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French Broad River
04-03-02
Dispersion of Cranston Print Works Effluent
Introduction
The Intensive Survey crew of the Division of Environmental Management
conducted a dispersion study of Cranston Print Works effluent in a 4.2 mile
reach of the French Broad River on 10-31-79. This river reach is from the
confluence of Cane Creek and the river, to the Glenn Bridge (SR 3495 -Buncombe
County). The study was requested by Roy Davis, the Regional Engineer of the
Division of Environmental Managements Asheville Regional Office, to assist
the City of Asheville in arriving at a decision regarding the location of a
raw water intake from the west side of the river at the Glenn Bridge.
Cranston Print Works outfall pipe discharges 2.1 MGD to the eastern
side of the river approximately 100 ft. upstream of the mouth of Cane Creek.
Cane Creek is a tributary that discharges an average flow of 81 cfs to the
eastern side of the river, 2800 ft. downstream of the Butler Bridge (SR 1345 -
Henderson County). The outfall pipe extends out into the river approximately
five feet, and on the date of the study the top quarter of the pipe was
exposed. Six liters of a fluorescent dye, Rhodamine W.T. (20% solution or
200,000 ppm) was poured into the effluent at the end of the pipe at 0900. A
canoe was used to visually track the dye on the surface as it moved downstream,
in order to determine when the dye cloud dispersed laterally across the river.
This was noted at 0958 approximately 100 ft. downstream the Fanning Bridge
(SR 1419 -Henderson County). Dye samples to run on a Turner Model III Fluoro-
meter were also taken at three points across the river at the Fanning Bridge
and the Glenn Bridge. The three points were left bank, middle, and right bank
looking upstream. The sampling points on the Fanning Bridge with the river
being 162 ft. wide were at 40.5 ft., 81 ft., and 121.5 ft., from left to right.
The sampling points on the Glenn Bridge with the river being 200 ft. wide were
at 50 ft., 100 ft., and 150 ft., from left to right. The samples were taken at
a depth of one foot. Bottom samples were taken at the middle station and from
this data it was determined that the river was completely mixed vertically.
Results
Dye concentration curves for the Fanning Bridge (FB -1) and Glenn Bridge
(FB -2) stations are plotted in the attached figures. Extrapolating from the
mixing information obtained for this slug input of dye to the mixing characteristics
for the continuous input of the Cranston Print effluent can best be accomplished
by looking at the areas under the dye concentration curves from dye data obtained
at various points across the stream. This will give an indication of the relative

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amounts of dye running through each section of the river and thus the relative
amounts of waste running through each section. The values found for these areas
under the dye concentration curves can be compared against what would be expected
under conditions of complete mixing. Under completely mixed conditions the dye
curve areas would be exactly equal, or we could sat that out of 100% total area,
each curve would contain 33.3%•
When the areas under the dye concentration curves are measured at the
Fanning Bridge station, the comparative values obtained at this station are 60%
of the dye at the left bank, 31% in the middle, and 9% at the right bank. To
obtain a number value for mixing, it could be said that the waste would be
9%/33.3% - 27% mixed at the right bank of the Fanning Bridge, or, put another
way, the waste concentration at Fanning Bridge would be 27% of the concentration
expected under complete mixing conditions. If the same procedure is used at the
Glenn Bridge, it is found that the left bank had 45% of the total, the middle 31%,
and the right bank 24% of the dye. Thus, mixing has increased to about 24$/33.3% •
72% complete at the Glenn Bridge.
One may conclude that the concentration of Cranston Print waste in the
French Broad passing by the right bank at Glenn Bridge in approximately 72% of
the concentration which would be expected under complete mixing conditions. Mote
that this mixing percentage would apply only at a river flow of 1678 cfs as
measured by the USGS gage on the French Broad River at Bent Creek. This was the
flow at the time of the study. The average discharge at this gage over the last
42 years is 1679 cfs.
Location Map - Figure #1
Time -of -Travel - Table #1
Fanning Bridge Dye Curve - Figure #2
Glenn Bridge Dye Curve - Figure #3
Dye Concentrations - Table #2
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REACH: French Broad River from the confluence of Cane Creek to the Glenn Bridge
Sta,
No.
Location
Date
Peak
Time
Travel
Time,
hrs.
Cum.
Time,
hrs.
Veloc-
ity,
ft/sec.
Length,
mi.
Di St.
from
Injec-
tion,
mi.
Stream
Dis-
charge,
cfs
Slope
ft/mi.
Cranston Print Works
10/31/79
0900
PB -1
Right Bank
Fanning Bridge-
10131/79
o9s4
S4 min
54 min
2.S2
1.5s1.
FB- 1
Fanning Bridge-
Middlein
min
2.48
1
FB -1
Fanning Bridge -
Left Bank
10/31/79
0956
56 min
56 min
2.44
1.55
1.55
W
J
I--
FB-2
Tennridge-
Right Bank
10/31/79
1208
2hr 14min
3hr 8min
1.74
2.65
4.2
FB -2
Glenn Bridge -
Middle
10/31/79
1152
lhr 57min
2hr 52mis
1.99
2.65
4.2
F5-2
Glenn Bridge -
Left nk10/31/7L-2h
1 mi
8min
•2
Bent Creek gaic
1 10/31/79
1325
1678cfs