Baseline Deposition Rates, LeadRich Sediment, Coeur dAlene CdA River Floodplain, Idaho Arthur Bookst

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Baseline Deposition Rates, Lead-Rich Sediment,
Coeur dAlene (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.

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Location map
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Production and Tailings Management
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History of Flooding
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Block Diagram of Floodplain
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Star Mill - south fork Coeur d Alene River
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1933 Flood Smelterville Flats, Idaho
Rose Lake, Idaho
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Lead in Surficial Sediments
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Section of Pb-Rich Sediments
1980 Mt. St. Helens volcanic ash layer
Riverbank near Medimont in 1993
Base of section of Pb-rich sediments
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Lead-Concentration Profiles
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Pre- and Post-1969 Rates of Sediment Deposition
in Medicine Lake
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Summary of Baseline Depositional Rates and Lead
Concentrations
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Baseline Depositional Rates
1.8
3.0
7.4
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Lateral Variation in Baseline Rates of Sediment
Deposition
28.5
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Baseline Lead Concentrations
1500
2800
4500
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Lateral Variation in Baseline Lead Concentrations
7500
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Box plots of historic and baseline
sediment-deposition rates
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Box plots of Pb concentrations in sediments of
successive time intervals
n 13
n 13
90th percentile
75th
4000
50th
3300
25th
10th
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.
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Percentages of tailings-derived Pb in
sediments by drainage basin, and by
depositional setting
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Lead Concentrations in Suspended Sediment
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1996 Scour of Pb-Rich Sediments in the River
near Dudley
Approximate location of drill hole 94VCD2
River bottom before 1996 flood
Sandy active bed sediment (poorly stratified)
Scoured zone
Stored Pb-rich sediments (well stratified)
Log exposed by flood scour
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Secondary Sourcesof Pb-Rich Sedimentin the
River Channel