exploring the same vein system in strata and numerous spring inflows with conductivity values 
14 Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada 

Photograph 10. Acidic mine drainage from the National mine flows over mine waste and tailings 

(left side of photograph), thereby accumulating even more acid and metals. 

0 

1 

10 

100 

1,000 

10,000 

100,000 

Metal in ppb

Tributary, west 

National mine area

0 100 200 300 400 500 600 700 800

Meters north

Copper Zinc Aluminum 

Figure 4. Evolution of mine drainage in the National mine area. 

900 
Overview of Mine Drainage Geochemistry, Humboldt River Basin and Adjacent Mining Areas, Nevada 15 

Photograph 11. Mill tailings from the Hilltop mill, placed in the channel of an ephemeral stream, 

react with seasonal surface waters, adding acid and metals. 

1,000,000 

100,000 

10,000 

1,000 

100 

10 

1 

0 

-500 0 500 1,000 1,500 2,000 2,500 3,000 

Metal in PPB 

headwaters 

pH 6.9 

adit waters, 

pH 2.7-2.9 

mill tailings 

East Fork, 

pH 8.4 

Junction 

Rock Creek 

in-stream concentrations 

Mixing 

Hilltop mine area 

Meters northwest 

Zinc Copper Aluminum 

Figure 5. Evolution of mine drainage in the Hilltop mining area. 
16 Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada 

that varied by more than 100 percent at sites a meter apart. 

Mixing of pH 3–4 stream waters with pH 8.2 spring waters 

caused immediate flocculation of FeOx and reduction of metal 

concentrations by more than an order of magnitude. Mixing 

in the vicinity of the lower adit flow and limestone-rich waste 

dump was complex: the mine drainage clearly added metals, 

but it also added alkalinity and raised the pH. Reactions continued down the stream, and at the 2,100 m mark the metal 

concentrations were at or below aquatic-life standards. Mixing 

with the main stem of Rock Creek further attenuated metal 

concentrations. Two relatively large mill tailings piles (5,800- 

to 7,200-ft marks of fig. 6) produced no measurable input to 

the creek, but sampling of ground water (which would require 

wells) might yield definitive results. This small basin demonstrates the self-mitigating effects of high-iron waters described 

by others (Drever, 1997; Langmuir, 1997; Smith; 1999). Brief 

study and sampling in June of 1999, after the mine adits were 

plugged and mine dumps were reclaimed by NDEP-BLM in 

1998, suggested greatly improved water quality (photograph 

13). 

Galena Canyon Area 

A fourth example comes from a complex watershed on 

the northeast side of the Battle Mountain district in the area 

of Butte, Galena, and Iron Canyons. High precipitation in the 

spring seasons of 1998 and 1999 created substantial fl ow from 

some historical mine adits and springs in this area of polymetallic veins in sedimentary rocks (siltite and chert). The springs 

in this area are notable for their high conductivities (2,000– 

4,500 microsiemens per centimeter—μS/cm) and high sulfate 

content (150–4,000 ppm), and pH values from 3 to 4. Mixing 

of several kinds of surface and spring waters produced copious 

amounts of ocher FeOx (photograph 14) that resembled schwertmanite (Fe-hydroxy-sulfate; Desborough and others, 2000), 

which forms below pH 3.5. A traverse, shown schematically 

on figure 7, starts with extremely acid, metal-rich mine drainage that flows over a large sulfidic dump (photograph 15) and 

mixes with surface waters and spring waters over a distance 

of about 1,200 m. Mixing in this zone caused FeOx deposition, but the pH stayed between 3.2 and 3.4, probably refl ecting acid released during hydrolysis of iron. Another factor in 

this reach was a layer of ferricrete that coated alluvium in the 

bed. At the 1,500-m mark (fig. 7) this small fl ow (20–40 gpm) 

joined the much larger Galena Canyon creek (400–700 gpm 

during flood stage), resulting in a pH rise to 6.8. This mixing 

zone of milky and rusty waters extended for 100–200 m. The 

evolved waters had much lower metal concentrations, less 

than 1 percent compared to the source, but still high in Al, 

Cd, Cu, Fe and Zn. The outflow of metals and acid in June of 

1999 appears to have overwhelmed the capacity of the area 

Photograph 12. A series of mine tunnels in the Dean Mine complex released acidic drainage that 

reacted with sulfidic waste rocks. The siliceous wallrocks at the upper tunnels provided no acid 

neutralization, but the lower tunnel (gray rocks, upper part of photograph) was in limestone and 

the mine drainage was near neutral. These tunnels were plugged and the dumps reclaimed in 1998, 

with major improvements in water quality. 
Overview of Mine Drainage Geochemistry, Humboldt River Basin and Adjacent Mining Areas, Nevada 17 

Photograph 13. The creek flowing north from the Dean mine workings and dumps was acidic and 

choked with iron flocculate in 1997, but the reclamation in 1998 produced a marked improvement in 

water quality. In June of 1999 the water was clear and created a small amount of white precipitate 

of aluminum at pH 7.2. 

0 

1 

10 

100 

1,000 

10,000 

100,000 

Metal in PPB 

Mixing inflows 

in-stream concentrations 

Mine sources 

Dean mine area 

0 500 1,000 1,500 2,000 2,500 3,000 

Meters north 

Zinc Copper Aluminum 

Figure 6. Evolution of mine drainage in the Dean mining area. 
18 Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada 

Photograph 14. The ocher materials shown here formed when acidic mine drainage in Iron Canyon 

evolved to higher pH, causing iron minerals (possibly schwertmanite) to precipitate. Concentrations 

of copper and other base metals decreased as they were adsorbed on the iron flocculate. 

Photograph 15. The sulfidic mine dump in Butte Canyon is fairly typical of mine waste from a 

polymetallic vein deposit. Mine drainage reacts with the dump waste and adds acid and metals to 

water that has a pH of 2.2 at the collapsed portal. 

to accomplish natural attenuation. During this unusual spring Coon Creek—An Unusual Example 

“flood” of 1999, similar acidic waters from historical mine 

adits and springs were treated by Battle Mountain Gold using Coon Creek, flowing west from the Rip Van Winkle mine 

a temporary water-treatment plant in adjacent Iron Canyon. (photograph 16), is an example of how physical conditions 

During normal spring runoff, the springs and adit discharges in control the chemistry of mine waters. The lower tunnel is dry, 

these canyons flow on the surface for only 100–200 m. and no seeps come from the waste dumps. The concern here is 
Overview of Mine Drainage Geochemistry, Humboldt River Basin and Adjacent Mining Areas, Nevada 19 

Zinc in PPB 

1,000,000 

100,000 

10,000 

1,000 

100 

10 

1 

0 

Spring 

Adit 

Mine dump 

Galena Creek inflow, 

mixing 

Butte-Galena Canyon 

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 

Meters north 

Zinc Copper Aluminum 

Figure 7. Evolution of mine drainage in the Galena mining area. 

for stream waters flowing over, and through, mill tailings (photograph 17). Geochemical results are summarized on fi gure 

8. Four visits to this area from 1996 to 1999 provided results 

that seem paradoxical on first examination. Measurements of 

pH of stream waters in contact with tailings showed values 

to be consistently in the range of 6.8 to 7.4, rising to about 

8.4 west of the tailings. Laboratory leach tests (Nash, 2001) 

confirmed the expectation that the sulfidic tailings should 

create acidic, metal-rich waters, but no such surface waters 

were detected. Closer inspection on the third visit disclosed 

thin films of red FeOx precipitate along the edge of the creek 

next to the tailings, and depressions made by cattle hooves 

contained small pools of reddish water. The red seeps proved 

to have pH values of 1.7 to 2.1 and very high conductivity 

(2,000–4,000 microsiemens per centimeter). Not surprisingly, 

chemical analyses of the acidic seeps showed extremely high 

metal concentrations, especially for Cu and Zn, which were 

more than 40,000 and 1 million ppb, respectively. Cadmium 

mimics Zn, reaching more than 8,000 ppb in tailings seeps. 

Repeated sampling of Coon Creek shows that relatively small 

concentrations of metals actually enter the stream (about 

200–400 ppb Zn) despite the evidence in leach tests and in the 

seep waters for thousands of ppb of Zn and other metals. The 

discrepancy appears to be explained by high clay content in 

the tailings that gives them very low permeability: only small 

amounts of water can infiltrate, react, and exit these tailings. 

The conclusions for this mining area are (1) despite moderate 

precipitation (about 25 cm/year), little or no water from waste 

dumps and mine workings enters the nearby creek, and (2) 

although mill tailings are in contact with stream waters, the 

high potential for acid generation and metal release are limited 

by low permeability. Poor mining practices and potentially 

reactive waste materials at this mine ultimately produce only 

slightly degraded water. Natural attenuation further minimizes 

metal concentrations within about a 0.5 km of the last tailings 

impoundment. 

Attenuation Mechanisms 

Three stages in a related process appear to be involved 

in the attenuation of metals in the areas described above 

(1) mixing of waters, (2) rise in pH, and (3) precipitation of 

Fe-Mn oxides and adsorption of trace metals. The attenuation reactions start with mixing of waters, seen clearly at the 

junction of tributary streams, and inferred from measure­
20 Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada 

Photograph 16. View of Rip Van Winkle mine area with tailings six ponds in Coon Creek. The mine 

tunnel and waste dump (dark gray) are in the right side of the view. 

Photograph 17. Acidic seepage from the Rip Van Winkle tailings create thin films of red iron minerals on mixing with Coon Creek. Shown here is a high flow stage for this small creek in June of 1997. 

ments of locally variable and low conductivities that suggest 

ground-water inflow (springs) into the stream. Reactions of 

acidic mine waters with rocks and alluvium also are likely 

but not evident in the spatial distribution of conductivity and 

pH values, which do not change immediately at lithologic 

contacts. More specifically, the inflowing surface and ground 

waters attain high alkalinity values by reaction with rocks and 

alluvium, and the high-alkalinity waters neutralize the acidity 

of the mine waters. The high alkalinity of surface and ground 

waters (median 170 ppm CaCO3

, many values > 200 ppm 
Overview of Mine Drainage Geochemistry, Humboldt River Basin and Adjacent Mining Areas, Nevada 21 

Metal in PPB 

10,000,000 

1,000,000 

100,000 

10,000 

1,000 

100 

10 

1 

0 

Rip Van Winkle mine area 

Coon Creek 

Tailings pore waters 

Spring inflows 

in-stream concentrations 

-500 0 500 1000 1500 2000 2500 3000 

Meters west 

Zinc Copper Aluminum 

Figure 8. Evolution of mine drainage in Coon Creek west of Rip Van Winkle mine. 

CaCO3) is an important factor in the efficacy of this process. 

As the pH of the mixed water rises from below 3 to more 

than 4, red to ocher FeOx coatings precipitate in the channel. 

Some of this has the appearance of schwertmanite (Fe-oxysulfate; Desborough and others, 2000) and is especially abundant in the Iron Canyon–Butte Canyon area (photograph 14). 

Concentrations of trace metals in water, especially As, Cu and 

Pb, decrease sharply along with the decrease in Fe at about pH 

4 (fig. 2; fig. 9). Concentrations of Zn and Cd also decrease, 

but less dramatically, and a higher fraction of these metals stay 

in solution at pH values of 4 to 7. Plots of metal concentrations vs. Fe concentration show the strong correlation (fi g. 9); 

concentrations of Cd, Co, Cu, Ni, Pb, and Zn decrease with Fe 

over the pH range of about 4 to 7. The behavior of As, which 

is not a base metal, differs from those metals. The decrease in 

As concentration from pH 3 to 5 could be evidence for adsorption onto FeOx as they flocculate. The general increase in As 

at pH values above 7 (fig. 9) suggests the adsorption mechanism does not hold under alkaline conditions and low Fe concentrations where As is soluble or desorbs from FeOx. If one 

plots the trace-metal concentrations against an unreactive element, such as Na or Sr (which are called “conservative”) there 

is no correlation (fig. 9)—suggesting that dilution is not a significant factor in the attenuation of metals. The compositional 

trends and metal associations strongly resemble the adsorption 

experiments of Smith (1999). More detailed, more closely 

spaced sampling would clarify the attenuation mechanism(s). 

As observed elsewhere (Nash, 2002; Plumlee and 

others, 1999), Zn and Cd concentrations, and in places Cu 

concentrations, remain high after neutralization in these 

mixing reactions. This is predicted by adsorption reaction 

models (Smith, 1999). Once the waters evolve through the 

pH 4–7 range and FeOx phases flocculate, there are few 

other natural reactions that can remove signifi cant amounts 

of Zn and Cd. Carbonate and hydroxide phases of Zn-Cd 

can precipitate, but only at higher concentrations or higher 

pH conditions than observed here. Alkaline waters can carry 

significant amounts of the oxyanions As, Mo, and Se above 

pH 7, regardless of whether there is acidic input to those 

waters. Because alkaline waters predominate in Nevada, 

more attention is needed on the effect of metals (including 

oxyanions) in these waters and the possibility of longdistance transport to playas or sinks where evaporation will 

increase metal concentrations. 

3500 
1 

22 Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada Cu/Ca 

0.1 

1 0.01 

0.001 0.1 

100 1000 

10 

100 

1 

?

? 

Fe in PPB As/Fe Fe in PPB 

10 

1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 

pH pH

1000 100,000

100 

10,000 

10 

Zn/Sr Ni/Na

1,000 

0.1 

100 

0.01 

0.001 10 

1 2 3 4 5 6 7 8 9 0 1 10 100 1,000 10,000 

pH Cu in PPB 

1,000.00 100,000 

100.00 

10,000 

10.00 

0.10 

100 

0.01 

0.00 10

1.00 1,000 

1 2 3 4 5 6 7 8 9 0 1 10 100 1,000 10,000 100,000 

pH Zn in PPB 

Figure 9. Evolution of mixed mine-related waters as a function of pH, iron, and unreactive elements. 

Quality of Streams 

Leaving Mining Areas 

The quality of surface waters flowing a kilometer or more 

from mining areas may be of greater significance than that 

found locally at mine adits or near mine waste because those 

waters more distant from mining are used by wildlife, ranches 

or farms, and by humans. However, few streams actually fl ow 

out of the historical mining districts in the Humboldt River 

basin. Study of the 40 mining areas shows that 17 mining 

areas have no streams flowing near the mines, or the streams 

flow only on rare occasions (i.e., they were not fl owing during 

the wet years of 1998 and 1999). Eight (20 percent) of the 

mining areas have ephemeral streams that fl ow after storm 

events, and 5 (12 percent) have intermittent streams that fl ow 

for several weeks of the wet season. Ten mining areas (25 

percent) are drained by substantial streams that may fl ow 

most of the year, but the largest of these is less than 3 m wide. 

Only one of the streams, the North Fork of the Little Humboldt River (east of the Buckskin-National mine), flows into a 

tributary of the Humboldt River. Several of the larger streams 

flow into internal drainages (such as Star Creek, outside of the 

Humboldt River watershed) and most flow out of canyons and 

infiltrate thick caliche-bearing alluvial deposits at the range 

front (such as Galena and Iron Creeks). 

Water was sampled from 13 streams downstream from 

where these streams interacted with mines, mine waste, or 

mill tailings to determine the amount of metal contamination 

leaving the mining area. Several streams flowing from areas 

of mining were not sampled because they did not interact 

with significant mines or mined materials. Analytical results 
Overview of Mine Drainage Geochemistry, Humboldt River Basin and Adjacent Mining Areas, Nevada 23 

are summarized for four of the most signifi cant, potentially 

toxic metals (As, Cd, Cu, and Zn) in table 2. The sampling 

sites were as far from the mining areas as possible (close to 

the point of disappearance into alluvium) or about 2–4 km 

downstream from mining. The metal concentrations are quite 

low at these sites, and all appear to be close to or lower than 

the concentration values stipulated for likely benefi cial uses, 

chiefly aquatic life. Concentrations of As are high at six sites, 

but the measured values of 19 to 37 ppb are below the most 

demanding criterion, domestic drinking water. Zinc is elevated 

at several sites, but the highest values in the range of 43 to 

100 ppb, are close to the aquatic life water-quality standard. 

Copper is elevated (3 to 13 ppb) at six or more sites, and these 

values may be high enough to have adverse effects on aquatic 

life. Some of these more complicated situations are discussed 

next for streams that have class designations. 

Six headwater streams in northern Nevada that are contaminated by mine-related effluent are shown on fi gure 10. 

The metal concentrations in these streams are thought to be 

elevated and a possible threat to aquatic life, but more detailed 

sampling needs to be done. Only short distances, comprising a 

small fraction of the larger streams in northern Nevada, appear 

to be contaminated by effluent from historical mines. 

Nevada Class-A Waters in Mining Areas 

The waters of Nevada are classified in a system of 

classes, A to D, based on the amount of human or industrial 

activity and beneficial uses (NDEP, 2002). Some streams in 

or near mining areas have been designated as class-A waters, 

the most pristine in the State and therefore having the most 

stringent quality standards. The NDEP quality standards for 

class-A waters use phrases such as “None attributable to man’s 

activities” and “None” for toxic materials (NDEP, 2002). The 

chemical criteria for water quality are related to benefi cial 

uses such as municipal or domestic water supply and aquatic 

life, and the tabulated criteria (NDEP, 2002, code 445A.119 

and elsewhere) are generally based on the same scientifi c and 

technical information used by EPA and other State agencies. 

Where there are multiple beneficial uses, the most stringent 

criterion is used; for instance, the Cu criterion for aquatic life 

and the As criterion for drinking water. Many pages of class-A 

waters are listed and are a bit confusing because of the “tributary rule” whereby headwater tributaries apply if the stream is 

listed. 

Parts of eight historical mining districts studied here are 

in headwaters designated class-A waters: (1) Star Creek, Pershing County; (2) Bottle Creek, Humboldt County; (3) Quinn 

River, Humboldt County; (4) North Fork Little Humboldt 

River, Humboldt County; (5) Lewis Creek, Lander County; 

(6) Birch Creek, Lander County; (7) Maggie Creek, Elko 

County; and (8) North Fork Humboldt River, Elko County. 

The Cu concentration in Star Creek and the Zn concentration in Coon Creek (tributary to Maggie Creek) appear to 

exceed the stringent standards in those class-A waters. Birch 

Creek near the Quito mine may be slightly contaminated by 

seeps from mine waste, but the main stem of Birch Creek 

seems to have good water quality. Bottle Creek in the Jackson Mountains does not appear to be infl uenced by the Bottle 

Creek mercury district, which is in a basin to the northeast. 

The contamination from the National mine, described earlier, 

infl uences Charleston Gulch, a tributary of the Quinn River 

that is designated a class-A water. Gance Creek, a tributary 

of the North Fork of the Humboldt River in the Independence 

Range, fl ows through the Black Beauty mine (LaPointe and 

others, 1988); seeps from the mine waste dumps contaminate Gance Creek (photograph 18), but the seeps are small 

in comparison with the stream and the high neutralization 

capacity from the carbonate rocks of the area probably mitigates the acidic seeps within 200 m (but no analyses were 

made). The headwaters of Lewis Creek (Dean Creek) fl ow 

close to mine waste and mill tailings from the Morning Star 

mine, which discharge a few low-fl ow seeps of relatively low 

metal concentration; no downstream sample was collected, 

but I presume that natural processes reduce the concentrations 

to acceptable levels within a few hundred meters. I did not 

sample the headwaters of the North Fork of Little Humboldt 

River east of the Buckskin mine, but it probably is somewhat 

contaminated (fi g. 10). 

Table 2. Composition of streams leaving six mining areas in northern Nevada. 

[Cond, conductivity] 

Site Number of Distance pH Cond Al As Cd Cu Fe Zn 

samples (m) (PS/ m) c (ppb) (ppb) (ppb) (ppb) (ppb) (ppb) 

Dean mine avg 2 2,050 7.6 440 66 3.0 2.9 2.9 355 48 

Hilltop mine avg 2 700 7.5 500 108 35 1.6 9.1 222 19 

Hilltop district 1 2,400 7.6 290 32 7.8 0.2 2.0 49 8.0 

Butte mine 1 1,800 6.9 810 102 6.2 63 91 1,310 1,085 

National mine 1 760 6.0 200 51 2.0 0.3 5.0 110 100 

Rip Van Winkle mine avg 3 1,200 8.1 420 36 24 3.7 13 320 265 
24 Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada 

Lander 

Eureka 

Churchill 

Humboldt 

Basin 

Potosi 

Ivanhoe 

Scraper 

Springs 

Burner 

Railroad 

Cortez 

Eureka 

Austin 

Lewis 

Buffalo 

Golconda 

Adelaide 

Bottle 

Creek 

Imlay 

Star 

Willard Rochester

Mineral 

Basin 

Safford 

Beowawe Majuba 

117° 

41° 

Modarelli 

Humboldt 

Pershing 

+

+

+

+

+

+ +

+

Midas

I-80 

I-80 

+ 

+ 

+ 

+ + 

+ 

National

Hilltop

Black

Diablo

+ 

Maggie

Crk

Quinn

River

Merrimac

Elko 

White Pine 

North Battle Mtn 

Mountain City 

River 

Gold Circle 

Tuscarora 

Independence Mts 

Swales Mtn 

Tenabo 

Mount Hope 

Valley 

Iron Point 

Awakening 

Tenmile 

Buena Vista 

Antelope Springs 

Trinity 

Seven Troughs 

Birch Creek 

Lovelock

White Pine 

Mill City 

Battle Mountain

Winnemucca

Eureka

Elko

Austin

US 95 

US 93 

N 271 

US 50 

Battle Mtn

North Fork

Possibly contaminated + Major source of contamination 

0 Scale in Miles 50 stream 

Figure 10. Major sources of contamination and possibly contaminated streams in northern Nevada. Six stream segments, shown in 

purple, have elevated metal concentrations that may be threats to aquatic health within a few kilometers of mines. 

Class-B waters, with less stringent quality standards than 

class A, are downstream from the headwater reaches, often 

in the foothills regions bordering the National Forest lands, 

where there is minor to moderate influence by man’s activities 

(such as ranching). None of the areas studied were in class-B 

waters, but many of the current mining operations, such as the 

Carlin trend, are near these waters. 

Nevada also classifies some of its larger streams and 

rivers by a system of beneficial uses that differs from the class 

system. Six segments of the Humboldt River are described in 

detail (NDEP, 2002, 445A.202-445A-207), including quality 

standards based on beneficial uses. Tributaries are covered by 

the tributary rule but not specifically listed. Some of the headwater streams in historical mining districts described above 

under class-A waters may be considered tributaries to the 

Humboldt River. 

Metal Loads and Total Maximum Daily Loads 

Toxicity and health effects of water are generally related 

to concentrations of contaminants (Manahan, 1994; Smith and 

Hyuck, 1999), but in recent years there has been increasing 

use of metal loads for watershed management (Black, 1996; 

NDEP, 2002). Metal loads and associated concepts were part 

of the original Clean Water Act in 1972 when the concept of 
Overview of Mine Drainage Geochemistry, Humboldt River Basin and Adjacent Mining Areas, Nevada 25 

Photograph 18. Sulfidic mine waste at the Black Beauty mine, Independence District, releases 

acid (pH 2.4) and metals to seeps that flow into Gance Creek. 

total maximum daily load (TMDL) was introduced. The State 

of Nevada is developing methods and priorities for waterquality management by TMDLs (www.ndep.state.nv.us/ndep/ 

bwqp/tmdl/htm/). 

Metal loadings, defined as the metal concentration times 

flow volume and expressed in terms such as pounds or grams 

per day, provide an alternative way to evaluate or rank miningrelated water contamination. One complication is the need 

for a measurement of stream flow, a complicated task. I have 

made estimates for small flows from mine workings, seeps, 

and streams in the 1- to 300-gallons-per-minute range. Examples of metal loads are in table 3 in which loads, in grams/day 

(g/d), are computed for four sources and four downstream 

flows after mixing and attenuation. To help understand magnitudes, the loads are compared with those computed for 

the Humboldt River. All of these values are approximate 

estimates, with an uncertainty of about ± 100 percent (for 

uncertainties in both analytical values and in Q, fl ow volume). 

The Humboldt River samples (three) are from the main stem 

between Battle Mountain and Dunphy. The loading values are 

easiest to grasp when considered relative to other values in the 

same units (grams per day): 

1. 	 Metal loads decrease significantly downstream from 

sources, reflecting the benefits of attenuation reactions. 

The in-stream values are low compared to those at 

source adits or seeps. 

2. 	 Metal loads for all metals at historical mine sources 

are low in comparison to those of the Humboldt River, 

chiefly because of the low flow volume at the mine 

sources. 

A good example of the load “paradox” is in the values 

for As: the concentration of As is relatively low (8 to 9 ppb 

in my analyses) in the Humboldt River, well below the drinking-water standard (50 ppb), but the load of 10 grams/day is 

much higher than for the mine drainages. Likewise, for Cu and 

Zn the concentrations in the Humboldt River are low (3 and 1 

ppb, respectively), but the loadings are 100-fold higher than 

the highly concentrated but low-flow mine drainages. None of 

the sampled mine waters flow into the Humboldt River. This 

comparison to the Humboldt River is highly simplistic but 

makes the point that the metal loadings from historical mining 

areas studied are low relative to the largest flow of water in the 

region. 

Discussion and Conclusions 

Reconnaissance hydrogeochemical studies of the Humboldt River basin and adjacent areas of northern Nevada have 

identified local sources of acidic waters generated by historical mine workings and mine waste. Where waters attain pH 

values of less than about 3, the waters mobilize extremely 

high concentrations of many potentially toxic metals; these 

conditions generally occur where large amounts of pyrite are 

oxidizing but also can be created when sulfate mineral crusts 

on the surface of mine waste and mill tailings dissolve during 

brief storm events. Metals that are enriched and potentially 

toxic in these acidic mine waters include Al, As, Cd, Cu, Fe, 

Mn, Pb, Se, and Zn. Only in a few rare instances are some 
Table 3. Examples of metal loads from mining areas compared to Humboldt River. [Cond, conductivity in microsiemens per centimeter. Q, flow in gallons per minute (gpm); LRH, load relative to Humboldt River; loads in grams per day (g/d). Water types—MSWL, stream leaving mining area; TPW, tailings pore water. na, not analyzed] 

Sample ID pH Cond Water type Q Al Al As As Cu Cu Fe Fe 

(PS/cm) (gpm) (g/d) (LRH) (g/d) (LRH) (g/d) (LRH) (g/d) (LRH) 

Battle Mountain district 

NNW131 3 >2,000 MDW 2.5 0.18 0.00 0.11 0.01 0.19 0.03 2.86 0.01 

NHW834 8.5 510 SWL 25 0.01 0.00 0.00 0.00 0.00 0.00 0.11 0.00 

Hilltop district 

NHW498 2.7 1,740 MDW 2.5 3.38 0.09 0.11 0.01 0.12 0.02 3.01 0.01 

NHW505 7.1 470 SWL 25 0.03 0.00 0.00 0.00 0.00 0.00 0.05 0.00 

NN0W320 7.8 414 SWL 250 0.01 0.00 0.01 0.00 0.00 0.00 0.06 0.00 

Merrimac district 

NHW650 1.8 2,500 TPW 0.1 0.35 0.01 0.10 0.01 0.03 0.00 2.63 0.01 NNW995 7.9 444 SWL 5.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

National district 

NHW629 3.1 1,430 MDW 10.0 1.13 0.03 0.03 0.00 0.01 0.00 6.27 0.01 NNW120 2.7 1,415 MDW 10.0 1.64 0.05 0.02 0.00 0.02 0.00 1.47 0.00 

NNW124 6 202 SWL 500.0 0.14 0.00 0.01 0.00 0.01 0.00 0.30 0.00 

Humboldt River 

Hum. R. (avg 3) 7.8 370.0 SW 225,000 35.9 1.00 10.4 1.00 5.88 1.00 438.6 1.00 
Overview of Mine Drainage Geochemistry, Humboldt River Basin and Adjacent Mining Areas, Nevada 27 

other elements, such as Mo, Sb, Te, Tl, and U, enriched sufficiently to pose a health threat to humans or wildlife. The 

processes that create these acidic, metal-rich waters in Nevada 

are the same as for other parts of the United States or the 

world, but the scale of transport and the fate of metals differs. 

In Nevada, acidic solutions do not migrate as far as in mining 

areas elsewhere because natural processes generally act to 

neutralize and attenuate metal concentrations within less than 

a kilometer of the source. The arid climate and associated soilforming processes explain the reduced scale of metal mobility 

in Nevada. The same processes and the importance of caliche 

soils can be expected in similar climatic regimes of the Great 

Basin or other arid parts of the world. 

Acid mine drainage is rare in historical mining districts 

of northern Nevada, and the volume of drainage rarely exceeds 

about 20 gpm. My findings are in agreement with those of 

Price and others (1995) who estimated that less than 0.05 percent of inactive mines are likely to be a concern for acid mine 

drainage. Most historical mining districts have no draining 

mines, and only a few have as many as three. Most drainage 

from mine workings appears to be related to melting snow 

plus spring rains; runoff from mine-waste dumps or mill tailings is generally limited to a few weeks of a year. Only in two 

districts (Hilltop and National) does water affected by mining 

flow into streams of significant size and length (more than 

10 km). 

The results of these reconnaissance studies offer encouraging evidence that abandoned mines in northern Nevada 

create only rare and local water-quality problems. In this semiarid climate, the high neutralization capacity of caliche soils 

and other natural processes are sufficient to compensate for 

these generally small sources of contamination. A few of the 

headwater streams in class-A watersheds may warrant more 

specific studies by specialists to determine in more detail the 

scale and magnitude of contamination. These results may provide useful analogs for future mining in the Humboldt River 

basin, but care must be given to matters of scale. Larger volumes of waste and larger volumes of water could easily overwhelm the delicate balance of natural attenuation described 

here. One example of this may be the problems that developed 

in Iron Canyon of the Battle Mountain district in the unusually 

wet spring of 1998 that caused acidic drainage to flow 2 to 5 

times farther than in normal seasons. 

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Manuscript approved for publication December 3, 2003 

Published in the Central Region, Denver, Colorado 

Editing, page layout, photocomposition—Richard W. Scott, Jr. 

Graphics and photographs by the author