Effects of the May Day Mine Site on 

Stream-Water Quality in the Cement Creek 

Basin, August 2000

By Winfield G. Wright, Briant A. Kimball, and Robert L. Runkel

Chapter E23 of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Animas River Watershed, San Juan County, Colorado

Edited by Stanley E. Church, Paul von Guerard, and Susan E. Finger

Professional Paper 1651

U.S. Department of the Interior

U.S. Geological Survey
Contents

Abstract .......................................................................................................................................................947

Introduction.................................................................................................................................................947

Study Area Description ....................................................................................................................949

Purpose and Scope ..........................................................................................................................949

Acknowledgments ............................................................................................................................949

Methods of Study .......................................................................................................................................952

Stream Tracer-Injection Study........................................................................................................952

Quantification of Constituent Concentrations and Loads ..........................................................953

Evaluation of Sources ......................................................................................................................954

Effects of the May Day Mine Site on Stream-Water Quality ..............................................................954

pH and Constituent Concentrations ...............................................................................................956

Constituent Loads .............................................................................................................................957

Constituent Attenuation ...................................................................................................................961

Evaluation of Water Sources ..........................................................................................................964

Mineral Saturation ............................................................................................................................968

Summary and Conclusions .......................................................................................................................970

References Cited........................................................................................................................................970

Figures

 1. Map showing location of May Day mine site in Cement Creek basin 

of Animas River watershed .....................................................................................................948

 2. Map showing location of study reach, sample sites, and reach distances 

referenced to study of Kimball and others (2002) ................................................................950

 3. Sketch map showing study reach affected by May Day mine site ..................................951

 4–17. Graphs showing:

 4. Bromide concentrations at fixed sites illustrating plateau conditions .....................952

 5. Longitudinal stream profile of discharges in the study reach ...................................953

 6. Longitudinal stream profile of pH in Cement Creek through study 

 reach and pH values of inflows and tributaries ...........................................................956

 7. Longitudinal stream profiles of dissolved and total constituent 

 concentrations in study reach, for aluminum, copper, and iron ................................958

 8. Longitudinal stream profiles of dissolved and total constituent 

 concentrations in study reach, for manganese, sulfate, and zinc ............................959

 9. Longitudinal stream profiles of constituent loads in study reach, for 

 aluminum, copper, and iron .............................................................................................960

 10. Longitudinal stream profiles of constituent loads in study reach for 

 manganese, sulfate, and zinc ..........................................................................................962

 11. Longitudinal stream profiles of change in dissolved and total iron 

 loads in study reach ..........................................................................................................963
 12. Longitudinal stream profile of change in dissolved sulfate loads 

 in study reach .....................................................................................................................964

 13. Longitudinal stream profiles of change in dissolved and total zinc loads 

 in study reach .....................................................................................................................965

 14. Oxygen and hydrogen isotopes of water samples collected from study 

 reach and from selected springs, streams, and inactive mines as part 

 of other studies in Animas River watershed study area .............................................966

 15. Oxygen and hydrogen isotopes of water and dissolved zinc concentrations 

 for sites affecting May Day reach ..................................................................................967

 16. Principal components analysis, including dissolved constituents and 

 isotopes, showing groups of inflows and stream sites in study reach 

 affected by May Day mine ...............................................................................................968

 17. Longitudinal stream profile of saturation index for selected mineral 

 species in water samples from study reach .................................................................969

Table

 1. Sites where water-quality samples were collected in the tracer study reach, 

August 17, 2000 ..........................................................................................................................955

Conversion Factors, Abbreviations, and Acronyms

Multiply By To obtain

meter (m) 3.281 foot (ft)

liter per second (L/s) 0.03532 cubic foot per second (ft3

/s)

cubic meter per second (m3

/s) 35.3 cubic foot per second (ft3/s)

kilometer (km) 0.6214 mile (mi)

milligram per second (mg/s) 0.1904 pound per day (lb/d)

The following terms and abbreviations also are used in this report:

micrograms per liter (μg/L)

milligrams per liter (mg/L)

parts per thousand relative to the Vienna Standard Mean Ocean Water (per mil VSMOW)

Principal Components Analysis (PCA)

Saturation Index (SI)

millimoles per liter (mmol/L)

milliliters per minute (mL/min)

milligram per second (mg/s)

Conversion of constituent-loading units:

Milligrams per second (mg/s) × 0.0864 = kilograms per day (kg/d)

Abstract

A tracer-injection study was done in the reach of 

Cement Creek that included Illinois Gulch and the May Day 

mine site. A lithium bromide tracer was used for the study; 

however, the tracer was not well mixed in certain sections 

of the study reach because of the large inflow at Illinois 

Gulch. Because of the uncertainty of tracer-dilution calculations downstream from Illinois Gulch, streamflow discharges 

were calculated from the dilution of lithium at certain control points, and streamflows between the control points were 

determined by linear interpolation. Water-quality samples 

were collected from stream sites, tributaries, springs, and 

seeps that affected the study reach. The May Day mine does 

not have any obvious mine drainage discharging from the adit; 

therefore, well points were installed downgradient from the 

May Day mine to further characterize contaminant flow paths 

from the site. The inflow from Illinois Gulch had higher pH 

values than did Cement Creek, and the mixing of the pH 7.39 

water with the pH 3.8 stream caused precipitation of dissolved 

iron. The inflows in the reach affected by the May Day mine 

site had low pH values but low discharges; hence, the pH of 

the stream was not greatly affected. Dissolved constituent 

concentrations fluctuated throughout the study reach, but the 

dissolved concentrations decreased most noticeably downstream from Illinois Gulch due to dilution by the large inflow. 

Total constituent concentrations increased in the reach affected 

by the May Day mine. Cumulative instream loads were greater 

than the total loads, indicating that nonconservative behavior and removal of some metals occurred in the study reach. 

Cumulative inflow loads were less than cumulative instream 

loads, indicating that diffuse ground-water sources were 

contributing loads to the study reach. The use of light stable 

isotopes of water and the technique of principal components 

analysis helped in the inventory of sources of water to the 

study reach. Mineral saturation calculations indicated supersaturation of iron and sulfate phases downstream from Illinois 

Gulch.

Introduction

Quantifying the effects of an inactive mine site on the 

environment is a difficult task, especially in mountainous terrain such as the Animas River watershed study area (fig. 1), 

and particularly at mine sites where no obvious mine drainage is discharging from an adit or portal. Several methods 

can be used for characterization of sites of inactive mines. For 

example, monitoring wells can be drilled around a mine site, 

but water samples collected from wells may only describe 

the contaminant concentrations in the immediate vicinity of 

the well, and the effects of the site on a larger scale may be 

difficult to describe from discrete well data. Leach tests can be 

performed on waste-rock samples, which might simulate the 

effects of rainfall or snowmelt passing through the waste-rock 

material (Smith, Ramsey, and Hageman, 2000; Hageman and 

Briggs, 2000); however, laboratory or field leach tests may not 

adequately represent actual field conditions. Surface geophysics can be used around a mine site to map the extent of the 

waste-rock pile, high conductivity zones within the waste-rock 

pile, and high conductivity zones of ground water discharging from the site (Campbell and Fitterman, 2000; Smith, 

McCafferty, and McDougal, 2000). These methods, however, 

do not provide conclusive evidence of the effects of the overall 

mine site on the environment.

A useful method for describing the effects of mine sites 

on stream-water quality is the application of tracer-injection 

studies (Kimball, 1997), and the tracer-injection data are 

particularly useful for reactive transport modeling (Runkel 

and Kimball, 2002). The value of a tracer-injection study is 

the ability to collect numerous synoptic samples in a short 

period of time without the need to make streamflow and 

inflow discharge measurements. Inflows can be direct (from 

a tributary or a draining adit) or diffuse (seepage from underground mine workings, seepage from waste-rock piles, or local 

and regional ground-water discharge). Diffuse inflow sources 

are the more difficult to quantify. For detailed descriptions of 

tracer-injection studies, see Kimball and others (this volume, 

Chapter E9).

Chapter E23

Effects of the May Day Mine Site on Stream-Water Quality 

in the Cement Creek Basin, August 2000

By Winfield G. Wright, Briant A. Kimball, and Robert L. Runkel
Previous studies of the entire reach of Cement Creek 

(Kimball and others, 2002; Walton-Day and others, 2000) 

indicated that the reach affected by the May Day mine (AMLI 

site # 181, fig. 1) contributed constituent loads to Cement Creek; 

however, the Illinois Gulch inflow (fig. 1) caused constituent 

mixing and possible attenuation difficult to interpret using the 

few sampling sites in the reach. Other studies of the May Day 

mine site and waste-rock pile (Smith and others, 2001; Wright 

and others, 1998) indicated high concentrations of metals 

present in the waste-rock pile; however, the dissolved constituent loads from the site could not be adequately explained by 

hydrogeochemical and mass-balance studies.

The May Day mine site is located on land administered by the Bureau of Land Management. To better quantify constituent sources from the May Day mine to Cement 

Creek, a detailed tracer-injection study was done to demonstrate the effects of Illinois Gulch, the Yukon tunnel (AMLI 

site # 186), and the May Day mine on stream-water quality. 

Figure 1. Location of May Day mine site in Cement Creek basin of Animas River watershed.

Elk Park

Mineral Creek

Animas

River

Cement Creek

Chattanooga Eureka

Silverton

MAY DAY

MINE

Animas

Forks

Howardsville

x Ohio 

Peak

Illinois Gulch

Animas River

watershed 

study area

C O L O R A D O

Durango

Study area

boundary

0

0 1

1 2 MILES

2 KILOMETERS

107o50'30" 107o45' 107o37'30" 107o30'

37o

52'

30"

37o

45'

37o

58'

948 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Effects of May Day Mine Site in Cement Creek Basin 949

The tracer study reach was referenced to the original distances 

of Kimball and others (2002) (fig. 2). Additions to the tracer 

study included water-quality samples collected from drips 

and pools inside the mine. Springs, seeps, and inflows were 

mapped near the mine site, and well points were installed 

along the streambanks to characterize contaminant flow paths 

and sample diffuse ground-water inflows (fig. 3). This report 

describes the results of the tracer-injection study.

Study Area Description

The May Day mine site is located near San Juan County 

Road 110 approximately 45 m west of Cement Creek (fig. 3). 

Coordinates of the May Day mine are lat 37°50'49" N., long 

107°40'43" W., at an elevation of 3,018 m above sea level. 

The May Day mine (about 1,000 m of tunnels) was excavated 

through propylitically altered andesitic lavas (Burns Member 

of the Oligocene Silverton Volcanics; Yager and Bove, this 

volume, Chapter E1) to access north-south-trending vein structures subparallel to the Cement Creek valley. Production and 

mining records from the May Day mine are generally lacking, but mining probably occurred from about 1910 to 1950. 

Minerals extracted from the mine included sulfide minerals 

galena (PbS), sphalerite (ZnS), pyrite (FeS2

), and chalcopyrite 

(CuFeS2); gangue minerals included quartz and feldspars, 

and the wall rock consists of andesitic lavas. The May Day 

mine entrance has no perennial mine drainage, but pools of 

water form near the entrance from snowmelt runoff during 

April–June of each year, and pools are present in the back of 

the mine during wet years. The volume of the mine waste-rock 

pile is about 5,000 m3

 (Hein and Fitterman, 1998).

The May Day mine site is a difficult site to characterize because mine drainage does not discharge directly from 

the adit, and the area has complex hydrogeology. Airborne 

conductivity mapping (Smith and others, 2001) has shown a 

linear feature (indicating a possible linear zone of fractured 

rock) near the May Day mine site. The linear feature originates 

in the Ohio Peak area northwest of the mine site (fig. 1) and 

projects into the lower segment of Cement Creek near Topeka 

Gulch and the May Day mine (Smith and others, this volume, 

Chapter E4). This linear feature may act as a conduit for discharge of ground water from mineralized areas near Ohio Peak 

into Cement Creek.

The tracer study includes the reach affected by the 

Yukon tunnel (fig. 2), which was a much larger underground 

mine than the May Day mine. The Yukon tunnel operated 

from about 1900 to the 1980s (Colorado State Archives, 

http://www.archives.state.co.us/hmrfi/g.htm, accessed 

December 31, 2002), and the primary target was tungsten 

from the mineral huebnerite (MnWO4

). The waste-rock 

pile of the Yukon tunnel contains abundant pyrite and other 

sulfide minerals, and it is at least three times larger than 

the May Day mine waste-rock pile. A small mill operated at the site during the 1970s. Mine drainage from the 

main, northern Yukon adit (fig. 2) is routed through a pipe 

into Illinois Gulch, about 50 m upstream from the confluence with Cement Creek. Discharge of water from the 

adit was about 0.03 m3

/s (Jim Herron, Bruce Stover, and 

Paul Krabacher, Unpublished Cement Creek reclamation 

feasibility report, Upper Animas River Basin, Colorado 

Division of Minerals and Geology, 1998). Concentrations 

of dissolved constituents in water from the Yukon adit were 

not high (pH=6.9, Al=<40 μg/L (micrograms per liter), 

Cu= <4 μg/L, Fe=200 μg/L, Mn=660 μg/L, SO4

=530 mg/L, 

and Zn=80 μg/L; Mast and others, 2000). Diffuse ground 

water seeps into and saturates the waste-rock pile and discharges into a constructed wetland before entering Cement 

Creek. Concentrations of dissolved constituents in the seeps 

below the Yukon waste-rock pile were extremely high 

(pH=2.5, Al=208 mg/L (milligrams per liter), Cu=14 mg/L, 

Fe=1,200 mg/L, Mn=56 mg/L, SO4

=2,700 mg/L, and 

Zn=46 mg/L; Mast and others, 2000). A small amount of 

water also discharges from the southern Yukon adit (fig. 2). 

It is difficult to sort out the contribution of Yukon adit drainage to the study reach because the drainage is included with 

the flow from Illinois Gulch; however, dissolved trace metals 

were below the detection limit in water from Illinois Gulch 

upstream from the Yukon adit (Mast and others, 2000). Most 

of the constituent loading in the Yukon reach should, therefore, come from seepage below the Yukon waste-rock pile.

Purpose and Scope

The objectives of this study were to:

• Quantify the sources of constituent loading from the 

May Day mine site to Cement Creek

• Describe the effects of the Illinois Gulch mixing zone 

on constituent transport in Cement Creek.

During August 15–17, 2000, the tracer-injection study 

was conducted in a 1,609-m reach of Cement Creek. Earlier 

tracer-injection studies in Cement Creek (Walton-Day and 

others, 2000; Kimball and others, 2002) measured the reach 

distances beginning from the headwaters of Cement Creek. 

To be consistent with the previous studies, the reach distances 

in this chapter are referenced to the headwaters distances. 

Therefore, the injection point for this tracer-injection study 

(local reach distance of 0 m) was assigned a reach distance of 

6,382 m; the end of the reach for this study (local reach distance of 1,609 m) was assigned a reach distance of 7,991 m.

Acknowledgments

Tracer-injection studies require an intensive period of 

data collection by many technical specialists. The authors 

acknowledge the assistance of Katherine Walton-Day, 

Robert E. Broshears, Jonathan B. Evans, Kenneth J. Leib, 

Tracy J. Yager, Philip L. Verplanck, Adam Kimball, 

Stephanie Odell, Bruce Stover, Aaron Packman, 

Katherine Zillich, Andrew Gleason, and Loren Wickstrom. 

This work was partially funded by the Bureau of Land 

Management. The Bureau of Reclamation installed groundwater monitoring wells at the May Day mine site.
Figure 2. Location of study reach, sample sites, and reach distances referenced to previous study of Kimball and others (2002).

Ohio Gulch

Topeka Gulch

Illinois Gulch

MAY DAY MINE (#181)

YUKON TUNNEL

(#186)

Injection point

Cement 

Creek

C e

ment

C

ree

k road

Silverton

Topeka Gulch 

alluvial fan

6,638

7,043

7,264

7,374

 7,538

7,556

7,611

7,673

7,741

7,846

7,941

7,991

6,520

7,094

6,753

6,382

6,432

6,544

6,781

6,981

7,044 7,006

7,234

7,527

7,554

7,561

7,537

7,612

7,891

7,495

7,440

7,144

6,988

6,871

7,447

7,497

7,260

7,542 and 7,545

EXPLANATION

Adit

Stream sample and distance, in meters, relative to 

 headwaters reference point

Inflow or tributary sample

Spring or well-point sample

6,520

0 200 METERS

0 500 FEET

37o51'18"

107o41'06" 107o41'08"

37o51'18"

37o50'34"

107o41'06"

37o50'34"

107o40'08" Base from U.S. Geological Survey

Orthophotoquad, Silverton, Colorado

1:12,000

950 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Effects of May Day Mine Site in Cement Creek Basin 951

Figure 3. Study reach affected by May Day mine site.

Topeka Gulch

Cement

Creek

EXPLANATION

0

0 100 FEET

33 METERS

Samples from underground

within the mine

Abandoned road

Stream sampling cross section and distance, in meters,

 relative to headwaters reference point

Well point, seep, or spring sample and number

Inflow (tributary) sample and number

7,497

7,527

7,234

Braided stream 

reach (wetland)

N

Adit

Waste piles—Hachures on downslope side

MAY DAY 

MINE

110

7,673

7,611

7,556

7,538

7,497

7,447

7,374

7,264

Well point

7,260

Yukon tunnel seeps

 7,234

Well point

7,440

Well point

7,495

Well point

7,527

Fracture 

spring

7,554

Topeka

Gulch 7,561 Channel 7,542

 draining braids

Channel 7,545 

draining braids

Left bank

seep 7,537

Ferricrete

spring

7,612

May Day mine

vein drip

May Day mine

burgundy pool

REACH AFFECTED 

BYTHE MAY 

DAY MINE
Methods of Study

Stream Tracer-Injection Study

An important part of the tracer-injection study is the 

measurement of the stream length, location of all visible 

inflows, and collection of numerous instream and inflow 

samples. On August 15, 2000, a cloth tape was used to measure 

the tracer-injection reach; instantaneous discharge measurements were made to estimate the necessary tracer concentration 

and injection rate; and inflows and tributaries were marked. 

Calculations were done to estimate the necessary concentration of tracer solution so that dilution of the tracer by inflows 

could be observed. Beginning on August 16, 2000, a solution 

of concentrated lithium bromide (18,045 mg/L as lithium) was 

pumped into Cement Creek at an injection rate of 198 mL/min 

upstream from Ohio Gulch at reach distance 6,382 m (fig. 2). 

In order to conduct a synoptic sampling event, and to use the 

tracer concentrations to calculate streamflow discharges, tracer 

concentrations must be steady throughout the reach (called the 

plateau condition). Automatic samplers were placed at fixed 

locations in the study reach; when steady tracer concentrations were obtained at these fixed sites, plateau conditions 

were achieved. The injection pump shut down overnight, but 

the pump was restarted 7 hours before the synoptic. Plateau 

conditions were achieved almost immediately after injection 

began on August 16, and plateau conditions were again quickly 

achieved after the pump was restarted on August 17 (fig. 4). 

The synoptic sampling effort—or snapshot in time—was done 

on August 17, 2000 (fig. 4).

Tracer concentrations in the stream were used to compute 

the streamflow discharges in the study reach, and the streamflow discharge profile was constructed from the discharge data. 

Dissolved lithium was used in this study for the tracer concentrations. Construction of the streamflow discharge profile in the 

study reach was difficult, owing to poor mixing of the tracer 

in certain segments, such as downstream from Illinois Gulch. 

Therefore, discharges were computed at selected control points 

in the stream where confidence in the lithium data was better 

(sites 6,638, 6,988, 7,043, 7,094, 7,538, and 7,941; fig. 2). 

Discharge was computed via the equation:

Qstream = Qinjection * Cinjection / (Cstream – Cbackground) (1)

where

Qstream was the calculated discharge at the control 

point in the stream,

 Qinjection was the fl ow rate of the injection pump 

(0.033 L/s),

Cinjection was the lithium concentration of the injectate 

(18,045 mg/L),

Cstream was the lithium concentration in the stream 

at the control point (from analytical data),

and

Cbackground was the background lithium concentration 

(0.02 mg/L).

Discharge at the remaining sites was estimated by linear 

interpolation between the control points (fig. 5). The streamflow discharges were verified by instantaneous discharge 

measurements (using a flow anemometer) done on the day of 

Figure 4. Bromide concentrations at fixed sites illustrating plateau conditions. Error 

bars show plus-or-minus standard deviation of laboratory analyses.

SYNOPTIC SAMPLING PERIOD

BROMIDE, IN MILLIGRAMS PER LITER

Bromide concentrations from automatic sampler

Smoothed bromide concentrations from automatic sampler

INJECTION PUMP

SHUT DOWN, THEN

RESTARTED THE

MORNING OF THE

SYNOPTIC SAMPLING

PERIOD

EXPLANATION

Intermittent samples collected

at reach distance 6,753 m

0.0

0.5

1.0

1.5

2.0

2.5

1800 2400 0600 1200

August 16, 2000 August 17, 2000

7,447 m

7,991 m

952 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Effects of May Day Mine Site in Cement Creek Basin 953

the synoptic. For example, from equation 1, the discharge at 

site 7,941 was 413.6 L/s, and the instantaneous discharge measurement at the next site downstream (7,991) was 414.5 L/s 

on August 17, 2000, at 1300 hours. Inflow discharges were 

estimated by the difference of discharge between streamflow 

discharge at upstream and downstream sites.

On the day of the synoptic, water samples were collected 

from 41 sites throughout the study reach (table 1; fig. 2). This 

collection included 22 stream samples, 12 inflow samples, 

4 samples from well points, 1 seep site, and 2 samples from 

inside the mine. Stream samples were collected via depth- and 

width-integrated sampling techniques (Edwards and Glysson, 

1988), and inflow samples were collected via grab methods. 

Samples were placed in 2-L pre-cleaned polyethylene containers and transported in dark plastic bags (to prevent the effects 

of sunlight on water samples) to a central location near the 

study reach. Field measurements for pH and other properties 

were done within 1 hour of sample collection. Stream samples 

were filtered through a laboratory-scale, tangential-flow, 

ultra-filtration apparatus with 10,000-Dalton molecular weight 

filters, and they were filtered at the central location near the 

study reach within 2 hours of sample collection. Samples were 

decanted for analysis of total (unfiltered) constituent concentrations. Inflows were sampled for total (unfiltered) analyses. 

Details of sample collection, filtration methods, and laboratory 

analyses for tracer-injection studies are described in Kimball 

and others (2002).

Quantification of Constituent Concentrations 

and Loads

Longitudinal stream profiles of pH values, constituent 

concentrations, and constituent loads are used in this chapter 

to illustrate the effects of tributaries, mine sites, springs, and 

diffuse sources on the fate and transport of contaminants in the 

stream. The synoptic sampling effort collects the numerous 

samples to characterize the study reach, and laboratory analyses of the samples provide data to construct the longitudinal 

profiles of constituent concentrations. Loads are computed 

by multiplication of the streamflow discharge by constituent 

concentrations (Kimball and others, 2000; Kimball and others, 

this volume). To describe the stream-water quality of the study 

reach, different characteristics of the data are presented:

1. Total instream concentrations and loads from unfiltered 

analyses. These data represent what the fish and aquatic 

life actually are exposed to in the stream.

2. Dissolved instream concentrations and loads from samples 

filtered through the ultrafiltration apparatus. These data 

represent what actually is in the dissolved phase, and indicate the constituents that result from mineral dissolution.

3. Colloidal instream load—total load (1) minus the dissolved load (2). This represents the solid phases that are 

being transported as suspended particulates in the stream. 

Figure 5. Longitudinal stream profile of discharges in the study reach.

Instream sampling point

EXPLANATION

300

320

340

360

380

400

420

440

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

REACH DISTANCE, IN METERS

STREAMFLOW DISCHARGE, IN LITERS PER SECOND

ILLINOIS GULCH

MAY DAY REACH

OHIO GULCH

TOPEKA GULCH ALLUVIAL FAN

YUKON REACH

TOPEKA GULCH
Colloidal load is part of the suspended load; however, this 

is quite different from the typical definition of suspended 

sediment transport, where silt- and sand-sized particles 

are transported by saltation (Graf, 1971). Colloids result 

from the chemical precipitation of dissolved constituents that are supersaturated with respect to a mineral 

phase. Colloids frequently are composed of amorphous 

(unidentifiable or noncrystalline) solids. In waters affected 

by acid-rock drainage, these solids consist of amorphous 

iron oxyhydroxide, iron sulfate, aluminum hydroxide, and 

aluminum sulfate phases (Schemel and others, 2000).

4. Cumulative instream load—sum of positive total load 

changes in a downstream direction. Because the total 

(unfiltered) load is the combination of all constituent 

phases—dissolved and colloidal—being transported by 

the stream, it becomes useful to sum the positive changes 

of instream load between stream sites in a cumulative 

downstream direction. This sum gives the best estimate 

of the total loading along the study reach. The cumulative 

instream load also indicates the total load in the stream 

if attenuation or colloid precipitation was not taking place.

5. Cumulative inflow loads—sum of inflow loads in a 

downstream direction. Inflows are the obvious tributaries, 

primarily consisting of visible streams and springs, and 

these obvious inflows are sampled during the synoptic. 

Inflow constituent loads are computed by multiplication 

of the inflow discharge by the inflow total (unfiltered) 

concentrations (Kimball and others, 2000). The inflow 

loads are summed in a downstream direction and compared to the cumulative instream loads, which also are 

total (unfiltered) loads. If the cumulative inflow loads 

do not equal the cumulative instream loads, there was 

probably a diffuse ground-water inflow that was not 

sampled. In addition to the diffuse nature of some lateral 

inflows, ground water can be moving down valley in the 

subsurface and can be forced to the surface by geologic 

structures or fractures, discharging to the stream as diffuse 

ground water (Wyrick and Borchers, 1981).

Evaluation of Sources

There are few methods to distinguish sources of constituents that enter a stream reach; for example, do they come 

from bedrock or mining-related sources? These sources may 

be evaluated using the light stable isotopes of water (Muir 

and Coplen, 1981; Hoefs, 1987). Oxygen and hydrogen stable 

isotopes can be affected by the source of the water (different 

weather patterns, altitude of precipitation, or connate water 

deposited in rock formations), and the isotopes are fractionated 

by evaporation, plant transpiration (Hoefs, 1987), and waterrock interaction (Plumlee and others, 1999). Hence, light stable 

isotope values can help to identify different sources of water. 

During the tracer-injection study, isotope samples were collected from selected well points, springs and seeps, and pools 

inside the mine (fig. 3).

Patterns in the chemistry and pH of stream and inflow 

samples were evaluated by use of Principal Components 

Analysis (PCA), a multivariate analysis technique (Daultrey, 

1976; Joreskog and others, 1976; Grundy and Miesch, 1987). 

Principal components represent a set of new, transformed 

reference axes that are linear combinations of the original 

variables; PCA is a transformation of data, not a statistical 

treatment. A principal components transformation orients the 

data points so that the first of the new axes, principal component 1 (PC1), is oriented along the direction of the greatest 

variance in the data. The second principal component (PC2) 

is orthogonal to PC1, and is oriented to show the next greatest 

amount of variance in the data. This is easy to picture in two 

dimensions. One can imagine drawing a line that would go 

through the two most distant points in a bivariate plot of data; 

that would be the direction of PC1. It would be at some angle 

to the original x and y axes, but any point along the line could 

be described by a linear equation. PC2 would be drawn perpendicular to PC1, and it would have its own linear equation. 

In multidimensional space, each subsequent principal component is orthogonal to the first two and represents a decreasing 

amount of the total variance.

Typically, the first two or three principal components 

show enough of the variance in the data set to enable the 

recognition of groups among samples; this is the advantage 

of using the method for multivariate data. Synoptic samples 

are plotted by their PCA scores, which are the coordinates 

of the original data points on the new principal component 

axes. Adding vectors representing the correlations of original 

variables with the new principal component axes to the plot 

of scores creates a biplot. The vectors help identify variations 

in chemistry among the groups of samples. For the analysis, 

chemical concentrations, including pH, were converted to 

millimoles per liter and used in the biplots after logarithmic 

transformation.

Effects of the May Day Mine Site 

on Stream-Water Quality

The mixing zone downstream from Illinois Gulch and the 

reach affected by the May Day mine were of primary interest, 

and a considerable stream length was required to adequately 

mix the tracer solution; therefore, the injection point was 

located upstream from Ohio Gulch (fig. 2). Longitudinal 

stream profiles of pH values, constituent concentrations, and 

constituent loads illustrate the effects of inflows and mine sites 

on stream-water quality.

954 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Effects of May Day Mine Site in Cement Creek Basin 955

Table 1. Sites where water-quality samples were collected in the tracer study reach, August 17, 2000.

[--, not applicable]

Site description

Distance from headwaters 

of Cement Creek

(meters)

Sample from stream, 

east bank, or west bank

(fig. 2)

Features described 

in figures and graphs

Mainstem sites

Upstream from injection 6,382 stream

First site downstream from injection 6,432 stream

Downstream 129 meters from injection 6,520 stream

Downstream from diffuse inflows 6,638 stream

Upstream from Ohio Gulch, autosampler 6,753 stream

Downstream 90 meters from Ohio Gulch 6,871 stream

Upstream from Illinois Gulch 6,988 stream

Downstream 37 meters from Illinois Gulch 7,043 stream

Downstream 88 meters from Illinois Gulch 7,094 stream Yukon tunnel

At Bridge to Yukon tunnel 7,144 stream reach

Downstream from Yukon tunnel seeps 7,264 stream

Downstream from seepage along banks 7,374 stream

Near beginning of braided reach, autosampler 7,447 stream

Adjacent to braided reach 7,497 stream May Day mine

Upstream from May Day inflows 7,538 stream reach

Upstream from Topeka Gulch 7,556 stream

Downstream from Topeka Gulch 7,611 stream

Downstream from Topeka Gulch alluvial fan 7,673 stream Topeka Gulch

Near end of Topeka Gulch alluvial fan 7,741 stream alluvial fan

Downstream from cascading reach 7,846 stream

Downstream from large spring 7,941 stream

End of study reach, autosampler 7,991 stream

Tributary, well point, and spring sites

Spring discharging from hill 6,544 east

Ohio Gulch at mouth 6,781 west

Unnamed adit upstream from Illinois Gulch 6,981 east

Illinois Gulch 7,006 east

Draining small gully on right bank 7,044 west Yukon tunnel

Yukon tunnel seep 7,234 7,234 east reach

Well point 7,260 7,260 west

Well point 7,440 7,440 west

Well point 7,495 7,495 west

Well point 7,527 7,527 west May Day mine

Left bank seep 7,537 7,537 east reach

First channel draining braided reach 7,542 west

Channel draining braided reach 7,545 west

Fracture spring 7,554 7,554 west

Topeka Gulch at mouth 7,561 west

Large ferricrete spring 7,612 7,612 west Topeka Gulch

Spring in Topeka Gulch alluvial fan 7,891 west alluvial fan

Sites inside the May Day mine

North mineralized vein within mine -- -- Mine sample

Burgundy pool in mine -- -- Mine sample
pH and Constituent Concentrations

The longitudinal profile of pH and constituent concentrations in the study reach was affected by several factors: 

(1) inflows with low or high pH (direct and diffuse sources), 

(2) inflows with low or high constituent concentrations (direct 

and diffuse sources), (3) dilution from inflows, (4) analytical 

error in laboratory measurement of constituent concentrations, and (5) measurement error in collection of adequate 

width-integrated samples across the stream cross section. 

The analytical error was addressed by showing the analytical 

precision of each measurement on the concentration profiles; 

the error bars show the plus-or-minus precision estimates for 

each analytical determination. If the lower error limit of a 

downstream concentration was greater than the upper error 

limit of an upstream concentration, there was probably a 

significant increase in a constituent concentration entering the 

stream between those two points (Kimball and others, 2002). 

The errors associated with loads can be cumulative because 

of the analytical concentration error and the possible error in 

discharge computation. These errors are discussed in Kimball 

and others (this volume), but the method was not applied to 

loading data presented in this chapter.

The most apparent feature of the pH profile in the study 

reach was the increase in stream pH due to streamflow from 

Illinois Gulch (fig. 6). In general, the west side (right bank) 

of the Cement Creek basin contains metal-rich rocks and 

very low pH water, and the east side contains propylitically 

altered rocks with higher pH water (Mast and others, 1998). 

This reflects the distribution of hydrothermally altered rocks 

in the watershed (Bove and others, this volume, Chapter E3). 

From previous studies, the mainstem of Cement Creek has a 

pH of less than 4 for most of its 11.6 km length (Kimball and 

others, 2002; Walton-Day and others, 2000); however, in the 

lower reaches several tributaries that drain rocks from the east 

side of Cement Creek have circumneutral pH; these include 

Illinois Gulch. The pH of Cement Creek at the injection point 

was about 3.65 on the day of the synoptic sampling (fig. 6). 

Downstream from the confluence with Illinois Gulch, which 

had a pH of 7.39, the pH of Cement Creek increased to 4.16 

Figure 6. Longitudinal stream profile of pH in Cement Creek through study reach and pH values of inflows and tributaries. 

Error bars represent ±0.05 pH units.

2

3

4

5

6

7

8

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

REACH DISTANCE, IN METERS

pH, IN STANDARD UNITS

EXPLANATION

East bank tributary or inflow

Cement Creek

ILLINOIS GULCH

MAY DAY REACH

TOPEKA GULCH ALLUVIAL FAN

OHIO GULCH

West bank tributary or inflow

Well point 7,495 Mine water YUKON REACH

956 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Effects of May Day Mine Site in Cement Creek Basin 957

and continued to increase to 4.35 even though the seeps from 

the Yukon site had a pH of 3.09. The stream pH decreased to 

4.21 at reach distance 7,447 m. The pH fluctuated between 

4.31 and 4.17 through the reach affected by the May Day mine 

site (fig. 6). Even though the water from the pools inside the 

May Day mine had a pH of 2.49, the pH in Cement Creek was 

only slightly affected by inflows from the mine site because of 

small inflow discharges.

Increases and decreases of dissolved and total aluminum 

concentrations alternated between sites throughout the study 

reach (fig. 7A). The dissolved and total aluminum concentrations were mostly the same at each site because of the low 

stream pH (fig. 7A). Aluminum precipitation from the dissolved phase occurs between pH 4.4 and 5.4, and aluminum 

does not completely precipitate from solution until pH exceeds 

5.4 (Nordstrom and Ball, 1986). Hence, with the stream pH of 

3.65 to 4.19, a substantial amount (between 5.3 and 6.4 mg/L) 

of dissolved aluminum was present in the stream. Downstream 

from Illinois Gulch, dissolved and total aluminum concentrations showed a decrease that was probably caused by dilution. 

Total aluminum concentrations increased in the May Day 

reach, possibly due to increased concentrations of aluminum 

particulates.

Total copper concentrations showed alternating increases 

and decreases throughout the study reach (fig. 7B). There 

may have been contamination of the water-quality samples 

for the dissolved copper analyses due to a malfunction of the 

ultrafiltration apparatus; therefore, dissolved copper results 

are not presented. Samples for analysis of total copper did 

not contact the filtration apparatus; therefore, total copper 

results are presented. Total copper concentrations increased 

at 6,988 m, just downstream from the inflow of the adit at 

6,981 m (fig. 2). Downstream from Illinois Gulch, the total 

copper decreased, possibly due to dilution. Generally, total 

copper increased slightly in Cement Creek as it flowed past 

the Yukon site, and total copper increased in the May Day 

reach. Total copper increased at 7,846 m, downstream from 

the Topeka Gulch alluvial fan (fig. 2), and then decreased to 

the end of the study reach.

In contrast to the aluminum profile, dissolved iron concentrations in the study reach were consistently less than total 

iron concentrations (fig. 7C), a condition caused by the pH 

values of the stream being greater than that for iron solubility. 

Theoretical iron solubility occurs at about pH 1.7 (Garrels and 

Christ, 1965), but other factors affecting iron solubility, such 

as photoreduction (McKnight and others, 1988), contribute to 

the presence of dissolved iron in water measuring above this 

pH. Dissolved iron concentrations decreased downstream from 

Illinois Gulch (from 5.25 to 4.18 mg/L). The slight increase 

of total iron downstream from Illinois Gulch shows inflows 

from the Yukon tunnel. Dissolved iron concentrations were not 

significantly affected by the May Day reach; however, total iron 

concentrations increased at the May Day reach (fig. 7C). Total 

iron concentrations increased steadily from 7,741 m to 7,941 m, 

in the reach affected by the Topeka Gulch alluvial fan.

Dissolved and total manganese concentrations showed 

alternating increases and decreases throughout the study reach 

(fig. 8A). However, because both the dissolved and the total 

concentrations were within the analytical error limits along 

most of the study reach, they essentially were equal. That total 

manganese concentrations decreased downstream from Illinois 

Gulch indicated dilution by the inflow. Total manganese 

increased substantially in the May Day reach (fig. 8A). Total 

manganese decreased downstream from Topeka Gulch, then 

increased at the lower end of the study reach.

Dissolved sulfate concentrations alternately increased 

and decreased throughout the study reach (fig. 8B); analyses 

for total sulfate concentrations were not done for this study, 

and are not shown on the graph. Downstream from the injection point, dissolved sulfate concentrations began a strong 

decrease just upstream from Illinois Gulch.

Dissolved and total zinc concentrations showed alternating increases and decreases throughout the study reach 

(fig. 8C). The dissolved concentration was greater than the 

total concentration at a few sites due to analytical error; the 

differences were less than 10 percent. Dissolved zinc concentrations decreased from the Ohio Gulch inflow to the May Day 

reach, followed by alternating increases and decreases from 

the May Day reach to the end of the study reach (fig. 8C). 

Total zinc concentrations decreased downstream from Illinois 

Gulch, increased in the May Day reach, and fluctuated downstream from Topeka Gulch (fig. 8C). Patterns of manganese 

and zinc concentrations were similar, possibly due to similar 

geologic sources of manganese and zinc minerals (Bove and 

others, this volume).

Constituent Loads

Increase in a constituent load reflects an input of constituent mass to the stream; decrease in constituent load reflects 

instream geochemical, biological, or physical processes by 

which mass is being removed. Longitudinal loading profiles 

were constructed for the study reach and show the loads for 

the different load fractions: (1) total load, (2) dissolved load, 

(3) colloidal load, (4) cumulative instream load, and (5) cumulative inflow load.

The longitudinal profile for aluminum loads showed 

that the dissolved and total fractions were about the same 

and the colloidal loads were small: the low pH values in the 

stream contributed to aluminum’s remaining in the dissolved 

phase (fig. 9A). The dissolved aluminum load ranged from 

2,047 to 2,268 mg/s in the study reach. In contrast, the colloidal aluminum load ranged from 0 to 342 mg/s; because 

of the graph scale, the colloidal aluminum load is not shown 

(fig. 9A). Aluminum loads were relatively constant throughout 

the study reach, except for an increase of total load upstream 

from Illinois Gulch (unnamed mine site 6,981—fig. 2; table 1), 

in the May Day reach, and through the Topeka Gulch alluvial 

fan (fig. 9A). Total aluminum loads decreased in the Yukon 
Figure 7. Longitudinal stream profiles of dissolved and total constituent 

concentrations in study reach. A, aluminum, B, copper; C, iron. Error bars show 

plus-and-minus analytical precision for each concentration. ILLINOIS GULCH OHIO GULCH REACH TOPEKA GULCH OHIO GULCH ILLINOIS GULCH YUKON REACH TOPEKA GULCH CONCENTRATION, IN MILLIGRAMS PER LITER

4.0

4.5

5.0

5.5

6.0

6.5

7.0

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

A

B

C

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

REACH DISTANCE, IN METERS

Dissolved concentration Total concentration

EXPLANATION

0.05

0.06

0.07

0.08

0.09

0.10

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180 ILLINOIS GULCH MAY DAY MAY DAY REACH REACH MAY DAY REACH OHIO GULCH

(DISSOLVED 

 CONCENTRATIONS

 NOT SHOWN)

ALLUVIAL

FAN

TOPEKA

GULCH

ALLUVIAL

FAN

TOPEKA

GULCH

ALLUVIAL

FAN

TOPEKA

GULCH

YUKON REACH

TOPEKA GULCH

YUKON

958 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Effects of May Day Mine Site in Cement Creek Basin 959

Figure 8. Longitudinal stream profiles of dissolved and total constituent 

concentrations in study reach. A, manganese, B, sulfate; C, zinc. Error bars 

show plus-and-minus analytical precision for each concentration. OHIO GULCH ILLINOIS GULCH YUKON REACH TOPEKA GULCH OHIO GULCH ILLINOIS GULCH YUKON REACH TOPEKA GULCH CONCENTRATION, IN MILLIGRAMS PER LITER

1.60

1.65

1.70

1.75

1.80

1.85

1.90

1.95

2.00

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

A

B

C

1.00

1.05

1.10

1.15

1.20

1.25

1.30

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

REACH DISTANCE, IN METERS

Dissolved concentration Total concentration

EXPLANATIONMAY DAY REACH MAY DAY REACH

500

510

520

530

540

550

560

570

580

590

600

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

(TOTAL

 CONCENTRATIONS

 NOT SHOWN)OHIO GULCH

ILLINOIS GULCH

YUKON REACH

TOPEKA GULCH

MAY DAY REACH

ALLUVIAL

FAN

TOPEKA

GULCH

ALLUVIAL

FAN

TOPEKA

GULCH

TOPEKA GULCH 

ALLUVIAL FAN
ILLINOIS GULCH

OHIO GULCH

YUKON REACH

GULCH

MAY DAY REACH

ALLUVIAL

FAN

TOPEKA

GULCH

OHIO GULCH

ILLINOIS GULCH

YUKON REACH

TOPEKA GULCH

MAY DAY REACH

ALLUVIAL

FAN

TOPEKA

GULCH

OHIO GULCH

ILLINOIS GULCH

YUKON REACH

TOPEKA GULCH

MAY DAY REACH

ALLUVIAL

FAN

TOPEKA

GULCH

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

REACH DISTANCE, IN METERS

LOAD, IN MILLIGRAMS PER SECOND

Cumulative instream load Cumulative inflow load

Total load Dissolved load

Colloidal load

EXPLANATION

20

25

30

35

40

45

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

A

B

C

1,900

2,100

2,300

2,500

2,700

2,900

3,100

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

(DISSOLVED LOADS

 NOT SHOWN)

TOPEKA

Figure 9. Longitudinal stream profiles of constituent loads in study reach. A, aluminum, 

B, copper; C, iron.

960 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Effects of May Day Mine Site in Cement Creek Basin 961

reach. In the May Day reach, total aluminum load increased 

from 2,163 to 2,415 mg/s for a gain of 252 mg/s. Cumulative 

instream loads were greater than the total loads throughout 

the study reach, indicating that nonconservative behavior and 

removal of aluminum took place. Some divergence of cumulative instream and total load occurred at Illinois Gulch, but 

most of the divergence occurred downstream from the May 

Day reach. Cumulative inflow loads were less than the cumulative instream loads, indicating the presence of unsampled or 

diffuse sources of aluminum loading in the study reach.

The longitudinal profile of total copper loads showed 

increases and decreases in the study reach (fig. 9B). Dissolved 

and colloidal copper loads are not presented, owing to copper 

contamination from the filtration equipment. Total copper 

loads increased upstream from Illinois Gulch, through the May 

Day reach, and in the lower end of the study reach affected by 

the Topeka Gulch alluvial fan (fig. 2; table 1). Gains in total 

copper loads were small in the Yukon reach. In the May Day 

reach, total copper load increased from 29.4 to 32.4 mg/s for 

a gain of 3.0 mg/s. Cumulative instream loads were greater 

than the total loads, indicating nonconservative behavior and 

removal of copper in the study reach. Cumulative inflow loads 

were less than cumulative instream loads, indicating diffuse 

sources of copper loading in the study reach.

The longitudinal profiles for iron loads showed that the 

dissolved and total fractions were quite different (fig. 9C), and 

colloidal loads were substantial compared to the other constituents. In the Yukon reach (affected by the mixing of Illinois 

Gulch and Cement Creek water), total iron load increased, 

dissolved load decreased, and colloidal load increased 

indicating precipitation of iron colloids (fig. 9C). Colloidal 

loads increased in the May Day reach, but the dissolved load 

remained essentially the same (fig. 9C). In the May Day reach, 

total iron loads increased from 3,006 to 3,267 mg/s for a gain 

of 261 mg/s. Cumulative instream loads were greater than the 

total loads, indicating nonconservative behavior and removal 

of iron in the study reach. Some divergence of cumulative 

instream and total load occurred between Illinois Gulch and 

the May Day reach, but most of the divergence occurred 

downstream from the May Day reach. Cumulative inflow 

loads were much less than the cumulative instream loads, 

indicating diffuse sources of iron loading in the study reach.

The longitudinal profile for manganese loads showed 

that the dissolved and total fractions were nearly the same, 

except in the May Day reach (fig. 10A). Colloidal loads were 

small compared to the total and dissolved loads; because of the 

graph scale, colloidal loads are not shown. Manganese loads 

increased upstream from Illinois Gulch, at Illinois Gulch, 

through the May Day reach, and downstream from Topeka 

Gulch. In the May Day reach, total manganese loads increased 

from 714 to 782 mg/s for a gain of 68 mg/s. Cumulative 

instream loads were greater than the total loads, indicating 

nonconservative behavior and removal of manganese in the 

study reach. Cumulative inflow loads were much less than 

the cumulative instream loads, indicating diffuse sources of 

manganese loading in the study reach.

The longitudinal profile for dissolved sulfate loads 

showed alternating decreases and increases (fig. 10B). Total 

sulfate was not analyzed; therefore, cumulative dissolved 

instream loads are shown rather than cumulative instream 

loads. The dissolved sulfate load increased at Illinois Gulch, 

the Yukon reach, the May Day reach, and downstream from 

Topeka Gulch. In the May Day reach, dissolved sulfate loads 

increased 8,000 mg/s. The large sulfate increase in the Yukon 

reach may be caused by the presence of gypsum (CaSO4

·2H2O) 

in the Yukon tunnel. Cumulative dissolved loads were greater 

than the dissolved loads, indicating nonconservative behavior 

and removal of sulfate in the study reach. Cumulative inflow 

loads were less than the cumulative dissolved loads, indicating 

diffuse sources of sulfate loading in the study reach.

The longitudinal profile for zinc loads showed that the 

dissolved and total loads were nearly the same (fig. 10C), but 

the colloidal loads were small; because of the graph scale, 

colloidal loads are not shown. The cumulative instream zinc 

loads increased upstream from Illinois Gulch, in the Yukon 

reach, in the May Day reach, and downstream from Topeka 

Gulch (fig. 10C). In the May Day reach, zinc load increased 

37.0 mg/s. Cumulative instream loads were greater than the 

total loads, indicating nonconservative behavior and removal 

of zinc in the study reach. Cumulative inflow loads were less 

than the cumulative instream loads, indicating diffuse sources 

of zinc loading in the study reach.

Constituent Attenuation

Constituent attenuation results from processes in the 

environment that act to reduce the mass of contaminants or 

constituents (Webster and others, 1994). The processes causing constituent attenuation may include adsorption, colloid 

precipitation, coprecipitation of metals with colloid formation, 

reaction with organic matter, losses to biofilm, and settling of 

colloids from the stream onto the streambed. Loss of the total 

load best reflects attenuation because the total mass (which 

includes dissolved and colloidal fractions) is removed from the 

system. Loss of dissolved load may result from colloid formation or other chemical and biological processes. Longitudinal 

profiles of changes in load between sampling points are shown 

to describe attenuation in the study reach.

The longitudinal profile of dissolved iron load showed 

alternating increases and decreases throughout the study reach; 

however, small changes may be due to analytical error. The 

dissolved iron load shows general patterns of load decrease 

in the upper portions of the study reach (fig. 11A), indicating iron precipitation and colloid formation. The dissolved 

iron load generally increased in the lower end of the study 

reach (fig. 11A), indicating gains of dissolved iron mass from 

inflows or the dissolution of iron colloids by low-pH inflows. 

The longitudinal profile of total iron load showed alternating 

increases and decreases throughout the study reach (fig. 11B). 

Decreases reflect a loss of iron mass from the system.

The longitudinal profile of dissolved sulfate load showed 

alternating increases and decreases throughout the study reach 

(fig. 12). A large increase of dissolved sulfate load came from 
Figure 10. Longitudinal stream profiles of constituent loads in study reach. A, manganese, 

B, sulfate; C, zinc.

ILLINOIS GULCH

OHIO GULCH

YUKON REACH

TOPEKA GULCH

MAY DAY REACH

ALLUVIAL

FAN

TOPEKA

GULCH

ILLINOIS GULCH

OHIO GULCH

YUKON REACH

TOPEKA GULCH

MAY DAY REACH

ALLUVIAL

FAN

TOPEKA

GULCH

LOAD, IN MILLIGRAMS PER SECOND

Cumulative instream load Cumulative inflow load

Total load Dissolved load

Colloidal load

EXPLANATION

A

B

C

350

400

450

500

550

600

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

REACH DISTANCE, IN METERS

600

650

700

750

800

850

900

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

Cumulative dissolved load

(TOTAL LOADS

 NOT SHOWN)

180,000

190,000

200,000

210,000

220,000

230,000

240,000

250,000

260,000

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180 ILLINOIS GULCH OHIO GULCH YUKON REACH TOPEKA GULCH MAY DAY REACH ALLUVIAL FAN TOPEKA GULCH

962 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Effects of May Day Mine Site in Cement Creek Basin 963

ILLINOIS GULCH

OHIO GULCH

YUKON REACH

TOPEKA GULCH

EXPLANATION

Load increase between stream sampling points

Load decrease between stream sampling points

-300

-200

-100

0

100

200

300

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

CHANGE IN DISSOLVED IRON LOAD, 

IN MILLIGRAMS PER SECOND

-300

-200

-100

0

100

200

300

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

REACH DISTANCE, IN METERS

CHANGE IN TOTAL IRON LOAD, 

IN MILLIGRAMS PER SECOND

A

B

ILLINOIS

MAY DAY

GULCH

REACH MAY DAY REACH

ALLUVIAL

FAN

TOPEKA

GULCH

ALLUVIAL

FAN

TOPEKA

GULCH

OHIO GULCH

YUKON REACH

TOPEKA GULCH

Figure 11. Longitudinal stream profiles of change in A, dissolved iron, and B, total iron loads 

in study reach.
Illinois Gulch (fig. 12) possibly due to the presence of gypsum 

and sulfate minerals in the Yukon tunnel and discharge of 

sulfate-rich mine drainage into Illinois Gulch from the Yukon 

adit. In several segments in the study reach, dissolved sulfate 

showed a decrease in load; however, the loss was only about 

2 percent, which may be due to error. If dissolved sulfate 

losses did occur in the study reach, they could be due to precipitation of sulfate-containing colloids such as schwertmannite (Desborough and others, 2000).

The longitudinal profile of dissolved zinc loads showed 

alternating increases and decreases throughout the study reach 

(fig. 13A). An increase in zinc load reflects a gain of dissolved 

zinc mass from inflows and dissolution of colloids by lowpH inflows. Decreases may reflect a loss of dissolved zinc 

mass due to coprecipitation or adsorption of zinc along with 

the formation of iron sulfate colloids. These gains and losses 

were relatively small compared to the total zinc mass being 

transported by the stream (fig. 10C). Dissolved zinc loads 

decreased downstream from Ohio Gulch and the Yukon reach, 

with slight losses in the May Day reach and downstream from 

Topeka Gulch. Dissolved zinc loads increased just downstream 

from the injection point, at Illinois Gulch, at the Yukon tunnel 

settling ponds, and downstream from Topeka Gulch (fig. 13A). 

Total zinc loads increased at the inflow of the unnamed mine, 

in the Yukon reach, in the May Day reach, and through the 

Topeka Gulch alluvial fan (fig. 13B).

Evaluation of Water Sources

Water in the study reach came from three sources: 

(1) inflows or obvious tributaries, (2) obvious springs or seeps, 

and (3) diffuse ground-water inflows. The May Day mine site 

has no perennial discharge, and contaminant flow paths from 

the mine to the stream might occur as diffuse inflows; therefore, 

an evaluation of whether water from the May Day mine site discharges to Cement Creek was important. Two approaches were 

taken: (1) the use of light stable isotopes as a hydrologic tracer, 

and (2) principal components analysis (PCA).

Samples were collected in the May Day reach for 

analysis of the oxygen and hydrogen light stable isotopes of 

water. The ratio of the 18O and 16O isotopes and the 2

H and 1H 

isotopes is referenced to an international standard (The Vienna 

Standard Mean Ocean Water, or VSMOW), expressed in the 

delta notation:

G

18O

O 18 O 16 e (sample)

O 18 O 16 e (standard)

---------------------------------------- – 1 © 1  ̈  ̧ § · = u 1 000  (2)

where the units are in parts per thousand referenced to the 

standard, or per mil VSMOW. A similar expression is developed for the δ2

H isotopes. Craig (1961) plotted δ18O and δ2H 

isotope values from around the world and developed a global 

ILLINOIS GULCH

OHIO GULCH

YUKON REACH

TOPEKA GULCH

EXPLANATION

Load increase between stream sampling points

Load decrease between stream sampling points

-30,000

-20,000

-10,000

0

10,000

20,000

30,000

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

REACH DISTANCE, IN METERS

CHANGE IN DISSOLVED SULFATE LOAD, 

IN MILLIGRAMS PER SECOND

MAY DAY REACH

ALLUVIAL

FAN

TOPEKA

GULCH

Figure 12. Longitudinal stream profile of change in dissolved sulfate loads in study reach.

964 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Effects of May Day Mine Site in Cement Creek Basin 965

ILLINOIS GULCH

OHIO GULCH

YUKON REACH

TOPEKA GULCH

ILLINOIS GULCH

OHIO GULCH

YUKON REACH

TOPEKA GULCH

-40

-30

-20

-10

0

10

20

30

40

50

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

CHANGE IN DISSOLVED ZINC LOAD, 

IN MILLIGRAMS PER SECOND

EXPLANATION

Load increase between stream sampling points

Load decrease between stream sampling points

B

A

MAY DAY REACH MAY DAY REACH

-40

-30

-20

-10

0

10

20

30

40

50

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

REACH DISTANCE, IN METERS

CHANGE IN TOTAL ZINC LOAD, 

IN MILLIGRAMS PER SECOND

ALLUVIAL

FAN

TOPEKA

GULCH

ALLUVIAL

FAN

TOPEKA

GULCH

Figure 13. Longitudinal stream profiles of change in A, dissolved zinc, and B, total zinc loads 

in study reach.
meteoric water line (GMWL), and an equation for the slope 

of the GMWL with the expression δ2

H = 8 δ18O + 10. Most 

δ18O and δ2

H isotope values should fall on or near the GMWL 

unless the isotopes have been fractionated by evaporation, 

plant transpiration, or water-rock interaction.

As part of previous studies in the Animas River watershed during 1995, isotope data were collected from springs, 

streams, and mines in Middle Fork Mineral Creek (Sole and 

others, this volume, Chapter G). An equation for the slope of 

these data has the expression δ2

H = 8.3 δ18O + 17 (fig. 14), 

which differs only slightly from the GMWL. For the purposes 

of this discussion, this is called the “Animas meteoric water 

line” (AMWL). Samples collected from Cement Creek during the May Day reach tracer study plotted on the AMWL 

(fig. 14). May Day mine pool and drip samples plotted below 

the AMWL (fig. 14). May Day reach well-point data also 

plotted below and to the right of the AMWL (fig. 14), and the 

Figure 14. Oxygen and hydrogen isotopes of water samples collected from study reach 

and from selected springs, streams, and inactive mines as part of other studies in Animas 

River watershed study area. VSMOW, Vienna Standard Mean Ocean Water.

slope of the line through the May Day data is significantly 

different (p<0.03). The samples from fracture spring 7,554 

and ferricrete spring 7,612 plot between the May Day mine 

and the well-point data (fig. 14). These data suggest several 

different sources of water in the May Day reach: (1) May Day 

mine waters, (2) well-point waters, or (3) a mixture of May 

Day mine and well-point waters. The source of the well-point 

waters is uncertain; however, the water could have traveled far 

distances along fractures, experiencing isotopic fractionation 

along the ground-water flow path. These water samples were 

distinctly different (p<0.01) from the water in Cement Creek.

Dissolved zinc concentrations combined with the isotope data may help to clarify the sources of water in the 

May Day reach. Dissolved zinc concentrations of water 

samples from inside the mine were extremely high (19,000 

and 181,000 μg/L); therefore, the dissolved zinc concentrations were superimposed on the light stable isotope graph to 

ANIMAS METEORIC WATER LINE

-130

-125

-120

-115

-110

-105

-100

-95

-90

-18 -17.5 -17 -16.5 -16 -15.5 -15 -14.5 -14 -13.5 -13

Other sites in Animas River watershed May Day mine pool and drip

Cement Creek May Day reach well points

Fracture spring 7,554 Ferricrete spring 7,612

EXPLANATION

-118

-116

-114

-112

-110

-108

-106

-104

-102

-16 -15.5 -15 -14.5 -14

May Day sites

MIXTURE OF 

SOURCES

966 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Effects of May Day Mine Site in Cement Creek Basin 967

Figure 15. Oxygen and hydrogen isotopes of water and dissolved zinc concentrations for sites affecting 

May Day reach. VSMOW, Vienna Standard Mean Ocean Water; μg/L, micrograms per liter. Dashed line, linear 

regression of samples collected in the May Day reach.

determine whether the different isotope values might have been 

affected by the mine water (fig. 15). The dissolved zinc concentrations were elevated in water from fracture spring 7,554 

and the May Day reach well points; therefore, water from these 

sites might have been affected by the May Day mine site. This 

is further evidence that water from fracture spring 7,554 is a 

mixture of water from the May Day mine and the well points.

To further describe sources of water in the May Day 

reach and determine whether water from the May Day mine 

discharges to Cement Creek, principal components analysis was done on the water samples. Although the processes 

contributing to patterns might not be described through PCA, 

different groups (or sources) can be identified. Patterns were 

displayed using scaled principal component loadings. In a 

loading plot each point corresponds to a sample, and the 

coordinates are given by the scaled principal component 

loading of the samples. The plot indicates the similarities and 

correlations between samples (Varmuza, 2001). PCA analysis of samples in the reach affected by the May Day mine 

reveals a mixture of sources (fig. 16): (1) Cement Creek and 

other streams, (2) ground water such as fracture spring 7,554, 

(3) ground water from the Topeka Gulch alluvial fan and 

ferricrete spring, (4) ground water from the well points, and 

(5) May Day mine water. Water from fracture spring 7,554 

plots in the middle of the groups (fig. 16) and might be a mixture of waters from the different sources. In addition, because 

of the high zinc concentrations (fig. 15), fracture spring 7,554 

might be affected by water from the May Day mine.

-120

-115

-110

-105

-100

-95

-16.5 -16 -15.5 -15 -14.5 -14 -13.5 -13

Well point 7,260

Well point 7,440

Well point 7,495

Braided channel 7,542

Ferricrete spring 7,612

Topeka Gulch alluvial fan spring 7,891

2,000 g/L

20,000 g/L

Diameter of circle represents 

 dissolved zinc concentration

 (extremely high concentration

 of mine water not shown to scale)

TREND OF SAMPLES FROM OTHER STUDIES IN THE WATERSHED

May Day mine pool and drips (19,000 and 181,000 g/L)

Cement

Creek

Fracture spring 7,554

7,561 Topeka Gulch at mouth

Left bank seep 7,537

Braided channel 7,545

EXPLANATION

Well point 7,527
Mineral Saturation

Alternating increases and decreases of constituent mass 

were evident in the study reach. Increases were explained by 

inflows or sources. Decreases, however, were more difficult 

to explain, and might have been caused by loss of constituent mass through physical, chemical (mineral saturation), 

or biological processes (Broshears and others, 1996). To 

describe mineral saturation, equilibrium geochemical modeling was done for each stream sample in the study reach 

using WATEQ4F (Ball and Nordstrom, 1991) and PHREEQC 

(Parkhurst and Appelo, 1999).

The saturation index (SI) is the log of the ion-activity 

product divided by the mineral solubility. Negative SI represents undersaturation of the mineral species, where the species 

would remain in the dissolved phase, and positive SI represents supersaturation of the mineral species, where the species 

would precipitate from the dissolved phase into the solid 

or colloidal phase. Iron and sulfate species were examined 

because of the predominance of these constituents in waters of 

the study area. Aluminum species also were examined because 

of the mixing of Cement Creek (pH ≈ 4) with circumneutral 

Illinois Gulch water in the tracer study reach. Regarding iron 

sulfate minerals, schwertmannite (Fe3+

16O16(OH)12(SO4

)

2

) has 

-4

-2

0

2

4

Lead

 SCALED PRINCIPAL COMPONENT 2 LOADINGS

 SCALED PRINCIPAL COMPONENT 1 LOADINGS

-4 -2 0 2 4 6 8 10

-4 -2 0 2 4 6 8 10

-4

-3

-2

-1

0

1

2

3

-3

-1

1

3

4

Zinc

Strontium

Nickel

Sodium

Magnesium

Iron

Copper

Cadmium

H+

Aluminum

Manganese

Sulfate

Calcium

2

H

18O

Chloride

Topeka

Gulch

7,561

Fracture 

spring 

7,554

May Day

mine 

pool

SCALED PRINCIPAL COMPONENT 2 SCORES

SCALED PRINCIPAL COMPONENT 1 SCORES

STREAMS

GROUND WATER

Cement

Creek

Ferricrete

spring

7,612

Topeka 

Gulch 

alluvial fan 

spring

7,891

Well

point

7,260

Braided

channel

7,545

Well

point

7,495

Well

point

7,440

Well

point

7,527

Braided

channel

7,542

GROUND WATER

GROUND WATER

MIXTURE OF 

SOURCES

Figure 16. Principal components analysis, including dissolved constituents and isotopes, showing groups 

of inflows and stream sites in study reach affected by May Day mine.

968 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Effects of May Day Mine Site in Cement Creek Basin 969

been found in bed sediment from Cement Creek (Desborough 

and others, 2000); however, the schwertmannite mineral species is not in the WATEQ4F database; therefore, a modified 

PHREEQC database was used to model schwertmannite. A log 

activity of –18.0 for schwertmannite as determined by Bigham 

and others (1996) was added to the WATEQ4F thermodynamic 

database (Ball and Nordstrom, 1991) used with PHREEQC. 

Geochemical modeling results indicated that the SI of 

schwertmannite was positive throughout the entire length of 

the study reach (fig. 17). The SI of schwertmannite decreases 

between reach distance 6,638 and 6,740, which may be caused 

by inflow of low-pH water. Similarly, the SI of schwertmannite fluctuates in the reach affected by the May Day inflows 

and the May Day alluvial fan. Ferrihydrite (Fe2

O3·0.5(H2O)), 

aluminum sulfate (KAl3

(SO4)

2

(OH)6), and aluminum silicate 

(Al2

Si4O10(OH)2) became supersaturated in the mixing zone of 

Cement Creek and Illinois Gulch (fig. 17). The large dissolved 

sulfate load (fig. 10B) and high-pH water (fig. 6) entering 

Cement Creek from Illinois Gulch caused supersaturation of 

these minerals. Mineral saturation fluctuated in the May Day 

reach, owing to inflow of low-pH water (fig. 17).

Alternating increases and decreases of dissolved 

constituent loads (figs. 11–13) may have resulted from 

adsorption and coprecipitation of dissolved constituents in 

the presence of actively forming colloids. Desborough and 

others (2000) identified schwertmannite in sediment from the 

Cement Creek streambed, which included a sample collected 

downstream from the Yukon tunnel. Total digestion of the 

solid-phase sample showed copper, lead, and zinc concentrations of 45, 450, and 140 parts per million, respectively. These 

data indicate that iron-sulfate precipitates adsorb or coprecipitate metals. These processes are reflected by a decrease 

of dissolved constituent loads in stream reaches of actively 

forming colloids. When low-pH water enters the study reach, 

these colloids may dissolve, thereby releasing the metals into 

solution and increasing the dissolved constituent load.

Saturation of ferrihydrite, aluminum sulfate, and aluminum 

silicate minerals is probably present in ground water beneath 

the May Day mine site. A linear feature—or zone of fractured 

rock—originates in the Ohio Peak area northwest of the May 

Day mine site, and the linear feature passes beneath the mine 

site, continuing along the lower reach of Cement Creek (Smith 

and others, 2001). This linear feature acts as a conduit for 

transport of ground water beneath the May Day mine. Ground 

water from the Ohio Peak area mixes with the acidic and 

constituent-rich water from inside the mine. Using PHREEQC 

(Parkhurst and Appelo, 1999), geochemical modeling was done 

mixing upgradient water from Topeka Gulch (Wright and Janik, 

1995) with water from inside the May Day mine to produce the 

chemical composition of water that discharges at fracture spring 

7,554 in the tracer study reach. The modeling indicated that 

about 25–45 percent of the dissolved constituents at fracture 

spring 7,554 resulted from upgradient sources. Minerals that 

were supersaturated with respect to the solution included ferrihydrite, gibbsite, goethite, jarosite, illite, and aluminum silicate. 

If these solid-phase minerals were, in fact, precipitating colloids 

in the subsurface before discharging to fracture spring 7,554, 

this may have contributed to the increases of total constituent 

concentrations and loads in the reach affected by the May Day 

mine (figs. 7–10).

Aluminum silicate [Al2Si4O10(OH)2]

EXPLANATION

Ferrihydrite [Fe2O3 0.5(H2O)]

Schwertmannite [Fe16O16(OH)12(SO4)

2]

MINERAL SPECIES

Aluminum sulfate [KAl3(SO4)

2(OH)6]

GULCH

OHIO GULCH

INFLOWS

SUPERSATURATION OF MINERAL SPECIES

MAY DAY

UNDERSATURATION OF MINERAL SPECIES ILLINOIS 

TOPEKA

GULCH

ALLUVIAL

FAN

-10

-8

-6

-4

-2

0

2

4

6

8

10

6,380 6,580 6,780 6,980 7,180 7,380 7,580 7,780 7,980 8,180

REACH DISTANCE, IN METERS

SATURATION INDEX OF MINERAL SPECIES

·

Figure 17. Longitudinal stream profile of saturation index for selected mineral species in 

water samples from study reach.
Summary and Conclusions

The tracer-injection study in a reach of Cement Creek 

showed sources of dissolved constituents to the study reach. 

These sources included inflows from an unnamed mine 

upstream from Illinois Gulch, Illinois Gulch, the Yukon tunnel, 

the May Day mine, and diffuse ground water. The increase in 

discharge was the greatest where Illinois Gulch enters Cement 

Creek. Only a slight discharge increase was evident in the 

reach affected by the May Day mine. The changes in pH were 

most noticeable downstream from Illinois Gulch owing to the 

large inflow of circumneutral pH water. Plotting the data on 

longitudinal stream profiles indicated alternating increases and 

decreases of dissolved constituent concentrations in the study 

reach. Concentration increases generally indicated inflows of 

constituent-rich water from mine sites or ground water, and 

concentration decreases generally indicated dilution by large 

inflows or adsorption onto iron precipitates. Total constituent 

(or unfiltered) concentrations increased and decreased through 

the reach, and the total constituent concentrations most noticeably increased at the May Day mine inflows, possibly indicating inflows of constituent-rich water in the reach affected by 

the May Day mine.

Alternating increases and decreases of dissolved and total 

constituent loads were noted in the study reach. Plotting longitudinal profiles of the cumulative instream loads in the study 

reach allowed for observation of the loads that might result if no 

attenuation took place in the stream. Large differences observed 

between the cumulative instream load and the total load for iron 

and sulfate indicated that geochemical reactions were taking 

place in the study reach. Decreases of dissolved constituent 

loads indicated precipitation of colloids. Total constituent loads 

increased in the May Day reach, indicating inflow of iron and 

aluminum supersaturated ground water from the linear feature 

beneath the May Day mine site. Even though the Yukon tunnel 

is a much larger mine, the loads from the May Day reach were 

sometimes larger than loads from the Yukon reach, possibly 

due to the linear feature that transports ground water beneath 

the May Day site. At the end of the study reach, cumulative 

inflow loads were much less than the cumulative instream 

loads, indicating the effect of diffuse ground-water sources in 

the study reach (“unsampled load” in Kimball and others, this 

volume). The change in dissolved and total loads through the 

course of the longitudinal stream profiles indicated the gains 

and losses of mass in the study reach. Some of the losses were 

the result of nonconservative behavior of constituents.

Study of oxygen and hydrogen light stable isotopes 

of water samples indicated different sources of water in the 

May Day reach compared to that of other samples collected 

in the Animas River watershed study area. The reason for isotopic fractionation of the May Day inflow water is uncertain; 

however, the fractionation might be related to water-rock 

interaction or to ground-water flow paths from different 

source areas discharging into Cement Creek through fractures. 

Because of the extremely high dissolved zinc concentrations 

in water from the May Day mine (as high as 181,000 μg/L), 

the dissolved zinc concentrations combined with light stable 

isotope data indicated that the well-point and seep samples 

in the May Day reach were probably affected by the mine. 

Grouping of samples by principal component analysis of the 

dissolved constituent data also indicated that these samples 

are distinct chemically and isotopically, and water from fracture spring 7,554 may be a mixture of both sources.

In conclusion, water from the inactive May Day mine 

and its waste-rock pile appears to contribute to Cement Creek. 

Even though the May Day mine has no perennial discharge, 

and the water inside the mine may only be ephemeral, the 

data indicate that the mine affects the streamflow despite no 

obvious contaminant flow path from the mine to the stream. 

Compared to the constituent loads present in Cement Creek 

at the upstream end of the study reach, the May Day reach 

only contributes a small percentage of loading. In addition, 

loads also entered the study reach from the Topeka Gulch alluvial fan downstream from the May Day site. The mass-loading 

study helped quantify these loading contributions.

References Cited

Ball, J.W., and Nordstrom, D.K., 1991, User’s manual for 

WATEQ4F, with revised thermodynamic data base and test 

cases for calculating speciation of major, trace, and redox 

elements in natural waters: U.S. Geological Survey OpenFile Report 91–183, 189 p.

Bigham, J.M., Schwertmann, Udo, Traina, S.J., Winland, 

R.L., and Wolf, M., 1996, Schwertmannite and the chemical modeling of iron in acid sulfate waters: Geochimica et 

Cosmochimica Acta, v. 60, p. 2111–2121.

Broshears, R.E., Runkel, R.L., Kimball, B.A., Bencala, K.E., 

and McKnight, D.M., 1996, Reactive solute transport in an 

acidic stream—Experimental pH increase and simulation of 

controls on pH, aluminum, and iron: Environmental Science 

and Technology, v. 30, p. 3016–3024.

Campbell, D.L., and Fitterman, D.V., 2000, Geoelectrical 

methods for investigating mine dumps, in ICARD 2000; 

Proceedings of the Fifth International Conference on Acid 

Rock Drainage, Volume 2: Society for Mining, Metallurgy, 

and Exploration, Inc., p. 1513–1523.

Craig, Harmon, 1961, Isotopic variations in meteoric waters: 

Science, v. 133, p. 1702–1703.

Daultrey, Stu, 1976, Principal components analysis: Concepts 

and techniques in modern geography 8, Institute of British 

Geographers, 50 p.

970 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Effects of May Day Mine Site in Cement Creek Basin 971

Desborough, G.A., Leinz, R.W., Sutley, S.J., Briggs, P.H., 

Swayze, G.A., Smith, K.S., and Breit, G.N., 2000, Leaching studies of schwertmannite-rich precipitates from the 

Animas River headwaters, Colorado, and Boulder River 

headwaters, Montana: U.S. Geological Survey Open-File 

Report 00–004, 16 p.

Edwards, T.K., and Glysson, D.G., 1988, Field methods for 

measurement of fluvial sediment: U.S. Geological Survey 

Open-File Report 86–531, 118 p.

Garrels, R.M., and Christ, C.L., 1965, Solutions, minerals, 

and equilibria: San Francisco, Freeman, Cooper & Company, 450 p.

Graf, W.H., 1971, Hydraulics of sediment transport: New York, 

McGraw-Hill, 513 p.

Grundy, W.D., and Miesch, A.T., 1987, Brief descriptions 

of STATPAC and related statistical programs for the IBM 

personal computer: U.S. Geological Survey Open-File 

Report 87–411–A, 34 p.

Hageman, P.L., and Briggs, P.H., 2000, A simple field leach 

test for rapid screening and qualitative characterization 

of mine waste dump material on abandoned mine lands, 

in ICARD 2000; Proceedings of the Fifth International 

Conference on Acid Rock Drainage, Volume 2: Society for 

Mining, Metallurgy, and Exploration, Inc., p. 1463–1475.

Hein, A.S., and Fitterman, D.V., 1998, Topographic surveys 

of selected mine dumps near Silverton and Leadville, Colorado: U.S. Geological Survey Open-File Report 98–588, 

4 p.

Hoefs, Jochen, 1987, Stable isotope geochemistry: New York, 

Springer-Verlag, 241 p.

Joreskog, K.G., Klovan, J.E., and Reyment, R.A., 1976, Geological factor analysis: New York, Elsevier, 178 p.

Kimball, B.A., 1997, Use of tracer injections and synoptic 

sampling to measure metal loading from acid mine drainage: U.S. Geological Survey Fact Sheet FS–245–96, 4 p.

Kimball, B.A., Bencala, K.E., and Runkel, R.L., 2000, 

Quantifying the effects of metal loading from mine drainage, in ICARD 2000; Proceedings of the Fifth International 

Conference on Acid Rock Drainage, Volume 2: Society for 

Mining, Metallurgy, and Exploration, Inc., p. 1381–1387.

Kimball, B.A., Runkel, R.L., Walton-Day, Katherine, and 

Bencala, K.E., 2002, Assessment of metal loads in watersheds affected by acid mine drainage by using tracer 

injection and synoptic sampling—Cement Creek, Colorado, 

U.S.A.: Applied Geochemistry, v. 17, p. 1183–1207.

Mast, M.A., Wright, W.G., and Leib, K.J., 1998, Comparison 

of surface-water chemistry in undisturbed and miningimpacted areas of the Cement Creek watershed, Colorado,

in Nimick, D.A., and von Guerard, P.B., eds., Science for 

watershed decisions on abandoned mine lands—Review of 

preliminary results, Denver, Colorado, February 4–5, 1998: 

U.S. Geological Survey Open-File Report 98–297, p. 38.

Mast, M.A., Evans, J.B., Leib, K.J., and Wright, W.G., 2000, 

Hydrologic and water-quality data at selected sites in the 

upper Animas River watershed, southwestern Colorado, 

1997–99: U.S. Geological Survey Open-File Report 00–53, 

20 p., 1 plate, CD-ROM.

McKnight, D.M., Kimball, B.A., and Bencala, K.E., 1988, 

Photoreduction of hydrous iron oxides in acidic mountain 

streams in Colorado: U.S. Geological Survey Open-File 

Report 87–764.

Muir, K.S., and Coplen, T.B., 1981, Tracing ground-water 

movement by using the stable isotopes of oxygen and 

hydrogen, upper Penitencia Creek alluvial fan, Santa 

Clara, California: U.S. Geological Survey Water-Supply 

Paper 2075, 18 p.

Nordstrom, D.K., and Ball, J.W., 1986, The geochemical 

behavior of aluminum in acidified waters: Science, v. 232, 

p. 54–56.

Parkhurst, D.L., and Appelo, C.A.J., 1999, User’s guide to 

PHREEQC (version 2), a computer program for speciation, batch-reaction, one-dimensional transport, and inverse 

geochemical calculations: U.S. Geological Survey WaterResources Investigations Report 99–4259, 312 p.

Plumlee, G.S., Smith, K.S., Montour, M.R., Ficklin, W.H., and 

Mosier, E.L., 1999, Geologic controls on the composition 

of natural waters and mine waters draining diverse mineraldeposit types, in Filipek, L.H., and Plumlee, G.S., eds., The 

environmental geochemistry of mineral deposits—Part B, 

Case studies and research topics: Reviews in Economic Geology, v. 6B, Society of Economic Geologists, Inc., p. 373–432.

Runkel, R.L., and Kimball, B.A., 2002, Evaluating remedial 

alternatives for an acid mine drainage stream—Application 

of a reactive transport model: Environmental Science and 

Technology, v. 36, no. 5, p. 1093–1101.

Schemel, L.E., Kimball, B.A., and Bencala, K.E., 2000, Colloid formation and metal transport through two mixing 

zones affected by acid mine drainage near Silverton, Colorado: Applied Geochemistry, v. 15, no. 7, p. 1003–1018.

Smith, B.D., Campbell, D.C., and Wright, W.G., 2001, Using 

resistivity to map acidic waters at the Mayday mine, Silverton, Colorado: Environmental and Engineering Geophysical 

Society, Proceedings of the Symposium on the Application 

of Geophysics to Engineering and Environmental Problems, 

March 4–7, 2001, Denver, Colo., paper 142.
Smith, B.D., McCafferty, A.E., and McDougal, R.R., 2000, 

Utilization of airborne magnetic, electromagnetic, and 

radiometric data in abandoned mine land investigations, 

in ICARD 2000; Proceedings of the Fifth International 

Conference on Acid Rock Drainage, Volume 2: Society for 

Mining, Metallurgy, and Exploration, Inc., p. 1552–1559.

Smith, K.S., Ramsey, C.A., and Hageman, P.L., 2000, Sampling strategy for rapid screening of mine-waste dumps on 

abandoned mine lands, in ICARD 2000; Proceedings of 

the Fifth International Conference on Acid Rock Drainage, 

Volume 2: Society for Mining, Metallurgy, and Exploration, 

Inc., p. 1453–1461.

Varmuza, K., 2001, Applied chemometrics—From chemical 

data to relevant information: Proceedings of the 1st Conference on Chemistry, Cairo University, March 6–9, 2000, 

Cairo, Egypt.

Walton-Day, Katherine, Runkel, R.L., Kimball, B.A., and 

Bencala, K.E., 2000, Application of the solute-transport 

models OTIS and OTEQ and implications for remediation in 

a watershed affected by acid mine drainage, Cement Creek, 

Animas River Basin, Colorado, in ICARD 2000; Proceedings of the Fifth International Conference on Acid Rock 

Drainage, Volume 1: Society for Mining, Metallurgy, and 

Exploration, Inc., p. 389–399.

Webster, J.G., Nordstrom, D.K., and Smith, K.S., 1994, 

Transport and natural attenuation of Cu, Zn, As, and Fe in 

the acid mine drainage of Leviathan and Bryant Creeks, in

Alpers, C.N., and Blowes, D.W., eds., Environmental geochemistry of sulfide oxidation: American Chemical Society Symposium Series 550; Washington, D.C., American 

Chemical Society, p. 244–260.

Wright, W.G., and Janik, C.J., 1995, Naturally occurring 

and mining-affected dissolved metals in two subbasins of 

the Upper Animas River Basin, southwestern Colorado: 

U.S. Geological Survey Fact Sheet FS–243–95, 4 p.

Wright, W.G., Leib, K.J., and Mast, M.A., 1998, Effects of 

selected mine dump piles on dissolved-constituent loads in 

the Cement Creek basin, upper Animas River watershed, 

Colorado—A preliminary assessment, in Nimick, D.A., and 

von Guerard, P.B., eds., Science for watershed decisions 

on abandoned mine lands—Review of preliminary results, 

Denver, Colorado, February 4–5, 1998: U.S. Geological 

Survey Open-File Report 98–297, p. 43.

Wyrick, G.G., and Borchers, J.W., 1981, Hydrologic effects 

of stress-relief fracturing in an Appalachian valley: 

U.S. Geological Survey Water-Supply Paper 2177, 51 p.

972 Environmental Effects of Historical Mining, Animas River Watershed, Colorado