20150579 Ver 1_Report_20130301

Ward Mill Dam Hydropower Project FERC Project No. 9842-004
Run of River Operation
Mark A. Cantrell, U.S. Fish & Wildlife Service
Chris Goudreau, North Carolina Wildlife Resources Commission
Fred Tarver, North Carolina Division of Water Resources
I. Introduction.
The PAD describes the operation as "The plant is operated in a run -of -river mode at all times,
and is not used for peaking. Water flowing into the reservoir equals water flowing out". The
study was designed to develop boundary def*ni-'�ons for run -of river mode of operation, and
determine and refine maintenance and emergency drawdown and refill procedures. At a
minimum, the de(nihbns should include measures and rates of reservoir change that may
minimize (1) the risk of downstream stranding and dewatering, and (2) the poten+,al for
resuspension or discharge of sediments from the reservoir.
The Project is operated manually (Figure 1). During normal opera'�ons, the Licensee checks
inflow conditions and pond levels at the forebay by direct observation and by review of the
real-time USGS gaging staljon 03479000 WATAUGA RIVER NEAR SUGAR GROVE, NC. The data
from the USGS gaging staf, on is available via internet at 15 -minute /-.-'me step, and has minimal
41 me lag to the pond. The Project has two turbines and' generators with a total installed
capacity of 168 kW. One unit has a capacity of 75 kW and one unit has a capacity of 93 kW.
There are no provisions or plans to install future units. The average head of the plant is 16 feet.
The reservoir has an estimated surface area of 4.6 acres, and est; mated gross storage capacity
of 16.3 acre-ieeL. The es4i'mated hydfaUiiC L6paciLy of Lhe project is 158 Lis. The drainage area
at 0)F !Jars+ is estinnated to be 92.6 square ii'olif?s. `h.-- :4nouai ()!Scha(ge is 178 cfi
We. clevnloped a flow - operaTlon demonstrahn,^ study to determine the daisy and seasor:a!
range of reservoir levels, ramping rates and discharge under normal operators and for periodic
maintenance. This information was conducted to assess the potent"+"al effects of Project
opera on on aquatic and riparian resources, to develop a definition of "run -of -river" for the

Ward Mill Dam Hydropower Project FERC Project No. 9842-004
Run of River Operation
Project, and to provide details of how the operaf,on is monitored, controlled, and the range of
reservoir fAuctuJ on.
Addilionally, water quality data were gathered during thef/ow-operdlon demonstrdlon to
determine if there were any issues with dissolved oxygen or temperature changes within the
reservoir (i.e., does the small reservoir strAfy?). This informafion is necessary to minimize
potential impacts of water quality impairment on aqudic resources in the Watauga River.
Descrip'f;on of normal operaiing scenario.
Under normal operating condi4ions, the Project operates in run -of -river mode, with ingow
equal to oujflow and stable pond level. Ou)flow is generally managed by combina}ion of
discharge through one or both turbines, spill across the dam, and opera ;on of a low-level sand
gate (Table 1).
Table 1. Normal opera ng protocols of Ward Mill hydro project.
In ow (USGS gage) Unit 1 Unit 2 Spill
>500 cfs
Yes
Yes
Yes
<300 cfs
Yes
?
Yes
<160 cfs
Yes
No
No
<60cfs
Yes
No
No
<30 cfs
No
No
Yes
Maintenance drawdown and red ll sequence.
Maintenance drawdown is usually conducted under low Row condiloons, since the spillway is
uncontrolled, except for 2 small sand gates that have limited discharge capacity (Figure 2).
Under a maintenance drawdown scenario, Mows are diverted through the 191 low-level sand
gate, and along with leakage throubr the turbines, will pass i4lows urA the pond ievci is at the
desired stage. Reservoir refill minimizes the potenf;al to dewater the tailwater by Timing of
reiiii coincident with rising stage levels.
2

Ward Mill Dam Hydropower Project FERC Project No. 9842-004
Run of River Operation
Figure 1. Powerhouse controls.
Figure 2. Ward Mill dam showing sand gates.

Ward Mill Dam Hydropower Project
Run of River Operation
II. Methods.
FERC Project No. 9842-004
We evaluated run -of -river operations at Ward Mill Dam during 2011 - 2012. We deployed
digital water level/temperature sensors at the Project in order to measure conditions during
the periods July - November 2011, and March 2012 - February 2013, and to calibrate these
stage measurements to the stage and discharge values measured at the USGS gaging stkon
03479000 Watauga River near Sugar Grove, NC (Figure 3). The data from these water level
loggers and the USGS gaging sta4ion were compared with 15-minutelime step generaflon data
from the Project. Thef(ow - generaVion data are representative of the typical range of
general ion scenarios and Iow�jow conditions, and are helpful in describing the overall run -of -
river opera}ion limits.
We also deployed short-term stage/discharge and water quality monitors during a low inflow
period, to look more closely at pond vs. tailwater eleva}ions during low -tow operations and a
maintenance drawdown scenario. During this flow demonstration study, we deployed multiple
water level/temperature sensors at the Project pond and tailwater. Each logger was a
pressure-sen4ve transducer capable of recording pressure to within +0.075% of the actual
pressure (HOBO U20-001-01 Water Level).
Long-term monitors. We deployed long-term loggers to sample pressure/depth every 15
minutes. Water depth (accurate to 0.032-(f) was established by compensating water pressure
with ambient barometric pressure, recorded by an additional level logger secured to a tree
located approximately 100 yards from the project powerhouse. Compensat+on was performed
using HOBOware soRware (Onset Computer Corp) which also accounts for changes in water
density with changing water temperature.
Short-term monitors. These level loggers were programmed to collect -lane -scale data at 1 -
minute intervals during the demonstration, for comparison to the sequence and 4fming of
Changes in general+ori (generatGi' i iii 2 or both)' and gate openings/Closings (i7iaintein, ance and
refill scenarios). We also collected digital photographs at4ime intervals during the
demonstration, with temporary sta4gages and reference points visible.
On August 29-30, 2012, we conducted a cooperalive flow demonstrk,on exercise in order to
�
evaluate typical oNe4l'G,aniu "rfil;; at Vvaru Iv11ii duffing iovJlow condi]-ions.`r✓iiiic i tlivii
were low (42-48 cfs), the Froiev was operated with (:i) generator 1 between 1404 - t439 hrs.,
('2) both generators betweei-, 1648 - 1848 firs, acid (3) generator 1 aper 1848 hrs. We measured
stage, discharge, and dissolved oxygen (HOBO U26-001 Dissolved Oxygen) at sites in the
tailwater and pond during these demonstr4lon %ws.

Ward Mill Dam Hydropower Project
Run of River Operation
FERC Project No. 9842-004
Long-term (Depth at 15 -minute interval)
1- Tailwater level logger
2 - Pond level loeeer
Figure 3. Map of study area at Ward Mill dam.

Ward Mill Dam Hydropower Project FERC Project No. 9842-004
Run of River Operation
Discharge. We measured tailwater discharge with hand-held velocity meters (Price meter, Type
AA and pygmy and top-se-�fng wading rod (marked in tenths of a foot), and tape measure /
tagline (marked in tenths of a foot) (Figure, 4). We also described the cross-sed;on dimensions
at the tailwater using during low flow using a grade rod and laser level to generate diagrams
showing stream geometry perpendicular to the bankfull flow (Figure 5). Transect endpoints
were established above the range of expected {bows. We developed stage -discharge
relagionships at the Project by iterative comparison with water levels recorded simultaneously
at the USGS gage sta ion and those collected from the loggers during stable flow periods.
Figure 4. Measuring tailwater discharge with hand-held velocity meter and top-se4f, ng wading
rod.
C.

Ward Mill Dam Hydropower Project FERC Project No. 9842-004
Run of River Operation
110
105
0
0
C 100
M
E 95
to
>3
M 90
G
C
0
85
m
W
80
75
0 13 23 33 43 53
----Tailrace X -sec on water surface
•--- dam Pond X -sec on
-water surface (normal pond) • • • • • w.s. at drawdown (-4 )
Figure S. Cross -sed -ions surveyed at tailrace and pond during *(ow demonstration monitoring.
Dissolved Oxygen. Dissolved oxygen (DO) levels were measured at 1 -minute intervals using a
standalone logger (Onset Computer Corp., INC, U26, HOBO Dissolved Oxygen logger) with RDO®
Basic Technology to measure dissolved oxygen. The loggers were calibrated using a three-step
laboratory procedure, with a new replaceable opl;cal sensor cap (0.2 mg/L accuracy) and an
integrated temperature sensor using HOBOwareO so -aware for logger setup. Because the study
was of short duration, the data were offloaded directly from the logger, without correction for
ii,casurcment uri1 fvi.i ging. i�- L' IUgg�� v�a5 aiiC�iv�c o< <iiC ta•n uC% CCOSS-52d ,
approxiimatei•y 0.25 feet from the bm. in thjE thaiwcg. Another DO, lugger was deployed in
the pond nt approximately 2 feet from the 11-14 cm (`''tire !s). Each DO longer was depioyed in.
combinJion with a stage (depth) logger (Figure i).
7

Ward Mill Dam Hydropower Project
Run of River Operation
FERC Project No. 9842-004
Figure 6. Pond short-term dissolved oxygen and depth transducer were anchored at the pond
transect, approximately 120 feet upstream of the dam.
Figure 7. Tailwater short-term dissolved oxygen monitor and depth transducer were anchored
at the tailwater transect.

Ward Mill Dam Hydropower Project FERC Project No. 9842-004
Run of River Operation
III. Results.
Inf)ow to the project varied during the study (Figure 8 and Figure 9). We measured changes in
relafive stage -discharge across a range of flows. Stage and temperature varied daily and by
i
season. Pond and tailwater temperature were generally similar.
10000-- - -- - -- - - _
�� USGS 03479000 WATAUGA RIVER NEAR SUGAR GROVE, NC
during July 2011- Feb 2013
1320
i
1000
31-
311
2?6
V
in
10
f9
149
117
76
27
i
22
i
1
0% 10% 20% 30% 40% s0% 60% 70% 80% 90% 100%
Figure 8. Flow duraa'on curve for USGS gage on Watauga River during opera(ron study
Low-Llow operai-on demonstration. Inflow to the project was relairvely steady at 42-45 cfs
during the demonstration. The pond level dropped over three feet during the drawdown, but
the tailrace rose only about 0.7 feet (Figure 10). The temperatures measured at the pond and
do%Pjr stream at the tailrace diAered duri-E the chert -term study (P<O.()5) (Table 1 and Figure
11). Although DO levels in the tailrace and the pond sagged beginning at dusk,they remained
above 6 mg/I in the tailrace, while DO levels in the pond sagged lower during refill (Table 1 and
Figure 12). Mean DO levels were dif4erent between pond and tailwater (t=22.519. dj=4917,
P<0.05). The lower DO in the pond appears to be due to the effects of the real II. Data
(.l riniparinnog both loca�iors during stable 1. cir.d Ei�Jafiwi are u but Indicate thep-_ olid and
taiiwater DO ieveis track each other closeiy (r igure 9)
E

Ward Mill Dam Hydropower Project
Run of River Operation
FERC Project No. 9842-004
30 �- - 100
25--
�
20 — - ----
15 loo
ai i c4
CL s
E
~
to
I i I I I I i i
s
I I i I
0 I 1 --- I -- - - i. - -- - ---- ' 10
titi titi titi titi titi titi ti� titi titi titi ti� ti�
Tailrace Mean Daily, °C Pond Mean Daily, °C Max Q (cfs)
Figure 9. Stage and .nater temperature of Watauga River during 2012-2013.
10

Ward Mill Dam Hydropower Project
Run of River Operation
5.0
4.5
4.0
3.5
3.0
a
a
w
s 2.5
CL
v
C
W
FERC Proiect No. 9842-004
Ward Mill Dam Flow Demonstrali on
8.0
7.5
7.0
6.5
6.0 a
a
s
5.5 v
C
M
C
5.0 a°
1.5 4.5
1.0 4.0
0.5 3.5
0.0 3.0
12:00 18:00 0:00 6:00 12:00 18:00 0:00
Tailrace ( ) Gage Site Pond Depth
Figure 10. Demonstra4lon drawdown and reVill opera�.Jon on August 29 - 31, 2012. The Project
was operated with (1) generator 1 between 1404 - 1439 hrs, (2) both generators
during pond drawdown between 1648 - 1848 hrs, and (3) generator 1 affer 1848 hrs.
Tah!e 1. Summary of short-term data co!!ected during log^ l(ows and maintenance drawdown
demonstra#ion 4Iows.
1'
Pond Temp
TaNvater
Pond DO,
JSGS Temp,
Tailrace
Pond Temp,
at DO
--- —
-�O'' I
-- mS�'---
--�pv,_ _
Terre, °�
---"-oc —____LO
oq
N 1
2090
L9:,J
LO /'-r
L97L
2965
2963
!Year I
7.354
5.73?
7-2.650
%3.295
21 526
22.686
and Dev i
0.803
0,435
' •0`'=
S. E. j
1
0.015
0.023
0.028
0.07
0.008
0.013
Min I
2.850
6.790
19.948
21.664
21.091
21.187
Max
8.940
9.060
25.319
25.028
23.100
25.125
Median
7.150
5.490
22.525
23.388
21.378
22.525
1'

Ward Mill Dam Hydropower Project FERC Project No. 9842-004
Run of River Operation
30.0 20.0
Ward Mill Dam Flow Demonstralton
28.0 I �- 18.0
i
26.0 1- 16.0
24.0 14.0
22.0 ..,T 12.0
v --
� s�
20.0 1C.0 fl -
a, -o
CL
E 18.0 - 8,0 0
16.0 1 t 6.0
14.0 - -- -- - 4.0
12.0 2.0
10.0 0.0
8/29/12 12:00 8/29/12 18:00 8/30/12 0:00 8/30/12 6:00 8/30/12 12:00 8/30/12 18:00 8/31/12 0:00
LISGS Temp, *C Tailrace Temp, °C
Pond Temp,'C Pond Temp at DO Logger, 'C
Ford Depth
Figure 11. Temperature at each of the monitored sites on August 29 — 31, 2012.
12

Ward Mill Dam Hydropower Project FERC Project No. 9842-004
Run of River Operation
10.0 7)
Ward Mill Dam Flow Dernonstral Ion
I
I
9.0
9
r
_ . }
8.0 r. i._
i F — - 8
7.0 - -- 7
CL
,a
Q. {rFfr f F--
GJ
c 6 0 s 5 v
C -�
bo
XCU
5.0 5
4a
O
N
4.0 4
3.0 t ,,_ 3
2.0 2
12:00 18:00 0:00 6:00 12:00 18:00 0:00
Pond Depth Tailwater DO Pond DO
Figure 12. Dissolved oxygen levels in the Project tailrace and pond on August 29 — 31, 2012.
13

Ward Mill Dam Hydropower Project
Run of River Operation
IV. Discussion.
FERC Project No. 9842-004
Based on the results of our study of the run -of -river operai on of the Ward Mill Project, the
Project should be operated in run -of -river mode. Although we measured di erences in
dissolved oxygen and temperature during drawdown and re'll, these clk�rences were slight,
and temporary. Extra cau'.on should be used when opera ng the Project when the USGS gage
reads less than 60 cfs in order to avoid drawdown of the pond and to protect tailwater
resources from dewatering. Re.,.11 following maintenance or emergency drawdown should be
done when in ows are greater than 60 cfs.
14