Most of the upstream samples were not collected
on the same dates as the downstream samples. The upstream data represent
an average for a period that precedes or includes the date of the downstream
sample. In Table 10 the number of observations is the number of samples
in the average, while the number of days is the period that was included
in the average. The comparison is somewhat complicated by the fact that
there is a variable travel time through the reservoir. The travel time
is affected by the flow and by the reservoir content. In addition stratification
within reservoir can dictate the formation of currents that can short-circuit
travel through the reservoir. High concentrations of TSS will also affect
the density of the inflowing water; this can also affect the way in which
the water is routed through the reservoir. What all of this means is that
the comparison in Table 10 is something of an oversimplification of a complex
situation. Nevertheless Table 10 provides an example of what happens in
the reservoir.
There are two mechanisms that can affect
the TSS concentration in the reservoir. The first is settling. When the
flowing water enters the reservoir, the velocity declines significantly
as the inflow mixes with the water already in the reservoir. The ability
to transport sediment is greatly affected by velocity. As the velocity
declines, the ability to transport sediment decreases, depositing the sediment.
The deposition is related to the size and composition of the particles.
In general, the larger particles are deposited first, while the finer particles
are transported farther in the reservoir. Some particles may be carried
through the reservoir to the river downstream. This is reflected in the
sediment concentrations in Table 10.
The complete inflow TSS data set is shown
on Figure 11. The plot shows the inflow TSS for the period prior to sample
collection downstream 
from
the dam. The plot is on semi-log axes because the variation in the inflow
TSS concentration and difference between the inflow and outflow TSS are
so large. It should be noted that there are still only 7 samples below
the dam; there appear to be more on figure 11 because of interpolation
between adjacent points in the data set. Since Figure 11 is only intended
as a qualitative illustration, this should not be a problem.
There are several orders of magnitude of
difference between the TSS of the inflow and outflow of Angostura Reservoir
(Table 10; Figure 11). For design purposes, Reclamation assumes that 100
percent of the inflowing sediment will be retained in the reservoir. The
average inflow TSS concentration for the data in Figure 11 is 24,800 mg/L;
the average TSS in the outflow is 52 mg/L. If these are representative
data, then 99.8 percent of the sediment was being retained in the reservoir.
The appearance imparted to water by suspended
material is more of a consideration to most than the actual concentration
of TSS in the water. The measure of the visual effect of TSS is turbidity.
Turbidity data for the Cheyenne River are shown in Table 11. Table 11 also
includes all of the TSS data collected at the inflow site for Angostura
Dam. The samples were collected between 1949 and 1967. The turbidity samples
shown as "Above Dam" were collected at two sites by the TVA (Tennessee
Valley Authority) between 1983 and 1989. The sample sites were above and
below the Edgemont Uranium Mill UMTRA cleanup, but both above the reservoir.
There are a large number of samples. The sample design involved hourly
samples for 24 hours either once a month or following storms. Consequently
the samples are in sets of 24 that are internally aggregated; in other
words they are not independent samples in a statistical sense. From that
perspective, there are considerable fewer than the 1500 samples shown in
Table 11. There are no concurrent TSS samples in the TVA data set.
| Table 11.
Suspended Solids and Turbidity at Three Sites on the Cheyenne River |
|
Above
Dam |
Below
Dam |
Near
Mouth |
|
Suspended
Sediment
Concentration
mg/L |
Turbidity
FTU |
Suspended
Sediment
Concentration
mg/L |
Turbidity
NTU |
Suspended
Sediment
Concentration
mg/L |
Turbidity
JTU & NTU |
|
|
| Minimum |
8 |
< 1 |
10 |
< 1 |
< 1 |
< 1 |
| Median |
14,000 |
17 |
42 |
10 |
390 |
61 |
| Maximum |
68,200 |
14,625 |
86 |
25 |
53,900 |
12,000 |
| # of Obs. |
162 |
1503 |
7 |
7 |
184 |
144 |
FTU - Formazin
Turbidity Unit
JTU - Jackson Turbidity Unit
NTU - Nepholometric Turbidity Unit
|
The turbidity data that are also included
in Table 11 have 3 different measurement units their equivalent abbreviations
are also shown in the table. The original measure of turbidity was the
Jackson candle turbidimeter (APHA, 1992); turbidity was measured in JTU.
The minimum turbidity that the Jackson candle could measure was about 25
JTU (APHA, 1992), a value that would be characteristic of clear pond water
(McKee and Wolfe, 1963). The currently preferred method is to use a turbidimeter
(or nephelometer). The turbidimeter is standardized against a suspension
of formazin polymer. An FTU is any turbidity measure against a formazin
standard. The NTU is an FTU as measured on a nephelometer, which can measure
down to 0.1 NTU. The drinking water standard for turbidity is 1 NTU, which
is assumed to indicate the presence of bacteria. The NTU (= FTU) is equal
to a JTU at 40 units. The measures will deviate from each other as one
moves away from 40 units depending on the instrument used; they are nevertheless
considered equivalent (Fishman and Friedman, 1989).
Table 11 contains both TSS and turbidity
data for a third site near the mouth of the Cheyenne River. Specifically
the site is at the USGS gage at Cherry Creek Village. Of the 144 turbidity
samples collected at the third site, there are 78 with concurrent TSS data.
The turbidity and TSS data show a relatively good correlation (r²
= 0.65). However, when an obvious pair of outliers is dropped from the
data set, the r² improved to 0.95. The equation without the outliers
is:
Turb. = (0.3201 * TSS)
- 3.0294
Based on this equation, turbidity is about
the TSS.
It should be noted that turbidity only
relates in part to the TSS concentration. The turbidity is also affected
by the shape and distribution of particles within the sample. The r²
of 0.95 would indicate that the sediments are comparatively uniform in
size from sample to sample and fine enough to be similarly dispersed throughout
the samples.
The turbidity data shown in Table 11 for
the site below the dam are not actual turbidity measurements. The turbidity
data were developed using the above turbidity equation. How accurate this
might be is unknown since the relationship reflects conditions well downstream
from the dam. If it is accurate, then the dam releases would have a turbidity
of 25 NTU or less. This is consistent with the type of clear water release
that is characteristic of dams.
The TSS samples at the site at Cherry Creek
were collected between June 1972 and August 1995. Obviously this is later
than the TSS samples near the reservoir, but it includes the period during
which the TVA samples were collected. The range of TSS in the samples collected
at the site upstream from the reservoir is somewhat greater than that at
the Cherry Creek gage (Table 11). The turbidity range is also much larger
at the upstream site. Since the reservoir is between the two sites, most
of the sediment at the Cherry Creek gage would be expected to have originated
from inflows downstream from the dam.
The Cheyenne River gage near Wasta also
has limited data on both turbidity and TSS. The Wasta gage is nearest gage
downstream from the project area, but it is also downstream from the Sage
Creek confluence. The 7 turbidity and TSS samples are shown in Table 12
along with stream flows and sample dates. The turbidity samples were collected
in less than a year during 1969-70, while the TSS samples were collected
over a 4-year period during 1983-87 (Table 12). The turbidity samples were
collected over a relatively small range of flow (42-188 ft³/s) and
show a comparably small range. The TSS samples on the other hand were collected
over a very broad range of flow (64-20,300 ft³/s) and show an appropriately
broad TSS range. The TSS data are consistent with the effects of storm
runoff with erosion as the sediment source. It is also consistent with
the DENR (1996) characterization of sediment sources and patterns downstream
from Angostura Dam.
| Table 12.
Flow, Turbidity, and TSS in the Cheyenne River near Wasta |
Sample
Date |
Stream
Flow (ft³/s) |
Turbidity
(JTU) |
Sample
Date |
Stream Flow,
(Inst-ft³/s) |
TSS
(mg/L) |
08/27/69 |
68 |
73 |
06/09/83 |
127 |
108 |
09/24/69 |
90 |
32 |
09/26/83 |
108 |
13 |
10/30/69 |
115 |
45 |
01/04/84 |
64 |
35 |
12/16/69 |
102 |
10 |
06/10/86 |
20,300 |
39,200 |
02/10/70 |
66 |
40 |
03/07/87 |
3,460 |
15,429 |
03/10/70 |
42 |
40 |
06/23/87 |
125 |
475 |
06/10/70 |
188 |
35 |
08/31/87 |
112 |
451 |
The relationships between flow and TSS,
for each of the above discussed gages on the Cheyenne River, along with
one for turbidity at the Cherry Creek gage, are illustrated by the regressions
in Table 13. All of the regressions are statistically significant at an
of level less than or equal to 0.01; the turbidity and flow data presented
in Table 12 for the gage near Wasta do not produce a statistically significant
regression (r² = 0.26). The two seemingly best regression relationships
shown in Table 13 are for the gages below Angostura Dam and near Wasta;
however, both are based on only 7 observations. Because of the limited
data sets on which these are based, the relationships represent a limited
range of conditions and cannot be used as predictive tools. Alternatively,
the r²-values for the other regressions are less than 0.5, indicating
that the regressions explain less than 50 percent of the variation in the
dependent variable (i.e., TSS or turbidity). Because of the small
r²-values, these regressions are not good predictive tools either.
As a generality the regressions indicate that there is a relationship between
the TSS concentration, but it is more complex than what can be quantified
by a simple linear regression.
| Table 13.
Summary of Regressions of TSS on Flow (Q) and Turbidity on Flow at USGS
Gages on the Cheyenne River |
|
Hot Springs
TSS-Q |
below Dam
TSS-Q |
near Wasta
TSS-Q |
at
Cherry Creek
TSS-Q
Turb-Q |
| r² |
0.386 |
0.764 |
0.829 |
0.358 |
0.468 |
| r |
0.621 |
0.874 |
0.911 |
0.598 |
0.684 |
| d.f. |
160 |
5 |
5 |
177 |
138 |
| b1 |
0.745 |
1.248 |
1.229 |
0.975 |
1.260 |
| b0 |
4.712 |
-2.076 |
-1.066 |
0.765 |
-2.909 |
| Begin date |
10/20/49 |
07/11/50 |
06/09/83 |
07/05/72 |
10/03/74 |
| End Date |
08/01/67 |
09/19/50 |
08/31/87 |
08/28/95 |
08/28/95 |
NOTE - the
above regressions are fitted to an equation of the form:
TSS = exp([b1 ln{Q}] + b0) |
Ten different fractions based on particles
sizes have been sampled over the years at the Hot Springs gage near the
reservoir inflow. The different fractions have been sampled with varying
frequencies over the years. Table 14 shows the regressions of the concentrations
as a function of flow; the regressions are in the same form as those in
Table 13. What is interesting about the regressions based on particle size
fractions is that, in general, the r² improves as the size of the
particles increases for particle sizes up to 0.125 mm. The slope of the
regression line also increases up to the same point. This is a reflection
of the fact that the smaller particles are transported independent of flow.
In other words, most any flow is high enough to carry the very finest particles.
As the particles increase in size, transport becomes a factor; i.e.
larger flows are needed to carry the larger particles.
| Table 14.
Regression of Size Fractions of Suspended Solids on Flow |
| Particle
Size |
r²
[%] |
r |
d.f. |
Prob. >
r |
b1 |
b0 |
| <2µm |
6.1% |
0.247 |
96 |
< 0.05 |
0.284 |
6.802 |
| 2-4µm |
8.1% |
0.285 |
142 |
< 0.01 |
0.369 |
5.518 |
| 4-8µm |
25.2% |
0.502 |
81 |
< 0.01 |
0.557 |
3.821 |
| 8-16µm |
19.9% |
0.446 |
141 |
<<
0.01 |
0.654 |
3.966 |
| 16-31µm |
32.9% |
0.573 |
67 |
<<
0.01 |
0.824 |
1.338 |
| 31-62µm |
14.3% |
0.378 |
144 |
<<
0.01 |
0.618 |
3.658 |
| 62-125µm |
58.4% |
0.764 |
63 |
<<
0.01 |
1.236 |
-2.687 |
| 0.125-0.25mm |
77.2% |
0.879 |
20 |
<<
0.01 |
1.309 |
-2.495 |
| 0.25-0.5
mm |
67.4% |
0.821 |
53 |
<<
0.01 |
1.242 |
-2.917 |
| 0.5-1 mm |
63.8% |
0.799 |
28 |
<<
0.01 |
1.030 |
-1.995 |
The regressions shown in Table 14 are plotted
individually against flows between 1 to 6,500 ft³/s on Figure 12A.
The relationships are somewhat confounded by the varying number of samples
in each of the particle data subsets (Table 15). The problem is that the
data are published as cumulative frequency distributions. The concentrations
for the individual size fractions were calculated from the total concentration
by multiplying the TSS by the cumulative frequency for a fraction and subtracting
the similar value for the previous fraction. Where a fraction is missing,
then the calculated concentration is actually the concentration of two
or more size fractions, depending on the intervening number that were not
reported. Since this is not a sediment transport study, but an environmental
impact analysis, this problem is not considered critical to the results.
Most of the curves on Figure 12A are similar
in form. There is a rapid increase at lower flows, followed by an attenuated
increase as the flow increases beyond 1,000 ft³/s. The two exceptions
are the 8-16 µm (10-3 mm) fraction and the and the 0.125-0.25
mm fraction. The 8-16 µm fraction shows a nearly linear increase
continuously to the 6,500 ft³/s maximum shown on the figure. The 0.125-0.25
mm fraction increases at an increasing rate at flows beyond about 2,500
ft³/s. Neither of these trends is sustainable. Each of the regressions
is based on a maximum flow of 6,540 ft³/s with the lone exception
of the 0.125-0.25 mm fraction, which had a maximum flow of only 3420 ft³/s.
The plot of the fraction is being extended well beyond the maximum observed.
In this case such an extrapolation is inappropriate. Alternatively the
reason for the anomaly for the 8-16 µm fraction cannot be explained
based on the data. This may be a reflection of the much smaller number
of samples in the previous size fraction. The smaller data set has the
effect of increasing some of the data in 8-16 µm fraction. For example
the median for the 8-16 µm fraction is much larger than medians for
the adjacent fractions (Table 15).
| Table 15.
Summary Statistics for Flow and Suspended Solids (mg/L) Regressions |
|
Stream
Flow,
ft³/s |
Total
Susp Sed
Conc |
Stream
Flow,
ft³/s |
Susp
Sed
Part. Size
<2µm |
Stream
Flow,
ft³/s |
Susp
Sed
Part. Size
2-4µm |
|
|
|
|
|
|
|
|
|
| Minimum |
18 |
8 |
32 |
124 |
18 |
66 |
| Median |
413 |
14,000 |
443 |
6,449 |
443 |
2,497 |
| Maximum |
6,540 |
68,200 |
6,540 |
38,190 |
6,540 |
39,476 |
| # of Obs. |
162 |
162 |
98 |
98 |
144 |
144 |
|
|
|
|
|
|
|
|
Stream |
Susp Sed |
Stream |
Susp Sed |
Stream |
Susp Sed |
|
Flow, |
Part. Size |
Flow, |
Part. Size |
Flow, |
Part. Size |
|
ft³/s |
4-8µm |
ft³/s |
8-16µm |
ft³/s |
16-31µm |
|
|
|
|
|
|
|
| Minimum |
32 |
46 |
18 |
10 |
32 |
12 |
| Median |
484 |
1,444 |
455 |
3,146 |
608 |
651 |
| Maximum |
6,540 |
12,060 |
6,540 |
53,932 |
6,540 |
63,426 |
| # of Obs. |
83 |
83 |
143 |
143 |
69 |
69 |
|
|
|
|
|
|
|
|
Stream |
Susp Sed |
Stream |
Susp Sed |
Stream |
Susp Sed |
|
Flow, |
Part. Size |
Flow, |
Part. Size |
Flow, |
Part. Size |
|
ft³/s |
31-62µm |
ft³/s |
62-125µm |
ft³/s |
.125-.25mm |
|
|
|
|
|
|
|
| Minimum |
18 |
8 |
42 |
3 |
88 |
12 |
| Median |
453 |
1,452 |
669 |
246 |
1,040 |
670 |
| Maximum |
6,540 |
56,745 |
6,540 |
30,987 |
3,420 |
2,096 |
| # of Obs. |
146 |
146 |
65 |
65 |
22 |
22 |
|
|
|
|
|
|
|
|
Stream |
Susp Sed |
Stream |
Susp Sed |
|
|
|
Flow, |
Part. Size |
Flow, |
Part. Size |
|
|
|
ft³/s |
.25-.5mm |
ft³/s |
0.5-1 mm |
|
|
|
|
|
|
|
|
|
| Minimum |
24 |
1 |
24 |
3 |
|
|
| Median |
653 |
216 |
1,040 |
143 |
|
|
| Maximum |
6,540 |
3,808 |
6,540 |
1,245 |
|
|
| # of Obs. |
55 |
55 |
30 |
30 |
|
|
Figure 12B shows a comparison of the sum
of the concentrations in the various size fractions from Figure 12A and
the concentrations from the TSS-flow regression shown in Table 13. The
results are similar at the lower flows, although the summed TSS increases
somewhat more rapidly. This is a reflection of the effect of the very fine
sediment fraction (< 2 µm), which shows a very rapid increase
at flows less than 1,000 ft³/s (Figure 12A). The two curves diverge
greatly at higher flows and differ by about 12,000 mg/L at 6,500 ft³/s.
At higher flows the sum of the fractions gives a much better estimate of
the TSS than does the regression equation. The measured maximum TSS was
68,000 mg/L (Table 15). The maximum TSS from the sum of the fractions is
65,200 mg/L, while the TSS-Q regression gives a TSS of over 77,000 mg/L.
The above provides the basis for the evaluation
of the effects of the various contract renewal alternatives. Alternatives
that increase the storage, and consequently the amount of time that the
water remains in the reservoir, relative to existing conditions, the more
TSS will be removed from the water. The reverse will also be true and alternative
that decrease the storage will increase the TSS in the releases relative
to existing conditions. However, as long as the dam remains in place, some
sediment would still be removed relative to the TSS of a free-flowing river.
Contaminants
Reclamation collected bed sediment samples
on August 4, 1997. The NIWQP had only sampled bed sediments on 1 date during
the 1988 reconnaissance study of the Angostura Unit, and no sediments were
sampled during the 1994 verification study. The purpose of sampling the
Cheyenne River sediments in 1997 was to update and expand the database
developed by the NIWQP. The NIWQP database include 9 sites between the
Edgemont gage and Red Shirt (see Greene et al., 1990; Table 23).
Reclamation resampled 4 of the NIWQP sites, and sampled 3 other NIWQP sites
where water or biotic samples had been collected, but no sediment sample.
Sample locations and site numbers, which were assigned their NIWQP equivalent
where appropriate, are as follows:
4a. Angostura Reservoir - Inflow Site
4b. Angostura Reservoir - Horsehead Creek
Arm
4c. Angostura Reservoir near Dam
6 Angostura Canal
6S Angostura Canal - split
9 Topeska's Pond
10 Iron Draw
11 Kimmie's Pond
12 Cheyenne River near Custer County Road
656 Bridge
14 Cheyenne River near Fairburn (Red Shirt)
CRRC Cheyenne River at Rapid Creek
CRCC Cheyenne River at Cherry Creek
The two additional sites (CRRC and CRCC)
that were sampled downstream from the NIWQP study area were added to supplement
the data and extend the study area to near the confluence with the Missouri
River. The complete set of Reclamation results are shown in Table 16.
The NIWQP evaluated sediment contamination
by comparing the sample data against a baseline for Western U.S. soils
that was published by Shacklette and Boerngen (1984). The rationale for
this is that most of the stream and lake sediments were derived from eroded
soils and the chemical composition of the sediment should reflect that
origin. The baseline is shown in Table 17 for the elements analyzed in
any samples that are to be used in this report, including those collected
by the NIWQP, Reclamation, the OST, and the CRST. The Shacklette and Boerngen
(1984) baseline does not include all of the elements that were analyzed
in the above referenced studies, e.g. cadmium was not included.
A baseline that is used in exploration
geochemistry is based on crustal abundance values (CAV). These are average
concentrations in the earth's crust; concentrations that are greatly above
these average CAV's are indicative of mineralized areas. In the Cheyenne
Basin, many of the tributaries to the river originate in the Black Hills,
which are predominantly dolomite [CaMg(CO3)2]. Other
parts of the drainage basin are composed of a variety sedimentary rocks.
For this reason abundance values for a variety of sedimentary rocks are
also included in Table 17. Table 17 also illustrates the variability in
the chemical composition of natural materials.
| Table 16.
Sediment Samples - Cheyenne River and Angostura Reservoir during 1997 (All
in ppm, unless otherwise noted) |
|
4a |
4b |
4c |
6 |
6S |
9 |
10 |
11 |
12 |
14 |
CRRC |
CRCC |
| Wet Wgt. [g.] |
16.30 |
14.28 |
15.73 |
18.52 |
18.52 |
16.65 |
14.81 |
14.59 |
16.13 |
17.61 |
15.73 |
12.10 |
| Dry Wgt. [g.] |
6.72 |
3.43 |
4.87 |
13.53 |
13.53 |
5.23 |
9.97 |
9.78 |
13.45 |
10.90 |
9.14 |
8.32 |
| TOC [%] |
1.26 |
0.78 |
1.31 |
0.55 |
0.62 |
3.19 |
0.39 |
1.13 |
0.09 |
0.31 |
0.66 |
0.41 |
| Arsenic |
5.1 |
7.2 |
16.4 |
13.0 |
10.3 |
10.2 |
6.4 |
10.8 |
21.7 |
4.9 |
15.9 |
104.3 |
| Boron |
20 |
27 |
19 |
6 |
5 |
23 |
4 |
14 |
9 |
12 |
12 |
7 |
| Barium |
192 |
146 |
232 |
81 |
47 |
88 |
84 |
157 |
615 |
436 |
561 |
403 |
| Cadmium |
1.3 |
1.5 |
1.4 |
0.6 |
0.6 |
0.7 |
0.3 |
0.7 |
0.2 |
0.6 |
0.5 |
1.9 |
| Chromium |
23.0 |
27.0 |
21.0 |
4.0 |
4.0 |
7.0 |
6.0 |
17.0 |
2.0 |
10.0 |
14.0 |
12.0 |
| Copper |
20.0 |
26.0 |
29.0 |
7.0 |
7.0 |
8.0 |
9.0 |
19.0 |
4.0 |
12.0 |
24.0 |
19.0 |
| Lead |
19 |
< 48 |
< 62 |
< 146 |
< 146 |
< 63 |
< 135 |
< 135 |
< 167 |
21 |
< 116 |
< 138 |
| Molybdenum |
5.9 |
7.3 |
7.5 |
4.0 |
3.0 |
3.9 |
1.9 |
5.4 |
6.9 |
3.4 |
4.7 |
3.9 |
| Nickel |
26.0 |
28.0 |
39.0 |
14.0 |
12.0 |
14.0 |
11.0 |
23.0 |
20.0 |
13.0 |
31.0 |
23.0 |
| Selenium |
1.0 |
0.4 |
1.9 |
0.3 |
0.4 |
1.0 |
0.9 |
0.5 |
0.7 |
0.2 |
0.5 |
0.8 |
| Vanadium |
25.0 |
43.0 |
46.0 |
12.0 |
11.0 |
16.0 |
12.0 |
30.0 |
19.0 |
19.0 |
24.0 |
21.0 |
| Zinc |
59.0 |
97.0 |
95.0 |
28.0 |
24.0 |
71.0 |
36.0 |
317.0 |
52.0 |
40.0 |
91.0 |
63.0 |
| Mercury |
< 0.1 |
< 0.1 |
< 0.1 |
< 0.1 |
< 0.1 |
< 0.1 |
< 0.1 |
< 0.1 |
< 0.1 |
< 0.1 |
< 0.1 |
< 0.1 |
| Thorium |
11.5 |
15.7 |
13.3 |
7.0 |
9.3 |
9.2 |
8.1 |
10.8 |
4.8 |
10.6 |
11.9 |
10.0 |
| Uranium |
4.2 |
5.1 |
5.8 |
2.8 |
3.2 |
17.8 |
2.5 |
3.3 |
2.7 |
3.2 |
3.4 |
3.2 |
| Calcium |
81,297 |
22,709 |
57,734 |
83,481 |
77,696 |
23,348 |
8,196 |
13,901 |
17,437 |
27,619 |
13,860 |
23,286 |
| Magnesium |
22,426 |
10,716 |
6,117 |
4,723 |
3,344 |
2,930 |
1,912 |
6,077 |
1,036 |
4,716 |
6,313 |
5,760 |
| Sodium |
711 |
1,419 |
936 |
271 |
261 |
704 |
341 |
593 |
152 |
1,000 |
854 |
654 |
| Potassium |
5,802 |
7,120 |
4,338 |
801 |
632 |
1,507 |
837 |
2,992 |
308 |
4,039 |
2,522 |
2,051 |
NOTE: TOC
is Total Organic Carbon.
Wet weight is the weight of the sample
as received from the field.
Dry weight is the weight of the sample
after drying, but before grinding. |
| Table 17:
Various baselines for evaluating Cheyenne River sediments [all in ppm] |
|
-------Western
States-------- Soils Baseline |
Crustal
& Sedimentary Rock Abundance Values |
| Element |
Lower C.L. |
Mean |
Upper C.L. |
Earth's
Crust [CAV] |
Clays
&
shales |
Shales |
Sandstones |
Carbonate
rocks |
|
|
|
|
| Arsenic |
1.2 |
5.5 |
22 |
1.8 |
6.6 |
13 |
1 |
1 |
| Boron |
5.8 |
23 |
91 |
9.0 |
100 |
100 |
35 |
20 |
| Barium |
200 |
580 |
1,700 |
390 |
800 |
580 |
< 10 |
10 |
| Calcium |
1,900 |
18,000 |
170,000 |
46,600 |
25,300 |
22,100 |
39,100 |
302,300 |
| Cadmium |
No Data |
No Data |
No Data |
0.2 |
0.3 |
0.3 |
< 0.1 |
0.035 |
| Chromium |
8.5 |
41 |
200 |
122 |
100 |
90 |
35 |
11 |
| Copper |
4.9 |
21 |
90 |
68 |
57 |
45 |
< 1 |
4 |
| Mercury |
0.0085 |
0.046 |
0.25 |
0.086 |
0.4 |
0.4 |
0.03 |
0.04 |
| Potassium |
3,800 |
18,000 |
32,000 |
18,400 |
22,800 |
26,600 |
10,700 |
2,700 |
| Magnesium |
1,500 |
7,400 |
36,000 |
27,600 |
13,400 |
15,000 |
7,000 |
47,000 |
| Molybdenum |
0.18 |
0.85 |
4.0 |
1.2 |
2 |
2.6 |
0.2 |
0.4 |
| Sodium |
2,600 |
9,700 |
37,000 |
22,700 |
6,600 |
9,600 |
3,300 |
400 |
| Nickel |
3.4 |
15 |
66 |
99 |
95 |
68 |
0.2 |
20 |
| Lead |
5.2 |
17 |
55 |
13.0 |
20 |
20 |
7 |
9 |
| Selenium |
0.039 |
0.23 |
1.4 |
0.05 |
0.6 |
0.6 |
0.05 |
0.08 |
| Thorium |
4.1 |
9.1 |
20 |
8.1 |
11 |
12 |
1.7 |
1.7 |
| Uranium |
1.2 |
2.5 |
5.3 |
2.3 |
3.2 |
3.7 |
0.45 |
2.2 |
| Vanadium |
18 |
70 |
270 |
136 |
130 |
130 |
20 |
20 |
| Zinc |
17 |
55 |
180 |
76 |
80 |
95 |
16 |
20 |
Sources:
Western States Baseline: Shacklette and Boerngen, 1984.
C.A.V.: Fortescue, 1992.
Sedimentary rock values: Parker, 1967. |
The comparison to the Western soils baseline
indicates that more often than not, concentrations in the samples were
below the lower confidence limit, rather than above the upper confidence
limit. This is particularly true of barium and chromium among the trace
elements and sodium and potassium among the more common elements; each
of these elements were below the soils baseline at a majority of the sites.
There has been uranium mining and milling
upstream from Angostura Reservoir. Erosion of mine and mill tailings has
been implicated in loading of uranium to the reservoir sediments (Rahn
et
al., 1996; NRC, 1982). Uranium exceeded the upper confidence limit
of the soils baseline at only one of the sites in the reservoir, the site
nearest the dam (site 4c). This would indicate that the uranium was associated
with the finest sediments; coarser particles would settle more quickly
and be deposited nearer the inflow are of the resrvoir. The baseline was
exceeded by the greatest margin in the only other site where the sample
exceeded the uranium baseline, site 9 (Topeska's Pond), which is located
off the river. The sample exceeded the upper limit of the baseline by a
factor of slightly more than 3 (tables 10 and 11) The source for the uranium
in the pond is unknown, but it seems unlikely that it came from the river
or the reservoir.
Molybdenum (Mo) is the only other trace
element that is elevated at more than one sample site. Mo is above the
upper limit of the soils baseline at each of the reservoir sites. The sediments
in
the reservoir originate from areas upstream from Angostura Reservoir. Webb
and Rahn (1994) indicate that the Inyan Kara Group is known to contain
anomalously high concentrations of molybdenum associated with uranium deposits,
some of which are adjacent to the Cheyenne River. The molybdenum could
originate from either uranium mining or natural weathering of these rocks.
The reservoir sediment sample collected
from the reservoir near Angostura Dam had a high concentration of selenium.
Webb and Rahn (1994) also indicate that the same rocks that had the high
concentration of molybdenum, contained high concentrations of selenium.
The selenium could originate from the same source as the molybdenum, but
in apparently finer material, since it was not deposited in the upper areas
of the reservoir.
Arsenic and zinc were also above the upper
confidence limit for Western soils at one site each. The elevated arsenic
was observed in the sample collected from the site at Cherry Creek, which
is located downstream from the mouth of the Belle Fourche River. Arsenic
is a significant pollutant in the former gold fields of the Whitewood Creek
basin. An estimated 100 million metric tons of finely ground gold-mill
tailings were discharged to Whitewood Creek near Lead between 1876 and
1977 (Goddard et al., 1987). The primary contaminant is arsenic
derived from, or still present as arsenopyrite (FeAsS), a gangue mineral
common to the gold deposits around Lead (ibid.). Other elements
identified in the tailings are antimony, cadmium, copper, iron, manganese,
mercury, and silver (ibid.). Whitewood Creek is a tributary to the
Belle Fourche River at the probable source of the arsenic in the sample
from the site near Cherry Creek.
Zinc was elevated relative to the soils
baseline in the sample collected from Kimmie's Pond (site 11). This site
is located off stream; the site was chosen by the NIWQP as potentially
receiving irrigation return flows. No water or sediment samples were collected
from the site by the NIWQP, but biological samples were collected. Zinc
was not elevated at the site (Greene et al., (1990).
The CAV values shown in Table 17 are based
on an assumed average crustal composition that is predominantly igneous
rock (95 percent - see Clarke and Washington, 1924). In an environment
such as that of the AID, this may not be particularly appropriate. In the
Project area, the reservoir, much of its drainage basin, and the Cheyenne
River to a point a couple of miles downstream from Angostura Dam, are underlain
by Mesozoic sedimentary rocks, predominantly shales and limestones (Greene
et
al., 1990). Most of the remainder of the Project area is underlain
by Pierre Shale. Igneous rocks are confined to an area to the north of
the Project area in the headwaters of Beaver Creek (see Greene et al.,
1990 - Figure 2). If the sediments in the Cheyenne River are derived from
the rocks in the drainage basin, the chemical composition should represent
a mix of shale and limestone. Based on the data in tables 10 and 11, the
sediments are principally derived from the shales. This is consistent with
the conclusion of Greene et al. (1990) that their samples were similar
in trace element composition to Department of Energy samples from Foxhills
Sandstone and Pierre Shale surface exposures.
The purpose for sampling the sediments
in this study was to expand the NIWQP data base and to compare the more
recent samples. Selected elements from the 1988 and 1994 NIWQP samples
and the 1997 Reclamation samples are shown on Figure 13. In 1988, the NIWQP
sampled several areas in the reservoir, but the samples were composited
into one sample for analysis in the laboratory; the reservoir was not sampled
in 1994. Reclamation sampled three sites in the reservoir. For purposes
of comparison, the geometric mean of the three Reclamation samples is plotted
on Figure 13.
Arsenic in the reservoir was somewhat higher
in the Reclamation sediment sample than in the NIWQP composite sample (Figure13).
The sediment samples from the tributaries to Angostura Reservoir showed
approximately the same arsenic concentration, but
were intermediate between the NIWQP and
Reclamation sediment samples (Figure 13). The Reclamation sample from the
Angostura Canal was about twice as high in arsenic as the NIWQP 1988 sample.
The highest arsenic in any sample was the Reclamation sample from the county
road 656 bridge, but it was only slightly higher than the NIWQP 1994 sample
(Figure 13). In 1994, the NIWQP collected a sample from the site ¾
mile downstream from Angostura Dam; that sample had an arsenic concentration
of 12 ppm, which is the same as the arsenic concentration in the 1988 sample
from the site near Buffalo Gap. This would indicate that there is an arsenic
source between the site near Buffalo Gap and the one at the county road
bridge. There were no samples collected from the river between the dam
and the bridge site in 1997 that could help identify the source.
The maximum arsenic in the NIWQP samples
was collected from Cottonwood Creek, which had been sampled as a background
site. Cottonwood Creek is downstream from the county road bridge site and
could not be the source of the sediment arsenic. Arsenic in samples from
the remaining two sites located in Iron Draw and the Cheyenne River near
Fairburn are similar in the two sample sets (Figure 13). At each of these
sites, the Reclamation samples are slightly lower in arsenic than NIWQP
samples. Overall the sediments appear to have had a higher concentration
of arsenic in 1997 than was the case in 1988.
In 1988, the Cheyenne River showed an increase
in selenium in the downstream direction as far as Buffalo Gap (Figure 13).
All of the selenium samples collected in 1994 were below the detection
limit of 1 ppm. (Most of the samples collected in 1988 and 1997 were also
less than 1 ppm, but the detection limits were also below 1 ppm). As was
the case for arsenic, the maximum selenium concentration in the 1988 NIWQP
sediment samples was observed in Cottonwood Creek. Selenium then declined
at the site near Red Shirt, despite the inflow from Cottonwood Creek upstream
from the site. In 1997, the results appear to be similar, although fewer
sites were sampled. Selenium was barely measurable at the site near Red
Shirt in 1997.
The final two elements shown on Figure
13 are vanadium and zinc. Both showed relatively high maximum concentrations
in 1988, although both remained within the soils baseline. The reason for
including the data in Figure 13 is to illustrate how much lower the concentrations
are in 1997 than they were in 1988. This was what was expected because
the 1988 samples were collected during a relatively significant drought
period. This makes the above discussed arsenic results even more perplexing.
Figure 14 shows the uranium data for the
NIWQP's 1988 study and the Reclamation samples collected during 1997. The
NIWQP verification 
study
1994 samples were all reported as < 100 ppm, which is well in excess
of any of the 1988 or 1997 results. The NIWQP 1988 and Reclamation's 1997
do not show any pattern between the two years. There is an interspersion
of results with some of the 1988 samples greater than the 1997 samples
at half the common sites (Figure 14). The mean of the Reclamation samples
from the reservoir is twice the concentration in the 1988 NIWQP composite.
On the other hand the NIWQP canal and Iron Draw samples have a greater
uranium concentration than the Reclamation samples. At Red Shirt the Reclamation
sample once again shows the higher uranium concentration (Figure 14). About
all that can be said of uranium based on the two sets of samples collected
in the study area during 1988 and 1997 is that it is highly variable among
the various samples sites. There is no clear pattern of uranium distribution.
There is also no evidence of widespread contamination.
The OST collected sediment samples from
the Cheyenne River at Red Shirt in 1996. Those data along with the NIWQP
1988 and 1994 and the Reclamation 1997 data for that site are plotted on
Figure 14. The plots are shown on a logarithmic scale. There are two plots
on Figure 14 to maintain a maximum of four log cycles (orders of magnitude)
per plot. The upper plot (Figure 15A) includes elements with concentrations
that were less than 100 ppm and ranged from a low of 0.02 ppm for mercury
to a maximum of 56 ppm for boron. The lower plot (Figure 15B) includes
elements that had concentrations between 10 ppm (chromium) and 1200 ppm
(barium). A comparison to Table 17 shows that only the Reclamation molybdenum
sample is above its respective upper 95 percent confidence limit for Western
soils (15 ppm and 4 ppm).
Of the four sampled years shown on Figure
15, 1988 was one of the driest (based on the Wasta gage record), 1994 was
fairly average, 1996 is another rather wet year, and 1997 was the overall
wettest year in the 66 years for which there are data. If there is any
relationship between mean annual flow (or particle size) and bed sediment
concentrations of the elements shown, 1988 (NIWQP) should have the highest
concentration and 1997 (USBR) should have the lowest. This is true for
each of the elements in Figure 15B (Reclamation did not analyze the sample
for manganese), but, with the exception of nickel, and possibly mercury,
it is not true for any of the elements in Figure 15A. Reclamation did analyze
the sample for mercury, but the analytical reporting limit was 0.1 ppm,
which is greater than either of the other results shown in Figure 15A.
Some of the other elements shown in Figure 15A also are affected by reporting
limits. For example, the NIWQP results for both cadmium and molybdenum
are actually reported as less than 2 ppm, which, in the case of cadmium,
is greater than either of the other results. In this instance the actual
concentrations may be greater than those of either the OST or Reclamation,
but there is no way to determine this for sure. Alternatively, the molybdenum
is definitely less than either of the other results.
The CRST initiated a sediment monitoring
project in 1994 (CRST, undated). Results for stations in the vicinity of
Cherry Creek are shown in Table 18. The Reclamation sample collected in
1997 at approximately the same site as CR-40 is also included in Table
18 for comparison. The CRST used clean-up criteria developed by the Washington
Department of Ecology (DoE, 1995) for Puget Sound as evaluation criteria.
The criteria include a "no adverse effect" level and a "minor adverse effect
level." These are used by the DoE to evaluate whether cleanup is needed
in contaminated areas of Puget Sound. None of the CRST samples from the
Cheyenne River in the vicinity of Cherry Creek exceeded the DoE sediment
standards (CRST, undated). The Reclamation sample collected in 1997 did
exceed the DoE criterion for arsenic, but was well below each of the other
criteria (Table 18).
| Table 18.
Sediment Criteria and CRST and Reclamation sediment data for the Cheyenne
River in the vicinity of Cherry Creek |
Element |
Sediment Quality Criteria
Wash. DoE1 |
Cheyenne River Sioux Tribe
|
USBR |
| (Dry Weight Units) |
No effect |
Minor effect |
CR-21 |
CR-38 |
CR-40 |
CR-20 |
CR-39 |
CRCC |
|
|
|
|
|
|
|
|
|
| As, ppm |
57 |
93 |
23.8 |
44.47 |
17.31 |
17.44 |
21.47 |
104.3 |
| Cd, ppm |
5.1 |
6.7 |
0.79 |
1.17 |
0.40 |
0.63 |
0.60 |
1.9 |
| Cr, ppm |
260 |
270 |
16.6 |
29 |
20.5 |
2 |
7.16 |
12.0 |
| Cu, ppm |
390 |
390 |
16.99 |
27.78 |
27.66 |
11.75 |
10.19 |
19.0 |
| Fe, % |
- - - |
- - - |
2.7 |
3.26 |
3 |
5.5 |
2 |
- - - |
| Hg, ppm |
0.41 |
0.59 |
< 0.1 |
< 0.1 |
< 0.1 |
< 0.1 |
< 0.1 |
< 0.1 |
| Mn, ppm |
- - - |
- - - |
332.9 |
552.9 |
516.5 |
2639.9 |
496.6 |
- - - |
| Ni, ppm |
- - - |
- - - |
17.3 |
29.8 |
28.8 |
25.4 |
13.5 |
23.0 |
| Pb, ppm |
450 |
530 |
13.9 |
19.7 |
17.8 |
15.7 |
9.4 |
< 10.0 |
| Zn, ppm |
410 |
960 |
67.0 |
97.0 |
103.0 |
68.0 |
44.5 |
63.0 |
| % solids |
|
|
92.51 |
91.78 |
85.46 |
82.34 |
77.40 |
68.76 |
|
| Sample Site Locations |
Site No. |
Date |
| CHEYENNE RIVER ABOVE
CONFLUENCE OF CHERRY CREEK |
CR-21 |
23-Aug-94 |
| CHEYENNE RIVER ABOVE
CONFLUENCE OF CHERRY CREEK |
CR-38 |
31-Aug-94 |
| CHEYENNE RIVER AT CHERRY
CREEK |
CR-40 |
31-Aug-94 |
| CHEYENNE RIVER BELOW
CONFLUENCE OF CHERRY CREEK |
CR-20 |
23-Aug-94 |
| CHEYENNE RIVER BELOW
CONFLUENCE OF CHERRY CREEK |
CR-39 |
31-Aug-94 |
| CHEYENNE RIVER AT CHERRY
CREEK |
CRCC |
04-Aug-97 |
| 1 Puget Sound
Sediment Quality Chemical Criteria, Washington Department of Ecology |
The primary reason that the CRST sampled
the sediments in streams on their reservation was to evaluate the effect
of floods that occurred throughout the summer of 1993 (CRST, undated).
The Reclamation sample is somewhat higher than the CRST results for arsenic
and cadmium, but within the range shown for the other elements (Table 18).
There is no indication whether the CRST samples were sieved prior to analysis;
the Reclamation sample represents only the < 0.062 mm fraction. If the
CRST samples represent the total sediment, that could account for some
of the difference. For example, Severson et al. (1991) observed
differences among the way different elements were partitioned in different
size-fractions of sediment. Arsenic was tightly clustered about the 45°
line of equal distribution between fine and coarse sediments at lower concentrations,
but showed a great deal of scatter at higher concentrations (> 20 ppm)
of arsenic (ibid.). Despite the one excessive arsenic concentration,
the sediments do not appear to be contaminated with any inorganic substances.
The partitioning of elements by size fractions
is important to any flow relationship. Higher flows are capable of transporting
larger sized sediments than lower flows. If an element is adsorbed to finer
particles, such as clays, then it will tend to be concentrated in the fines.
During periods of low flow, these elements would tend to constitute a larger
part of the suspended sediments, and when deposited, a larger part of the
surface layer of bed sediments. When higher flows are present in wetter
years, larger particles with lower concentrations of the adsorptive elements
will be present. These larger particles are less easily transported, and
thus more readily deposited. The deposition of the larger particles with
lower concentrations of the adsorptive elements will dilute the sediment
concentrations. This is the reason that higher concentrations of some elements
are expected following dry periods.
The CRST also analyzed 5 sediment samples
for pesticides. No measurable pesticides were found in any of the samples,
but only one of the samples was from the mainstem of the Cheyenne River
(CRST, undated, Table 3). The NIWQP analyzed 5 sediment samples for atrazine
and carbofuran. Samples were collected from the Cheyenne River upstream
from Angostura Reservoir, above Buffalo Gap, and near Fairburn; samples
were also collected from Iron Draw and Cottonwood Creek. All of the results
were reported as < 0.1 ppm (Greene et al., 1990).
References
American Public Health Association, American
Water works Association, and Water Environment Federation. 1992. Standard
Methods for the Examination of Water and Wastewater. APHA, Washington,
D.C. Paged by Chapter.
Cheyenne River Sioux Tribe. Undated. Sediment
Monitoring Project, Volume 1: Project Report. Cheyenne River Indian Reservation,
Eagle Butte, South Dakota. 36 pp. + App.
Clarke, F. W., and H.S. Washington. 1924.
The composition of the earth's crust. U.S. Geological Survey Professional
Paper 127. U.S. Government Printing Office, Washington, D.C. 117 pp. (Cited
in Parker, 1967).
Fishman, Marvin J., and Linda C. Friedman.
1989. Methods for the Determination of Inorganic Substances in Water and
Fluvial Sediments. Techniques of Water-Resources Investigations of the
United States Geolocial Survey, Book 5, Cchapter A!. US Government Printing
Office, Washington, D.C. 545 pp.
Fortescue, John A.C. 1992. Landscape geochemistry:
retrospect and prospect--1990. Applied Geochemistry 7:1-53.
Goddard, Kimball E., Arthur J. Horowitz,
and Charles E. Shearer. 1987. Distribution of Solid-Phase Arsenic and Trace
Elements in Bottom and Suspended Sediments, Whitewood Creek and the Belle
Fourche and Cheyenne Rivers, Western South Dakota.
In: U.S. Geological Survey Toxic Substances
Hydrology Program - Surface-Water Contamination: Proceedings of the Technical
Meeting, Denver, Colorado, February 2-4, 1987. Open-file Report 87-764,
USGS, Reston, Virginia. Pp 13-17.
Parker, Raymond L. 1967. Data of Geochemistry,
Sixth Edition, Chapter D. Composition of the Earth's Crust. Geological
Survey Professional Paper 440--D, U.S. Government Printing Office, Washington,
D.C. 19 pp.
Rahn, P.H., A.D. Davis, C.J. Webb, and
A.D. Nichols. 1996. Water quality impacts from mining in the Black Hills,
South Dakota, USA. Environmental Geology 27: 38-53.
Severson, R.C., K.C. Stewart, and Thelma
F. Harms. 1991. Partitioning of Elements Between Two Size Fractions in
Samples from Nineteen Areas of the Western United States. U.S. Geological
Survey, Open-File Report 91-381, USGS, Denver, Colorado. 18 pp.
Shacklette, Hansford T., and Josephine
G. Boerngen. 1984. Element concentrations in Soils and Other Surficial
Materials of the Conterminous United States. U.S. Geological Survey Professional
Paper 1270, U.S. Government Printing Office, Washington, D.C. 105 pp.
Washington Department of Ecology. 1995.
Sediment Management Standards, Chapter 173-204 WAC, (http://www.wa.gov/ecology/sea/smu/173-204.htm),
DoE, Seattle, Washington. 49 pp.
Webb, Cathleen J., and Perry H. Rahn. 1994.
Final Report: Potential Chemical and Environmental Hazards at Abandoned
Mining Sites in the Black Hills. Report to the University of South Dakota,
Vermillion, South Dakota. 117 pp.
