U.S. GEOLOGICAL SURVEY BULLETIN 2220

Environmental

Considerations of

Active and

Abandoned

Mine Lands

Lessons from

Summitville, Colorado
Environmental Considerations of 

Active and Abandoned Mine Lands

Lessons from Summitville, Colorado

U.S. GEOLOGICAL SURVEY BULLETIN 2220

Edited by Trude V.V. King

With contributions from

Cathy M. Ager

William W. Atkinson

Laurie S. Balistrieri

Robert J. Bisdorf

Dana Bove

Roger N. Clark

Mark F. Coolbaugh

James A. Erdman

Larry P. Gough

John E. Gray

Paul von Guerard

Trude V.V. King

Fredrick E. Lichte

William R. Miller

Roderick F. Ortiz

Geoffrey S. Plumlee

W. Ian Ridley

Kathleen S. Smith

Gregg A. Swayze

Ronald R. Tidball

Katherine Walton-Day

Thomas M. Yanosky
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Gordon P. Eaton, Director

Any use of trade, product, or firm names in this publication is for descriptive pu

only and does not imply endorsement by the U. S. Government.

UNITED STATES GOVERNMENT PRINTING OFFICE: 1995

For sale by

U.S. Geological Survey

Information Services

Box 25286, Federal Center

Denver, CO 80225

Library of Congress Cataloging-in-Publication Data

Environmental considerations of active and abandoned mine lands : lessons from Summ

Colorado / compiled by Trude V.V. King with contributions from Cathy M. Ager . . . [

p. cm.—(U.S. Geological Survey bulletin : 2220)

Includes bibliographical references (p. ).

1. Gold mines and mining—Environmental aspects—Colorado—Summitville. 2. 

drainage—Environmental aspects—Colorado—Summitville. 3. Heap leaching—Env

aspects—Colorado—Summitville. 4. Reclamation of land—Colorado—Summitville

I. King, Trude V.V. II. Series.

QE75.B9 no. 2220

[TD195.G64]

363.73′84—dc20 

M A R C H 3, 18 4 9

U.S. DEPARTMENT OF THE INTERIOR
Introduction 2 CONTENTS

Acid Mine Drainage 4

Lessons from Summitville 6

Active Volcanoes Once Covered Southwestern Colorado 6

Gold in an Ancient Volcano 8

Mining of Gold and Formation of Acid Mine Drainage

at Summitville 10

Geophysics Plays a Role in Understanding

Acid Mine Drainage 14

Summitville from the Air 16

Water Transport—A Powerful Way to Move Metals 20

Revealing Groundwater Quality by Examining

Tree Rings 24

Pathways of Sediment and Water to the San Luis Valley 28

Imaging Spectroscopy—A Method for Mapping

Crop Distribution 30

Uptake of Elements by Alfalfa and Barley—Another

Way to Study Metal Dispersion 32

Biogeochemical Examination of the Alamosa

National Wildlife Refuge 34

Summary 35

Further Reading 36

Photo Credits 37

Frontispiece
2

etals and minerals are essential components of a highly industri

In the United States part of this demand has been met through 

mining of metals and minerals in almost every State of the Nation. Hi

when mines were no longer economic, individual mines or whole minin

were abandoned with little or no consideration for future environmenta

Current awareness has made the public more concerned about the effec

ing. The deleterious effect of historic mining activity is a national probl

are between 100,000 and 500,000 abandoned or inactive mine sites in t

States; a total of 26 States, predominantly in the West, have more tha

Environmental Protection Agency (EPA) Superfund restoration sites 

non-fuel mining activity. The Summitville mine site in Colorado is an e

what can go wrong.

From 1985 through 1992, the Summitville open-pit mine produced 

low-grade ore using cyanide heap-leach techniques, a method to ex

whereby the ore pile is sprayed with water containing cyanide, which dis

minute gold grains. Environmental problems at Summitville include 

increases in acidic and metal-rich drainage from the site, leakage of cya

ing solutions from the heap-leach pad into an underdrain system (designe

solutions containing gold and cyanide that leaked through the liner under 

and several surface leaks of cyanide-bearing solutions into the Wightm

the Alamosa River. The mine’s operator had ceased active mining and 

environmental remediation, including treatment of the heap-leach pile 

lation of a water-treatment facility, when it declared bankruptcy in Decem

and abandoned the mine site. The EPA immediately took over the Summ

under EPA Superfund Emergency Response authority. Summitville wa

the EPA National Priorities List in late May 1994. The total cost of the c

been estimated at $100 to $120 million. EPA’s remediation efforts inc

ment of cyanide solutions remaining in the heap-leach pad, detoxificat

heap, plugging of the Reynolds adit (a major source of acid- and metal-

age from the site), backfilling of the open pit with acid- and metal-genera

dump material, and capping of the backfilled pit to prevent water inflow

Summitville has focused nationwide attention on the environmenta

modern mineral-resource development. Soon after the mine was a

Federal, State, and local agencies, along with Alamosa River water 

Environmental

Considerations of

Active and

Abandoned

Mine Lands

Lessons from

Summitville,

Colorado

Superfund

The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), commonly

called Superfund, was passed into law in December

1980. It established a program to identify sites from

which releases of hazardous substances into the environment have or might occur, to provide for cleanup

by responsible parties or the government, to evaluate

natural resource damage, and to create procedures

for cost recovery related to cleanup activities. 

M
San Luis Valley

Summitville

mine

Approximate eastern

boundary of the

San Juan Mountains

Bitter Creek

Platoro

Monte Vista National

Wildlife Refuge

37 ̊

30'

37 ̊

00'

107 ̊00' 106 ̊30' 106 ̊00'

.

Iron Creek Alum Creek

Wightman Fork

Jasper

ALAMOSA RIVER

Terrace

Reservoir

Monte Vista RIO GRANDE

Alamosa

Alamosa National

Wildlife Refuge

Farmlands irrigated with

Alamosa River water

Capulin

La Jara Cre ek

COLORADO

0 10 20 KILOMETERS

private companies, began extensive

studies at the mine site and surrounding areas. These studies included

analysis of water, soil, livestock and

vegetation. The role of the U.S. Geological Survey (USGS) was to provide

geologic and hydrologic information

about the mine and surrounding area

and to describe and evaluate the environmental condition of the Summitville mine and the downstream

effects of the mine on the San Luis

Valley. The environmental condition

of the Summitville area is both a result

of the geologic evolution of this area

that culminated in the formation of

precious-metal mineral deposits and a

result of the mining activity. Understanding the geologic and hydrologic

history of this area is a critical part of

understanding the environmental

puzzle at Summitville.

Summitville mine area in the San Luis Valley of Colorado. 
4

ining activity occurs in areas

that have high concentrations of

economically important materials,

such as gold, silver, copper, cobalt,

iron, lead, and zinc. These areas may

also contain high concentrations of

noneconomic elements such as arsenic,

selenium, mercury, and sulfur, whose

presence is closely tied to the formation of the heavy metals. Many of

these economic and noneconomic elements can be hazardous if released into

the environment. Even without mining, mineralized areas can naturally

adversely affect the environment. 

A common process that results in

dispersion of elements from a mineralized site is acid drainage. When acid

drainage results from mining activity,

it is more specifically called acid mine

drainage. As the name implies, acid

mine drainage is the formation and

movement of highly acidic water rich

in heavy metals. This acidic water

forms principally through chemical

reaction of surface water (rainwater,

snowmelt, pond water) and shallow

subsurface water with rocks that contain sulfur-bearing minerals (mainly

pyrite), resulting in sulfu

Heavy metals can be leac

rocks that come in contact 

acid, a process that may be 

tially enhanced by bacterial a

resulting fluids may be hig

and when mixed with gro

surface water, and soil may h

ful effects on humans, an

plants.

Mining accentuates an

ates natural processes. The 

ment of underground worki

pits, ore piles, mill tailings, 

heaps and the extractive pro

ores enhance the likelihood 

ing chemical elements to the 

ing area in large amount

increased rates relative to 

areas. Studies describing 

extent and effect of acid drai

in unmined mineralized are

areas containing inactive a

doned mines are required if 

ronmental impact of heavy m

be understood. Studies in 

mineralized areas describe th

baseline chemical character

variations of the mineralized 

ACID MINE DRAINAGE M

 pH

All natural waters contain free hydronium (H3O+)

and hydroxyl (OH–) ions. Acidity is measured by the

concentration of hydrogen ions, called pH, which is

the negative logarithm of the hydrogen ion activity.

Neutral solutions have pH values of 7. If the pH is

greater than 7 the water is basic, and if the pH is less

than 7 the water is acid. Acids have a sour taste. For

example, vinegar (a strong acid) has a pH of about

4.6, whereas the pH of rainwater is about 6 (a weak

acid). The pH of acid mine drainage may be less than

2 but commonly is between 2 and 5.

Elements in Solution

Sulfuric acid in liquid form breaks down into hydronium ions (H3O+) and sulfate ions (SO2–4 ) and can

carry many metals in solution, as both simple and

complex ions. For example, copper can be transported in solution as simple copper ions (Cu2+) and deposited as copper sulfate (CuSO4); iron can be

transported as ferrous or ferric ions (Fe2+ or Fe3+)

and deposited as ferric hydroxide (Fe(OH)3). The variety of simple and complex ions in solution depends

in part on the pH of the solution, the amount of oxygen dissolved in the solution, and the concentrations

of the cations (positively charged ions) and anions

(negatively charged ions) in the solution.
6

he Summitville gold mine is in the San Juan Mountains of Colorado 

that was once covered with steep-sided volcanoes. These volcano

about 30 million years ago but have been partly destroyed by natural ero

ing behind remnants of volcanic debris. Summitville is part of a volca

summit collapsed, forming a caldera. After the caldera formed, lava erup

tinued at the surface and intrusions formed beneath the surface. At the s

rocks inside the volcano were exposed to hot, corrosive water produced b

canic system, a process called hydrothermal alteration.

The region around the Summitville mine is covered with creek

and intermediate size that drain into the Alamosa River and form the u

mosa River basin. The downward-cutting action of these creeks has ex

hydrothermally altered rocks and allowed geologists to examine thes

detail. Two main episodes of hydrothermal alteration occurred in the u

mosa River basin. The older period of alteration affected about 11 squa

ters of rock in the Iron, Alum, and Bitter Creek basins and a roughly 

area at Jasper. A younger period of alteration, corresponding to renew

thermal activity almost 8 million years later, affected about 3 square 

surrounding the Summitville mine area and led to the formation of 

metal mineral deposits. 

The Summitville mine, Iron, Alum, and Bitter Creek basins, and J

are all located on a zone of weakness in the Earth’s crust. During the pa

lion years, this zone was the focus of many cycles of magma intrusion, 

mal alteration, and mineral formation. The magma intrusions in the Ir

and Bitter Creek basins and in the Jasper area have been exposed by er

geologists have shown that the origins of the intrusions and the rock alte

closely connected. At Summitville, however, the intrusive body is not e

the surface because it is covered by almost 600 meters of younger lava

the geologic situation of the Iron, Alum, and Bitter Creek basins and 

area as an analogy, geologists assume that the buried intrusion at Sum

also closely tied to the rock alteration and mineral deposits observed at th

One of the strong similarities between the Summitville mining distr

Iron, Alum, and Bitter Creek basins is the presence of altered rocks that 

extremely corroded by sulfuric acid during hydrothermal alteration. Th

rock disintegration is known as acid-sulfate alteration. The hot fluids i

Alum, and Bitter Creek basins did not carry silver or gold in solution an

not produce an economic mineral deposit. In contrast, the fluids at Su

carried gold, silver, and copper. When these elements were deposited fro

ids, a precious-metal and base-metal mineral deposit formed. The contra

the Iron, Alum, and Bitter Creek basins and Jasper area and the Summi

ing area is very important. The former areas, as shown in the photo

undisturbed by mining or extensive exploration and can be used to charac

compare background sites adjacent to the Summitville mining area.

LESSONS FROM

SUMMITVILLE

ACTIVE VOLCANOES

ONCE COVERED

SOUTHWESTERN

COLORADO

T

Formation of Volcanoes

Heating in the Earth's interior results in melting of

previously formed rocks to produce magma. Magma

is less heavy than the surrounding rocks and moves

upward, pushing aside surrounding colder rocks or

moving through regions of pre-existing weakness. If

magma reaches the surface, it spills out and flows

across the land as lava flows or congeals near the

eruption site as a dome; if magma below the surface

is under enormous pressure, it can be violently blown

into the atmosphere as volcanic ash. Continued eruption in one area eventually builds a volcano fed from

underground stores of magma. Sudden eruption or

sideways movement of underground magma can

produce a subsurface void causing the volcano summit to collapse around a roughly circular depression

called a caldera. Some calderas are tens of kilometers

in diameter. During the building of such a volcano,

the magma can cool and solidify before reaching the

surface to form dikes (near-vertical, narrow sheets),

sills (near-horizontal, narrow sheets), or irregular

shaped masses beneath the volcano. As the magma

cools it discharges fluids (primarily water containing

various dissolved metals and salts) and gases and

also heats local groundwater, which begins to move

through the volcano. These fluids and gases can be

very corrosive and attack the surrounding rocks,

producing areas of hydrothermal alteration. Cooling

of the fluids and gases can precipitate new minerals,

including gold, silver, and sulfides, in sufficient

amounts to form a mineral deposit.
5

combining these baseline studies with

information from areas containing

inactive and abandoned mines, it is

possible to provide: 

An assessment of the intensity and

extent of environmental impact due to

acid mine drainage 

An understanding of natural processes to detect and predict where and

when acid mine drainage might occur

The production and consequences

of acid drainage involve the movement

of various chemical elements through

the environment as a result of physical,

chemical, and biological processes.

Collectively, these processes form the

biogeochemical cycle. 

Geology (the physical, structural,

and historical relations between rocks),

geochemistry (the chemistry of rocks

and their constituents), geophysics (the

physics of rocks and their constituents),

biochemistry (the chemistry of biological substances), and hydrology (the

properties, distribution, and effects of

water at the Earth’s surface and in the

subsurface) are the major scientific disciplines used to investigate the

biogeochemical cycle and, consequently, are used in a multidisciplinary

fashion to study acid mine drainage. 

USGS studies at the Summitville

mine in Colorado and adjacent parts of

the San Luis Valley used this integrated approach. Many of the environmental problems associated with

Summitville are the result of acid

mine drainage, and in this document

we describe studies that allow acid

drainage to be understood in more

detail. USGS activities at Summitville

were undertaken in part to provide

other Federal and State agencies with

data and interpretations and to develop

prototypes for future studies involving

inactive and abandoned mines. 

The Biogeochemical Cycle

Three principal ingredients make up the biogeochemical cycle. (1) Source of chemical elements

(where do they come from?). The source determines

how elements are physically and chemically distributed and to what extent they are available within

the cycle. (2) Transport mechanisms (how do elements move through the environment?). Commonly,

these mechanisms include water, wind, gravity, and

living organisms and are heavily influenced by

climate. (3) Sites (fate) of deposition (where and why

does transport stop?). For example, the elements

may be deposited as a part of the sediment in a reservoir or they may be taken up by a plant and perhaps become part of the food chain. Not all

deposition sites are permanent, and chemical

elements can be remobilized if physical or chemical

conditions change.
Background Sites

An assessment of the environmenta

ing at Summitville (or any mining f

related to areas that are undisturb

“How does the environment of a 

pare to what we might reasonably 

if there had been no human interf

information about an area prior to 

ence would serve this purpose; how

information is rarely available. In 

parison areas are chosen that are 

lar but have not experienced hum

The effect of human interference i

uated by simple statistical techniqu

parison, or background, site to pro
8

old mining at Summitville and

the minerals that produce acid

mine drainage are closely related to

each other. How did such a close relation develop? One way to answer this

question is to study modern volcanoes

that appear to be similar to ancient

volcanoes in the Summitville region.

For example, the unaltered rocks in

the Summitville region are very similar to rocks at Mount St. Helens in

Washington. The violent eruption of

Mount St. Helens in 1980 was accompanied by the growth of a volcanic

dome within the summit crater. This

dome represented the surface eruption

of very viscous (thick and sticky)

magma that had slowly risen through

the bowels of the volcano. During and

after the growth of the bulbous dome

at Mount St. Helens, large volumes of

acidic gas and water vapor poured

from the volcano summit as a result of

magma cooling within the volcano. 

Based on drilling inform

known that a similar dome li

the Summitville mine site

analogy to Mount St. Helen

describe the geologic evolutio

mitville in the following wa

magma beneath Summitville 

many dissolved gases, mai

dioxide (SO2) and hydroge

(H2S), water, and metals

magma cooled, the gases 

separated, each taking man

with them. The gases, being 

ascended quickly along fault

tures that cut through the volc

ing their rise, the magmatic 

water vapor combined to for

acid (H2SO4), which is hig

sive. The sulfuric acid dissolv

als in the surrounding rock

the rock porous, a process c

leaching. The metal-bearin

being heavier than the gase

upward at a slower pace but 

GOLD IN AN

ANCIENT VOLCANO G

Magma

Hydrothermal

fluids rich

in metals

Fault

Gold deposit Faults

Volcanic

dome 

Magma gases

H2S + SO2

Cross section of a volcano. Magma is below the volcanic dome, and magm

separating from the liquid magma.
the same complex of faults and fractures. Normally rocks are able to withstand severe attack by acid solutions

because they quickly neutralize the

waters, a process called acid buffering.

The quantity of acidic gases and

waters that attacked the rocks at Summitville must have been great because

the intensity of acid alteration is

extreme. These altered rocks no longer

have a natural acid-buffering capacity

and can no longer neutralize the fluids.

The ascending gases caused the rock

porosity (the volume of open space in

a rock relative to its total volume) and

permeability (the ability of a rock to

transmit fluid) to increase (by acid

leaching) and hence eased the upward

movement of the later fluids.

The most important metals in the

fluids were gold, silver, copper, iron,

lead, and arsenic, but the fluids also

contained abundant sulfur and salt.

The volcano probably had a welldeveloped groundwater table, and

mixing of rising hot, magmatic fluids

and cooler groundwater was inevitable.

Because of the vastly different temperatures and chemical compositions of

these mixtures and fluids, many metals

and compounds were deposited from

the solutions as solid minerals in fractures and pore spaces. This account fits

well with the common observation of

gold and iron pyrite, as well as copperand arsenic-bearing sulfur minerals

such as covellite (a copper ore mineral)

and enargite (a copper ore mineral containing arsenic), in the altered rocks at

Summitville.

As a result of these complicated

chemical processes, rocks that originally contained no gold were converted to highly altered ore rocks

containing large amounts of gold. It is

this gold ore that has been sought and

mined at Summitville since gold was

first discovered there in 1870. Equally

important from an environmental

standpoint, however, was the formation of metal sulfides, particularly

pyrite (FeS2), which are essential to

the generation of acid drainage. 
10

efore 1960, miners at Summitville dug many underground tunnels to remove

the high-grade gold ore concentrated along fractures and faults; however,

much of the gold was scattered in small amounts and in minute grains over large

areas of altered rock. Modern gold extraction technology made it possible to mine

rocks carrying this finely distributed gold. Within the last 10 years, large volumes

of ground were excavated to remove gold ore, forming a large open pit as shown

in the photograph to the left. Gold ore was placed in one pile, and rock that did not

contain gold was put into waste piles. To remove the gold, the ore pile was sprayed

with a mixture of water and cyanide, which dissolved the minute gold grains. Further chemical treatment of the cyanide solutions caused the gold to separate. The

gold was then collected, formed into bars, and sold. In 1992, mining ended at Summitville because most of the gold ore had been removed and the ore remaining was

unprofitable to mine. The large open pit was abandoned, and rocks in the ore pile

and waste piles remained in place.

Many of the rocks remaining in the rock piles, open pit, and underground tunnels contain sulfides, especially pyrite, that undergo chemical reactions when they

come into contact with air and rainwater at or below the ground surface. This process is called chemical weathering. During chemical weathering, air and rainwater

react with sulfide minerals such as pyrite, enargite, chalcopyrite, covellite, and

chalcocite and generate large amounts of sulfuric acid. The altered rocks, which

formed by an earlier episode of corrosion by sulfuric acid, as described previously,

cannot neutralize the acid formed by chemical weathering. The acid dissolves

many heavy metals present in ore and non-ore minerals to produce a fluid-acid

mine drainage. The Summitville mine drainage waters are among the most acidic

and metal bearing in Colorado; the drainage waters have a pH generally below 3

and contain high to extreme concentrations of iron, aluminum, copper, zinc,

arsenic, lead, and other metals. 

MINING OF GOLD AND

FORMATION OF

ACID MINE DRAINAGE AT

SUMMITVILLE

B
10,000

HEAVY METALS, IN PARTS PER MILLION

9

1,000

100

10

1

0.1

0.01

1 2 3 4 5 6 7 8

pH

Summitville mine

drainage compositions

Other Colorado mine

drainage compositions

Production of sulfuric acid by the reaction of pyrite with air.

pH and heavy-metal composition (zinc, copper, cadmium, lead, cobalt, and nickel) at

the Summitville mine site and other mine areas in Colorado.

Mine entrance

Reaction A 

 Tunnel

Reaction B 

Pyrite (FeS2)

Oxygen (O2)

Water (H2O)

Pyrite + Water + (Fe3+ or oxygen)

Reaction A 

Fe2+ + Sulfate + A

Reaction B 

Fe3+ + Water Iron hydroxides + A
12

As a result of mining activity, the content of copper and other metal

draining the Summitville pit via underground workings and the Reynold

nificantly increased from 1984 through 1993. During dry periods, acid m

evaporate from the underground mine workings, mine waste dumps, and 

rock around the open pit. As the waters evaporate, they leave behind 

metal-bearing salts such as chalcanthite, a copper sulfate mineral. These 

acid and metals in the solid form, and they are highly soluble and rediss

the next pulse of rainwater or snowmelt flows through the mine.

The resulting flush of these salts can lead to sharp, short-term in

acid and metals draining the site, such as the seasonal spike in dissolv

concentration in Reynolds adit outflow that coincides with spring sno

shown in the photograph on this page). Deep red puddles that are highly 

metal rich form soon after summer thundershowers (as shown in the ph

on the facing page). These puddles also reflect the dissolution of solu

salts in the pit rocks. Extensive remedial efforts will be required to is

unweathered sulfides and soluble metal salts in the open-pit area an

waste piles from weathering and dissolution.

Amount of copper in the Reynolds Tunnel outflow over time. Modified fr

Associates (1992).

12

Spring flush

COPPER, IN MILLIGRAMS PER LITER 

400

300

200

100

0

1984 1986 1988 1990 1992

END OF YEAR

14

ot all water in the Summitville

area moves along the ground surface. Some water flows beneath the

surface and may re-emerge in springs,

creeks, and rivers. How can we see the

geologic structures and movement of

fluids that are hidden from our direct

view? One important aid is the geophysical technique called electrical

resistivity. Rocks do not conduct electricity very well; they resist the flow of

electricity. The most resistive rocks

are dense (low-porosity) materials

such as granite, limestone, or some

crystalline volcanic rocks. Moderately

resistive material includes porous sand

and gravel that is saturated with potable water. Low resistivity commonly

indicates highly altered or fractured

rocks, rocks filled with nonpotable

water, or clay-rich rocks. 

measure the change in vol

voltage decrease is a reflect

resistivity of the rocks and f

subsurface and can be inte

terms of rock mineralogy, w

tent, and water quality. In a 

neous rock the current flows 

all directions; however, if t

not homogeneous the flow o

rent is modified, and diffe

resistivity can be mapped. C

tions can arise, however, if 

(cultural) materials are prese

affect the measurement of un

resistivity. For example, 

mitville, power lines, metal 

and debris, cables, and pipe li

detrimental to accurate meas

The Schlumberger soundin

has been developed to lessen 

types of cultural problems a

variations in resistivity. In th

computer models are develop

series of horizontal rock 

known resistivity and are co

the measured resistivities in 

determine the closest fit to 

This method was used to ma

surface in the Summitville m

GEOPHYSICS PLAYS

A ROLE IN

UNDERSTANDING

ACID MINE DRAINAGE

N

How can we make these resistivity measurements and interpret the

results? The basic technique is to

“shock” the underground rocks by

introducing an electric current of

known voltage at a specific point. The

current flows through the rocks, but

not very efficiently, and sensitive electrodes placed at several other locations
A number of individual soundings can be combined to create a resistivity

cross section. Cross sections, which can be thought of as vertical slices through

the ground similar to road cuts, are more easily interpreted than individual soundings and illustrate lateral as well as vertical variations of resistivity. For illustrative purposes in the figure showing a cross section through the heap-leach pile

(sounding 11), warm colors (orange-red) represent high resistivities, and cool

colors (blue-green) represent low resistivities. The cross section demonstrates

that the heap-leach pile (indicated by yellow and green) is located on the volcanic

andesite (an extrusive rock that formed when the magma from the volcano

flowed on the surface), which in turn lies upon some of the oldest rocks in the

area (commonly dense and nonporous rocks known as basement rocks) represented by the higher resistivities (pink and red colors). At soundings 15 and 17,

high resistivities indicate that the basement rocks are only 40 meters below the

surface and extend under the heap-leach pile to near sounding 14.

Downward movement of mine drainage through the subsurface is probably

hindered wherever the fluids encounter basement rocks; the mine drainage then

flows along the basement surface downhill to the Wightman Fork. The basement

rocks probably dip to the north, mimicking the topographic surface, and they

may represent an erosional surface that is buried beneath the younger volcanic

rocks. To the north (under sounding 12), in the suggested direction of fluid flow,

low-resistivity rocks are 20–30 meters below the surface and probably represent

clay-rich or water-saturated sediments. 

When evaluating the movement of acid mine drainage in the Summitville

mine area, we must understand the flow of fluids through both the surface and

subsurface because both types of flow influence the amount, direction, and quality of the discharge.

Geoelectrical cross section through the heap-leach pile at the Summitville mine. Triangles represent the surface locations 

soundings. 

18 12

7

15

14

NORTH

ELEVATION, IN METERS

3600

3500

3400

3300

3200

11

S

Heap

1,000700300200150100703020

0 100 200 300 METERS

OHM-METERS
16

emote sensing data of the Summitville mine site and adjacent a

collected using NASA’s Airborne Visible and Infrared Imaging S

ter (AVIRIS) system. 

The AVIRIS system is a NASA (National Aeronautics and Space 

tration) instrument onboard an aircraft flown at about 19,800 meters 

speeds of just less than mach 1 (the speed of sound). The data are collec

vide an image of the land surface across a swath about 11 kilometers w

The image is composed of many data points, called pixels. Each 

three-dimensional data point consisting of an X, Y, and Z component. E

represents a surface area (the X and Y components) of about 17 met

meters and contains information on the chemical and mineralogical ch

the material (the Z component). Spectra acquired by remote measure

interpreted by comparison with laboratory spectra from known samples

Imaging spectroscopy data of the Summitville mine and the Ir

and Bitter Creek basins were used to search for minerals associated w

ation. USGS scientists produced maps using the continuous spectral 

data to define the distribution of these mineral groups. Hydroxyl-bearin

als, including clays, show discrete distribution boundaries at both the 

and within the Iron, Alum, and Bitter Creek basins. 

SUMMITVILLE

FROM THE AIR

Remote Sensing

Most naturally occurring and manmade materials absorb sunlight at specific wavelengths. For example, it

is the absorption and scattering of the sunlight by

plants that produces the green color observed by the

human eye. Just as every human has a characteristic

thumb print, each mineral and manufactured material

has a unique spectral signature related to its chemical

composition, grain size, degree of crystallinity, and

temperature of formation. The spectral signature is a

measure of how reflected sunlight interacts with a surface. Spectral information can be gathered from laboratory measurements, or it can be remotely acquired

by aircraft or satellite systems, therefore providing a

powerful mapping tool.

224 spectra

Imaging spectroscopy data are acquired from an aircraft, in this study using the AVIRIS system of NASA. The aircra

data over a swath about 11 kilometers wide. The image is composed of a series of three-dimensional data points or pixels 

a 17-meter by 17-meter area on the surface (the X and Y directions) and acquire a solar reflectance spectrum in the Z d

R
17

Halloysite or kaolinite-smectite mixture

Potassium-rich alunite

Sodium-rich alunite

Poorly crystalline kaolinite

Highly crystalline kaolinite

Sodium-rich montmorillonite

Not mapped

AVIRIS image of the Summitville mine and adjacent area showing the distribution of

hydroxyl-bearing minerals. Image made September 3, 1993.
18

Perhaps the most interesting observation from the spectral data 

Summitville mine apparently does not contribute hydroxyl-bearing m

the Wightman Fork to the Alamosa River, in contrast to the mineralize

Iron, Alum, and Bitter Creek basins, which do. This observation is ba

spectral characteristics of the exposed fluvial sediments along Alum 

Bitter Creek and the lack of hydroxyl-bearing fluvial sediment along t

man Fork. The unmined mineralized areas are believed to contribute 

bearing materials to the Alamosa River because of the porous charac

well-exposed rock, which allows altered materials to be eroded e

deposited along the streambanks as sediment. If hydroxyl-bearing mat

associated contaminants, are being supplied to the Wightman Fork by 

mitville mine, the material must be carried as a very fine grained aqu

pension in the water, which cannot settle on the creek banks. 

Images show that both the Summitville mine and the Iron, Alum, 

Creek basins are sources of iron-bearing sediments to the Alamosa Ri

sediments give a reddish-brown color to streambanks, a characteristic 

associated with acid drainage, and are potential carriers of heavy meta

tions downstream. Consequently, in assessing the environmental impact 

at Summitville, it is an important observation that both the Summitville 

and the Iron, Alum, and Bitter Creek basins contribute this type of sedim

Alamosa River. 

Downstream from the Summitville mine, other creek drainages, inc

Jasper area, contribute hydroxyl-bearing and iron-bearing minerals to th

River. These river sediments are then carried into the Terrace Reservo

below), the source of irrigation water for some parts of the San Luis Va

18
Reynolds tunnel sludge

Iron hydroxide

Potassium-rich jarosite

Goethite

Sodium-rich jarosite

Ferrihydrite

Hematite

Not mapped 

AVIRIS image of the Summitville mine and adjacent area showing the distribution of

iron-bearing minerals. Image made September 3, 1993.
20

rainage from the Summitville mine comes from three sources—h

water, seeps that are present throughout the mine workings, and wat

from the old Reynolds adit. These waters move downslope into Wightm

small tributary of the Alamosa River, which in turn flows east for abou

meters and then enters the fertile agricultural lands of the San Luis V

increase in the trace metal burden of the Alamosa River watershed due 

activity at Summitville is of concern to farmers, fishermen, and Federal 

of Colorado agencies.

To investigate the influences of waters containing heavy metals o

rounding region, the USGS initiated a study of local and regional water 

Between April and September 1993, in the Alamosa River and the W

Fork, water samples were collected to determine their quality and water 

rates were measured. These data were used to evaluate the impact of 

mitville mine on water quality in the river basins and in Terrace Reserv

locate sources of acidic waters containing elevated concentrations of a

copper, iron, manganese, and zinc. 

Metal concentrations are higher and pH values lower (more acidic

immediately downstream from the Summitville mine site relative to wate

just upstream from the mine (the background site). This observation ind

WATER TRANSPORT—

A POWERFUL WAY TO

MOVE METALS

Water Quality

Water quality is determined by the amounts of suspended solid particles and dissolved substances. Federal and State agencies provide standards for water

quality based on whether the water will be used for (1)

recreation, (2) aquatic life, (3) agriculture, or (4) domestic supply. The standards are in the form of tables

of maximum allowable concentrations for a wide variety of elements and organic compounds.

Jasper

Summitville

1

Background

site 50:15

10

100

1000

10,000

DISSOLVED ALUMINUM IN WATERS,

IN PARTS PER BILLION

April 21–23

June 2–4

Iron Creek

Alum Creek

Bitter Creek

Wightman Fork 

Burnt Creek

Jasper Creek

Estimated extent of

rainstorm on

August 9–10, 1993

Terrace

Reservoir

Concentration of dissolved aluminum along the Alamosa River during April and June 1993. The 

extent of the rainstorm discussed on page 21 is also shown.

D
acidic, metal-rich water may enter the

Wightman Fork in its headwater region

upstream from either where the background stream enters the Wightman

Fork or where it crosses the mine site.

There is some input of metals and low

pH water to the Alamosa River

upstream from the Wightman Fork during the first part of spring snowmelt

runoff (April through May). Numerous

small tributaries upstream from the

Wightman Fork contribute acid water

to the Alamosa River at this time. Many

of these tributaries stop flowing when

snowmelt ends. During the late April

sampling trip, concentrations of dissolved aluminum were greater

upstream from the Wightman Fork than

in the Wightman Fork. During all other

sampling trips, concentrations of dissolved aluminum were lower upstream

than in the Wightman Fork. Data for

iron concentrations show a similar

trend. Therefore, during early snowmelt in April, sources upstream from

the Wightman Fork are the primary

cause of elevated aluminum and iron

concentrations in the Alamosa River. 

By measuring both the total concentration of an element carried in

water and the water flow rate, it is a

simple matter to calculate the amount

of an element transported during a

fixed-time interval. This calculation

was performed for the Wightman Fork

and the Alamosa River upstream from

the Wightman Fork for eight fixedtime periods. Ratios of the amount of

metal in water from the Wightman

Fork to the amount of metal in the Alamosa River are shown in the table on

the following page. Values greater than

1 indicate that Wightman Fork is the

major contributor of that metal to the

Alamosa River. Values less than 1 indicate that sources other than and

upstream from the Wightman Fork are

the major contributors of that metal to

the Alamosa River. The Wightman

Fork is the source of most of the copper, manganese, and zinc discharged

into the Alamosa River and Terrace

Reservoir during all sampling periods

and is the primary source of aluminum

and iron during the latter parts of spring

1

pH

Iron

Creek

KILOMETERS UPSTREAM FROM RIO GRANDE

(not to scale) 

83

3

5

7

9

80 79 77 72 68 56

Alum

Creek

Bitter

Creek

Wightman

Fork

Jasper

Creek

Burnt

Creek

Alamosa River

upstream from

Terrace Reservoir

pH of inflows along the north side of the Alamosa River, May 6, 1993. Station locations

are measured from the confluence of the Alamosa and the Rio Grande Rivers in the

San Luis Valley. 
22

Ratio of total amount of metal in the Wightman Fork at its mouth to tota

of metal in the Alamosa River above Wightman Fork

[A ratio of more than 1 indicates that the Wightman Fork supplies most of the metal to th

River, and a ratio of less than 1 indicates that areas upstream from the Wightman Fork s

of the metal to the Alamosa River]

Date Aluminum Iron Copper Manganese 

April 21–23, 1993 0.24 0.10 16 1.1 

May 4–6, 1993 0.27 0.15 7 1.3 

May 18–20, 1993 1.3 0.85 47 4.1 

June 2–4, 1993 3.0 2.8 230 6.4 

June 21–23, 1993 1.7 2.4 340 4.6 

July 12–14, 1993 2.0 1.9 330 4.6 

August 8–10, 1993 1.1 0.39 62 3.6 

September 7–8, 1993 0.71 0.36 53 3.2 

1The amount of total recoverable zinc in the Alamosa River above Wightman Fork is 

detection limit of 10 micrograms per liter.

ALUMINUM COPPER IRON MOLYBDENUM Z

CONCENTRATION OF DISSOLVED METALS,

IN MILLIGRAMS PER LITER

0.001

0.01

0.1

1

10

Before s

After st

Concentrations of dissolved metals in the Alamosa River upstream from Te

ervoir before and after a rainstorm, August 10, 1993. The geographic ex

rainstorm is shown on page 20.

22

?
runoff and into July and August.

Sources upstream from the Wightman

Fork supplied most of the iron and aluminum to the Alamosa River in April,

early May, and September. 

A few tributaries downstream

from the Wightman Fork, including

Burnt Creek, contribute acidic, metalbearing water to the Alamosa River

during the early part of snowmelt runoff. This observation was confirmed in

an unusual manner during August

1993. Samples were collected in the

Alamosa River directly upstream from

Terrace Reservoir before and after a

rainstorm that soaked an area downstream from, but not including, the

Wightman Fork drainage basin. Runoff from the storm had two important

effects. First, water flow rate in the

Alamosa River increased by a factor of

three. Second, concentrations of some

metals in the Alamosa River upstream

from Terrace Reservoir increased as

many as 400 times. 

Sources of acidic, metal-rich

water to the Alamosa River include (1)

areas that have been disturbed by mining, such as Summitville, and (2) areas

that have had minimal mining activity

but where the rocks are hydrothermally altered, such as Iron, Alum, and

Bitter Creeks, upstream from the

Wightman Fork and Burnt Creek, and

downstream from the Wightman Fork.

Many natural sources of acidic water

were identified in these altered areas. 

?

?
24

ree rings are used by geologists to

examine past environments. They

are particularly useful because each

ring represents one year of growth, preserving evidence of past conditions.

Counting rings from the outside toward

the tree center allows the researcher to

move precisely backward in time.

Nutrients provided by the root system

are required by a tree in order to promote ring growth. The roots excrete

acids that then dissolve metals in the

soil, making them available for uptake

by the tree. These metals eventually are

deposited within the growing tree. Consequently, small changes in soil chemistry can be seen by examining the

metal concentrations in tree rings, and

these changes can be precisely dated. 

The use of plants in 

environmental metal contami

a long history. In the middle o

century, the association w

between overall air quality 

industrialized European citie

presence or absence of speci

of tree lichens and mosses. 

lichen and mosses are c

absorbing large quantities 

and recently the USGS has us

establish baseline levels for 

plant tissues. These plants 

been used to map regions 

metal concentrations associ

contaminants emitted into 

sphere from specific point so

as smokestacks of power-g

stations or mine sites.

REVEALING

GROUNDWATER

QUALITY BY

EXAMINING

TREE RINGS

T

Metals in solution

in ground water

Metals in so

in surface w

Tree core showing annual rings

1986

Summitville mining

began

1992

Summitville mining

ended

Bark

Metal levels in individual annual rings of cottonwood can be examined for 

between years (pre-mining versus post-mining) or between the same year b

ous distances from the Summitville mine. The latter is an indirect measure 

ciency of metal transport in the Alamosa River system.
Tree-ring studies are useful, but

the chemistry of tree rings can be difficult to interpret. First, there may be

differences in metal concentrations

around the perimeter of a single tree

ring. Second, metals may move

between rings, particularly if there are

initially large differences in concentrations between adjacent rings. Third,

narrow tree rings, representing a slow

growth rate, make ring-counting more

difficult and add errors to the dating.

Fourth, distinguishing between local

and distant metal sources is difficult.

Despite these problems, tree rings

have been used successfully to document changes in groundwater chemistry down gradient from point sources

of metal contamination. 

Near Summitville, in the Alamosa River basin, the USGS analyzed

individual tree rings from narrow-leaf

Tree-ring sampling sites along the Alamosa River.

C D

B E

F

G

H

I J K

Summitville

mine

Platoro

37 ̊

30'

37 ̊

00'

107 ̊00' 106 ̊30' 106 ̊00'

. Jasper

ALAMOSA RIV

Terrace ER

Reservoir

Monte Vista

RIO

GRANDE

Alamosa

Capulin

La Jara Cre ek

0 10 20 KILOMETERS

SAN JUAN

MOUNTAINS

COLORADO

SAN

LUIS

VALLEY
26

1960

Sit

Site G

Site F

Site E

CONCENTRATION, IN MICROGRAMS PER GRAM

0

10

20

30

40

50

60

1970 1980 1986 1990

YEAR

Zinc concentrations in cottonwood tree rings downstream from the Summitville mine along the Alamosa River. Sci

examine differences within a single tree over time, as well as differences between sites for specific years.

cottonwood (Populus angustifolia) and aspen (Populus tremuloides). B

of trees produce annual growth rings that can be precisely dated. Sm

were drilled from the outside toward the center of each tree and ext

analysis. Individual tree rings were analyzed using a new analytical ins

laser-ablation inductively coupled plasma mass spectrometer (LA-ICP-

Both copper and zinc, heavy metals that are environmentally h

were detected in the rings of the tree samples. Both metals are most ab

older tree-ring tissue formed prior to mining activity at Summitville. 

amount of copper and zinc available to the tree roots has decreased 

years. This distribution may be due to an absolute decrease in levels 

and zinc in the soils; however, high concentrations of copper in ground

duce toxicity in tree roots, retarding metal uptake. Consequently, the d

copper and zinc in the tree rings may reflect toxicity as a result of incre

per and zinc levels in the soil. More study is required to distinguish 

these competing interpretations. 

26
Molybdenum, an element associated with the Summitville mineralization, was also detected in the tree

rings. The data for molybdenum suggest that its presence in the tree rings

decreases as the distance from the

Summitville mine increases; however,

the amount of molybdenum observed

does not change on a yearly basis.

There was, however, an increased

uptake at site K, possibly due to oxygenated, saline soil conditions that

favor molybdenum uptake by plants.

Bromine is also more abundant in the

older tissue relative to the newer tissue but does not decrease in abundance as a function of distance from

the Summitville mine.

Tree-Ring Chemistry

Laser-ablation inductively coupled 

trometer (LA-ICP-MS) has the cap

ing the concentrations of about 5

rings at the parts per billion level in 

that has a diameter as small as a p

ring core is viewed through a micro

ual rings are burned by a fine laser 

ing gaseous plasma is then h

concentrations are measured usin

mass spectrometer.
28

cidic, metal-bearing surface

water and sediment carried down

the Alamosa River enters Terrace Reservoir. From Terrace Reservoir, the

Alamosa River runs east through the

Alamosa National Wildlife Refuge.

Because the San Luis Valley is a major

agricultural center for Colorado, analyzing the effects of these waters and

sediments on crops and livestock is of

particular concern to local farmers and

agricultural industries. Similar concerns are also relevant to the Alamosa

Wildlife Refuge, a sanctuary for

migrating birds including sandhill and

whooping cranes. 

Weathering breaks rocks into particles and dissolved forms that are

readily transported. Streams, the most

common mode of transport, are the

most effective way to move sediment,

especially near their headwaters where

they move fastest. Material is transported downstream until the carrying

capacity of the stream diminishes, the

water slows down, and solid particles

are deposited to form sediments. Some

sediments form directly in the streambed, whereas others are deposited

over the streambank as a result of

flooding. After floodwaters recede,

these overbank sediments are further

weathered to form soils. Thus, the particular mixture of minerals in the soil

reflects the mineralogy of the source

rocks and imparts a geochemical fingerprint to the soil. Where the source

rocks have a geochemicall

signature, such as in an area 

deposits are present, the sig

the soil commonly is similar 

the ore deposits.

Examination of the r

streams that flow into the 

Valley indicates that the maj

of sediment are the Sangre 

Range, the Sawatch Range, a

Juan Mountains. Most of the 

results from the weathering a

of volcanic rocks. These so

also include a number of ore 

some of which have been m

therefore it might be expecte

iments enriched in heavy m

also carried into the San Lu

and become part of the soil. 

analysis of soils collected by 

in this region in 1993 indicate

major mining districts, Su

and Bonanza, contribute met

sediment to the San Luis Va

The Bonanza mining district 

sediment into the northern p

valley. Sediment is carrie

southern part of the San Lu

floor via numerous streams, 

the Wightman Fork, the 

River, and the Rio Grande R

Rio Grande River does not c

ment derived from the Su

mine or directly adjace

whereas the Wightman For

Alamosa River do.

PATHWAYS OF SEDIMENT

AND WATER TO THE

SAN LUIS VALLEY

A

Rock Weathering

How long does a rock last? The primary mechanism

of erosion is weathering. The severity of weathering

depends on climate, original rock composition, and

time. Given sufficient time, climate is the dominant

factor. Weathering is a twofold process. Mechanical

weathering, the shattering of rocks, results from the

physical action of water, ice, wind, and gravity, which

causes rocks to fragment. Chemical weathering, the

chemical decomposition of rocks, results from the

corrosive action of water, which causes parts of the

rock to be dissolved.

The Sawatch Range and the Bonanza mine contribute sediments contain

to the northern part of the San Luis Valley, and the Rio Grande and Alam

carry sediments to the southern part of the valley. 

30

pectral imaging of minerals from

aircraft was described previously, and this technique is also

extremely useful in examining crop

distribution. Just as minerals have

unique spectral signatures, so do

plants, trees, and soils. Laboratory

spectral investigations of plants have

shown that species can be identified

using their visible and near-infrared

spectra. The primary spectral features

used for identification result from the

presence of chlorophyll in plants, the

organic material that gives plants a

green color.

Details of the relation between

chlorophyll in plants and their individual spectra are still poorly understood. Although the spectra of plants

are sufficiently different to allow

species identification, the spectra for

an individual species can vary. Variations in plant spectra probably result

from the amount of chlorophyll in the

plant, a complex relation between the

stages of the growing cycle and the

health of the plant. The health of a

plant can be affected by many factors

including the amount of water it has

available (too much or too little) or

metal toxicity. Using AVIRIS data,

maps were made of the distribution of

IMAGING

SPECTROSCOPY—

A METHOD FOR MAPPING

CROP DISTRIBUTION

S crops, relative amounts of dry versus

green vegetation, and relative health

of specific crops in the lower San

Luis Valley

Farmers in the San Luis Valley

rely heavily on irrigation waters

applied by center-pivot irrigation systems; thus, most farmed lands appear

as circular areas in the remotely

sensed data. Pasture land, fallow

fields, and public lands not being used

for agricultural purposes are usually

not irrigated and do not appear as circular areas in the images. A number of

crops, including alfalfa, canola, barley, hay, oats, potatoes, and spinach,

were successfully mapped. Subtle but

significant differences in the reflectance spectra of potatoes allowed the

mapping of three different species.

Pasture lands and areas of mixed

green and dried vegetation were also

mapped, providing a method to analyze crop distribution over large areas.

Such methods are useful to land management agencies to inventory and

assess land usage; however, more rigorous and thorough testing is required

to determine the full capabilities and

application of airborne imaging spectroscopy to agricultural problems. 
Alfalfa

Canola

Barley

Potato

Oat hay

Spinach

Chico/pasture

Not mapped

AVIRIS image of the distribution of crops in the San Luis Valley, September 3, 1993.

The circular patterns are the result of center-pivot sprinkling systems. Each of the colors corresponds to a specific crop. In areas that are black, no crops were mapped.
32

errace Reservoir receives water from the Summitville mine and su

areas and provides irrigation water to the southwestern part of the 

Valley. The composition of water and stream sediment from the Wight

and the Alamosa River suggests that arsenic, chromium, copper, lead, nic

ganese, and zinc are likely components of water being drawn from Terra

voir. USGS scientists undertook two studies to determine the effec

irrigation water on metal concentrations in alfalfa (a perennial crop) and 

annual crop) and their associated soils. 

Two sources of irrigation water were examined and compared f

fields of similar soil types in center-pivot irrigated alfalfa and barley f

sources for the irrigation water were the Alamosa River (terrace fields) a

Grande River and confined groundwater (control fields). The Alam

receives acidic metal-rich drainage, whereas the Rio Grande River and 

groundwater are uncontaminated.

A comparison of copper, manganese, and zinc concentrations 

two water sources indicates that water from the Alamosa River is m

(pH 5.6–6.8) than irrigation waters from the Rio Grande River or 

groundwater (pH 7.6–9.2) and contains much higher concentrations 

metals. Because the two sources of irrigation water have such differen

sitions, the question that needs to be addressed is are these differe

present in the crops and soils? Our studies suggest that the answer is no

Comparison of the metal-concentration ranges for the soils irrigat

ferent water sources shows that copper, manganese, and zinc concent

the soils are generally similar. Comparison of these concentration ra

those for soils collected throughout the Western United States indicate

concentration ranges of the soils, regardless of the source of irrigation 

within expected ranges.

Comparison of the copper concentrations in alfalfa and barley irr

different sources shows that copper concentrations of the crop in the 

gated with Alamosa River water are higher than those for fields irrigated 

Grande River water or confined groundwater. Concentration ranges are 

ble, however, to those reported in other studies for different location

results were obtained for nickel.

UPTAKE OF ELEMENTS BY

ALFALFA AND BARLEY—

ANOTHER WAY TO STUDY

METAL DISPERSION

T
If nutritional requirements for cattle are considered, alfalfa irrigated with both sources of water meets published nu

requirements and contains amounts of metals far below concentrations reported to be toxic to cattle. Interestingly, the 

copper concentrations in alfalfa grown in fields irrigated with Alamosa River water are commonly in the sufficient ra

nutrient status, whereas alfalfa grown in fields irrigated with Rio Grande River water or confined groundwater extend

the low range of nutrient status. Similar results were obtained for manganese and zinc.

Thus, although concentrations of many metals in irrigation water affected by the Summitville mine are higher t

other local irrigation-water sources, these metal-rich irrigation waters have only a slight effect on the bulk soil compo

and a minimal effect on the metal content of the crops. None of the metal values in alfalfa is near toxic levels, and some 

levels can be considered somewhat beneficial to the nutritional value for alfalfa.

1

n = 24

Mean

n = 24

10 +/-

n = 49

n = 112

n = 129

San Luis Valley, Colo.

Terrace fields*

Control fields*

San Joaquin Valley, Calif.

Casper, Wyo.

Uncompahgre River Valley, Colo.

Dietary requirement for cattle

Possible toxic level in cattle

115

10 100 

CONCENTRATION IN DRY MATTER,

IN PARTS PER MILLION *Differences significant at the

95 percent confidence level

San Luis Valley, Colo.

Terrace fields*

Control fields*

Reported in literature

Mean

2 4 6 8 10 1

CONCENTRATION IN DRY MATTER,

IN PARTS PER MILLION *Differences significant at the

99 percent confidence level

COPPER IN ALFALFA

COPPER IN BARLEY

Copper concentrations in alfalfa and barley for the different irrigation sources in the study area compared to copper concentr

in alfalfa and barley determined during other studies reported in the literature. For both alfalfa and barley, the copper conc

tions of the crops in the fields irrigated with Alamosa River water (terrace fields) are greater than those for fields irrigated w

Grande River water or confined groundwater (control fields); however, the ranges of concentrations are comparable to th

ported in the literature for other locations in the Western United States.
34

o examine the nature and extent

of the effects of acid drainage on

the biogeochemistry of wetlands in the

San Luis Valley, the USGS initiated a

study of the Alamosa National Wildlife Refuge (shown below). Water and

stream sediments were collected in

June 1993 from the Wightman Fork

and from 10 sites along the Alamosa

River. In addition, water, sediment

cores, and aquatic plants (Polegonum

amphibia) were collected from nine

wetlands just west of and within the

Alamosa National Wildlife Refuge.

The sources of water entering the wetlands include the Alamosa River, or a

mixture of La Jara Creek and Alamosa

River water, and the Rio Grande River.

1993. The concentration o

decreases as the waters flo

and along the valley floor. 

some indication that the lev

per remains above the base

in the wildlife refuge. 

Analysis of sediments 

above and below the conflue

Wightman Fork and the Alam

suggests that copper levels 

enced by drainage from the W

Fork and the tributaries draini

per area. The presence of am

iron-enriched particles in the 

downstream dilution of disso

concentrations, and the do

enrichment of metals in sed

consistent with the depositio

elements from the water, thei

in the solid phase, and settling 

water velocity decreases.

The waters in the wetl

high pH values, in contrast 

pH values for acid drainage

erally contain low concent

heavy metals. A compariso

ment samples from the Alam

and Rio Grande River sho

ever, that the accumulation 

cobalt, chromium, copper

vanadium, and zinc is grea

part of the wetland that rece

from the Alamosa River. O

ments, such as arsenic, ce

lead, show no significant en

that can be attributed to diff

the source of water and 

Studies of aquatic plants in 

lands show that plants recei

mosa River water contain mo

and zinc than plants that rec

from other sources. Thus, c

ments associated with acid 

from both mined and unmi

are being introduced into the 

Further, the chemical comp

the wetlands near and within 

mosa National Wildlife R

dependent in large part on t

of the water.

BIOGEOCHEMICAL

EXAMINATION OF THE

ALAMOSA NATIONAL

WILDLIFE REFUGE

T

Data for sediment and water

samples collected in the Alamosa

River suggest that both the

Summitville mine and the unmined

mineralized areas are sources of

copper. Using data collected

upstream from the confluence of the

Wightman Fork and the Alamosa

River as baseline level, the study suggests that dissolved copper was introduced into the Alamosa River by the

Wightman Fork waters during June
esults of USGS research at the Summitville mine site in Colorado underscore

the crucial need for sound scientific information in predicting, assessing, and

remediating the environmental effects of mining. Although final scientific judgments about Summitville and its downstream environmental effects await the outcome of all of the research, some preliminary conclusions can be drawn. 

Extreme acid-rock drainage is the dominant long-term environmental concern

at the Summitville mine and could have been predicted given the geologic characteristics of the deposit. Extensive remedial efforts are required to isolate both

unweathered sulfides and soluble metal salts in the open-pit area and mine-waste

piles from weathering and dissolution. 

It is likely that natural contamination adversely affected water quality and

fish habitat in the Alamosa River long before mining and will continue to have

adverse effects even when acid drainage from Summitville is remediated. Thus,

reasonable natural conditions for the Alamosa River basin must be established in

order to set realistic remediation standards for the Summitville site.

Results of studies as of late 1993 indicate that mining at Summitville has had

no discernible short-term adverse effects on barley or alfalfa crops irrigated with

Alamosa River water. Remediation of the site will help to ensure that no adverse

effects occur over the longer term.

R

SUMMARY
36

Bove, D.J., Preliminary report on the geology of hydrothermally altered areas

within the upper Alamosa River Basin,

Colorado: U.S. Geological Survey

Open-File Report 94–224, 12 p.

Clark, R.N., Swayze, G.A., Gallagher, A.J.,

King, T.V.V., and Calvin, W.M., 1993,

The U.S. Geological Survey Digital

Spectral Library, version 1—0.2 to 3.0

mm: U.S. Geological Survey OpenFile Report 93–592, 1,326 p.

Erdman, J.E., and Smith, K.S., 1993,

Impact of the Summitville Mine on

irrigation water, agricultural soils, and

alfalfa in the southwestern San Luis

Valley, Colorado: U.S. Geological

Survey Open-File Report 93–616, 4 p.

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FURTHER READING
PHOTO CREDITS

Edited by Judith Stoeser and Ca

Graphics by Carol Quesenberry

Mari Kauffmann, Shawn T

and Richard P. Walker

Photocomposition by Carol Que

Book design by Carol Quesenbe

On-line version by Joan Nadeau

Cover: Alamosa River near the Summitville mine, July 1994. Photograph by Geoff Plumlee

Page iii: Alum Creek basin near the Summitville mine, September 1994. Photograph by

Larry Gough.

Page iv: Ore chute at the old Summitville mine, 1975. Photograph by Chuck Beverly,

ASARCO; reproduced with permission from the Denver Museum of Natural History.

Page 1: Aerial view of the Summitville mine, August 1994. Photograph by IntraSearch;

reproduced with permission

Page 2: Old Summitville mine site, October 1975. Reproduced with permission from the

Denver Museum of Natural History 

Page 3: Terrace Reservoir on the Alamosa River downstream from the Wightman Fork, September 1994. Photograph by Larry Gough.

Page 4: Monte Vista National Wildlife Refuge in the San Luis Valley, April 1993.

Photograph by Larry Gough.

Page 5: Drainage water coming from the Cropsy dump at the Summitville mine, October

1990. Photograph by Geoff Plumlee.

Page 7 (top): South Mountain and Little Annie mining camp, Summitville area, circa 1873.

From “Statistics of mines and mining in the States and Territories west of the Rocky

Mountains,” U.S. Treasury Department, 1877.

Page 7 (bottom): Unmined, mineralized area, Alum Creek basin, September 1994.

Photograph by Larry Gough.

Page 8: Unmined, mineralized area, Alum Creek basin, September 1994. Photograph by

Larry Gough.

Page 9 (top): Unmined, mineralized area, Alum Creek basin, September 1994. Photograph

by Larry Gough.

Page 9 (bottom): Aerial view of the Summitville mine, August 1994. Photograph by

IntraSearch; reproduced with permission.

Page 10 (top): Miners in underground mine, circa 1900. Photograph by Mark Coolbaugh.

Page 10 (bottom): Aerial view of the Summitville mine, 1991. Photograph by IntraSearch;

reproduced with permission.

Page 12: Heavy metals coloring the water draining from the Reynolds tunnel at the

Summitville mine, June 1993. Photograph by Walt Ficklin.

Page 13 (left): Dark-red metal-rich puddles at the Summitville mine, August 1993.

Photograph by Geoff Plumlee.

Page 13 (right): Drainage from the Pass-Me-By mine, Iron Creek, south of the Summitville

mine, October 1991. Photograph by Geoff Plumlee.

Page 14 (top): Unmined, mineralized area, Alum Creek basin, September 1994. Photograph

by Larry Gough.

Page 14 (bottom): Geologist working in the Alum Creek area, September 1994. Photograph

by Larry Gough.

Page 17: Summitville mine, October 1990. Photograph by Geoff Plumlee.

Page 18 (top): Summitville mine, June 1993. Photograph by Geoff Plumlee.

Page 18 (bottom): Terrace Reservoir on the Alamosa River downstream from the

Wightman Fork, June 1993. Photograph by Geoff Plumlee.

Page 19 (top): Part of the gold boulder of Summitville; weight 132 troy pounds, estimated

to contain 26.4 troy pounds of gold. On display at the Denver Museum of Natural

History; reproduced with permission.

Page 19 (bottom): The gold boulder of Summitville, found October 3, 1975, by Bob

Ellithorpe of Del Norte, Colorado. Donated to the Denver Museum of Natural History.

Photograph by Ron Pochon, ASARCO; reproduced with permission from the Denver

Museum of Natural History.

Page 21: Natural iron bog in unmined, mineralized area on the Alamosa River above the

confluence with the Wightman Fork, 1991. Photograph by Geoff Plumlee.

Page 22: Unmined, mineralized area, Alum Creek basin, September 1994. Photograph by

Larry Gough.
38

Page 23 (top): Alamosa River below the confluence with the Wightman Fork

Terrace Reservoir, September 1994. Photograph by Larry Gough.

Page 23 (bottom left): Terrace Reservoir on the Alamosa River downstream 

Wightman Fork, September 1994. Photograph by Larry Gough.

Page 23 (bottom right): Sign along the bank of Alum Creek, June 1993. Pho

Larry Gough.

Page 24: Collecting samples in the Alamosa National Wildlife Refuge in th

Valley, June 1993. Photograph by Larry Gough.

Page 25: Unmined, mineralized area, Alum Creek basin, September 1994. Pho

Larry Gough.

Page 27 (top): Alamosa River below the confluence with the Wightman Fork

Terrace Reservoir, September 1994. Photograph by Larry Gough.

Page 27 (bottom): Alum Creek basin, September 1994. Photograph by Larry G

Page 30: Old Terrace Main Canal in the San Luis Valley, August 1993. Pho

Geoff Plumlee.

Page 32 (left): Collecting alfalfa samples in the San Luis Valley, June 1993. Pho

Kathy Smith.

Page 32 (right): Data acquisition in an alfalfa field in the San Luis Valley, 

Photograph by Jim Erdman.

Page 34: Alamosa National Wildlife Refuge in the San Luis Valley, June 1993. 

by Larry Gough.

Page 35: Open pit at the Summitville mine, August 1993. Photograph by Geoff 

Page 36: Ore chute at the old Summitville mine site, October 1975. Repro

permission from the Denver Museum of Natural History.

Page 38: Aerial view of the Summitville mine, August 1994. Photograph by I

reproduced with permission.

38