Baseline Deposition Rates, Lead-Rich Sediment, Coeur d’Alene (CdA) River

Floodplain, Idaho

Arthur Bookstrom, Stephen Box, Robert Fousek

• Mill tailings and floods in the CdA drainage basin,• Lead-rich sediments on the CdA River floodplain,• Baseline rates of sediment deposition,• Baseline concentrations of lead (Pb) in sediments,• Secondary sources of Pb-rich sediment,• Continuing deposition of Pb-rich sediments.

Location map

ANNUAL PRODUCTION, CDA MINING DISTRICT, 1886 TO 1990

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1885 1905 1925 1945 1965 1985YEAR

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ES

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ME

TA

LS

(M

EG

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OrePb

Zn

Jig intervalFlotation interval

Post-tailings-release time

Post-1980baselinetime

Tailings lawsuit of 1903

Jig-flotation transition

1968 1980

1893-'94 floods

SF, O, CCtailings damsbuilt 1901-07

O, CC tailings damsdestroyed by

floods of 1917

SF tailings dam destroyed by major flood

of 1933

Dredge at Cataldo Flats (1932-67)

Bunker converts to flotation

~1937

Major floodof 1974

Sand fraction of tailings used for backfill

Bunker Tailings Impoundment (1928-81)

Tailingsreprocessing

Production and Tailings Management

Coeur d'Alene River Flood History: 1886-1997

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46

1886 1896 1906 1916 1926 1936 1946 1956 1966 1976 1986 1996

Ele

vati

on o

f ri

ver

surf

ace @

Dudle

y (

+2100')

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60,000

70,000

80,000

90,000

Flo

w @

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ldo g

age (

cfs

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(column) Dudley spring (column) Dudley winter Cataldo spring Cataldo winter

History of Flooding

Block Diagram of Floodplain

Star Mill - south fork Coeur d’ Alene River

Rose Lake, Idaho

1933 Flood Smelterville Flats, Idaho

Lead in Surficial Sediments

Riverbank near Medimontin 1993

1980 Mt. St. Helensvolcanic ash layer

Base of section ofPb-rich sediments

Section of Pb-Rich Sediments

Lead-Concentration Profiles

DepthMedicine Lake-

bottom sediments, site M92CS.

Time-stratigraphic intervals,

Cs isotopic episodes

(cm) top of drill core (dates)a

Tailings-release interval 137Cs decay (1964 - 1969)

36 bottom of drill core bottom in BA2 interval nd nd nd nd nd nd

(cm)

1.1

sdrAA ~4.3

sdr BA partial interval

9.2

(y/10)

0.5

1.3

10

10 2.3~5.2

~4.8

14

Baseline interval (1980 - 1992)

1.2

Post-tailings-release interval (~1969-1980)

Tailings-release interval 137Cs accumulation,

(1951 - 1964)

sdrAA ~4.3

sdrBA1 ~4.3

18

32

alternating light- and dark-colored

layers of sediments of

partial BA2 interval

16.0

10.8

sdr BA2 partial interval 12.2

8

a.Cs isotopic dating by Rember and others (1993) indicates depths to 1951, 1964 and 1969 time-stratigraphic levels. Depth to 1980 time-stratigraphic level is approximated, assuming AA and BA1 sedimentation rates were about the same (after disposal of tailings into streams ended in 1968-69).

sdr PBR

partial interval

7.8

Sediment-deposition rate (sdr)

(cm/10y)

Time spanDepth span

water-saturated, organic-rich sediments

4.3

Pre- and Post-1969 Rates of Sediment Deposition in Medicine Lake

Littoral Limneticnumber of sites n 125 47 49 18 7 4

Mean + stdev cm/10y 4.7 + 4.3 6.9 + 5.3 3.7 + 3.8 2.5 + 1.7 2.4 + 1.4 3.8 + 0.8

median cm/10y 3.1 6.4 2.8 2.2 2.9 4.0area-wtd average

of medianscm/10y 2.9

Littoral Limneticnumber of sites n 77 20 40 9 5 3

Mean + stdev ppm Pb 3400 + 1500 3400 + 990 3600 + 1600 2800 + 2100 2300 + 900 4100 + 1200

median ppm Pb 3300 3300 3800 1900 2100 4400area-wtd average

of mediansppm Pb 2900

Riverbank Upland Palustrine

Riverbank Upland Palustrine

Summary statistics by depositional settingLacustrineunits

Entire floodplain

LacustrineunitsSediment-

deposition rates

Summary statistics by depositional settingEntire

floodplain

Lead concentrations

Summary of Baseline Depositional Rates and Lead Concentrations

CUMULATIVE FREQUENCY OF BASELINE SEDIMENT-DEPOSITION RATES (1980 ~1993)

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BASELINE SEDIMENT-DEPOSITION RATE (CM/10Y)

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OP

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F S

ITE

S

Floodplain total n = 125

Riverbank n = 47

Upland n = 49

Palustrine n = 18

Littoral n = 7

Limnetic n = 4

Baseline Depositional Rates

1.8 3.0 7.4

BASELINE SEDIMENT-DEPOSITION RATES VERSUS DISTANCE FROM THE RIVER

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0 500 1000 1500 2000 2500

DISTANCE FROM THE CDA RIVER (M)

BA

SE

LIN

E S

ED

IME

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-DE

PO

SIT

ION

RA

TE

(C

M/1

0Y

)

Floodplain total n = 125

Riverbank n = 47

Upland n = 49

Palustrine n = 18

Littoral n = 7

Limnetic n = 4

Lateral Variation in Baseline Rates of Sediment Deposition

28.5

CUMULATIVE FREQUENCY OF LEAD CONCENTRATIONSIN SEDIMENTS OF THE BASELINE INTERVAL (1980 ~1993)

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BASELINE LEAD CONCENTRATION (PPM PB)

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OP

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N O

F S

ITE

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Floodplain total n = 90

Riverbank n = 20

Upland n = 44

Palustrine n = 16

Littoral n = 7

Limnetic n = 3

Baseline Lead Concentrations

1500 2800 4500

LEAD IN BASELINE (AA) SEDIMENTS VERSUS DISTANCE FROM THE RIVER

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DISTANCE FROM CDA RIVER (M)

BA

SE

LIN

E L

EA

D (

PP

M P

B)

Floodplain total n = 90

Riverbank n = 20

Upland n = 44

Palustrine n = 16

Littoral n = 7

Limnetic n = 3

Lateral Variation in Baseline Lead Concentrations

7500

Box plots of historic and baseline sediment-deposition rates

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40S

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IME

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(C

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0Y)

sdrBA (~1903 - 1980) sdrAA (1980 ~1993)

Figure 17. Box-and-whisker plots, comparing sediment-deposition ratesfor sediments of the historic (BA) and baseline (AA) time-stratigraphic intervals.

90th percentile

75th

50th

25th

10th

4.7

3.6

n = 46 n = 46

Box plots of Pb concentrations in sediments of successive time intervals

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ER

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PbBA1 (1968 - 1980) PbAA (1980 ~1993)

Figure 23. Box-and-whisker plots, comparing interval-weighted average lead (ppm Pb) in sediments of the early post-tailings-release (BA1) and baseline (AA) time-stratigraphic intervals.

n = 13n = 13

90th percentile

75th

50th

25th10th

40003300

Percentages of tailings-derived Pb

in sediments by drainage basin,

and by depositional setting

Lead Concentrations in Suspended Sediment

Pb in suspended sediments 1996-97

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-20020406080100120140

River miles downstream from Mullan Idaho

Main 5/20/97Tribs 5/20/97Main 5/2/97Main 1/2/97Tribs 1/2/97Main 2/9/96Tribs 2/9/96Marsh 2/9/96

South Fork

main stem

1996 Scour of Pb-Rich Sediments

in the River near Dudley

Approximate location of drill hole 94VCD2

Log exposed byflood scour

Stored Pb-rich sediments(well stratified)

River bottom before 1996 flood

Scoured zone Sandy active bed sediment(poorly stratified)

Secondary Sourcesof Pb-Rich Sedimentin the River Channel

’96 scour