-------
53
No data are available concerning iron and manganese concentrations at
Roanoke Rapids after completion of Kerr Dam but prior to construction of
Roanoke Rapids I)am; however, comment "by Riddick in his report to the Halifax
Paper Company^" implies that problems had not developed at that time.
Summary
Discharges from John H. Kerr Dam were practically devoid of dissolved
oxygen daring the late summer period as a result of thermal stratification
and low-level power intakes. Reaeration between the dam and Roanoke Rapids
resulted in disaolved oxygen conditions above Roanoke Rapids waste sources
only slightly lower than before Kerr Dam was constructed. Estimates by the
North Carolina Stream Sanitation Committee indicated that minimum flows pro-
vided by Kerr Dam assured a waste assimilative capacity of 109,000 pounds of
BOD per day on weekdays. Since industrial waste discharges were not reduced
on weekends as postulated in establishing the lower weekend flow requirements,
the North Carolina State Stream Sanitation Committee Pollution Abatement Plan
for the Roanoke Rapids-Weldon area was based on the minimum weekday flows.
By 195^ industrial and municipal waste loads had increased to the
extent that the dissolved oxygen content of the lower Roanoke River was
reduced to Ij-.O mg/1 at the minimum flow rates provided by John H. Kerr Dam
during the summer season.
POST-ROANOKE RAPIDS DAM CONDITIONS
The information contained in this section pertains primarily to
(l) dissolved oxygen in Kerr Reservoir, in the discharges from Kerr Dam,
and in the Roanoke River between Kerr Dam and the head of Roanoke Rapids
Reservoir for the period since routine sampling was begun by "VEPCO and the
Corps of Engineers, and (2) dissolved oxygen conditions in and below Roanoke
Rapids Reservoir for the period since completion of Roanoke Rapids Dam.
Above Roanoke Rapids
Observations of dissolved oxygen, temperature, pH, iron, and manganese
have been made in the John H. Kerr Reservoir by VEPCO since 195 ^« Samples
were collected at Buoy No. 1, 1,000 feet upstream from the face of Kerr Dam.
Samples were originally collected at 10-foot intervals of depth but since
1959 have been collected at 5-foot intervals. Since 1957> samples were also
-------
collected at the 1-foot depth. Iron and manganese samples were collected
at 20-foot intervals of depth. Samples were also collected from the scroll
case and tailrace at Kerr Dam, U. S. Highway 1 "bridge, Clements Island (at
the head of Roanoke Rapids Reservoir), Roanoke Rapids Reservoir, the scroll
case and tailrace at Roanoke Rapids Dam, North Carolina Highway 48 "bridge
(at Roanoke Rapids), U. S. Highway 301 bridge (at Weldon), U. S. Highway 258
"bridge (at Scotland Neck), and from the raw and treated water at the Roanoke
Rapids Sanitary District water treatment plant. Samples were generally
collected at two- to four-week intervals during the summer stratification
period, although no sampling was conducted in Kerr Reservoir during the
period of the 1957 joint studies by the Steering Committee for Roanoke River
Studies and the Virginia Electric and Power Company.
The corps of Engineers has collected samples for dissolved oxygen
and temperature since 1956. Samples were collected at Buoy No. 1 at 10-foot
intervals of depth. Samples were also collected at Buoys No. 2, 3, and k
further upstream from the dam in the summer of 1957• Samples were also
collected from the Smith, Dan, and Roanoke Rivers above Kerr Reservoir,
from the scroll case and tailrace at Kerr Dam, and from Eaton's Ferry and
Clement's Island below the 'dam. Samples were collected at two- to four-week
intervals during the summer stratification period.
Between August 3 and September 29, 1954, the North Carolina State
Stream Sanitation Committee collected 14 sets of samples at 4-, 40-, and
90-foot depths from the platform in front of the powerhouse as reported in
the previous section. They also collected 1J sets of samples from the
tailrace in I960. The Committee established D.Q. recorders in the river
at North Carolina Highway 48 bridge in I960, at U. S. Highway 258 in I960
and 1961, and at Eaton's Ferry-in 1961. Other data were collected in con-
nection with the Roanoke River Basin Pollution Survey Report and the 1957
studies by the Steering Committee for Roanoke River Studies.
Annual graphs of the temperature and dissolved oxygen observations
prepared on the basis of the data obtained by the Corps of Engineers and
VEPCO indicate that stratification developed as early as June 1 in Kerr
Reservoir and that a thermocline is identifiable throughout the summer
season. The thermocline is gradually lowered by discharge of hypolimnetic
water through the power penstocks and wind induced mixing. Stratification
is finally and abruptly eliminated in the fall (usually in October) by mixing
due to surface cooling and/or seasonal storms.
-------
55
The VEPGO and Corps of Engineers data indicate that the dissolved oxygen
content of the water near the 'bottom of the reservoir was completely exhausted
in only one (l) year was the lowest dissolved oxygen content of the bottom
sample above 1.0 mg/1. The minimum dissolved oxygen level observed at the
elevation of the top of the turbine intakes has been below 4.0 mg/1 for periods
up to 95 days (1957) and- as low as 0.3 mg/1.* In only one (l) year has the
minimum value remained above 4,0 mg/1. During summer stratification periods
the dissolved oxygen content of the water in the top layers of the reservoir is
generally substantially higher than at the elevation of the power intakes. At
the 10-foot depth D.O. is generally between 7.0 and 9.0 mg/1. The minimum values
at the 10-foot depth and at the elevation of the top of the turbine intakes are
listed in Table XII for each year of observation. The period during which the
dissolved oxygen at the elevation of the top of the power intakes was below
4.0 mg/1 is also included to indicate the period over which minimum tailrace
dissolved oxygen levels will occ'or.
Thirty-five percent of the dissolved oxygen samples collected at the
1-foot depth by VEPCO during July, August, and September exceeded saturation
at the temperature observed. These samples were collected between 9 a.m. and
12:30 p.m. and it would be expected that a larger proportion would be super-
saturated later in the day due to photosynthetic activity. Photosynthesis and
surface reaeration will add to the dissolved oxygen of the reservoir. Both
processes depend on mixing due to wind and temperature fluctuations to transfer
oxygen to the lower levels of the epilimnion.
Samples collected by Kerr Dam personnel and analyzed by the National
Water Quality Network laboratory of the U. S. Public Health Service for plankton
late in September 1961 had a tenfold higher total algae count in the surface
sample than in the sample taken at 50 feet indicating the greater productivity
of the surface waters. Subsequent samples in October confirmed the evidence of
temperature and oxygen observations that the fall overturn had occurred. How-
ever, even the surface sample collected in September was considered to indicate
relatively unproductive water. Thus, photosynthetic activity may be of limited
benefit in increasing the dissolved oxygen content of the surface layers of
Kerr Reservoir, but further information should be secured before its importance
in Ken- Reservoir and in the lower reservoirs can be properly determined.
*
This value was probably due to wind denivellation as are most of the other
extremely low values at intermediate reservoir elevations. Wind denivellation
is the setup or tilting of a lake or reservoir surface resulting from sustained
wind. Of importance is the associated denivellation (or tilting) of the
hypolimnion in the opposite direction, than the water surface. This phenomenon
is discussed in detail by Hutchinson.^°
-------
56
Table XII
Summary of Minimum Dissolved Oxygen Observations
in John H. Kerr Reservoir
10-Foot Depth. Top of Turbine Intakes (Elev. 265)
Year
1954
1955
1956
1957
1958
1959
1960
1961
Min. D.O.
mg/1
6.4
0.2
2.7
6.3
5^
6.5
5.8
4.2
7.1
Date
Oct. 13
Aug. 10
Sept. 15
Sept. 28
Oct. 2
Oct. 1
Sept. 9
Sept. 13
Aug. 16
Min. D.O.
mg/1
2.1
0.3
1.8
3-2
1.5
3-2
2-5
4.3
1.4
Date
Aug. 31
Aug. 10
July 25
July 16
July 17
Aug. 20
Aug. 25
Sept. 13
Aug. 16
Period D.O. was
below 4.0 mg/1
Aug. l4-Sept. 9
July 1-Aug. .24
July 11-July 29
June 24-Sept. 26
Aug. 12 -Aug. 25
June 25 -Sept. 7
None
July 20-Sept. 15
The North Carolina State Stream Sanitation Committee D.O. observations
in Kerr Reservoir were made from the platform above the power intakes in 1954.
These observations probably were made during peaking flows and showed much
higher dissolved oxygen concentrations than were observed at corresponding depths
at Buoy No. 1, 1,000 feet upstream from the dam. The observations made at a
depth of 40 feet (near the elevation of the top of the power intakes) correspond
to observed dissolved oxygen levels as much as 50 feet higher at Buoy No. 1 in
August and early September, and 30 feet higher in late September. At the high
discharges during peaking flows, water is apparently drawn from substantially
higher levels in the reservoir than the penstock opening. Fish commented on the
variations in the dissolved oxygen content which might be observed in the
"adclaustral zone" or area in which high exit velocities and inertial effects
of reducing flow are prominent.3° The drawdown of surface water indicated by
-------
57
these data undoubtedly occurs each day, the extent depending on the discharge
rate, and is effective in improving the dissolved oxygen content of the dis-
charge over that implied by the observations at the intake level at Buoy No. 1.
The elevation of the top of the hypolimnion at Buoy Wo. 1 (as indicated
by the strata of the low D.O. water) has been observed to change over a fairly
wide range. For example, on August 10, 1955, the hypolimnion extended to the
surface and was observed to be at or below 0.^ mg/1 at all depths. On this day
the VEPCO sampling party noted that a brisk northeast wind was blowing. Water
was turbid in the deep water areas and a sharp line of demarcation existed
between the clear and turbid water approximately 200 yards from the north shore.
In the clear water the dissolved oxygen at the 10-foot depth was found to be
2.5 mg/1. On the same day the scroll case D.O. was observed to be 0.0 mg/1,
but the tailrace D.O. was 1.2 mg/1. On August 30 the D.O. at the 10-foot depth
was 6.8 mg/1 while the D.O. exceeded k-.O mg/1 to a depth of 55 feet. The lowest
sample collected at a depth of 90 feet had a D.O. of 2.8 mg/1. On September 15
of the same year relatively low dissolved oxygen levels (2.7 mg/l) were again
noted from the top to near the bottom of the reservoir. Only 15 days later the
dissolved oxygen concentration was 5.2 mg/1 and nearly uniform down to 80 feet.
Similar changes in the levels of hypolimnetic water occurred in most of the
years of observation, but generally involved elevation changes of 20 to 40 feet.
These changes are believed due to wind denivellation and this phenomenon has an
important bearing on the desirability of submerged weirs as corrective measures
in improving the dissolved oxygen concentration of reservoir discharges.
Discharge of water through penstocks located deep in reservoirs has been
reported to stem essentially from the layer in which they are located. ^ FOr
deep reservoirs such as Montana (TVA), only water located below the thermocline
will be discharged. In Kerr Reservoir the thermocline is in the vicinity of
the elevation of the top of the penstocks at the beginning of the stratification
period. Wind mixing in the late spring and the rapidity with which the surface
waters warm are probably the most important factors in determining the elevation
of the thermocline at the beginning of summer stratification. Little control
over these factors seems possible. As the season progresses, the thermocline
is lowered so that an increasing proportion of the oxygenated epilimnetic water
is discharged. The discharge over the summer stratification period (estimated
as July 1 to October 15) exceeds the quantity of water estimated to be in the
hypolimnion at the beginning of the season by a substantial factor as shown in
Table XIII.
-------
Table XIII
Summer Discharge from John H. Kerr Reservoir
- as Initial
Year
1956
1957
1958
1959
I960
1961
Mean
Summer*
Discharge
acre -feet
800,
1,01*0,
1,160,
1,110,
990,
1,150,
i,ote,
000
000
000
000
000
000
000
Volume
in Hypolimnion
Stratification Period
Beginning End
June
June
June
June
June
June
15
1
1
15
15
1
Sept
Sept
Oct.
Oct.
Oct.
Oct.
• 25
. 30
31
15
10
10
Volume of Discharge Volume
Hypolimnion of Hypolimnion
acre-feet** ratio
718,
880,
too,
W2,
310,
718,
583,
000
000
000
000
000
000
000
1
1
2
2
3
1
2
.1
.2
.9
.3
.2
.6
.0
•X-
Estimated as July 1 to October 15.
**Based on the combined Corps of Engineers and Virginia Electric and Power
Company observations.
The duration of dissolved oxygen levels below k.O mg/1 at the top of
the turbine intakes was generally inversely proportional to the ratio of dis-
charge to initial volume stored. The inclusion of substantial amounts of water
from the lower levels of the epilimnion during peaking power discharges is a
significant factor in tailrace D.O.'s through much of the summer stratification
period. The inclusion of this higher D.O. water, together with turbulence in
the tailrace, results in a higher D.O. in the tailrace than that implied by
observations in the hypolimnian opposite the intake.
-------
59
Dissolved oxygen profiles observed at Buoy No. 1 immediately opposite the
intake would not result in the D.O. value observed in the scroll case if complete
mixing took place. Early in its'sampling program, VEPCO personnel commented on
this anomaly.* The scroll case values apparently represent water drawn into the
turbine from near the bottom of the reservoir. Tailrace D.O. observations in
the period of summer stratification are substantially higher than the scroll
case values. The increase in dissolved oxygen between the scroll case and
tailrace is apparently largely due to mixing of higher level, higher dissolved
oxygen water rather than reaeration in the tailrace as has sometimes been
supposed. Observations in Lake Wylie by Duke Power Company"^ showed that the
tailrace D.O. could be estimated from the dissolved oxygen at the several depths,
weighted in proportion to the velocity toward the turbine intake, implying
relatively little reaeration in the tailrace, just as seems to be indicated by
the observations reported for Kerr Reservoir.
Scroll case and tailrace dissolved oxygen observations were included in
both the VEPCO and Corps of Engineers sampling programs. Annual graphs of the
observations indicate that the lowest dissolved oxygen levels occur in August,
although minimum values observed in July and September are almost as low on
occasion. The lowest dissolved oxygen levels occurring in the summer months of
each of the years observations have been made are listed in Table XIV.
Dissolved oxygen observations at the Kerr Dam tailrace were also made
during the 1957 survey by the Steering Committee and VEPCO. On 15 days between
July 22 and September 12 observations extending through most of the peaking flow
period were obtained at maximum flows between 10,000 and 30,000 cfs. The summary
of dissolved oxygen and temperature data reported by the Special Committee for
Roanoke River Studies for stations on the Roanoke River above Roanoke Rapids
are listed in Table XV.
i
J. D. Ristroph, Report on Water Quality - Roanoke River, VEPCO, September 3, 195 4.
-------
60
Table XIV
Minimum Dissolved Oxygen
Year
1954
1955
1956
1957
1958
1959
1960
1961
Mean
Min.
Observations
During the
June
3.8
3.6
4.9
2.5
4.6
3.7
3.6
5-0
4.0
2.5
in John H. Kerr Dam
Summer
July
2.6
1.4
2.3
1.8
2.3
2.0
1.8
1.6
1.9
1.4
Months, 1954
Tailrace
to 1961
Dissolved Oxygen, mg/1
August September
1.7
1.2
1.9
1.9
2.3
1.8
1.2
1.4
1.7
1.2
1-9
3-0
2.2
2.2
3.2
1.8
1.7
1.4
2.2
1.4
October
4.0
6.0
6.0
^.5
6.0
^.3
5-7
4.5
5.1
4.0
-------
61
Table XV
Dissolved Oxygen and Temperature Observations
in the Roanoke River between John H. Kerr Dam and Roanoke Rapids, 1957*
Kerr Tailrace
Ri. Mi. 179
Eaton's Ferry
Ri. Mi. 152
Gaston Site
Ri. Mi. llf-6
N.C. Hwy. ^8 Brdg.
Ri. Mi. 13T
Observed Adjusted**
Maximum
Upper Quartile
Arithmetic Avg.
Weighted Avg.
Median
Lower Quartile
Minimum
Number Observed
3.0
2.5
2.3
1.7
0.3
323
Dissolved Oxygen, mg/1
9.0
6.7
5.6
3.7
336
8.2
7.1
6.6
6.8
6.0
5-2
303
8.6
6.9
6.3
6.3
6.3
5-7
2.7***
1092
8.0
6.7
6.0
6
6
1092
Temperature, °3T.
Maximum
Upper Quartile
Arithmetic Avg.
Weighted Avg.
Median
Lover Quartile
Minimum
Number Observed
76.3
72,8
-
7L9
71.3
69.5
6^.0
318
87.8
76.1
-
Jk.k
73-8
71.7
68.0
338
87.0
75-7
Ik.h
-
73-9
72.9
68. k
307
Si)-. 2
77-8
76.2
76.5
76.1
7^-3
71.0
1082
^Steering Committee for Roanoke River Studies.
**Data adjusted assuming single-wheel operation for flows less than 2,500 cfs.
***Extreme value was due to minimum flows following a density underflow resulting
from a large release from John H. Kerr Dam requested by survey personnel.
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62
In I960 the Korth Carolina State Stream Sanitation Committee and VEPCO made
17 sets of observations at half-hour intervals in the tailrace of Kerr Dam below
one of the operating turbines. At the same time composite samples were collected
for long-term BOD tests. These data are summarized in Table XVI.
Table XVI
Dissolved Oxygen and
in the John H.
Date
6-15
6-30
7-8
7-12
7-18
7-27
8-4
8-12
8-16
8-22
8-31
9-8
9-16
9-20
9-26
10-4
10-12
Day
Wed
Thu
Fri
Tue
Mon
Wed
Thu
Fri
Tue
Mon
Wed
Thu
Fri
Tue
Mon
Tue
Wed
BOD Observations
Kerr Dam Tailrace,
Maximum Dissolved Oxygen
Discharge mg/1
cfs Max. Avg. Min.
22,200
22,200
16,500
23,500
26,100
12,300
26,700
17,800
16,100
22,300
21,700
20,500
22,900
17,400
17,100
19,000
14,500
5-3
4.2
3.8
2.9
2.4
3.7
3.6
3.4
2.5
3-5
3.8
3.1
5-3
5-2
4.7
6.3
6.9
4.8
3.6
2.8
2.1
1.8
2.6
2.4
1.9
1.7
2.4
2.9
2.2
4.7
4.3
3.8
5.8
6.4
4.3
2.8
2.2
1.6
1.4
1.7
1.9
1.1
1.0
1.8
2.2
1.3
4.2
2.1
3.0
5.2
5.4
I960*
Temperature
°F.
Max. Avg. Min.
66
69
67
68
70
70
73
73
73
76
76
77
77
76
73-5
74.5
71
64
67
66
67
68
69
72
71
72
74
75
76
76
76
73
74
70
63
65
64
64
67
65
68
70
69
71
73
73
74
74
71.5
72.5
68
20°C. BOD
k
5 -Day 30-Day I/Day
1.1
1.1
1.1
1.1
1.1
1.4
1.4
0.9
0.9
1.2
1.0
1.0
1.0
1.0
0.6
0.7
-
3.2
3.0
2.9
3.4
3.0
3.2
4.4
3.0
4.0
4.8
4.6
4.1
4.0
4.3
1.4
2.1
-
0.03
0.03
0.07
0.07
0.07
0.07
0.07
0.10
0.10
-
0.05
0.05
0.05
0.05
0.04
0.04
-
North Carolina State
Company.
Stream Sanitation Committee and Virginia Electric and Pover
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63
These data show that the lowest tailrace dissolved oxygen values generally
occurred early in the morning vhen only the house turbine vas in operation or
else just after peaking operation began and before drawdown of surface waters
might be expected to develop. Although the mean elevation of the house turbine
intakes is higher than that of the main turbine intakes, and the discharge is
almost negligible (hence allowing a greater time for surface aeration in the
tailrace), the dissolved oxygen content is lower than later in the day under
peaking flows. The data indicate that the D.O. discharged from Kerr Dam is
higher than indicated by the scroll case observations and that, while the tail-
race dissolved oxygen observations are subject to some variation, they may be
expected to increase gradually during a normal peaking day, and be "lowest at
night or on weekends under minimum flow conditions.
VEPCO and Corps of Engineers samples at Kerr Dam were collected during
peaking flows and have been considered to represent the dissolved oxygen content
of the mass of the water discharged. Observations by VEPCO since 195^, the
Steering Committee for Roanoke River Studies in 1957, and- the North Carolina
State Stream Sanitation Committee in 1960 show that the dissolved oxygen con-
centration in the water passing through both the scroll case and tailrace are
subject to substantial variation. The 195^ ajn^ 1957 data tend to show increased
D.O. with increased flow as was found by the Steering Committee at Roanoke Rapids
Dam, although this was not always the case. The I960 D.O. observations in the
tailrace of Kerr Dam by the Worth Carolina State Stream Sanitation Committee
showed an increase in D.O. with increased flow in about half the series of
observations.
Dissolved oxygen samples collected in the river between the Kerr Dam
and Roanoke Rapids since 195^- by VEPCO and the Corps of Engineers are summarized
in Table XVII.
Observations in 1957 with graphical estimation of missing data (such
estimates could be reasonably made for 7 days) indicated that the weighted
dissolved oxygen passing Eaton's Ferry was only 0.1 mg/1 lower than the esti-
mated D.O. at 10 a.m., the usual time of observation. For the number of
observations available, this is not a significant difference. The weighted
D.O. for these same days was 0.1 mg/1 higher than the estimated D.O. based on
graphical extension of the available Corps of Engineers and VEPCO data at
Eaton's Ferry reasonably represent the weighted mean dissolved oxygen passing
that point. Since all observations were taken during weekday flows, the
observed dissolved oxygen values would be below those obtained on minimum flow
days on weekends. However, since the volume of flow on such days is estimated
to be only 7 percent of the flow on power producing days (data from July,
August, and September 1960), the added D.O. from this source is quite small.
-------
64
These data show that under present conditions there is considerable absorption
of dissolved oxygen between Kerr Dam and Eaton's Ferry under critical dissolved
oxygen conditions.
Table XVII
Summary of Dissolved Oxygen Observations
in the Roanoke River from John H. Kerr Dam
to Clements Island, 1954 to
Dissolved Oxygen, mg/1
July August September
Max. Mean Min. Max. Mean Min. Max. Mean Min.
Kerr Scroll Case 2.6 1.3 0.1 2.2 0.7 0.0 6.4 3.3 0.0
Kerr Tailrace 3.9 2.7 1.4 3.0 2.2 1.2 7«5 4.1 1.4
(Ei. Mil 179)
U. S. Hwy. 1 Brdg. 4.9 4.5 2.0 6.5 3.4 2.4 5.9 4.6 2.7
(Ei. Mi. 173)
Virginia-Worth Carolina State Line (Ei. Mi. l6l)
Eaton's Ferry 7.5 6.2 5.1 5.7 5-0 4.6 8.4 6.6 3-6
(Ei. Mi. 152)
Clement's Island 8.6 7.3 6.5 7.4 6.7 6.1 9.3 6.9 5.7
(Gaston Site,
Ei. Mi. 146)
_
Corps of Engineers and VEPCO data.
Data since 195^ have been used to estimate the duration of mean dis-
solved oxygen levels below specified concentrations as shown in Table XVIII.
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65
Table XVIII
Duration of Mean
Dissolved Oxygen
Concentrations Below Specified Values, Days
Location
Kerr Dam
Scroll Case
(Ri. Ml* 179)
Kerr Dam
Tailrace
(Rl. Mi. 179)
State Line*
(Bi. Mi. 161)
Eaton's Ferry
Y Mean Annual
*ear Plow, ,cfs
1954 5,^2
1955 6,901
1956 4,375
1957 8,446
1958 8,768
1959 6,245
I960 9,773
1961
Mean
1954
1955
1956
1957
1958
1959
I960
1961
Mean
1954
1955
1956
1957
1958
1959
I960
1961
Mean
1954
1955
1956
1957
1958
1959
I960
1961
Mean
Mean „ . -, -,
T n ,-» 4. -,£- Dissolved
July-Oct 15
Flow, cfs 4 3
3,6to 118
8,300 99
3,770 99
4,900 121
5,470 82
5,240 114
4,670 90
5,^5 92
102
87
85
68
105
55
88
83
82
82
_
-
_
to
0
4i
46
36
33
-
-
-
0
0
0
0
13
3
89
80
74
92
72
86
73
83
81
64
55
47
85
36
62
66
72
61
_
-
-
0
0
0
0
7
1
-
-
-
0
0
0
0
0
0
Oxygen, mg/1
210
47
47
49
81
53
73
62
74
61
9
5
17
10
0
38
26
55
20
_
-
_
0
0
0
0
0
0
-
-
-
0
0
0
0
0
0
25
.29
43
64
36
51
54
57
44
0
0
0
0
0
0
0
0
0
_
-
_
0
0
0
0
0
0
-
-
-
0
0
0
0
0
0
5
15
0
3
15
10
20
0
8
0
0
0
0
0
0
0
0
0
_
-
-
0
0
0
0
0
0
-
-
-
0
0
0
0
0
0
Based on interpolation between tailrace and Eaton's Ferry observations.
-------
66
Although the curves from which the duration of low dissolved oxygen
conditions was estimated are based on single observations at biweekly inter-
vals, the samples were collected during peaking flows when the greatest
portion of the water was discharged. The results show that the Roanoke
River from Kerr Dam to as far as Eaton's Ferry is below the present North
Carolina State Stream Sanitation Committee classification standard of 4.0
mg/1 for considerable periods of time each summer. The following tabulation
indicates the number of days the tailrace D.O. during peaking flows may be
expected to be below 4.0, 3.0, 2.0, and 1.0 mg/1 in 90, 50, and 10 percent
of the years?
Number of Days the Dissolved Oxygen
Dissolved Oxygen will be Below the Indicated Value
mg/1 for the Proportion Years (Percent)
Indicated at the Head of the Column.
22 52 i2
4.0 62 80 102
3.0 40 60 86
2.0 3 18 60
1.0 None None None
Based on a similar analyses, the scroll case D.O. may be expected to be
below 4.0 mg/1 for 84 days, or more, in 90 percent of the years and for
122 days, or more, in 10 percent of the years. The data at the State line
and at Eaton's Ferry were felt to be inadequate for such analyses.
The data on the duration of critical dissolved oxygen conditions for
the scroll case and tailrace at Kerr Dam have been examined for a temperal
trend. These analyses indicate that the problems associated with low D.O.
as a result of thermal stratification may be increasing. The duration of
scroll case dissolved oxygen levels of 2.0 mg/1 and below appears to be
gradually increasing, though the duration of values below 4.0 mg/1 appears
to have remained relatively steady at about 100 days per year. The increase
in duration of tailrace dissolved oxygen levels of 4.0 mg/1 or below has
been much more pronounced. However, several more years of observation will
be required to definitely establish these trends. Although the mean annual
flow does not appear to have an influence on the duration of low D.O.'s in
scroll case or tailrace samples, an increase in the mean summer flow appears
to result in an increase in the duration of low D.O. value. A possible
reason for this influence would be the lesser drawdown of the power pool
during high flow years resulting in the thermocline being maintained at a
higher level so that less admixture of surface water is possible.
-------
67
Increases in mean summer flow resulting from upstream storage would
probably not have the adverse effect on dissolved oxygen discharged from
Kerr Dam implied by the previous analyses. Prior storage in these impoundments
would reduce the first- and second-stage BOD load presently reaching Kerr
Reservoir. It is further assumed that all future installations will include
as a part of the original construction adequate consideration of intake
structures or system operation to minimize the reduction in the dissolved
oxygen content of the water discharged. The water stored during the winter
period has a lower organic content because of the much greater dilution.
The greater storage of this water will tend to dilute the summer flows. A
possible adverse effect of upstream storage could be the development of
density interflows resulting from lower stream temperatures. These inter-
flows might reduce the amount of surface water reaching the present Kerr
turbine intakes by maintaining the hypolimnion at a higher elevation, there-
by resulting in less oxygen being added from the surface waters. The net
effects of these changes depend on several opposing forces and must be ob-
served before definite conclusions can be reached.
It should be noted that while the dissolved oxygen as measured in
the scroll case and in the tailrace at the John H. Kerr Dam was below 4.0
mg/1 for substantial periods of time, it was below this value only an average
of 3 days per year by the time it reached Eaton's Ferry and in no case was it
below 3.0 mg/1 at that point. On an average of 33 days per year over the past
5 years the estimated mean dissolved oxygen at the State line has been below
the North Carolina classification standard of 4.0 mg/1. On an average of
about one day per year it has been below 3-0 mg/1.
Estimates of the increases in dissolved oxygen required in the Kerr
Dam tailrace to meet the North Carolina classification standards indicate
that:
1. Increases in D.O. during low flows when vacuum breaker operation
could be applied will add relatively little to the mean D.O.
at the State line since the volume is small and the reaeration
of this water—at the low levels at which it flows—is already
quite high.
2. Increases required during peaking flows amount to as much as
1.0 to 1.5 mg/1 at the beginning of peaking flow on Monday and
are as much as 0.7 to 0.9 mg/1 during the maximum discharge from
10 a.m. to 2 p.m. However, during this short period, 80 to 90
percent of the daily flow occurs.
-------
68
Reaeration coefficients based on the 1957 observations by the Special
Committee on Roanoke River Studies ranged from 0.19 to 0.51 per day based
on the increase from the indicated dissolved oxygen in the tailrace during
peaking discharges to the minimum dissolved oxygen content observed at
Eaton's Ferry. For observations made on a single day estimated reaeration
coefficients ranged from 0.27 to as high as 0.92 per day. For the period
of maximum discharge a value of 0.3 per day has been used for peaking flows,
but a value of 0.6 per day is estimated for a streamflow of 1,000 cfs.
It has been noted that the dissolved oxygen values observed by VEPCO
at Eaton's Ferry approximate the weighted mean value of dissolved oxygen
values observed in connection with the Roanoke Rapids Study survey. This,
however, masks the adverse effects of periods of lower D.O. resulting from
the high instantaneous discharges during peaking flows. Both the 1957 ob-
servations and the dissolved oxygen recorder observations by the Worth
Carolina State Stream Sanitation Committee in the summer of 1961 show that
the dissolved oxygen levels are subject to wide variation. While the mean
D.O. content was estimated to be below k.O mg/1 for 13 days at Eaton's Ferry
(including weekend days within the period), minimum values observed in 1961
were as low as 2.5 mg/1 and the dissolved oxygen was below k.Q mg/1 for an
estimated 230 hours, or almost 10 days. Based on the D.O. recorder data it
is estimated that the D.O. was below 4.0 mg/1 for parts of 22 days. The
limited dissolved oxygen data available at John H. Kerr Dam for that period
make it difficult to estimate the corresponding concentrations of dissolved
oxygen in the tailrace, although consideration of the high flows associated
with the lowest dissolved oxygen observations at Eaton's Ferry indicates
that reduced reaeration below the tailrace was probably a more important
factor than unusually low dissolved oxygen in the discharge from Kerr Dam.
The VEPCO and Corps of Engineers data indicate that the dissolved
oxygen content of the water reaching Clement's Island, the head of Roanoke
Rapids Reservoir, is about 80 percent of saturation. While the recovery
at element's Island is not as great as was previously found at North Carolina
Highway hQ bridge, it is substantial and the reaeration capacity of the
natural channel of the Roanoke River above Roanoke Rapids Reservoir has
been an important factor in correcting the low dissolved oxygen levels re-
sulting from discharges from Kerr Dam.
At the upper end of Roanoke Rapids Reservoir, the variation in temper-
ature and velocity of the inflowing water results in alternate recharge of
surface and intermediate depth waters. The warmer water which reaches the
reservoir passes into the surface layers. Just as it has been warmed by its
greater relative exposure to the air and sun, it is also the most oxygenated
water. The DcO. varies over a wide range as indicated by the results at
-------
69
Eaton's Ferry and Clement's Island In 1957 and the D.O. recorder results
at Eaton's Ferry in 1961. The results at Gaston site are parallel to the
observations at Eaton's Ferry for the period that surface flow is occurring,
but diverge from it in each case when the temperature and velocity of the
flowing water decrease sufficiently that an underflow can develop. Obser-
vations at Clement's Island (river mile lU6) therefore represent surface
water from Roanoke Rapids Reservoir when density underflow is occurring.
The D. 0. measured thereafter is higher than the inflow "because of (l) its
higher original value, (2) mixing with the higher D.O. surface water of the
reservoir, (3) reaeration resulting from physical transfer, and (k) re-
oxygenation resulting from photosynthesis.
The results imply a higher D.O. at Clement's Island than should have
been expected based on the D.O. at Eaton's Ferry and the flow time involved.
The implied high reaeration rates do not seem reasonable. These conclusions
are in agreement with-the discussion of density underflow presented in
Special Report No. 1,^8 pages 33 through ko, and the relationship developed
in that report between Kerr Dam discharge factor, Roanoke Rapids Dam discharge,
and the dissolved oxygen at North Carolina Highway kQ bridge. They are not,
however, in accord with the statement in Special Report No. 1 (page 5) that
the increase in dissolved oxygen between Eaton's Ferry and Gaston site are
due to increased rate of reaeration. This overestimation of the dissolved
oxygen content of the inflow to Roanoke Rapids Reservoir would account for
a part of the reduction observed between Clementte Island and Roanoke Rapids
Dam tailrace.
Conclusions of the present review of the data are in general agree-
ment with the conclusions stated in Special Report No. 1 by the Steering
Committee for Roanoke River Studies and are summarized as follows:
"The minimum values, both D.O. and temperature, correspond to the
high flows. This is a result of (1) the more rapid transit from Kerr Dam
to Eaton's Ferry at high flows allowing a shorter time of exposure for re-
aeration, (2) the increased depth of the flowing water at high flows, and
(3) the decreased surface area per unit of volume of the water. These
factors outweigh the effect of increased turbulence at high flows which
tend to increase reaeration.
"In summary, the water traveling from Kerr Dam to Eaton's Ferry
is slightly improved in average D.O. quality and normality increased in
temperature, but with occasional cooling when unseasonably low atmospheric
temperatures occur. Low flows are reasonably well aerated, but such flows
represent a relatively small portion of the total volume of water moving
downstream."
-------
TO
The Roanoke Rapids Dam was closed on June 25, 1955- The first turbine
was placed in operation on July l8, 1955- Dissolved oxygen observations re-
ported by VEPCO and the Corps of Engineers at the Roanoke Rapids Dam tailrace
and at North Carolina Highway kQ bridge prior to July l8, 1955, were 8.0 mg/1,
or above, as a result of reaeration below Kerr Dam. However, immediately
following the initiation of power production by VEPCO, observations by the
Halifax Paper Company33 in the tailrace immediately below the dam indicated
that the dissolved oxygen content fell to as low as 3«2 mg/1. These low
values were obtained until the low dissolved oxygen water resulting from the
combination of the reduced reaeration and the relatively long period of
storage during the filling of the reservoir was exhausted by the high flows
occasioned by Hurricane Diane (August 17, 1955)• High flows prevailed from
August 17 to August 2k-; before and after this period of high flow, normal
September flows prevailed. Following Hurricane Diane the tailrace dissolved
oxygen level was almost 7*0 mg/1 and gradually fell to 5-^ rag/1 by mid-
September. Thereafter, the dissolved oxygen gradually increased as the
dissolved oxygen content of water discharged from John H. Kerr Reservoir
improved.
Dissolved oxygen levels were observed in 1956 by VEPCO and the
North Carolina State Stream Sanitation Committee. The VEPCO observations
made during the peaking flows in the tailrace and at the North Carolina
Highway kQ bridge indicated a minimum value of 4.7 mg/1. The North Carolina
observations were made during minimum flow periods of the days sampled during
late August and early September. The observations represent minimum dissolved
oxygen conditions on the basis of subsequent observations that low flows are
accompanied by low dissolved oxygen conditions. The minimum observation
was 3-2 mg/1 and the average of the 21 observations was 5«^ mg/1. Only
the one value cited was below k.Q mg/1.
The minimum dissolved oxygen observation of 3«2 mg/1 was in contra-
vention of the stream classification standards, subsequently established,
so that no waste could have been discharged to the tailrace. However, ob-
servations made by the North Carolina State Stream Sanitation Committee in-
dicate that reaeration between North Carolina Highway kQ bridge and Weldon
exceeded the deoxygenation caused by waste discharges. Thus some waste
could be added in the Roanoke Rapids-Weldon area without again lowering the
dissolved oxygen below k.O mg/1. At the observed flow of 1,330 cfs it is
estimated that a waste load in the order of 25,000 pounds of BOD per day could
have been discharged.
-------
71
Dissolved oxygen conditions were improved Toy the installation of
the submerged weir in Roanoke Rapids Reservoir "by VEPCO in early 1957-
The discussions and negotiations leading to the construction of the submerged
weir are contained in minutes of the Steering Committee for Roanoke River
Studies. Briefly, a weir was proposed for inclusion in the Gaston Project.
In the absence of experience with such an installation, the North Carolina
State Stream Sanitation Committee could not agree to accept the project.
The Roanoke Rapids weir was proposed, installed, and investigated as a pro-
totype for the Gaston Project and to improve the quality of water discharged
from Roanoke Rapids Dam itself. The study was to be the basis for deter-
mining whether a submerged weir would assure adequate water quality below
Roanoke Rapids Dam during the summer period acceptable to the North Carolina
State Stream Sanitation Committee and the Halifax Paper Company. The con-
clusions of the study and the comments of the special consultants are
summarized in the section, "Summaries of Previous Studies." A summary of
the observations made in 1953, 1956, and 1957 at North Carolina Highway 48
bridge presented in Special Report Wo. 1 is reproduced in Table XIX.
The routine VEPCO stream data collected since 1955 below Roanoke
Rapids Dam relate to peaking flows. Since adverse dissolved oxygen conditions
occur under minimum flow conditions these observations have not been exten-
sively reviewed. The results of the 1957 Survey by the Steering Committee
and VEPCO have been the primary basis for the analysis of the waste assim-
ilative capacity below Roanoke Rapids since construction of the Roanoke
Rapids Dam.
Below Roanoke Rapids
The development of reservoirs on the Roanoke River has been accompanied
by economic development of the lower Roanoke River. The growth of municipal
and industrial waste loads tributary to the stream has been an important
factor accompanying the development of the area and has been a factor in the
dissolved oxygen changes observed and in the adjustments in minimum flow
for the river below Roanoke Rapids. Since the paper industries discharge
the largest quantities of wastes in the lower Roanoke River area their wastes
are of concern in discussing the changes in dissolved oxygen observed.
Data secured by the North Carolina State Stream Sanitation Committee
in 1955 indicated that the waste loads at Halifax Paper Company had been
reduced to 50*300 pounds of BOD per day, despite a 21 percent increase in
pulp production.39 The improvements made in plant equipment and operation
-------
72
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73
also substantially reduced the toxic and slime producing characteristics
of the waste discharge.*
Additional data secured by the North Carolina State Stream Sanitation
Committee in August 1956 indicated that both the waste load and production
had increased slightly and equaled 57,^0 pounds of BOD per
During 1955 the North Carolina Pulp Company plant was expanded to a
capacity of 1,300 tons of pulp per day.oU Information supplied by the
North Carolina Division of Weyerhaeuser Company (the present owner of the
former North Carolina Pulp Company facilities) indicated that production
in 1960 amounted to 1,060 tons of pulp per day.** The North Carolina State
Stream Sanitation Committee has indicated that the plant is now discharging
less than the amount of BOD allowed under the pollution abatement plan.
Data supplied by the Halifax Paper Company indicated that the mean
waste discharge for September 1 through September 20, 1961, amounted to
4l,700 pounds of BOD per day.
The untreated waste discharge from a modern unbleached kraft mill
amounts to approximately 50 pounds of BOD per ton of paper produced. 75 New
plants being placed in operation on the West Coast have reduced waste dis-
charges per unit of production well below this figure. On the basis that
some of the waste is due to loss of pulp in paper production, the present
Halifax Paper Company waste discharge of 60 pounds of BOD per ton of pulp
is approaching the value considered reasonable for unbleached kraft mills.
At the average dissolved oxygen level observed in the tallrace of
Roanoke Rapids in 1956 after the dam was in operation but before the submerged
weir was installed, the waste assimilative capacity at a minimum flow of
1,000 cfs on weekends was approximately U0,000 pounds of BOD per day, while
^Minutes of the Steering Committee for Roanoke Rapids Studies.
**Private communication through North Carolina State Stream Sanitation
Committee.
-------
at 2,000 cfs the capacity was 80,000 pounds per day. Although the weekend
minimum flows have been eliminated "by the interim agreements between the
Horth Carolina State Stream Sanitation Committee and VEPCO the assimilative
capacity available at 2,000 cfs was below that which was available at
comparable flows in 1953 following completion of the John H. Kerr Dam«
Based on the average dissolved oxygen content of the tailrace after
installation of the submerged weir, as found in the Steering Committee-VEPCO
Survey,48 the assimilative capacity at minimum weekend flows of 1,000 cfs
would have been 47,000 pounds of BOD per day. Under minimum weekday flows
the assimilative capacity was increased to 93>000 pounds per day. Thus,
the weir resulted in a 16-percent increase in minimum assimilative capacity.
The capacity indicated in the previous paragraph for 2,000 cfs flows
is higher than the critical instantaneous capacity which could occur under
present operating practices. Whenever flow is below 2,500 cfs and the
dissolved oxygen level is below 5-0 mg/1 vacuum breaker operation is in-
stituted to increase the dissolved oxygen level one (l) mg/1 or more, The
lowest assimilative capacity thus prevails when flow is just 2,500 cfs and
the dissolved oxygen is at the classification value, or flow is reduced to
2,000 cfs while the dissolved oxygen is just 5-0 mg/1. (The Tn1.n3.mum weekend
flows are not considered.) The lesser of the assimilative values for the
two above cases would be approximately 65,000 pounds of BOD per day.
The waste assimilative capacity of the Roanoke River below Roanoke
Rapids was presented in Table 20 of Special Report No. 1 for selected times
when the discharge rate exceeded 2,500 cfs and the observed dissolved oxygen
level was below 5.0 mg/1. In only 3 of 26 observations cited was the
assimilative capacity after installation of the submerged weir less than
the minimum value of 109,000 pounds of BOD per day observed prior to con-
struction of Roanoke Rapids Dam.
Data obtained from VEPCO indicate that in 1961 the dissolved oxygen
discharged from Roanoke Rapids Reservoir tailrace was below 4.0 mg/1 for
a total of only about 15 hours. As a result of these low initial D.O, and
associated waste discharges, the dissolved oxygen at Scotland Neck fell
below 4.0 to a minimum of 3«8 rag/1 for only 6 hours. The minimum assimilative
capacity below Roanoke Rapids under conditions of the submerged weir and
vacuum breaker operation is less than was available under post-Kerr Dam
conditions but more than would have been available at the design flow under
natural conditions. Further, minimum daily values substantially below the
design flow, though of very infrequent occurrence, have been eliminated.
-------
The adjustments of minimum weekday and weekend flows presently in
effect nave been described in the section on water resources development.
They are essentially the same as will be in effect after the Gaston Project
goes into operation. Together with the mixing resulting from the wide
variations in flow and translatory wave action and present operating practice
as regards vacuum breaker operation, the minimum assimilative capacity be-
low Roanoke Rapids will be assured to be at least 76,000 pounds per day.
Peaking flows following minimum weekday flows provide more than enough
capacity to assure the daily average of 109,000 pounds of BOD per day which
has been used as the basis for the pollution abatement plan established by
the North Carolina Stream Sanitation Committee.
Summary
Thermal stratification restricted mixing of water between the various
levels of Kerr Reservoir and, together with degradation of organic materials,
resulted in complete depletion of dissolved oxygen at the bottom of John H.
Kerr Reservoir in 6 of the 8 years of observation. Discharge of water from
the lower levels of the reservoir resulted in minimum dissolved oxygen con-
centrations of 1.2 mg/1 in the tailrace during peaking flows and as low as
0.3 mg/1 during minimum flows.
Reaeration in the Roanoke River improved the D.O. considerably but
at peaking flows was not sufficient to ensure a D.O. above 4.0 mg/1 at
Eaton's Ferry, 9 miles below the Virginia-North Carolina State line, at all
times.
Immediately after installation of Roanoke Rapids Dam, the dissolved
oxygen content of peaking discharges fell to as low as 3.2 mg/1 as a result
of density underflow of incompletely reaerated peaking discharges from
John H. Kerr Dam. With installation of a submerged weir the D.O. was raised
substantially but not sufficiently at minimum flows to prevent a reduction in
waste assimilative capacity below Roanoke Rapids as compared with that avail-
able before Roanoke Rapids Dam was completed. Modification of minimum flow
schedules by negotiations between the State Stream Sanitation Committee and
VEPCO with the approval of the Federal Power Commission resulted in still
further improvement in assimilative capacity on weekends below the Roanoke
Rapids area.
The submerged weir in Roanoke Rapids Reservoir, together with the
modified minimum flow schedule and current operating practices as regards
vacuum breaker operation, assure a minimum weekend assimilative capacity
of at least 76,000 pounds of BOD per day and peaking flows, following min-
imum weekday flows, assure a daily average capacity of 109,000 pounds per day.
-------
PREDICTED POST-GASTON CONDITIONS
The initial purposes of the Steering Committee for Roanoke River
Studies were to establish the flow releases from John H. Kerr Dam necessary
to assure effective striped bass spawning and to assure reasonable dissolved
oxygen conditions during the summer season below the Roanoke Rapids area.*
With the construction of Roanoke Rapids Dam and application of the Virginia
Electric and Power Company for a Federal Power Commission license for con-
struction of Gaston Dam between John H. Kerr Dam and Roanoke Rapids Reservoir,
primary interest turned to the determination of a basis upon which the State
Stream Sanitation Committee and the State Wildlife Resources Commission could
be assured that reasonable water quality would be maintained in the lower
Roanoke River.
Above Roanoke Rapids
To correct the reduced D.O. resulting from construction of Roanoke
Rapids Dam, the Virginia Electric and Power Company proposed installation
of a submerged weir in Gaston Reservoir extending to within 30 feet of the
maximum power pool elevation.31 Consultants for VEPCO estimated that such
an installation would assure that the dissolved oxygen content of the dis-
charges from Gaston Dam would be at least 3«5 ing/l* after an initial 2-year
period which would allow for stabilization of organic material inundated by
the new reservoir, and at least h.Q mg/1 below Roanoke Rapids Dam. However,
during the first 2 years of operation the minimum D.O. might be 0.5 mg/1
lower than the above.. The expected minimum dissolved oxygen concentration
was at (or below) the value required under the proposed stream classification
standards resulting in a reduction of the assimilative capacity of the lower
river to approximately JjO>000 pounds of BOD per day at the minimum weekday
flow of 2,000 cfs. Reaeration in the reach between North Carolina Highway
h8 bridge and Weldon was expected to be sufficient to supply the immediate
demands of the waste.
The proposed installation of a submerged weir in Gaston Reservoir
was considered by the Committee, but the reduction of the dissolved oxygen
content of the discharges from Roanoke Rapids Dam to the extent predicted
was unacceptable. It was further felt that a guarantee of a minimum assim-
ilative capacity should be included in the Gaston Project license or that
the effectiveness of the submerged weir to accomplish the same results should
be conclusively proven. The installation of the submerged weir in Roanoke
*W. King, Fish and Water Resources Problems - Roanoke River, North Carolina.
Report of Steering" Committee, May 2t, 1955, Raleigh (June 7, 1955) •
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77
Rapids Reservoir by VEPCO was to serve as a full-scale prototype for use
in studying the "benefits of such an installation for the proposed Gaston
Reservoir, as well as to provide an immediate improvement in dissolved
oxygen concentrations below Roanoke Rapids Dam. The results of the studies
of the effectiveness of the submerged weir in Roanoke Rapids Reservoir
were presented in Special Report No. 1, Roanoke River Studies.^ The
report presumes that the quality of water discharged from Kerr Reservoir
would remain the same as had been observed in 1957 (after the initial
stabilization period), and presents estimates of the dissolved oxygen
levels to be expected in the Gaston Project discharge.
The presentation in Special Report No. 1 of the effectiveness of
the submerged weir in Roanoke Rapids Reservoir to act as a high-level in-
take was prepared largely by Dr. D. W. Pritchard, director of the Chesapeake
Bay Institute of the Johns Hopkins University, Baltimore, Maryland.50,51
Since the effects of reaeration and photosynthesis extend over a relatively
long period as the water passes through Gaston and Roanoke Rapids Reservoirs,
average conditions under moderately high flows were considered in estimating
the dissolved oxygen conditions. The estimates made in the report for mean
daily flows of 5,000 cfs for July and August and 6,000 cfs for September
were felt to provide "conservatively low estimates of the dissolved oxygen
concentrations discharged from Gaston and subsequently from Roanoke Rapids."
Most years will have lower flows providing longer exposure to the forces
that supply oxygen to the surface waters which will be discharged from
Gaston Dam. "On the infrequent years of higher flows, downstream assimila-
tive capacity will be kept high as a result of the high dilution afforded
by such high flows." However, even though total assimilative capacity would
be increased, the capacity under minimum flow conditions could be reduced.
It was concluded^" that the water discharged from Gaston Dam with a submerged
weir located 15 feet below the full power-pool elevation, would have a
dissolved oxygen content of 7-5 ing/1 if the water passed through the epilim-
nion of Gaston Reservoir and 6.k mg/1 if the water passed first into the
hypolimnion. The minimum dissolved oxygen content of Roanoke Rapids Dam
discharges should be at least as high as the 6.U mg/1 predicted for Gaston
(in the conclusions this was rounded to "at least 6 ppm").
Since the water quality above Roanoke Rapids waste sources has such
an important bearing on the assimilative capacity of the lower Roanoke River
and since Special Report No. 1 was rather long and involved, the Steering
Committee for Roanoke River Studies asked for comments from three consultants
acquainted with reservoir quality problems. Comments on the estimates of the
quality of water to be discharged from the Gaston and Roanoke Rapids Reservoirs
were prepared by F. W. Kittrell of the U. S. Public Health Service,5^
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T8
M. A. Churchill of the Tennessee Valley Authority,52 an^ t ^ Riddick,
consulting engineer and chemist, .New York City.53 Their comments were
condensed and presented together with a short description of the Roanoke
River problems and the recommendations of the Committee in a summary report.5°
The project description, summaries of the comments of the consultants, and
Committee recommendations are presented in the section, "Summaries of
Previous Studies."
Each of the three consultants reviewing Special Report No. 1 caution-
ed that there might be unusual conditions which could result in occasional
low D.O.Ts. The considered opinions of the reviewers were that the submerged
weirs installed or proposed should generally result in the "discharge of
water having a minimum dissolved oxygen concentration in the range of 5 to
6 parts per million" (Churchill),5^ should "not make conditions worse than
they presently are and, in fact, holds promise of improvement in the present
situation most of the time" (Kittrell),5^ and "any prediction of this type
... is extremely difficult and speculative" (Riddick).53
On the basis of the predictions of water quality from Roanoke Rapids
Dam, VEPCO accepted license provisions providing for the assurance of
sufficient dissolved oxygen in Roanoke Rapids Dam discharges to provide a
daily assimilative capacity of 109,000 pounds of BOD per day as required
by the State Stream Sanitation Committee and the Wildlife Resources Commis-
sion.
Since it is the initial source of low D.O. water there has been
continual interest in the improvement of the dissolved oxygen content of
discharges from John H. Kerr Dam as a means of improving conditions below
Roanoke Rapids Dam. Each of the three consultants reviewing Special Report
No. 1 expressed the opinion that improvement in the dissolved oxygen content
of water discharged from Kerr Dam should be given serious consideration.
The disparity of opinion on the effectiveness of the Gaston and Roanoke
Rapids weirs indicates that all difficulties with occasional low D.O. below
Roanoke Rapids probably will not be eliminated. Correction of low D.O.'s
below John H. Kerr Dam may help minimize occurrences of low D.O. still
further.
Factors affecting the dissolved oxygen content of discharges from
Roanoke Rapids Dam following installation of the submerged weir in Roanoke
Rapids Reservoir were discussed in Special Report No. l.1^ For the summer
period the D.O. was found to increase with increasing discharges from.
Roanoke Rapids Dam, but to decrease with increasing discharges from Kerr
Dam. However, the dissolved oxygen content of the discharges from Kerr Dam
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79
was not considered as a variable. Since increased D.O. in the discharges
from Kerr Dam would decrease the addition of oxygen "by reaeration, the
net effect would "be less than the increase observed in the Kerr Dam tailrace.
Based on the VEPCO and Corps of Engineers observations since completion
of Roanoke Rapids submerged weir, it is estimated that an increase of 1.0
mg/1 in minimum D.O. at Kerr Dam results in an increase of approximately
0.2 mg/1 in the peaking flows of Roanoke Rapids Dam. However, density
underflow in Roanoke Rapids Reservoir still results in low dissolved oxygen
content during minimum flow periods requiring that VEPCO institute measures
for meeting the license requirements. It is estimated that improvement
of the dissolved oxygen content of peaking flows to a minimum of ^.0 mg/1
at Kerr Dam will result in an average improvement in the D.O. of Roanoke
Rapids Dam discharges during peaking flows of 0.1, O.U, and 0.3 mg/1
in the months of July, August, and September, respectively. A corresponding
increase during minimum flows seems reasonable but has not been demonstrated.
With completion of Gaston Dam conditions affecting dissolved oxygen changes
between Kerr Dam and Roanoke Rapids will be completely altered. It is ex-
pected that the submerged weir in Gaston Reservoir will improve the dissolved
oxygen concentration of the water entering Roanoke Rapids Reservoir and will
alter the flow through pattern in Roanoke Rapids Reservoir. Under these con-
ditions improvement in the dissolved oxygen content of Kerr Dam discharges
is expected to have less influence on the D.O. content of Roanoke Rapids Dam
discharges than in the past. The net effect is expected to be negligible, but
should be confirmed by field observation after completion of Gaston Dam and
completion of necessary facilities to improve the dissolved oxygen conditions
below Kerr Dam.
Below Roanoke Rapids
The assimilative capacity available below Roanoke Rapids at the minimum
dissolved oxygen level of 6.0 mg/1 predicted by the Steering Committee for
Roanoke River Studies in Special Report No. 1 will be 90,000 pounds of BOD
per day at a minimum flow of 2,000 cfs. The dissolved oxygen and flow re-
quirements of the Federal Power Commission license for the combined Roanoke
Rapids-Gaston Project, License 2009, as amended, indicate that a minimum
assimilative capacity of 109,000 pounds of BOD per day will be provided at
Roanoke Rapids. This value exceeds the estimated capacity available at the
design flow applied to natural streams in North Carolina by the State Stream
Sanitation Committee, and also exceeds the capacity at minimum controlled
flows which existed in 1953 after the construction of John H. Kerr Dam
(however, reduced weekend flows have been eliminated since 1956).
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,, The Comprehensive Pollution Abatement Plan for the Roanoke River
Basin developed "by the North Carolina State Stream Sanitation Committee
provided for the allocation of vaste assimilative capacity in the Roanoke
Rapids-Weldon area of 109,000 pounds of BOD per day at a flow rate of 2,000
cfs, and allowed for the discharge of greater quantities of waste when
controlled in proportion to flow. The graph of waste assimilative capacity
for given discharges and initial dissolved oxygen levels, presented "by the
Steering Committee for Roanoke River Studies in the Summary Report covering
Special Report Wo. 1, Roanoke River Studies,56 was included as Figure 3 in
this report.
Since improvement of the dissolved oxygen content of John H. Kerr
Dam is expected to make little change in the D.O. of Roanoke Rapids discharges,
little improvement in waste assimilative capacity is expected. Considering
the variation in estimates of D.O. in Roanoke Rapids Dam discharges, the
change in assimilative capacity can "be ascertained only by field observation
and should not be estimated at this time.
Summary
Water quality conditions below John H. Kerr Dam will be drastically
altered by Gaston Reservoir. The Steering Committee for Roanoke River Studies
estimated that the minimum dissolved oxygen content of discharges from
Gaston-Roanoke Rapids Dams would be at least 6.0 mg/1 based on the present
dissolved oxygen content of discharges from John H. Kerr Dam. Considering
the size of the Gaston Reservoir and the existence of submerged weirs in
both Gaston and Roanoke Rapids Reservoirs, improvement of the D.O. in the
discharge from Kerr Dam is not ejected to have a significant effect on the
dissolved oxygen content of discharges from Roanoke Rapids Dam.
The inclusion of provisions for a minimum discharge of dissolved
oxygen as well as minimum flows in the license for the joint Roanoke Rapids
and Gaston Project should assure a minimum daily waste assimilative capacity
below Roanoke Rapids equivalent to that available on weekdays after com-
pletion of John H. Kerr Dam. It is not expected that improving the dissolved
oxygen content of discharges from John H. Kerr Dam will affect the assured
assimilative capacity of the lower Roanoke River.
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SFiCTION 7
THE NEED FOR AND VALUE OF WATER QUALITY IMPROVEMENT
Interest in water quality management aspects of water resources
development projects has increased considerably since the Public Health
Service evaluation of the John H. Kerr Project in 19^7. Water quality
control is now recognized as a Joint Federal, State, and local responsi-
bility and water resources agencies are generally adopting the policy that
water quality must be improved and maintained at as high a level as is
reasonably possible to protect the water for all legitimate uses and to
provide for future municipal and industrial growth.
The minimum flow and dissolved oxygen requirements included in
the Federal Power Commission License 2009, as amended to include the
Gaston Project, provide for sufficient waste assimilative capacity below
Roanoke Rapids Dam for the residual wastes from present and anticipated
municipal and industrial wastes after adequate treatment or other means
of controlling wastes at the source. Therefore, additional flow at Fed-
eral expense for water quality control below Roanoke Rapids is not
warranted at this time.
Minimum flows from Kerr Dam have been reduced to about 100 cfs
since completion of Roanoke Rapids Dam. However, there are no municipal
or industrial water uses between Kerr Dam and Roanoke Rapids Dam; therefore,
no increases in minimum flow releases are needed at this time. There is a
definite need, however, for improving the quality of discharges from Kerr
Dam.
At the time John H. Kerr Dam was constructed, primary consideration
was given to minimum flows necessary to assimilate municipal and industrial
wastes reaching the Roanoke River at Roanoke Rapids, North Carolina. Min-
imum flow requirements stated in Public Health Service reports were based
on the assimilation of wastes discharged at Roanoke Rapids. Requirements
established in Fish and Wildlife Service reports for maintenance of fish,
and especially for the spawning of the striped bass, were also based on
conditions in the vicinity of Roanoke Rapids. While the possibility of
the discharge of water of poor quality was considered, relatively little
knowledge was available on the degree of depletion which might be expected
in the discharge and it was further thought that reaeration in the tailrace
and over a short distance downstream would quickly return the streamflow
81
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82
to near saturation. Since that time, however, considerable information
has been accumulated, much of it on the Roanoke River, to substantiate
the detrimental effects which can result from the combination of thermal
stratification in reservoirs and low-level power intakes. Because of the
reduction in dissolved oxygen concentrations in the hypolimnion associated
with the natural phenomenon of thermal stratification, low-level discharges
from Kerr Dam have resulted in significant reductions in dissolved oxygen
concentrations in the Roanoke River below the dam. Dissolved oxygen con-
centrations of as low as 1.2 mg/1 were observed in the tailrace in routine
field observations by the Corps of Engineers and the Virginia Electric and
Power Company between 195^ and 1961. Concentrations as low as 1.0 mg/1
were observed in the tailrace in 1960 in special joint studies by the Worth
Carolina Stream Sanitation Committee and the Virginia Electric and Power
Company. One observation of 0.3 mg/1 in the tailrace was reported in the
studies conducted by the Steering Committee for Roanoke River Studies. In
the years for which data are available the dissolved oxygen concentration
was less than the minimum objective of It-.O mg/1 for an average of 33 days
per year at the North Carolina State line and 82 days per year in the tail-
race of Kerr Dam. Information on the seriousness and duration of such low
dissolved oxygen conditions below Kerr Dam and at other locations has been
a factor in the extension of concern for adequate dissolved oxygen levels
to the entire length of the river rather than only to reaches affected by
organic waste discharges alone. In the section entitled "Water Quality
Objectives," a minimum dissolved oxygen content of 4.0 mg/1 was established
as a reasonable objective in the lower Roanoke River below Kerr Dam. This
objective must be maintained to assure a good environment for fish, other
aquatic life, and wildlife.
Thermal stratification in Kerr Reservoir and low-level power in-
takes in Kerr Dam have also resulted in measurable increases in iron and
manganese concentrations in the stream below the dam. The iron and man-
ganese concentrations were further increased by installation of Roanoke
Rapids Dam, and immediately after completion of the dam (Roanoke Rapids)
it became necessary for the Roanoke Rapids Sanitary District to change the
location of their water supply intake. The intake was raised to near
the surface of Roanoke Rapids Reservoir and with this change the Sanitary
District has been able to produce satisfactory water.
Any installation which makes use of public waters should provide
facilities or conduct its operations either alone or in combination with
other water uses so that the resulting water quality below the installation
meets reasonable quality objectives. Although no addition of organic
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waste is involved in the discharge of water low in dissolved oxygen content
associated with thermal stratification and withdrawal from the lower levels
of reservoirs, John H. Kerr Dam can be considered as the equivalent of a
source of pollution from the standpoint of altering water quality in the
Roanoke River below the reservoir. A definite need therefore exists for
modification of Kerr Dam and its operations to the extent that the dissolved
oxygen in the tailrace at least meets the minimum objective of k.O mg/1.
In evaluating the improvement of the quality of discharges from
Kerr Dam it must be recognized that installation of the Dam resulted in a
measurable degradation of water quality in the Roanoke River below the dam.
While most water uses result in some quality degradation, it is important
that such degradation does not interfere with other legitimate downstream
uses. The minimum water quality objectives previously discussed are set
forth to protect the stream for best usage and to provide for future munic-
ipal and industrial growth.
Maintaining water quality at satisfactory levels is the responsibil-
ity of all water users and the cost of any necessary treatment or other
water quality control measures is considered to be part of the cost of water
use. In areas where water quality and uses dictate, municipalities and in-
dustries must treat their wastes prior to discharge to assure adequate water
quality for downstream uses. In the same sense, the cost of facilities and/
or operation expense at John H. Kerr Dam necessary to meet the quality
objective for the Roanoke River is a part of the cost of water use for power
production.
Field observations conducted by the Special Committee for Roanoke
River Studies indicated that the passage of water downstream with relative-
ly little reaeration or warming resulting from peaking operation at John H.
Kerr Dam resulted in density underflow and contributed to occasional prob-
lems even after installation of a submerged weir at Roanoke Rapids Dam.
Maintaining water quality at or above the recommended minimum dissolved
oxygen objective will reduce the possibility that downstream users will be
adversely affected in their efforts to meet water quality control obliga-
tions.
Reservoir development in the lower Roanoke River is expected to play
an important part in providing for increasing recreational demands. The
full benefits of the developments as recreational areas will not be realized;
however, unless water quality is adequate to support good populations of
fish and wildlife.
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Another important aspect of any water quality improvement at John H.
Kerr Dam is the value such improvement would have in considering if similar
corrective measures or design practices would be effective in water quality
management problems in other reservoirs. The present water quality problem
at John H. Kerr project is primarily the result of a lack of technical data
at the time of project installation and any remedial measures taken could
be of great experimental value in avoiding similar problems in future reser-
voir development. It is therefore recommended that any facility installed
at Kerr Dam for the purpose of water quality control, be subject to detailed
field observation to determine the effectiveness of the facility and that
such information be made available for possible future use in designing
and/or evaluating similar projects.
The value of water quality control accomplished by a Federal project
is often expressed in terms of the cost of providing the same improvement
by the most likely alternative means that would be utilized in the absence
of the project under consideration. At Kerr Dam,, there is no alternative
to project modification. According to a preliminary estimate by the Norfolk
District, Corps of Engineers, remedial measures needed to improve the
quality of water discharged may be as much as $1,000,000, based on the cost
of a variable level submerged weir. Other methods of improving the D,0.
content of the discharges are also under study. Such an estimate should not
be looked upon as a measure of a benefit but rather as a measure of the cost
to mitigate a damage. Accomplishment of water quality improvement would be
of widespread benefit to all downstream users in that it would restore the
quality of discharges from Kerr Dam to minimum acceptable levels.
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SECTION 8
METHODS FOR IMPROVING THE DISSOLVED OXYGEN CONTENT
OF KERR RESERVOIR DISCHARGES
Methods for improving the dissolved oxygen content of -water dis-
charged from impoundments have been discussed by H. Wagner,37, 57
F. W. Kittrell,^, 65 A< Ja Wiiey, et aJ-.J1' 91 and others.^3, °2 ^g^
suggestions have been assembled in this section of the report. This discussion
of specific methods is not intended to exclude the possibility of the develop-
ment of other methods for improving the dissolved oxygen content of Kerr
Reservoir discharges.
Several methods suggested for improving the quality of water discharged
from impoundments have received considerable attention, and have been tried
experimentally or in actual practice on small lakes or reservoir. However,
the application of these methods to reservoirs as large as the John H. Kerr
Reservoir has not been demonstrated at this time. The selection of the best
method will depend largely upon the cost of installation and operation; this
factor is not considered in the present discussion. These methods have the
single purpose of improving the dissolved oxygen quality of the reservoir
discharge. The addition of pumped storage features or thermal electric units
requiring cooling water might also accomplish the same result incidental to
their primary purpose. However, these have not been discussed herein because
their effect on water quality would be a small factor in their economic
justification.
SUBMERGED WEIR
A submerged weir is an underwater barrier used to retain the colder,
hence heavier water below the hypolimnion within the reservoir; in this
sense it acts much in the same way as a dam. It can also be considered an
extension of the power intake to a point near the surface of the water.
A submerged weir has been installed in Roanoke Rapids Reservoir and
a second is being installed in Gaston Reservoir.. Special Report No. 1 by
the Steering Committee for Roanoke River Studies^ presents substantial
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86
data on the Roanoke Rapids veir indicating that the major portion of the
flow is selected from above the weir with the proportion increasing with
higher flow rates, such as occur with peaking flows. The Roanoke River
Studies demonstrated the effectiveness of a submerged weir to raise the
level from which the water is withdrawn. The dissolved oxygen content
of the discharge would increase as the elevation of the crest of the weir
is raised nearer to the water surface. Where a long weir crest can be pro-
vided, the elevation can be raised to very near the minimum power pool
elevation if a fixed weir is installed and possibly above it if a variable
level weir similar to the one being considered by the Corps of Engineers,
Norfolk District, is installed in Kerr Reservoir. A submerged weir would
increase the temperature of the water discharged so that the tendency for
density underflow to develop in downstream reservoirs would be substantially
reduced, thus allowing a greater proportion of the discharge to pass through
the next reservoir above the thermocline. The effect of cold, high volume
and low D.O, discharges from Kerr Dam on Roanoke Rapids Reservoir was dis-
cussed in Special Report No. 1 . Density underflow of low D.O. water re-
sulting from Kerr Dam peak discharges maintained the thermocline and the
elevation of low D.O. water near the elevation of the submerged weir crest
in Roanoke Rapids Dam. During the minimum flow periods or after especially
large discharges from Kerr Dam, the low D.O, water was raised above the weir
and resulted in low D.O. discharges. While the same conditions will occur
in Gaston Reservoir, it is expected that with the higher weir crest eleva-
tion, longer storage time, and operation primarily for peaking power the
water discharged will be much less affected by density underflow. Density
underflow is not expected to be serious in Roanoke Rapids Reservoir after
Gaston Dam. goes into operation.
The withdrawal of water from the highest level possible would reduce
the iron and manganese content of the water discharged from the reservoir
during the stratification season. Even with a submerged weir, there remains
the possibility of infrequent discharges of low dissolved oxygen water dur-
ing low flows when the thermocline is located near the level of the weir
crest. Low D.O, water could also be discharged at very infrequent occasions
as a result of wind denivellation.
The installation of a fixed weir with a crest near the reservoir
surface will tend to stabilize the thermocline slightly below the weir
crest elevation. It therefore would be desirable to discharge water from
the hypolimnion to the extent possible to lower the elevation of the ther-
mocline. If some water can be discharged from the bottom of the reservoir
the tendency to develop a large volume of water devoid of dissolved oxygen
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will be minimized. The effect of extended periods of zero dissolved
oxygen water in the lower levels of the reservoir on the iron and mangan-
ese content might be quite serious, especially at the fall turnover period.
The inclusion of ports at the bottom of the adjustable submerged weir which
could allow hypolimnetic water to be discharged during periods when the
dissolved oxygen content of the mixed flow was above k,0 mg/1 would add
flexibility in handling this potentially serious problem.
A weir with provision for adjusting the depth of the crest to the
lowest possible level during periods when the dissolved oxygen content of
the discharge was above the minimum would also be effective in reducing the
thermocline to the lowest practicable level. For a reservoir of the size
impounded by Roanoke Rapids Dam, the possible effects of fall turnover would
be negligible. However, unless hypolimnetic water is discharged to the ex-
tent possible during the summer season, some difficulty with the fall turn-
over may be experienced in the discharge from Kerr Dam.
TAILRACE AERATION
Increased reaeration in the tailrace could probably be induced by
special tailrace construction to increase the turbulence at this point.
The increased turbulence would involve some head loss, and hence, some re-
duction in efficiency of power production. The short period of turbulence,
especially at peaking flows where additional dissolved oxygen is most need-
ed, makes it highly questionable whether sufficient oxygen could be added
by such a method.
The installation of air diffusion equipment in the tailrace could
be used to increase the dissolved oxygen level. Experience in the Flambeau
River below Pixley Dam in Wisconsin' indicated that appreciable oxygen
could be added to the water, but that absorption was at a rather low level
of efficiency (on the order of 6 to 8 percent of the oxygen introduced into
the water). The introduction of air required substantial energy and has
been abandoned by the Wisconsin group in its investigations.
Mechanical aerators floating in the tailrace might provide a possible
means of introducing oxygen in the tailrace. This is currently under in-
vestigation by the Chicago Sanitary District. Improvements in mechanical
aeration efficiency seem possible through the use of Kessner brush type
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equipment; however, both mechanical and diffusion aeration methods have
been found to "be relatively expensive in terms of capital and operating
costs.^l Where other methods are not practicable, mechanical aerators
may prove useful.
INTRODUCTION OF AIR TO TURBINE PENSTOCKS
Admission of air through vacuum breakers has been successfully
applied by VEPCO to increase the dissolved oxygen in discharges from
Roanoke Rapids Dam.^ Significant increases were accomplishedj however,
only through restriction of the flow rate to values of the order of 1,000
cfs per turbine, or half the normal minimum flow rate. No aeration was
possible at peaking flow rates.
Similar admission of air at Pixley Dam on the Flambeau River in
Wisconsin has been tried. The increases in D.O. repprted71>91 were not
so large as those reported in the Special Report #1,^° but much less de-
tailed data are supplied so that reaeration under less advantageous con-
ditions may have been included in the averages cited. In one turbine the
water wheels were located in such a way that a vacuum was not formed and
air was introduced under pressure. It should be possible to introduce air
in this manner at higher flow rates. In such cases it is important to
supply only as much air as is needed to accomplish the desired or possible
aeration. The supply of excessive air reduces the aeration efficiency.
Turbine aeration seems to be the most promising for introducing
oxygen by direct aeration. For discharges having low initial dissolved
oxygen, Wiley concluded that "turbine aeration appears as a method which
can be considered low in cost under most conditions." The cost of tur-
bine aeration involves relatively small capital expenditures for turbine
modification and compressors, but results in the loss of a certain per-
centage of the power production of the turbine. For low head plants,
Wiley estimated the loss to be approximately 5 percent, but for higher
head installations, the loss would be a smaller proportion of the normal
power production.
Experimental studies by the Sulfite Pulp Manufacturers League and
the Wisconsin Committee on Water Pollution indicate that 15 to 25 percent
of the oxygen introduced through vacuum breakers could be absorbed by the
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89
water passing through the turbines at low discharge rates. It is un-
fortunate that the data on the efficiency of oxygen transfer at dis-
charge rates near the rated capacity of the turbines have not been re-
ported. Turbine aeration at discharge rates near the rated capacity
would have to be considered experimental and it is possible that the
efficiencies observed at the lowest discharge rates would not be applicable.
With adequate provision of facilities for ensuring the introduction
of the air in the form of small bubbles, an efficiency of 25 to 35 percent
is felt to be more reasonable and possible. This would indicate that
approximately 100 cfm of air would be necessary per milligram per liter
of oxygen to be added per 1,000 cfs of turbine discharge. Turbine aeration
would not be effective as an addition to the use of the submerged weir since
oxygen transfer efficiency would be reduced as the dissolved oxygen concen-
tration is brought nearer saturation by the submerged weir installation.
AERATION OR MIXING IN KERR RESERVOIR
Aeration has been used in Lac de Bret, Switzerland, to prevent oxygen
depletion in the hypolimnion which results in solution of iron, thus causing
water treatment difficulties. ^ The water was pumped from the hypolimnion
at a depth of k$ feet, passed through an aeration chamber, and returned to
the same depth about 600 feet from the intake. A little less than one-fourth
of the total lake volume was pumped and, since the aerated water remained at
the same depth from which it was subsequently withdrawn by the water treat-
ment plant, it was not necessary to reaerate the entire hypolimnion.
Circulation of water from the hypolimnion has been effective in
several instances°5 in reducing stratification or significantly lowering
the thermocline so that the dissolved oxygen content of water withdrawn
was increased to acceptable levels. The largest reservoir in which this
was reported* had a total volume of only 37,500 acre-feet and a mean
annual flow of 970 cfs. Application of such a procedure to Kerr Reservoir
involves an increase in scale of over one order of magnitude. The aeration
and pumping equipment required for such large flows would be substantial.
However, equipment reported to circulate large volumes of water in reser-
voirs was recently reported in the literature.90
^Private communication from equipment manufacturer.
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90
SELECTION OF METHOD
Selection of the facilities and/or operational procedures for
corrective measures to be taken at John H. Kerr Dam depends on the
availability of equipment and on detailed estimates of the cost of
fabrication, installation and operation.
Detailed design and cost estimates of possible corrective measures
are not within the scope of this report. While no single method of water
quality improvement should be expected to be best for all conditions,
technical and operating data available on the submerged weir installed
in Roanoke Rapids Reservoir and estimates of the effect of a similar
structure in Gaston Reservoir indicate that the submerged weir being
considered for Kerr Reservoir may be expected to result in satisfactory
conditions most of the time. Further data on the cost of installation
and operation of trther methods would be needed before a final recommenda-
tion could be made.
The contribution to the understanding of quality changes in reser-
voirs possible through the study of Kerr Reservoir is a further important
aspect of water quality improvement at John H. Kerr Dam. The lack of
technical data on quality changes in reservoirs at the time the project
was designed is a major reason for the present water quality problems.
Development of effective corrective measures at Kerr Dam will therefore
aid in the solution or prevention of water quality management problems in
other reservoirs. The effectiveness of any facility installed at Kerr Dam
for the purpose of water quality control should therefore be determined
by detailed field observations. Such information should be made available
for general use in designing similar projects.
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Section 9
SUMMARIES OF PREVIOUS STUDIES
The Roanoke River has been the subject of numerous meetings, con-
ferences, and studies involving various Federal, State, and local agencies,
as veil as local industries and interested groups. Three Public Health
Service reports were made between 19^3 and 1952 in which the minimum flows
required to maintain existing water quality below Roanoke Rapids were
recommended.°> 12> 18 The 195^ report by the Public Health Service
established water quality conditions following construction of the
John H. Kerr Dam and refined the estimate of the waste assimilative
capacity below Roanoke Rapids.29 Reports prepared by VEPCO and Halifax
Paper Company discussed the effects of the proposed Gaston Dam on the water
quality at Roanoke Rapids and hence on the waste assimilative capacity.31* 32, 33
The North Carolina State Stream Sanitation Committee issued the Roanoke
River Basin Pollution Survey Report39 j.n 1956, The report presented data on
water use and conditions existing in 1953 through 1956 and presented the
proposed classifications for streams in the Roanoke River Basin in North
Carolina. On the basis of the adoption of these classifications, the
Committee issued its plan for the abatement of pollution in the basin in
1957-^
The Steering Committee for Roanoke River Studies investiaged the
effectiveness of a submerged weir installed in Roanoke Rapids Reservoir
to improve the dissolved oxygen content and projected the results to the
proposed Gaston Dam.^°> ^9> 64 Through the Committee, agreement was reached
on minimum flows and water quality below Roanoke Rapids Dam acceptable to
the North Carolina State agencies and economically feasible for VEPCO. On
the basis of this agreement, the license for Roanoke Rapids Dam has been
amended to permit the construction of Gaston Dam by VEPCO.7° The reservoir
will begin filling in the fall of 1962.
91
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92
Summaries of the major reports on the Roanoke River are presented
on the following pages.
ROANOKE RIVER, VIRGINIA AND NORTH CAROLINA1
Navigation, flood control, power development, and irrigation of the
Roanoke River and its tributaries were considered. Seventeen reservoir sites
worthy of consideration for power production, including Smith Mountain, Buggs
Island, Gaston, and Roanoke Rapids but excluding Philpott and Schoolfield,
were cited. It was concluded that a hydroelectric power potential existed
but that comprehensive multipurpose development was not economically justified
at that time.
STUDIES OF THE DRAINAGE BASINS IN VIRGINIA2
Power development possibilities on the Roanoke River in Virginia were
discussed. It was noted that power development is generally associated with
industrial development which in turn is associated with increased stream
pollution unless adequate provision for its control is provided. Forty-five
industrial waste discharges of unspecified magnitude were reported for the
Roanoke River Basin in Virginia. A survey of stream pollution conditions
was recommended. No data on stream conditions were included.
ROANOKE RIVER INVESTIGATION - FLOW RELEASES NECESSARY FOR POLLUTION
CONTROL FROM ROANOKE RAPIDS TO WELDON, NORTH CAROLINA6
Minimum flow requirements for dilution of wastes in the river channel
between a proposed Roan'oke Rapids Dam and the point at which the power dis-
charges would be returned to the main channel of the river below Weldon
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93
were estimated. The organic vaste load reaching the Roanoke Rapids from
municipalities and industries in the Roanoke Rapids-Weldon area was esti-
mated to be 15,000 pounds of 5-day, 20°C. BOD per day, or an estimated
90,000 P.E.
Data indicated substantial pollution above Roanoke Rapids, presumably
from natural causes. This substantially affected the minimum flows suggested.
Minimum flows suggested to maintain dissolved oxygen at water quality objec-
tive of 5«0 mg/1 between Roanoke Rapids and ¥eldon were:
January through April 500 cfs
May 1,000 cfs
June 2,000 cfs
July and August 2,500 cfs
September 1,500 cfs
October through December 500 cfs
Flow releases proposed were for the disposal of sewage and industrial waste
discharged at that time (19^-2) without treatment. The possibilities of a
sewer to the power plant tailrace and of treatment were discussed. Releases
were based on the observed levels of dissolved oxygen above Roanoke Rapids
and it was suggested that aeration might be necessary if the discharge from
the reservoir was low in dissolved oxygen.
ROANOKE RIVER, VIRGINIA AND NORTH CAROLINA'''
Eleven reservoirs were recommended for construction based on the
prevention of flood damage and production of hydroelectric power. A signi-
ficant portion of the flood control benefit occurred in the lower Roanoke
River valley.
Philpott and Buggs Island (John H. Kerr) projects were recommended
for initial development. These projects provided practically all of the
flood control features included in the final plan. Possible use of the
reservoirs for water supply and stream pollution abatement and as an aid in
the industrial development of the lower basin were cited as intangibles not
subject to direct monitary evaluation.
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WATER QUALITY" INVESTIGATION IN CONNECTION WITH
SUGGS ISLAND RESERVOIR12
Available information indicated that wastes equivalent to a sewered
population of over 225,000 persons were being discharged to the rivers above
Kerr Dam. Since the major portion reached the river about 170 miles above
the dam, it was concluded that the residual demand would not appreciably
affect the quality of water in the reservoir.
In discussing the quality of water to be discharged from the reservoir.
it was noted that: "Water released from the reservoir through the turbines
during the warmer months, after thermal stratification is established, may be
entirely or almost devoid of oxygen and relatively cold. However, it should
have a very low biochemical oxygen demand, and turbulent flow in the stream
below the reservoir should restore possible depressed dissolved oxygen levels
to near saturation in a short distance. The greater turbulence which would
attend release of water through the sluice gates would restore any lowered
dissolved oxygen content even more quickly. In either case, before the water
reaches Roanoke Rapids, the critical point for water use and pollution below
Buggs Island, the stream should have a normal dissolved oxygen content."
Lower BOD observed in the water reaching Roanoke Rapids in 19^6 than
was observed in 19^2 was considered more representative of the conditions
to be expected after completion of the Kerr Dam. Waste loads discharged at
Roanoke Rapids were essentially the same as in 19^-2. Based on the satis-
factory stream conditions observed at flows of approximately 2,000 cfs in
the minimum summer flows were reduced somewhat as indicated below:
January through April 500 cfs
May 1>250 cfs
June through September 15 2,000 cfs
September 15 through October 1*250 cfs
November and December 500 cfs
Allowance was made for the greater depletions occurring along the south
shore of the river because of poor lateral mixing.
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95
No comment was made on the possibility of reducing the estimated
minimum flows during a portion of the day or on weekends. However, it was
noted that "appreciable changes in the pollution load by treatment of wastes
or by changes in industrial plant practices or in plant output, may warrant
changing these figures in the future."
ROANOKE RAPIDS DEVELOPMENT (F.P.C. PROJECT NO. 2009) -
REPORT ON INVESTIGATION OF APPLICATION OF VIRGINIA
ELECTRIC AND POWER COMPANY FOR LICENSE13
!Ehe Corps of Engineers review of the proposed VEPCO license for a
Roanoke Rapids Dam indicated that the project should assure the same minimum
flows at Roanoke Rapids as had been provided by the Corps' John H. Kerr Dam
"(a) to ensure that pollution conditions remain unchanged in the stream and
(b) for the conservation of fish." Table 3 of the report listing the low
flow requirements recommended by the U.S. Public Health Service and the
Fish and Wildlife Service is reproduced on the following page.
12
The Public Health Service flow recommendations in the report cited
were modified by the reduction of the minimum flow from 2,000 cfs to 1,600 cfs
for the first 15 days of September with a compensating increase from 1,250 cfs
to 1,600 cfs for the last half of the month. The reduction in weekend flows
was based on the letter report by the Public Health Service dated December 11,
19^-5 > which suggested that instantaneous flows might be reduced as much as
50 percent, provided there was a corresponding reduction in waste loading.9
The earlier Fish and Wildlife Service daily flow recommendations were used
for the striped bass spawning period. The revised Fish and Wildlife Service's
recommendations were substantially higher but the report was based on the
earlier requirements.
ROANOKE RIVER BASIN INVESTIGATION - REPORT ON EFFECTS OF PROPOSED
HYDROELECTRIC DEVELOPMENTS ON POLLUTION PROBLEMS IN ROANOKE RIVER
BASIN - UNITED STATES PUBLIC HEALTH SERVICE18
The effect of the entire proposed Corps of Engineers development for
the Roanoke River Basin on the quality of water which would result and the
minimum flows required was reviewed. It was emphasized that: (l) further
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96
Table 3
Low Flow Requirements in Cfs
For Pollution Abatement(a)
For Conservation of Fish
J.MX/11 UL1
January
February
March
April
1-15
16-30
May
June
July
August
September
October
November
December
Weekly
500
500
500
500
1,250
2,000
2,000
2,000
1,600
1,250
500
500
Each
Weekend
500
500
500
500
600
1,000
1,000
1,000
800
600
500
500
Each
Week(b)
2,000
2,000
2,000
2,000(c)
2,000
2,000
2,000
2,000
2,000
2,000
2,000
2,000
Each
Day(b)
500
500
500
1,000
2,000(c)
2,000
1,000
1,000
1,000
800
500
500
500
Each
Day(e)
1,000
1,000
1,000
2,000(d)
2,000(d)
1,000
1,000
1,000
1,000
1,000
1,000
1,000
(a)Required to maintain minimum monthly average dissolved oxygen of 6.5 ppm
and minimum daily dissolved oxygen of 5«0 ppm, U. S. Public Health Service,
"Roanoke River Investigation," March
(b)Fish and Wildlife Service, "A Report on Fish and Wildlife Resources in
Relation to the Buggs Island Reservoir, Roanoke River Basin," May
Revised 14 February
(c)l5,000 cfs for 3 days during last week in April if such flow has not
normally occurred during latter half of month is required in addition to
amount shown.
(d)Also minimum instantaneous.
(e)Ltr. Assistant Secretary of Interior to Chairman, Federal Pover Commission
dated 2^ January 19^-9 • This letter states that the volume of controllable
releases of water shall not be permitted to increase to double, or decrease
to half, of any prevailing discharge in less than one hour. In a conference
at the Norfolk District office on 2 February 19^9, the Fish and Wildlife Ser-
vice personnel indicated this requirement applied only during striped bass
spawning period.
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97
studies should be made after the proposed impoundments were placed in
operation in order to determine the quality of outflow from these impound-
ments (page 6), (2) readjustment of minimum flow releases presently suggested
might have to be made (page 6), and (3) reaeration of the released water
might need to be considered (page 5). Information on waste loads indicated
that substantial increases had taken place in the Roanoke, Virginia, area
above the John H. Kerr Reservoir and in the Plymouth, Worth Carolina, area,
an area still subject to the effects of discharge flows from the John H. Kerr
Reservoir. A small increase was noted at Roanoke Rapids. It was noted that
no allowance had been made for further growth insofar as the waste load which
might be imposed on the stream was concerned (page 2^). Since the stream
was excessively loaded at the time it was assumed that corrective measures
would be taken by the industries and cities and that it was only necessary
to maintain the existing water quality under the then existing waste loads
not withstanding the fact that pollution abatement had been included as one
of the ancillary benefits of the reservoir. The report concluded that the
minimum flow requirements proposed by the 19^-7 report were still applicable
to the existing pollution loads at Roanoke Rapids and commented that, while
a reduction in water releases for pollution control over weekends might be
made for an industry operating on a 5-day week schedule, pulp and paper
mills such as at Roanoke Rapids customarily operate 7 days per week. Re-
ductions in minimum releases on the weekend would therefore be inadvisable.
By implication, if the paper mill were shut down, some reduction in flow
might be made. For extreme drought periods (by implication occurring less
frequently than once in 10 years) a reduction of not over 20 percent in the
above flows might be necessary (page
EFFECTS OF CONTROLLED WATER RELEASES FROM THE JOHN H. KERR RESERVOIR
ON THE STRIPED BASS FISHERY OF THE ROANOKE RIVER, NORTH CAROLINA -
FISH AND WILDLIFE SERVICE20
Provision for releases from the reservoir to abate pollution and to
meet the specialized requirements of the existing striped bass fishery was
made in the operating plan for the John H. Kerr Dam. The benefits of these
were discussed in the definite project report but not evaluated as a part
of the justification of the project.
A program to evaluate and refine the recommendations for future
water releases for the maintenance of the striped bass fishery with a
minimum power loss was set up. Described are the results of observations
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on the striped bass spawning success from April 6 to May 15, 1953, "the first
season following the closure of Kerr Dam. Bioassaysof the effects of pulp
and paper mill wastes on eggs and fry are also described. Detailed informa-
tion on temperature changes and hydrographs for the striped bass spawning
season are given for stations at Kerr Dam, Weldon, Halifax, Hamilton,
Williamston, and Jamesville. Conclusions and recommendations of this report
were:
CONCLUSIONS
29. From information obtained during the course of this study,
which has been correlated with data presented in prior reports,
the Fish and Wildlife Service concludes that:
(l) River stages and temperatures prevailing during the 1953
striped bass spawning season in Roanoke River downstream
from John H. Kerr Reservoir were favorable to the migration
of adequate numbers of breeding fish to sustain production.
The extent to which pre-season high flows resulting from
augmented discharges of 13,000 second-feet April 9, 10, and
11 contributed to this success was not determined.
(2) River stages and temperatures were favorable to egg matura-
tion and spawning.
(3) After initiation of controlled releases in the interest of
the striped bass fishery minimum river stages were prevented
from falling below 11 feet at Weldon. This stage was ade-
quate to sufficiently dilute the pollution load to ratios
favorable to the survival of striped bass eggs and fry.
(4) A river stage of about 11.0 feet at Weldon is the minimum
desired from a standpoint of satisfactory sport and commer-
cial fishing operations.
(5) Impoundment of that segment of the Roanoke River from the
proposed site of Roanoke Rapids Dam to John H. Kerr Dam for
hydroelectric power purposes, may influence water tempera-
ture at Weldon to the extent that successful reproduction
of striped bass will be jeopardized.
(6) A successful management program of the North Carolina
striped bass fishery must include the following:
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a. Measures to reduce or neutralize the more harmful
pollutants discharged into the stream in the vicinity
of Roanoke Rapids, and
b. Provisions in operational plans for proposed Gaston
and Roanoke Rapids Dam and Reservoir projects and
John H. Kerr Reservoir •which will insure river stages
and temperatures at Weldon favorable to striped bass
migration, reproduction, and fishing success.
RECOMMENDATIONS
30, The following recommendations are advanced to supplement recom-
mendations provided by the Fish and Wildlife Service in prior
reports concerning the minimum flow requirements for the striped
bass fishery.
a. Biological observations should be made each year to
determine the periods when supplemental releases would
be necessary for the preservation of the striped bass
fishery.
b. Minimum stages of 11 feet at Weldon should be provided
during the period adult striped bass are congregating
in the rapids.
c. Minimum stages of 12 feet at Weldon should be provided
during the period of actual spawning.
d. Supplemental releases should be made from the surface
of the reservoir if cold-water discharges adversely
affect the striped bass fishery.
e. Cooperation of industries and municipalities should be
solicited to reduce pollution to a point commensurate
with sound economic use of the water resources.
f. Future studies should be designed to acquire specific
information on the movements of adult striped bass and
the presence and survival of eggs and fry of this
species in various reaches of Roanoke River.
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REPORT OF STUDIES ON THE ROAWOKE RIVER BELOW JOHN H. KERR RESERVOIR,
AUGUST-SEPTEMBER, 1953 AND APRIL-MAY, 195^29
Stratification in John H. Kerr Reservoir resulted in the discharge of
•water devoid of oxygen at time. The D.O. was 40 percent of saturation, or
3.5 nig/1, 6 miles downstream and 93 percent of saturation ij-3 miles below, at
Roanoke Rapids. It was suggested that impoundment behind Roanoke Rapids Dam
might (l) result in substantial degradation of the dissolved oxygen quality
above Roanoke Rapids (2) adversely affect the quality of water used for
domestic and industrial water supplies by increasing the iron and manganese
content, and (3) produce taste and odor resulting from plankton growth.
Data collected in 195^ indicated that the industrial wastes and
domestic sewage discharged in the Roanoke Rapids-Weldon area had a population
equivalent of 96,000 pounds of 5-day, 20eC. BOD, or 575,500 p.E. This repre-
sented a substantial increase since 1952. Most of the increase and 93.7
percent of the load in the Roanoke Rapids-Weldon area was the result of pulp
and paper production by the Halifax Paper Company.
Extension of the survey area further downstream from Weldon indicated
that the critical point was in the vicinity of Scotland Neck, 28 miles below
Roanoke Rapids and below the area surveyed in earlier reports. Minimum flow
requirements based on the new waste loading conditions, an assumed dilution
water D.O. of 9k percent saturation and 5-day,20°C. BOD of 0.7^ ppm and on
the additional stream data, were higher than had been suggested in the past.
The oxygen-sag curves and tables of flows necessary to meet a dissolved oxygen
requirement of 4 mg/1 indicated a waste assimilative capacity of about 70,000
pounds of 5-day, 20°C. BOD per day at 2,000 cfs. Data collected at the mouth
of the Roanoke River were not sufficient to establish the assimilative capacity
of the river in the vicinity of Plymouth.
Toxicity tests conducted in connection with this report indicated that
the toxic components of the wastes from the pulp mills might be of more
importance than oxygen consuming components as far as their effects on fish
fry and freshly spawned eggs is concerned. Reduction of the concentration
of toxicants, especially during the spawning season, might be required if the
Roanoke'River striped bass fishery is to be adequately protected.
It was concluded that requirements for public health protection,
industrial water supply, fishing, and other uses could not be adequately met
by reasonable sewage and industrial waste treatment alone, but could be
achieved by a combination of reasonable treatment and adequate dilution.
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Good housekeeping, prevention of accidental spills or excessive loss of raw
materials in the industrial establishments combined with lagooning, and a
reasonable degree of treatment of domestic sewage should maintain a dissolved
oxygen level satisfactory for water uses at that time. A combination of
dilution water and reasonable treatment of waste should reduce pollution
effects in the Roanoke River to the extent that the water resources will
support the existing industry and aid in the expansion of industry important
to the economy of the lower Roanoke and to over-all State productivity. The
benefits of pollution abatement would not be limited to a single community,
but would accrue to several communities and the State.
Additional studies of water quality with respect to dissolved oxygen
below Roanoke Rapids appeared to be warranted following the completion of
Roanoke Rapids hydroelectric project to determine the character of its
discharges. Any significant change in dissolved oxygen at Roanoke Rapids
would require adjustment of the proposed schedule of minimum releases and
the degree of treatment of pollutional wastes now indicated in order to
maintain the desired water quality.
REPORT TO VIRGINIA ELECTRIC AND POWER COMPANY ON EFFECT OF THE SUBMERGED
WEIR UPON QUALITY OF WATER DISCHARGED FROM GASTON RESERVOIR31
The conditions leading to the development of density underflow were
discussed. Density underflow of the low D.O. water discharged from Kerr Dam
would likely proceed through Gaston Dam and Roanoke Rapids Reservoir, if both
had low-level intakes. A submerged weir at a depth of 30 feet at Gaston Dam
was proposed as a high-level intake for selecting surface water for discharge.
It was postulated that withdrawal of water over the submerged weir would
result in the discharge from Gaston Dam of the best quality water available.
Data from projects in the Tennessee Valley Authority system were used to
show the quality improvement which resulted when the downstream reservoirs
had high-level intakes. It was concluded that model studies would not be
feasible to investigate the effects of a high-level weir in Gaston as a
result of problems of scaling.
While it was concluded that the water drawn through the turbines at
Gaston Dam over a submerged weir would be the best quality water available
from the reservoir, no estimate was made of the minimum D.O. of either the
Gaston or Roanoke Rapids discharges.
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A STUDY LEADING TO ESTIMATES OF THE PROBABLE DISSOLVED OXYGEN CONTENT
OF DISCHARGE WATERS FROM ROANOKE RAPIDS TAILRACE32
Estimates were made of the minimum dissolved oxygen concentrations to
be expected in the discharge from Gaston Dam if it were constructed with a
weir 30 feet below the surface. The mean dissolved oxygen in the discharge
from Gaston Dam was esitmated as the average (smooth) value of the dissolved
oxygen observed in Kerr Reservoir at the 10-, 20-, and 30-foot depths during
the fall of 195^ and spring of 1955. On this basis, the minimum D.O. was
predicted to increase from 1.8 mg/1 in the Kerr tailrace to ^.0 mg/1 in the
Gaston tailrace. The high-level intake at Gaston Dam would result in its
discharge being relatively warm so that it would mix with the water in
Roanoke Rapids Reservoir thus preventing the development of density underflow.
On this basis and with no submerged weir in Roanoke Rapids Reservoir, it was
estimated that the minimum D.O. discharge from Roanoke Rapids Dam would be
4.5 mg/1.
However, it was pointed out that the minimum dissolved oxygen level
which would result in the first 2 years after Gaston Reservoir was filled
could be as much as 0.5 mg/1 lower than in subsequent years. Further, the
dissolved oxygen might fluctuate somewhat, depending on weather so that in
hot summers when there was little wind the D.O. could be 0.5 mg/1 lower,
while in cool, windy summers it could be 0.5 mg/1 higher.
HALIFAX PAPER COMPANY, INCORPORATED, ROANOKE RAPIDS, NORTH CAROLINA,
INVESTIGATION OF THE ROANOKE RIVER (AS RELATED TO PRESENT AND FUTURE
OPERATION OF A PULP AND PAPER MILL BY HALIFAX PAPER COMPANY, INCORPORATED
AT ROANOKE RAPIDS, NORTH CAROLINA^
This report was prepared to advise the Halifax Paper Company regarding
"(l) The anticipated effects on quality of river water at Roanoke Rapids
occasioned by the construction of the proposed Gaston Dam, and (2) the effects
of the present rates and durations of water released through Kerr and Roanoke
Rapids Dams - as they influence Halifax's present and future paper mill opera-
tions."
Based on the waste assimilative capacity estimates prepared by the
North Carolina State Stream Sanitation Committee, the condition of the river
under natural flow and as modified by John H. Kerr Reservoir were compared
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with conditions in the first 3 months of operation of Roanoke Rapids Dam.
Anticipated conditions after the installation of Gaston Dam (as then proposed
by VEPCO) were also considered. The report summarized past uses of the stream,
described the condition in 1955> and discussed probable effects of further
development. Conditions which developed were not anticipated at the time
Roanoke Rapids and Gaston Projects were initiated nor was the seriousness of
the condition known until Roanoke Rapids Dam went into operation.
It was pointed out that the Halifax Paper Company has used the Roanoke
River as a source of water supply and as a means of disposing of its industrial
wastes since 1909 and, until construction of Kerr Dam 45 miles above Roanoke
Rapids, the river off the mill had been of sufficiently good quality as to
enable the disposal of the mill wastes without evident detrimental effects to
the stream. Although poor quality water was discharged from Kerr Dam, open
streamflow restored the dissolved oxygen to 90 to 100 percent of saturation
and by implication, reduced the iron and manganese contents to acceptable
values. Output gradually increased from 50 to 350 tons of pulp per day.
Completion of Roanoke Rapids Dam approximately 2 miles upstream from
Halifax Paper Company in July 1955 reduced the reaeration above Roanoke Rapids
and inundated decomposable vegetation resulting in a reduction of the D.O. of
the Roanoke River off Roanoke Rapids to as low as 3«75 mg/1, which was below
the then proposed State Stream Sanitation Committee standards. Construction
of Gaston Dam would be expected to deplete the dissolved oxygen content of the
river at Roanoke Rapids to as low as 4.0 mg/1, which would be the minimum allowed
under stream classification. Such depletion would make the control of industrial
wastes required at Halifax Paper Company "economically and practically impossible."
While the river would have a considerable waste assimilative capacity
even with dissolved oxygen concentrations only slightly above 4.0 mg/1 because
of the continuous reaeration which occurs in the stream, it would have greater
waste assimilative capacity at higher initial dissolved oxygen concentrations.
This is of particular importance during critical periods of low flow. Further-
more, some dissolved oxygen potential in excess of the minimum should be present
to satisfy the immediate oxygen demand of wastes and to prevent the stream from
being in default immediately below the sources of pollution in the Roanoke
Rapids-Weldon area.
Estimates of minimum dissolved oxygen below Roanoke Rapids Dam during
the hot summer months following completion of Gaston Dam (3«5 mg/1 in the first
2 years and 4.0 mg/1 after the reservoir has aged) seemed reasonable but would
not allow compliance with North Carolina State Stream Sanitation Committee
objectives without requiring a prohibitive degree of waste treatment by Halifax
Paper Company.
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Production difficulties from iron and manganese seemed likely unless
provision was made at water treatment plants to handle the situation.
Conditions were made worse "by the construction of Roanoke Rapids Dam and
would be accentuated by Gaston Dam if both had low-level outlets.
The water use problem on the Roanoke River involves peaking power
production, industrial and municipal waste disposal, and recreation and
fishery interests. "The established positions of Halifax and municipalities
are of long standing, those of VEPCO are recent or proposed, and those of
the fishery interests will shortly be covered by specific law." Possible
remedial actions which could be taken by VEPCO were suggested.
Particular note was made of the unreasonableness of reduced weekend
flows since most of the industries producing waste at Roanoke Rapids operated
7 days per week.
For Halifax Paper Company to continue to operate satisfactorily
sufficient quantities of water at sufficiently high dissolved oxygen con-
centrations should be assured to assimilate its wastes at all times. Data
and arguments supporting the outline of the situation were presented and it
was concluded that construction of Gaston Dam without the guarantee of
satisfactory minimum flows and quality would result in serious impairment
of downstream public and industrial rights.
POLLUTION SURVEY REPORT NO. 4, THE ROANOKE RIVER HASINA
The General Statutes of North Carolina, Article 21, Sections 1^3-215,
as revised in 1951j require that g-i 1 the streams of the State be surveyed to
establish existing pollution and be classified as to best use, and that a
plan for the abatement of pollution be formulated and enforced. This report
was prepared for the Roanoke River Basin in North Carolina in fulfillment of
the first two objectives.
Data are presented showing the present uses of the Roanoke River,
sources of pollution entering these waters, the effect of pollution on water
quality, and the recommended classifications of the streams. The first
studies were made in August 1953 for the high temperature, low flow period.
In the spring of 195^ studies were made of stream conditions during the period
anadromous fish (striped bass) were present in the river. As a result of
changes in river conditions produced by the construction of Roanoke Rapids
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105
Dam by VEPCO and by plant changes made by Halifax Paper Company, Incorporated,
additional studies were made during both the spring and fall of 1955 and- the
summar of 195^. The report recognized that the pollution problems of the
basin were complex and indicated that every effort had been made toward
developing reasonable conclusions and recommendations pertaining to the
proposed classifications of the various waters.
The data collected during the surveys were tabulated in the report
but no additional pre-Roanoke Rapids Dam data were given. Data for the
period after the reservoir was filled was given. The resurvey of the Halifax
Paper Company waste discharge in 1955 indicated that plant changes had been
effective in reducing the waste load kk percent from 90,000 to about 5^,700
pounds per day, while pulp production had been increased by 21 percent. Waste
load data were presented in greater detail in the Report of Studies Conducted
on the Roanoke River in the Roanoke Rapids-Weldon Area by the Task Force I
of the Steering Committee for Roanoke River Studies for the period, August-
September 1956.
In the discussion of the general survey findings for the lower Roanoke
River, the following statements are of particular interest for the present
report:
Plans have been submitted to the Federal Power Commission for
the construction of hydroelectric projects that will utilize
practically all the hydroelectric power potential of the
Roanoke River. Of the existing and proposed power projects
the Kerr project is the largest. The Kerr Dam was built by
and is operated by the United States Corps of Engineers for
flood control and power generation. The Virginia Electric and
Power Company has completed the construction of a hydroelectric
project near Roanoke Rapids and has applied for a license from
the Federal Power Commission for the construction of another
dam to be known as the Gaston project. The backwaters of the
Roanoke Rapids Dam extend to the siteiof the proposed Gaston
Dam which if constructed will, in turn, create a pool extend-
ing upstream to the toe of the John H. Kerr Dam.
Even though a hydroelectric project adds no pollutants to the
water, it may from the standpoint of altering water quality
be equivalent to a source of pollution. In large lakes or
reservoirs the water near the bottom of the impoundment will
be considerably colder than the water near the surface and be
completely devoid of oxygen. If the turbine intakes draw water
from near the bottom, the water discharged through the turbines
may contain little or no dissolved oxygen.
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106
Streams in this section receive an extensive pollution load
made up of both domestic sewage and industrial waste. In
many instances these discharges are resulting in conditions
that seriously jeopardize the necessary uses which must "be
made of the receiving streams. The total sewage and waste
load tributary to the stream, expressed as population
equivalent (P.E.), is estimated to be 622,500 of which
5-97*000 is due to industrial waste discharges. The indivi-
dual sources of pollution are discussed as follows:
Roanoke Bapids Reservoir - Even though no polluting material
is discharged into the stream by Roanoke Rapids Reservoir, the
dam, with its low level turbine intake structure, is the
equivalent of a source of pollution. Water discharged through
the turbines is low in dissolved oxygen and at times high in
manganese and iron.
Halifax Paper Company - The United States Public Health Service
in cooperation with the State Stream Sanitation Committee
studied the volume and characteristics of liquid waste from
the Halifax Paper Company during August and September, 1953 •
Results from this study show that the Halifax Paper Company
discharged an average of 17«3 millions of gallons of untreated
industrial waste daily into the Roanoke River. The plant study
also shows that during the period of study the waste contained
90,000 pounds of 5-day 20°C BOD, or the equivalent of domestic
sewage from a population of approximately 5l«3,000 persons.
These wastes, not only contain materials that are high in
oxygen demand, but they also contain materials that are toxic
to fish life when present in sufficient concentrations. As
yet these substances have not all been identified, nor has
lethal concentrations, as they affect striped bass, been
determined. These wastes seriously jeopardize the necessary
downstream uses.
During early 1955 certain changes were made at the mill. A
second study was made to determine volume and characteristics
of the waste. Results of this study showed that the waste
load had been reduced by W$ while pulp production had in-
creased by 21$. This reduction in pollution load has not
appreciably improved river conditions, due to the reduction
of dissolved oxygen by upstream impoundments.
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North Carolina Pulp Company^ Plymouth - This plant discharges
an estimated volume of 40 MGD of untreated industrial vaste
into Welsh Creek and the Roanoke River. This waste contributes
a five-day 20°C BOD load of ^5,800 pounds, or a population
equivalent of approximately 231,000. These wastes, highly
colored as well as high in oxygen consuming material, almost
completely delete the dissolved oxygen in the stream during
periods of hot- - dry weather. Not only are the wastes high
in oxygen consuming material, but they contain substances
that are toxic to fish life when present in sufficient
concentrations. As yet these substances have not all been
identified, nor have lethal concentrations been determined.
The report indicated that the area has excellent possibilities for
industrial development and that such development will increase the need
for suitable sources of water supply for domestic and industrial use.
The data presented in this report have been used by the North
Carolina State Stream Sanitation Committee to establish the treatment or
Vaste reduction necessary to meet the pollution abatement plan. The
assimilative capacity of the river was not given.
The recommended classification given the Roanoke River from the
Worth Carolina-Virginia State line to Roanoke Rapids Dam was "A-II," based
on water supply use at Roanoke Rapids. The recommended classification for
the reach below Roanoke Rapids Dam was "C," based on the fishery industry
dependent on the lower river. Both of these classifications allow a
minimum D.O. of 4.0 mg/1.
The conclusions included in the report are quoted in part:
1. The waters of the basin are not presently used to their utmost.
There is an adequate quantity of water to sustain additional
industrial expansion, population growth, recreational development
and other legitimate uses provided a comprehensive water pollu-
tion control program is carried out.
2. Both population and industrial development are increasing in
the basin. These trends are toward greater water use. To
adequately protect the water resources of the basin for future
use, steps must be taken to reduce existing pollution and to insure
that future polluters provide effective waste treatment.
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3« Industry has not kept pace with municipalities in the abatement
of pollution. Of the wastes being discharged to the streams
without any treatment, there are 11 points discharging domestic
sewage with a population equivalent of 48,480 while there are
21 points discharging industrial wastes without treatment with
a P.E. of 703,800.
if. Unsatisfactory operation and lack of proper maintenance have
reduced the efficiency of many existing waste treatment plants.
ko
WATER RESOURCES OF WORTH CAROLINA, ROANOKE RIVER BASIN
Municipal, industrial, agricultural, recreational, and electrical
power uses of the Roanoke River Basin in North Carolina were tabulated and
discussed. Data on surface water flows and quality and availability of
ground water were summarized. Sources of pollution in the basin together
with data on the treatment provided, the stream to which it is discharged,
and the significance of the discharge were tabulated.
The water pollution problems of the lower Roanoke River Basin were
reviewed, The most important items considered at each of the various meetings
and conferences on the lower Roanoke River held between April 1, 195^> and.
November 28, 1956, were reviewed. The metings were called in order to
establish future programs for controlling river flows, primarily for the
striped bass spawning season but also for the summer season. Through these
meetings the Steering Committee for Roanoke River Studies was organized.
The activities at the early meetings were outlined.
lj.5
ASSIMILATION OF BOD IN NATURAL WATERS J
The policy of the North Carolina State Stream Sanitation Committee
toward the allocation of the assimilative capacity of a major stream among
several municipalities and industries contributing waste was described by
means of a hypothetical, but typical, situation.
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North Carolina policy recognizes that surface waters must serve many
legitimate and necessary pruposes, some of which conflict with each other.
The disposal of wastes depends on the ability of streams to dilute and
assimilate waste materials while maintaining water quality acceptable for
other beneficial uses. North Carolina first determined how much waste was
being discharged to the stream. The cooperation of the municipalities and
industries was usually secured in the installation of flow measuring devices
and the collection of samples. An intensive study of the effects of the wastes
on the dissolved oxygen content of the stream was then conducted. Sufficient
streamflow, dissolved oxygen, temperature, long-term BOD, and waste load data
were collected.to yield statistically reliable results.
Based on the quality of water necessary for the highest stream usages
to be protected, stream standards were established. From the existing loads
and their effect on the stream, the permissible load at the critical design
flow and temperature was estimated. Considering the type of stream, present
uses, plans of existing industries for expansion, availability of possible
sites for industrial development, and the rate of growth of municipalities
a percentage of the total assimilative capacity was set aside for future
municipal growth and industrial development.
Each municipality and existing industry was then required to reduce
its waste discharges an equal proportion, applicable to all, to meet the
allowable waste discharge under critical conditions. In any event, settle-
able solids were required to be substantially removed, toxic materials reduced
to such a level as not to be biologically harmful, and slime producing materials
essentially removed. Except for the above limitations, pollution abatement
could be accomplished by treatment, or for industry, recovery systems, process
changes, treatment in a municipal plant, or by storage and controlled dis-
charge in proportion to flow.
The waste load resulting from subsequent development of a new industry
is added to the load allowed existing industry and the percentage reduction
required to again meet the allowable load is applied, the assimilative
capacity being allocated from the reserve. As municipalities grow and
existing industries expand, additional allotments from the reserve capacity
may be made on the same basis as the original allotment.
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SPECIAL REPORT NO. 1, RQANOKE RIVER STUDIES - A REPORT OH
A STUDY OF THE EFFECTS OF A SUBMERGED WEIR IN THE ROANOKE
RAPIDS RESERVOIR UPON DOWNSTREAM WATER QUALITY1*®
This report vas prepared from data collected during special studies
conducted during the period July through September 1957 for the purpose of
determining the effects of a submerged weir in the Roanoke Rapids Reservoir
upon downstream water quality.
Because of the volume and type of data presented, the report was quite
lengthy and highly technical. A Summary Report was therefore prepared by
the Subcommittee for Operations. This Summary Report gives the purpose of
the studies reported, summarizes Special Report No. 1 and the consultants1
reports on it, and expresses the subcommittee's conclusions and recommenda-
tions. The portion of that report summarizing Special Report No. 1 prepared
by persons engaged in the survey activity and analysis of results is repro«
duced in the following. Some paragraphs summarize information already in
this report.
1. Physical Description - Lower Roanoke River. The Roanoke
River is an interstate stream which rises along the eastern
slope of the Appalachian Mountains in Virginia and flows
generally southeasterly to its mouth in Albemarle Sound
about 6 miles below Plymouth, North Carolina. The portion
of the river affected by the hydroelectric projects which
alter water quality and regulate flow is the 179 mile
reach between Kerr Dam in Virginia and its mouth. Over
this section, the river traverses the gently rolling
topography of the Piedmont Plateau for 30 miles, having
an average fall of about 1.5 feet per mile whereas in the
next 21 miles it crosses the fall line where the gradient
steepens to about 6 feet per mile. Below this point
(River Mile 129) it flows through the Coastal Plains and
the gradient flattens to an average fall of less than
0.2 foot per mile.
2. Flows. The Roanoke River carries more water, by far, than
any other river in North Carolina. The annual flow through
the State averages about 8,500 cubic feet per second. Since
the construction of the John H. Kerr flood control and
hydroelectric project by the Government, river flows have
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been considerably altered and with the completion of the
Roanoke Rapids Hydroelectric Project further reregulation
of flows has been effected so that the river flow pattern
is largely governed by the schedule of minimum discharges
from the dam and the demands for peak power on the
Virginia Electric and Power Company power distribution
system.
3* Water Uses. The river possesses the greatest latent possi-
bilities for further development of any river in the State,
provided flow regulation and water quality are properly
managed. It is presently used for the generation of
hydroelectricity at the Government's John H. Kerr Project
in Virginia and at the Roanoke Rapids Project of the
Virginia Electric and Power Company located just above
Roanoke Rapids, North Carolina; for municipal and industrial
water supplies at Roanoke Rapids, Weldon and Plymouth; for
agricultural purposes, including irrigation and livestock
watering; for fishing and other recreational purposes; and
for the carriage and absorption of municipal and industrial
wastes. Skiing and boating have developed rapidly on the
Roanoke Rapids Reservoir while the reach of the river from
the Weldon - Roanoke Rapids area to its mouth constitutes
the only known major spawning area for the entire Albemarle
Sound striped bass population and furnishes spawning or
nursery areas for large, commercially important, runs of
menhaden, herring, and white perch as well as some shad.
if. Classifications Assigned. All of the above uses were
considered by the North Carolina State Stream Sanitation
Committee in assigning classifications to the waters of
the Roanoke River. The Committee, recognizing the
necessity of protecting those uses requiring the highest
quality of water, assigned classification "A-II" for the
protection of public water supplies to the reach of the
river extending from the Worth Carolina - Virginia State
line to the Roanoke Rapids Sanitary District Water Supply Intake
at the Roanoke Rapids Dam and classification "C" for the
protection of fish from the Roanoke Rapids Dam to Albemarle
Sound. The portion of the river below River Mile 18 at
Jamesville was, because of its topography and other
characteristics, designated as swamp waters.
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Flood Control and Hydroelectric Power. The first project
for flood control and hydroelectric power production in
the Lower Roanoke River Valley is the John H. Kerr Reservoir
which was closed early in 1953- This is a Government
sponsored project, constructed and operated by the Corps
of Engineers, U. S. Army. Although the physical structure
is located in Virginia, the pool formed by the impoundment
extends into North Carolina. Likewise, the effects of
flood control and flow regulation with respect to quantity
and quality are felt primarily in this State.
The second project, developed by the Virginia Electric and
Power Company, was completed in 1956 and is operated pri-
marily for the production of hydroelectric power. It is
located on the river just above the Town of Roanoke Rapids,
Worth Carolina and like the Kerr Reservoir, is operated as
a peaking plant. This installation further reregulates
downstream flows and adversely affects water quality from
the standpoint of dissolved oxygen, particularly during
periods when the impounded water is thermally stratified.
In addition to the above, the Virginia Electric and Power
Company has applied to the Federal Power Commission for a
license to construct a similar hydroelectric power project
on the river approximately nine miles above the Roanoke
Rapids Dam. The proposed development, designated as the
Gaston Project, would also be a peaking plant and would
be so located as to create a pool extending from the
headwaters of the Roanoke Rapids Reservoir to the tail-
race of the John H. Kerr Dam. The Gaston Project, if
licensed, will utilize the entire potential of the Lower
Roanoke River for hydroelectric development and will
completely canalize the river from the Roanoke Rapids Dam
to the headwaters of the John H. Kerr Reservoir, thus
eliminating the natural stream bed over the entire distance.
Proposal Relating to Water Quality and Quantity Problems.
Since December 1953; Virginia Electric and Power Company
has worked with interested North Carolina State and Federal
Agencies and with certain affected downstream water users
in an effort to find an equitable and economically sound
solution to the problems concerning both quality and quantity
of water available downstream from its Roanoke Rapids Dam.
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Hie Company made two proposals: one, dated February 16, 1956,
for the purpose of establishing a basis upon which the river
stages required during the striped bass spawning period could
be provided through joint efforts of the Company and the
Federal Government; the other, dated May 16, 1956, for the
purpose of establishing a program for providing additional
waste assimilating capacity downstream from the Eoanoke Rapids
Dam, both before and after construction of the proposed Gaston
Project. Neither of these proposals was acceptable to the
State and Federal Agencies concerned, -.which position was
concurred in by the Governor of the State of Worth Carolina
in his letter of December 17, 1956 to the President of
Virginia Electric and Power Company.
The Steering Committee, in rejecting the May 16, 1956 pro-
posal suggested a joint study to collect adequate data to
serve as a basis of a new proposal relative to the Roanoke
Rapids Reservoir and the proposed Gaston Project which
could reasonably be expected to produce downstream river
conditions under which a minimum of k.O ppm of dissolved
oxygen would be maintained at the critical sag point and,
in addition, a minimum waste assimilating capacity of
109,000 pounds of 5-Day 20°C: B.O.D. per day above that
necessary to sustain the required 4.0 ppm dissolved oxygen.
On March 27, 1957> the Virginia Electric and Power Company
withdrew earlier proposals and indicated the Company's
willingness to proceed with the following major under-
takings :
(a) The installation of a submerged weir at the Roanoke
Rapids Project, having a uniform weir crest at
elevation 107 thereby forming a curtain wall extend-
ing within 25 feet of the normal pool surface at
elevation 132. It was proposed that this weir would
promote better downstream oxygen content, both before
and after Gaston, and would also serve as a full scale
prototype for use in studying the benefits of a similar
installation in the proposed Gaston Project upon down-
stream water quality.
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(b) The Company's participation in a joint study during
the 1957 critical summer-fall season to evaluate the
the effects of a weir of this nature, and use of
these data to predict the performance of Gaston with
a similar weir. Following a joint meeting of the
State agencies and the Virginia Electric and Power
Company, held in Roanoke Rapids on May 31> 1957* a
mutually agreeable study program, within the frame-
work of the available manpower and equipment, was
adopted. The Company initiated construction of the
submerged weir about May 1, 1957> and completed it
on July 10, 1957- Upon completion of the weir, water
quality studies were begun and carried on through
September 13, 1957* The nature of these studies
together with the study findings, etc., are presented
in Special Report Wo. 1, Roanoke River Studies pre-
pared by an ad hoc Report Committee appointed by the
Chairman of the Subcommittee for Operations. This
report was presented to the Subcommittee for Operations
on February 2k, 1958, as a draft representing the
majority viewpoint of the Report Committee
7« Summary of Conclusions Presented in Special Report No. 1
From the vast amount of data and the many calculations con-
tained in the Report, the following salient conclusions were
presented:
(a) The submerged weir in Roanoke Rapids Reservoir was
hydraulically effective in selecting, for discharge
from the reservoir, water primarily from the layers
above the crest of the weir.
(b) Only a small percentage of the flow originated at
depths below 35 feet.
(c) At discharges of 2,000, 6,000, and 12,000 cfs, 7^.6$,
84.9$, and 83.6$ of the flow originated above the crest
of the weir, respectively.
(d) The layer, from which the maximum contribution to the
flow originated, was centered at 10, 15, and 20 feet
with flows of 12,000 cfs, 6,000 cfs, and 2,000 cfs,
respectively.
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(e) There was no significant change in the percent contri-
bution of the layers below the weir crest with change
in discharge rate, but there was a marked increase
in the percent contribution for the upper 10 feet with
increasing flow.
(f) A large discharge of cold, more dense water from Kerr
Reservoir upon flowing into the lower Roanoke Rapids
Reservoir can displace upwards into the surface layers
of the latter reservoir, above the weir crest, older,
somewhat degraded water from below the weir crest,
thus making this low-oxygen water available for dis-
charge across the weir. "By this process of vertical
displacement, this degraded water becomes centered in
the 20 to 25 foot layer which is preferentially selected
for discharge at low flows. At high flows from the
Roanoke Rapids Reservoir, sufficient surface-layer water
is incorporated in the discharge so that the effect of
the degraded water is largely cancelled.
(g) As a result of the process described above, the dissolved
oxygen content of the discharge from the Roanoke Rapids
Reservoir increases or decreases as indicated in the
conclusions contained in Special Report No. 1.
(h) At low total turbine discharges, the process of split-
ting the flow between two turbines, thus taking advan-
tage of maximum addition of oxygen by vacuum-breaker
operation but at a loss of power production, can effec-
tively eliminate the problem of low dissolved oxygen
at mininium flows.
(i) Because of increased dilution at higher flows and since
the incorporation of increased amounts of surface layer
water in the discharge drawn across the weir at high
flows largely cancels the effect of the degraded water
displaced upward by recent Kerr releases, no serious
problem regarding pollution abatement downstream from
Roanoke Rapids Reservoir exists at high discharge rates.
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( j) From the standpoint of hydraulic performance the weir
at Roanoke Rapids serves as a model for the proposed
weir in the proposed Gaston Project.
(k) Because of greater storage volume and greater surface
area of the Gaston Project, appropriate adjustments
must be used when applying, to the proposed Gaston
Project, the results of Roanoke Rapids Reservoir
studies of water-mass displacement, degree of strati-
fication, depth of the mixed layer, and effectiveness
of photosynthetic oxygen production and atmospheric
aeration.
(l) Significant quantities of degraded water will not likely
be rapidly lifted above the weir crest in the proposed
Gaston Project by large inflows from Kerr Reservoir as
is the case in the Roanoke Rapids Reservoir. Instead,
intermediate depth waters will be slowly lifted into
the surface layer where photosynthetic oxygen production
and atmospheric aeration are effective.
(m) The average time that the water passing through the
proposed Gaston Project would be retained in the
euphotic zone (l8 to 2k days) would be sufficiently
long to provide for significant additions of oxygen
through photosynthetic production. During any periods
of reduced yield by photosynthetic processes, atmos-
pheric aeration would contribute significant quantities
of oxygen to the upper layers of the proposed Gaston
Project.
(n) Because of the low temperature of the oxygen-deficient
waters that would be discharged from Kerr Reservoir
into the proposed Gaston Project and the consequent
likely location of the thermocline closer to the
surface than that observed in Kerr Reservoir, the
weir in the proposed Gaston Project should have a
crest 15 feet below full power-pool level rather
than the 25 feet as now constructed in the Roanoke
Rapids Reservoir.
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(o) Since the proposed Gaston Project would function for
peaking power production only, the flow pattern associated
with its weir would be that observed in Roanoke Rapids
Reservoir for high discharge, as modified for a shallower
depth of the weir crest. Thus, the waters drawn across
the proposed weir -in the proposed Gaston Project would
originate primarily in the upper 10 feet thereof.
(p) It is calculated that the dissolved oxygen in the waters
that would be discharged from the proposed Gaston Project
during the critical summer period, would be at least
6 ppm and that the temperature of this discharge would
approximate 78°F.
(q.) The dissolved oxygen content in the waters released from
Roanoke Rapids Reservoir would be at least 6 ppm and, in
most cases, even higher.
(r) Catastrophic turnover would not occur either in the pro-
posed Gaston Project or the Roanoke Rapids Reservoir.
The deep pools of cold water retained behind the weirs
would provide sufficient stability so that the fall over-
turns would proceed in a step-by-step manner, with the
thermocline slowly increasing in depth as surface cooling
continues.
A SUMMARY OF THE REPORT OF THE ROANOKE RIVER INVESTIGATION,
SUMMER, 1957 - PREPARED BY C. H. HULL -.BASED"ON DISCUSSION BY
DR. D. W. PRITCHARDPl
This summary was presented at the meeting of the Steering Committee,
Roanoke River Studies, March 27, 1958, as a simplified summary of Special
Report No. 1.
Natural surface streams in the absence of contamination absorb oxygen
from the atmosphere until near saturation. If wastes were added to the stream,
dissolved oxygen is removed at an increased rate and, if it is removed faster
than it can be replaced, it may be reduced to levels harmful to fish and other
aquatic life. This is particularly true in summer periods when, at the in-
creased temperature, the saturation value is lowered. If not overloaded with
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natural or manmade pollution, a shallow, swift, and turbulent stream absorbs
oxygen from the air fast enough to replace that absorbed by pollution.
When a stream is impounded by a high dam, a deep lake is formed in
which the water moves much more slowly, and the surface area of a given
volume of water is much smaller than in the natural stream, resulting in
reduced ability of the water to absorb oxygen from the air. In the upper
part of the reservoir, this is partially balanced by the greatly increased
time of exposure to the atmosphere. However, during the summer season the
sun warms the surface layers so that they are lighter than the deeper layers
of water resulting in thermal stratification. The deeper layers are thus
cut off from circulation with the surface so that oxygen is not carried to
these waters as it is used in the process of decay of natural organic matter
and pollution. This results in lower dissolved oxygen in the deep waters
which lasts until colder weather in the fall cools the surface waters,
making them heavier. When the density reaches that of the deep water, the
entire reservoir mixes again so that the oxygen content of the bottom waters
is restored through mixing with the surface water and exchange at the water
surface.
When hydreoelctric power plants are constructed so that the inlets
to the turbines are located deep in the reservoir, it can be observed that
the water discharged is selected exclusively from the layers at the intake
depth. During the period of summer stratification when this water is low
in dissolved oxygen, a problem results when the water is passed on downstream.
If plant intakes are at relatively high levels in the dam, they select water
from their own level, thereby passing on downstream surface water of relatively
high oxygen content.
Data on year-round oxygen concentration of water discharged from
reservoirs in the Tennessee Valley Authority were reviewed. During the
critical summer period, dams with the deepest intakes discharged water of
very low oxygen content, dams with intermediate-level intakes discharged
water of higher oxygen content, and dams with high-level intakes discharged
water of still .higher oxygen content. "From these observations, it was
reasoned that if in some way the effect of a high-level intake could be ob-
tained in the Gaston Project, the anticipated condition of low oxygen in the
water discharged downstream would be remedied."
A submerged weir was proposed for construction around the Gaston
turbine intakes as a solution to the problem of low D.O. discharge from low-
level intakes. The submerged weir would form an underwater baffle to obstruct
passage of deep water into the turbines so that water would be selected for
discharge from levels above the crest of the weir in the same manner as ob-
served for high-level intakes.
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Since the concept of a submerged weir was new, it was felt that the
ability of such a device to perform as a high-level intake should be verified.
Model studies were rejected because of the difficulty of scaling certain
controlling hydraulic features and the impossibility of including the many
factors found in nature. Other remedies for low oxygen content in reservoir
discharges were also studied including artificial aeration of water immedi-
ately downstream from the dam and spillage of water over the top of the dam.
These were alI rejected in favor of the suberged weir method. In order to
determine the effectiveness of the submerged weir in improving the dissolved
oxygen discharged, VEPCO constructed a full-scale submerged weir in the
existing Roanoke Rapids Reservoir in the summer of 1957.
"A comprehensive survey was planned jointly by the Steering Committee
(Roanoke River Studies) and VEPCO and carried out during the late summer
and early fall of 1957• This was one of the most intensive limnological
studies ever performed anywhere, involving more than twenty engineers,
chemists, biologists, limnologists, and samplers. Upwards of 15,000 separate
chemical and physical measurements of water quality were made. Several
thousands of man hours were consumed in carrying out the survey."
The survey resulted in the following findings and conclusions:
(l) The submerged weir in Roanoke Rapids functions effectively
at all times as a high-level intake, selecting water almost
exclusively from levels above the crest of the weir.
(2) The weir causes a significant improvement in average water
quality. However, due to the relatively small storage
capacity of Roanoke Rapids Reservoir compared to large
releases from Kerr Dam, such releases cause occasional
displacement of low-quality water from intermediate levels
upward into the layers above the level of the weir. The
water thus displaced upward then becomes available for
withdrawal over the weir. Under an unusual combination of
factors, water thus selected may at times be of undesirably
low oxygen content. Although these unfavorable conditions
represent a very small proportion of the time and of the
total water released, they are severe enough to cause a
downstream problem unless corrected. Means for correction
are available, as explained later.
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(3) The submerged weir has effectively solved the problem of
water quality at high flows below Roanoke Rapids Dam. No
other proven method of correcting the low oxygen conditions
at high flows is available. Dissolved oxygen in these flows
will meet the assigned stream classification of 4.0 ppm at
all times, and the dissolved oxygen above 4.0 ppm, coupled
with the large dilution factor of the high flows, provides
an excess of waste capacity above that needed in the Roanoke
Rapids -Weldon area. (During the survey, when the discharge
from Roanoke Rapids Dam was higher than 2500 cfs, the D.O.
at the W. C. 48 Bridge was never less than 4.0 ppm; ninety
per cent of the time, it exceeded 5«5
(4) At discharge rates of less than 2000 cfs through a single
turbine at Roanoke Rapids Dam, air is admitted to the turbine
through a device called a "vacuum breaker" in order to relieve
negative pressures in the turbine. The oxygen thus admitted
is absorbed by the water, thus raising its oxygen content
appreciably. This improvement can be increased by dividing
the low flow between two turbines instead of one. The im-
provement resulting from this procedure can be seen in the
graph, figure 6 [not included], which shows actual increases
exceeding 2.25 ppm. Although it results in significant power
loss, "split-wheel" operation can be used to eliminate the
severe low oxygen conditions, as noted above, which can be
expected occasionally until Gaston Dam is constructed. As
noted below, the Gaston Project should eliminate the cause
of these extreme low oxygen conditions, and thereby elimi-
nate the need for split -wheel operation at low flows .
(5) Eased on observations in Roanoke Rapids Reservoir, the weir
in the proposed Gaston Reservoir should be redesigned to
extend upward to within 15 feet of the surface, instead of
the 25 feet depth originally planned.
(6) The weir in Roanoke Rapids Reservoir serves as an adequate
"model" for predicting the hydraulic characteristics and
functioning of the proposed Gaston ¥eir. However, because
of its small size, Roanoke Rapids Reservoir can not be complete
in all respects as a model for the much larger Gaston Reservoir.
The increased size of Gaston will permit both greater retention
times for all flows and greater buffering of high surge flows
from Kerr Reservoir. Either of these two benefits of the in-
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creased size of Gaston Reservoir over the Roanoke Rapids
Reservoir would by itself provide a significant increase
in water quality. Neither of these effects could be
satisfactorily modeled. Other significant differences
between the two reservoirs exist, including operationg
methods. These differences must be considered in predict-
ing the effect of the Gaston Project on downstream water
quality. A most important item is that Gaston will operate
as a peaking-power plant with no releases at low rates.
Thus the conditions which combine to give low oxygen at low
flows in Roanoke Rapids will not occur in the proposed
project.
(7) Taking all factors into account, it is predicted that Gaston
Dam, if provided with a submerged weir extending to within
15 feet of the surface, will discharge water with minimum
dissolved oxygen concentrations of 6»0 ppm. (This prediction
is based on voluminous records acquired during the survey
and translated to conditions as they will exist in the
Gaston Reservoir.) The average oxygen content will be
considerably greater. This will provide higher oxygen con-
tent in the inflow to Roanoke Rapids Reservoir than the
minimum of 5-2 ppm observed under present pre-Gaston condi-
tions. Furthermore, it is estimated that dissolved oxygen
values as low as 3«0 ppm can occur in the natural river at
the Gaston Dam site prior to completion of the Gaston Dam.
(8) Gaston Dam, with a submerged weir, will discharge water of
about 75° temperature. This is considerably warmer than
the water now entering Roanoke Rapids Reservoir. This
change will eliminate the displacement effect in the smaller
reservoir, noted previously, which causes the occasional low
oxygen values observed. The water released from Gaston Dam
will flow through the surface layers of Roanoke Rapids
Reservoir, and as a result, should gain more oxygen on the
way.
(9) The water released from Roanoke Rapids Dam following construc-
tion of Gaston Dam with the proposed weir will have oxygen
content greater than can be expected under present conditions.
The post-Gaston minimum values are predicted to be not less
than 6.0 ppm, compared to the observed minimum of 2.7 ppm
under existing conditions for single-wheel operation.
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COMMENTS ON PROBABLE EFFECTS OF A SUBMERGED WEIR IN
GASTON RESERVOIR ON DISSOLVED OXIGEN CONCENTRATIONS
DOWNSTREAM*2
Comments on Special Report No. 1 by Mr. M. A. Churchill, chief, Stream
Pollution Control Section, Tennessee Valley Authority, were made at the request
of the Subcommittee for Operations of the Steering Committee for Roanoke River
Studies. The Subcommittee summarized his comments in the Summary Report Cover-
ing Special Report No. 1, Roanoke River Studies, as follows:
In his statement, Mr. Churchill points out that his comments are
based not only on the reported data contained in Special Report No.l,
but also on observations of a similar nature on TVA reservoirs having
both high-level and low-level power intakes. He then offered the
following comments and observations:
(a) The main points made in Special Report No. 1 concerning the
way in which water will flow through the proposed Gaston
Reservoir are correct. The proposed weir will produce essen-
tially the same hydraulic flow pattern through the pool as
power intakes located high on the face of the 'dam. The weir
should, however, be constructed at as high a level as permitted
by the lowest level to which the pool must be drawn so that
it will skim water off the surface only in order that the
released water will have the highest possible dissolved oxygen
concentration.
(b) The weir crest should not be so long as to allow velocity
distribution over it similar to those observed over the
Roanoke Rapids weir at low flows.
(c) Cold inflows from upstream storage reservoirs will move
through downstream pools at their corresponding density
level. Therefore, if the proposed Gaston Reservoir could
be kept filled to weir crest level with water colder than
that entering from Kerr, this would force the inflow to
pass through Gaston in the surface layers where it will be
oxygenated by natural reaeration and by algae-produced oxygen.
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(d) Based on reaeration coefficients for TVA reservoirs, the
dissolved oxygen concentration in the Gaston outflow should,
except possibly for a very rare event, be in the range of
five to six ppm if the weir is submerged no more than 15 feet
(below full power-pool level) and the discharge rates are not
less than 5,000 cfs.
(e) With a submerged weir in the Gaston Reservoir, it is reasonable
to assume that the released water would be warm enough to flow
through Roanoke Rapids Reservoir at a depth not greater than
20 feet; therefore, low D.O. water from below the weir crest
level in the lower pool would not be lifted above the weir
crest. This being the case, D.O. in the outflow from the
Roanoke Rapids Reservoir should not drop below about 5 to 6 ppm.
(f) If flows were cut off at both Gaston and Roanoke Rapids for a
week or more in midsummer, it is possible that subsiding dead
algae could produce a layer of low D.O. water above weir crest
level in Roanoke Rapids. Subsequent low releases from Roanoke
Rapids would then show low D.O. concentrations. The occurrence
of such a situation would appear to be a very rare event.
(g) On the off chance that low D.O. water might be discharged over
the existing weir in Roanoke Rapids Reservoir, this weir might
be effectively raised by a number of means that would still
permit the desired pool level fluctuations for pondage. Steel
plate extensions could be added to the existing fixed weir in
such manner as to stand vertically at full-pool level and rotate
to a nearly horizontal position at low pool levels. The steel
plate extensions could be float supported and hinged at the
bottom to a concrete slab laid on top of the existing stone
weir. Tight Joints would not be necessary.
(h) If releases of water of low oxygen content at Kerr Reservoir
could be converted into high-oxygen releases, most of the
problems downstream would be eliminated or greatly reduced
in magnitude. Float supported extensions of existing power
penstocks in Kerr would effectively prevent such low oxygen
releases. This would present a number of design problems
and would be expensive but the over-all downstream benefits
would also be high.
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12k
LETTER REVIEW OF SPECIAL REPORT HO. 1
ROANOKE RIVER STUDIES^
Comments on Special Report No. 1 by Mr. T. M. Riddick, consulting
engineer and chemist, and engineer who has represented Halifax Paper Company,
•were made at the request of the Subcommittee for Operations of the Steering
Committee for Roanoke River Studies. The Subcommittee summarized his comments
in the Summary Report Covering Special Report No. 1, Roanoke River Studies,
as follows:
Mr. Riddick in his review takes issue with many of the individual
statements contained in Sprical Report No. 1. He points out the
importance of the Roanoke River from the standpoint of established
uses and expresses concern over the possibility that the dissolved
oxygen in the river, after further impoundment, will be insufficient
to satisfy the waste loadings which have been assigned and provide
a suitable habitat for fish. The following is a summary of his
comments;
(a) Whereas average values as quoted in Special Report No. 1
are significant in evaluating the overall waste assimilating
capacity of the river, only minimum values have real signifi-
cance in relation to the preservation of the fishery.
(b) Aside from the potential threat of low quality water to the
fishery, the downstream water users are incumbered by the wide
variation in dissolved oxygen concentrations that have accom-
panied impoundment of the Roanoke River as well as the associa-
tion of low dissolved oxygen concentrations with minimum river
discharges.
(c) The report points out the advantages of the high level weir
in improving average conditions (compared with those which
would have prevailed had no weir been installed), but it does
not show that the weir will, under conditions of low flow and
low-dissolved oxygen concentrations, prevent intolerable con-
ditions as far as downstream waste assimilating capacities are'
concerned.
(d) The potential reaeration capacity of the proposed Gaston
Reservoir has been over-estimated by placing primary reliance
upon photosynthesis. While photosynthesis is undoubtedly
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125
helpful, the principal reaeration takes place at the water
surface and the oxygen dissolved from the atmosphere is
transferred to the lover depths of the zone of circulation
by diurnal changes in temperature at the water surface, and
by wind action.
(e) The real crux of the situation is the poor quality of water
discharged, and which will be discharged into perpetuity by
Kerr Reservoir unless corrective measures are taken. This
condition can probably be corrected by the installation of a
half-moon shaped cut-off wall of sheet steel piling in Kerr
Reservoir to permit withdrawal of top lying waters only. It
is not too .much for the State and other concerned parties to
request Kerr Dam and VEPCO authorities to spend another sum
from $250,000 to $1,000,000 for correcting a condition that
should not have been created in the first place.
(f) A floating weir consisting of structual steel members with
a 1/2 " plastic face could be constructed for the proposed
Gaston Dam so as to permit withdrawal from the top five feet
only. If this was done and Kerr Reservoir similarly corrected,
it is believed that all concerned parties would quickly and
heartily approve such a solution.
A REPORT ON A STUDY OF THE EFFECTS OP A SUBMERGED
WEIR IN THE RpANOKE RAPIDS RESERVOIR UPON DOWNSTREAM
WATER QUALITY '
Comments on Special Report Wo. 1 by Mr. F. W. Kittrell, in charge,
Stream Sanitation Studies, Robert A. Taft Sanitary Engineering Center,
U. S. Public Health Service, were made at the request of the Subcommittee
for Operations of the Steering Committee for Roanoke River Studies. The
Subcommittee summarized his comments in the Summary Report Covering Special
Report No. 1, Roanoke River Studies, as follows:
At the outset of his statement, Mr. Kittrell recognized the pioneer
nature of the investigation reported in Special Report No. 1 and
observed that almost certainly there is no precedent for the pro-
jection of such an investigation and evaluation to the prediction
of the performance of a proposed reservoir which would be similar
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126
to an existing reservoir in some respects, but dissimilar in others.
He states that in viev of this lack of precedent as veil as the
limited amount of time for the performance of the investigation
and preparation of the report, his coments were presented with
understanding of and sympathy with the complexity of the situation.
His presentation discusses the various weaknesses in material, in
logic, in assumptions made, and in conclusions reached. The con-
clusions given in his statement are summarized as follows:
(a) Both the lack of precedent for this particular type of in-
vestigation and the limited time available for its performance
made necessary the use of a number of assumptions in predict-
ing the probable dissolved oxygen content of the water that
would be discharged from the proposed Gaston Reservoir. The
soundness of judgement exercised in selection of these assump-
tions largely governs the accuracy of the predictions.
(b) Two examples are offered wherein relatively conservative
changes in basic assumptions markedly affected the resulting
predictions. Evaluation of the report is made difficult be-
cause details are omitted which are necessary to trace all
of the steps used in development of the data. It is recog-
nized that these details could not be included without the
report becoming excessively lengthy.
(c) The philosophy of the report deals with averages rather than
minimum conditions. The report would be strengthened if the
worst combination of conditions that might occur were examined
and their probable frequency of occurrence estimated.
(d) In spite of the adverse coments on certain features of the
report, it has shed light on details of reservoir mechanism
that previously were not so well understood. In the light
of this new knowledge and on the basis of considerable ex-
perience with reservoirs he expressed the opinion that
creation of Gaston Reservoir, with the proposed submerged
weir 15 feet below the surface (i.e», full power-pool level),
would not make conditions worse than they presently are, and
in fact hold promise of improvement in the present situation
most of the time. At times, however, there may be combinations
of unusual circumstances that can produce conditions, for
short periods, that will be as bad as, or possibly worse than,
those at Roanoke Rapids Dam.
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127
(e) The experimental operation of vacuum "breakers at Roanoke
Rapids Dam shoved promise as a possible expedient for dealing
•with temporary low dissolved oxygen conditions. Uses of
similar devices, possibly specially designed for the purpose
of adding D.O. to the water in the penstocks at Gaston, might
veil receive consideration.
(f) The part played by Kerr Reservoir in the overall Roanoke
River situation is important, because it is vithin the
depths of Kerr that the initial dissolved oxygen depletion
occurs. Based on technical consideration only, "it appears
reasonable to suggest that the feasibility of improvement
in the dissolved oxygen of vater discharged through Kerr Dam
should be examined." Unless such improvement can be made,
the threat of occasional low dissolved oxygen concentrations
in the Roanoke River below the Roanoke Rapids Dam vill persist
despite the best efforts of those responsible for Roanoke
Rapids Reservoir and the proposed Gaston Reservoir.
SUMMARY REPORT COVERING SPECIAL REPORT NO. 1, ROANOKE RIVER STUDIES
ENTITLED: "A REPORT AND STUDY OF THE EFFECTS OF A SUBMERGED WEIR
IN THE ROANOKE RAPIDS RESERVOIR UPON DOWNSTREAM WATER QUALITY -
FEHJARY 6, 19^85°
This report vas prepared to summarize Special Report No. 1, to
summarize the consultants' reports on it, and to express the conclusions
and recommendations of the Subcommittee for Operations, Roanoke River Studies.
The conclusions and recommendations of the Subcommittee for Operations are
reproduced belov.
A through reviev of both Special Report No. 1, Roanoke River Studies,
and the comments submitted by the Special Consultants (Churchill,
Kittrell, and Riddick) has been made by the Subcommittee for Opera-
tions. While thereis not unanimous agreement on the part of all
members of the Subcommittee concerning certain statements and con-
clusions presented in that report and comments cited above, it is
recognized that the special reservoir study and report have made
available invaluable data and a much clearer understanding of the
problems involved. The Subcommittee, in accordance vith its
assigned responsibilities, has reached certain conclusions vhich
are presented belov together vith recommendations concerning the
problems under consideration.
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128
CONCLUSIONS
1. The Lover Roanoke River, because of the large volume of water
it carries, the present uses served by it, and its latent
possibilities for further development is the dominant factor
in maintaining and improving the economy of the entire Lower
Roanoke River Valley. It is, accordingly, an inescapable
responsibility of all users of the river to establish and
carry out such measures as are necessary for the conservation
of these waters.
2. The existing flood control and hydroelectric projects (Kerr
and Roanoke Rapids Reservoirs) are both desirable and benefi-
cial; however, they have, because of low-level intakes which
discharge water of low or depleted oxygen content, seriously
reduced water quality in Roanoke River below the dams. This
has greatly reduced the capacity of the river to assimilate
existing waste discharges in the Roanoke Rapids - Weldon Area,
and during periods of critical stream flow and temperature
conditions, the dissolved oxygen in the river has been reduced
to levels dangerous to fish and wildlife. These levels have
been less than those specified by the classification assigned
to the river by the State Stream Sanitation Committee.
3. Extensive studies of the effects of impoundment and waste dis-
charges upon water quality in Roanoke River have indicated the
need for (l) improving the dissolved oxygen content of water
discharged from the Kerr and Roanoke Rapids Reservoirs and
(2) for providing treatment for the municipal and industrial
wastes discharged to the river.
k. The following means for obtaining the highest quality water
from the existing and proposed reservoirs are suggested:
(l) raising the weir at the Roanoke Rapids Dam to not more
than 15 feet below the full power-pool level; (2) installing
a weir in the proposed Gaston Project at a depth of not more
than 15 feet below full power-pool level; and (3) so modifying
the intake structures at Kerr Reservoir as to permit withdrawal
of top lying waters only; and, further (^) employing other
feasible means for increasing dissolved oxygen, including split-
wheel operation or by introducing oxygen into the discharge.
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RECOMMENDATIONS
1. It is recommended that the Steering Committee for Roanoke River
Studies endorse the proposed Gaston Project subject to agree-
ment on the part of Virginia Electric and Power Company to the
following license provisions:
(a) The reservoir shall, be constructed vith a submerged weir
having a uniform crest at an elevation no more than 15 feet
below the full power-pool level.
(b) The licensee shall take such additional measures as may be
required to discharge water of such quantity and quality
from the Eoanoke Rapids Reservoir as to maintain adequate
dissolved oxygen, above the required minimum of 4.0 ppm
at the first major oxygen pounds per day as determined by
the North Carolina State Stream Sanitation Committee in
terms of 5-&a.y 20°C B.O.D., but under no circumstances
shall the instantaneous discharges be reduced to the ex-
tent that the dissolved oxygen, above 4.0 ppm, is less than
that required to produce a waste assimilative capacity at
the rate of 70,000 pounds per day.
The attached graph entitled "Roanoke River - Graph Showing
Assimilative Capacity in River Below Weldon for Various
Discharges and D.O.'s at Critical Temperature of 25* Centi-
grade" has been prepared from available data. The assimila-
tive capacity given represents that which is provided by the
dissolved oxygen above the 4.0 ppm required for fishing
waters. The discharges required to provide a minimum daily
waste assimilative capacity for various dissolved oxygen
concentrations may be determined from the graph. It is
believed, therefore, that the attached graph will serve as
a useful tool for scheduling discharges from the Roanoke
Rapids project in relation to the dissolved oxygen content
of the water as measured at Highway 48 Bridge to produce
the minimum instantaneous and minimum daily assimilative
capacities of 70,000 and 109,000 pounds per day. The
chart maybe verified and amended as required to include
other D.O. values if needed.
Note: The graph of assimilative capacity referred to in subsection (b) is
reproduced as Figure 3 in this report.
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130
(c) The licensee shall provide special flows during the striped
bass migration and spawning season in accordance with the
recommendations of the Steering Committee for Roanoke
River Studies and/or the North Carolina Wildlife Resources
Commission and the U. S. Fish and Wildlife Service.
2. The Steering Committee should request the Corps of Engineers,
U. S. Army, to study and develop appropriate methods for im-
proving the dissolved oxygen content of the water discharged
from the John H. Kerr Reservoir.
t
REPORT OF THE STEERING COMMITTEE FOR ROANOKE RIVER STUDIES, 1955-1958
The results of the activities of the"Steering Committee for Roanoke
River Studies are consolidated in this report. The Committee, formed at the
suggestion of Congressman Herbert C. Bonner in May 1955> ^cL as its objective
the development of a comprehensive solution to the problems of the lower
Roanoke River which would protect all legitimate river uses, yet, permit the
optimum beneficial use of the limited resources of the river. Of primary
concern was the establishment of minimum flows for the Roanoke River below
Roanoke Dam which would be equitable to all legitimate river interest. The
report presents a review of past river studies and discusses in detail the
toxicity and spawning activity studies carried out in connection with the
spawning flows. The engineering studies of the effectiveness of the sub- , ...
merged weir in Roanoke Rapids Dam were not included since a separate report
had already been prepared.
The summary and conclusions of the Steering Committee are presented
as follows:
1. Minimum Flow Requirements
The primary objective of the Roanoke River Cooperative Study was to
establish a schedule of minimum flows for the Roanoke River below
below the Roanoke Rapids Dam, founded upon the facts of river per-
formance, that would be equitable to all legitimate river interests.
For convenience, considerations of minimum flows are divided between
two unrelated categories: (l) the minimum flows required to maintain
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1.31
legally assigned classification standards; and (2) the river flows
that are required to fulfill physiological requirements of the
striped bass, and other anadromous fishes, during their short annual
migrations and spawning.
a. Minimum Flow Requirements Respecting River Sanitation
The need for a final decision by the Steering Committee regarding
the minimum flows required in the Roanoke River for waste assimila-
tion and the maintenance of the classification standards assigned
by the State Stream Sanitation Committee arose early in 1959-
Following a series of negotiations over minimum flows with the
various river interests, the Virginia Electric and Power Company
filed an amended application with the Federal Power Commission
during April of 1959* The amended application requested immediate
consideration of License 2093 which would authorize the construc-
tion of the Gaston Project by the power company. Action upon the
applicant's previous request for License 2093 had been deferred
by the Federal Power Commission following receipt of a petition
for leave to intervene filed by the Halifax Paper Company under
date of June 20, 1955> an coupled with the
dissolved oxygen added to the river water by reaeration as it
moved downstream, would permit loading the Roanoke River in the
Roanoke Rapids-Weldon area with organic wastes equivalent to
109,000 pounds of 5-day, 20°C., BOD without reducing dissolved
oxygen concentrations downstream below the assigned minimum
classification standard of Ij-.O parts per million. The strength
of BOD loading that a river will absorb at any given point without
subsequent reduction of the dissolved oxygen below a fixed value
generally is known as the "assimilative capacity" of the river at
that point. The State Stream Sanitation Committee based its
Comprehensive Pollution Abatement Plan for the lower Roanoke River
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132
upon on assimilative capacity at the NC-48 Highway bridge suffi-
cient to absorb 109,000 pounds of BOD waste loading per day and
required the polluters in the Roanoke Rapids-Weldon area to
provide waste treatment facilities sufficient to restrict the
BQD river loadings at minimum flows within that limit. The
72,500-pounds-per-day difference between the 21^,000 pounds of
BOD assimilative capacity estimated available per day under the
average flows of August, 1953 (3,980 cfs), and the l4l,500 pounds
of BOD assimilative capacity present at the same average daily
river flow with the oxygen content of the river water reduced to
agree with the Virginia Electric and Power Company's post-Gaston
river-water oxygen predictions constituted the power company's
equitable share in the assimilative capacity of the river. The
Steering Committee for Roanoke River Studies reaffirmed its
position at a meeting held on November 28, 1956.
The Virginia Electric and Power Company firmly rejected the
proposed restrictions placed upon their future Roanoke River
operations by the Steering Committee. The controversy finally
resulted in the Virginia Electric and Power Company submitting
an application to the Federal Power Commission requesting
immediate consideration of the Gaston project and thus referring
the issue to the Commission for final decision.
The Steering Committee for Roanoke River Studies was called into
session on March 26, 1959> to clarify its position in respect
to the proposed Gaston project. The Steering Committee voted
to withdraw objections to the Gaston project subject to agree-
ment by the Virginia Electric and Power Company that, in the
future, the Roanoke Rapids powerhouse would discharge water
of such quantity and quality as to:
...maintain adequate dissolved oxygen, above the
required k.O ppm at the critical point of the first
major sag, to provide a minimum waste assimilative
capacity of 109,000 pounds per day, as determined
by the State Stream Sanitation Committee, in terms of
5-day, 20°C, BOD using the Thomas modification of
the Streeter-Phelps oxygen sag equation.
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133
The Steering Committee further recognized that circumstances
might arise beyond control of the power company wherein the
dissolved oxygen concentrations of the water discharged from
their Eoanoke Rapids powerhouse might fall below that quantity
required to sustain the assimilative capacity of 109,000 pounds
per day at minimum flows. Under these circumstances, the
assimilative capacity of the river could be maintained at the
109,000-pounds-per-day rate only by the release of water in
excess of the minimum flow schedule. To avoid the unnecessary
wastage of water at times when no peak power demand existed, the
Steering Committee further acceeded to the Virginia Electric and
Power Company the right to provide an instantaneous waste
assimilative capacity as low as the rate of 70,000 pounds per
day. The reduced assimilative capacity rate, however, could not
prevail for longer than eight hours and must be followed immedi-
ately by flows of sufficient magnitude to provide assimilative
capacity in excess of the 109,000-pound-per-day rate. The
excess rate of assimilative capacity would be maintained at
such a level as would compensate for the accumulative deficit
within a maximum period not exceeding one-half the duration of
the oxygen-deficient flows.
The Steering Committee further stipulated that under all
circumstances, the Eoanoke Rapids powerhouse must maintain
instantaneous discharges of not less than: 1,000 cfs during
the period November through March, inclusive; 2,000 cfs during
April and October.
The Steering Committee for Roanoke River Studies acted with the
conviction that the foregoing stipulations regarding the pro-
posed Gaston project are essential—in light of the known facts
of river performance--if the terms of the State's Pollution
Abatement Plan for the lower Roanoke River are to be met. Any
compromise towards less stringent requirements for the Gaston
project inevitably must result either in abrogation of the
assigned minimum classification standards for the lower Roanoke
River or in the imposition of more drastic requirements for
waste treatment placed upon the downstream polluters to com-
pensate for the further reduction of the river's assimilative
capacity by the Virginia Electric and Power Company's impound-
ments .
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b. Minimum Flew Requirements Respecting the Physiological Needs
of the Striped Bass
The minimum river flows required to satisfy the physiological
requirements of the striped "bass during their annual spawning in
the Roanoke River are less susceptible to conclusive proof than
are the minimum flovs required for river sanitation.
The duration of the period when minimum flows in excess of those
required for river sanitation are required for striped bass
spawning can be reliably estimated. The adult fish participating
in the annual spawning migration first enter the mouth of the
Roanoke River during late February or very early March--the
time depending in large part upon climatic conditions. Successive
recruitments of adult fish to the spawning population continue
until well into May when the last of the spawning fish enter
the river. The first adult migrants of the season are caught
in the vicinity of Roanoke Rapids-Weldon around April 1. The
spawning migrants then accumulate over the rapids area in
ever-increasing numbers until the time of first spawning--which
is rather clearly defined by water temperature. The time of
first spawning usually occurs sometime during the late April or
early May, depending upon climatic conditions of the year in
question. Following the initial spawning of the season, which
may be very intense if water temperatures rise rapidly, large
numbers of the spent females apparently return to the Sound.
The size of subsequent populations on the spawning grounds is
then governed by the rapidity of recruitment from later-running
fish from the Sound. Spawning usually subsides in the Roanoke
Rapids-Weldon area between June 1 and June 15, depending upon
seasonal water temperatures and stream flows. The spawning
population of striped bass, therefore,- are within the zone of
direct river influence during a period of some 120 days--ex-
tending from the time the first adult migrant enters the river
about March 1 until the last fry has left the river sometime
around July 1. The time of most critical exposure to river
conditions extends over a much shorter period from the time
adult fish have congregated in the rapids area in large
numbers (about mid-April) to shortly after the last signi-
ficant spawning has occurred in the river above Scotland Keck--
about June 15 under present conditions. The period during which
supplemental minimum river flows are required for protection of
the striped bass spawning therefore extends from April 1 to
June 30--with the most critical requirements existing between
April 25 and June 10.
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The location within the river where supplemental flows are
most favorable to spawning conditions for the striped bass
are even less well defined. Generally, it may be considered
as that part of the river accessible to striped bass above
the US-258 Highway (Scotland Heck) bridge at River Mile 102.4.
The rapids area--extending from the downstream end of the
Eoanoke Rapids powerhouse tailrace (approximately River Mile
135.4) across the eastern margin of the fall line to the
"Sluice" immediately below the US-301 Highway bridge (approxi-
mately River Mile 129-6)--is believed to represent the most
valuable spawning area for the striped bass. This belief
admittedly has not been subjected to accurate evaluation, and
it is predicted upon the following assumptions:
(l) Some reason must underlie the choice of the Roanoke
River as a spawning ground by the overwhelming majority
of the Albemarle Sound striped bass. The Tar River forms
the second, and numerically a far less consequential,
spawning ground for the Albemarle Sound striped bass.
These two tributaries apparently have some factor in
common which the striped bass prefer for a spawning area.
The most apparent common factor is that, unlike the other
tributaries of Albemarle Sound, the Roanoke and the Tar
contain rapids and the degree of usage of these two
tributaries by the spawning striped bass appears roughly
proportional to the original extent of their rapids
sections. In this connection, it is noteworthy that in
1884 the U. S. Fish Commission--with the entire Atlantic
Coast at their disposal—selected for hatchery site the
Roanoke River rapids area as the location where the
greatest concentration of striped bass were available
for artificial propagation.
(2) The buoyancy of the striped bass egg changes markedly
during incubation. As shown in Figure 10, these changes
are most rapid during the first three hours of life. The
fast, turbulent waters of the Roanoke River rapids provide
a maximum rate of vertical water movement and, therefore,
the most probable assurance that eggs will be held in
suspension during the heavy stages immediately following
spawning. After waterhardening, when the specific gravity
of the egg more closely approximates that of the surround-
ing medium, buoyancy of the egg would be assured by much
less rapidly moving water.
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136
(3) When an abundance of vater exists in the river, the
striped bass demonstrate - a marked preference for spawning
in the rapids area. Conversely, spawning downstream, from
the rapids section appears to result, in most instances,
from the fish being unwilling (or unable) to negotiate
the rapids on low-water stages rather than from any pref-
erence on the part of the fish for the quieter, downriver
area.
Considerable spawning by striped bass does occur each year
in the quieter river sections below the rapids. Presumably,
the products from spawning in the quieter river areas are
not entirely lost, even though the probability of egg
survival may be somewhat lower than in the fast water of
the rapids. Quantitative data are lacking which demonstrate
the comparative utilization of the rapids and the quieter
downriver areas by spawning striped bass. There is, however,
no convincing evidence contradicting the contentions of the
of the Beaufort Laboratory staff of the U. S. Fish and
Wildlife Service thats on a 13-15-foot Weldon stage, the
majority of spawning oceurs below River Mile 133j the fish
move farther upstream to spawn when water levels and
velocities are higher, and river discharges in excess of
15 feet at Weldon are required for full utilization of the
rapids' spawning areas.
With the general limits established for the time period
and the area of the Roanoke River over which supplemental
flows may be required to meet the physiological require-
ments of the spawning striped bass, the question then
follows as to what magnitude of minimum river flows is
required.
The results obtained during the three-year Roanoke River
Cooperative Study have not produced data by which the
water flows required for optimum spawning conditions for
the striped bass can be confllusively demonstrated. The
results have conclusively demonstrated, however, that
river conditions did produce one dominant year class
(1956 brood) of striped bass during the study period.
The minimum flows of 1956, per se, did not produce the
dominant year-class. Minimum flows could have been but
one--of presumably many--factors which, in the right
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1ST
combination, -were responsible for the dominant year class.
By the same reasoning, the minimum, river stages that
prevailed during the 195& season patently did not preclude
the development of a dominant year class when the remain-
ing pertinent factors happened to line up the right way.
The 1956 minimum river flows, therefore, may be accepted
as a pattern for a minimum flow schedule that has
demonstrated its efficacy.
Examination of the 1956 Weldon stage hydrograph during the striped
bass migration and spawning season (see Figure 8), reveals an
attraction flow reaching 23-2^ feet on March 27, 28, and 29. A
minimum river stage of 10.8 feet (2,000 cfs) then prevailed each
day (and was sustained over week ends) between March 30 and April 15
inclusive. The disposal of surplus water from Kerr Reservoir
occurred between April 16 and 21 during which period the daily
river discharges at Weldon varied between the turbine capacity at
the Roanoke Eapids powerhouse (ca. 2^.6 feet, 20,000 cfs) and a
minimum stage exceeding 20 feet. A single exception during this
period was a minimum stage of 15.5 feet recorded on April 20.
Between April 22 and May 2, inclusive, a st,eady 13-foot stage
(5j550 cfs) was maintained except for occasional very brief
power peaks slightly in excess of 15 feet (8,950 cfs) on April 26
and 27. On May 3; a minimum daily stage of 15 feet was established
and maintained through May l8--with many power peaks and periods of
sustained high flows (ca. 20 feet, 15,000 cfs) on at least four days
during the 16-day period. Available evidence indicates that the bulk
of the 1956 spawning occurred during the period of high minimum river
stages between May 3 and 18. On May 19, the minimum river stage was
reduced to the summertime weekday level of 10.8 feet (2,000 cfs).
That year, it was very apparent that concurrently with the drop in
minimum stage to 10.8 feet, virtually all fishing effort—and, pre-
sumably therefore, most of the fish then in the rapids area--imme-
diately moved downstream several miles below Weldon.
It was concluded, in the light of all available evidence and obser-
vations, that the physiological requirements of the spawning striped
bass will be fulfilled, at least in minimum degree, by the following
schedule of minimum discharges—to be measured at the U. S. Geological
Survey gage on the US-301 Highway bridge at ¥eldon:
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138
(l) Instantaneous discharges of not less than 2,000 cfs
from April 1, when the first of the spawners appears in the
Weldon area, to the date when eggs are first detected in
the river above Halifax--usually about April 25.
(2) Immediately following identification of first spawning,
the instantaneous minimum river discharge of 8,950 cfs
should be maintained to May 20, then reduced and held at
5,550 cfs until June 1 and as long thereafter as water
conditions will permit.
Definite provisions should be effected with the Corps of Engineers
and the Virginia Electric and Power Company whereby some flexibility
will be permitted in scheduling minimum flow changes on the exact
dates specified in the event of unusual climatic developments
during certain years, or should the Gaston Reservoir--if constructed--
significantly alter the current striped bass spawning pattern.
The recommendations of the Steering Committee for Roanoke River Studies
are present below:
The Steering Committee for Roanoke River Studies recommends that:
A. Respecting Roanoke River sanitation, minimum river discharges--
as measured at the U. S. Geological Survey Roanoke Rapids gage--be
maintained in sufficient volume as to provide adequate dissolved
oxygen above the required h.O parts per million at the critical
point of the'first major sag, for maintaining a minimum waste
assimilative capacity at the WC-lj-8 Highway bridge of 109,000
pounds per day--as determined by the State Stream Sanitation
Committee in terms of 5-day, 20°C, BOD using the Thomas modifica-
tion of the Streeter-Phelps oxygen sag equation. In the interests
of more efficient power generation and to avoid a needless waste
of water, an instantaneous waste assimilative capacity at a rate
not less than 70,000 pounds per day shall be permitted under the
conditions that the reduced assimilative capacity rate must not
prevail for longer than eight consecutive hours and it must be
followed immediately by discharges of sufficient magnitude to
provide an assimilative capacity in excess of the minimum 109,000-
pounds-per-day rate. The excess assimilative capacity rate must
be maintained at a level sufficient to compensate for the accumulated
oxygen deficit within a maximum period not exceeding one-half the
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139
duration of the oxygen-deficient flows * In addition, instanta-
neous discharges must be maintained in the river at the Roanoke
Rapids gage site not less than 1,000 cfs during the period
November through March, inclusive; 2,000 cfs during the period
May through September, inclusive; and 1,500 cfs during April
and October.
B. Supplemental river flows--as measured at the U. S. Geological
Survey gage on the US-301 Highway bridge at ¥eldon--be provided
during the annual spawning migrations of the striped bass and
other anadromous fishes, in accordance with the following schedule;
Instantaneous river discharges not less than 2,000 cfs between
April 1 and April 25; instantaneous discharges not less than
5,550 cfs between April 26 and May 4; instantaneous discharges
not less than 8,950 cfs between May 5 and May 20; instantaneous
discharges not less than 5>550 cfs between May 21 and June 1
and as long thereafter as water conditions will permit.
C. The effective dates for the supplemental flows provided to
meet the physiological requirements of anadromous fishes be
susceptible to some modification to conform with climatic
conditions of atypical seasons or to encompass any effects
that the proposed Gaston Reservoir, if constructed, may exert
upon the current striped bass spawning pattern.
D. Use of the water provided to meet the physiological require-
ments of anadromous fishes in excess of that provided under the
terms of the sanitation flow schedule be denied to river polluters
with controlled waste discharges. In other words, where wastes
are proportioned to river flow, the proportion should continue
to be coordinated with the appropriate sanitation flow and not
increased to take advantage of the supplemental flows provided
for the anadromous fishes,
E. A continuing investigation of the Roanoke River, the general
areas of which should includes
1. Surveillance
a. Respecting Water Quality
Year-round monitoring of water quality with emphasis
upon dissolved oxygen in the critical areas; to evaluate
reservoir performance; to determine the efficacy of the
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pollution abatement plan recommended by the Steering
Committee; and to provide a framework of reference
against which post-Gaston river conditions can be
compared. Toxicant monitoring also should be maintained
in the critical areas--particularly during the striped
bass season.
b. Respecting the Fisheries of the Roanoke River
Continuing studies of river and Sound catches of
striped bass by number, gear, and age composition;
spawning populations and escapement; egg production in
terms of total numbers, location of spawning, and
viability; young-of-the-year abundance estimates--all
pointed towards an annual evaluation of the contribu-
tion with prevailing river conditions.
F. An informal organization of the river interests be formed
to supplant the Steering Committee for Roanoke River Studies
which, as an ad hoc committee, fulfills its purpose with the
adoption of the Comprehensive Report of its study program. The
organization should function primarily as a continuing forum for
the expression and discussion of mutual interests of the river-
water users in the orderly development of the lower Roanoke
River basin.
THE RIVER DISCHARGES REQUIRED FOR EFFECTIVE SPAWNING BY STRIPED BASS IN
THE RAPIDS OF THE ROANOKE RIVER OF NORTH CAROLINA (DECEMBER 1, 1959)^
The objective of this report was to present minimum river discharges
considered necessary by the North Carolina Wildlife Resources Commission to
assure effective spawning by the Albemarle Sound striped bass. The report
reviews current knowledge of the life cycle of striped bass, emphasizing
the necessity of a current speed sufficient to assure buoyance for the
survival of the eggs.
The U.S. Fish and Wildlife Service estimated in 19^6 that successful
spawning could be maintained if minimum daily flows of 2,000 cfs together
with average monthly flows of 6,000 to 9>000 during April and May were
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lit-1
provided by the John H. Kerr Dam. In 1951 the Federal Power Commission
license for Roanoke Rapids Dam.provided for a minimum rate of flow of
2,000 cfs during the striped bass season for a period of up to 75 days
between March 15 and June 15. It also required that flows should not be
increased to double nor decreased to half in less than one (l) hour during
the spawning season.
The Worth Carolina Wildlife Resources Commission, the State agency
responsible for protection of the striped bass, has contended that the
minimum flow schedule was inadequate to maintain successful spawning.
VEPCO and the Corps of Engineers have cooperated with the Commission and
provided minimum flows in excess of those stipulated by the Federal Power
Commission.
Two reports were submitted to Task Force 3 of the Roanoke River
Cooperative Study relative to the striped bass spawning area in the Roanoke
River. Drs. Brandt and Hassler concluded that the majority of the spawning
originated between river mile 108, above Scotland Week, to river mile 130,
at Weldon.
The U.S. Fish and Wildlife Services' Beaufort Laboratory concluded
that spawning occurs predominantly from river mile 106 to river mile 137
but that at flows below 5,500 to 8,350, most spawning is confined below
river mile 133• A minimum flow of 5>550 was recommended for access of both
fish and fishing boats from Weldon to the vicinity of river mile 133-
THE MINIMUM RIVER DISCHARGES RECOMMENDED FOR THE PROTECTION
OF THE ROMOKE RIVER ANADROMOUS FISH (DECEMBER 1, 1960)^ .
The objective of this report is to present further information on the
minimum flows considered necessary by the North Carolina Wildlife Resources
Commission to assure effective spawning by the Albemarle Sound striped bass.
The Roanoke River is the most important spawning area for striped bass in
Worth Carolina and is important in sustaining an annual harvest of approxi-
mately 600,000 pounds, economically one of the largest fishing industries in
the State. The report reviews the information on the life cycle of the
striped bass and the flow requirements which are or have been in effect since
John H. Kerr Dam was completed. The conclusions of the 1959 report are
repeated except that the recommendations for minimum flow releases are based
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142
upon the maximum peaking flow in the previous 2^-hour period. This report
further makes provisions for reducing the draft on water stored for maintain-
ing spawning flows in exceptionally dry years so that it will not be pre-
maturely exhausted.
It is the responsibility of the North Carolina Wildlife Resources
Commission to protect the striped bass fishery in the Roanoke River
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SECTION 10
BIBLIOGRAPHY
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-------
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147
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