NC0004961_Proposed Semiannual Vertical Profiles_19880504

State of North Carolina
Department of Natural Resources and Community Development
Division of Environmental Management
512 North Salisbury Street • Raleigh, North Carolina 27611
James G Martin, Governor R Paul Wilms
S. Thomas Rhodes, Secretary May 4, 1988 Director
Mr. Ralph Roberts
Duke Power Company
Fossil Production
P.O. Box 33189
Charlotte, NC 28242
Dear Mr. Roberts:
Duke Power has proposed semiannual vertical profiles of 27 water
quality parameters at five instream stations to determine the impact of the
discharge from the Riverbend plant (attached). Recent discussions with Duke
Power and DEM resulted in a permit requirement for development of a study
plan by June 1, 1988. Therefore, a one-year study could be completed prior
to permit expiration on 8/31/89. As a result, the previous plan submitted
by Duke has been reviewed, and several suggestions for both focusing and
broadening the scope of the study have been made. These include: perform-
ing water column sampling during summer minimum release, including horizon-
tal sampling in the mix zone, targeting key parameters, and including fish
tissue and sediment sampling. These recommendations pertain to a one-year
program. After data collection and review, adequate information should be
available to flag areas of concern and determine the necessity for and scope
of monitoring.
Specific Sampling Design Considerations
T. Water Column Sampling
A. Parametric Coverage
High priority (H) and low priority (L) parameters are indicated in
Duke's sampling design (attached).
B. Frequency
At least two sampling runs during this summer's growing season are
recommended. Further sampling would be beneficial, but not as
useful as growing season sampling.
Pollution Prevenlion Pays
PO Box 27687, Raleigh, North Carolina 27611-7687 Telephone [phone]
An Equal Opportunity Affirmative Action Employer

C. Spatial Coverage
Agree with vertical sampling concept. 2 m intervals may be
sufficient for metals, depending on results of previous sampling,
pilot run, or initial sampling efforts. If sufficient vertical
data exists, can also consider stratified sampling.
Plan should address horizontal variability because of incomplete
mix (i.e., within 3 miles of discharge).
D. Flow Considerations
Daily and monthly average release from Cowans Ford and Mountain Island
dams should be reported. During the week of water column sampling,
hourly release should be reported. Sampling runs should be completed
during periods of minimum release from both operations (at least twice).
II. Sediment
Suggest as highest priority: As, Hg, Cu, Cd, Pb, Se, Ni. One time sampling
with a minimum of three replicates and preferably five replicates per sta-
tion this summer. Upstream, downstream. Include horizontal sampling in mix
zone. Because net sedimentation will be higher nearer the dam, it may be
appropriate to have a sediment station located further downstream.
ITI. Fish Tissue
Suggest one time sampling with priority metals shown above, except
copper.
IV. Miscellaneous Comments
Because of the large amount of dilution (average = 400:1; critical period
10:1) and rapid uptake, sorption, and settling frequently exhibited by
many of the parameters of interest, the key element in this program will be
biomonitoring. Another environmental consideration is the rapid flushing
(average retention time = 10 days) relative to, for example, Hyco and
Belews lakes.
Please advise if questions.
Sincerely yours,
�d,_ CC ­6e C �Cp
_Handy Dodd
Attachment
RD/gh
CC: Jay Sauber
Steve `Pedder

�r
5.1 Problem Time Scales
The appropriate time scale of the problem is again approximated by the
time to steady-state calculations presented in Section 3.2. Sufficient
data should be collected on inputs and water quality responses during this
period so that reasonable average values can be used for the steady-state
analyses.
The time scale of chemical buildup in bed sediments can be highly
variable. The chemical buildup in bed sediments is caused by diffusion of
chemical from the water column into the bed and by the initial exchange of
particulate chemical between water column and bed by settling and
resuspension. In situations where the chemical has weak partitioning
characteristics and is primarily in the dissolved state in the water
column, chemical buildup in the sediment will be controlled primarily by
diffusive exchange, a relatively slow process. For strongly partitioning
chemicals, chemical buildup in the sediment may be dominated by particulate
exchange through settling and resuspension.
Guidelines for time scales in sediments are approximate at best. In
lakes, time scales may be in the order of months to years. From a water
quality field survey standpoint, practicality dictates that the problem
time scale as defined for the water column will be used as a guide for most
intensive field work. However, as the time scale for bed sediments may be
substantially larger, it would be desirable to obtain chemical loading
information periodically over a roughly equivalent period of time.
5.2 Location of Sampling Stations
In lakes, concentration gradients are likely to be a function of depth
and width as well as time of flow. Sampling locations in lakes should
therefore be oriented around the sources so that gradients will be
measured. This usually calls for closely spaced sampling stations near
outfalls and more widely spaced stations at distances from the outfall.
When appropriate, it may be advantageous to perform a dye or tracer study
5-2

to determine the mixing characteristics of the lake or impoundment. This
type of study will also give insight to the appropriateness of a completely
mixed assumption.
Figure 5-1 shows two different lake configurations, one which is
completely mixed over volume and one which is not well mixed. Potential
sampling locations for each lake are also shown on Figure 5-1. For unmixed
Lake A, samples can be collected at each station and at various depths from
surface to bottom. In Lake B which is mixed over depth and width, samples
are required only at a single point in the water column, perhaps mid -depth.
5.3 Water Quality Measurements
For calibration purposes, water quality data are required in both water
column and sediment as shown in Table 5-1 and discussed below.
TABLE 5-1. SUMMARY OF WATER QUALITY MEASUREMENTS
WATER COLUMN
Required
1. dissolved chemical
2. particulate chemical
3. suspended sediment
4. particulate organic carbon
BED SEDIMENT
Required
1. dissolved chemical
2. particulate chemical
3. solids concentration
(fine fraction)
4. porosity
5. particulate organic carbon
5-3
Supplemental
1. conservative tracer
- total dissolved solids
- chlorides
- conductivity
2. temperature
3. pH
4. light intensity with depth
(ultraviolet penetration)
5. particle size distribution
Supplemental
1. measure with depth
2. particle size distribution
3. pH

,pin CHEMICAL % QIn
LOAD
%� ®®
SCALE
Qln ® 0 i°
MILES
® (A) NON -MIXED
LAKE
/gout
CHEMICAL
LOAD
I-
0 os
MILES
(B) MIXED LAKE
L EGENO r
® SAMPLING STA
LOCATIONS
(C) NON -MIXED LAKE
VERTICAL PROFILE
Figure 5-1. Example Sampling Station Lccations

5.3.1 Water Column
Analysis should be performed for the chemical of concern in both
dissolved and particulate form. The concentration of suspended solids at
each sampling location should also be determined for subsequent use to
estimate settling and resuspension rates. Particulate organic carbon
(poc), which may strongly influence organic chemical partitioning should
also be measured. Additional data which may be useful are measurements of
conservative tracers in the water column. These tracers are useful to
evaluate the mixing characteristics in lakes.
Temperature and pH measurements may be required to modify laboratory
reaction kinetics to lake conditions. For photosensitive chemical, data
should be gathered on surface light intensity and the depth distribution of
sunlight in the water column.
5.3.2 Sediment Layer
, Dissolved and particulate chemical measurements are also required in
the sediment layer to perform the impact analysis. For many chemicals,
most of the chemical mass is adhered to sediment in the bed. In this case,
measurements of total chemical in the sediment layer as grams of chemical
per gram dry weight sediment solids, together with bed sediment solids
concentration and porosity, are sufficient to estimate the total mass of
chemical in the bed. Again, poc should be measured to help determine
organic partitioning characteristics. The dissolved concentration in the
interstitial water, cd2, should also be measured for the purpose of
estimating the partition coefficient in the sediment layer. Bed sediment
chemical concentrations are usually measured in the top few centimeters of
the bottom material, in the mixed layer, as discussed in Section 2.0.
However, measurements of chemical at various depths in the sediment (i.e.,
core samples) may be useful to more accurately define the well mixed layer
and total mass of chemical in the sediments. In cases where the chemical
under analysis partitions differently depending on the size of each
sediment particle, particle size distributions should be developed for both
water column suspended solids and bed sediments.
5-5 �

DIVISION OF ENVIRONMENTAL MANAGEMENT
April 26, 1988
MEMORANDUM
T0: Ken Eagleson
Jay Sauber (� n
Steve Tedder
FROM: Randy Dodd _acb
THRU: Trevor Clements
SUBJECT: Duke Power Riverbend Sampling Program Review
Summary
Duke Power has proposed semiannual vertical profiles of 27 water
quality parameters at five instream stations to determine the impact of the
discharge from the Riverbend plant (attached). Recent discussions with Duke
Power and DEM resulted in a permit requirement for development of a study
plan by June 1, 1988. Therefore, a one-year study could be completed prior
to permit expiration on 8/31/89. As a result, the previous plan submitted
by Duke has been reviewed, and several suggestions for broadening the scope
of the study have been made. These include: increasing water column sam-
pling from biannual to quarterly, including horizontal sampling, targeting
key parameters, including flow considerations, and including fish tissue and
sediment sampling. These recommendations pertain to a one-year program.
After data collection and review, an abbreviated program based on the
results and statistical considerations may be warranted.
Specific Sampling Design Considerations
I. One -Year Study
A. Water Column Sampling
1. Parametric Coverage
High priority (H) and low priority (L) parameters are indicated
in Duke's sampling design (attached).
2. Frequency n
J_. _ U__3-- --w o sc _ Y-0 V -, S. 5 o
a* Lerlathe ^n �I,gy xV recommended.

3. Spatial coverage
Agree with vertical sampling concept. 2 m intervals may be
sufficient for metals, depending on results of previous samp-
ling, pilot run, or initial sampling efforts. If sufficient
vertical data exists, can also consider stratified sampling.
Plan should address horizontal variability because of incom-
plete
nco—plete mix
4. Flow considerations
Daily and monthly average release from Cowans Ford and Mountain
Island dams should be reported. During the week of water
column sampling, hourly release should be reported. Sampling
runs should be completed during periods of minimum release from
both operations)�at least twice, dtar= ^� a� ' LLLL U111C
zperat4,an_
II. Sediment
Suggest as highest priority: As, Hg, Cu, Cd, Pb, Se, Ni.
One time sampling wither h's summer. Ups ream, owns ream.
Include horizontal samplin�x' zone ll- d �, (''-`�.^""..►
III. Fish Tissue
Suggest one time sampling with priority metals shown above, ncaY'� `►4r co.
IV. ing eview
I'- • • • • •• ••.U.. �rin
V. Miscellaneous Comments
Because of the large amount of dilution (average = 400:1; critical
period = 10:1) and rapid uptake, sorption, and settling frequently
exhibited by many of the parameters of interest, the key element in
this program will be biomonitoring. Another environmental consider-
ation is the rapid flushing (average retention time = 10 days) relative
to, for example, Hyco and Belews lakes.
Attachment
RD:gh
cc: Dave Lenat
Vince Schneider