NC0024406_Dan River Summary Report_20091230

M
Duke
i€uer ►y®
CORPORATE EHS SERVICES
Duke Energy Corporation
526 South Church St.
Charlotte, NC 28202
Mailing Address:
EC13K / PO Box 1006
Charlotte, NC 28201-1006
December 30, 2009
�C z -V yl o �01���/Qe 1�WJ Com.
Mr. Jay Sauber P-�t�N11� eqf °�C, �/7'�/� 01 L
Environmental Sciences Branch �� �' tfki®
North Carolina Department of Environment
and Natural Resources
1621 Mail Service Center Pe el 11
�PF
Raleigh, NC 27699-1621
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Subject: Belews Creek Steam Station NPDES Permit NC0024406
2008 Dan River Summary Report f
Tear Mr_ Overton- 0i
�..CJ e ✓a/
Enclosed are three copies of the 2008 Dan River summary report, as required by Part I.A.(4.) of NPDES
permit No. NCO024406 for Belews Creek Steam Station in Stokes County, North Carolina. The selenium
concentration in fish muscle tissue remained well below the 10 µg/g concentration considered by the
North Carolina Department of Health and Human Services as the maximum safe concentration for human
consumption. This annual update continues to indicate no detrimental impact to the aquatic biota in the
Dan River from the discharge of Belews Creek Steam Station ash basin that was initiated in November;
1985.
If you have any questions concerning this report, please contact me at (980)-373-5710.
Sincerely,
Ron Lewis
Water Management
Attachments
xc w/att: Mr. Tom Belnick, NCDENR-DWQ, 1617 Mail Service Center, Raleigh, NC 27699-1617
JAN - 4 2010
DENR - WATER QUALITY
POINT SOURCE BRAtiG.Re-energy.com
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BELEWS CREEK STEAM STATION
2008 DAN RIVER SUMMARY
Principal Investigators:
Michael A. Abney
John E. Derwort
Keith A. Finley
DUKE ENERGY
Corporate EHS Services
McGuire Environmental Center
13339 Hagers Ferry Road
Huntersville, NC 28078
December 2009

ACKNOWLEDGMENTS
The authors wish to express their gratitude to a number of individuals who made significant
contributions to this report. First, we, are much indebted to the EHS Scientific Services field
staff in carrying out a complex, multiple -discipline sampling effort that provides the
underpinning of this report. We would like to thank Glenn Long and Brandy Starnes for
support in water quality sample collections. Kim Baker, Bob Doby, James Hall, Bryan Kalb,
Glenn Long, and Todd Lynn were vital contributors in completing fisheries collections and
sample processing. James Hall, Aileen Lockhart, Shannon McCorkle, and Jan Williams
contributed in macroinvertebrate sampling, sorting and taxonomic processing.
We would also like to thank multiple reviewers; including Penny Franklin, Duane Harrell,
Ron Lewis, and John Velte. The insightful commentary and suggestions from these
individuals and also between co-authors have benefited the report in myriad ways.
ii

TABLE OF CONTENTS
EXECUTIVESUMMARY.................................................................................................. iv
LISTOF TABLES...............................................................................................................
ix
LISTOF FIGURES...............................................................................................................
x
CHAPTER1- INTRODUCTION........................................................................................1-1
BACKGROUNDINFORMATION................................................................................1-1
DAN RIVER FLOW CHARACTERIZATION.............................................................1-2
CHAPTER2- FISH..............................................................................................................
2-1
MATERIALS AND METHODS....................................................................................
2-1
RESULTSAND DISCUSSION.....................................................................................2-1
CHAPTER 3- MACROINVERTEBRATES......................................................................
3-1
MATERIALS AND METHODS....................................................................................
3-1
RESULTS AND DISCUSSION.....................................................................................3-2
Habitat..........................................................................................................................
3-2
Bioclassification...........................................................................................................
3-3
Elemental Concentrations in Organisms......................................................................3-4
Selenium...................................................................................................................
3-4
Zinc...........................................................................................................................
3-5
Arsenic......................................................................................................................
3-6
AllElements.............................................................................................................
3-7
SUMMARY....................................................................................................................
3-7
CHAPTER 4- WATER AND SEDIMENT CHEMISTRY ...............................................
4-1
MATERIALSAND METHODS....................................................................................4-1
RESULTS AND DISCUSSION.....................................................................................4-3
Stream Flow Characterization......................................................................................4-3
SurfaceWater Quality..................................................................................................4-3
SeleniumLoading Rates..............................................................................................
4-7
Surface Water Trace Element Concentrations.............................................................
4-8
Sediment Trace Element Concentrations.....................................................................4-8
SUMMARY....................................................................................................................
4-9
LITERATURECITED.......................................................................................................L-1
APPENDIXTABLES.......................................................................................................
A-1
iii

EXECUTIVE SUMMARY
A decline in the Belews Lake fishery was observed during 1976 and was linked to trace
element (principally selenium) contamination and bioaccumulation resulting from discharge
of Belews Creek Steam Station (BCSS) ash basin effluent to the lake. The ash basin effluent
was re-routed to the Dan River in November 1985 as one of several remedies to the
contamination problem. North Carolina Department of Environment and Natural Resources
(NCDENR) subsequently mandated that Duke Energy monitor the recovery of Belews Lake
and assess the impact of the new discharge on the biota, water quality, and sediment
chemistry in the Dan River. As required by NPDES permit number NC0024406,
environmental monitoring upstream and downstream of the BCSS ash basin discharge
continued during 2008.
Muscle selenium concentrations in suckers and sunfish collected from Dan River sample
locations both up- and downstream of the ash basin discharge remained within the normal
background ranges for fish skeletal muscle tissue. Although selenium concentrations in fish
downstream of the ash basin discharge are consistently twice that of fish from the upstream
location, the concentrations have been similarly low within and among years indicating no
appreciable bio -accumulation or impairment of the Dan River fish community due to the
operation of BCSS. All concentrations were well below the 10 µg/g, wet weight,
concentration that warrants issuance of a consumption advisory.
Mean zinc concentrations were highest for sunfish and suckers at upstream locations and
lowest for both taxa downstream of the ash basin discharge. The low concentrations of zinc
in fish among locations in 2008, and since the inception of this program, may reflect regional
background levels. Zinc concentrations in muscle tissue of fish collected from the Dan River
do not appear problematic, as concentrations continue to be lower than concentrations (16.0
to 82.0 µg/g, wet weight) reported for several taxa of omnivorous freshwater fish from other
areas in the United States.
In 2008, selenium concentrations among most macroinvertebrate taxa, including Plecoptera
and Trichoptera, showed increases downstream of the ash basin discharge as compared to
2007, while the opposite was true at the upstream location. Concentrations among
Plecoptera downstream of the ash basin discharge were the highest since monitoring of these
forms began in 2005. Collections of trichopterans at the upstream location were insufficient
for analysis; however, concentrations from those collected downstream of the ash basin
iv

discharge were considerably higher than in 2007 and were the highest recorded since 2005.
The mean concentration of selenium in the Anderson Creek reference site samples of 1999
(0.86 gg/g) was higher than that for similar taxa at both Dan River locations in 2008.
Zinc concentrations in macroinvertebrates collected from the Dan River were well within
historical ranges. The mean zinc concentration from the Anderson Creek reference site
samples, 24.48 gg/g, was higher than the concentration recorded for similar taxa from both
locations on the Dan River in 2008.
Most arsenic values in macroinvertebrates collected in 2008 were below detection limits.
However, values above the limits were slightly higher than or similar to those of 2007. The
mean arsenic concentrations in Corbicula, Ephemeroptera, and Odonata from both upstream
and downstream sites were higher than the mean arsenic concentration of 0.30 gg/g at the
Anderson Creek reference site.
Compared to the previous eleven years, the total number of macroinvertebrate taxa upstream
of the BCSS discharge canal was the highest yet recorded, while the total number of taxa
downstream of the discharge was among the highest. Nevertheless, EPT taxa declined at
both locations since 2007. The bioclassification score at the upstream location declined
considerably since 2007 and was the lowest yet recorded, while the bioclassification score at
the location downstream of the BCSS discharge was similar to that of 2007 and was among
the highest recorded from this location since 1997. The lower than normal bioclassification
score upstream of the BCSS ash basin discharge may have been due to perturbation resulting
from exceptionally high flow which occurred just prior to sampling, as well as somewhat less
suitable habitat. Downstream bioclassifications have continued to be in the "Good -Fair" to
"Good" ranges over the course of time presented.
Based on total numbers of taxa, numbers of EPT taxa, and bioclassification scores, there do
not appear to be any long-term significant impacts of BCSS ash basin discharges on Dan
River macroinvertebrate communities. The data for 2008 indicate that the Dan River in the
vicinity of BCSS supports balanced and indigenous macroinvertebrate populations.
Dan River water quality in 2008 was generally comparable to that of other Piedmont streams
in the Duke Energy service area, as well as similar to historical data. Most Dan River water
chemistry indicators and analyte concentrations have remained comparable to those
measured prior to the diversion of the BCSS ash basin discharge to the Dan River. Water
VA

temperatures remained below the default North Carolina standard (32 °C). DO
concentrations consistently exceeded DO standards (minimal 5 mg/L as a daily average and 4
mg/L as an instantaneous value) in 2008, as in prior years.
Beginning in February 2008, the BCSS ash pond began receiving treated process wastewater
from a new internal NPDES discharge point associated with operation of the Unit 1 flue gas
desulfurization (FGD) system. Contributions from the Unit 2 FGD system followed
beginning in May 2008. As a result of this new air emissions -related internal wastewater
discharge and its influence on final ash pond effluent properties, several monitored analytical
variables demonstrated elevated levels during 2008 monitoring of the Dan River.
Beginning in spring 2008, specific conductance measured in the Dan River downstream of
the ash basin outfall was clearly elevated with respect to values from previous years and also
in comparison to the site upstream of the ash basin outfall. Levels of calcium and
magnesium likewise increased dramatically in the latter half of 2008, consistent with the
increased specific conductance following activation of the BCSS FGD systems.
Additionallly, concentrations of sulfate and chloride at Dan River sample locations
downstream of the BCSS ash basin outfall were slightly elevated compared to upstream
concentrations. Nonetheless, sulfate and chloride concentrations were not elevated in 2008
with respect to many earlier years.
Noted increases in calcium, magnesium, and sulfate which appear linked to new BCSS FGD -
related wastewater inputs are not anticipated to have bearing on aquatic life uses of the Dan
River. The maximum sulfate and chloride concentrations measured in 2008 were well below
the human health -based 250 mg/L standards. An estimate of the maximum TDS
concentration (187 mg/L) in 2008 was also well below the human health -based TDS
standard.
As previously documented in this ongoing study and as supported elsewhere, the Smith River
has typically affected water quality of the Dan River downstream of their confluence at Eden,
NC. Compared to upstream Dan River, 2008 Smith River pH, and concentrations of total
alkalinity, nitrate+nitrite, total nitrogen, orthophosphate, and total phosphorus were
significantly (P < 0.05) greater.
A comparison of 2008 Dan River water quality for sample locations immediately upstream
and downstream of the BCSS ash basin NPDES outfall resulted in slightly greater
vi

differentiation than has been recently observed. Significant (P < 0.05) concentration
differences between the two sites were primarily related to major dissolved minerals which
were linked to treated BCSS FGD wastewater. Analytes that displayed a significant increase
at the immediate downstream site relative to upstream included specific conductance, sulfate,
magnesium, and TS (corresponding to the TDS component).
Estimated mass loading of selenium to the Dan River via the BCSS ash basin discharge in
2008 was within the range exhibited in recent years. The 2008 225 g/d loading rate
represented a 7% decrease compared to the long-term average of 242 g/d. Selenium loading
was slightly above average during the first third of 2008, but near to or slightly below
average for the year.
As noted in prior years, 2008 Dan River (and lower Smith River) aqueous cadmium, lead,
and selenium concentrations were consistently below laboratory reporting limits and North
Carolina water quality standards. Copper and zinc concentrations also remained below the
NCDENR water quality action level for all 2008 samples. All 2008 Dan and lower Smith
River arsenic concentrations were well below North Carolina surface water quality standards,
with only one sample slightly exceeding the reporting limit.
Dry -weight selenium concentrations in Dan River surficial fine (< 63 µm) sediments
measured at four Dan River locations were similar to long term historical data, and were
within the range of concentrations measured before the routing of the BCSS ash basin
discharge to the river. All 2008 sediment selenium concentrations were of similar low
magnitude; below sample -dependent detection limits.
Arsenic concentrations in sediment fines ranged from below the detection limit to a
maximum of 37.8 µg/g. Arsenic concentrations in sediment fines from upstream and
downstream of the BCSS ash basin outfall, as well as at the downstream -most site were
similar. Two replicate samples collected from downstream of the Dan River Steam Station
(DRSS) diversion dam yielded the highest sediment arsenic concentrations observed to date,
averaging approximately 33 µg/g. However, from a long-term perspective, trace element
concentrations in Dan River fine sediments have not consistently increased since diversion of
the BCSS ash basin effluent to the Dan River.
Results of 2008 monitoring of Dan River biota, water quality, and sediment chemistry in the
vicinity of the BCSS ash basin discharge indicate that the effluent continues to have
vii

negligible impact on the receiving stream. These results are similar to those observed since
1985 when this monitoring program began. Findings continue to indicate the absence of any
short-term and long-term negative impacts which would limit the perpetuation of balanced
indigenous aquatic communities.
viii

M
CHAPTER 1
INTRODUCTION
BACKGROUND INFORMATION
Belews Creek Steam Station (BCSS) is a base -load, coal-fired electric generating facility
with two 1,110 -megawatt unitsa, located on Belews Lake, NC. Unit 1 began commercial
operation in August 1974, followed by Unit 2 in December 1975. During early operational
years, a decline in the Belews Lake fishery became evident, and was ultimately associated
with trace element (principally selenium) contamination and bioaccumulation resulting from
discharge of BCSS ash basin effluent to the lake.
In 1984 a dry fly -ash collection system was installed at BCSS to eliminate most wet ash
sluicing, thereby substantially lessening selenium and other trace element inputs to the ash
basin. Re -direction of ash basin effluent to the Dan River was implemented in November
1985. Related to these modifications, two required environmental monitoring programs were
subsequently stipulated by the North Carolina Department of Environment and Natural
Resources (NCDENR) in conjunction with the BCSS National Pollutant Discharge
Elimination System (NPDES) permit (NC0024406; NCDENR 2002, 2005b). One program
was designed to monitor the recovery of the Belews Lake ecosystem, while the other was to
assess the impact of the new discharge to the Dan River. Results of the Dan River
monitoring program, described in this report, are provided to NCDENR annually.
Environmental monitoring upstream and downstream of the BCSS ash basin discharge
continued in 2008 as required by the BCSS NPDES permit (Table 1-1; Figure 1-1). As in the
past, monitoring activities were designed to characterize potential impacts to selected Dan
River biota, water quality, and sediment chemistry resulting from BCSS ash basin effluent.
Details of monitoring methods and frequencies, as well as a discussion of 2008 monitoring
results, are provided in subsequent chapters of this report.
a BCSS generating units were down -rated from their previous 1120 megawatt rating in October 2008 after
installation of enhanced air emissions controls.
1-1

B
DAN RIVER FLOW CHARACTERIZATION
Regional precipitation was below normal in 2008. As occurred earlier in the decade, drought
conditions were again prevalent in the Southeast and in particular western North Carolina
from spring 2007 through early 2008. For North Carolina as a whole, the April 2007 —
March 2008 period proved to be the driest on record, with the most extreme precipitation
shortfall occurring in the western portions of the state (Corrigan 2009). At the Greensboro,
NC airport, a January — July 2008 cumulative precipitation deficit of 16.4 cm, or 24.9%
below normal, was recorded. Year-end total precipitation for the site was 10% below -normal
(Table 1-2; NCDC 2009).
The 2007 to mid -year 2008 drought period in the North Carolina and Virginia portions of
Dan River basin resulted in lower than average stream flows over much of the 2008 calendar
year. Dan River 2008 discharge gauged at Wentworth, NC, a site located approximately
mid -way among the monitoring locations included in this report (Figure 1-1), reflected the
continuation of low stream flows from the previous year (USGS 2009; Figures 1-2 and 1-3).
Median monthly flows for 2008 consistently fell below the 50th percentile of the period of
record (1940 — 2008) monthly medians for the site. For seven months (January — March,
June — August, and November), median flow did not exceed the 10th percentile of historical
monthly median flow. While it is typical of this ecoregion for maximum river flows to occur
in winter -spring, flows at the onset of calendar year 2008 were well below average.
Springtime flows increased somewhat in response to elevated April precipitation, but
substantially below -normal precipitation over the May — July period again led to severe
reductions in summer stream flow. The median flow at Wentworth in August 2008 (5.21
m3/s; 184 cfs) proved to be the lowest monthly median flow observed since an exceptionally
drought -impacted August 2002, and the 4th lowest monthly median flow over the entire 69
years of record for the site. The 2008 biological and chemistry sampling results are related to
Dan River hydrology where appropriate in subsequent chapters.
1-2

Table 1-1. Summary of environmental monitoring locations and sampling activity on the
Dan and Smith Rivers during 2008. (Locations displayed on Figure 1-1.)
b Latitude and longitude data obtained from TOM USGS mapping software (National Geographic Holdings, Inc. 2001)
1-3
Duke
River
Location Description
Report
Energy
-------
------------------------
Location
Location
County
Samples Collected
Latitude b
Longitude
Designation
Number
N
W
Dan River
US Highway 311 bridge east of
36° 19.620'
80° 05.724'
A
710.0
--------
Walnut Cove, NC; 4.3 km (2.7
Stokes Co.
mi) upstream of BCSS ash
basin discharge
------------------------
Fish, Macroinvertebrates,
Chemistry (incl. sediments)
B
720.0
Dan River
Off SR 1138 at Pine Hall Brick
36° 22.436'
79° 59.764'
--------
factory, southeast of Madison,
Rockingham
NC; 14.8 km (9.2 mi)
Co.
downstream of BCSS ash
basin discharge
------------------------
Fish, Macroinvertebrates,
Chemistry (incl. sediments)
C
729.0
Smith River
Kings Highway bridge in Eden,
36° 29.493'
79° 45.060'
--------
NC, 1.2 km (0.7 mi) upstream
Rockingham
of confluence with Dan River
Co.
------------------------
Chemistry
D
733.1
Dan River
Dan River Steam Station,
36° 29.151'
79° 43.133'
--------
below diversion dam and in
Rockingham
thermal discharge plume; 55.2
Co.
km (34.3 mi) downstream of
BCSS ash basin discharge
------------------------
Chemistry (incl. sediments)
E
705.0
Dan River
NC Highway 700 bridge, east
36° 29.936'
79° 40.879'
--------
of Eden, NC; 59.2 km (36.8 mi)
Rockingham
downstream of BCSS ash
Co.
basin discharge
------------------------
Fish, Chemistry (incl.
sediments
b Latitude and longitude data obtained from TOM USGS mapping software (National Geographic Holdings, Inc. 2001)
1-3

1•
Table 1-2. Precipitation at Greensboro, NC during 2008. (Data from NCDC 2009.) c
° Precipitation totals as water equivalent centimeters and inches
1-4
2008
Historical
Departure From
Departure From
Month
Precipitation
Average
Average
Average
(cm)
(in)
(cm)
(in)
(cm)
(in)
N
Jan
2.41
0.95
8.99
3.54
-6.58.
" =2.59 -
-73
Feb
6.73
' 2'.65
7.87
3.10,
-1.14
-0.45.
-15
Mar
10.95
.4.3.1
9.78
3.85
1.17
0.46,
12
Apr
13.84
" ' : 5:45
8.71
3.43
5.13
2.02
59
May
4.06
1.60
10.03
3.95
-5.97
-2.35
-59
Jun
6.55
2.58
8.97
3.53
-2.42
-0.95
-27
Jul
4.72
1.86
11.28
4.44
-6.56
-2.58
-58
Aug
17.98
7.08
9.42
3.71
8.56
3.37
91
Sep
12.40
4.88
10.92
4'.30,
1.48
- ' 0:58''
13
Oct
3.38
1.33
8.31
3.27
-4.93
-1.94
-59
Nov
7.11
" 2.80
7.52
; `2.96
-0.41
-0.16
-5
Dec
8.38
3.30
7.77
3.06-
0.61
0.24':
8
Total
98.51
38.79
109.57.
43.14 ,
-11.06
-4.35.'
-10
° Precipitation totals as water equivalent centimeters and inches
1-4

Virginia
------------------------------------------------ ---------------------------------------------------------------------------------------
North Carolina
sm
N r
N
N
y
� %E,
B C S S
Ash Basin
BCSS--
Stokes
--------------------
Forsyth
O C
U U
May dan
Madi n
B
eq USGS Wentworth Gauge
Dan
-------------------------
N C 7'
E
0
D
\DRSS
p
Belews
Lake Na 2 0 2
0
2 0 2 4 E
-------------nimmmmmiia
Rockingham
---------------
--------------------------
------
G uilford
Figure 1-1. Monitoring locations in Dan River upstream and downstream of the ash basin discharge of Belews Creek Steam Station,
NC.

w
E
1,000
100
10
35,310
10,000
3,531
n
1,000 y
353
100
1 I 35
sr � c0 1-- N M O N M '� Lo w c.- M O O N M it LO W c.- 00
co c0 c0 m W CO M M M M M M M M M M O O O O O O O O O
M M M M M M M M M M M M M M M M O O O O O O O O O
r- N N N N N N N N N
Figure 1-2. Hydrograph of daily average flows for the Dan River near Wentworth, NC
(USGS Station 02071000) from 1984 — 2008.
80--------•--------------------------------------------------------------------------------------------------•------------ — -------------------------
70 -------------------------------------------------------------------------------------------------- - 2,500
60 ------------------------------------------------------------------ —------------------- —
2,000
50 --------------- ---------- ----------- — -----— ------------ — — ----- — —
40 1,500
P7._—_--__ __--___—_ _____ ___ ____
E
-- --------------- --- --- -
1,000
500
10
0 0
1984198519861987198819891990199119921993199419951996199719981999200020012002200320042005200620072008
Figure 1-3. Monthly median flows for the Dan River near Wentworth, NC (USGS Station
02071000) from 1984 — 2008.
1-6

Mac �u im ve e I -,f bva- k�,
Locations A and B, respectively) were higher than the mean arsenic concentration of 0.30
gg/g at the Anderson Creek reference site (Table 3-6).
Poulton et al. (1995) reported arsenic concentrations that ranged from 6.8 µg/g nearest the
source of pollution to 0.68 gg/g 198 km downstream, while the concentration at the control
site was 0.54 gg/g. Farag et al. (1998) found arsenic concentrations from 0.42 to 0.48 gg/g at
reference sites and 0.44 to 19.40 gg/g at impacted sites. Location B had mean arsenic
concentrations somewhat higher than at reference sites mentioned by these authors, but
generally, concentrations were well below those from impacted sites in the literature.
All Elements
Most elemental concentrations in macroinvertebrates during 2008 were similar to or slightly
lower than in 2007. Additionally, concentrations were generally well within historical
ranges. Comparisons of macroinvertebrate elemental concentrations upstream with those
downstream of the BCSS discharge did not show consistently higher values downstream
verses upstream. This would indicate minimal impacts resulting on macroinvertebrates from
elemental uptake.
MMU'
Based on total numbers of taxa, numbers of EPT taxa, and bioclassification scores, there do
not appear to be any long-term significant impacts of BCSS ash basin discharges on Dan
River macroinvertebrate communities. The data for 2008 indicate that the Dan River in the
vicinity of BCSS supports balanced and indigenous macroinvertebrate populations.
3-7

CHAPTER 4
WATER AND SEDIMENT CHEMISTRY
MATERIALS AND METHODS
The Dan River water chemistry was sampled in 2008 at one location upstream (A) and three
locations downstream (B, D, and E) of the Belews Creek Steam Station (BCSS) ash basin
discharge (Table 1-1; Figure 1-1). An additional water chemistry sampling site (Location C)
was monitored on the Smith River, 1.2 km (0.7 mi) upstream of its confluence with the Dan
River. Quarterly sampling during 2008 occurred January 30, May 20, August 7, and October
29.
Water chemistry parameters were analyzed using standard analytical procedures (Table 4-1).
Near -surface (0.3 m) temperature, dissolved oxygen (DO), pH, and specific conductance
were determined in situ by Duke Energy Scientific Services personnels using a calibrated
Hydrolab DataSonde® (Hach Company 2006). Water grab samples were also collected at a
depth of 0.3 meters at each sample location. Samples for soluble nutrients (i.e., ammonia -N,
nitrite+nitrate-N, and orthophosphate) and dissolved copper were filtered (0.45-µm) on site.
All samples were preserved on site per Table 4-1 immediately after collection. With minor
exceptions, laboratory analyses were performed by Duke Energy Corporate EHS Services
Analytical Laboratory, Huntersville, NC (North Carolina Department of Environment and
Natural Resources [NCDENR] Certificate No. 248). Total solids (TS) and turbidity analyses,
and October 2008 total suspended solids (TSS) analyses were performed by Prism
Laboratories, Charlotte, NC (NCDENR Certificate No. 402).
Since 2001, trace element concentrations of river water samples have been analyzed as "total
recoverable" elemental concentration, which incorporates a dilute acidic digestion of the
sample (USEPA 1994). This technique was distinct from the analytical method for trace
elements employed during the period 1988 — 2000, when acid -preserved samples were
analyzed by atomic absorption spectroscopy direct injection, i.e., samples were not acid -
digested.
'The Duke Energy Scientific Services organization is presently certified by the North Carolina Division of
Water Quality (DWQ) under the Field Parameter Certification program (certificate number 5193).
4-1

Sediment cores (two replicates per location) were collected from wadable depths at the four
Dan River locations (A, B, D, and E) on May 22, 2008. Cores were collected in cellulose
acetate butyrate core liner tubes. Upon collection, sediment core tubes were sealed with
polyethylene end caps, with site water overlaying the intact water -sediment interface. Cores
were covered with ice and maintained upright to preserve the water -sediment interface and
subsequently refrigerated upon return to the lab. Fine surficial sediments at the sediment -
water interface were siphoned from the top 2-3 mm of each core sample, sieved through a
63-µm Nitex screen, and deposited on a pre -weighed, 0.45-µm Millipore acetate
membrane filter. Filters were dried at room temperature and analyzed for dry weight -based
selenium and arsenic concentration by neutron activation, as previously described (Duke
Power Company 1987).
Daily mean Dan and Smith River stream flows were obtained from the US Geological
Survey National Water Information System (NWIS) web site (USGS 2009). October 23
through December 2008 data obtained for the Wentworth, NC site were classified as
provisional at the time of this report. Estimated selenium mass loading to the Dan River
from the BCSS ash basin discharge was calculated from NPDES discharge monitoring report
discharge flows and selenium analyses.
Graphical methods were used to examine selected water quality and sediment elemental
concentrations for temporal and spatial trends. Statistical comparisons of water quality
parameters were made among sample locations, sample years, and historically referenced
low flow versus high flow sampling conditions (i.e., flows exceeding the 75"' percentile for
the entire Wentworth USGS gauge period of record) using an analysis of variance (ANOVA)
with Duncan's multiple range test (SAS Institute Inc. 2004). For all statistical tests,
significance was determined at a significance level of P < 0.05. Dan River sediment arsenic
and selenium concentrations and arsenic, cadmium, lead, and selenium concentrations from
aqueous samples for 2008 were not analyzed statistically due to the prevalence both in 2008
and historical data of analytical values below laboratory reporting limits.
4-2

RESULTS AND DISCUSSION
Stream Flow Characterization
Below normal Dan River flows predominated during the calendar year 2008 (Chapter 1), and
as a result, all 2008 water quality sampling events occurred under moderate to low river
flows (Table 4-2; Figure 4-1). In the most extreme example, August water quality sampling
was conducted with the Dan River at approximately the lowest 4th percentile of historical
seasonal flows, yet comparatively higher flows contributed by the Smith River at the time of
sampling increased Dan River flows downstream of the confluence of the two rivers at Eden,
NC.
Surface Water Quality
Dan River water quality in 2008 (Table 4-3; Figures 4-2 through 4-9) was generally
comparable to that of other Piedmont streams in the Duke Energy service area. With minor
exceptions, Dan and lower Smith River water quality constituent variability in 2008 also was
generally within the range observed in previous years, and the data tended to reflect
previously documented historical spatial and temporal relationships (Duke Power 1999,
2000, 2001, 2002, 2003, 2004, 2005; Duke Energy 2006, 2007, 2008). Most Dan River
water chemistry indicators and analyte concentrations have remained comparable to those
measured during the baseline (i.e., pre -discharge) period (January 1984 to October 1985).
Temperature and DO displayed typical seasonal variability in both the Dan and Smith Rivers
during 2008 (Table 4-3). Summer meteorological conditions generally present the greatest
challenges for compliance with thermal and DO water quality standards. Quarterly sampling
indicated that both parameters met applicable water quality standards (NCDENR 2007) in
2008, as has been the case historically during this monitoring program. All water
temperatures remained below the default North Carolina standard (32 °C). A minimum DO
concentration of 5.9 mg/L was recorded during the August quarterly sampling at Location B,
downstream of the BCSS ash basin discharge. Applicable DO standards for this part of the
Roanoke Basin, minimal 5 mg/L as a daily average and 4 mg/L as an instantaneous value,
were consistently exceeded in 2008 and in prior years, as was reported by NCDENR (2005a).
Consistent with recent monitoring, Dan River pH (Table 4-3) was near -neutral to slightly
alkaline. Smith River pH values tended to be slightly greater (i.e., more alkaline) than
4-3

upstream Dan River pH values, and therefore influenced the marginally greater pH values
usually observed at the lower Dan River sites compared to the locations upstream of the
Smith River confluence.
Major environmental controls aimed at the reduction of sulfur oxides in BCSS air emissions,
including related wastewater treatment systems, were completed in 2008. Beginning in
February 2008, the BCSS ash pond began receiving treated process wastewater from a new
internal NPDES discharge point associated with operation of the Unit 1 flue gas
desulfurization (FGD) system, followed by wastewater contributions from the Unit 2 FGD
system beginning in May 2008. Previous efforts to characterize wastewater from similarly
designed wet limestone, forced oxidation FGD systems have shown that FGD -associated
effluents typically have high concentrations of mineral salts, various trace elements, and
metals (EPRI 2006). Prior to reaching the ash basin, the combined FGD waste stream at
BCSS was effectively treated with a combination of conventional solids separation, followed
by a fixed bed bioreactor. These treatment processes effectively reduced concentrations of
key constituents of concern, including selenium and mercury, but residual concentrations of
total dissolved solids (TDS) in FGD process wastewater remained elevated with respect to
receiving waters, adding substantially to TDS within the existing ash pond. As a result of
this new air emissions -related internal wastewater discharge and its influence on final ash
pond effluent properties, several monitored analytical variables, principally major cations and
anions that can be linked to either the source coal or FGD -associated limestone,
demonstrated elevated levels during 2008 monitoring of the Dan River. The influence of this
FGD process wastewater on specific water quality analytes is further discussed below, where
appropriate.
Specific conductance, a surrogate measurement for TDS, had remained relatively constant
over the course of 1984 — 2007 monitoring. Beginning in spring 2008, however, specific
conductance measured in the Dan River downstream of the ash basin outfall (Location B)
was clearly elevated with respect to formerly encountered values at that site, but also in
comparison to Location A, upstream of the ash basin outfall (Table 4-3; Figure 4-2). During
particularly low river flows associated with the August and October sampling dates (after
both the BCSS FGD systems had been operating for several months), specific conductance
downstream of the ash basin discharge was respectively about 3.6 and 3.7 times conductance
values measured upstream — a clear indication of the increased dissolved solids inputs
attributable to the modified upstream wastewater source.
4-4

Before 2008, it was evident that total alkalinity (Figure 4-3) and calcium (Figure 4-4)
concentrations were gradually increasing in the Dan River, both up- and downstream of
BCSS. Levels of calcium and magnesium (Figure 4-5) increased dramatically in the latter
half of 2008, consistent with increases noted in specific conductance following activation of
the BCSS FGD systems. Calcium reached maximum concentrations (21.2 and 24.1 mg/L for
August and October 2008, respectively) immediately downstream of the BCSS ash basin
discharge (Location B), as did magnesium (5.6 and 5.8 mg/L, respectively for the same
samples). An average increase in calcium concentrations of about 22%, typical of prior
years, was observed in 2007 immediately downstream of the ash basin discharge (Location
B) relative to upstream (Location A) (Duke Energy 2008). By the latter half of 2008,
however, downstream (Location B) calcium concentrations were averaging about five times
those measured upstream. Similarly, Location B magnesium concentrations in latter 2008
averaged approximately three -fold those measured upstream, whereas only a 19% increase,
typical of prior years, was observed in 2007. It should be emphasized that due to the low
Dan River flows associated with summer and fall 2008 sampling events, the magnitude of
downstream increases noted for calcium and magnesium may somewhat overstate normally
anticipated future concentrations in the Dan River; obviously additional data to be collected
in this monitoring program under a variety of flow conditions will clarify future trends.
Samples collected at the most downstream site (Location E) in latter 2008 reflected
maximum calcium and magnesium concentrations (10.2 mg Ca/L and 3.4 mg Mg/L) relative
to the 25 -year span of the monitoring effort at that location. Due to downstream flow
accretion, calcium and magnesium concentrations during the latter half of 2008 represented a
1.7 to 2.1 -fold increase (Location A to Location E), contrasted to average downstream
increases observed in 2007 of about 47%.
Unlike calcium, a summer -fall increase in total alkalinity was not evident in the Dan River.
A reasonable explanation for this is that a compensatory downward adjustment in carbonate -
bicarbonate anions occurred. Such a reduction via a shift in the carbonate -bicarbonate -
carbon dioxide equilibrium would naturally take place, permitting the waterbody to maintain
its ionic balance in light of increased concentrations of other major ions (i.e., calcium,
magnesium, and sulfate).
Sulfate (Figure 4-6) concentrations during the most recent five years have remained
relatively consistent. While similarly true for chloride (Figure 4-7) monitored at Location A
and B, further downstream chloride concentrations have been more variable in recent years.
4-5

Following operation of the BCSS FGD systems, however, concentrations of either anion at
Dan River sample locations (B, C, and E) downstream of the BCSS ash basin outfall were
slightly elevated, with maximal sulfate concentrations at Location B (11 mg/L) attaining the
highest level observed for the site in more than a decade. Nonetheless, sulfate and chloride
concentrations were not elevated in 2008 with respect to many earlier years.
Increases in calcium, magnesium, and sulfate which appear linked to new BCSS FGD -related
wastewater inputs are not anticipated to have bearing on aquatic life uses of the Dan River.
Presently applicable water quality standards, based on human health criteria, include limits
for Class WS -IV waters for TDS (500 mg/L), sulfates (250 mg/L), and chloride (250 mg/L).
Maximal measured sulfate and chloride concentrations in 2008 remained well below the 250
mg/L standards (Table 4-3; Figures 4-6 and 4-7). An estimate of the maximum TDS
concentration (187 mg/L) encountered in 2008 (Location B, October 2008) derived from TS
minus TSS data was also well below the human health -based TDS standard.
Results from previous years have collectively illustrated a number of water quality
constituents for which concentrations typically increase from upstream to downstream in the
- t Dan River. For 2008 as a whole, this spatial trend proved significant (P < 0.05) for specific
conductance (Figure 4-2), alkalinity (Figure 4-3), nitrate+nitrite, total nitrogen,
orthophosphate, total phosphorus, sodium, potassium, chloride (Figure 4-7), and total copper
(Figure 4-8). As in past years, inability to discern spatial differences among sample locations
during 2008 for the trace elements arsenic, cadmium, lead, and selenium can be attributed to
the predominance of concentrations below laboratory reporting limits (Table 4-3).
Substantial temporal variability within water quality analytes commonly associated with
suspended material has occurred in response to short-term Dan River discharge fluctuations
(NCDENR 2000, 2005a). Historically, temporal fluctuations in Dan River suspended solids
loads and related changes in various physico-chemical properties associated with storm event
runoff are frequently of greater magnitude than any observed spatial heterogeneity in these
parameters. Because all 2008 water quality samplings were conducted at relatively low Dan
River flows, considerably less temporal variability was observed in turbidity or TSS
concentrations compared to 2007 or many prior years (Table 4-3).
As previously documented in this ongoing study (Duke Power 1999, 2000, 2001, 2002, 2003,
2004, 2005a; Duke Energy 2006, 2007, 2008) and as supported elsewhere (NCDENR 2000,
2001, 2005), the Smith River has typically affected water quality of the Dan River
4-6

downstream of their confluence at Eden, NC. Compared to upstream Dan River locations (A
and B), 2008 Smith River (Location C) pH, and concentrations of total alkalinity,
nitrate+nitrite, total nitrogen, orthophosphate, and total phosphorus were significantly (P <
0.05) greater. This listing comprises fewer analytes exhibiting significant increases as a
consequence of Smith River inputs than reported in recent years, with the major cations (e.g.,
calcium and magnesium) and anions (e.g., sulfate and chloride) being excluded largely due to
upstream Dan River concentration increases and temporal variability during the year arising
from the increasing TDS loading from BCSS FGD -related inputs.
A comparison of 2008 Dan River water quality for sample locations immediately upstream
(Location A) and downstream (Location B) of the BCSS ash basin NPDES outfall resulted in
slightly greater differentiation than has been recently observed. Significant (P < 0.05)
concentration differences between the two sites were primarily related to major dissolved
minerals, which as discussed previously, was in turn linked to treated BCSS FGD
wastewater. Analytes that displayed a significant increase at the immediate downstream site
relative to upstream included specific conductance, sulfate, magnesium, and TS
(corresponding to the TDS component).
Selenium Loading_Rates
Estimated mass loading of selenium to the Dan River via the BCSS ash basin discharge in
2008, at 225 g/d, was within the range exhibited in recent years (Figures 4-10 and 4-11). The
2008 loading rate, while slightly exceeding the 2007 rate, represented a 7% decrease
compared to the long-term average of 242 g/d. Selenium loading was slightly above average
during the first third of 2008, but near to or slightly below average for the year.
Because ash basin effluent flow rates remain relatively consistent from year to year, temporal
variations in selenium loading to the Dan River have historically been driven by fluctuations
in the selenium concentration of the ash basin effluent, which in turn, is influenced by
changes in quantities of flyash sluiced to the basin over time (Duke Power 2003). With the
operation of BCSS FGD systems beginning in 2008, no increases (conversely, decreases) in
selenium loading were observed at the final NPDES outfall, indicative of the highly
successful treatment afforded to FGD wastewater by the upstream fixed bed bioreactor.
Median and average NPDES discharge selenium concentrations for the year were 6.2 and 6.3
µg/L, respectively, with all values ranging between < 4.0 µg/L in February to 10.7 µg/L in
April.
4-7

Surface Water Trace Element Concentrations
Aqueous trace element concentrations remained low in 2008 Dan and lower Smith River
samples. Slightly elevated trace metal (e.g., copper, zinc, or lead) concentrations noted in
many previous annual summaries were not observed in 2008, primarily attributable to the
absence of higher flow sampling events (and lack of high TSS levels that often contribute to
particulate -bound metal concentrations). Similar to previous years, 2008 Dan River and
lower Smith River cadmium, lead, and selenium concentrations (Table 4-3) consistently
remained below laboratory reporting limits and North Carolina water quality standards
(cadmium: 2.0 µg/L; lead: 25 µg/L; selenium: 5 µg/L; NCDENR 2007). At mid -year,
laboratory reporting limits were changed for a number of trace elements — for arsenic,
copper, lead, and selenium the reporting limit was lowered from 2 to 1 µg/L, whereas the
cadmium limit increased from 0.5 to 1 µg/L. Only one sample, collected in August at the
most downstream site (Location E) yielded an arsenic concentration in excess of either
reporting limit: 1.4 µg/L. All 2008 Dan and lower Smith River arsenic concentrations were
well below North Carolina surface water quality standards (50 µg/L based on aquatic life,
and 10 µg/L based on human health; NCDENR 2007). Copper and zinc (Table 4-3; Figures
4-8 and 4-9) concentrations likewise consistently remained below the applicable NCDENR
(2007) water quality action levels (7 µg Cu/L; 50 µg Zn/L) for all 2008 samples.
Sediment Trace Element Concentrations
Dry -weight selenium concentrations in Dan River surficial fine (< 63 µm) sediments
measured at four Dan River locations were similar to long term historical data, and were
within the range of concentrations measured before the routing of the BCSS ash basin
discharge to the river (Table 4-4; Figures 4-12 through 4-15). All 2008 sediment selenium
concentrations were of similar low magnitude; below sample -dependent detection limits.
Arsenic concentrations in sediment fines ranged from below the detection limit to a
maximum of 37.8 µg/g (Table 4-4; Figures 4-12 through 4-15). Samples collected
immediately upstream (Location A) and downstream of the BCSS ash basin outfall (Location
B), as well as at the downstream -most site (location E), yielded similar, minimal arsenic
concentrations. Two replicate samples collected from downstream of the Dan River Steam
Station (DRSS) diversion dam (Location D), however, yielded the highest sediment arsenic
concentrations observed to date in the monitoring program, averaging approximately 33
µg/g. As the sample site is upstream of the DRSS ash basin discharge, potential sources for
4-8

the elevated arsenic at this sample point remain unclear. From a long-term perspective, trace
elemental concentrations in Dan River fine sediments have not shown a consistent increase
after diversion of BCSS ash basin effluent to the Dan River.
SUMMARY
Dan River water quality in the vicinity of BCSS in 2008 was, with minor exceptions, similar
to that of previous years. With the initial operation of FGD air emissions "scrubbers" at
BCSS occurring in 2008, an increase in several dissolved solids constituents immediately
downstream of the ash basin discharge, including calcium, magnesium, chloride, and sulfate
was evident. These slightly elevated cation and anion concentrations, however, were not of a
magnitude anticipated to affect resident Dan River biological communities. Mass loading of
selenium and arsenic to the Dan River via the BCSS ash basin discharge in 2008 was of
similar magnitude as observed in prior years, reflecting the highly effective treatment of
upstream, high -dissolved solids BCSS FGD system wastewater. All monitored water quality
indicators and constituent concentrations observed in 2008 Dan and lower Smith River
samples, including those of trace elements, remained within applicable North Carolina water
quality standards or action levels. Fine sediments collected from the Dan River in 2008 in
the vicinity of BCSS yielded low concentrations of selenium and arsenic, similar to previous
years. Arsenic was slightly elevated in a pair of samples collected downstream of the Smith
River confluence, below the DRSS diversion dam in Eden. The collective 2008 results of the
BCSS Dan River monitoring program continue to indicate no appreciable detrimental effects
attributable to the BCSS ash basin outfall, and that the waterbody, both up- and downstream
of the BCSS ash basin discharge, is capable of maintaining diverse, indigenous aquatic
communities.
HE