U.S. Department of the Interior

U.S. Geological Survey

USGS

Scientific Investigations Report 2005–5011

Stream-Sediment Geochemistry in Mining-Impacted 

Streams: Sediment Mobilized by Floods in the Coeur 

d’Alene-Spokane River System, Idaho and Washington
Cover. South Fork of the Coeur d’Alene River at Kellogg, Idaho, near peak streamflow at approximately 10 a.m. P.s.t. on December 23, 1933. Major 

damage occurred to towns, transportation infrastructure, and ore-concentration-mill facilities in the Coeur d’Alene Mining District from this flood 

event, estimated to be the third largest since mining began in 1885. Data on sediment mobilized by the second-largest historical flood (in February 

1996) and other 1990s flood events are discussed in this report. The largest historical flood in the Coeur d’Alene River basin occurred in January 

1974. Photograph by the Washington National Guard; view eastward (upriver).
Stream-Sediment Geochemistry in MiningImpacted Streams: Sediment Mobilized by 

Floods in the Coeur d’Alene-Spokane River 

System, Idaho and Washington

By Stephen E. Box, Arthur A. Bookstrom, and Mohammed Ikramuddin

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2005–5011
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2005

For sale by U.S. Geological Survey Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

This report and any updates to it are available online at:

http://pubs.usgs.gov/sir/2005/5011/

For additional information write to:

U.S. Geological Survey

Box 25046, Mail Stop 421, Denver Federal Center

Denver, CO 80225–0046

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endorsement of the U.S. Government.

Cataloging-in-publication data are on file with the Library of Congress (URL http://www.loc.gov/).

Produced in the Western Region, Menlo Park, California

Manuscript approved for publication, January 20, 2005

Text edited by George Havach

Layout and design by Sara Boore and Susan Mayfield
 iii

Contents

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

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

Background ................................................................................................ 4

Description of the Drainage Basin ............................................................... 4

Description of the Floods of 1995, 1996, and 1997 ............................................. 5

Sampling and Analytical Methods ..................................................................... 8

Results ...................................................................................................... 12

Downstream Trends in Suspended-Sediment Concentration and Load ..................... 12

Downstream Trends in the Metal Contents of Suspended Sediment ........................ 13

Downstream Trends in the Metal Loads in Suspended Sediment ........................... 16

Downstream Trends in the Metal Contents of Streambank Flood Deposits .................. 16

Interelement Correlations in Flood Sediment ................................................... 18

Discussion ................................................................................................ 23

Sources of Metal-Enriched Sediment Mobilized During Flooding and the Processes 

Responsible for Elemental Distributions ...................................................... 23

Conclusions ................................................................................................ 31

Acknowledgments ....................................................................................... 32

References Cited .......................................................................................... 32

Figures

 1–3. Maps of:

1. Eastern part of the Coeur d’Alene-Spokane River system in northern Idaho, 

showing locations of sampling sites for suspended sediment during peak 

streamflows in 1996 and 1997 ............................................................ 2

2. Western part of the Coeur d’Alene-Spokane River system in northern Idaho 

and eastern Washington, showing locations of sampling sites for suspended 

sediment during peak streamflows in 1997 .......................................... 3

3. Eastern part of the Coeur d’Alene-Spokane River system in northern Idaho, 

showing locations of sampling sites for sediment deposited on streambanks 

and in marshes during peak streamflows in 1995 and 1996 ........................ 5

 4. Schematic diagram showing longitudinal stream gradient of the Coeur d’AleneSpokane River system from upstream, east of Wallace, Idaho, to downstream, 

west of Spokane, Wash. ..................................................................... 6

 5–9. Hydrographs of mean daily streamflow at U.S. Geological Survey gaging stations on:

5. The Coeur d’Alene and Spokane Rivers during water years 1995, 1996, and 1997 ... 7

6. The Coeur d’Alene River at Cataldo, Idaho, during high-flow event of 

February 20, 1995, with river-surface elevation at U.S. Geological Survey 

gaging station shown for comparison ................................................ 8

7. The Coeur d’Alene River for 30-day period surrounding high-flow event of 

February 9, 1996, with mean daily river-surface elevations at U.S. Geological 

Survey gaging station shown for comparison ....................................... 9

8. The South Fork of the Coeur d’Alene River at Elizabeth Park, Idaho, for 24-day 

period centered on high-flow event of January 1, 1997 .............................. 10
iv 

9. The Coeur d’Alene and Spokane Rivers for 120-day period in spring 1997, with 

mean daily river-surface elevations at U.S. Geological Survey gaging station 

shown for comparison .................................................................. 11

 10. Logarithmic plots of suspended-sediment concentrations in grab samples 

collected from the Coeur d’Alene and Spokane Rivers and their tributaries, and 

daily suspended-sediment loads at sampling sites for which mean daily streamflow 

could be extrapolated from nearby U.S. Geological Survey gaging stations, versus 

downstream distance from Mullan, Idaho, during high flow events in 1996 and 1997 ... 14

 11. Plots of Pb, Zn, Fe, and Mn contents in samples of suspended sediment collected 

from the Coeur d’Alene and Spokane Rivers and their tributaries and in samples of 

sediment deposited in flood-plain marshes versus downstream distance from 

Mullan, Idaho, during high-flow events in 1996 and 1997 ................................. 15

 12. Logarithmic plots of calculated daily loads of Pb and Zn in suspended sediment 

at selected sampling sites versus downstream distance from Mullan, Idaho, during 

high-flow events in 1996 and 1997 ............................................................ 17

 13. Plots of Pb, Zn, Fe, and Mn contents in samples of streambank sediment 

deposited along the South Fork and main stem of the Coeur d’Alene River versus 

downstream distance from Mullan, Idaho, during February 1995 and February 1996 

high-flow events .............................................................................. 18

 14. Schematic cross section of river channel and natural levee during overbank 

flooding .......................................................................................... 19

15–20. Plots of:

15. Mn versus Fe contents and Zn versus Pb contents in flood-sediment samples 

grouped by sample media, river reach, and flood year ........................... 20

16. Pb versus Fe contents and Pb versus Mn contents in flood-sediment samples 

grouped by sample media, river reach, and flood year ........................... 21

17. Zn versus Fe contents and Zn versus Mn contents in flood-sediment samples 

grouped by sample media, river reach, and flood year ........................... 22

18. Cd versus Zn contents, Ag versus Pb contents, Sb versus Pb contents, Ag 

versus Sb contents, As versus Fe contents, and Cu versus Fe contents in floodsediment samples grouped by sample media, river reach, and flood year ...... 24

19. Zn versus Pb contents in potential flood-sediment source materials in and 

along the South Fork of the Coeur d’Alene River, northern Idaho ............... 28

20. Zn versus Pb contents in potential flood-sediment source materials in and 

along the main stem of the Coeur d’Alene River downstream from 

Cataldo, Idaho ........................................................................... 29

 21. Schematic cross sections of the lower Coeur d’Alene River valley, northern Idaho, 

during overbank flooding in February 1996 and May 1997 ................................. 30

Tables

1. Analytical data for samples of suspended sediment collected from the Coeur d’AleneSpokane River system, northern Idaho and eastern Washington, during high-water 

events in 1996 and 1 ................................................................................. 36

2. Analytical data for samples of overbank sediment from the South Fork and main stem 

of the Coeur d’Alene River, northern Idaho, deposited during high-water events in 1995 

and 1996 ............................................................................................. 46

3. Daily metal loads in suspended sediment at selected sampling sites in the Coeur d’AleneSpokane River system, northern Idaho and eastern Washington .............................. 51
Stream-Sediment Geochemistry in Mining-Impacted 

Streams: Sediment Mobilized by Floods in the Coeur 

d’Alene-Spokane River System, Idaho and Washington

Abstract

Environmental problems associated with the dispersion 

of metal-enriched sediment into the Coeur d’Alene-Spokane 

River system downstream from the Coeur d’Alene Mining 

District in northern Idaho have been a cause of litigation since 

1903, 18 years after the initiation of mining for lead, zinc, 

and silver. Although direct dumping of waste materials into 

the river by active mining operations stopped in 1968, metalenriched sediment continues to be mobilized during times of 

high runoff and deposited on valley flood plains and in Coeur 

d’Alene Lake (Horowitz and others, 1993). To gauge the geographic and temporal variations in the metal contents of flood 

sediment and to provide constraints on the sources and processes responsible for those variations, we collected samples of 

suspended sediment and overbank deposits during and after 

four high-flow events in 1995, 1996, and 1997 in the Coeur 

d’Alene-Spokane River system with estimated recurrence 

intervals ranging from 2 to 100 years. Suspended sediment 

enriched in lead, zinc, silver, antimony, arsenic, cadmium, and 

copper was detected over a distance of more than 130 mi (the 

downstream extent of sampling) downstream of the mining 

district. Strong correlations of all these elements in suspended 

sediment with each other and with iron and manganese are 

apparent when samples are grouped by reach (tributaries to 

the South Fork of the Coeur d’Alene River, the South Fork of 

the Coeur d’Alene River, the main stem of the Coeur d’Alene 

River, and the Spokane River). Elemental correlations with 

iron and manganese, along with observations by scanning 

electron microscopy, indicate that most of the trace metals 

are associated with Fe and Mn oxyhydroxide compounds. 

Changes in elemental correlations by reach suggest that the 

sources of metal-enriched sediment change along the length of 

the drainage. Metal contents of suspended sediment generally 

increase through the mining district along the South Fork of 

the Coeur d’Alene River, decrease below the confluence of the 

North and South Forks, and then increase again downstream of 

the gradient flattening below Cataldo. Metal contents of suspended sediment in the Spokane River below Coeur d’Alene 

By Stephen E. Box, Arthur A. Bookstrom, and Mohammed Ikramuddin1

Lake were comparable to those of suspended sediment in the 

main stem of the Coeur d’Alene River above the lake during 

the 1997 spring runoff, but with somewhat higher Zn contents. 

Daily suspended-sediment loads were about 100 times larger 

in the 1996 flood (50–100-year recurrence interval) than in the 

smaller 1997 floods (2–5-year recurrence intervals). Significant differences in metal ratios and contents are also apparent between the two flood types. The predominant source of 

suspended sediment in the larger 1996 flood was previously 

deposited, metal-enriched flood-plain sediment, identified by 

its Zn/Pb ratio less than 1. Suspended sediment in the smaller 

1997 floods had metal ratios distinct from those of the floodplain deposits and was primarily derived from metal-enriched 

sediment stored within the stream channel, identified by a 

Zn/Pb ratio greater than 1. Sediment deposited during overbank flooding on the immediate streambank or natural levee of 

the river typically consists of sandy material with metal ratios 

and contents similar to those of the sandy streambed sediment 

in the adjacent river reach. Samples of overbank deposits in 

backlevee marshes collected after the 1996 flood have metal 

ratios similar to those of peak-flow suspended sediment in the 

same river reach, but generally lower metal contents.

Introduction

The South Fork of the Coeur d’Alene River in northern 

Idaho (fig. 1) drains the Coeur d’Alene Mining District, one of 

the world’s largest producers of silver and one of the Nation’s 

largest producers of lead and zinc (Long, 1998). More than 

130 million tons of Pb-Zn-Ag sulfide ores has been mined 

from more than 20 major mines in the district since 1885 

(Long and others, 1998). From the onset of ore production in 

the 1880s to 1968, most of the ore-concentration mills in the 

district piped or flumed pulverized waste material (“tailings”) 

from the concentration process directly into the river, resulting 

in gray opaque river water charged with suspended sediment 

year round (Ellis, 1940). This sediment overloading of the 

river, along with the flat-bottomed topography of the Coeur 

d’Alene River valley and its history of repeated inundation, 

resulted in incorporation of this metal-enriched material into 1

Eastern Washington University, Cheney,Wash.
2 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

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Figure 1. Eastern part of the Coeur d’Alene-Spokane River system in northern Idaho, showing locations of 

sampling sites for suspended sediment during peak streamflow of February 9–10, 1996 (A; red circles), January 

2, 1997 (B; green triangles), and May 19–20, 1997 (C; dark-blue squares). Blue italic numbers, river miles below 

Mullan. See table 1 for analytical data.

stream sediment and flood-plain soils over nearly the entire 

length and breadth of the valley floor from the mining district 

downstream into Coeur d’Alene Lake, a distance of about 60 

mi (Bookstrom and others, 2001). Direct dumping of tailings 

into the river stopped in 1968, when tailings-settling ponds 

became legally required for all active mining operations 

(Long, 1998). Since that time, the river water has substantially 

cleared, and suspended-sediment concentrations are elevated 

only during times of high runoff. Despite this remedial action, 

however, sedimentation rates and metal contents of new sediment deposited in Coeur d’Alene Lake have not decreased 

since 1968 (Horowitz and others, 1995), as previously deposited metal-enriched sediment in the valley continues to be 

remobilized by both physical and chemical processes.

Sediment carried during high-flow events typically is 

physically remobilized from unconsolidated materials within 
the drainage basin, although precipitation of solids and (or) 

ionic sorption onto solids from the dissolved state can also 

occur, owing to changing chemical conditions in the stream. 

Flood-sediment sources consist of erodible materials exposed 

in streambeds, streambanks, and flood plains of the Coeur 

d’Alene-Spokane River system (figs. 1, 2). Although these 

source materials may undergo geochemical changes (weathering) under various surface conditions during the year, 

incorporation of the source materials into the suspended-sediment load is generally dominated by physical processes. The 

elemental composition of a particular flood-sediment sample 

is controlled by the mixture of source materials accessed by 

floodwaters upstream from the sampling site, the degree to 

which the shear stress of the flowing waters can overcome the 

inertia of source particles, and the subsequent sorting (based 

on particle size and density) of the mobilized material by the 

floodwaters. These factors can change during a high-flow 

event, and so suspended-sediment concentrations and their 

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Figure 2. Western part of the Coeur d’Alene-Spokane River system in 

northern Idaho and eastern Washington, showing locations of sampling 

sites for suspended sediment during peak streamflow of May 2, 1997 (A; 

pale-blue diamonds), and May 19–20, 1997 (B; dark-blue squares). Map area 

overlaps western part of map area in figure 1. Blue italic numbers, river 

miles below Mullan, Idaho. See table 1 for analytical data.

Introduction 3
4 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

elemental composition can change accordingly over the duration of the event (Horowitz and others, 1990).

We collected samples of sediment mobilized in the Coeur 

d’Alene-Spokane River system (figs. 1–3) during and after 

four high-flow episodes in 1995, 1996, and 1997 to characterize its elemental composition and downstream variation 

during an individual high-flow event, and its variation between 

different high-flow events. Three sample media were used 

for this study: (1) fine suspended sediment, collected during 

peak flow; (2) sandy sediment deposited on the immediate 

streambank or natural levee of the river during overbank flooding; and (3) fine sediment deposited in backlevee marshes 

at a greater distance from the river channel during overbank 

flooding. These three sample media represent flood-mobilized 

sediment that was sampled on different time scales (instantaneous versus cumulative high-flow event) and with different 

sorting histories (washload sediment in true suspension, levee 

sediment deposited from traction currents, and marsh sediment 

deposited from part of the washload).

In this report, we present the results of chemical analyses 

of flood sediment from the Coeur d’Alene-Spokane River 

system (figs. 1–3) and discuss how the data constrain our 

understanding of the sources and processes that control the 

elemental composition of sediment mobilized during highflow events. We begin by describing the drainage basin in and 

downstream from the mining district and the several sampled 

high-flow events. We compare the downstream variations 

in metal contents and loads for each high-flow event and 

for each sample media. Finally, we discuss the variations in 

elemental composition in terms of their relevance to understanding the variations in flood-sediment sources during highstreamflow events.

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Figure 3. Eastern part of the Coeur d’Alene-Spokane River system in northern Idaho (see fig. 1 for index map), showing locations of sampling sites for sediment deposited on streambanks during peak streamflow of February 21, 1995 (A; 

tan triangles), and for sediment deposited on streambanks (B; green squares) and sediment deposited in marshes (C; 

pink circles) during and after peak streamflow of February 9–10, 1996. See table 2 for analytical data.
Background

Description of the Drainage Basin

The drainage basin of the Coeur d’Alene-Spokane River 

system in northern Idaho and eastern Washington (figs. 1, 2) 

that is impacted by mining can be divided into four reaches. 

The first reach comprises the South Fork and main stem of 

the Coeur d’Alene River between the confluence of the North 

and South Forks and the gradient flattening downstream from 

the town of Cataldo, Idaho. In this reach, the river runs in a 

braided, cobbly channel flanked by a sandy flood-plain surface 

of varying width (0–1 mi). The channel in several segments 

of this reach has been significantly modified with artificial 

riprap banks and levees and is spanned by numerous bridges. 

The second reach comprises the lower Coeur d’Alene River 

from below Cataldo to the delta into Coeur d’Alene Lake at 

Harrison, Idaho. In this reach, the river runs in a deep, sandbottomed channel through a wide (0.3–2.0 mi) marshy valley 

flanked by narrow (avg 0.12 mi wide) natural levees. During 

low-flow periods, the channel in this reach is backflooded by 

the waters of Coeur d’Alene Lake. The third reach comprises the 

main body of Coeur d’Alene Lake, a natural lake that drowns 

a Quaternary river valley. The lake has two main tributaries of 

approximately equal size: the Coeur d’Alene and St. Joe Rivers. 

The lake has relatively steep bedrock walls and water depths of 

as much as 250 ft (Woods and Berenbrock, 1994). The fourth 

reach comprises the Spokane River, which flows westward out 

of the north end of Coeur d’Alene Lake to Spokane, Wash. In 

this reach, the river runs in a cobble- and boulder-filled channel incised into Quaternary glacial-outburst-flood gravel, with 

almost no natural flood plain (Box and Wallis, 2002). A longitudinal plot of the stream gradient of the Coeur d’Alene-Spokane 

River system is shown in figure 4.

The responses of these four river reaches to high-flow 

conditions differ in relation to the valley characteristics. In the 

first reach, where unconstrained by artificial modifications, 

the river occupies a broad channel during times of high runoff, 

with cutbanks of metal-enriched (relative to premining deposits or sediment along unmined tributaries), sandy flood-plain 

deposits. As a result of flood-plain aggradation during the 

first decades of mining activity, very little of what is considered to be the alluvial flood plain along the South Fork of the 

Background 5

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Figure 4. Longitudinal stream gradient of the Coeur d’Alene-Spokane River system from upstream, east of Wallace, Idaho (right) to 

downstream, west of Spokane, Wash. (left; see figs. 1 and 2 for locations). Steep upstream gradient at Wallace gradually decreases 

to just below Cataldo, where waters of Coeur d’Alene Lake backflood lower 28 mi of the Coeur d’Alene River channel. Lake waters 

are impounded by a bedrock constriction on the Spokane River at Post Falls, now augmented by the Post Falls dam.
6 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

Coeur d’Alene River in the mining district was flooded during 

1995–97 high-flow events, even though the February 1996 

flood was one of the three highest flows recorded on the South 

Fork since 1920. During low-flow conditions, water occupies 

only a narrow strip of the high-water channel.

In the second reach, the Coeur d’Alene River fills a narrow, deep channel floored by metal-enriched sand and flanked 

by narrow natural levees and cutbanks of metal-enriched fine 

sand and silt. A wide flood plain of backlevee marshes and 

shallow flood plain lakes is generally connected to the river 

channel by natural or manmade side channels (Bookstrom and 

others, 1999). For most of the year, the channel is backflooded 

by the waters of Coeur d’Alene Lake to a point just below the 

town of Cataldo, Idaho (fig. 1). Current is perceptible only 

during high-flow events; flow velocity reached more than 7 

ft/s during the February 1996 flood (M.A. Beckwith, written 

commun., 1996). The river-surface elevation in this reach is 

controlled both by the flow rate on the Coeur d’Alene River 

upstream at Cataldo and by the surface elevation of Coeur 

d’Alene Lake downstream. Overbank flooding occurs in most 

years, and nearly all of the flood plain was inundated during 

each of the sampling events in this study.

In the third reach, the surface elevation of Coeur d’Alene 

Lake is controlled from mid-June to mid-November by a gated 

dam at Post Falls, Idaho (figs. 2, 4). All the sampling events in 

this study was conducted while the dam gates were wide open, 

at which times the outflow from the lake is restricted by a narrow bedrock gorge at the damsite at Post Falls, such that the 

natural outflow rate is directly correlative with the lake-surface 

elevation. During high-flow events on the main tributaries to 

the lake (Coeur d’Alene and St. Joe Rivers), inflow exceeds 

outflow, causing the lake level to rise until outflow equals 

Figure 5. Hydrograph of mean daily streamflow at U.S. Geological Survey gaging stations on the South Fork of the Coeur d’Alene 

River at Elizabeth Park, Idaho (dark-blue curve), on the Coeur d’Alene River at Cataldo, Idaho (red curve), and on the Spokane River 

at Spokane, Wash. (light-blue curve) during water years 1995, 1996, and 1997 (see figs. 1 and 2 for locations). Arrows denote points 

on hydrograph when samples of flood sediment (suspended sediment during high-flow event and overbank deposits after waning of 

the high-flow event) were collected.

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inflow. As high flow on the tributaries diminishes, outflow 

exceeds inflow and the lake level falls until outflow and 

inflow are equal. Average residence times for lake water were 

calculated for water years 1991 and 1992 at 160 and 325 days, 

respectively (Woods and Beckwith, 1995). The traveltime of 

water (and suspended sediment) from the inlet at Harrison, 

Idaho (fig. 1) to the outlet at Coeur d’Alene, Idaho, during 

high-flow events (for example, the May 1997 flood) is much 

shorter than these average residence times during runoff events 

(on the order of days to weeks), because of faster movement of 

the shallow lake waters (P.F. Woods, written commun., 2000).

In the fourth reach, the Spokane River flows westward 

in a shallow channel incised into coarse Quaternary gravel. 

Most of the channel is occupied even at low water, with almost 

no natural flood plain. Deposits of sand or finer material are 

scarce (except behind the Upriver dam) above Spokane Falls 

(Box and Wallis, 2002). The Upriver dam backs up a small 

reservoir in the incised channel for about 1 mile. No surfacewater tributaries join the Spokane River from the outlet of 

Coeur d’Alene Lake to just west of Spokane Falls, where the 

river turns northward at the inflow of Latah Creek (figs. 2, 4).

Description of the Floods of 1995, 1996, and 1997

Several high-flow events occurred in the Coeur d’AleneSpokane River system (figs. 1, 2) during water years 1995, 1996, 

and 1997 (fig. 5; U.S. Geological Survey, 1996, 1997, 1998). 

Winter (between mid-November and mid-March) high-flow 

events typically result from warm Pacific winter storms (“pineapple express”) that bring a sudden warming to above-freezing 

temperatures and, commonly, heavy rains to northern Idaho. 

Rapid snowmelt produces an abrupt increase in runoff to peak 

Background 7

Figure 6. Hydrograph of mean daily streamflow at U.S. Geological Survey gaging station on the Coeur d’Alene River at Cataldo, 

Idaho (thin line, with scale on left axis), during high-flow event of February 20, 1995, with river-surface elevation at U.S. Geological 

Survey gaging station on the Coeur d’Alene River at Rose Lake, Idaho (thick line, with scale on right axis) shown for comparison. 

Rose Lake gaging station is near upstream end of 28-mi-long backflooded reach of the lower Coeur d’Alene River, where river elevation is controlled both by inflow from river at Cataldo and by lake-surface elevation. Overbank deposits from this high-flow event 

were sampled at six sites (fig. 3A) on February 23, 1995.

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8 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

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Figure 7. Hydrograph of mean daily streamflow at U.S. Geological Survey gaging stations on the South Fork 

of the Coeur d’Alene River at Elizabeth Park, Idaho (A), and on main stem of the Coeur d’Alene River at Cataldo, 

Idaho (B; thin line, scale on left axis), for 30-day period surrounding the high-flow event of February 9, 1996, with 

mean daily river-surface elevations at U.S. Geological Survey gaging station on the Coeur d’Alene River at Rose 

Lake, Idaho (B; thick line, scale on right axis) shown for comparison (see fig. 1 for locations). Arrows denote 

points on hydrograph when suspended-sediment samples were collected. Overbank deposits from this event 

were sampled at 18 sites (figs. 3B, 3C) after floodwaters receded in March and April 1996.
flow from winter base-level flows; an equally abrupt cooling to 

below-freezing temperatures after storm passage returns the runoff to midwinter low-flow levels more gradually. The February 

1995, February 1996, and January 1997 high-flow events were 

all of this abrupt type. Spring runoff (mid-March to mid-June) 

results from melting of the winter snowpack. The gradual, sustained snowmelt produces a broad runoff high, on which spring 

rainstorms superimpose sharper runoff peaks. The spring runoff 

of April through June 1997 was of this more gradual type.

The February 1995 flood (fig. 6) was the highest flow 

on the Coeur d’Alene River recorded since 1982 and the first 

peak flow greater than 15,000 ft3/s recorded since April 1991. 

Instantaneous peak flow on February 20 for the main stem of 

the Coeur d’Alene River at Cataldo, Idaho (fig. 1) was 35,200 

ft3/s, the eighth-highest peak flow recorded since 1920, with 

a calculated recurrence interval at Cataldo of about 10 years 

(Kjelstrom, 1996). The water-surface elevation of the lakeinfluenced lower Coeur d’Alene River at the Rose Lake gage 

below Cataldo rose 11 ft in 3 days (fig. 6), attaining a maximum 

elevation of 10 ft above summer lake-surface elevation (2,125 ft 

above sea level) on February 21 and a maximum current velocity greater than 5 ft/s (M.A. Beckwith, written commun., 1996). 

Almost no overbank flooding occurred along the South Fork, 

and only minor overbank flooding occurred on the main stem of 

the Coeur d’Alene River above Cataldo. Most of the flood plain 

below Cataldo was inundated, except for that part south of the 

river protected by a railroad embankment and the crests of some 

natural levees in the upper half of the valley below Cataldo. 

Streambank flood deposits were sampled at six sites on the 

Coeur d’Alene River below Cataldo through the upper half of 

the lower Coeur d’Alene Valley on February 23 (fig. 3A).

The February 1996 flood (fig. 7) had the second-highest 

flow on the Coeur d’Alene River recorded at the U.S. Geological Survey gaging station at Cataldo (fig. 1) since gaging 

began in 1920, surpassed only by the flood of January 1974 

(Beckwith and others, 1996). Using data from the Spokane 

Sampling and Analytical Methods 9

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Figure 8. Hydrograph of mean daily streamflow at U.S. Geological Survey gaging station on the South Fork of the Coeur d’Alene 

River at Elizabeth Park, Idaho (fig. 1), for 24-day period centered on the high-flow event of January 1, 1997. Arrow denotes point on 

hydrograph when suspended-sediment samples were collected.
10 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

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Figure 9. Hydrograph of mean daily streamflow at U.S. Geological Survey gaging stations on the South Fork of the 

Coeur d’Alene River at Elizabeth Park, Idaho (A), and on main stem of the Coeur d’Alene River at Cataldo, Idaho (B; thin 

line, with scale on left axis) and on the Spokane River at Spokane, Wash. (B; thick gray line, with scale on left axis), for 

120-day period in spring 1997, with mean daily river-surface elevations at U.S. Geological Survey gaging station on the 

Coeur d’Alene River at Rose Lake, Idaho (B; thick black line, scale on right axis) shown for comparison (see figs. 1 and 

2 for locations). Arrows denote points on hydrograph when suspended-sediment samples were collected.
River gage at Spokane (fig. 2), with a period of record dating back to 1891, the February 1996 flood apparently had the 

second-highest peak flow on the Coeur d’Alene River since at 

least 1891, soon after production began in the Coeur d’Alene 

Mining District. Instantaneous peak flow on February 9 for the 

South Fork of the Coeur d’Alene River at Elizabeth Park (fig. 

1) was 9,600 ft3/s and for the main stem at Cataldo was 68,300 

ft3/s, with a calculated recurrence interval at Cataldo of about 

100 years (Kjelstrom, 1996). The water-surface elevation of the 

lake-influenced lower Coeur d’Alene River at Rose Lake (fig. 

1) rose 17 ft in 4 days (fig. 7B), attaining a maximum elevation of 14 ft above summer lake-surface elevation on February 10 and a maximum current velocity in the channel greater 

than 7 ft/s on February 9 (Mike Beckwith, written commun., 

1996). Minor overbank flooding occurred along the South 

Fork, but major overbank flooding occurred on the main stem 

of the Coeur d’Alene River above Cataldo, causing extensive 

flood damage in the towns of Cataldo and Kingston. The 

entire flood plain below Cataldo was inundated, including the 

railroad embankment, which was washed out in many places. 

Suspended sediment was sampled at 10 sites on the South Fork 

and main stem of the Coeur d’Alene River during the 24 hours 

surrounding the peak flow on February 9 and 10 (fig. 1A). 

Sediment deposited on streambanks and in marshes during the 

February flood was sampled at 18 sites along the same channel 

segment on March 28 and April 12 (figs. 3B, 3C).

The January 1997 high-flow event (fig. 8) was much 

smaller than the previous two floods. Instantaneous peak 

flow on January 1 for the South Fork at Elizabeth Park 

(fig. 1) was 3,840 ft3/s and for the main stem of the Coeur 

d’Alene River at Cataldo was 20,800 ft3/s, with a calculated 

recurrence interval at Cataldo of about 2 years (Kjelstrom, 

1996). Suspended sediment was sampled at five sites on the 

South Fork and its tributaries after peak flow on January 2 

(fig. 1B), when daily mean streamflow on the South Fork 

was 1,890 ft3/s (fig. 8).

The May 1997 flood (fig. 9) occurred as a long-delayed 

spring runoff from an abnormally heavy winter snowpack. Several flow peaks occurred between March 21 and June 1. Instantaneous peak flow for the South Fork at Elizabeth Park (fig. 1) was 

4,230 ft3/s on May 17; peak flow on the main stem of the Coeur 

d’Alene River at Cataldo was 23,300 ft3/s on May 16, with a 

recurrence interval at Cataldo of about 3–4 years (Kjelstrom, 

1996). The water-surface elevation of the lake-influenced lower 

Coeur d’Alene River at Rose Lake increased 11 ft in 30 days 

(fig. 9B), attaining a maximum elevation of 11 ft above summer 

lake-surface elevation on May 17 and a maximum current velocity in the channel estimated at less than 2 ft/s. The long-duration 

runoff maintained a high surface elevation of Coeur d’Alene 

Lake throughout the month of May, resulting in persistent high 

flow on the Spokane River below the lake outlet. Instantaneous 

peak flow for the Spokane River at Post Falls (fig. 2) was 43,900 

ft3/s on May 19 (fig. 9B), the fourth-highest flow on the Spokane 

River since 1891, with a calculated recurrence interval at Post 

Falls of 25 years (Kjelstrom, 1996). Total runoff on the Spokane 

River for May 1997 was the highest monthly volume recorded 

since gaging began in 1891. Almost no overbank flooding 

occurred during May 1997 along the South Fork or main stem 

of the Coeur d’Alene River above Cataldo, or along the Spokane River. In contrast, the entire flood plain in the lower Coeur 

d’Alene River valley below Cataldo was inundated throughout 

the month of May, owing to the high surface elevation of Coeur 

d’Alene Lake. Suspended sediment was sampled at 22 sites on 

the South Fork and main stem of the Coeur d’Alene River (fig. 

1C) on May 20 (after peak flow), on the Spokane River at 4 sites 

(fig. 2A) on May 2 (before peak flow), and on the Spokane River 

at 5 sites (fig. 2B) on May 19–20 (during peak flow).

Sampling and Analytical Methods

A total of 42 suspended-sediment samples were collected 

from the Coeur d’Alene-Spokane River system during peak 

flows on February 9–10, 1996, January 2, 1997, and May 

19–20, 1997. The suspended-sediment samples analyzed in 

this report represent grab samples of the washload portion of 

the total sediment load in suspension at the time of sampling. 

Samples were collected in February 1996 from the river’s edge 

directly into 2-gal plastic Ziploc bags held below the surface 

of the water. All other samples (except samples 10 and 22, 

collected as above) were collected with a 1-gal plastic bucket 

tied to a rope and thrown into the center of the stream from 

the downstream side of a bridge. Upon retrieval of the bucket, 

samples were transferred to 1-gal plastic Ziploc bags. Samples 

were transported to the laboratory and allowed to settle.

Suspended sediment was extracted from the 1996 and 1997 

samples by slightly different procedures. The 1996 samples 

were allowed to settle for 2 weeks. Clear water was poured off 

the top of the bag until about 0.5 L remained. The sample was 

then transferred to a glass jar, and both the glass jar and plastic 

bag were heated in an oven at 80oC for several days. Clean 

sample containers were labeled and weighed, the dried sediment 

from both the glass jar and plastic bag was transferred to them, 

and the containers were reweighed. The 1997 samples were 

allowed to settle for 3 weeks. Clear water was then poured off 

the top of the bag until 1 to 2 L remained. The sample was then 

transferred to a glass jar and again allowed to settle for 24 hours. 

Clear water was poured off the top of the jar until about 200 mL 

remained, which was spun in a centrifuge on a high setting for 4 

minutes. All but about 10 mL was poured off, and the centrifuge 

vials were heated in an oven at 80oC overnight. Clean sample 

containers were labeled and weighed, the dried sediment was 

transferred to them, and the containers were reweighed.

Suspended-sediment concentrations were measured by 

dividing the dry weight of solid by the volume of water sampled. The suspended-sediment concentrations reported here 

are for grab samples of the fine fraction or washload portion 

of the suspended-sediment load and are almost certainly less 

than the cross-section-integrated suspended-sediment concentrations (U.S. Geological Survey, 1984). However, washload 

materials (<0.063-mm-diameter grains) typically are dispersed 

relatively uniformly throughout the water column, and comSampling and Analytical Methods 11
12 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

parison of the suspended-sediment (washload) concentrations 

between sampling sites during a single high-flow event and 

between different high-flow events should be acceptable.

A total of 24 samples of sediment from streambank and 

flood-plain settings, deposited during overbank flooding in 

February 1995 and February 1996, were collected in late 

February 1995 and in late March–early April 1996, respectively, after the floodwaters had receded. Samples of streambank or natural-levee deposits (within 200 ft of the river’s 

edge) were collected with a plastic trowel into labeled plastic 

bags. Samples of recent flood sediment were collected above 

a recognizable preflood surface, typically identified by a flattened-vegetation-mat horizon. Samples of marsh sediment, 

deposited during the February 1996 overbank flood, were collected from surfaces of vegetation, rocks, or fenceposts in late 

March and early April after the floodwaters had receded, into 

labeled plastic bags. Samples were dried for 24 hours in the 

drying oven at 80oC. Streambank samples were pulverized in a 

chromium-steel ball mill to minus-200 mesh.

Samples were analyzed in the geochemical laboratory of 

Eastern Washington University, Cheney. For most samples, 

a 250-mg aliquot of the prepared sample was weighed in a 

Teflon beaker, except for some suspended-sediment samples 

for which the weight ranged from 25 to 250 mg. First, 2 mL 

of HNO3 and 1 mL of HClO4 was added to the sample, followed by heating until its volume was reduced to about half. 

Then 3 mL of HF and 5 mL of aqua regia was added to the 

sample, which was heated to dryness. Another 5 mL of aqua 

regia was added to the sample to completely break down any 

sulfide minerals. The sample was again heated to dryness, and 

the residue was dissolved in 4 mL of 1:1:2 HCl-HNO3-H2O by 

gently warming the solution. Finally, the sample was diluted to 

a volume of 25 mL with distilled-deionized water, and the solution was transferred to a 60-mL polyethylene bottle. Preparation 

blanks, duplicates, and reference standards were carried through 

the same procedure. Only Baker Instra-analyzed acids and high 

purity distilled-deionized water (similar to American Society 

for Testing and Materials type I water) were used throughout 

the digestion procedures and dilutions.

Contents of 28 elements (As, Ba, Be, Cd, Ce, Co, Cr, Cs, 

Cu, Ga, K, La, Mo, Ni, P, Pb, Rb, Sb, Sn, Sr, Th, Tl, U, V, W, 

Y, Zn, and Zr) were determined by inductively coupled plasma 

mass spectrometry (ICP–MS), using a Perkin-Elmer Sciex 

model 5000 instrument. For ICP–MS analyses, the sample 

solutions were further diluted by a factor of 10 with distilleddeionized water, and Sc, Rh, and Ho were used as internal 

standards. The concentration of HCl and HNO3 in final diluted 

solution was 0.4 volume percent. Contents of six elements 

(Al, Ca, Fe, Mg, Mn, and Ti) were determined by inductively 

coupled plasma atomic-emission spectrometry (ICP–AES), 

using a Perkin-Elmer model ICP/6000 instrument. When 

Pb and Zn contents were high, the samples were reanalyzed 

by ICP–AES. Ag content was determined by using a flame 

atomic-absorption spectrophotometer, a Perkin-Elmer model 

5000 instrument; a high-sensitivity nebulizer was used for 

determining low Ag contents.

The precision of these analyses is better than ±5 percent, 

established by duplicate analyses of numerous stream-sediment samples and reference standards. To estimate the accuracy of the chemical analyses, National Institute of Standards 

& Technology (NIST) standard reference materials (SRM) 

2710 and 2711 (Montana soils) and USGS reference standards GXR–2 and AGV–1 were analyzed with each batch of 

samples. The results obtained in this study for major and trace 

elements agreed closely with certified or recommended values. 

The contents of some elements, particularly Ba, Cr, Ti, and Zr, 

were about 5 to 10 percent lower, possibly owing to incomplete recovery of these refractory elements. The contributions 

from blanks were negligible; the contents of most elements in 

the blanks were below detection limits. Details concerning the 

accuracy and precision of the analyses of another sample set of 

stream sediment and streambank and marsh deposits from the 

drainage basin by the geochemical laboratory at Eastern Washington University were reported in Box and others (2001).

Results

Sampling sites for suspended sediment from the South 

Fork and main stem of the Coeur d’Alene River are located in 

figure 1 and from the Spokane River in figure 2, and sampling 

sites for overbank deposits from the South Fork and main stem 

of the Coeur d’Alene River are located in figure 3; corresponding analytical data are listed in tables 1 and 2. Some of the 

samples of suspended and marsh sediment collected from the 

February 1996 flood were examined by using scanning electron 

microscopy (SEM) to identify the various mineral phases that 

incorporate heavy metals (Robert Hooper, written commun., 

1998). Most of the Pb and Zn observed in the samples with 

SEM is associated with amorphous Fe and Mn oxyhydroxide compounds as irregular grains or as surface coatings on 

other grains. A minor amount of Pb is carried as Pb carbonate 

(another weathering product of the original sulfide minerals) 

and as tiny Pb sulfide grains. A small but ubiquitous component of Zn sulfide grains is also present in most samples. In the 

original ores, these four metals occur primarily as sulfide and 

associated sulfur-bearing minerals (except Mn, which occurs as 

a major impurity in siderite [Fe carbonate], an uneconomic vein 

mineral; Fryklund, 1964). These sulfide minerals are unstable 

in oxygen- and water-rich surface soils, where they break down 

into their constituent elements and reprecipitate into more 

stable secondary phases (Balistrieri and others, 2003).

Downstream Trends in Suspended-Sediment 

Concentration and Load

Suspended-sediment concentrations (in weight of sediment per volume of water), as reported here, consist of the 

silt- and clay-size washload fraction of the total cross-section-integrated suspended-sediment concentration of Edwards 

and Glysson (1999); this fraction is generally considered to 
be evenly distributed throughout the channel cross section 

(Horowitz and others, 1990) and does not include sandier 

suspended material, which is concentrated near the streambed 

surface and decreases in concentration upward in the water 

column. Suspended-sediment loads (in tons of sediment moving past a particular sampling site per day) were estimated 

for the day of sampling at many of our sites by multiplying 

the measured suspended-sediment concentration by the mean 

daily streamflow (as extrapolated from nearby U.S. Geological 

Survey gaging-station data), using the appropriate units. The 

data used in these calculations are listed in table 3.

Suspended-sediment concentrations (fig. 10A) and loads 

(fig. 10B) during the February 1996 flood were much higher 

(by one and two orders of magnitude, respectively) than during either of the sampled 1997 high-flow events. Ignoring for 

a moment the two samples with sharply lower suspended-sediment concentrations collected at mi 24 and 38, suspended-sediment concentrations in 1996 increased downstream to a peak 

on the South Fork of the Coeur d’Alene River at Smelterville 

(mi 22) and gradually decreased farther downstream. In contrast, the suspended-sediment load peaked below the confluence of the North and South Forks of the Coeur d’Alene River 

(because of the much higher discharge below the confluence) 

and gradually decreased farther downstream. The two samples 

with anomalously lower suspended-sediment concentrations 

at mi 24 and 38 were collected in situations that may have 

resulted in the lower concentrations: the sample at mi 24 was 

collected about 20 hours after peak flow, when the river-surface elevation at that site had fallen 3.5 ft; the sample at mi 38 

was collected at peak flow but along the upstream, distal edge 

of an overbank eddy about 100 ft from the channel edge.

The downstream trends in suspended-sediment concentration and load on the Coeur d’Alene River during the waning flows on May 20, 1997, show similar patterns to those of 

the February 1996 trend but at lower values (figs. 10A, 10B). 

Suspended-sediment concentrations gradually increased from 

above Mullan downstream to Wallace (fig. 1), were nearly 

static in the South Fork of the Coeur d’Alene River below 

Wallace (with one unexplained anomalously low value at mi 

12), and decreased abruptly below the confluence with the 

much larger North Fork (at mi 27). The suspended-sediment 

load gradually increased downstream from the South Fork 

into the main stem of the Coeur d’Alene River and remained 

at the same level farther downstream into the lower Coeur 

d’Alene River (fig. 10B).

Suspended sediment in the Spokane River was sampled 

twice during May 1997 high-flow event. In both sampling 

events, suspended-sediment concentrations in the Spokane 

River were very low relative to those in the South Fork and 

main stem of the Coeur d’Alene River (generally, the Spokane 

River was perceived as being “clear” during both sampling 

events), gradually increasing downstream between Coeur 

d’Alene Lake and Spokane Falls (downtown Spokane, fig. 2) 

and increasing more sharply below the muddy inflow of Latah 

Creek below Spokane Falls (mi 122). Sediment concentrations 

in the Spokane River on May 19–20 were higher than those 

on May 2. The suspended-sediment load on May 19–20 in the 

Spokane River at the lake outlet (peak flow) was about a third 

that on the Coeur d’Alene River (waning flow) and gradually 

increased downstream to values similar to, and even slightly 

larger than, those in the Coeur d’Alene River.

Downstream Trends in the Metal Contents of 

Suspended Sediment

In this section, we consider downstream trends in the 

contents of four mining-related elements (Pb, Zn, Fe, and 

Mn) in samples of suspended sediment collected during the 

1996–97 high-flow events. Lead and zinc are relatively enriched 

in mined materials in the Coeur d’Alene Mining District and, 

when enriched in sediment, can significantly impact aquatic and 

human health. Iron and manganese are less enriched in sediment but play an important role as precipitated oxyhydroxide 

compounds onto which lead, zinc, and other metals sorb. Documenting the downstream compositional trends of these metals 

in suspended sediment is a first step toward understanding the 

sources and processes that control those compositions.

The elemental composition of suspended sediment changes 

along the flowpath of a stream by input from several sources, 

including (1) new material that is added from tributaries; (2) 

new material that is added by resuspension from, or subtracted 

by deposition onto, the streambed or flood plain of the stream; 

(3) new solids that are precipitated or dissolved in, or ions that 

are adsorbed from solution onto or desorbed into solution from, 

existing solids (as inflowing tributary or ground water mix into 

the stream, as conditions change within the stream, or by biologic processes); and (4) new material that is added by atmospheric fallout. During high-flow events, the first two sources are 

expected to be the most important; the second two sources may 

deposit materials in or on (or remove them from) the streambed 

and flood plain over a water year, affecting the mix of materials 

resuspended during subsequent high-flow events.

During suspended-sediment sampling on May 20, 1997, 

Pb and Zn contents increased downstream on the South Fork 

from upstream of Mullan (fig. 1) to its mouth and progressively decreased farther downstream along the main stem of 

the Coeur d’Alene River (fig. 11). Fe and Mn contents also 

generally increased downstream along the South Fork, with 

some subparallel irregularities along the way. Fe contents 

continued to increase farther downstream in the main stem of 

the Coeur d’Alene River, whereas Mn contents peaked just 

below the confluence of the North and South Forks and then 

decreased farther downstream in the main stem. All metal 

contents increased again in the Spokane River below the lake 

outlet, decreased just above Post Falls Dam (mi 92.3), and 

gradually increased downstream to Spokane Falls to values similar to or higher than those at Cataldo on the Coeur 

d’Alene River. During suspended-sediment sampling on May 

2, 1997, metal contents were generally similar to, but lower 

than, those during peak flow on May 19–20. The sample collected farthest downstream on the Spokane River on May 2, 

Results 13
14 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

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Figure 10. Suspended-sediment concentrations in grab samples collected from the South Fork of 

the Coeur d’Alene River, main stem of the Coeur d’Alene River, and the Spokane River (“main”) and 

their tributaries (“tribs”) (A), and daily suspended-sediment loads at sampling sites for which mean 

daily streamflow could be extrapolated from nearby U.S. Geological Survey gaging stations (B), 

versus downstream distance from Mullan, Idaho (see figs. 1 and 2 for locations), during high-flow 

events in 1996 and 1997. Tributary samples are plotted at downstream distance of tributary mouth 

from Mullan, Idaho. Data points for samples collected from “main” during a single high-flow event 

are connected by lines. See table 3 for analytical data.
which had significantly lower Pb, Zn, and Mn contents but 

slightly higher Fe content, was apparently diluted by inflow of 

metal-poor suspended sediment from Latah Creek.

The downstream trend in the elemental composition of 

suspended sediment during the February 1996 flood shows a 

strikingly different pattern from that of the May 1997 flood 

(fig. 11). All metal contents except Zn were higher on the South 

Fork of the Coeur d’Alene River in the February 1996 flood, 

with a sharp peak at the Smelterville Bridge near the middle of 

the Bunker Hill Superfund site (mi 22.4, fig. 1). Metal contents 

reached a minimum at the sampling site on the Coeur d’Alene 

River just below Cataldo (mi 32.0, fig. 1). All metal contents in 

suspended sediment were considerably lower (except Fe, which 

was unchanged) at Cataldo in February 1996 than in May 1997 

and were similar to those on the South Fork at Wallace from 

May 1997. Below Cataldo, metal contents gradually increased 

downstream to a sharp peak just above Coeur d’Alene Lake.

Samples of fine sediment coating marsh vegetation and 

other objects, collected after the recession of the February 

1996 flood (fig. 3B; table 2), represent samples of suspended 

sediment accumulated over the period of flood-plain inundation, as opposed to the instantaneous samples collected 

from the water column during peak flow. Metal contents in 

this marsh sediment are compared with those in peak-flow 

suspended sediment in figure 11. Metal contents in a sample 

of 1996 marsh sediment at Cataldo (mi 32), where flood-plain 

inundation lasted about 1 day, were higher than in the corresponding sample of suspended sediment collected nearby 

during instantaneous peak flow. Metal contents in samples of 

1996 marsh sediment below Cataldo, where flood-plain inundation lasted more than 2 weeks, varied widely, with a slightly 

lower range than in corresponding samples of the instantaneous-peak-flow suspended sediment collected near the same 

sites, and increased somewhat downstream.

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Figure 11. Pb (A), Zn (B), Fe (C), and Mn (D) contents in samples of suspended sediment collected from the South Fork of the Coeur 

d’Alene River, main stem of the Coeur d’Alene River, and the Spokane River (“main”) and their tributaries (“tribs”) and in samples 

of sediment deposited in flood-plain marshes versus downstream distance from Mullan, Idaho (see figs. 1 and 2 for locations and 

tables 1 and 2 for analytical data), during high-flow events in 1996 and 1997. Tributary samples are plotted at downstream distance 

of tributary mouth from Mullan, Idaho. Data points for samples collected from “main” during a single high-flow event are connected 

by lines. Note that in five samples collected from Canyon and Ninemile Creeks (near mi 7), Pb and, in three of these samples, Zn 

contents plot offscale.

Results 15
16 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

Samples of suspended sediment were also collected at 

the mouths of several tributaries during the February 1996, 

January 1997, and May 1997 floods. A few tributaries were 

sampled during more than one high-flow event. Canyon and 

Ninemile Creeks (fig. 1), major mining-impacted tributaries 

to the South Fork of the Coeur d’Alene River at Wallace (mi 

6.8, 7.7), were sampled during three and two high-flow events, 

respectively. In these tributaries, Fe and Mn contents were 

slightly higher, and Pb and Zn contents were significantly 

higher (generally plotting off scale on fig. 11; see table 1), 

than at the next downstream sampling site in the South Fork 

during each high-flow event. Comparing high-flow events at 

the same sampling sites, all metal contents were higher in the 

February 1996 flood than in the two 1997 floods except Zn, 

which was higher in the two 1997 floods.

Fe contents in suspended sediment from other tributaries 

(sampled in either or both of the 1997 high-flow events) were 

similar to those in 1997 samples from the adjacent reach of 

the Coeur d’Alene River (except the sample from the mouth of 

Fourth of July Creek at mi 37.9, which had a much higher Fe 

content; figs. 1, 11). Pb and Zn contents in samples of suspended sediment from three of these tributaries (Mill Creek, 

mi 0.4; Government Gulch, mi 21.7; Page Creek, mi 23.8) are 

higher, and from another three of these tributaries (Big Creek, 

mi 15.3; Pine Creek, mi 24.8; Fourth of July Creek, both 

upstream and at mouth, mi 38; fig. 11) much lower, than from 

the adjacent reach of the Coeur d’Alene River.

Downstream Trends in the Metal Loads in 

Suspended Sediment

Metal loads in suspended sediment (in pounds of metal 

in suspended sediment moving past a particular sampling site 

per day) were estimated for the day of sampling at many of our 

sites by multiplying the suspended-sediment load (in weight of 

sediment per day, as calculated in a previous section) by the Pb 

and Zn contents in that sample (table 3). The calculated metal 

loads must be considered only approximate because the instantaneous suspended-sediment concentration and metal content 

of that sample are implicitly assumed to represent daily averages when they are multiplied by the mean daily streamflow. 

However, these approximate values suffice to allow recognition 

of downstream trends in the metal loads in suspended sediment 

during a single high-flow event and to allow general comparisons between different high-flow events.

Calculated daily Pb and Zn loads in suspended sediment 

are plotted against distance along the river in figure 12. The 

downstream changes in metal loads during a single high-flow 

event were small relative to the contrast between different 

high-flow events. Metal loads during the February 1996 flood 

were about 100 times larger than at corresponding sites during 

the May 1997 flood. During each high-flow event, Pb and Zn 

loads in suspended sediment increased by a factor of 3 or 4 

downstream in the South Fork (fig. 1) from Osburn (mi 12) to 

its confluence with the North Fork (mi 27) and remained fairly 

constant downstream in the main stem of the Coeur d’Alene 

River during both events. Somewhat surprisingly, Pb and Zn 

loads in the Spokane River during peak flow on May 19–20, 

1997 were nearly equivalent to those in the South Fork and 

main stem of the Coeur d’Alene River on May 20. However, 

because the samples of suspended sediment from the Coeur 

d’Alene River were collected 4 days after peak flow on that 

reach, we suspect that the metal loads in suspended sediment 

on that reach were at least somewhat higher during peak flow. 

Pb and Zn loads in suspended sediment in the Spokane River 

during peak flow on May 19–20, 1997, were more than double 

those during the earlier, lower peak flow on May 2.

The downstream increases in suspended-sediment and 

metal loads in the Spokane River during the two sampling periods in 1997 indicate that a significant proportion of the metal 

load is being progressively mobilized out of the Spokane River 

streambed sediment. At 20 mi below the lake outlet, about 70 

percent of the Pb load and more than 80 percent of the Zn load 

in suspended sediment in the Spokane River was derived from 

sediment in its bed, overwhelming the suspended component 

that transited the lake from the Coeur d’Alene River.

Downstream Trends in the Metal Contents of 

Streambank Flood Deposits

After the February 1995 flood and again after the February 

1996 flood, samples of newly deposited flood sediment were 

collected along the flanks of the river channel after high water 

had subsided. Unlike the very fine grain size of the washload 

suspended-sediment samples discussed above, these samples 

typically consisted of fine sand but ranged in grain size from 

silt to coarse sand (table 2). After the February 1995 flood, 

samples of sediment deposited on the streambank by the flood 

were collected for several miles both upstream and downstream 

of the gradient break in the Coeur d’Alene River below Cataldo 

(figs. 1, 3A). After the February 1996 flood, streambank flood 

deposits were sampled along a 40-mi reach from near Kellogg 

on the South Fork of the Coeur d’Alene River nearly to the 

delta of the Coeur d’Alene River into Coeur d’Alene Lake (fig. 

3A). Analyses of unfractionated samples of the 1995 and 1996 

streambank flood deposits are listed in table 2.

In the more extensive sampling of streambank deposits 

after the February 1996 flood (fig. 3B), metal contents gradually decrease from near Kellogg on the South Fork (fig. 13) 

to Cataldo on the main stem of the Coeur d’Alene River, and 

sharply increase beginning a few miles below Cataldo. Over 

a 4-mi reach centered on mi 36 (fig. 13), Pb and Fe contents 

more than double, while Zn and Mn contents more than 

quadruple. Metal contents similarly increase downstream over 

the same reach after February1995 flood, with nearly identical 

values. Metal contents peak near mi 40 in the 1996 streambank 

deposits and decrease downstream somewhat to the delta into 

Coeur d’Alene Lake (though still well above values at Cataldo).

Metal contents in the fine (<2-mm grain size) fraction 

of samples of streambed sediment collected on the South 
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Figure 12. Calculated daily loads of Pb (A) and Zn (B) in suspended sediment at selected 

sampling sites versus downstream distance from Mullan, Idaho (see figs. 1 and 2 for locations), 

during high-flow events in 1996 and 1997. Daily metal loads were calculated by using measured suspended-sediment concentration, Pb and Zn contents in each sample, and daily mean 

flow at that sampling site, extrapolated from daily mean streamflows measured at nearby U.S. 

Geological Survey gaging stations (see data listed in table 3). Samples collected along main 

channel (“main”) during February 1996 (red), early May 1997 (light blue), and late May 1997 

(dark blue) are connected by colored lines.

Results 17
18 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

Fork and main stem of the Coeur d’Alene River in 1993 and 

1994 (Box and others, 2001) are also plotted in figure 13. Pb 

and Zn contents in the streambed sediment samples closely 

correspond to those in the 1995 and 1996 streambank flood 

deposits at adjacent sites. Fe and Mn contents in samples of 

streambed sediment are nearly identical to those in adjacent 

streambank deposits below Cataldo but differ markedly above. 

Specifically, Fe and Mn contents in samples of streambed 

sediment between mi 20 and 30 are much higher than in 1996 

streambank flood deposits. The close similarity in the metal 

contents of the 1995 and 1996 streambank flood deposits to 

those of adjacent streambed sediment below Cataldo strongly 

suggests that streambank flood deposits were derived from 

mobilized streambed sediment in the adjacent channel (fig. 

14). Although the similarity in the Pb and Zn contents of the 

streambank deposits and adjacent streambed sediment above 

Cataldo also suggests such a derivation, their contrasts in Fe 

and Mn contents suggest that other processes or sources must 

also be important over that reach.

Interelement Correlations in Flood Sediment

In the Coeur d’Alene Mining District, fine Fe and Mn 

oxyhydroxide compounds commonly occur as weathering 

products within accumulations of tailings and tailings-contaminated sedimentary deposits in the valley, and as precipitates 

floating within mining-impacted streams and coating streambed sediment (Horowitz and others, 1993; Balistrieri and 

others, 2003). As discussed above, SEM examination of some 

of the samples of February 1996 suspended sediment indicated 

that lead and zinc were spatially associated with fine Fe and 

Mn oxyhydroxide minerals, probably by sorption (Robert 

Hooper, written commun., 1998). In the following discussion, 

we more carefully examine the relations between Fe, Mn, Pb, 

and Zn in our samples, as well as several other mining-related 

elements, including Ag, As, Cd, Cu, and Sb.

For comparison purposes, the entire flood-sediment-sample suite was grouped by sample media (suspended, streambank, and flood-plain marsh sediment), river reach, and year. 

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Figure 13. Pb (A), Zn (B), Fe (C), and Mn (D) contents in samples of streambank sediment deposited along the South Fork and main 

stem of the Coeur d’Alene River versus downstream distance from Mullan, Idaho (see fig. 3 for locations), during February 1995 and 

February 1996 high-flow events. Data points for samples of sediment deposited on streambank during high-flow events of February 

1995 (gray triangles) and February 1996 (red circles) are connected by colored lines. Yellow squares, samples of streambed sediment collected from river channel in 1993 and 1994 (Box and others, 2001). Similarity of downstream progression in metal contents of 

streambank deposits from the two floods, as well as their similarity to those of adjacent streambed sediment, suggests that streambank sediment deposited during each flood was mobilized from sediment in adjacent streambed.
The four river reaches are (1) tributaries to the South Fork 

of the Coeur d’Alene River, including the South Fork above 

Wallace; (2) the South Fork of the Coeur d’Alene River below 

Wallace; (3) the main stem of the Coeur d’Alene River, and (4) 

the Spokane River (figs. 1–3). Samples of streambank flood 

deposits are subdivided into those from the South Fork, those 

on the main stem of the Coeur d’Alene River above Cataldo, 

and those on the main stem below the abrupt flattening of the 

stream gradient a few miles below Cataldo.

In the following discussion, we compare the interelement 

correlations in samples from subsets of these sample groups. On 

the accompanying element-element scatterplots (figs. 15–17), 

regression lines are calculated for selected data subsets by river 

reach and, for some samples, by year as well. Regression lines 

on the plots were calculated by the least-squares method, and 

coefficients of determination (R2) are listed; however, given the 

generally small size of the data subsets (mostly less than 25 

samples, some as small as 8 samples), the statistical significance 

of some of these apparent correlations is uncertain. Nonetheless, the consistent contrasts in the correlation trends between 

selected data subsets argue strongly for their general distinction.

Fe and Mn correlate strongly (R2=0.86) in all samples (fig. 

15A). The Fe contents of all samples separate into two clusters: 

(1) samples containing from 9 to 11 weight percent Fe (mostly 

streambank flood sediment from the lower Coeur d’Alene River 

below Cataldo), and (2) samples containing from 3 to 7 weight 

percent Fe (all other samples). The linear regression line for 

this correlation trends toward a point at 0 ppm Mn and about 2 

weight percent Fe, apparently reflecting a sedimentary mixture 

of two Fe compounds in the sediment: in a form unassociated 

with Mn (2 weight percent Fe in all samples), and in association 

with Mn. We infer that the association of Fe with Mn represents 

Fe and Mn oxyhydroxide compounds produced from weathering of tailings-contaminated sedimentary deposits in the valley 

and from interaction of ground and surface waters (Horowitz 

and others, 1993; Balistrieri and others, 2003).

Zn and Pb correlate crudely in all the samples of flood 

sediment (R2=0.62; regression line not shown in fig. 15B), but 

better correlations result from clustering the sample set into three 

subsets: (1) samples with Zn less than Pb contents (mostly 1996 

samples, including suspended sediment from the South Fork 

and main stem of the Coeur d’Alene River, marsh flood sediment from the Coeur d’Alene River valley, and both 1995 and 

1996 streambank flood deposits from the South Fork and main 

stem of the Coeur d’Alene River above Cataldo; (2) samples 

with Zn about equal to Pb contents (1996 and 1997 suspended 

sediment from tributaries to the South Fork of the Coeur d’Alene 

River, and 1997 suspended sediment from the South Fork); 

and (3) samples with Zn greater than Pb contents (mostly 1997 

samples, including suspended sediment from the Coeur d’Alene 

and Spokane Rivers, but also 1995 and 1996 streambank flood 

deposits from the Coeur d’Alene River below Cataldo). A t test 

indicates that the differences between the three subsets are statistically significant. The first subset defines a linear regression line 

(R2=0.86) that trends toward the origin (0 ppm Zn and 0 ppm 

Pb) and has the shallowest slope (that is, the smallest increase in 

Zn content relative to increasing Pb content), and the third subset 

defines a linear regression line (R2=0.75) that trends toward a 

point at 1,790 ppm Zn and 0 ppm Pb and has the steepest slope. 

The second subset defines a linear regression line (R2=0.72) 

intermediate between the other two, trending toward a point at 

680 ppm Zn at 0 ppm Pb. These relations suggest the presence 

of a sedimentary component with Zn but no Pb content in the 

second and third sample subsets (discussed further below).

The relations of Pb and Zn to Fe and Mn are complex, 

as shown in figures 16 and 17. For the entire sample set, Pb 

and Fe correlate poorly (R2=0.14), but better correlations 

result from dividing the sample set into three subsets by river 

reach, regardless of year (fig. 16A): (1) suspended sediment 

(n=16) from tributaries to the South Fork of the Coeur d’Alene 

River (high Pb/Fe ratios; R2=0.94), (2) suspended and streambank flood sediment (n=9) from the South Fork of the Coeur 

d’Alene River (moderate Pb/Fe ratios; R2=0.94, when sample 

outlier of streambank sediment with 7.2 weight percent Fe is 

omitted), and (3) suspended, streambank, and marsh sediment (n=38) from the main stem of the Coeur d’Alene River 

and suspended sediment from the Spokane River (low Pb/Fe 

ratios; R2=0.80). The regression lines radiate from a point at 

Figure 14. Schematic cross section of river channel and natural levee during overbank 

flooding. Blue, floodwater; pink-dotted unit, sandy material entrained along riverbed; red 

layered unit, historical metal-enriched sedimentary deposits; yellow layer, premining 

unconsolidated deposits. Sandy material deposited on channel margin and levee top during overbank flood is mobilized from (and is similar in elemental composition to) adjacent 

streambed sediment and is deposited as water velocities decrease along channel flanks.

Results 19
20 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

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Figure 15. Mn versus Fe contents (A) and Zn versus Pb contents (B) in flood-sediment samples grouped by sample 

media, river reach, and flood year. Sample media: B–, streambank sediment; M–, marsh sediment; S–, suspended sediment. River reaches: CR, main stem of the Coeur d’Alene River; LCR, lower main stem of the Coeur d’Alene River, downstream from Cataldo; SF, South Fork of the Coeur d’Alene River; Sp, Spokane River; Tr, tributary to the South Fork of the 

Coeur d’Alene River; UCR, upper main stem of the Coeur d’Alene River, from Cataldo upstream. Year (combined if not designated): 96, 1996; 97, 1997. Data points for two tributary samples with more than 12,000 ppm Pb and (or) Zn plot outside 

area of figure 15B. Linear-regression lines and coefficients of determination (R2, calculated by least-squares method) are 

for samples clustered by year and river reach into three subsets as listed in figure 15B.
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Figure 16. Pb versus Fe contents (A) and Pb versus Mn contents (B) in flood-sediment samples grouped by 

sample media, river reach, and flood year. Same symbols and abbreviations as in figure 15; see figures 1 and 2 

for locations. Linear-regression lines and coefficients of determination (R2, calculated by least-squares method) 

are for samples clustered by river reach (regardless of year) into three subsets as listed. Sample B–SF96 outlier 

with 7.2 weight percent Fe and 5,280 ppm Mn was not used in regression calculation. Data points for two tributary samples that contain more than 12,000 ppm Pb plot outside area of figures.

Results 21
22 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

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Figure 17. Zn versus Fe contents (A) and Zn versus Mn contents (B) in samples grouped by sample 

media, river reach, and flood year. Same symbols and abbreviations as in figure 15; see figures 1 and 

2 for locations. Linear-regression lines and coefficients of determination (R2, calculated by leastsquares method) are for samples separated by river reach into three subsets as in figure 16, except 

for 1997 suspended samples and lower Coeur d’Alene River streambank samples, which correlate with 

next upstream subset (that is, 1997 samples from the South Fork of the Coeur d’Alene River correlate 

with tributary samples, and 1997 samples from the Spokane River and main stem of the Coeur d’Alene 

River correlate with 1996 samples from the South Fork of the Coeur d’Alene River). Data points for two 

tributary samples that contain more than 12,000 ppm Zn plot outside area of figures.
Discussion 23

0 ppm Pb and about 2.0 to 2.5 weight percent Fe. Pb and Mn 

correlate well in the same three sample subsets (fig. 16B), with 

regression lines radiating from closer to the origin (0 ppm Pb 

and 0–1,000 ppm Mn). Similar correlations of Pb with Fe and 

Mn by reach along the Coeur d’Alene-Spokane River system 

provide strong supporting evidence that Pb is associated with 

Fe and Mn mineral compounds, suggesting that this association changes stepwise in a downstream direction (that is, from 

tributaries to the South Fork, to the South Fork itself, and 

finally into the main stem of the Coeur d’Alene River, continuing through Coeur d’Alene Lake into the Spokane River) to 

account for the stepwise changes in geochemical correlations.

Because Zn and Pb correlate differently for samples from 

the 1996 versus the 1997 floods (fig. 15B), the sample subsets 

(by river reach) used for correlations of Zn to Fe and Mn in figure 17 are modified somewhat from those used for Pb in figure 

16. The 1997 suspended-sediment sample groups and the sample 

group of all streambank flood deposits from the lower Coeur 

d’Alene River are each correlated with the next upstream sample 

subset. For example, the 1997 South Fork suspended-sediment 

samples, which clustered with 1996 South Fork suspended-sediment samples at moderate Pb/Fe and Pb/Mn ratios in figure 16, 

correlate with the tributary samples at high Zn/Fe (R2=0.62) and 

Zn/Mn (R2=0.69) ratios in figure 17. Likewise, the samples of 

1997 suspended sediment from the Coeur d’Alene and Spokane 

Rivers and all streambank flood deposits from the lower Coeur 

d’Alene River, which clustered with 1996 Coeur d’Alene River 

samples at low Pb/Fe and Pb/Mn ratios in figure 16, correlate 

with 1996 South Fork samples at moderate Zn/Fe (R2=0.69) and 

Zn/Mn (R2=0.77) ratios in figure 17. In figures 17A and 17B, the 

regression lines for the sample subset including the 1997 Coeur 

d’Alene and Spokane River suspended sediment nearly parallel 

those for the sample subset including the 1996 Coeur d’Alene 

suspended and marsh sediment but are higher by 1,500 to 2,000 

ppm Zn at a given Fe or Mn content. These trends (along with 

those in fig. 15B) suggest that 1,500 to 2,000 ppm of the Zn in 

the 1997 Coeur d’Alene and Spokane River suspended sediment 

and in streambank flood deposits along the lower Coeur d’Alene 

River is not associated with Fe and Mn.

Several previous studies in the Coeur d’Alene-Spokane 

River system have also suggested the presence of a sedimentary component of particulate Zn that is not strongly associated with Fe, Mn, or Pb. Paulson (2001) found that dissolved 

Zn is progressively lost from river water downstream in the 

Coeur d’Alene River below Cataldo, apparently by sorption 

onto organic particulates, which accumulate in the streambed 

sediment. Similarly, Box and Wallis (2002) identify a highZn, low-Pb component in streambed sediment in the Spokane 

River that they suggest is derived by precipitation of Zn in 

new particles or by sorption of Zn onto existing particles. 

Balistrieri and others (2003) showed that dissolved Zn is lost 

during mixing of Zn-rich ground waters with Coeur d’Alene 

River water, either by sorption onto existing Fe-rich particles 

or by precipitation of Fe-rich flocculants. We suggest that 

the process of sorption of dissolved Zn from river water onto 

existing organic or inorganic particles contributes the sedimentary component of Zn, which is apparently not associated with 

Fe, Mn, or Pb, to the sources of the 1997 suspended sediment 

in the Coeur d’Alene and Spokane Rivers and of the streambank flood sediment along the lower Coeur d’Alene River.

Several other mining-related elements consistently correlate with either Zn or Pb, although the samples of suspended 

sediment from the Spokane River commonly are somewhat 

distinct from those the Coeur d’Alene River and tributaries (figs. 1, 2). Cd correlates well with Zn (fig. 18A), with a 

weight ratio of about 5:1,000. Both Ag and Sb correlate well 

with Pb (figs. 18B, 18C), with weight ratios of 3:1,000 and 

10:1,000, respectively, although the samples of suspended sediment from the Spokane River have weight ratios consistently 

different from (about half) those from the Coeur d’Alene 

River and its tributaries. Ag consistently correlates with Sb 

(R2=0.83) in all samples (fig. 18D) with a weight ratio of 1:4.

Correlations between some of the mining-related elements are weak or nonexistent. Arsenic broadly correlates 

with Fe in all the samples (R2=0.64), but within-group 

trends are generally scattered (fig. 18E). Cu correlates 

poorly with all other mining-related elements, as illustrated 

by a plot of Cu versus Fe contents (fig. 18F). Cu contents 

in many of the samples of tributary suspended sediment and 

in some of the samples of Spokane River suspended sediment are anomalously high relative to enrichments in other 

mining-related elements.

Discussion

Sources of Metal-Enriched Sediment Mobilized 

During Flooding and the Processes Responsible 

for Elemental Distributions

The geographic and temporal variations in mining-related 

elemental composition and in interelemental correlations in flood 

sediment in the Coeur d’Alene-Spokane River system (figs. 1, 2) 

result from corresponding variations in the sediment sources and 

their characteristics. The ultimate sources of the metal-enriched 

materials are the ore deposits of the Coeur d’Alene Mining District, in which the Pb, Zn, Cd, Ag, Cu, As, Sb, and some of the 

Fe are held in sulfidic minerals, while the Mn and some of the Fe 

are held in carbonate gangue minerals (Fryklund, 1964). Once 

these ores are extracted from the deep subsurface and placed in 

the oxidizing surface environment, the primary ore and gangue 

minerals begin to weather and are gradually replaced by secondary compounds, which consist of various oxide, carbonate, 

phosphate, sulfate, and sulfide minerals (Fryklund, 1964; Hooper 

and Mahoney, 2000). Many of the primary minerals in the 

approximately 62 million tons of mine-waste materials that were 

disposed of into the South Fork of the Coeur d’Alene River and 

its tributaries between 1886 and 1968 (Long, 1998) have subsequently weathered into these secondary compounds. The overall 

strong correlations of mining-related elements with Fe and Mn 

in flood-sediment samples, along with the spatial association 
24 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

0

20

40

60

80

0 2,000 4,000 6,000 8,000 10,000

Zn CONTENT, IN PARTS PER MILLION

Cd CONTENT IN PARTS PER MILLION

A

 All samples

 R2

 = 0.68 

0

5

10

15

20

25

30

0 2,000 4,000 6,000 8,000 10,000 12,000

Ag CONTENT, IN PARTS PER MILLION

 All samples

 R2

 = 0.86

S-Tr

S-SF97

S-SF96

S-CR97

S-CR96

S-Sp97

M-CR96

B-SF96

B-UCR

B-LCR

EXPLANATION

B

Pb CONTENT, IN PARTS PER MILLION

Figure 18. Cd versus Zn contents (A), Ag versus Pb contents (B), Sb versus Pb contents (C), Ag versus Sb 

contents (D), As versus Fe contents (E), and Cu versus Fe contents (F ) in flood-sediment samples grouped 

by sample media, river reach, and flood year, showing linear-regression lines for all samples and coefficients 

of determination (R2, calculated by least-squares method). Same symbols and abbreviations as in figure 15; 

see figures 1 and 2 for locations. Data points for two tributary samples that contain more than 10,000 ppm 

Zn plot outside area of 18A; data points for two tributary samples that contain more than 12,000 ppm Pb plot 

outside area of figure 18B; data points for three tributary samples that contain more than 100 ppm Sb and 

(or) more than 12,000 ppm Pb plot outside area of figure 18C; and data points for two tributary samples that 

contain more than 200 ppm As plot outside area of figure 18E and were not used in regression calculation.
Discussion 25

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26 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

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Figure 18. Continued.
Discussion 27

of those elements in SEM backscatter images, indicate a strong 

mineralogic association of Pb, Zn, and other mining-related 

elements with secondary Fe and Mn oxyhydroxide phases. The 

varying processes of weathering, transport, and depositional 

storage of the mining-related materials are presumed to lead to 

geochemical variations in sediment sources and their characteristics. In the following discussion, we identify potential sources of 

the flood sediment and consider some implications of the varying 

source mixtures that are required to produce the geographic and 

temporal variations in the geochemistry of flood sediment.

A large dataset of chemical analyses of potential flood-sediment source materials is available for the South Fork and main 

stem of the Coeur d’Alene River (Abraham, 1994; Fousek, 1996; 

McCulley and others, 1995; Golder Associates, 1996; Paulson 

and others, 1996; Terragraphics Environmental Engineering, 

Inc., 1996; Box and others, 2001). Because many of the analyses of South Fork materials consist of data for only Pb and Zn, 

we compare only these elements with the flood-sediment data. 

The analyses are divided into those of streambed sediment from 

the South Fork (fig. 19A), soils and sedimentary deposits on the 

South Fork historical flood plain (fig. 19B), streambed sediment 

from the Coeur d’Alene River below Cataldo (fig. 20A), and soils 

and sedimentary deposits from the active Coeur d’Alene River 

flood plain (fig. 20B). Much higher metal contents are common in 

soils on the historical flood plain of the South Fork of the Coeur 

d’Alene River than on the active flood plain of the main stem of 

the Coeur d’Alene River below Cataldo, or in streambed sediment 

from either channel reach. Also noteworthy are the contrasting 

Zn/Pb ratios between the flood-plain soils/sedimentary deposits 

and the streambed sediment. Zn/Pb ratios for South Fork streambed sediment scatter on both sides of 1.0 (fig. 19A), average about 

1.25 for Coeur d’Alene River streambed sediment below Cataldo 

(fig. 20A), and average much less than 1.0 for sedimentary deposits from either flood-plain segment (figs. 19B, 20B). The apparent 

cause of this variation in Zn/Pb ratio is the higher solubility of Zn 

than of Pb in oxidized surface and ground waters of the drainage 

basin. Percolating soil water gradually leaches Zn from the oxidized surface soils, lowering the soil Zn/Pb ratio as the soil weathers. Some fraction of dissolved Zn in surface water of the lower 

Coeur d’Alene River has been shown to sorb onto inorganic or 

organic surfaces between Cataldo and Harrison (Paulson, 2001). 

The influx of slightly acidic ground water with high dissolved Zn 

and low dissolved O contents into oxygenated waters of the river 

channel results in precipitation of fine Fe and Mn oxyhydroxides 

with a high content of sorbed Zn but low Pb content (Balistrieri 

and others, 2003). These processes result in Zn/Pb ratios of 1.0 or 

greater in submerged-channel sediment.

The contrasts in Zn/Pb ratio among some of the samples of 

flood sediment (fig. 15B) might be explainable by differences in 

sediment sources. The 1995–97 samples of flood sediment (except 

for the tributary samples) approximately separate (fig. 15B) into 

those with Zn/Pb ratios less than 1.0 (all 1996 samples except 

those of lower Coeur d’Alene River streambank deposits) and 

those with Zn/Pb ratios greater than 1.0 (all the samples of 1997 

suspended sediment plus those of the lower Coeur d’Alene streambank deposits). By analogy with the potential flood-sediment 

source materials (figs. 19, 20), the lower Zn/Pb ratios of the 1996 

samples of suspended and marsh sediment are consistent with a 

greater component of eroding-flood-plain soils, whereas the higher 

Zn/Pb ratios of the 1997 samples of suspended sediment suggest 

a larger component derived from streambed sediment.

Before we discuss how these differences in flood sediment 

source materials might be explained, we present some crude 

calculations of the potential contributions of fine sediment from 

streambed, the streambank, and flood-plain deposits. Mobilization of sandy streambed sediment releases the incorporated 

fine (<0.063-mm grain size) fraction (avg 30 weight percent in 

the lower Coeur d’Alene River; U.S. Environmental Protection 

Agency, 1998) into washload suspension throughout the water column. Mobilization of the upper 10 cm of streambed deposits over 

the 50-m average width of historical deposits in the Coeur d’Alene 

River below Cataldo yields about 1.5 m3 of fines per linear meter 

of channel. Erosion of streambanks, with the average streambank 

lateral-erosion rate of 6.4 cm/yr on each streambank (derived 

from measurements at 34 sites over 4 years: S.E. Box and A.A. 

Bookstrom, unpub. data, 2000), an average thickness of 0.7 m of 

metal-enriched streambank soil/sedimentary deposit (Bookstrom 

and others, 2001), and an average fine (...0.063-mm grain size) 

fraction of 60 weight percent (data from the lower Coeur d’Alene 

River; U.S. Environmental Protection Agency, 1998) yields about 

0.05 m3 of fines per linear meter of channel, or about 4 percent of 

the inferred yield of mobilized streambed deposits. Mobilization 

(during overbank flooding) of the upper 2 cm of the sandy, poorly 

vegetated natural levee (average width, 360 m: Bookstrom and 

others, 2001) of the Coeur d’Alene River below Cataldo (upland 

of Bookstrom and others, 1999, 2001), with an average of 60 

weight percent fine (<0.063-mm grain size) fraction (U.S. Environmental Protection Agency, 1998) would yield 4.3 m3 of fines 

per linear meter of valley, nearly 100 times that calculated from 

eroding streambank deposits and 3 times that from resuspended 

streambed sediment. Although considerable uncertainty exists in 

the depth of mobilization of either the streambed sediment or the 

upland flood-plain surface, mobilization of a thin surficial layer 

over their broad areal extent clearly would volumetrically overwhelm the contribution of a much thicker but also much narrower 

slice of eroding streambank deposits.

The large February 1996 flood had a suspended washload about 100 times greater than that of the smaller May 

1997 flood (fig. 10B). Because only minor overbank flooding occurred along the South Fork of the Coeur d’Alene 

River (figs. 1, 2) in the February 1996 flood, we infer that the 

primary sources of suspended sediment over that reach must 

have been from remobilized streambed sediment and from 

eroding streambank deposits. Given the high metal contents 

of the flood-plain deposits exposed in streambanks along 

the South Fork (fig. 19B) relative to those of the streambed 

sediment in the same reach (fig. 19A), only a small input of 

eroding-streambank deposits would be required to produce the 

low Zn/Pb ratios of the 1996 samples of South Fork suspended 

sediment, even if it was derived predominately from remobilized streambed sediment. Along the Coeur d’Alene River 

below Cataldo in the February 1996 flood, extensive overbank 
28 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

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Figure 19. Zn versus Pb contents in potential flood-sediment source materials in and along the South Fork of the 

Coeur d’Alene River, northern Idaho (see fig. 1). A, Streambed sediment, analyzed by grain-size fraction. Data from 

Box and others (2001). B, Unfractionated historical flood-plain soils. Data from McCulley and others (1995), Golder 

Associates (1996), and Terragraphics Environmental Engineering, Inc. (1996). Dashed diagonal line indicating equal 

Zn and Pb contents is shown for reference.
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Figure 20. Zn versus Pb contents in potential flood-sediment source materials in and along main stem of the Coeur 

d’Alene River downstream from Cataldo, Idaho (fig. 1), showing linear-regression lines for all samples and coefficients of determination (R2

, calculated by least-squares method). Data from Box and others (2001). A, Uppermost 1 

m of streambed sediment. B, Historical streambank deposits. Dashed diagonal line indicating equal concentrations 

of Zn and Pb shown for reference in each diagram. Zn content is generally greater than Pb content in streambed 

sediment but is generally less than Pb content in weathered streambank deposits.

Discussion 29
30 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

flooding did occur, and so both eroding streambank deposits 

and resuspension of the fine fraction of surficial flood-plain 

soils are potential sources of the lower-Zn/Pb-ratio component. 

Because of the volumetric considerations discussed above, 

resuspension of the fine fraction of upland exposures of Coeur 

d’Alene River flood-plain soils probably was the predominant 

source of the low-Zn/Pb-ratio Coeur d’Alene River suspended 

sediment sampled in 1996 (fig. 21A).

The consistently high Zn/Pb ratio of suspended sediment 

in the 1997 floods contrasts with that in the February 1996 flood 

(fig. 15B). We suggest that the 1997 samples of suspended sediment on the South Fork and main stem of the Coeur d’Alene 

River were primarily derived by resuspension of the fine fraction of the streambed sediment, which has a Zn/Pb ratio greater 

than 1.0. The lower discharge in the 1997 floods (that is, 20,000 

versus 70,000 ft3/s on the Coeur d’Alene River at Cataldo) produced lower river-surface elevations on the South Fork (below 

most cutbanks of metal-enriched flood-plain soil) and slower, 

less erosive currents on the flood plain of the lower Coeur 

d’Alene River valley than in the February 1996 flood, reducing 

the relative contribution of flood-plain soils to the suspended 

sediment. This lesser discharge of the 1997 floods (30 percent 

that of the February 1996 flood) and its smaller suspended sediment load (1 percent that of the February 1996 flood) resulted in 

the predominance of streambed-derived fines over streambankor flood-plain-soil-derived fines in the suspended-sediment load 

(fig. 21B). Because the recurrence interval of floods like those 

of 1997 (3–4 years at Cataldo) is much shorter than that of the 

February 1996 flood (approx 100 years), we infer that streambed-derived fines are the dominant source of the suspended 

sediment load in most high-flow events.

Suspended sediment in the Spokane River at the outlet of 

Coeur d’Alene Lake in May 1997, occurring at low concentrations even at the highest flows, was dominated by metalenriched fines that had traversed the lake after input from 

the mouth of the Coeur d’Alene River. This interpretation is 

strongly supported by the similarity of their Fe and Mn contents 

and of their Pb/Fe and Pb/Mn ratios to those of Coeur d’Alene 

River suspended sediment from all sampled floods, and by the 

similarity of their Zn/Fe, Zn/Mn, and Zn/Pb ratios to those of 

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Figure 21. Schematic cross sections of the lower Coeur d’Alene River valley, northern 

Idaho (fig. 1), during overbank flooding in February 1996 (A) and May 1997 (B). Although overbank floods reached similar floodwater elevations in the lake-backwater-influenced lower 

Coeur d’Alene valley during the two high-flow events, geochemistry of fine suspended sediment in each flood was distinctive because of different balance of flood-sediment sources. 

Dark blue, water elevation in river channel during low-flow conditions; light blue, floodwater elevation; red, metal-enriched flood-plain-levee soil; green, backlevee marsh; yellow, 

premining valley deposits and bedrock. Short-duration high discharge during February 1996 

flood (50–100-year recurrence interval) generated high flow velocities over thinly vegetated 

natural flood-plain levees, mobilizing fine metal-enriched material with low Zn/Pb ratio from 

weathered flood-plain surface (large red arrows, fig. 21A), which dominated suspended-sediment budget over bedload-derived fine material from channel (large blue arrow). In contrast, 

long-duration, moderate discharge during May 1997 flood (3–4-year recurrence interval) 

raised elevation of Coeur d’Alene Lake and backflooded the lower Coeur d’Alene River valley, with floodwater elevations slightly higher than in February 1996. Lower flow velocities 

over flood-plain levees in 1997 flood did not significantly mobilize surface materials, such that 

suspended-sediment budget was dominated by fine material winnowed out of remobilized 

streambed sediment (large blue arrow, fig. 21B), with lesser contributions from erosion of 

weathered streambank deposits and flood-plain soils (small red arrows).
Conclusions 31

Coeur d’Alene River suspended sediment from the same highflow event. However, the increases in suspended-sediment concentration and metal loads farther downstream in the Spokane 

River indicate addition of metal-rich suspended sediment mobilized from the streambed sediment. The distinctly lower Ag/Pb 

ratio in 1997 suspended-sediment samples from the Spokane 

River (figs. 18B, 18C) apparently reflect a similar ratio in Spokane River streambed sediment (Grosbois and others, 2001); the 

cause of this and, possibly, other contrasting ratios (for example, 

Sb/Pb) in the source is uncertain. The Ag/Pb and Sb/Pb ratios 

of Coeur d’Alene Lake bottom sediment do not show a decreasing trend northward in the lake or a correlation with grain size 

at any sampling site (Horowitz and others, 1993), as would be 

expected if the contrasting ratios were produced during transit 

through Coeur d’Alene Lake.

Samples of marsh sediment deposited in the Coeur 

d’Alene River valley during the 1996 flood have metal ratios 

similar to those of samples of suspended sediment collected 

from the adjacent Coeur d’Alene River in the same flood and 

were presumably deposited from the fallout of suspended 

sediment during the month-long inundation of the flood plain. 

However, metal contents of most marsh-sediment samples are 

somewhat lower than those of the nearest peak-flow suspended-sediment samples. The cause of this apparent decrease 

in metal contents is uncertain. We suggest two possible causes: 

(1) suspended sediment similar in metal contents to peak-flow 

suspended sediment was deposited in the marshes during peak 

flow, but deposition of lower-metal-content material followed 

during the longer period of flood-plain inundation, leading to 

lower average metal contents of the flood deposits; or (2) the 

high specific gravity of Fe and Mn compounds bearing the 

other heavy metals caused them to preferentially settle out as 

currents waned with distance from the channel.

The most striking downstream trend in samples of 

streambank deposits from both the 1995 and 1996 floods is 

the sharp increase in metal contents below the gradient break 

in the Coeur d’Alene River below Cataldo (fig. 13). This 

downstream change in the elemental composition of streambank deposits correlates with the similar change in elemental 

composition of sandy streambed sediment across that gradient 

break, because the streambank deposits represent entrained 

streambed sediment that was dropped on the natural levee as 

water spilled out of the channel (fig. 14). Above the gradient 

break, streambed sediment consists of coarse cobbly bars, 

capped locally by ephemeral sandbars; below the gradient 

break, cobbles are absent, and surficial streambed sediment 

consists of several meters of metal-enriched sand and silt accumulated since the onset of mining in the drainage basin (U.S. 

Environmental Protection Agency, 1998; Box and others, 

2001). Reduction in the input of metal-rich sediment to the 

main stem from the Coeur d’Alene River by the South Fork 

after the cessation of tailings releases in 1968 has resulted in 

more effective dilution of the fine fraction of streambed sediment in the cobbly channel below the confluence by the metalpoor component from the North Fork. Higher metal contents 

in the sandy surficial streambed sediment below the gradient 

break are maintained by remobilization of the underlying, historical metal-rich streambed deposits, resulting in the contrast 

in metal content above and below the gradient break.

Conclusions

1. Suspended-sediment concentrations were 10 to 20 times 

greater, and peak flows 4 to 5 times higher, during the 

100-year flood of 1996 than during the 2- to 5-year floods 

of 1997, resulting in suspended-sediment loads as much 

as 100 times higher in 1996. The daily Pb and Zn loads in 

suspended sediment (in weight of metals transported in suspended sediment past a given point per unit time) were also 

typically about 100 times greater during the 1996 flood.

2. Contents of nine mining-related elements (Pb, Zn, Fe, 

Mn, Ag, Cd, Cu, Sb, As) in suspended sediment typically 

increase downstream along the South Fork of the Coeur 

d’Alene River through the Coeur d’Alene Mining District, 

decrease below the confluence of the North and South 

Forks, and increase again downstream below the gradient 

break at Cataldo. Metal contents in suspended sediment of 

the Spokane River below Coeur d’Alene Lake were similar 

to those of the lower Coeur d’Alene River above the lake 

during the 1997 spring runoff.

3. The ratios of most mining-related elements (Pb, Zn, Ag, 

Sb, Cd) to Fe and Mn are similar within each river reach 

(tributaries to the South Fork of the Coeur d’Alene River, 

the South Fork of the Coeur d’Alene River, the main stem 

of the Coeur d’Alene River, and the Spokane River). SEM 

observations indicate that these elements occur primarily in 

fine aggregates and grain coatings of amorphous Fe and Mn 

oxyhydroxide compounds and that the other mining-related 

elements are adsorbed onto the Fe and Mn compounds. 

Changes in the ratios of most mining-related elements to Fe 

or Mn between river reaches could be due to downstream 

changes in Fe and Mn oxyhydroxide compounds because 

of aging, or to subtle physicochemical source changes in 

river water or in pore water in the suspended sediment 

source areas (streambed or streambanks). Much of the Zn 

in Spokane River suspended sediment is not associated 

with Fe or Mn but is inferred to be associated with organic 

matter generated in the Coeur d’Alene River (Paulson, 

2001), in Coeur d’Alene Lake (Kuwabara and others, 2000) 

and in the Spokane River (Box and Wallis, 2002).

4. The contrasting geochemistry between suspended-sediment samples from the 1996 and 1997 floods indicates 

that the predominant suspended-sediment sources 

differed between the 100-year flood of 1996 and the 

2–5-year floods of 1997. The 1996 suspended sediment 

is most geochemically similar to flood-plain soil over 

the same reach, whereas the 1997 suspended sediment 

is most similar to streambed sediment over the same 

reach. Volumetric considerations suggest that the larger 
32 Stream-Sediment Geochemistry in Mining-Impacted Streams: Coeur d’Alene-Spokane River System

suspended-sediment loads in the February 1996 flood 

(100 times larger than those in the May 1997 flood) 

were most likely released to suspension when overbank traction currents remobilized flood-plain soils 

on the broad, poorly vegetated natural levees (upland 

of Bookstrom and others, 2001) of the lower Coeur 

d’Alene River. This remobilization of flood-plain soils 

apparently was less significant in the smaller floods of 

1997, and so the smaller suspended-sediment load was 

dominated by fine material released during the mobilization of streambed sediment. Similar material was 

released from mobilized streambed sediment in both 

the 1996 and 1997 floods, but its geochemical signature was dwarfed in the 1996 flood by the much larger 

contribution from remobilized flood-plain soils.

5. Suspended sediment in the Spokane River at the immediate outlet of Coeur d’Alene Lake consists of suspended 

sediment derived from the lower Coeur d’Alene River 

that transited the lake. Farther downstream, however, the 

suspended-sediment and metal loads gradually increase 

through addition of fine sediment mobilized from previously deposited sediment in the riverbed. After 20 river mi 

(that is, in Washington) this sediment component derived 

from the riverbed accounts for 70 percent of the Pb load 

and more than 80 percent of the Zn load carried as suspended sediment.

6. Samples of overbank deposits in the backlevee marshes collected after the 100-year flood of 1996 have similar metal 

ratios to those of peak-flow suspended sediment over the 

same river reach, but with generally lower metal contents. 

Flood deposits on the immediate streambank or natural 

levee of the river are typically composed of sandy material 

mobilized from sandy streambed sediment in the adjacent 

river reach, which have similar metal contents and ratios.

Acknowledgments

We are grateful to Mike Beckwith (formerly of the U.S. 

Geological Survey) for his help in gaining access to critical 

sampling sites during the February 1996 flood. We appreciate 

the help of Yvonne Isaak and Kevin Myers in processing our 

samples, and of John Wallis in drafting the figures. We thank 

Bob Hooper for sharing the results of his SEM analyses of our 

samples. We also thank Jim Rytuba and Laurie Balistrieri for 

their helpful reviews of the manuscript.

References Cited

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geochemistry and lead isotopic composition of sediments in 

Coeur d’Alene River, Idaho: Cheney, Eastern Washington 

University, M.S. thesis, 149 p.

Balistrieri, L.S., Box, S.E., and Tonkin, J.W., 2003, Modeling 

precipitation and sorption of elements during mixing of river 

water and porewater in the Coeur d’Alene River basin: Environmental Science and Technology, v. 37, p. 4694–4701.

Beckwith, M.A., Berenbrock, Charles, and Backsen, R.L., 

1996, Magnitude of floods in northern Idaho, February 

1996: U.S. Geological Survey Fact Sheet 222–96.

Bookstrom, A.A., Box, S.E., Campbell, J.K., Foster, K.I., and 

Jackson, B.L., 2001, Lead-rich sediment, Coeur d’Alene 

River valley, Idaho; area, volume, tonnage and lead content: 

U.S. Geological Survey Open-File Report 01–140, 77 p.

Bookstrom, A.A., Box, S.E., Jackson, B.L., Brandt, T.R., Derkey, P.D., and Munts, S.R., 1999, Digital map of surficial 

geology and wetlands, Coeur d’Alene River valley, Idaho: 

U.S. Geological Survey Open-File Report 99–548, 121 p., 

11 sheets, scales 1:24,000, 1:60,000.

Box, S.E., Bookstrom, A.A., Ikramuddin, Mohammed, and 

Lindsay, James, 2001, Geochemical analyses of soils and 

sediments, Coeur d’Alene drainage basin, Idaho; sampling, 

analytical methods and results: U.S. Geological Survey 

Open-File Report 01–139, 230 p.

Box, S.E., and Wallis, J.L., 2002, Surficial geology along the 

Spokane River, Washington, and its relationship to the metal 

contents of sediments: U.S. Geological Survey Open-File 

Report 02–126, 54 p., scale 1:24,000.

Edwards, T.K., and Glysson, G.D., 1999, Field methods for 

measurement of fluvial sediment: U.S. Geological Survey 

Techniques of Water Resources Investigations Report TWI 

03–C2, 89 p.

Ellis, M., 1940, Pollution of the Coeur d’Alene River and 

adjacent waters by mine wastes: U.S. Bureau of Fisheries 

Special Scientific Report 1, 61 p. [available from U.S. Fish 

and Wildlife Service, Washington, D.C.].

Fousek, R.S., 1996, Trace element distributions in the sediments of the floodplain and river banks of the South Fork 

and Coeur d’Alene Rivers, Shoshone and Kootenai Counties, 

Idaho: Auburn, Ala., Auburn University, M.S. thesis, 310 p.

Fryklund, V.C., Jr., 1964, Ore deposits of the Coeur d’Alene 

district, Shoshone County, Idaho: U.S. Geological Survey 

Professional Paper 445, 139 p.

Golder Associates, 1996, Test pit logs, soil/sediment analytical results, and contaminated sediment volume estimates, 

Osburn reach of South Fork of Coeur d’Alene River: Kellogg, Idaho, consultant report to Idaho Silver Valley Natural 

Resources Trust Fund, 68 p.

Grosbois, C.A., Horowitz, A.J., Smith, J.J., and Elrick, 

K.A., 2001, The effect of mining and related activities on 

the sediment-trace element geochemistry of Lake Coeur 

d’Alene, Idaho, U.S.A. Part III, Downstream effects; the 

Spokane River basin: Hydrological Processes, v. 15, no. 5, 

p. 855–875.
Hooper, R.L., and Mahoney, J.B., 2000, Constraining contaminant transport: lead and zinc speciation in fluvial subenvironments, lower Coeur d’Alene River valley, Idaho [abs.]: 

Geological Society of America Abstracts with Programs, v. 

32, no. 7, p. 125.

Horowitz, A.J., Elrick, K.A., and Cook, R.B., 1993, Effect of 

mining and related activities on the sediment trace element 

geochemistry of Lake Coeur d’Alene, Idaho, USA. Part I, 

Surface sediments; Hydrological Processes, v. 7, p. 403–423.

Horowitz, A.J., Elrick, K.A., Robbins, J.A., and Cook, R.B., 

1995, Effect of mining and related activities on the sediment 

trace element geochemistry of Lake Coeur d’Alene, Idaho, 

USA. Part II, Subsurface sediments: Hydrological Processes, v. 9., p. 35–54.

Horowitz, A.J., Rinella, F.A., Lamothe, Paul, Miller, T.L., 

Edwards, T.K., Roche, R.L., and Rickert, D.A., 1990, Variations in suspended sediment and associated trace element 

concentrations in selected riverine cross sections: Environmental Science and Technology, v. 24, p. 1313–1320.

Kjelstrom, L.C., 1996, Gaging stations with 10 or more years 

of record, v. 1 of Statistical summaries of streamflow data 

for selected gaging stations in Idaho and adjacent States 

through September 1990: U.S. Geological Survey WaterResources Investigations Report 94–4069, 533 p.

Kuwabara, J.S., Berelson, W.M., Balistrieri, L.S., Woods, P.F., 

Topping, B.R., Steding, D.J., and Krabbenhoft, D.P., 2000, 

Benthic flux of metals and nutrients into the water column 

of Lake Coeur d’Alene, Idaho, report of an August 1999 

pilot study: U.S. Geological Survey Water-Resources Investigations Report 00–4132, 74 p.

Long, K.R., 1998, Production and disposal of mill tailings in 

the Coeur d’Alene mining region, Shoshone County, Idaho; 

preliminary estimates: U.S. Geological Survey Open-File 

Report 98–595, 14 p.

Long, K.R., DeYoung, J.H., Jr., and Ludington, S.D., 1998, 

Database of significant deposits of gold, silver, copper, lead, 

and zinc; part A, Database description and analysis: U.S. 

Geological Survey Open-File Report 98–206–A, 33 p.

McCulley, Frick & Gilman, Inc., 1995, Engineering evaluation/cost analysis for the Canyon Creek site: Osburn, Idaho, 

prepared for Idaho Silver Valley Natural Resource Trustees, 

34 p.

Paulson, A.J., 1996, Fate of metals in surface waters of the 

Coeur d’Alene basin, Idaho: U.S. Bureau of Mines Report 

of Investigations 9620, 75 p.

Paulson, A.J., 2001, Biogeochemical removal of Zn and Cd 

in the Coeur d’Alene River (Idaho, USA), downstream of a 

mining district: Science of the Total Environment, v. 278, p. 

31–44.

Paulson, A.J., Balderrama, Robert, and Zahl, Eric, 1996, 

Treatment of fluvially deposited streamside mine waste—

material from Canyon Creek, Idaho: U.S. Bureau of Mines 

Report of Investigations 9633, 58 p.

Terragraphics Environmental Engineering, Inc., 1996, Smelterville Flats soil data report: Boise, Idaho, unpublished 

report to Idaho Department of Health and Welfare, 31 p.

U.S. Environmental Protection Agency, 1998, Bunker Hill 

Facility basin-wide RI/FS data report—sediment contamination in the lower Coeur d’Alene River basin (LCDARB); 

geophysical and sediment coring investigations in the river 

channel, lateral lakes and floodplains: Seattle, consultant 

report prepared by URS Greiner, Inc., and CH2M Hill, 2 v.

U.S. Geological Survey, 1984, National handbook of recommended methods for water-data acquisition (revised ed.): 

Reston, Va., 692 p.

U.S. Geological Survey, 1996, Upper Columbia River Basin 

and Snake River Basin below King Hill, v. 2 of Water 

resources data, Idaho—water year 1995: U.S. Geological 

Survey Water-Data Report ID–95–2, 357 p.

U.S. Geological Survey, 1997, Upper Columbia River Basin 

and Snake River Basin below King Hill, v. 2 of Water 

resources data, Idaho—water year 1996: U.S. Geological 

Survey Water-Data Report ID–96–2, 377 p.

U.S. Geological Survey, 1998, Upper Columbia River Basin 

and Snake River Basin below King Hill, v. 2 of Water 

resources data, Idaho—water year 1997: U.S. Geological 

Survey Water-Data Report ID–97–2, 357 p.

Woods, P.F., and Beckwith, M.A., 1997, Nutrient and trace 

element enrichment of Coeur d’Alene Lake, Idaho: U.S. 

Geological Survey Water-Supply Paper 2485, 93 p.

Woods, P.F., and Berenbrock, Charles, 1994, Bathymetric 

map of Coeur d’Alene Lake, Idaho: U.S. Geological Survey 

Water-Resources Investigations Report 94–4119, scale 

1:48,000.

References Cited 33

Tables 1–3
1 South Fork at Twomile Creek --------------------------------------------------- 02/09/96 47o28 32 115o54 51 12.5 616 2 South Fork at the Smelterville bridge ------------------------------------------- 02/09/96 47o28 29 115o55 20 22.4 1,388 3 South Fork above Pine Creek ---------------------------------------------------- 02/10/96 47o30 36 115o59 33 25.3 104 4 Coeur d’Alene River at Kingston --------------------------------------------------------------- 02/09/96 47o32 55 116o10 27 27.8 534 5 Coeur d’Alene River at the Idaho Highway 2 bridge at Cataldo--------------------------------------------------------------- 02/09/96 47o32 55 116o13 17 32.0 490 6 Coeur d’Alene River above Dudley --------------------------------------------------------------- 02/09/96 47o33 12 116o16 09 37.3 52 7 Coeur d’Alene River below Rose Lake --------------------------------------------------------------- 02/09/96 47o32 53 116o20 04 43.4 426 8 Coeur d’Alene River at Anderson Lake inlet ------------------------------------------ 02/10/96 47o32 39 116o24 43 61.4 138 9 Canyon Creek at mouth ---------------------------------------------------------- 02/09/96 47o32 04 116o30 54 7.0 14 

10 Ninemile Creek at mouth --------------------------------------------------------- 02/09/96 47o27 56 116o45 47 7.5 699 

11 South Fork at Enaville ------------------------------------------------------------ 01/02/97 47o31 47 116o02 05 26.7 104 

12 Canyon Creek at mouth ---------------------------------------------------------- 01/02/97 47o33 34 116o15 03 7.0 7 13 Big Creek at mouth --------------------------------------------------------------- 01/02/97 47o28 22 115o54 50 15.8 25 14 Government Gulch at mouth ---------------------------------------------------- 01/02/97 47o32 44 116o09 59 22.2 1,471 15 Page Creek above tailings pond ------------------------------------------------- 01/02/97 47o32 24 116o12 09 24.3 60 16 Pine Creek above mouth --------------------------------------------------------- 01/02/97 47o32 51 116o13 31 25.3 119 

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Table 1. Analytical data for samples of suspended sediment collected from the Coeur d’Alene-Spokane River system, northern Idaho and easterduring high-water events in 1996 and 1997.[See figures 1 and 2 for locations. Samples grouped by sampling date and listed from upstream to downstream. Samples from tributaries near their mouths are listed separately fdate. n.a., not analyzed]
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17 Spokane River at the Stateline bridge --------------------------------------------------------------- 05/02/97 47o41 55 117o02 36 98.3 3 18 Spokane River at the Centennial Trail bridge --------------------------------------------------- 05/02/97 47o41 37 117o14 55 110.2 4 19 Spokane River at the Gonzaga University bridge --------------------------------------------------------------- 05/02/97 47o39 49 117o24 08 119.0 5 20 Spokane River at the 7-Mile bridge --------------------------------------------------------------- 05/02/97 47o44 28 117o31 07 132.4 16 21 South Fork at Larsen -------------------------------------------------------------- 05/20/97 47o28 01 115o43 59 -3.2 1.4 22 South Fork at Mullan ------------------------------------------------------------- 05/20/97 47o28 12 115o47 34 0.0 23 23 South Fork below the Morning Mine ------------------------------------------- 05/20/97 47o27 58 115o48 48 1.3 32 24 South Fork above Canyon Creek ------------------------------------------------ 05/20/97 47o28 21 115o54 40 6.9 102 25 South Fork at west end of Wallace ---------------------------------------------- 05/20/97 47o28 37 115o55 57 8.0 92 26 South Fork at Twomile Creek ---------------------------------------------------- 05/20/97 47o30 36 115o59 33 12.5 11 27 South Fork at the Evolution bridge --------------------------------------------- 05/20/97 47o31 00 116o01 56 14.3 58 28 South Fork at Enaville ------------------------------------------------------------ 05/20/97 47o33 34 116o15 03 26.7 83 29 Coeur d’Alene River at the Idaho Highway 2 bridge at Cataldo----------------------------------------------- 05/20/97 47o32 52 116o20 02 32.0 20 30 Coeur d’Alene River at the Idaho Highway 3 bridge ----------------------------------------------- 05/20/97 47o31 25 116o30 49 44.2 20 31 Spokane River at the Idaho Highway 95 bridge ------------------------------ 05/20/97 47o41 11 116o47 54 83.6 2 32 Spokane River above the Post Falls dam -------------------------------------- 05/19/97 47o42 33 116o57 06 92.3 3 33 Spokane River at the Stateline footbridge ------------------------------------- 05/19/97 47o41 45 117o02 18 98.0 4 34 Spokane River at Sullivan Rd --------------------------------------------------- 05/19/97 47o40 22 117o11 45 106.7 9 35 Spokane River at the Gonzaga University bridge ----------------------------- 05/19/97 47o39 49 117o24 08 119.0 5 36 Mill Creek above Mullan --------------------------------------------------------- 05/20/97 47o28 19 115o48 01 0.2 5 

37 Canyon Creek above mouth ----------------------------------------------------- 05/20/97 47o28 32 115o54 51 7.0 7 

38 Ninemile Creek above mouth ---------------------------------------------------- 05/20/97 47o28 37 115o55 11 7.5 11 

39 Big Creek at mouth ---------------------------------------------------------------- 05/20/97 47o31 47 116o02 05 15.8 4 

40 Pine Creek, 1 mi south of Pinehurst --------------------------------------------- 05/20/97 47o31 09 116o14 26 25.3 1 41 Flooded field southwest of Interstate Highway 90 ---------------------------- 05/20/97 47o34 03 116o24 47 37.9 15 42 Fourth of July Creek at mouth --------------------------------------------------- 05/20/97 47o32 38 116o25 30 37.9 0.3 

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Table 1. Analytical data for samples of suspended sediment collected from the Coeur d’Alene-Spokane River system, northern Idaho and easterduring high-water events in 1996 and 1997.—Continued
1 South Fork at Twomile Creek --------------------------------------------------- 2 South Fork at the Smelterville bridge ------------------------------------------ 3 South Fork above Pine Creek ---------------------------------------------------- 4 Coeur d’Alene River at Kingston ----------------------------------------------- 5 Coeur d’Alene River at the Idaho Highway 2 bridge at Cataldo------------ 6 Coeur d’Alene River above Dudley -------------------------------------------- 7 Coeur d’Alene River below Rose Lake ---------------------------------------- 8 Coeur d’Alene River at Anderson Lake inlet --------------------------------- 9 Canyon Creek at mouth ----------------------------------------------------------- 10 Ninemile Creek at mouth --------------------------------------------------------- 11 South Fork at Enaville ------------------------------------------------------------ 12 Canyon Creek at mouth ----------------------------------------------------------- 13 Big Creek at mouth ---------------------------------------------------------------- 14 Government Gulch at mouth ----------------------------------------------------- 15 Page Creek above tailings pond -------------------------------------------------

16 Pine Creek above mouth ----------------------------------------------------------

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64 853 2.2 0.46 15.9 55 14 

102 767 2.0 0.34 15.7 45 14 

87 831 2.7 0.33 20.1 70 17 

58 732 2.3 0.65 9.0 62 18 

44 813 2.7 0.42 4.7 76 14 

72 897 3.3 0.53 9.8 75 17 44 880 3.0 0.53 7.4 68 16 

158 661 2.0 0.33 24.0 34 14 

64 593 2.3 0.48 63.1 35 19 

39 793 2.5 0.74 28.1 62 18 

61 634 2.2 0.26 36.9 74 16 63 525 2.6 0.57 77.9 72 24 

83 700 2.1 0.33 1.2 71 12 

275 936 2.3 0.46 79.0 80 74 

35 659 2.7 0.58 16.0 82 21 

46 577 2.2 0.18 3.0 77 11 

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Table 1. Analytical data for samples of suspended sediment collected from the Coeur d’Alene-Spokane River system, northern Idaho and during high-water events in 1996 and 1997.—Continued
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17 Spokane River at the Stateline bridge ------------------------------------------18 Spokane River at the Centennial Trail bridge ---------------------------------

19 Spokane River at the Gonzaga University bridge ----------------------------

20 Spokane River at the 7-Mile bridge --------------------------------------------21 South Fork at Larsen --------------------------------------------------------------22 South Fork at Mullan -------------------------------------------------------------23 South Fork below the Morning Mine -------------------------------------------24 South Fork above Canyon Creek ------------------------------------------------25 South Fork at west end of Wallace ----------------------------------------------26 South Fork at Twomile Creek ----------------------------------------------------

27 South Fork at the Evolution bridge ---------------------------------------------28 South Fork at Enaville ------------------------------------------------------------29 Coeur d’Alene River at the Idaho Highway 2 bridge at Cataldo------------30 Coeur d’Alene River at the Idaho Highway 3 bridge ------------------------31 Spokane River at the Idaho Highway 95 bridge ------------------------------32 Spokane River above the Post Falls dam --------------------------------------33 Spokane River at the Stateline footbridge -------------------------------------34 Spokane River at Sullivan Rd ---------------------------------------------------35 Spokane River at the Gonzaga University bridge -----------------------------36 Mill Creek above Mullan ---------------------------------------------------------

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30 602 2.3 0.93 28.5 87 18 

17 486 2.0 1.10 22.5 65 14 49 665 2.8 1.09 28.6 95 19 

23 761 2.4 1.58 12.9 100 19 25 835 2.1 1.01 2.5 79 11 

29 1,012 2.7 0.58 2.7 83 12 

36 1,113 2.7 0.59 5.3 95 13 

20 1,025 2.0 0.31 5.4 63 9 

22 884 1.8 0.33 9.8 64 9 27 1,034 2.2 0.40 14.2 74 12 29 872 1.7 0.32 14.9 31 11 

64 751 2.1 0.40 21.7 59 17 

62 707 2.3 0.36 21.1 69 19 

46 711 2.6 0.31 10.3 52 25 

38 619 2.5 0.82 17.1 86 23 33 557 2.0 1.19 35.5 80 16 

39 589 2.1 1.09 66.6 86 18 

61 691 3.2 1.38 18.9 96 20 

55 835 3.7 1.41 31.6 130 25 

25 1,266 2.0 0.90 14.3 48 18 

37 Canyon Creek above mouth -----------------------------------------------------

38 Ninemile Creek above mouth ----------------------------------------------------39 Big Creek at mouth ----------------------------------------------------------------40 Pine Creek, 1 mi south of Pinehurst ---------------------------------------------41 Flooded field southwest of Interstate Highway 90 ----------------------------42 Fourth of July Creek at mouth ---------------------------------------------------

94 598 1.8 0.85 52.8 77 26 

22 555 2.9 0.84 48.6 76 17 

35 650 1.6 0.68 1.9 67 17 

24 498 2.1 0.74 2.3 66 12 

27 584 2.1 0.70 3.8 107 26 

110 545 1.6 1.32 24.6 66 21 

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Table 1. Analytical data for samples of suspended sediment collected from the Coeur d’Alene-Spokane River system, northern Idaho and during high-water events in 1996 and 1997.—Continued
1 South Fork at Twomile Creek ----------------------------------------------------- 2 South Fork at the Smelterville bridge -------------------------------------------- 3 South Fork above Pine Creek ----------------------------------------------------- 4 Coeur d’Alene River at Kingston ------------------------------------------------- 5 Coeur d’Alene River at the Idaho Highway 2 bridge at Cataldo-------------- 6 Coeur d’Alene River above Dudley ---------------------------------------------- 7 Coeur d’Alene River below Rose Lake ------------------------------------------ 8 Coeur d’Alene River at Anderson Lake inlet ----------------------------------- 9 Canyon Creek at mouth ------------------------------------------------------------ 10 Ninemile Creek at mouth ---------------------------------------------------------- 11 South Fork at Enaville -------------------------------------------------------------- 12 Canyon Creek at mouth ------------------------------------------------------------ 13 Big Creek at mouth ----------------------------------------------------------------- 14 Government Gulch at mouth ------------------------------------------------------ 15 Page Creek above tailings pond --------------------------------------------------- 16 Pine Creek above mouth ----------------------------------------------------------- ������ �������� 113 4.69 15 2.99 24 0.76 2,770 

139 6.50 14 2.69 19 0.60 4,318 

119 5.31 19 3.25 31 0.75 3,182 2 

82 4.82 17 2.76 27 0.81 2,092 3 59 4.24 19 3.15 32 0.95 1,330 

106 5.91 22 3.84 30 1.13 2,306 2 

72 5.83 22 3.61 28 1.23 1,776 2 

122 10.10 13 2.42 14 0.76 7,882 322 6.40 13 2.29 15 0.50 3,771 7 186 5.42 17 2.75 27 0.60 2,831 2 

111 4.06 16 2.76 32 0.54 2,573 

412 5.61 15 2.34 31 0.50 4,515 3 

122 2.84 14 3.28 31 0.60 1,308 

1,401 3.54 18 2.30 35 0.42 2,291 4 

87 3.48 18 3.06 38 0.53 1,328 2 54 3.32 17 3.39 32 0.53 620 

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during high-water events in 1996 and 1997.—Continued
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17 Spokane River at the Stateline bridge ------------------------------------------18 Spokane River at the Centennial Trail bridge ---------------------------------

19 Spokane River at the Gonzaga University bridge -----------------------------20 Spokane River at the 7-Mile bridge ---------------------------------------------21 South Fork at Larsen --------------------------------------------------------------22 South Fork at Mullan -------------------------------------------------------------23 South Fork below the Morning Mine -------------------------------------------24 South Fork above Canyon Creek ------------------------------------------------25 South Fork at west end of Wallace ----------------------------------------------

26 South Fork at Twomile Creek ----------------------------------------------------

27 South Fork at the Evolution bridge ----------------------------------------------28 South Fork at Enaville ------------------------------------------------------------29 Coeur d’Alene River at the Idaho Highway 2 bridge at Cataldo------------30 Coeur d’Alene River at the Idaho Highway 3 bridge -------------------------31 Spokane River at the Idaho Highway 95 bridge -------------------------------32 Spokane River above the Post Falls dam ---------------------------------------33 Spokane River at the Stateline footbridge --------------------------------------34 Spokane River at Sullivan Rd ----------------------------------------------------35 Spokane River at the Gonzaga University bridge -----------------------------36 Mill Creek above Mullan ---------------------------------------------------------

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103 4.70 16 1.72 32 1.13 2,871 1 127 3.46 13 1.54 26 0.92 1,840 1 

98 4.65 17 1.99 37 1.28 2,735 2 

57 5.33 20 2.34 44 1.33 1,660 1 58 2.65 14 2.26 35 0.70 1,303 1 

310 3.08 16 3.15 36 0.76 2,147 2 

269 3.20 16 3.83 41 0.78 2,211 2 

114 2.87 13 2.82 25 0.62 1,626 1 

103 2.71 13 2.66 27 0.59 1,574 1 120 3.37 16 3.16 32 0.75 1,936 1 127 3.08 14 2.70 11 0.62 1,818 1 

112 3.98 15 2.56 22 0.64 3,042 1 

96 4.13 15 2.70 29 0.67 3,355 1 82 4.78 18 2.62 19 0.66 1,931 2 

276 5.59 17 2.06 35 0.92 3,681 2 

100 4.10 15 1.71 31 1.00 1,890 2 299 4.53 15 1.85 32 1.10 2,415 1 127 4.86 18 2.24 38 1.46 2,296 2 288 6.42 22 2.64 52 1.69 3,423 2 

89 3.15 13 2.00 20 0.29 5,145 2 

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37 Canyon Creek above mouth -----------------------------------------------------38 Ninemile Creek above mouth ----------------------------------------------------39 Big Creek at mouth ----------------------------------------------------------------40 Pine Creek, 1 mi south of Pinehurst ---------------------------------------------41 Flooded field southwest of Interstate Highway 90 ----------------------------42 Fourth of July Creek at mouth ---------------------------------------------------

265 5.57 14 2.27 33 0.43 3,408 5 

197 4.41 16 2.30 35 0.44 2,699 3 

93 2.88 12 2.23 29 0.66 1,297 2 

165 3.19 13 2.05 31 0.54 936 2 

67 5.09 15 1.82 41 0.57 1,934 2 

176 10.77 8 0.70 27 0.62 6,756 3 

Table 1. Analytical data for samples of suspended sediment collected from the Coeur d’Alene-Spokane River system, northern Idaho and eduring high-water events in 1996 and 1997.—Continued
1 South Fork at Twomile Creek ---------------------------------------------------- 2 South Fork at the Smelterville bridge ------------------------------------------- 3 South Fork above Pine Creek ---------------------------------------------------- 4 Coeur d’Alene River at Kingston ----------------------------------------------- 5 Coeur d’Alene River at the Idaho Highway 2 bridge at Cataldo------------ 6 Coeur d’Alene River above Dudley -------------------------------------------- 7 Coeur d’Alene River below Rose Lake ---------------------------------------- 8 Coeur d’Alene River at Anderson Lake inlet --------------------------------- 9 Canyon Creek at mouth ----------------------------------------------------------- 10 Ninemile Creek at mouth --------------------------------------------------------- 11 South Fork at Enaville ------------------------------------------------------------ 12 Canyon Creek at mouth ----------------------------------------------------------- 13 Big Creek at mouth ---------------------------------------------------------------- 14 Government Gulch at mouth ----------------------------------------------------- 15 Page Creek above tailings pond -------------------------------------------------

16 Pine Creek above mouth ----------------------------------------------------------

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4,035 147 41 <1 66 12 1,713 0.79 

6,360 129 70 3 64 10 1,491 0.85 

4,235 164 45 <1 65 14 1,936 0.87 

1,765 136 26 3 97 12 2,046 0.87 

1,075 165 15 <1 68 14 2,245 0.87 

2,480 194 29 <1 64 16 2,651 1.03 

2,060 184 17 4 62 15 2,965 1.01 

5,925 112 47 2 41 9 1,252 0.70 

17,310 110 181 10 75 9 1,628 0.65 

11,280 130 87 1 174 13 2,333 0.80 

3,832 157 28 4 52 15 1,813 0.9 

13,929 126 136 8 75 13 1,834 0.9 

294 141 42 3 40 13 1,321 0.9 

3,087 147 73 8 103 16 2,747 2.0 3,693 154 26 4 96 17 2,318 1.0 

674 168 9 4 45 14 1,630 0.8 

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Table 1. Analytical data for samples of suspended sediment collected from the Coeur d’Alene-Spokane River system, northern Idaho and easterhigh-water events in 1996 and 1997.—Continued
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17 Spokane River at the Stateline bridge ------------------------------------------18 Spokane River at the Centennial Trail bridge ---------------------------------

19 Spokane River at the Gonzaga University bridge -----------------------------20 Spokane River at the 7-Mile bridge ---------------------------------------------21 South Fork at Larsen --------------------------------------------------------------22 South Fork at Mullan --------------------------------------------------------------23 South Fork below the Morning Mine -------------------------------------------24 South Fork above Canyon Creek ------------------------------------------------25 South Fork at west end of Wallace ----------------------------------------------

26 South Fork at Twomile Creek ----------------------------------------------------

27 South Fork at the Evolution bridge ----------------------------------------------28 South Fork at Enaville ------------------------------------------------------------29 Coeur d’Alene River at the Idaho Highway 2 bridge at Cataldo------------30 Coeur d’Alene River at the Idaho Highway 3 bridge -------------------------31 Spokane River at the Idaho Highway 95 bridge -------------------------------32 Spokane River above the Post Falls dam ---------------------------------------33 Spokane River at the Stateline footbridge --------------------------------------34 Spokane River at Sullivan Rd ----------------------------------------------------35 Spokane River at the Gonzaga University bridge -----------------------------36 Mill Creek above Mullan ---------------------------------------------------------

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1,404 110 9 4 98 15 3,074 0.7 

898 88 7 6 106 11 2,916 0.7 

1,293 123 8 7 118 17 3,363 0.8 

532 139 4 5 189 18 2,285 0.8 

180 132 4 3 97 13 1,924 0.7 

510 172 15 4 63 15 1,720 1.2 846 185 15 14 61 16 1,373 1.2 929 155 13 4 35 13 1,760 0.9 

1,563 150 15 4 41 12 1,128 0.9 2,096 187 22 5 50 15 1,738 1.1 2,098 110 21 4 41 9 1,368 0.9 2,618 133 32 3 81 12 1,811 0.9 1,909 147 19 4 60 14 1,733 0.9 1,233 99 13 4 58 10 2,331 0.8 2,318 132 13 14 62 17 2,580 0.9 1,275 105 8 30 116 14 3,102 0.8 

1,611 118 11 9 106 15 3,043 0.8 

1,324 139 8 19 151 19 2,565 1.0 2,015 164 12 10 145 26 2,790 1.1 

3,005 130 13 6 78 12 1,553 0.9 

37 Canyon Creek above mouth -----------------------------------------------------38 Ninemile Creek above mouth ----------------------------------------------------39 Big Creek at mouth ----------------------------------------------------------------40 Pine Creek, 1 mi south of Pinehurst ---------------------------------------------41 Flooded field southwest of Interstate Highway 90 ----------------------------42 Fourth of July Creek at mouth ---------------------------------------------------

9,793 124 126 8 123 15 2,106 0.7 

10,100 132 46 9 206 16 2,228 0.8 

224 119 51 4 80 11 1,995 0.8 698 130 7 8 80 15 2,250 0.7 398 107 4 3 101 15 2,269 0.6 929 49 5 6 110 11 1,480 0.3 

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Table 1. Analytical data for samples of suspended sediment collected from the Coeur d’Alene-Spokane River system, northern Idaho and eastern Washevents in 1996 and 1997.—Continued
1 South Fork at Twomile Creek --------------------------------------------------- 2 South Fork at the Smelterville bridge ------------------------------------------ 3 South Fork above Pine Creek ---------------------------------------------------- 4 Coeur d’Alene River at Kingston ----------------------------------------------- 5 Coeur d’Alene River at the Idaho Highway 2 bridge at Cataldo------------ 6 Coeur d’Alene River above Dudley -------------------------------------------- 7 Coeur d’Alene River below Rose Lake ---------------------------------------- 8 Coeur d’Alene River at Anderson Lake inlet --------------------------------- 9 Canyon Creek at mouth ---------------------------------------------------------- 10 Ninemile Creek at mouth --------------------------------------------------------- 11 South Fork at Enaville ------------------------------------------------------------ 12 Canyon Creek at mouth ---------------------------------------------------------- 13 Big Creek at mouth --------------------------------------------------------------- 14 Government Gulch at mouth ---------------------------------------------------- 15 Page Creek above tailings pond ------------------------------------------------

16 Pine Creek above mouth ---------------------------------------------------------

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3 17 2,820 682 13 2,515 552 15 3,280 75

11 16 1,505 65

3 19 838 723 19 1,560 893 19 1,280 722 11 4,065 427 11 9,580 444 20 5,348 723 14 4,575 719 16 19,567 544 14 340 553 17 4,370 926 22 3,545 822 10 1,179 59

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Table 1. Analytical data for samples of suspended sediment collected from the Coeur d’Alene-Spokane River system, northern Idaho and eastern Washington, during high-water events in 1996 and 1997.—Continued
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17 Spokane River at the Stateline bridge ---------------------------------------------------------------18 Spokane River at the Centennial Trail bridge ---------------------------------------------------19 Spokane River at the Gonzaga University bridge ---------------------------------------------------------------20 Spokane River at the 7-Mile bridge ---------------------------------------------------------------21 South Fork at Larsen --------------------------------------------------------------22 South Fork at Mullan -------------------------------------------------------------23 South Fork below the Morning Mine -------------------------------------------24 South Fork above Canyon Creek ------------------------------------------------25 South Fork at west end of Wallace ----------------------------------------------

26 South Fork at Twomile Creek ----------------------------------------------------

27 South Fork at the Evolution bridge ----------------------------------------------28 South Fork at Enaville ------------------------------------------------------------29 Coeur d’Alene River at the Idaho Highway 2 bridge at Cataldo-----------------------------------------------

30 Coeur d’Alene River at the Idaho Highway 3 bridge -----------------------------------------------31 Spokane River at the Idaho Highway 95 bridge -------------------------------32 Spokane River above the Post Falls dam ---------------------------------------33 Spokane River at the Stateline footbridge --------------------------------------34 Spokane River at Sullivan Rd ----------------------------------------------------35 Spokane River at the Gonzaga University bridge -----------------------------36 Mill Creek above Mullan ---------------------------------------------------------

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4 28 3,068 847 21 2,430 659 31 3,169 963 33 1,690 1103 20 378 632 17 482 722 15 907 583 13 889 843 15 1,625 513 14 2,433 682 7 2,494 643 11 3,805 673 15 3,762 703 12 2,403 68

39 29 3,708 9512 31 3,046 45

7 31 3,440 94

11 35 3,489 87

9 36 4,234 934 13 2,038 68

37 Canyon Creek above mouth ----------------------------------------------------38 Ninemile Creek above mouth ---------------------------------------------------39 Big Creek at mouth ---------------------------------------------------------------40 Pine Creek, 1 mi south of Pinehurst --------------------------------------------41 Flooded field southwest of Interstate Highway 90 ---------------------------42 Fourth of July Creek at mouth ---------------------------------------------------

6 14 5,818 507 21 9,398 599 16 492 55

12 14 1,264 56

5 24 561 709 27 2,401 58

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Table 1. Analytical data for samples of suspended sediment collected from the Coeur d’Alene-Spokane River system, northern Idaho and eastern Washington, during high-water events in 1996 and 1997.—Continued
Table 2. Analytical data for samples of overbank sediment from the South Fork and main stem of the Coeur d’Alene River, northern deposited during high-water events in 1995 and 1996. [See figure 3 for locations. Samples are grouped by sampling data and depositional environment (streambank or marsh) and listed from upstream to downs

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43 North bank above the Idaho Highway 2 bridge ---------------------- Coarse sand 47o32 57 116o20 03 02/2

44 North bank above the Idaho Highway 2 bridge ---------------------- Silt to fine sand 47o32 57 116o20 03 02/2

45 North bank at Cataldo Mission boat launch -------------------------- Silty mud 47o33 13 116o21 59 02/2

46 North bank above Fourth of July Creek ------------------------------- Fine sand 47o32 37 116o25 23 02/2

47 South bank below the Rose Lake bridge ------------------------------ Fine sand 47o32 10 116o28 19 02/2

48 North bank above the Idaho Highway 3 bridge ---------------------- Fine sand 47o31 27 116o30 47 02/2

49 South bank below the Smelterville bridge ---------------------------- Medium to coarse sand 47o32 55 116o10 30 03/2

50 South bank above Pine Creek ------------------------------------------- Muddy silt 47o32 54 116o13 13 03/2

51 South bank at Kingston -------------------------------------------------- Silty fine sand 47o33 07 116o16 28 03/2

52 South bank above railroad bridge at Cataldo ------------------------- Fine sand 47o33 22 116o19 12 03/2

53 North bank above the Idaho Highway 2 bridge ---------------------- Medium to coarse sand 47o32 55 116o20 04 03/2

54 North bank at the Mission boat launch -------------------------------- Muddy silt 47o33 10 116o21 57 03/2

55 South bank below the Rose Lake bridge ------------------------------ Fine sand 47o32 10 116o28 19 03/2

56 North bank 1 mi above the Idaho Highway 3 bridge ---------------- Medium sand 47o32 05 116o30 33 03/2

57 South bank at the Medimont boat launch ----------------------------- Fine to medium sand 47o28 40 116o35 37 03/2

58 North bank at the Thompson Lake inlet boat launch ---------------- Very fine sand 47o29 08 116o43 26 04/

59 North bank above the Harrison bridge -------------------------------- Silt to fine sand 47o27 58 116o45 49 04/

60 Field near the town of Cataldo ----------------------------------------- Silty mud 47o33 14 116o19 21 03/2

61 Cataldo Mission parking lot -------------------------------------------- Silty mud 47o33 04 116o21 31 03/2

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62 Lane Marsh, south edge ------------------------------------------------- Clay to fine silt 47o30 33 116o31 39 03/2

63 Medicine Lake marsh ---------------------------------------------------- Silt 47o28 38 116o35 24 03/2

64 Cave Lake, southeast shore --------------------------------------------- Clay to fine silt 47o28 04 116o35 20 03/2

65 Bare Marsh, west edge -------------------------------------------------- Fine silt 47o29 11 116o43 15 04/

66 Thompson Lake, north shore ------------------------------------------- Fine silt 47o29 38 116o43 51 04/
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43 North bank above the Idaho Highway 2 bridge -------------------44 North bank above the Idaho Highway 2 bridge -------------------45 North bank at Cataldo Mission boat launch -----------------------46 North bank above Fourth of July Creek ---------------------------47 South bank below the Rose Lake bridge --------------------------48 North bank above the Idaho Highway 3 bridge ------------------49 South bank below the Smelterville bridge -------------------------50 South bank above Pine Creek ---------------------------------------51 South bank at Kingston ----------------------------------------------52 South bank above railroad bridge at Cataldo ----------------------53 North bank above the Idaho Highway 2 bridge -------------------54 North bank at the Mission boat launch -----------------------------55 South bank below the Rose Lake bridge ---------------------------56 North bank 1 mi above the Idaho Highway 3 bridge -------------57 South bank at the Medimont boat launch --------------------------58 North bank at the Thompson Lake inlet boat launch -------------59 North bank above the Harrison bridge -----------------------------60 Field near the town of Cataldo --------------------------------------61 Cataldo Mission parking lot -----------------------------------------

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32.0 2.8 4.44 52 442 1.1 0.12 4.

32.0 2.8 4.72 72 502 1.2 0.32 8.

34.4 15.1 3.59 224 428 1.2 0.25 11.

37.8 12.3 3.70 118 563 1.0 0.35 43.

40.8 12.5 3.46 111 577 0.9 0.36 49.44.1 10.7 2.86 110 529 0.8 0.35 43.22.4 11.2 5.11 90 654 1.9 0.31 13.

24.9 18.6 5.13 103 678 1.7 0.37 22.

27.9 8.7 6.51 83 677 2.1 0.48 10.

31.0 8.6 5.61 68 555 1.6 0.35 9.

32.0 6.7 6.18 81 643 2.1 0.27 8.

34.4 6.6 7.62 68 676 2.1 0.45 8.

40.8 17.8 3.84 78 503 1.1 0.31 41.

43.2 15.7 5.39 109 734 1.6 0.44 46.

50.9 14.3 3.44 99 518 1.1 0.42 31.

59.0 15.1 4.05 141 571 1.4 0.41 24.

61.4 15.8 3.29 135 509 1.1 0.31 29.

31.1 6.5 5.36 36 552 1.6 0.32 8.

34.4 5.4 7.48 52 641 2.2 0.44 6.

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62 Lane Marsh, south edge ----------------------------------------------63 Medicine Lake marsh -------------------------------------------------64 Cave Lake, southeast shore ------------------------------------------65 Bare Marsh, west edge -----------------------------------------------66 Thompson Lake, north shore ----------------------------------------

46.8 4.6 8.62 44 842 2.8 0.32 6.

50.8 11.5 3.74 107 616 1.4 0.38 28.

51.0 1.4 6.37 17 578 1.8 1.10 3.

58.9 4.9 5.83 54 644 2.2 0.73 10.

59.0 7.5 6.74 87 788 2.3 0.34 13.

Table 2. Analytical data for samples of overbank sediment from the South Fork and main stem of the Coeur d’Alene River, northerdeposited during high-water events in 1995 and 1996.—Continued
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6 6 37 4.41 11 1.94 23 0.47 

10 7 57 4.24 13 1.99 28 0.55 

13 7 158 4.52 13 1.89 13 0.38 

9 6 122 9.53 9 1.47 20 0.62 9 5 132 9.47 9 1.36 14 0.59 9 5 114 10.05 7 1.16 16 0.57 

15 8 119 7.20 12 2.37 15 0.52 

14 6 137 5.03 12 1.98 13 0.51 

15 7 115 4.21 15 2.39 17 0.65 

11 8 71 4.18 12 2.09 24 0.59 

10 6 67 6.28 12 2.64 13 0.74 14 10 68 4.56 16 2.53 29 0.80 

8 6 121 10.81 9 1.74 14 0.66 1

11 7 136 10.78 11 1.98 21 0.79 

9 5 96 10.52 8 1.53 13 0.65 

11 6 88 9.36 9 1.64 14 0.62 

10 5 95 10.34 8 1.43 11 0.57 

8 7 61 5.62 12 1.94 19 0.57 

12 10 59 3.89 15 2.54 30 0.77 

62 Lane Marsh, south edge -----------------------------------------------63 Medicine Lake marsh -------------------------------------------------64 Cave Lake, southeast shore -------------------------------------------65 Bare Marsh, west edge ------------------------------------------------66 Thompson Lake, north shore -----------------------------------------

12 16 56 4.49 19 3.99 28 0.85 

11 7 110 9.31 10 1.72 16 0.61 

13 8 39 3.49 14 2.08 33 0.72 

13 9 105 4.80 14 2.32 21 0.68 

11 12 89 5.81 17 2.84 20 0.71 

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Table 2. Analytical data for samples of overbank sediment from the South Fork and main stem of the Coeur d’Alene River, northern Iddeposited during high-water events in 1995 and 1996.—Continued
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43 North bank above the Idaho Highway 2 bridge --------------------44 North bank above the Idaho Highway 2 bridge --------------------45 North bank at Cataldo Mission boat launch ------------------------46 North bank above Fourth of July Creek ----------------------------47 South bank below the Rose Lake bridge ----------------------------48 North bank above the Idaho Highway 3 bridge --------------------49 South bank below the Smelterville bridge --------------------------50 South bank above Pine Creek ----------------------------------------51 South bank at Kingston -----------------------------------------------52 South bank above railroad bridge at Cataldo ----------------------53 North bank above the Idaho Highway 2 bridge -------------------54 North bank at the Mission boat launch -----------------------------55 South bank below the Rose Lake bridge ---------------------------56 North bank 1 mi above the Idaho Highway 3 bridge -------------57 South bank at the Medimont boat launch --------------------------58 North bank at the Thompson Lake inlet boat launch -------------59 North bank above the Harrison bridge ------------------------------60 Field near the town of Cataldo ---------------------------------------61 Cataldo Mission parking lot ------------------------------------------

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11 10 264 1,662 96 29 3 43 

14 16 506 1,625 86 20 3 53 

86 33 370 2,247 74 78 3 27 

8 13 235 4,564 75 48 2 36 4 12 254 5,010 70 51 2 32 6 11 181 4,633 59 45 2 26 3 15 417 3,835 106 58 1 71 3 17 503 4,950 76 62 1 69 2 22 698 2,610 84 47 1 83 12 15 497 2,410 97 28 <1 59 13 17 381 2,050 90 35 1 56 2 22 696 1,960 111 22 <1 71 12 11 223 4,315 77 38 2 29 3 18 444 6,430 90 51 2 46 12 12 272 3,315 65 37 2 32 3 15 405 4,680 73 36 2 41 2 12 252 3,970 65 40 <1 29 4 16 466 3,295 99 32 4 59 2 20 654 1,540 122 18 1 67 1

62 Lane Marsh, south edge -----------------------------------------------63 Medicine Lake marsh -------------------------------------------------64 Cave Lake, southeast shore -------------------------------------------65 Bare Marsh, west edge ------------------------------------------------66 Thompson Lake, north shore -----------------------------------------

2 28 727 1,614 184 20 31 63 11 16 446 4,309 74 37 4 44 1 17 694 574 93 6 8 151 16 134 880 1,693 123 20 79 83 11 21 596 2,548 143 31 7 53 1

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Table 2. Analytical data for samples of overbank sediment from the South Fork and main stem of the Coeur d’Alene River, northern Iddeposited during high-water events in 1995 and 1996.—Continued
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63 Medicine Lake marsh --------------------------------------------------64 Cave Lake, southeast shore -------------------------------------------65 Bare Marsh, west edge ------------------------------------------------66 Thompson Lake, north shore -----------------------------------------

1.00 3.0 83 6 17 1,021 78

0.60 3.0 40 2 9 4,062 52

0.70 2.0 77 4 18 507 80

0.70 2.0 58 3 11 1,649 66

0.90 3.0 72 4 12 1,961 71

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Table 2. Analytical data for samples of overbank sediment from the South Fork and main stem of the Coeur d’Alene River, northern Idaho, deposited during high-water events in 1995 and 1996.—Continued
Table 3. Daily metal loads in suspended sediment at selected sampling sites in the Coeur d’Alene-Spokane River system, northern Idaho and eas[See figures 1 and 2 for location w data for each sampling date, extrapolated from mean daily streamflow measured at nearby U.S. Geological Survey gaging stations (U.S. Geological Survey, 1997, 1998)]

1 South Fork at Twomile Creek ------------------------------------ 12.5 616 6,000 4,035 2,820 4.69 9,947 82 South Fork at the Smelterville bridge --------------------------- 22.4 1388 8,000 6,360 2,515 6.50 29,861 373 South Fork above Pine Creek ------------------------------------ 25.3 104 9,900 4,235 3,280 5.31 2,772 24 Coeur d’Alene River at Kingston -------------------------------- 27.8 534 56,000 1,765 1,505 4.82 80,367 285 Coeur d’Alene River at the Idaho Highway 2 bridge --------- 32.0 490 56,000 1,075 838 4.24 73,773 156 Coeur d’Alene River above Dudley ----------------------------- 37.3 52 56,000 2,480 1,560 5.91 7,841 37 Coeur d’Alene River below Rose Lake ------------------------- 43.4 426 56,000 2,060 1,280 5.83 64,151 268 Coeur d’Alene River at Anderson Lake inlet------------------- 61.4 138 56,000 5,925 4,065 10.10 20,849 249 Canyon Creek at mouth ------------------------------------------- 7.0 14 1,000 17,310 9,580 6.40 38 

11 South Fork at Enaville --------------------------------------------- 104 3,850 3,832 4,575 4.06 1,075 

12 Canyon Creek at mouth ------------------------------------------- 7.0 7 225 13,929 19,567 5.61 4 

13 Big Creek at mouth ------------------------------------------------ 15.8 25 200 294 340 2.84 13 

17 Spokane River at the Stateline bridge --------------------------- 98.3 3 34,800 1,404 3,068 4.70 270 

18 Spokane River at the Centennial Trail bridge ------------------ 110.2 4 34,800 898 2,430 3.46 381 

19 Spokane River at the Gonzaga University bridge ------------- 119.0 5 34,800 1,293 3,169 4.65 424 20 Spokane River at the 7-Mile bridge ----------------------------- 132.4 16 34,800 532 1,690 5.33 1,511 

27 South Fork at Evolution bridge ---------------------------------- 14.3 58 1,637 2,098 2,494 3.08 257 

28 South Fork at Enaville -------------------------------------------- 26.7 83 2,650 2,618 3,805 3.98 590 

29 Coeur d’Alene River at the Idaho Highway 2 bridge --------- 32.0 20 12,100 1,909 3,762 4.13 636 

30 Coeur d’Alene River at the Idaho Highway 3 bridge --------- 44.2 20 12,100 1,233 2,403 4.78 636 

31 Spokane River at the Idaho Highway 95 bridge --------------- 83.6 2 43,200 2,318 3,708 5.59 179 

32 Spokane River above the Post Falls dam ----------------------- 92.3 3 43,200 1,275 3,046 4.10 372 33 Spokane River at the Stateline footbridge ---------------------- 98.0 4 43,200 1,611 3,440 4.53 512 

34 Spokane River at Sullivan Rd ------------------------------------ 106.7 9 43,200 1,324 3,489 4.86 1,081 

35 Spokane River at the Gonzaga University bridge ------------- 119.0 5 43,200 2,015 4,234 6.42 536 

37 Canyon Creek above mouth ------------------------------------- 7.0 7 290 9,793 5,818 5.57 5 

39 Big Creek at mouth ------------------------------------------------ 15.8 4 253 224 492 2.88 3 

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