20030147 Ver 0_Report_20110113

Yadkin-Pee Dee River Hydroelectric Project
FERC No. 2206
Continuous Water Quality Monitoring in the
Pee Dee River below the Tillery and Blewett
Falls Hydroelectric Plants,
May-October, 2006-2009
PROGRESS ENERGY
December 2010
TABLE OF CONTENTS
Section Title PaLre No.
LIST OF FIGURES ....................................................................................................... IV
LIST OF TABLES ......................................................................................................... XI
ACRONYM LIST .................................................................................................... AL- I
EXECUTIVE SUMMARY .......................................................................................... ES-1
SECTION 1 - INTRODUCTION .................................................................................... 1-1
SECTION 2 - STUDY OBJECTIVES ............................................................................. 2-1
SECTION 3 - SITE DESCRIPTION ............................................................................... 3-1
3.1 Reach 1 - Pee Dee River Below the Tillery Development .....................................................3-1
3.2 Reach 2 - Pee Dee River Below the Blewett Falls Development ......................................... ..3-1
SECTI ON 4 - METHODS ............................................................................................ 4-1
4.1 Continuous Monitor Locations ............................................................................................. ..4-1
4.2 Continuous Monitor Deployment ......................................................................................... ..4-3
4.3 Continuous Monitor Service and Calibration ..................................................................... ..4-3
4.4 Data Validation and Review .................................................................................................. ..4-3
4.5 Quality Assurance and Quality Control ............................................................................... ..4-4
RESULTS AND DISCUSSION
SECTI ON 5 - ENVIRONMENTAL AND RESERVOIR CONDITIONS ................................. 5-1
5.1 Environmental Conditions .................................................................................................... ..5-1
5.1.1 Climatological Conditions ........................................................................................................ ..5-1
5.1.2 River Flow Conditions ............................................................................................................. ..5-2
5.2 Dissolved Oxygen in Project Reservoirs ............................................................................... ..5-7
5.2.1 Lake Tillery .............................................................................................................................. ..5-7
5.2.2 Blewett Falls Lake .................................................................................................................... 5-10
SECTION 6 - 2006 WATER QUALITY RESULTS ......................................................... 6-1
6.1 Water Quality in the Pee Dee River, 2006 ..............................................................................6-1
6.1.1 Dissolved Oxygen - Tillery Dam to Turkey Top Creek (Reach 1) ............................... .............6-1
6.1.2 North Carolina Water Quality Standards for DO in Reach 1 ........................................ .............6-5
6.1.3 Operational Effects of the Tillery Hydroelectric Plant .................................................. ............. 6-8
6.1.4 Dissolved Oxygen - Blewett Falls Dam to Below Hitchcock Creek (Reach 2) ........... ...........6-12
6.1.5 North Carolina Water Quality Standards for DO in Reach 2 ........................................ ...........6-16
6.1.6 Operational Effects of the Blewett Falls Hydroelectric Plant ....................................... ........... 6-19
i
TABLE OF CONTENTS
(Continued)
Section Title PaLre No.
6.2 Water Temperature in the Pee Dee River ............................................................................ 6-21
6.2.1 Reach 1 - Tillery Dam to Turkey Top Creek ........................................................................... 6-21
6.2.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek ........................................................ 6-22
6.3 pH in the Pee Dee River ......................................................................................................... 6-24
6.3.1 Reach 1 - Tillery Dam to Turkey Top Creek ........................................................................... 6-24
6.3.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek ........................................................ 6-25
6.4 Specific Conductance in the Pee Dee River .......................................................................... 6-26
6.4.1 Reach 1 - Tillery Dam to Turkey Top Creek ........................................................................... 6-26
6.4.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek ........................................................ 6-28
SECTION 7 - 2007 WATER QUALITY RESULTS ......................................................... 7-1
7.1 Water Quality in the Pee Dee River, 2007 ..............................................................................7-1
7.1.1 Dissolved Oxygen - Tillery Dam to Turkey Top Creek (Reach 1) .......................................... ..7-1
7.1.2 North Carolina Water Quality Standards for DO in Reach 1 ................................................... ..7-7
7.1.3 Operational Effects of the Tillery Hydroelectric Plant ............................................................. .. 7-9
7.1.4 Dissolved Oxygen - Blewett Falls Dam to Below Hitchcock Creek (Reach 2) ...................... 7-13
7.1.5 North Carolina Water Quality Standards for DO in Reach 2 ................................................... 7-17
7.1.6 Operational Effects of the Blewett Falls Hydroelectric Plant .................................................. 7-20
7.2 Water Temperature in the Pee Dee River ............................................................................ 7-21
7.2.1 Reach 1 - Tillery Dam to Turkey Top Creek ........................................................................... 7-21
7.2.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek ........................................................ 7-23
7.3 pH in the Pee Dee River ......................................................................................................... 7-24
7.3.1 Reach 1 - Tillery Dam to Turkey Top Creek ........................................................................... 7-24
7.3.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek ........................................................ 7-26
7.4 Specific Conductance in the Pee Dee River .......................................................................... 7-27
7.4.1 Reach 1 - Tillery Dam to Turkey Top Creek ........................................................................... 7-27
7.4.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek ........................................................ 7-28
SECTION 8 - 2008 WATER QUALITY RESULTS ......................................................... 8-1
8.1 Water Quality in the Pee Dee River, 2008 ..............................................................................8-1
8.1.1 Dissolved Oxygen - Tillery Dam to Turkey Top Creek (Reach 1) .......................................... ..8-1
8.1.2 North Carolina Water Quality Standards for DO in Reach 1 ................................................... .. 8-9
8.1.3 Operational Effects of the Tillery Hydroelectric Plant ............................................................. 8-10
8.1.4 Dissolved Oxygen - Blewett Falls Dam to Below Hitchcock Creek (Reach 2) ...................... 8-12
8.1.5 North Carolina Water Quality Standards for DO in Reach 2 ................................................... 8-15
8.1.6 Operational Effects of the Blewett Falls Hydroelectric Plant .................................................. 8-20
8.2 Water Temperature in the Pee Dee River ............................................................................ 8-20
8.2.1 Reach 1 - Tillery Dam to Turkey Top Creek ........................................................................... 8-20
8.2.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek ........................................................ 8-22
8.3 pH in the Pee Dee River ......................................................................................................... 8-24
8.3.1 Reach 1 - Tillery Dam to Turkey Top Creek ........................................................................... 8-24
11
TABLE OF CONTENTS
(Continued)
Section Title Page No.
8.3.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek ........................................................ 8-26
8.4 Specific Conductance in the Pee Dee River .......................................................................... 8-27
8.4.1 Reach 1 - Tillery Dam to Turkey Top Creek ........................................................................... 8-27
8.4.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek ........................................................ 8-28
SECTION 9 - 2009 WATER QUALITY RESULTS ......................................................... 9-1
9.1 Water Quality in the Pee Dee River, 2009 ..............................................................................9-1
9.1.1 Dissolved Oxygen - Tillery Dam to Turkey Top Creek (Reach 1) ............................... .............9-1
9.1.2 North Carolina Water Quality Standards for DO in Reach 1 ........................................ ............. 9-4
9.1.3 Operational Effects of the Tillery Hydroelectric Plant .................................................. ............. 9-7
9.1.4 Dissolved Oxygen - Blewett Falls Dam to Below Hitchcock Creek (Reach 2) ........... ............. 9-9
9.1.5 North Carolina Water Quality Standards for DO in Reach 2 ........................................ ...........9-13
9.1.6 Operational Effects of the Blewett Falls Hydroelectric Plant ....................................... ........... 9-16
9.1.7 Comparison of DO Temporal Trends, 2004-2009 ........................................................ ...........9-16
9.2 Water Temperature in the Pee Dee River ........................................................... .......... 9-23
9.2.1 Reach 1 - Tillery Dam to Turkey Top Creek ................................................................ ...........9-23
9.2.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek ............................................. ........... 9-24
9.3 pH in the Pee Dee River .........................................................................................................9-26
9.3.1 Reach 1 - Tillery Dam to Turkey Top Creek ................................................................ ...........9-26
9.3.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek ............................................. ........... 9-27
9.4 Specific Conductance in the Pee Dee River ..........................................................................9-28
9.4.1 Reach 1 - Tillery Dam to Turkey Top Creek ................................................................ ...........9-28
9.4.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek ............................................. ...........9-30
SECTION 10 - SUMMARY ....................................................................................... 10-1
SECTION II -REFERENCES .................................................................................... 11-1
APPENDICES
APPENDIX A SUMMARY OF CONTINUOUS MONITOR PERFORMANCE IN
REACHES 1 AND 2 OF THE PEE DEE RIVER BELOW THE TILLERY
AND BLEWETT FALLS HYDROELECTRIC PLANTS, 2006-2009
iii
LIST OF FIGURES
Figure Title Page No.
3-1 Map of the Tillery Development and Reach 1 of the Pee Dee River showing
continuous water quality monitoring stations ...................................................... 3-2
3-2 Map of the Blewett Falls Development and Reach 2 of the Pee Dee River
showing continuous water quality monitoring stations ....................................... 3-3
5-1 Comparison of monthly precipitation totals during the 2006-2009 period
to the 71-year monthly averages for the period 1938 to 2009 ............................. 5-1
5-2 Comparison of mean monthly air temperatures during the 2006-2009
period with the 71-year monthly averages of air temperatures for the period
1938 to 2009 ........................................................................................................ 5-2
5-3 Daily mean stream flow for the Rocky River at the N.C. Highway 52 Bridge
and the Pee Dee River at the U. S. Highway 74 Bridge, 2006-2009 .................... 5-3
5-4 Plant discharge at the Tillery Hydroelectric Plant, May-October 2006-2009 ..... 5-4
5-5 Plant discharge at the Blewett Falls Hydroelectric Plant, May-October
2006-2009 ............................................................................................................ 5-6
5-6 Vertical profiles of dissolved oxygen concentrations measured at Station B2
at Lake Tillery, May through November, 2006-2009 .......................................... 5-8
5-7 Vertical profiles of dissolved oxygen concentrations measured at Station B2
at Blewett Falls Lake, May through November, 2006-2009 ............................. 5-11
6-1 Weekly mean dissolved oxygen concentrations at continuous monitor
stations in Reach 1 of the Pee Dee River below the Tillery Hydroelectric
Plant, May 1 to October 31, 2006 ........................................................................ 6-3
6-2 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant, May 1 to October 31, 2006 ................................................. 6-4
6-3 Daily averages and ranges of dissolved oxygen concentrations at Stations
TYCM1-1, TYCM2, TYCM3 and TYCM4 in Reach 1 of the Pee Dee River
below the Tillery Hydroelectric Plant, May 1 to November 30, 2006 ................ 6-6
iv
LIST OF FIGURES
(continued)
Figure Title Page No.
6-4 Dissolved oxygen concentrations on select days with no power plant
generation at Stations TYCM1-1, TYCM2, TYCM3 and TYCM4 ..................... 6-9
6-5 Weekly mean dissolved oxygen concentrations at continuous monitor
stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, May 1 to October 31, 2006 ............................................... 6-14
6-6 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, May 1 to October 31, 2006 ............................................... 6-15
6-7 Daily averages and ranges of dissolved oxygen concentrations at Stations
BFCM1, BFCMIA, BFCM2, and BFCM3 in Reach 2 of the Pee Dee River
below the Blewett Falls Hydroelectric Plant, May 1 to November 30, 2006 .... 6-17
6-8 Weekly mean temperatures at continuous monitor stations in Reach 1
of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
October 31, 2006 ................................................................................................ 6-22
6-9 Weekly mean temperatures at continuous monitor stations in Reach 2
of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2006 ................................................................................ 6-23
6-10 Weekly mean pH values at continuous monitor stations in Reach 1
of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
October 31, 2006 ................................................................................................ 6-24
6-11 Dissolved oxygen concentrations and pH values at Station TYCM2 in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant,
May 6 to 12, 2006 .............................................................................................. 6-25
6-12 Weekly mean pH values at continuous monitor stations in Reach 2
of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2006 ................................................................................ 6-26
6-13 Weekly mean specific conductance values at continuous monitor stations
in Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant,
May 1 to October 31, 2006 ................................................................................ 6-27
6-14 Weekly mean specific conductance values at continuous monitor stations
in Reach 2 of the Pee Dee River below the Blewett Falls Hydroelectric
Plant, May 1 to October 31, 2006 ...................................................................... 6-28
v
LIST OF FIGURES
(continued)
Figure Title Page No.
7-1 Weekly mean dissolved oxygen concentrations at continuous monitor
stations in Reach 1 of the Pee Dee River below the Tillery Hydroelectric
Plant, May 1 to October 31, 2007 ........................................................................ 7-3
7-2 Daily averages and ranges of dissolved oxygen concentrations at Stations
TYCM1-1, TYCM2, TYCM3 and TYCM4 in Reach 1 of the Pee Dee River
below the Tillery Hydroelectric Plant, May 1 to November 30, 2007 ................ 7-4
7-3 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant, May 1 to October 31, 2007 ................................................. 7-6
7-4 Dissolved oxygen concentrations on select days with no power plant
generation at Stations TYCM1-1, TYCM2, TYCM3 and TYCM4 ................... 7-10
7-5 Weekly mean dissolved oxygen concentrations at continuous monitor
stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, May 1 to October 31, 2007 ............................................... 7-15
7-6 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, May 1 to October 31, 2007 ............................................... 7-16
7-7 Daily averages and ranges of dissolved oxygen concentrations at
Stations BFCM1, BFCMIA, BFCM2, and BFCM3 in Reach 2 of the
Pee Dee River below the Blewett Falls Hydroelectric Plant, May 1 to
November 30, 2007 ............................................................................................ 7-18
7-8 Weekly mean temperatures at continuous monitor stations in Reach 1
of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
October 31, 2007 ................................................................................................ 7-22
7-9 Weekly mean temperatures at continuous monitor stations in Reach 2
of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2007 ................................................................................ 7-24
7-10 Weekly mean pH values at continuous monitor stations in Reach 1
of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
October 31, 2007 ................................................................................................ 7-25
vi
LIST OF FIGURES
(continued)
Figure Title Page No.
7-11 Dissolved oxygen concentrations and pH values at Station TYCM2 in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant,
May 14 to 21, 2007 ............................................................................................ 7-26
7-12 Weekly mean pH values at continuous monitor stations in Reach 2
of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2007 ................................................................................ 7-27
7-13 Weekly mean specific conductance values at continuous monitor stations
in Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant,
May 1 to October 31, 2007 ................................................................................ 7-28
7-14 Weekly mean specific conductance values at continuous monitor stations
in Reach 2 of the Pee Dee River below the Blewett Falls Hydroelectric
Plant, May 1 to October 31, 2007 ...................................................................... 7-29
8-1 Weekly mean dissolved oxygen concentrations at continuous monitor
stations in Reach 1 of the Pee Dee River below the Tillery Hydroelectric
Plant, May 1 to October 31, 2008 ........................................................................ 8-3
8-2 Daily averages and ranges of dissolved oxygen concentrations at Stations
TYCM1-1, TYCM1-2, TYCM1-3, TYCM2, TYCM3, and TYCM4 in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant,
May 1 to October 31, 2008 .................................................................................. 8-4
8-3 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant, May 1 to June 11, 2008 ....................................................... 8-7
8-4 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant, June 11, to October 31, 2008 .............................................. 8-8
8-5 Dissolved oxygen concentrations on a select days with no power plant
generation at Stations TYCM1-1, TYCM1-2, TYCM1-3 and TYCM2, May 1
to October 31, 2008 ............................................................................................ 8-11
8-6 Weekly mean dissolved oxygen concentrations at continuous monitor
stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, May 1 to October 31, 2008 ............................................... 8-14
vii
LIST OF FIGURES
(continued)
Figure Title Page No.
8-7 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, May 1 to June 11, 2008 ..................................................... 8-14
8-8 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, June 12 to October 31, 2008 ............................................. 8-15
8-9 Daily averages and ranges of dissolved oxygen concentrations at
Stations BFCM1, BFCMIA, BFCM2, BFCM2A, and BFCM3 in
Reach 2 of the Pee Dee River below the Blewett Falls Hydroelectric
Plant, May 1 to October 31, 2008 ...................................................................... 8-17
8-10 Dissolved oxygen concentrations at Stations BFCM1, BFCMIA, and
BFCM2A and power plant generation at the Blewett Falls Hydroelectric
Plant, July 12 to 14, 2008 ................................................................................... 8-20
8-11 Weekly mean temperatures at continuous monitor stations in Reach 1
of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
October 31, 2008 ................................................................................................ 8-22
8-12 Weekly mean temperatures at continuous monitor stations in Reach 2
of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2008 ................................................................................ 8-24
8-13 Weekly mean pH values at continuous monitor stations in Reach 1
of the Pee Dee River below the Tillery Hydroelectric Plant,
May 1 to October 31, 2008 ................................................................................ 8-25
8-14 Dissolved oxygen concentrations and pH values at Station TYCM2 in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant,
May 4 to 11, 2008 .............................................................................................. 8-26
8-15 Weekly mean pH values at continuous monitor stations in Reach 2
of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2008 ................................................................................ 8-27
8-16 Weekly mean specific conductance values at continuous monitor
stations in Reach 1 of the Pee Dee River below the Tillery Hydroelectric
Plant, May 1 to October 31, 2008 ...................................................................... 8-28
viii
LIST OF FIGURES
(continued)
Figure Title Page No.
8-17 Weekly mean specific conductance values at continuous monitor
stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, May 1 to October 31, 2008 ............................................... 8-29
9-1 Weekly mean dissolved oxygen concentrations at continuous monitor
stations in Reach 1 of the Pee Dee River below the Tillery Hydroelectric
Plant, May 1 to October 31, 2009 ........................................................................ 9-2
9-2 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant, May 1 to October 31, 2009 ................................................. 9-3
9-3 Daily averages and ranges of dissolved oxygen concentrations at Stations
TYCM1-1, TYCM1-2, TYCM1-3, and TYCM2 in Reach 1 of the
Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
October 31, 2009 .................................................................................................. 9-5
9-4 Dissolved oxygen concentrations on select days with no generation at
Stations TYCM1-1, TYCM1-2, TYCM1-3 and TYCM2 .................................... 9-8
9-5 Weekly mean dissolved oxygen concentrations at continuous monitor
stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, May 1 to October 31, 2009 ............................................... 9-11
9-6 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, May 1 to October 31, 2009 ............................................... 9-12
9-7 Daily averages and ranges of dissolved oxygen concentrations at Stations
BFCM1, BFCMIA and BFCM2A in Reach 2 of the Pee Dee River
below the Blewett Falls Hydroelectric Plant, May 1 to October 31, 2009 ........ 9-14
9-8 Dissolved oxygen concentrations at Stations BFCM1, BFCMIA, and
BFCM2A, and power plant generation at the Blewett Falls Hydroelectric
Plant, July 7 to July 12, 2009 ............................................................................. 9-16
9-9 Weekly mean temperatures at continuous monitor stations in Reach 1
of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
October 31, 2009 ................................................................................................ 9-24
ix
LIST OF FIGURES
(continued)
Figure Title Page No.
9-10 Weekly mean temperatures at continuous monitor stations in Reach 2
of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2009 ................................................................................ 9-25
9-11 Weekly mean pH values at continuous monitor stations in Reach 1
of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
October 31, 2009 ................................................................................................ 9-26
9-12 Dissolved oxygen concentrations and pH values at Station TYCM2 in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant,
May 1 to 6, 2009 ................................................................................................ 9-27
9-13 Weekly mean pH values at continuous monitor stations in Reach 2 of
the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2009 ................................................................................ 9-28
9-14 Weekly mean specific conductance values at continuous monitor stations
in Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant,
May 1 to October 31, 2009 ................................................................................ 9-29
9-15 Weekly mean specific conductance values at continuous monitor stations
in Reach 2 of the Pee Dee River below the Blewett Falls Hydroelectric
Plant, May 1 to October 31, 2009 ...................................................................... 9-30
x
LIST OF TABLES
Table Title Page No.
4-1 Description of Station locations used in the continuous water quality study
in Reaches 1 and 2 of the Pee Dee River below the Tillery and Blewett
Falls Hydroelectric Plants, 2006-2009 ................................................................. 4-1
4-2 Locations, GPS coordinates, water depths, and types of deployment for 11
continuous water quality monitor stations in Reaches 1 and 2 of the Pee
Dee River below the Tillery and Blewett Falls Developments ............................ 4-2
6-1 Dissolved oxygen concentration summary for Reach 1 of the Pee Dee River
below the Tillery Hydroelectric Plant, May 1 to October 31, 2006 .................... 6-2
6-2 Assessments of daily dissolved oxygen concentrations from May 1 to
October 31, 2006 at stations in Reach 1 of the Pee Dee River below the
Tillery Hydroelectric Plant compared to the North Carolina dissolved
oxygen water quality standards ............................................................................ 6-5
6-3 Days that no power was generated at the Tillery Hydroelectric Plant and
assessments of dissolved oxygen concentrations at stations in Reach 1 to
determine if they met the North Carolina water quality standards for daily
average and instantaneous dissolved oxygen concentrations during 2006........ 6-11
6-4 Dissolved oxygen concentration summary for Reach 2 of the Pee Dee River
below the Blewett Falls Hydroelectric Plant, May 1 to October 31, 2006 ........ 6-13
6-5 Assessments of daily dissolved oxygen concentrations from May 1 to
October 31, 2006 at stations in Reach 2 of the Pee Dee River below the
Blewett Falls Hydroelectric Plant compared to the North Carolina DO
water quality standards ...................................................................................... 6-16
6-6 Days that no power was generated at the Blewett Falls Hydroelectric Plant
and assessments of dissolved oxygen concentrations at stations in Reach 1
to determine if they met the North Carolina water quality standards for daily
average and instantaneous dissolved oxygen concentrations during 2006........ 6-20
6-7 Summary statistics of water quality variables from stations in Reach 1
of the Pee Dee River below the Tillery Hydroelectric Plant,
May 1 to October 31, 2006 ............................................................................... 6-21
6-8 Summary statistics of water quality variables from stations in Reach 2 of the
Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2006 ................................................................................ 6-23
xi
LIST OF TABLES
(continued)
Table Title Page No.
7-1 Dissolved oxygen concentration summary for Reach 1 of the Pee Dee River
below the Tillery Hydroelectric Plant, May 1 to October 31, 2007 .................... 7-2
7-2 Assessments of daily dissolved oxygen concentrations from May 1 to
October 31, 2007 at stations in Reach 1 of the Pee Dee River below the
Tillery Hydroelectric Plant compared to the North Carolina dissolved oxygen
water quality standards ........................................................................................ 7-8
7-3 Days that no power was generated at the Tillery Hydroelectric Plant and
assessments of dissolved oxygen concentrations at stations in Reach 1 to
determine if they met the North Carolina water quality standards for daily
average and instantaneous dissolved oxygen concentrations during 2007........ 7-12
7-4 Dissolved oxygen concentration summary for Reach 2 of the Pee Dee River
below the Blewett Falls Hydroelectric Plant, May 1 to October 31, 2007 ........ 7-14
7-5 Assessments of daily dissolved oxygen concentrations from May 1 to
October 31, 2007 at stations in Reach 2 of the Pee Dee River below the
Blewett Falls Hydroelectric Plant compared to the North Carolina dissolved
oxygen water quality standards .......................................................................... 7-17
7-6 Days that no power was generated at the Blewett Falls Hydroelectric Plant
and assessments of dissolved oxygen concentrations at stations in Reach 1 to
determine if they met the North Carolina water quality standards for daily
average and instantaneous dissolved oxygen concentrations during 2007........ 7-21
7-7 Summary statistics of water quality variables from stations in Reach 1 of the
Pee Dee River below the Tillery Hydroelectric Plant, May 1 to October 31,
2007 .................................................................................................................... 7-22
7-8 Summary statistics of water quality variables from stations in Reach 2
of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2007 ................................................................................ 7-23
8-1 Dissolved oxygen concentration summary for Reach 1 of the Pee Dee River
below the Tillery Hydroelectric Plant, May 1 to October 31, 2008 .................... 8-2
xii
LIST OF TABLES
(continued)
Table Title Page No.
8-2 Assessments of daily dissolved oxygen concentrations from May 1 to
October 31, 2008 at stations in Reach 1 of the Pee Dee River below the
Tillery Hydroelectric Plant compared to the North Carolina dissolved
oxygen water quality standards ............................................................................ 8-9
8-3 Days that no power was generated at the Tillery Hydroelectric Plant and
assessments of dissolved oxygen concentrations at stations in Reach 1 to
determine if they met the North Carolina water quality standards for daily
average and instantaneous dissolved oxygen concentrations during 2008........ 8-12
8-4 Dissolved oxygen concentration summary for Reach 2 of the Pee Dee River
below the Blewett Falls Hydroelectric Plant, May 1 to October 31, 2008 ........ 8-13
8-5 Assessments of daily dissolved oxygen concentrations from May 1 to
October 31, 2008 at stations in Reach 2 of the Pee Dee River below the
Blewett Falls Hydroelectric Plant compared to the North Carolina
dissolved oxygen water quality standards .......................................................... 8-16
8-6 Summary statistics of water quality variables from stations in Reach 1
of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
October 31, 2008 ................................................................................................ 8-21
8-7 Summary statistics of water quality variables from stations in Reach 2
of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2008 ................................................................................ 8-23
9-1 Dissolved oxygen concentration summary for Reach 1 of the Pee Dee River
below the TIllery Hydroelectric Plant, May 1 to October 31, 2009 .................... 9-1
9-2 Assessments of daily dissolved oxygen concentrations from May 1 to
October 31, 2009 at stations in Reach 1 of the Pee Dee River below the
Tillery Hydroelectric Plant compared to the North Carolina dissolved
oxygen water quality standards ............................................................................ 9-4
9-3 Days that no power was generated at the Tillery Hydroelectric Plant and
assessments of dissolved oxygen concentrations at stations in Reach 1 to
determine if they met the North Carolina water quality standards for daily
average and instantaneous dissolved oxygen concentrations during 2009.......... 9-9
X111
LIST OF TABLES
(continued)
Table Title Page No.
9-4 Dissolved oxygen concentration summary for Reach 2 of the Pee Dee River
below the Blewett Falls Hydroelectric Plant, May 1 to October 31, 2009 ........ 9-10
9-5 Assessments of daily dissolved oxygen concentrations from May 1 to
October 31, 2009 at stations in Reach 2 of the Pee Dee River below the
Blewett Falls Hydroelectric Plant compared to the North Carolina dissolved
oxygen water quality standards .......................................................................... 9-13
9-6 Comparison of dissolved oxygen summary statistics between the
2004 -2009 monitoring programs for the Tillery and the Blewett Falls
Hydroelectric Plants ........................................................................................... 9-17
9-7 Summary statistics of water quality variables from stations in Reach 1 of the
Pee Dee River below the Tillery Hydroelectric Plant, May 1 to October 31,
2009 .................................................................................................................... 9-23
9-8 Summary statistics of water quality variables from stations in Reach 2
of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2009 ................................................................................ 9-25
xiv
Acronym List
Federal/State Agencies
Advisory Council on Historic Preservation (ACHP)
Federal Aviation Administration (FAA)
Federal Energy Regulatory Commission (FERC)
National Park Service (NPS)
National Marine Fisheries Service (NMFS)
National Oceanic and Atmospheric Administration (NOAA)
National Resource Conservation Service (NRCS) formerly known as Soil Conservation Service
National Weather Service (NWS)
North Carolina Department of Environment and Natural Resources (NCDENR)
North Carolina Environmental Management Commission (NCEMC)
North Carolina Department of Natural and Economic Resources, Division of Environmental
Management (NCDEM)
North Carolina Division of Parks and Recreation (NCDPR)
North Carolina Division of Water Resources (NCDWR)
North Carolina Division of Water Quality (NCDWQ)
North Carolina Natural Heritage Program (NCNHP)
North Carolina State Historic Preservation Officer (NCSHPO)
North Carolina Wildlife Resources Commission (NCWRC)
South Carolina Department of Natural Resources (SCDNR)
South Carolina Department of Health and Environmental Control (SCDHEC)
State Historic Preservation Office (SHPO)
U. S. Army Corps of Engineers (ACOE)
U. S. Department of Interior (DOI)
U. S. Environmental Protection Agency (USEPA)
U.S. Fish and Wildlife Service (USFWS)
U. S. Geological Survey (USGS)
U. S. Department of Agriculture (USDA)
U.S. Forest Service (USFS)
Other Entities
Alcoa Power Generating, Inc., Yadkin Division (APGI)
Progress Energy (Progress)
University of North Carolina at Chapel Hill (UNCCH)
Facilities/Places
Yadkin - Pee Dee River Project (entire two-development project including both powerhouses,
dams and impoundments)
Blewett Falls Development (when referring to dam, powerhouse and impoundment)
Blewett Falls Dam (when referring to the structure)
Blewett Falls Hydroelectric Plant (when referring to the powerhouse)
Blewett Falls Lake (when referring to the impoundment)
Tillery Development (when referring to dam, powerhouse and impoundment)
Tillery Dam (when referring to the structure)
Tillery Hydroelectric Plant (when referring to the powerhouse)
Lake Tillery (when referring to the impoundment)
AL- I
Acronym List
Acronym List
(continued)
Documents
401 Water Quality Certification (401 WQC)
Draft Environmental Assessment (DEA)
Environmental Assessment (EA)
Environmental Impact Statement (EIS)
Final Environmental Assessment (FEA)
Initial Consultation Document (ICD)
Memorandum of Agreement (MOA)
National Wetland Inventory (NWI)
Notice of Intent (NOI)
Notice of Proposed Rulemaking (NOPR)
Preliminary Draft Environmental Assessment (PDEA)
Programmatic Agreement (PA)
Scoping Document (SD)
Shoreline Management Plan (SMP)
Laws/Regulations
Clean Water Act (CWA)
Code of Federal Regulations (CFR)
Electric Consumers Protection Act (ECPA)
Endangered Species Act (ESA)
Federal Power Act (FPA)
Fish and Wildlife Coordination Act (FWCA)
National Environmental Policy Act (NEPA)
National Historic Preservation Act (NHPA)
Terminology
Alternative Relicensing Process (ALP)
Cubic feet per second (cfs)
Degrees Celsius (°C)
Degrees Fahrenheit (°F)
Dissolved oxygen (DO)
Feet (ft)
Gallons per day (gpd)
Geographic Information Systems (GIS)
Gigawatt Hour (GWh)
Global Positioning System (GPS)
Grams (g)
Horsepower (hp)
Kilogram (kg)
Kilowatts (kW)
Kilowatt-hours (kWh)
Mean Sea Level (msl)
Megawatt (MW)
AL-2
Acronym List
Acronym List
(continued)
Terminology
Megawatt-hours (MWh)
Meter (m)
Micrograms per liter (µg/L)
Milligrams per liter (mg/L)
Millimeter (mm)
Million gallons per day (mgd)
National Geodetic Vertical Datum (NGVD)
National Wetlands Inventory (NWI)
Non-governmental Organizations (NGOs)
Ounces (oz.)
Outstanding Remarkable Value (ORV)
Parts per billion (ppb)
Parts per million (ppm)
Pounds (lbs.)
Power Factor (p.f.)
Probable Maximum Flood (PMF)
Project Inflow Design Flood (IDF)
Rare, Threatened, and Endangered Species (RTE)
Ready for Environmental Assessment (REA)
Resource Work Groups (RWG)
Revolutions per Minute (rpm)
Rights-of-Way (ROW)
Stakeholders (federal and state resource agencies, NGOs, and other interested parties)
Volts (V)
AL-3
Executive Summary
This monitoring program assessed the spatial and temporal patterns of dissolved oxygen (DO)
concentrations in the Pee Dee River downstream of the Tillery and Blewett Falls hydroelectric
plants using in-situ continuous monitoring instruments during May through October, 2006-2009.
The 2006-2009 monitoring program methods were essentially the same as the program
conducted during 2004 and 2005, as part of the environmental relicensing studies. One
exception was the 2008 program included two additional sampling stations at Tillery along the
NC Highway 731 Bridge (Stations TYCM1-2 and TYCM1-3) and one additional station at
Blewett Falls (Station BFCM2A). Sampling began at these new additional stations on June 11,
2008 at Blewett Falls and on June 12, 2008 at Tillery. Four sampling locations from previous
studies were dropped during this time period (Stations TYCM3, TYCM4, BFCM2, and
BFCM3). These new sampling locations were approved by the North Carolina Division of Water
Quality (NCDWQ).
The 2006-2009 monitoring program evaluated the longitudinal (upstream to downstream)
differences in DO concentrations in the Pee Dee River below both power plants, and the
latitudinal (east bank to west bank) differences (2008 and 2009) immediately below the Tillery
Plant. Monitoring was conducted from May-October to capture the seasonal period of
hypolimnetic stratification in both project reservoirs. The study also evaluated spatial and
temporal patterns of temperature, pH, and specific conductance below each power plant.
Four continuous water quality monitors were placed in the Pee Dee River below each power
plant within sections designated by the NCDWQ as impaired for DO under Section 303(d) of the
Clean Water Act. The NCDWQ has listed the 4.9 mile reach from the Tillery Dam to the Rocky
River confluence as impaired (NCDWQ 2010). These low DO concentrations occur seasonally
during the warmer months when the Project reservoirs stratify and the deeper reservoir waters
have low DO concentrations.
Measured DO concentrations in the Pee Dee River from the Tillery Plant to the Turkey Top
Creek confluence were below the North Carolina water quality standards for instantaneous
(4.0 mg/L) and daily average (5.0 mg/L) DO concentrations on some days from May through
early October of each monitored year. These periods corresponded with low DO levels in the
deeper water of Lake Tillery and the low DO concentrations in this water periodically released
from the Tillery Plant. Dissolved oxygen concentrations increased in the river below the Tillery
Plant after DO de-stratification in Lake Tillery during October. Dissolved oxygen
concentrations were also below one or both North Carolina water quality standards on days that
the power plant did not generate power. Dissolved oxygen concentrations immediately below
the Tillery Plant were more often below one or both water quality standards on non-power
generation days than at other downstream stations.
Dissolved oxygen concentrations in the river generally increased with increased distance from
the Tillery Plant due to re-aeration in the river channel and tributary inflow. Dissolved oxygen
concentrations were affected by natural diel cycles of algal photosynthesis and respiration as
well as power plant operations. Dissolved oxygen concentrations usually increased during
daylight hours and decreased at night as a result of algal photosynthesis and respiration. Tillery
Plant operations were most noticeable when power generation occurred after DO concentrations
ES-1
Executive Summary
began to rise during the morning hours. Dissolved oxygen concentrations in the river would
decrease when hypolimnetic water with low DO concentrations was released from Lake Tillery.
This change in DO concentrations was most evident 0.2 miles downstream of the Tillery Plant.
Dissolved oxygen concentrations in the Pee Dee River below the Blewett Falls Plant were below
one or both North Carolina water quality standards on some days from mid-May to early
October.
Dissolved oxygen concentrations did not consistently increase throughout Reach 2 with
increased distance from the Blewett Falls Plant. Both North Carolina water quality standards
were met more often at Station BFCM3, the lowermost monitoring station, than at any other
Station within Reach 2. The number of days not meeting the water quality standards for DO
concentrations (62, 72, 88 and 121 days from 2004-2007 respectively) and the percentage of DO
concentrations less than 5.0 mg/L (24.4%, 34.3%, 35.1% and 45.4% from 2004-2007
respectively) were the greatest at Station BFCM2, located approximately 3.4 miles downstream
of the power plant.
Filamentous algae that accumulated on the continuous monitor at Station BFCM3 during late
July and August contributed to periods of low DO concentrations and fluctuations in daily pH
values at that station. The accumulated algae caused wide daily fluctuations in DO
concentrations and affected the continuous monitor's ability to measure DO concentrations
accurately. There appeared to be a source of nutrients entering the river upstream of this
continuous DO monitor that contributed to the profuse algal growth.
The period that DO concentrations did not meet the water quality standards occurred for a longer
period during 2007 in both Reaches 1 and 2 (i.e., mid May through mid October) compared to
the period documented in other monitored years (i.e., late May through early September
2004-2009). This temporal difference was attributable to climatological differences, reservoir
stratification patterns, and frequency of plant generation. The year 2007 was marked by a warm,
dry spring and summer. However, in all years, reservoir destratification and DO levels above the
state water quality standards occurred by early to late September to mid October depending upon
the annual climatological conditions, reservoir inflow, and station location. Spatial trends in DO
concentrations in the two river reaches were similar during all monitored years.
ES-2
Section I - Introduction
Progress Energy is currently relicensing the Tillery and Blewett Falls Developments (i.e.,
Yadkin-Pee Dee River Hydroelectric Project No. 2206) with the Federal Regulatory Commission
(FERC). As part of the relicensing process, Progress Energy established Resource Work Groups
during May 2003 to identify environmental issues associated with Project operations and develop
study plans specific to Project lands and associated lakes and tailwaters. The Water Resources
Work Group (RWG) identified the need for additional water quality studies of the Project
reservoirs and tailwaters (i.e., Progress Energy 2004, Water RWG Issue Nos. 7 and 8, "Lake
Tillery and Blewett Falls Lakes and Tailwaters Water Quality"). The purpose of these studies
was to evaluate the water quality in the Project reservoirs and the Pee Dee River below the
Tillery and Blewett Falls Hydroelectric Plants. Specifically, these water quality studies
addressed: (1) meeting state water quality standards and supporting designated uses in the
reservoirs and tailwaters; (2) evaluating the Project operation effects on the water quality in both
reservoirs and downstream tailwaters; (3) cumulative effects of nutrient and sediment loading on
reservoirs and tailwaters; and (4) water quality effects of Rocky River inflow.
Three studies were conducted during 2004 to address the water quality issues: (1) a monthly
sampling program at the Tillery and Blewett Falls Developments to characterize the existing
water quality conditions in the Project reservoirs and downstream tailwaters, including the
effects of the Rocky River tributary inflow (Progress Energy 2006a); (2) an intensive assessment
of the spatial and temporal patterns of temperature and DO concentrations in the Pee Dee River
downstream of each power plant (Progress Energy 2005a); and (3) a continuous monitoring
study of DO (Progress Energy 2005b) from May through November in the upper, mid, and lower
reaches of the 303(d) impaired river reaches below each hydroelectric dam, as designated by the
NCDWQ (2006). These studies also characterized the water quality of the Project tailwaters
with and without power plant generation.
Progress Energy filed the results of the 2004 water quality studies in its Final License
Application (FLA) with FERC during April 2006 (Progress Energy 2006b).
In May 2007, Progress Energy submitted an application to the NCDWQ for a 401 Water Quality
Certificate (WQC) for the Project. The WQC application also contained the DO Enhancement
Plan and schedule for meeting water quality standards at each power plant. The NCDWQ issued
the 401 WQC for the project during February 2008 which was modified and subsequently
reissued during September 2008. The 401 WQC specified the timeline for compliance for
meeting the state water quality standards at the Project by the end of 2011.
To meet the state water quality standards, Progress Energy began an evaluation program to
assess various DO enhancement technologies, which began in the summer of 2005 and continued
through 2010. The goal of this evaluation program was to determine the least cost and most
technologically suitable method for each power plant to meet the state water quality standards.
Turbine draft tube venting is planned for the Blewett Falls plant while venting and reservoir
oxygen enhancement is planned for the Tillery Plant. Implementation of the chosen DO
enhancement technologies is currently underway at both power plants.
1-1
Section 1 Introduction
As part of the filed DO Enhancement Plan, Progress Energy also proposed to continue the
continuous monitoring of DO and temperature through 2010, on an interim basis, until
permanent temperature and DO compliance monitoring locations could be established at each
development. The continuous monitoring program followed the same methods used in the 2004
relicensing study and a voluntary 2005 monitoring program (Progress Energy 2005b, 2006c).
This report provides the interim continuous water quality monitoring results in the river reaches
below the Tillery and Blewett Falls Hydroelectric Plants from May 1 to October 31, 2006-2009.
This report marks the sixth year of monitoring (2004-2009).
The NCDWQ has previously listed sections of the Pee Dee River below each hydroelectric plant
as impaired for aquatic life due to low DO concentrations from the hydropower operations
(NCDWQ 2006). Currently, the 4.9-mile section of the Pee Dee River from Tillery Dam to the
confluence of the Rocky River is listed as impaired due to low DO concentrations
(NCDWQ 2010). The Blewett Falls section was removed from the 303(d) list by the NCDWQ
during 2010 (NCDWQ 2010). The Pee Dee River from Tillery Dam to Blewett Falls Lake has a
Class WS-V&B water quality classification and the Pee Dee River from Blewett Falls Lake to
Hitchcock Creek has a Class C classification (NCDWQ 2007). Class WS-V&B waters are
designated as drinking water supplies and primary recreation while Class C are designated for
propagation of aquatic life and secondary recreational uses.
1-2
Section 2 - Study Objectives
The objective of this study was to assess the spatial and temporal patterns of DO concentrations
in the Pee Dee River downstream of the Tillery and Blewett Falls Hydroelectric Plants using
in-situ continuous monitoring instruments from May through October, 2006-2009. The study
evaluated the longitudinal (upstream to downstream) and latitudinal (east bank to west bank)
differences in the DO regime in the Pee Dee River with power plant operations over a seasonal
period of hypolimnetic stratification and de-stratification of the Project reservoirs. Monitors
were placed below each power plant and within the river sections designated or previously
designated by the NCDWQ as impaired due to low DO concentrations under Section 303(d) of
the Clean Water Act. A secondary study objective was to continuously monitor temperature, pH,
and specific conductance.
2-1
Section 3 - Site Description
3.1 Reach 1 - Pee Dee River Below the Tillery Development
The study area for Reach 1 was a 15.3-mile reach of the Pee Dee River in south-central North
Carolina located immediately below the Tillery Development to the mouth of Turkey Top Creek
(Figure 3-1). Reach 1 immediately below the Tillery Development is generally shallow with
runs, shoals, large substrate, and bedrock outcroppings. River conditions are similar downstream
until the Rocky River confluence, approximately 5 miles downstream of the Tillery Dam. From
the Rocky River confluence to the downstream extent of Reach 1, pools and deep runs with
smaller substrate such as sand, silt, and organic detritus become more common.
Several tributaries enter into Reach 1 (Figure 3-1). Clarks Creek enters into Reach 1 from the
east just upstream of the N.C. Highway 731 Bridge. The Town of Mount Gilead's Wastewater
Treatment Plant discharges into Clarks Creek. The Rocky River, the largest tributary in the
reach, converges with the Pee Dee River from the west, approximately five miles below the
Tillery Dam. The Rocky River watershed includes several urban communities such as
Mooresville, Kannapolis, Concord, Huntersville, and eastern portions of Charlotte. Urban as well
as agricultural nonpoint sources of runoff and point sources of discharge have contributed to
degraded water quality in the Rocky River. Turbidity and fecal coliform have been noted as
water quality parameters of concern in sections of the Rocky River by the NCDWQ and the
Yadkin-Pee Dee River Basin Association (NCDWQ 2008, 2010). These two parameters were in
excess of applicable state water quality standards in more than 10 percent of samples collected
during the assessment period. Brown Creek flows through the Pee Dee National Wildlife Refuge
and enters into Reach 1 from the west approximately one mile upstream of the N.C. Highway
109 Bridge. Brown Creek from the mouth of Lick Creek to the confluence of the Pee Dee River
has an overall impaired use due to impaired biological integrity and low DO concentrations
(NCDWQ 2010). Two small tributaries, Cedar Creek and Turkey Top Creek, enter into Reach 1
below the N.C. Highway 109 Bridge.
3.2 Reach 2 - Pee Dee River Below the Blewett Falls Development
The study area for Reach 2 was a 7.5-mile reach of the Pee Dee River in south-central North
Carolina from below the Blewett Falls Development to 1.2 miles downstream of the Hitchcock
Creek confluence (Figure 3-2). Reach 2 has shoals, riffles, runs, and pools with a wide range of
substrate sizes and bedrock outcroppings. River conditions are similar throughout Reach 2.
Shoals are intermittently located within the reach, which indicate substantial drops in river
channel gradient.
Four named tributaries enter into Reach 2 of the Pee Dee River (Figure 3-2). Cartledge Creek
enters into the Pee Dee River from the east approximately two miles below the Blewett Falls
Dam. McCoy Creek enters from the west about a half mile upstream of the U. S. Highway 74
Bridge. Island Creek enters from the west below the U. S. Highway 74 Bridge. Hitchcock
Creek, the largest tributary in the reach, enters into the Pee Dee River from the east at the lower
extent of Reach 2.
3-1
Section 3
Site Description
Ti
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i
Figure 3-1 Map of the Tillery Development and Reach 1 of the Pee Dee River showing
continuous water quality monitoring stations.
3-2
Section 3
Blewett Falls Hydroelectric Development
Little River

Mountain
Creek
3
- RICHMOND
ANSON COUNTY
COUNTY

Blewett Falls Lake
Buffalo Cartledge
BIe1

Falls Dam

Site Description
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Figure 3-2 Map of the Blewett Falls Development and Reach 2 of the Pee Dee River
showing continuous water quality monitoring stations.
3-3
Section 4 - Methods
4.1 Continuous Monitor Locations
Continuous monitor stations were located in the upper, middle, and lower sections of the
monitored reaches below the Tillery and Blewett Falls Developments (Table 4-1 and Figures 3-1
and 3-2). In Reach 2, the lowermost Station (Station BFCM3) was located 1.2 miles downstream
of the Hitchcock Creek confluence. Prior to selecting the continuous monitor stations in 2004,
lateral and vertical water quality measurements were made at cross-channel transects to
determine any significant spatial differences in DO concentrations across the river channel
(Progress Energy 2005b). Station locations were chosen to be representative of the river channel
area with the lowest DO concentrations. These same station locations were used in the
2004-2009 continuous monitoring programs. On June 11, 2008, Stations TYCM3, TYCM4,
BFCM2 and BFCM3 were dropped from the monitoring program. Stations TYCM1-2,
TYCM1-3, and BFCM2A were subsequently added to the monitoring program on this same date
to better assess spatial DO concentrations in the immediate tail waters. The NCDWQ approved
these modifications to the monitoring program.
Table 4-1 Description of Station locations used in the continuous water quality study in
Reaches 1 and 2 of the Pee Dee River below the Tillery and Blewett Falls
Hydroelectric Plants, 2006-2009.
Transect Location Description (approximate river miles below each power plant dam)
Reach 1 Tillery Hydroelectric Plant
TYCMI-1 East Bank of N.C. Highway 731 Bridge (0.4 mile)
TYCMI-2 Mid-Channel of N.C. Highway 731 Bridge (0.4 mile)
TYCMI-3 West Bank of N.C. Highway 731 Bridge (0.4 mile)
TYCM2 Above Rocky River confluence (4.6 miles)
TYCM3 N.C. Highway 109 Bridge (12.2 miles)
TYCM4 Confluence of Turkey Top Creek above Blewett Falls Lake (15.3 miles)
Reach 2 Blewett Falls Hydroelectric Plant
BFCMI Power Plant Tailrace Buoy Line (0.1 mile)
BFCMIA Below Peninsula Separating Power Plant Tailrace and Dam (0.7 mile)
BFCM2 U.S. Highway 74 Bridge (3.5 miles)
BFCM2A Below Cartledge Creek confluence (2.1 miles)
BFCM3 Below Hitchcock Creek confluence (7.1 miles)
Selection of the continuous monitor stations was based on the results of the cross-channel DO
measurements, suitable water depth, access to monitors, availability of permanent structures for
anchoring monitors, and protection from floating debris and vandalism. In some instances,
continuous monitors were cabled to bridge pilings, while other monitors were held in place by
anchors placed on the river bottom (Table 4-2). The location of the continuous monitor at
Station TYCM2 was changed during 2005. It was moved to the east side of the river channel
because previous studies showed that DO concentrations were often lower on the east side.
Because the river is very shallow in this sub-reach with few deep areas, the monitor was also
4-1
Section 4
Methods
moved upstream approximately 100 m. The continuous monitor at Station BFCM2 was moved
approximately 0.5 m higher in the water column.
Table 4-2 Locations, GPS coordinates, water depths, and types of deployment for 11
continuous water qua lity monitor stations in Rea ches 1 and 2 of the Pee Dee
River below the Tillery and Blewett Fa lls Develop ments.

GPS Water
Station Location Coordinates Depth Type of Deployment

TYCMI-1 N.C. Highway 731 Bridge 3512' 03.48" N 0.4-2.0 m In a Stationary, vertical PVC
piling near the east shore 8003' 41.41" W pipe cabled to the bridge piling
TYCMI-2+ N.C. Highway 731 Bridge 35° 12' 02.52" N 0.4-2.Om In a Stationary, vertical PVC
piling near the mid-channel 80° 03' 41.84" W pipe cabled to the bridge piling
TYCMI-3+ N.C. Highway 731 Bridge 35° 12' 01.45" N 0.4-2.Om In a Stationary, vertical PVC
Piling near the west channel 80° 03' 45.35" W pipe cabled to the bridge piling
TYCM2 In a shallow run near the east 35o 09' 01.60" N 0.4-1.5 m Suspended in water column by
bank 1 km upstream of the 80o 04' 17.12" W floats and anchored with a heavy
Rocky River confluence weight
TYCM3¶ N.C. Highway 109 Bridge 35o 05'08.1 F N 1.5-2.5 m Tethered to the bridge piling and
piling near the east shore 79o 59' 55.88" W anchored on the river bottom
TYCM4¶ In a mid-channel pool just 35o 06' 59.63" N 2.0-3.0 m Suspended in water column by
below the confluence of 79o 57'07.18" W floats and anchored with a heavy
Turkey Top Creek weight
BFCMI Midway on the safety buoy 34o 59'00.24" N 2.0-3.5 m Tethered to the safety buoy line
line in the power plant 79o 52' 34.00" W cable with an anchor on the river
tailrace bottom
BFCMIA In a shallow run downstream 34o 58' 59.92" N 1.0-2.0 m Suspended in water column by
of the peninsula separating 79o 52' 12.77" W floats and anchored with a heavy
the tailrace and dam weight
BFCM2 U.S. Highway 74 Bridge 34o 56' 45.21" N 2.5-3.5 m Suspended by cable from a
piling in mid-channel 79o 52' 13.73" W horizontal bridge support and
anchored on the river bottom
BFCM2A+ In a pool just below a rock 34° 58' 04.30" N 2.5-3.5 m Suspended in water column by
shoal below the confluence of 79° 51' 58.63" W floats and anchored with a heavy
Cartledge Creek. weight
BFCM3¶ In a pool 1.9 km downstream 34o 53' 55.35" N 3.0-4.0 m Suspended in water column by
of the confluence of 79o 51'01.63" W floats and anchored with a heavy
Hitchcock Creek weight
+ Removed from monitoring program in June 2008 per NCDWQ approval.
¶ Added to monitoring program in June 2008 per NCD WQ approval.
4-2
Section 4
4.2 Continuous Monitor Deployment
Methods
YSI9 600XLM continuous monitors were selected to monitor water quality in the 2004-2009
monitoring studies (YSI 2003). All continuous monitors were placed in a sleeve section of two-
inch diameter PVC pipe for protection. Holes were drilled in the lower end of the PVC pipe to
allow water to move freely around the continuous monitor probes. Five different deployment
techniques were used for the continuous monitors depending on the station location (Table 4-2).
Continuous monitors were anchored to permanent structures such as bridge pilings when
available. Otherwise, continuous monitors were anchored to the river bottom by a heavy weight
and suspended in the water column beneath foam floats. Continuous monitors at stations
TYCM1-1, TYCM1-2, TYCM1-3, TYCM3, and BFCM2 maintained stationary positions and
were capable of recording accurate depth data.
Continuous monitors were deployed below the Tillery and Blewett Falls developments in late
April and began logging data on May 1. Continuous monitors were programmed to record
temperature, DO, pH, specific conductance, and depth at 15-minute intervals. During 2004, a
28-second warm up period was used for the DO probes. A 40-second warm up period was used
for the DO probes in 2005-2009. All continuous monitors were removed from the river
October 31 of each year after the 2004 monitoring year.
4.3 Continuous Monitor Service and Calibration
Continuous monitors were calibrated in the laboratory prior to deployment. Continuous
monitors were field-checked/calibrated against known pH and conductivity standards during
routine field servicing. Dissolved oxygen membranes were changed during service, and DO was
air-calibrated prior to each deployment. Additionally, continuous monitors were cleaned and
data were uploaded during service. Temperature probes was checked when continuous monitors
were returned to the laboratory for service, cleaning, and calibration during the study.
The continuous monitors were scheduled to be serviced and calibrated biweekly and rotated
among stations during the May through October monitoring period. Rotating continuous
monitors reduced the time that data were not recorded and helped determine if any data
anomalies were due to station environmental conditions or continuous monitor performance.
Continuous monitors that were not deployed in the field were returned to the laboratory for
service, cleaning, and calibration. All YSI® 600XLM continuous monitors had a unique
identification number which permitted instrument performance tracking during the study.
4.4 Data Validation and Review
Each YSI*) 600XLM continuous monitor was compared against a laboratory- and field-calibrated
YSI9 Model 650 multi-parameter instrument during the field servicing. All continuous monitor
data were combined for each station and then reviewed and edited to determine if any data
needed to be omitted due to equipment performance issues. Water quality data were recorded in
the field and retained for analysis for 93.5-100 percent of the time that continuous monitors were
deployed (Tables A-1-A-4). Data were omitted if there was a problem with one or more of the
YSIR 600XLM continuous monitor probes based on the instrument-to-instrument comparisons.
4-3
Section 4 Methods
Periods when data were not logged at each station and the reason(s) why the continuous monitor
malfunctioned or why recorded data were omitted after review are listed in Tables A-5-A-7.
4.5 Quality Assurance and Quality Control
All continuous monitoring data were collected in accordance with Progress Energy's Quality
Assurance/Quality Control (QA/QC) Program (Progress Energy 2007a, 2007b and 2008). In
addition, Progress Energy filed a draft Quality Assurance Project Plan (QAPP) with the
NCDWQ (Progress Energy 2007c) in its 401 Water Quality Certificate application, dated May
11, 2007. The QAPP specifies the QA/QC framework that was followed during the conduct of
these studies.
Progress Energy is certified by the NCDWQ and the South Carolina Department of Health and
Environmental Control to collect water quality and biological samples through Standard
Operating Procedures. Specific procedures for instrument calibration and water quality sampling,
including sample handling and chain-of-custody, are detailed in Progress Energy's QA/QC
Program and the QAPP.
4-4
Section 5 - Environmental and Reservoir Conditions
5.1 Environmental Conditions
5.1.1 Climatological Conditions
The long-term annual precipitation average at Wadesboro, North Carolina (COOP Station
318964) for the 1938-2009 period was 117.0 cm. Precipitation during 2007 and 2009 was less
than the long term annual average (88.6 cm and 116.1), whereas 2006 and 2008 exceeded the
long term annual average (125.1cm and 130.6cm). The drought of 2007 persisted into June
2008, but precipitation levels from July-September 2008 exceeded the 71 year average
(Figure 5-1), breaking the drought. Strong summer thunderstorms and two tropical storms
(Fay and Hannah) were responsible for high rain fall totals in July, August, and September 2008
(Figure 5-1). Monthly precipitation totals ranged from 0.7 cm (November 2007) to 26.0 cm
(August 2008). Based on monthly totals, 2008 was the wettest year during this time period.
30
25
_ 20
E
U
C
°; 15
Q-
U
N
L
a
10
5
0

i
c
,,A e??JaKk P??Jy? Keeec O?10' , c 0 `?1
? e c, oe ee
O
411
Month
1 2006 $2007 (2008 2009 Historical Average
Figure 5-1 Comparison of monthly precipitation totals during the 2006-2009 period to
the 71-year monthly averages for the period 1938 to 2009. (Data Source:
Wadesboro, North Carolina COOP Station 318964).
5-1
Section 5 Environmental and Reservoir Conditions
Mean monthly air temperatures were generally below the 1938-2009 long-term average for the
majority of 2007-2008 (Figure 5-2). Monthly average air temperatures ranged from 15.1 °C
(October 2008) to 28.2°C (August 2007) during the May through October monitoring period
2006-2009 (Figure 5-2). Based on the long-term monthly averages, 2007, 2008, and 2009 were
0.3, 0.5 and 0.1°C cooler, respectively, than the 71 year average. Based on the long-term
monthly averages, 2006 was 0.4°C warmer than the 71 year average.
30.0
20.0
u
w
L
L
Q
E
~ 10.0
0.0
P IP ?o Oe
Month
1 2006 42007 12008 2009 Historical Average
Figure 5-2 Comparison of mean monthly air temperatures during the 2006-2009 period
with the 71-year monthly averages of air temperatures for the period 1938 to
2009 (Source: Wadesboro, North Carolina COOP Station 318964).
5.1.2 River Flow Conditions
The stream flow gage for the Rocky River at the N.C. Highway 52 Bridge (USGS 02126000)
reflected local and watershed precipitation events (Figure 5-3). The stream flow gage for the Pee
Dee River at the U.S. Highway 74 Bridge (USGS 02129000) reflected watershed precipitation
events as well as Blewett Falls Hydroelectric Plant operations. Daily mean stream flow for the
Rocky River ranged from 51 cfs (August 25, 2008) to 39,300 cfs (November 22-23, 2006), and
averaged 915 cfs for the 2006-2009 period. Daily mean stream flow at the U.S. Highway 74
Bridge ranged from 268 (September 11, 2006) to 106,000 cfs (November 23, 2006), and
averaged 5,583 cfs for the 2006-2009 period.
5-2
Section 5
50000
v 40000
3
0
LL 30000
W
bb
N
N 20000
a
10000
0
Environmental and Reservoir Conditions
Rocky River at the N.C. Highway 52 Bridge (USGS 02126000)
0
>a?J?Kk
F

A
owe >pJ Jy? `oet sec sec sec
> PJao he??eco O`?o ?oett` oeGe?
Month
2006 2007 2008 2009
Pee Dee River at the U.S. Highway 74 Bridge (USGS 02129000)
120,000
100,000
U
0 80,000
LL
60,000
L
Q 40,000
0 20,000
Figure 5-3
>a°J,,A e?iJ,,A OPo?ec
Q P ?eQ?' ?o Oe
Month
2006 2007 2008 2009
0
Daily mean stream flow for the Rocky River at the N.C. Highway 52 Bridge
and the Pee Dee River at the U.S. Highway 74 Bridge, 2006-2009.
5-3
Section 5
Environmental and Reservoir Conditions
Power plant discharge never exceeded 20,000 cfs below the Tillery Hydroelectric Plant during
2006-2009 (Figure 5-4). Water spilling over the dam did not occur during the 2006-2008 period.
From May through October 2006-2009, more power generated flows occurred during May and
June than any other months, while the least flow occurred during October. Plant generation flows
in 2009 were twice the amount that occurred in 2007 and 2008. The number of days from May 1
to October 31 without any power generation during a 24-hour period at the Tillery Hydroelectric
Plant totaled 22 days in 2006, 26 days in 2007, 6 days in 2008, and 7 days in 2009.
2006
21000
18000
15000
UU
ww 12000
L
M
N 9000
0
6000
3000
0
Month
2007
21000
18000
N 15000
UU
w 12000
ao
L
M 9000
U
N
6000
3000
0
Figure 5-4
May June July August September October
Month
Plant discharge (cfs) at the Tillery Hydroelectric Plant, May-October
2006-2009.
5-4
May June July August September October
Section 5
2008
21000
18000
15000
UU
w 12000
ao
L
9000
U
V1
6000
3000
0
2009
21000
18000
15000
4-
U
W 12000
bb
L
M 9000
U
N
0 6000
3000
0
Month
Figure 5-4 (continued).
Environmental and Reservoir Conditions
During the 2006-2009 monitoring period, plant discharge estimates never exceeded 10,000 cfs
below the Blewett Falls Hydroelectric Plant (Figure 5-5). Power generation in May was greater
than any other month, while the least amount of power generation occurred during October. Plant
generation during 2009 was greater than 2007 and 2008 discharge totals by over 5.3 M cfs. The
number of days from May 1 to October 31 without any power generation during a 24-hour period
at the Blewett Falls Hydroelectric Plant totaled 30 days in 2006, and 9 days in 2007. The Blewett
Falls Plant released flows for more than 24 consecutive hours on several occasions from May
through October.
5-5
May June July August September October
Month
May June July August September October
Section 5
2006
10000
8000
U
U 6000
ao
L
M
U
N 4000
0
2000
0
2007
10000
8000
6000
w
ao
L
M
N 4000
0
2000
0
Environmental and Reservoir Conditions
May June July August September October
Month
Figure 5-5 Plant discharge (cfs) at the Blewett Falls Hydroelectric Plant, May-October
2006-2009.
5-6
May June July August September October
Month
Section 5
2008
10000
8000
6000
w
ao
L
M
U 4000
W
0
2000
0
Environmental and Reservoir Conditions
May June July August September October
Month
2009
10000
8000
6000
w
ao
L
M
U 4000
W
0
2000
0
May June July August September October
Month
Figure 5-5 (continued).
5.2 Dissolved Oxygen in Project Reservoirs
5.2.1 Lake Tillery
The intake structure at the Tillery Hydroelectric Plant extends from 12 to 19 m below the surface
of Lake Tillery at the normal maximum operating elevation (277.3 ft)'. Vertical profiles of DO
concentrations were taken at least once a month at Station B2 on Lake Tillery near the intake
structure (Figures 3-1 and 5-6). In May of most monitored years, Lake Tillery was well-mixed
and DO concentrations were similar throughout the water column (Figure 5-6). In June of most
monitored years stratification (i.e., change of > 1 mg/L per meter of depth) occurred at or below
four meters (Figure 5-6). Dissolved oxygen concentrations were stratified in the lake during
July, August, and part of September 2006-2009, and DO concentrations were less than 5.0 mg/L
' Unless otherwise noted, all elevations are NAVD 88 datum. The NAVD 88 datum is 0.9 feet lower than the 1929
NGVD datum.
5-7
Section 5 Environmental and Reservoir Conditions
below 7 m. Dissolved oxygen concentrations at the intake depth (12-19 m) were < 1.0 mg/L
from July-August, 2007-2009. Dissolved oxygen stratification disappeared during mid-late
September, as DO concentrations were above 5 mg/L and similar throughout the water column.
The period of DO stratification in 2009 was less than that for the 2006-2008 periods.
2006
Dissolved Oxygen (mg/L)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0
0.0
2.0
4.0
6.0
8.0
E
MW 10.0
Q.
w -
12.0
14.0
16.0
18.0
20.0
-+--5/31/2006 -9--6/21/2006 7/20/2006 -0-8/23/2006
9/21/2006 10/18/2006 11/21/2006
Figure 5-6
Vertical profiles of dissolved oxygen concentrations measured at Station B2
at Lake Tillery, May through November, 2006-2009.
5-8
Section 5
2007
Dissolved Oxygen (mg/L)
0.0 2.0 4.0 6.0
0 - -
2
4
6
8
10
Q.
w
0 12
14
16
18
20
Environmental and Reservoir Conditions
8.0 10.0 12.0
X5/10/2007 --W-6/7/2007 7/3/2007 --X-8/9/2007
9/7/2007 10/3/2007 10/30/2007 11/14/200
2008
Dissolved Oxygen (mg/L)
0.0 2.0 4.0 6.0 8.0 10.0
0.0
2.0
4.0
6.0
_ 8.0
10.0
t
12.0
0
14.0
16.0
18.0
20.0
22.0
X5/14/2008 f 6/12/2008 7/8/2008 --X-8/9/2008
9/10/2008 10/8/2008 10/31/2008
12.0
Figure 5-6 (continued).
5-9
Section 5
2009
0.0
2.0
4.0
6.0
Environmental and Reservoir Conditions
Dissolved Oxygen (mg/L)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0
8.0
10.0
Q.
w
0 12.0
14.0
16.0
18.0
20.0
--$--5/14/2009 --W-6/16/2009 7/17/2009 8/14/2009
-0-9/9/2009 10/8/2009 11/6/2009
Figure 5-6 (continued).
5.2.2 Blewett Falls Lake
The intake structure at the Blewett Falls Hydroelectric Plant extends from approximately 6 to
10 m below the lake surface at the normal maximum operating elevation (177.2 ft)'. Vertical
profiles of temperature and DO concentrations were taken at least once a month at Station B2
located near the Blewett Falls Dam. This station is adjacent to the power plant intake canal
(Figures 3-5 and 5-7). Station B2 was usually 7 to 9 m deep depending upon lake level
elevation. Dissolved oxygen concentrations were > 5.0 mg/L throughout the water column
during May and stratified in by mid June during the 2006-2008 period. Dissolved oxygen
stratification did not occur until mid to late July in 2009. Dissolved oxygen concentrations at the
intake depth (6-10 m) were < 2.0 mg/L from July to early September during the 2006-2008
period. From mid-late September-November 2006-2009, DO concentrations were above
5.0 mg/L throughout the water column (Figure 5-7). The duration of DO stratification in 2009
was less than that from 2006 to 2008.
5-10
Section 5 Environmental and Reservoir Conditions
2006
Dissolved Oxygen (mg/1)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0
0.0
4
1.0
2.0
3.0
4.0
5.0
Q.
0 6.0
7.0
8.0
9.0
10.0
-+--5/31/06 -9--6/23/06 7/18/06 --X-8/22/06
X9/20/06 10/18/06 11/16/2006
2007
Dissolved Oxygen (mg/1)
0.0 2.0 4.0 6.0 8.0 10.0 12.0
0.0
1.0
2.0
3.0
4.0
5.0
Q.
0 6.0
7.0
8.0
9.0
10.0
X5/9/2007 -0--6/8/2007 7/2/2007 --X- 8/9/2007
-!r-•9/5/2007 10/2/2007 10/31/2007 12/6/2007
14.0
Figure 5-7 Vertical profiles of dissolve oxygen concentrations measured at Station B2 at
Blewett Falls Lake, May through November, 2006-2009.
5-11
Section 5
0.0
0.0
1.0
2.0
3.0
4.0
t
w 5.0
0
6.0
7.0
8.0
9.0
--
-+--5/13/2008 -0--6/11/2008 7/8/2008 -)4-8/9/2008
#9/10/2008 10/8/2008 10/31/2008
2009
Dissolved Oxygen (mg/1)
0.0 2.0 4.0 6.0 8.0 10.0 12.0
0.0
1.0
2.0
3.0
4.0
t
w 5.0
0
6.0
7.0
8.0
9.0
-+--5/12/2009 -0--6/17/2009 7/16/2009 --X-8/5/2009
9/8/2009 10/7/2009 11/6/2009
Figure 5-7 (continued).
2008
Dissolved Oxygen (mg/1)
2.0 4.0 6.0 8.0
Environmental and Reservoir Conditions
10.0 12.0 14.0
14.0
5-12
Section 6 - 2006 Water Quality Results
6.1 Water Quality in the Pee Dee River, 2006
6. 1.1 Dissolved Oxygen - Tillery Dam to Turkey Top Creek (Reach 1)
During the May through October monitoring period, instantaneous DO concentrations in Reach 1
ranged from 0.7 to 17.5 mg/L at the four monitoring stations in Reach 1 (Table 6-1). Mean DO
concentrations at these four stations ranged from 5.4 to 7.2 mg/L for this entire period
(Table 6-1). Throughout Reach 1, DO concentrations exhibited a seasonal trend by decreasing
during May and June; remaining at a seasonal low during July and August; rising during early
September; fluctuating during September and early October; then rising during mid and late
October (Figure 6-1 and Figure 6-3).
Dissolved oxygen concentrations less than 1.0 mg/L occurred occasionally between August 13
and August 28 at Station TYCM1-1, and August 18 at Station TYCM4. However, these DO
concentrations below 1.0 mg/L only occurred for short periods (< 1% of total observations) of
time (Figure 6-3). At Station TYCM2 and TYCM3 the lowest DO concentrations occurred
throughout July and early September (Figure 6-3). On August 10; the lowest DO concentration
of 1.8 mg/L occurred at Station TYCM2 (Table 6-1). At Station TYCM3, DO concentrations
were lowest throughout August and September, but the lowest DO concentration occurred on
August 8.
Dissolved oxygen concentrations throughout Reach 1 fluctuated widely on most days during the
study period (Figure 6-3). These daily fluctuations were most apparent at Station TYCM2 where
DO concentrations often fluctuated by more than 11 mg/L during August. Dissolved oxygen
concentrations on August 24 ranged from 1.8 mg/L (lowest recorded at this station) to
13.7 mg/L. Dissolved oxygen concentrations were often supersaturated and exceeded 17 mg/L
and 200 percent saturation on some occasions during May. Station TYCM2 was the shallowest
of the monitored stations, and changes in river flow, coupled with diurnal fluctuations associated
with algal photosynthesis and respiration, likely contributed to these DO conditions.
6-1
Section 6
2006 Water Quality Results
Table 6-1 Dissolved oxygen concentration summary for Reach 1 of the Pee Dee River
below the Tillery Hydroelectric Plant, May 1 to October 31, 2006.

Dissolved Oxygen (DO) Variable
TYCN11-1 Reach 1 Stations
TYCM2 TYCM3
TYCM4
Mean DO (mg/L) ¶ 5.4 7.2 6.6 6.6
Range of DO (mg/L) 0.9-13.8 1.8-17.5 2.7-12.4 0.7-12.2
Percent of DO concentrations < 5.0 mg/L 46.8% 29.8% 21.2% 19.6%
Percent of DO concentrations < 4.0 mg/L 34.6% 15.5% 5.9% 5.5%
Percent of DO concentrations < 3.0 mg/L 21.9% 5.1% 0.8% 1.0%
Percent of DO concentrations < 2.0 mg/L 6.3% 0.2% 0.0% 0.3%
Date of lowest DO concentration 28-Aug 10-Aug 8-Aug 18-Aug
First DO concentration < 5.0 mg/L 7-May 7-May 10-Jun 11-Jun
Last DO concentration < 5.0 mg/L 6-Oct 5-Oct 24-Sep 19-Sep
First DO concentration < 4.0 mg/L 25-May 25-Jun 26-Jun 6-Jul
Last DO concentration < 4.0 mg/L 14-Sep 15-Sep 5-Sep 17-Sep
First DO concentration < 3.0 mg/L 7-Jun 22-Jul 1-Aug 15-Jul
Last DO concentration < 3.0 mg/L 7-Sep 30-Aug 16-Aug 18-Aug
First DO concentration < 2.0 mg/L 22-Jul 3-Aug NA+ 18-Aug
Last DO concentration < 2.0 mg/L 4-Sep 10-Aug NA+ 18-Aug
Longest duration of DO < 5.0 mg/L (hours) 95.47 23.95 48 47.67
Start of longest duration of DO < 5.0 mg/L 27-Aug 30-Aug 28-Jun 17-Jun
'NA = Not Applicable.
¶ Mean of all measurements for the monitoring period of May 1 to October 31, 2006.
Weekly mean DO concentrations varied throughout Reach 1 (Figure 6-1). However, weekly
mean DO concentrations for Station TYCM2, TYCM3, and TYCM4 were typically greater than
weekly mean DO concentrations at Station TYCM1-1.
Station TYCM1-1 had more instantaneous DO concentrations below 4.0 mg/L (34.6 %) than
other stations in Reach 1 (5.5-15.5 %) (Table 6-1 and Figure 6-2). Frequency distributions of
DO concentrations for Stations TYCM3 and TYCM4 were similar (Figure 6-2). Station
TYCM1-1 also had a greater percentage of DO concentrations < 5.0 mg/L and a lower
percentage of DO concentrations above 5.0 mg/L when compared to the other stations. Station
TYCM2 differed from other stations with a wider distribution of DO concentrations, including a
greater percentage of DO concentrations greater than 10.0 mg/L (Figure 6-2).
6-2
Section 6
10 -Fq
9
8
7
E
6
a?
X 5
O
4
0
w
N 3
0
2
1
0-k--
05/01/06
06/01/06 07/01/06 08/01/06 09/01/06 001/06
Date
e? TYCM1-1 El El El TYCM2 TYCM3 TYCM4
11/01/06
Figure 6-1 Weekly mean dissolved oxygen concentrations at continuous monitor stations
in Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 1
to October 31, 2006.
d
2006 Water Quality Results
Tillery Reach 1 - 2006
6-3
Section 6
2006 Water Quality Results
TilleryReach 1- 2006
20
15
C
a?
v
L
d
a
0 10
C
a?
Cr
a?
L
LL
5
0
? TYCM1-1 ? TYCM2 ? TYCM3 TYCM4
Figure 6-2 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant, May 1 to October 31, 2006.
The percentage of instantaneous DO concentrations below 5.0 mg/L in Reach 1 generally
decreased with increased distance from the Tillery Hydroelectric Plant. Nearly 47 percent of the
instantaneous DO concentrations recorded at Station TYCM1-1 from May through October were
less than 5.0 mg/L (Table 6-1). The percent of DO concentrations below 5.0 mg/L decreased at
downstream stations to a low of 19.6 percent at Station TYCM4.
In Reach 1, instantaneous DO concentrations first decreased below 5.0 mg/L on May 7 at
Stations TYCM1-1 and TYCM2 (Table 6-1). Dissolved oxygen concentrations below 5.0 mg/L
were recorded on many days at stations in Reach 1 through October. The last DO concentration
below 5.0 mg/L in Reach 1 was recorded at Station TYCM1-1 on October 6.
The lowest recorded instantaneous DO concentration during the study period was 0.7 mg/L at
Station TYCM4. Dissolved oxygen concentrations remained below 5.0 mg/L for about four
consecutive days in July at Station TYCM1-1 (Table 6-1).
0-1 1-2 2-3 3-4 4-6 5-6 6-7 7-8 8-9 9-1010-1111-1212-1313-1414-1515-1616-1717-18
Dissolved Oxygen (mg /L)
6-4
Section 6
2006 Water Quality Results
6.1.2 North Carolina Water Quality Standards for DO in Reach 1
The North Carolina water quality standards for DO require a daily average DO concentration of
at least 5.0 mg/L and all instantaneous DO concentrations must be at least 4.0 mg/L (NCDWQ
2007). Dissolved oxygen concentrations were below one or both water quality standards at all
four stations in Reach 1 for varying periods of time in 2006. Both water quality standards were
not met for at least 38 days from May through October, depending on the station (Table 6-2;
Figures 6-2 and 6-3). The period during which the daily average DO standard was not met in
Reach 1 extended from June 10 through September 15. Instantaneous DO concentrations in
Reach 1 initially decreased below 4.0 mg/L on May 25 and concentrations less than 4.0 mg/L
were recorded on some days until September 17 (Table 6-2).
Table 6-2 Assessments of daily dissolve oxygen concentrations from May 1 to October
31, 2006 at stations in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant compared to the North Carolina dissolved oxygen water
quality standards.

North Carolina Water Quality Standard
TYCM1-1 Reach 1 Stations
TYCM2 TYCM3
TYCM4
Daily average DO (5.0 mg/L)
Number of days not meeting standard 81 22 31 37
First day standard was not met 10-Jun 28-Jun 25-Jun 18-Jun
Last day standard was not met 14-Sep 15-Sep 13-Sep 13-Sep
Instantaneous DO (4.0 mg/L)
Number of days not meeting standard 97 56 28 31
First day standard was not met 25-May 25-Jun 26-Jun 6-Jul
Last day standard was not met 14-Sep 15-Sep 5-Sep 17-Sep
Number of days either standard was not met+ 98 59 38 44
Number of days assessed¶ 195 193 218 211
+The total number of days that one or both of the North Carolina water quality standards for daily average
(5.0 mg/L) and instantaneous (4.0 mg/L) DO concentrations were not met.
¶The number of days assessed was the total number of days from May 1 to October 31 when DO concentrations
were recorded for at least half of the day.
6-5
Section 6
Tillery Reach 1, Station CM1-1 - 2006
19
18
17
16
15
14
J 13
E 12
? 11
d
>' 10
X
O 9
v
> 8
0
rn 7
0 6
5
4
3
2
1
O
2006 Water Quality Results
T"NI
05/01/2006 06/01/2006 07/01/2006 08/01/2006 09/01/2006 10/01/2006 11/01/2006 12101/2006
Date
Tillery Reach 1, Station CM2 - 2006
IW
18
17
16
15
14
J 13
12
11
a?
10
X
O 9
v
> 8
0
?n 7
N
D 6
5
4
3
2
1
O
05/01/2006 06/01/2006 07/01/2006 08/01/2006 09/01/2006 10/01/2006 11/01/2006 12/01/2006 01/01/2007
Date
Figure 6-3 Daily averages (black line) and ranges (vertical bars) of dissolved oxygen
concentrations at Stations TYCM1-1, TYCM2, TYCM3 and TYCM4 in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
November 30, 2006.
6-6
Section 6
Tillery Reach 1, Station C PM - 2006
.Iy
18
17
16
15
14
J 13
E 12
? 11
a?
>, 10
x
O 9
v
> 8
0
m 7
Mn
0 6
5
4
3
2
1
0
2006 Water Quality Results
05/01/2006 06/01/2006 07/01/2006 08/01/2006 09/01/2006 10/01/2006 11/01/2006 12/01/2006 01/01/2007
Date
Tillery Reach 1, Station C IM - 2006
IV
18
17
16
15
14
J 13
E 12
? 11
>, 10
x
O 9
v
> 8
0
m 7
0 6
5
4
3
2
1
0

05/01/2006 06/01/2006 07/01/2006 08/01/2006 09/01/2006 10/01/2006 11/01/2006 12101/2006 01/01/2007
Date
Figure 6-3 (continued).
6-7
Section 6 2006 Water Quality Results
Dissolved oxygen concentrations were below each of the North Carolina water quality standards
more frequently at Station TYCM1-1 than at other Reach 1 stations. At Station TYCM1-1, DO
concentrations were below one or both water quality standards on 98 non-consecutive days from
May 25 to September 14 (Table 6-2 and Figure 6-3). At Station TYCM1-1, instantaneous DO
concentrations below 4.0 mg/L and daily average concentrations below 5.0 mg/L usually
occurred on the same days.
At Station TYCM2, DO concentrations were below one or both North Carolina water quality
standards for 59 non-consecutive days from June 25 to September 15 (Table 6-2 and Figure 6-3).
Instantaneous DO concentrations below 4.0 mg/L and daily average concentrations below
5.0 mg/L occurred on the same days. At Station TYCM2, instantaneous DO concentrations
below 4.0 mg/L occurred on 56 days whereas daily average DO concentrations less than
5.0 mg/L occurred on 22 days from June through September.
At Station TYCM3, DO concentrations were below one or both North Carolina water quality
standards for 38 non-consecutive days from June 25 to September 15 (Table 6-2 and Figure 6-3).
Instantaneous DO concentrations below 4.0 mg/L and daily average concentrations less than
5.0 mg/L typically did not occurred on the same days. At Station TYCM3, instantaneous DO
concentrations below 4.0 mg/L occurred on 28 days whereas daily average DO concentrations
below 5.0 mg/L occurred on 31 days from June through September.
At Station TYCM4, DO concentrations were below one or both North Carolina water quality
standards for 44 non-consecutive days from June 18 to September 17 (Table 6-2 and Figure 6-3).
Instantaneous DO concentrations below 4.0 mg/L and daily average concentrations below
5.0 mg/L typically did not occurred on the same days. At Station TYCM3 instantaneous DO
concentrations below 4.0 mg/L occurred on 31 days whereas daily average DO concentrations
below 5.0 mg/L occurred on 37 days from June through September.
6.1.3 Operational Effects of the Tillery Hydroelectric Plant
Dissolved oxygen concentrations in Reach 1 were affected by natural diel cycles (algal
respiration-photosynthesis), power plant operations, and tributary inflow. The relative degree of
algal respiration effect on DO concentrations compared to power plant operations could not be
readily partitioned out with this monitoring. Similar to observations in 2004 (Progress Energy
2005b), there were strong diel cycles in DO concentrations at all monitored stations, which likely
reflected the influence of algal photosynthesis and respiration on DO dynamics at these shallow
stations. These diel cycles were apparent on days of no power plant generation (Figure 6-4).
Dissolved oxygen concentrations typically changed by 4 to 8 mg/L during a 24-hour period at all
monitored stations. On days without power generation, the DO concentrations would begin to
rise around dawn, peak during early afternoon, decrease through the early evening, and then
remain low until the next day (Figure 6-4). When flows increased with power generation, the
DO concentrations correspondingly decreased. This effect was particularly evident when
generation began several hours after DO concentrations began to rise in the morning hours.
Dissolved oxygen concentrations would then decline to levels just above the pre-dawn
concentrations (this report and Progress Energy 2005b). The diel response of DO also showed
6-8
Section 6
2006 Water Quality Results
seasonal shifts with greater peaks in DO concentrations during the days of longer daylight length
and higher water temperatures (late May through September) when there was greater
photosynthetic activity as opposed to the days of shorter daylight length and lower water
temperatures (early May and October) (Table 6-3).
8/12/2006
14.0
12.0
ao
10.0
C
a 8.0
x
0 6.0
w
4.0
0
0 2.0
0.0 '
0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00
Time
I TYCM1-1 TYCM2 TYCM3 TYCM4
8/19/2006
14.0
Zr 12.0
o?io
10.0
C
bb 8.0
a
x
0 6.0
w
0 4.0
p 2.0
0.0
0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00
Time
I TYCM1-1 TYCM2 TYCM3 TYCM4
Figure 6-4 Dissolved oxygen concentrations (mg/L) on select days (August 12, 19,
and 27) with no power plant generation at Stations TYCM1-1, TYCM2,
TYCM3 and TYCM4.
6-9
Section 6
8/27/2006
14.0
12.0
o?io
10.0
c
a 8.0
x
6.0
w
6 4.0
0 2.0
0.0
2006 Water Quality Results
0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00
Time
I TYCM1-1 TYCM2 TYCM3 TYCM4
Figure 6-4 (continued).
Power generation affected the daily DO maximums and daily DO means more than daily DO
minimums at Station TYCM1-1 (Section 5.5.3 of Progress Energy 2005b). If no power
generation occurred, DO concentrations were typically above 5.0 mg/L for 8-12 hours. During
power generation days, this period of DO concentrations above 5.0 mg/L would be shorter, and
DO concentrations would decline below 5.0 mg/L during power generation.
Even on days when no power generation occurred, the DO concentrations were not always high
enough to meet both North Carolina water quality standards at Stations TYCM1-1 and
TYCM1-2 in early August (Table 6-3). From May 1 to October 31, the number of days without
any power generation during a 24-hour period at the Tillery Hydroelectric Plant totaled 22 days.
Of these 22 days, daily mean DO concentrations were less than 5.0 mg/L on 5 days at Station
TYCM1-1; 1 day at Station TYCM2; and 1 day at Station TYCM3. Instantaneous DO
concentrations below 4.0 mg/L occurred on 11 days at Station TYCM1-1; 4 days at Station
TYCM2; 1 day at Station TYCM3; and 2 days at Station TYCM4 (Table 6-3). These results
indicated that algal respiration, tributary inflow, and/or wicket gate leakage from the power plant
influenced DO dynamics during non-generation periods at Stations TYCM1-1, TYCM2,
TYCM3, and TYCM4.
6-10
Section 6
2006 Water Quality Results
Table 6-3 Days that no power was generated at the Tillery Hydroelectric Plant and
assessments of dissolved oxygen concentrations at stations in Reach 1 to
determine if they met the North Carolina water quality standards for daily
average and instantaneous dissolved oxygen concentrations during 2006.+
Reach 1 Stations
TYCMI-1 TYCM2 TYCM3 TYCM4
< 5.0 < 4.0 < 5.0 < 4.0 < 5.0 < 4.0 < 5.0 < 4.0
Date mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L

6-May
13-May
14-May
6-Jun X
7-Jun X
17-Jun X
14-Jul X X X
29-Jul X X X X X X
30-Jul X
12-Aug X X X
19-Aug X X X
27-Aug X X X
3-Sep X X
9-Sep X
7-Oct
8-Oct
11-Oct
15-Oct
16-Oct
21-Oct
22-Oct
29-Oct
Total 5 11 1 4 1 1 0 2
'Days when the daily average DO was < 5.0 mg/L and days when an instantaneous DO concentration was
< 4.0 mg/L are denoted with an "X". Days that the water quality standards were met are not marked.
6-11
Section 6
2006 Water Quality Results
6.1.4 Dissolved Oxygen-Blewett Falls Dam to Below Hitchcock Creek (Reach 2)
For the May through October study period, instantaneous DO concentrations ranged from 0.1 to
13.7 mg/L at the four monitoring stations in Reach 2 (Table 6-4). Mean DO concentrations at
these stations within Reach 2 ranged from 5.8 to 7.3 mg/L for the May through October period
(Table 6-4). Generally, DO concentrations at stations within Reach 1 decreased during May and
June; remained low during July and August; and then increased during early September through
October (Figure 6-5).
Weekly average DO concentrations were usually lowest at Stations BFCMIA and BFCM2.
Generally, the weekly average DO concentrations at the four other stations differed by less than
3.0 mg/L among all stations. Weekly average DO concentrations for all monitored stations
followed a similar spatial trend throughout the monitoring period with Stations BFCMIA and
BFCM2 generally differing by 1.0 mg/L to 4.0 mg/L from the other stations. Weekly average
DO concentrations were lowest at Stations BFCMIA and BFCM2 during the late part of August
(Figure 6-5).
6-12
Section 6 2006 Water Quality Results
Table 6-4 Dissolved oxygen concentration summary for Reach 2 of the Pee Dee River
below the Blewett Falls Hydroelectric Plant, May 1 to October 31, 2006.
Reach 2 Stations
Dissolved Oxvgen (DO) Variable BFCMl BFCMIA BFCM2 BFCM3
Mean DO (mg/L) + 6.3 5.9 5.8 7.3
Range of DO (mg/L) 1.5-11.8 0.1-11.7 0.2-13.0 0.3-13.7
Percent of DO concentrations < 5.0 mg/L 20.3% 33.0% 35.1% 18.6%
Percent of DO concentrations < 4.0 mg/L 7.3% 17.2% 17.4% 6.0%
Percent of DO concentrations < 3.0 mg/L 1.1% 6.7% 4.5% 0.7%
Percent of DO concentrations < 2.0 mg/L 0.2% 3.2% 1.2% 0.1%
Date of lowest DO concentration 22-Aug 5-Sep 5-Sep 10-Jun
First DO concentration < 5.0 mg/L 10-Jun 17-May 7-May 7-May
Last DO concentration < 5.0 mg/L 28-Sep 6-Oct 6-Oct 11-Sep
First DO concentration < 4.0 mg/L 10-Jun 23-May 1-Jun 28-May
Last DO concentration < 4.0 mg/L 20-Sep 13-Sep 13-Sep 5-Sep
First DO concentration < 3.0 mg/L 19-Jun 1-Jun 4-Jun 9-Jun
Last DO concentration < 3.0 mg/L 4-Sep 11-Sep 6-Sep 21-Aug
First DO concentration < 2.0 mg/L 21-Aug 21-Jun 21-Jun 9-Jun
Last DO concentration < 2.0 mg/L 22-Aug 7-Sep 6-Sep 10-Jun
Longest duration of DO < 5.0 mg/L (hours) 144.5 72.11 72.19 23.79
Start of longest duration of DO < 5.0 mg/L 13-Sep 2-Sep 25-Jun 10-Aug
'Mean of all measurements for the monitoring period of May 1 to October 31, 2006.
Instantaneous DO concentrations below 5.0 (mg/L) were most frequent at Stations BFCMIA
(33.0%) and BFCM2 (35.1%) during May through October (Table 6-4). Instantaneous DO
concentrations below 5.0 mg/L represented about 20 percent or less of the total number of
measurements at Stations BFCM1 and BFCM3 during this same period. The percentage of DO
concentrations below 4.0 mg/L were greatest at Stations BFCMIA (17.2 %) and BFCM2
(17.4 %). Frequency distributions indicated that Station BFCMIA had more DO concentrations
below 3.0 mg/L while Station BFCM3 had more DO concentrations greater than 9.0 mg/L
(Figure 6-6).
6-13
Section 6
12--
11
--
10--
9
J
8
E
7
N
x 6
O
5
N 4
N
3
2
1
0?
05/01/06
06/01/06 07/01/06 08/01/06 09/01/06 001/06
Date
e BFCM1 El El El BFCM1A ?? BFCM2 BFCM3
11/01/06
Figure 6-5 Weekly mean dissolved oxygen concentrations at continuous monitor stations
in Reach 2 of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2006.
2006 Water Quality Results
Blewett Falls Reach 2 - 2006
6-14
Section 6
Ble Adt Falls Reach 2 - 2006
30
2006 Water Quality Results
25
C 20
a?
L
CL
15
C
a?
Cr
10
LL
5
0
0-1 1-2 2-3 34 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-14
Dissolved Oxygen (mg1L)
BFCM1 ? BFCM1A ? BFCM2 BFCM3
Figure 6-6 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, May 1 to October 31, 2006.
Instantaneous DO concentrations initially declined below 5.0 mg/L in Reach 2 on May 7 at
Stations BFCM2 and BFCM3 (Table 6-4). Dissolved oxygen concentrations below 5.0 mg/L
were recorded in Reach 2 until October 6 at Stations BFCMIA and BFCM2; and mid to late
September at Stations BFCMI and BFCM3 (Table 6-4).
The minimum DO concentration for Reach 2 was 0.1 mg/L at Station BFCMIA on September 5
(Table 6-4). The lowest DO concentrations at Stations BFCM1, BFCMIA and BFCM2 occurred
during the late August to early September time frame. The longest duration (144.5 hours at
Station BFCM1) of DO concentrations below 5.0 mg/L also occurred during this time period.
The lowest DO concentrations at Station BFCM3 occurred on June 10.
6-15
Section 6
2006 Water Quality Results
6.1.5 North Carolina Water Quality Standards for DO in Reach 2
Dissolved oxygen concentrations at Reach 2 stations were below one or both North Carolina
water quality standards for at least 42 days from May through October, depending upon the
station (Table 6-5). All four stations had instantaneous DO concentrations below 4.0 mg/L and
daily average DO concentrations below 5.0 mg/L during this period (Figure 6-7). Daily average
DO concentrations were below the water quality standard for some days in Reach 2 from June 9
to October 6. Dissolved Oxygen concentrations below the instantaneous water quality standard
(4.0 mg/L) were recorded on some days in Reach 2 beginning May 23 and ending September 20.
Dissolved oxygen concentrations were below one or both water quality standards at Station
BFCM3 on 42 days, the fewest of any stations in Reach 2.
Table 6-5 Assessments of daily dissolved oxygen concentrations from May 1 to October
31, 2006 at stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant compared to the North Carolina dissolved oxygen water
quality standards.
Reach 2 Stations
North Carolina Water Quality Standard BFCMI BFCMIA BFCM2 BFCM3
Daily average DO (5.0 mg/L)
Number of days not meeting standard
First day standard was not met
Last day standard was not met
Instantaneous DO (4.0 mg/L)
Number of days not meeting standard
First day standard was not met
Last day standard was not met
Number of days either standard was not met+
Number of days assessed¶
38 63 77 7
12-Jun 1-Jun 1-Jun 9-Jun
19-Sep 9-Sep 6-Oct 24-Aug
40 89 84 41
10-Jun 23-May 1-Jun 28-May
20-Sep 13-Sep 13-Sep 5-Sep
47 91 88 42
192 217 217 207
+The total number of days that one or both of the North Carolina water quality standards for daily average
(5.0 mg/L) and instantaneous (4.0 mg/L) DO concentrations were not met.
¶The number of days assessed was the total number of days from May 1 to October 31 when DO concentrations
were recorded for at least half of the day.
6-16
Section 6 2006 Water Quality Results
Blevtett Falls Reach Z Station CM1 - 2006
15
14
13
12
11
J 10
a?
E
9
c
d
a? 8
a
X
O 7
v
d
6
O
y 5
D
4
3
2
1
O
05/01/2006 06/01/2006 07/01/2006 08/01/2006 09/01/2006 10/01/2006 11/01/2006 12101/2006 01/01/2007
Date
Blewett Falls Reach Z Station CM1A - 2006
14
13
12
11
J 10
a?
E
9
c
d
a? 8
X,
X
O 7
v
d
6
0
N
5
4
3
2
1
O
05/01/2006 06/01/2006 07/01/2006 08/01/2006 09/01/2006 10/01/2006 11/01/2006 12101/2006 01/01/2007
Date
Figure 6-7 Daily averages (black line) and ranges (vertical bars) of dissolved oxygen
concentrations at Stations BFCM1, BFCMIA, BFCM2, and BFCM3 in
Reach 2 of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to November 30, 2006.
6-17
Section 6
2006 Water Quality Results
15-
14-
13-
12-
11 J 10-
9-
d
8-
a? O 7
x
d
6-
O
(A
H 5
D
4
3
2
1
O
05?01/2006 06/01/2006 07/01/2006 08/01/2006 09/01/2006 10101/2006 11/01/2006 12/01/2006 01/01/2007
Date
Blewett Falls Reach 2, Station CM3 - 2006
-13
14
13
12
11
J 10
a?
9
c
d
a? 8
xx
O 7
d
6
O
N
H 5
D
4
3
2
1
O
05?01/2006 06/01/2006 07/01/2006 08/01/2006 09/01/2006 10101/2006 11/01/2006 12101/2006 01/01/2007
Date
Figure 6-7 (continued).
6-18
Blewe# Falls Reach 2, Station CM2 - 2006
Section 6 2006 Water Quality Results
At Station BFCM1, both instantaneous and daily average water quality standards were not met
for 47 days between June 10 and September 20 (Table 6-5 and Figure 6-7). The daily average
DO concentration was below 5.0 mg/L on 38 days from June 12 to September 19. Instantaneous
DO concentrations were below 4.0 mg/L on 40 days between June 10 and September 20.
Dissolved oxygen concentrations were below the instantaneous and daily average water quality
standards on more days at Station BFCMIA than at any other Station in Reach 2. At Station
BFCMIA, the instantaneous water quality DO standard was not met on 91 days beginning on
May 23 and ending on September 13 (Table 6-5 and Figure 6-7). The daily average DO
concentration was below 5.0 mg/L on 63 days between June 1 and September 9. Instantaneous
DO concentrations were below 4.0 mg/L on 89 days between May 23 and October 13.
At Station BFCM2, both instantaneous and daily average water quality standards were not met
for 88 days between June 1 and September 13. The daily average DO concentration was below
5.0 mg/L on 77 days from June 1 to October 6. Instantaneous DO concentrations were below
4.0 mg/L on 84 days between June 1 and September 13 (Table 6-5 and Figure 6-7).
At Station BFCM3, the water quality standards were not met for 42 days between May 28 and
September 5. The daily average DO concentration was below 5.0 mg/L on 7 days from June 9 to
August 24. Instantaneous DO concentrations were below 4.0 mg/L on 41 days between May 28
and September 5 (Table 6-5 and Figure 6-7).
6.1.6 Operational Effects of the Blewett Falls Hydroelectric Plant
A comparison between DO concentrations at Station BFCM1 and Blewett Falls Hydroelectric
Plant power generation flows from May 1 to October 31, 2006 showed that DO concentrations
below 4.0 mg/L occurred about equally during generation and non-generation periods primarily
in early July, early to mid August, and late September (Tables 6-5 and 6-6). Generally, these
periods of lower DO concentrations occurred in the evening to early morning hours which
coincided with algal respiration in the tailwaters area.
On days when no power generation occurred, the DO concentrations were not always high
enough to meet both North Carolina water quality standards at Stations BFCM1, BFCMIA,
BFCM2, and BFCM3. From May 1 to October 31, the number of days without any power
generation during a 24-hour period at the Blewett Falls Plant totaled 30 days. Of these 30 days,
daily mean DO concentrations were below 5.0 mg/L on 11 days at Station BFCM1; 6 days at
Station BFCM2; and 13 days at Station BFCM2. Instantaneous DO concentrations below
4.0 mg/L occurred on 11 days at Station BFCM1; 13 days at Station BFCMIA; 13 days at
Station BFCM2; and 8 days at Station BFCM3 (Table 6-6). These results indicated that algal
respiration and/or wicket gate leakage from the power plant likely influenced DO dynamics
during non-generation periods at all monitored stations.
6-19
Section 6 2006 Water Quality Results
Table 6-6 Days that no power was generated at the Blewett Falls Hydroelectric Plant
and assessments of dissolved oxygen concentrations at stations in Reach 1 to
determine if they met the North Carolina water quality standards for daily
average and instantaneous dissolved oxygen concentrations during 2006.+
Reach 1 Stations
BFCMI BFCMIA BFCM2 BFCM3
< 5.0 < 4.0 < 5.0 < 4.0 < 5.0 < 4.0 < 5.0 < 4.0
Date mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L

13-May
14-May
3 -Jun X X X X
4-Jun X X X X X
5-Jun X X X X X
6-Jun X X X X
7-Jun X X X X
12-Aug X X X X
19-Aug X X X X X
20-Aug X X X X X X X
26-Aug X X X X X X
27-Aug X X X X X X X
11-Sep X X X X
12-Sep X X X X X
13-Sep X X X X
14-Sep X X
15-Sep X
16-Sep X X
17-Sep X X
18-Sep X X
19-Sep X X
6-Oct
7-Oct
8-Oct
9-Oct
10-Oct
14-Oct
15-Oct
22-Oct
29-Oct
Total 11 11 6 13 13 13 0 8
'Days when the daily average DO was < 5.0 mg/L and days when an instantaneous DO concentration was
< 4.0 mg/L are denoted with an "X". Days that the water quality standards were met are not marked.
6-20
Section 6 2006 Water Quality Results
6.2 Water Temperature in the Pee Dee River
6.2.1 Reach 1 - Tillery Dam to Turkey Top Creek
Water temperatures ranged from 8.1 to 35.3°C in Reach 1 from May through October
(Table 6-7). Mean water temperatures in Reach 1 from May through October ranged from
22.8°C at Station TYCM2 to 23.3°C at Station TYCM4 (Table 6-7). The Reach 1 maximum
instantaneous temperature of 35.3°C occurred at Station TYCM2 on August 3. Weekly mean
temperatures were slightly lower at Station TYCM1-1 than the other stations from May through
August but converged with mean temperatures at the other stations during September and
October (Figure 6-8). Weekly mean temperatures at Stations TYCM3 and TYCM4 were very
similar and usually slightly higher than weekly mean temperatures at Station TYCM2
(Figure 6-8).
Table 6-7 Summary statistics of water quality variables from stations in Reach 1 of the
Pee Dee River below the Tillery Hydroelectric Plant, May 1 to October 31,
2006.

Water Quality Variable
TYCMl-1 Reach 1 Stations
TYCM2 TYCM3
TYCM4
Mean temperature (°C) 23.0 22.8 23.1 23.3
Temperature range (°C) 10.6-31.2 8.6-35.3 8.1-33.1 8.6-32.7
Median pH 6.8 7.1 7.1 7.1
pH range 5.6-9.8 5.8-10.0 6.3-9.0 6.4-9.3
Mean specific conductance (p S/cm) 98 97 115 120
Specific conductance range (pS/cm) 31-116 30 - 115 71 - 309 79 - 284
6-21
Section 6
Tillery F?each 1 - 2006
X
a?
ea
L
T
W
d
U
N
N
N
L
d
d
L
3
10
L
d
Q
E
d
2006 Water Quality Results
01---
06/01/06
06/01/06 07/01/06 06/01/06 09/01/06 10/01/06 11/01/06
Date
- TYCM1-1 - TYCM2 ° TYCM3 TYCM4
Figure 6-8 Weekly mean temperatures at continuous monitor stations in Reach 1 of the
Pee Dee River below the Tillery Hydroelectric Plant, May 1 to October 31,
2006.
Temperature values greater than the North Carolina water quality standard of 32°C were most
often observed at Station TYCM2 during July and August. Infrequent excursions above 32°C
were noted at Stations TYCM3 and TYCM4. Temperature measurements greater than 32°C at
Station TYCM2 accounted for less than three percent (n = 494) of the total number of discrete
temperature measurements at this station (n = 17,760). There were 21 measurements greater
than 32°C at Station TYCM4 (n = 18,624) and 17 water temperature measurements greater than
32°C at Station TYCM3 (n = 19,776).
6.2.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek
Water temperatures ranged from 9.5°C (all stations) to 35.9°C at Station BFCM3 from May
through October in Reach 2 (Table 6-8). Mean water temperatures in Reach 2 ranged from
23.4°C at BFCM1 to 23.6°C at Stations BFCMIA and BFCM3 (Table 6-8). The Reach 2
maximum instantaneous temperature of 35.9°C occurred at Station BFCM3 on August 3.
Weekly average water temperatures at all four stations were very consistent throughout the study
period (Figure 6-9).
6-22
Section 6
2006 Water Quality Results
Table 6-8 Summary statistics of water quality variables from stations in Reach 2 of the
Pee Dee River below the Blewett Falls Hydroelectric Plant, May 1 to October
31, 2006.

Water Quality Variable
BFCMI Reach 2 Stations
BFCMIA BFCM2
BFCM3
Mean temperature (°C) 23.4 23.6 23.5 23.6
Temperature range (°C) 9.5 -32.1 9.5 -33.3 9.5-33.0 9.5 -35.9
Median pH 7.0 7.0 7.0 7.2
pH range 6.2-9.1 6.4-8.7 6.3-8.4 6.2-9.7
Mean specific conductance (pS/cm) 106 109 105 107
Specific conductance range (p S/cm) 71 - 140 62 - 143 67 - 137 69 - 142
Blewett Falls Reach 2 - 2006
40
Z,
30
a?
d
U
N
N
N
L
im 20
d
d
L
3
L
d
E 10
d
H
0 i
05/01/06
06/01/06 07101106 08/01/06 09/01/06 10/01/06
Date
6 e BFCM1 BFCM1A ° BFCM2 BFCM3
11/01/06
Figure 6-9 Weekly mean temperatures at continuous monitor stations in Reach 2 of the
Pee Dee River below the Blewett Falls Hydroelectric Plant, May 1 to October
31, 2006.
6-23
Section 6 2006 Water Quality Results
Temperature values greater than the North Carolina water quality standard of 32°C were most
often observed at Station BFCM3 during July and August. Infrequent excursions above 32°C
were noted at Stations BFCM1, BFCMIA, and BFCM2. Temperature measurements greater
than 32°C at Station BFCM3 accounted for less than 4% (n = 699) of the total number of discrete
measurements at this station (n = 18,720). There were 64 measurements > 32°C at Station
BFCM2 (n = 19,968), 32 measurements > 32°C at Station BFCMIA (n = 19,968), and 1
measurements > 32°C at Station BFCM1 (n = 20,736).
6.3 pH in the Pee Dee River
6.3.1 Reach 1 - Tillery Dam to Turkey Top Creek
Median pH values at stations in Reach 1 were slightly acidic to near neutral (6.8 to 7.1) for the
study period (Table 6-7). Instantaneous pH values in Reach 1 ranged from 5.6 at Station
TYCM1-1 to 10.0 at Station TYCM2. The minimum pH recorded at the other three stations
ranged from 5.6 to 6.4. Weekly mean pH means ranged from 6.3 to 8.4 at all stations
(Figure 6-10). Station TYCM1-1 typically had the lowest weekly mean pH values while Station
TYCM2 usually had the highest weekly mean pH values. There was wide variation in weekly
mean pH values which likely reflect the effect of algal respiration and photosynthesis at each
station. Stations TYCM3 and TYCM4 exhibited similar weekly mean pH trends during the
monitoring period.
Tillery Reach 1 - 2006
x
Q
4
0i
05(01/06
06/01/06 07/01/06 08/01/06 09(01/06 10/01/06
Date
e°--9 TYCM1-1 - TYCM2 ° TYCM3 TYCM4
11/01/06
Figure 6-10 Weekly mean pH values at continuous monitor stations in Reach 1 of the Pee
Dee River below the Tillery Hydroelectric Plant, May 1 to October 31, 2006.
6-24
Section 6 2006 Water Quality Results
The daily pH values fluctuated over a large range at Station TYCM2 and instantaneous values
frequently exceeded 9.0, particularly during May. These instantaneous pH values exceeded the
upper limit (9.0) of the North Carolina water quality standard for pH (NCDWQ 2007).
Approximately 9.4% of the total number of measurements (n = 17,760) at Station TYCM2
exceeded 9.0. Instantaneous pH values > 9.0, occurred less than 1.0 % at other stations. These
pH fluctuations at Station TYCM2 followed DO trends; reflect algal photosynthesis and
respiration (Figure 6-11). Algae produce oxygen and take up carbon dioxide during
photosynthesis, resulting in a pH increase. Conversely, when algae respire and produce carbon
dioxide, the pH decreases.
J
bA
E
c
w
ao
a
O
w
0
0
20.0
18.0
16.0
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00
Time
Dissolved Oxygen pH
12.0
10.0
8.0
6.0 a
4.0
2.0
0.0
Figure 6-11 Dissolved oxygen concentrations and pH values at Station TYCM2 in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 6 to
12, 2006.
6.3.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek
Median pH values at stations in Reach 2 were neutral to slightly basic (7.0 to 7.2) for the study
period (Table 6-8). Instantaneous pH values in Reach 2 ranged from 6.2 at Stations BFCM1 and
BFCM3 to 9.7 at Station BFCM3. Weekly mean pH values ranged from 6.4 to 7.8 (Figure 6-12).
Generally, Station BFCM3 had greater weekly mean pH values more often than the other
stations combined. There was more daily variation in pH values at Station BFCM3 due to the
greater amount of algal growth and subsequent photosynthesis and respiration (Table 6-8). At
the other three stations, pH values varied among weeks and there were no consistent spatial
trends in pH.
6-25
Section 6
Blevmd Falls Reach 2 - 2006
= 4
CL
0
2006 Water Quality Results
05/01/06 06/01/06 07/01/06 06/01/06 09/01/06 10/01/06 11/01/06
Date
e e a BFCM1 - BFCM1A - BFC1W BFC:IVI3
Figure 6-12 Weekly mean pH values at continuous monitor stations in Reach 2 of the Pee
Dee River below the Blewett Falls Hydroelectric Plant, May 1 to October 31,
2006.
Variation in pH was greatest throughout Reach 2 from late August through September which
coincided with a period of lower flow and warmer than average air temperatures. Variation in
pH was greatest at Station BFCM3, likely due to the algae accumulation on the continuous
monitor. Approximately 7.3 % of the total number of discrete pH values (n = 19,968) at Station
BFCM3 exceeded the North Carolina water quality standard of 9.0. Discrete pH values
exceeding 9.0, accounted for less than 1.0% (n = 17,376) at Station BFCM1.
6.4 Specific Conductance in the Pee Dee River
6.4.1 Reach 1 - Tillery Dam to Turkey Top Creek
Mean specific conductance values for stations within Reach 1 from May through October ranged
from 97 µS/cm at Station TYCM2 to 120 µS/cm at Station TYCM4 (Table 6-7). Instantaneous
specific conductance values within Reach 1 ranged from 30 to 309 µS/cm. Weekly mean
specific conductance values were always greater at Stations TYCM3 and TYCM4 than at
Stations TYCM1-1 and TYCM2 (Figure 6-13). Weekly mean specific conductance values at
Stations TYCM1 and TYCM2 ranged from 83 to 105 µS/cm while values at Stations TYCM3
and TYCM4 ranged from 90 to 188 µS/cm (Figure 6-13). Weekly mean specific conductance
values at Station TYCM4 were usually greater than values at Station TYCM3.
6-26
Section 6
2006 Water Quality Results
Stations TYCM3 and TYCM4 were influenced by Rocky River inflow, as evidenced by higher
specific conductance values and greater variability. Specific conductance values were typically
low during power generation. During non-power generating periods, specific conductance
steadily increased as Rocky River inflow contributed to more of the water volume in the Pee Dee
River. The Rocky River and Brown Creek both enter the Pee Dee River between Stations
TYCM2 and TYCM3, and high specific conductance in the Rocky River has been documented
by the NCDWQ (2010) and Progress Energy (2003, 2006a).
Tillery Reach 1 - 2006
190
180
170
160
150
140
o 130
120 - 4
v
110 - d
i 100-----
90
0 80
0 U 70
v
wv60
a? 50
Q
N 40
30
20
10
0
0601/06 06/01106 07101106 =01/06 09/01/06 10/01/06 11/01/06
Date
- TYCM1-1 - TYCM2 - TYCIM TY(?VI4
Figure 6-13 Weekly mean specific conductance values at continuous monitor stations in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
October 31, 2006.
6-27
Section 6 2006 Water Quality Results
6.4.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek
Mean specific conductance values at stations in Reach 2 ranged from 105 to 109 µS/cm for the
period from May through October (Table 6-8). Instantaneous specific conductance values
ranged from 62 to 143 µS/cm. Weekly mean specific conductance values at each station
generally showed similar temporal trends during the study period (Figure 6-14).
Blevmd Falls Reach 2 - 2006
130
120
110
E 100
n
Cl) 90
3
v 80
70
v
3
60
O
U 50
v
v 40
d
O_ 30
Cl)
20
10
0 i
05/01/06
06/01/06 07101106 08/01/06 09/01/06 10/01/06
Date
e e a BFCM1 - BFCM1A - BFC1W BFC:IVI3
11/01/06
Figure 6-14 Weekly mean specific conductance values at continuous monitor stations in
Reach 2 of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2006.
6-28
Section 7 - 2007 Water Quality Results
7.1 Water Quality in the Pee Dee River 2007
7. 1.1 Dissolved Oxygen - Tillery Dam to Turkey Top Creek (Reach 1)
During the May through October monitoring period, instantaneous DO concentrations in Reach 1
ranged from 0.1 to 17.0 mg/L at the four stations in Reach 1 (Table 7-1). Mean DO
concentrations at these four stations ranged from 5.2 to 6.9 mg/L. Throughout Reach 1, DO
concentrations exhibited a seasonal trend by decreasing during May and June; remaining low
during July and August; rising during early September; fluctuating during September and early
October; and then increasing in mid and late October (Figures 7-1 and 7-2).
Dissolved oxygen concentrations less than 1.0 mg/L occurred occasionally between August 21
and September 6 at Station TYCM1-1, and July 3-4 at Station TYCM4 (Figure 7-2). However,
these DO excursions below 1.0 mg/L only occurred for a short period(< 1% of total
observations) of time. At Stations TYCM2 and TYCM3, the lowest DO concentrations occurred
throughout July and early September (Figure 7-2). On August 24, the lowest DO concentration
of 1.8 mg/L occurred at Station TYCM2 (Table 7-1). At Station TYCM3, low DO
concentrations occurred throughout August and September, but the lowest was recorded on
September 7 at 2.6 mg/L.
Dissolved oxygen concentrations throughout Reach 1 fluctuated widely on most days during the
study period (Figure 7-2). These fluctuations were most apparent at Station TYCM2 where DO
concentrations often ranged more than 11 mg/L daily during August. Dissolved oxygen
concentrations on August 24 ranged from 1.8 mg/L to 13.7 mg/L. Dissolved oxygen
concentrations above 17.0 mg/L and 200 percent saturation occurred on some occasions during
May. As previously mentioned, station TYCM2 was the shallowest of the monitoring stations,
and the flow changes, coupled with diurnal fluctuations associated with algal photosynthesis and
respiration, likely contributed to these conditions.
7-1
Section 7
2007 Water Quality Results
Table 7-1 Dissolved oxygen concentration summary for Reach 1 of the Pee Dee River
below the Tillery Hydroelectric Plant, May 1 to October 31, 2007.

Dissolved Oxygen (DO) Variable
TYCMl-1 Reach 1 Stations
TYCM2 TYCM3
TYCM4
Mean DO (mg/L) ¶ 5.2 6.9 6.6 6.8
Range of DO (mg/L) 0.2-14.0 1.8-17.0 2.6-14.1 0.1-13.6
Percent of DO concentrations < 5.0 mg/L 50.8% 37.6% 22.0% 16.7%
Percent of DO concentrations < 4.0 mg/L 37.9% 25.3% 8.7% 7.1%
Percent of DO concentrations < 3.0 mg/L 27.6% 8.8% 0.2% 1.1%
Percent of DO concentrations < 2.0 mg/L 10.3% 0.2% NA+ 0.2%
Date of lowest DO concentration 27-Aug 24-Aug 7-Sep 4-Jul
First DO concentration < 5.0 mg/L 17-May 3-May 1-Jun 31-May
Last DO concentration < 5.0 mg/L 25-Oct 19-Oct 27-Sep 16-Oct
First DO concentration < 4.0 mg/L 26-May 27-May 18-Jun 1-Jun
Last DO concentration < 4.0 mg/L 19-Oct 19-Sep 14-Sep 14-Sep
First DO concentration < 3.0 mg/L 19-Jun 29-May 28-Jul 1-Jun
Last DO concentration < 3.0 mg/L 18-Sep 14-Sep 7-Sep 7-Sep
First DO concentration < 2.0 mg/L 27-Jun 3-Aug NA+ 3-Jul
Last DO concentration < 2.0 mg/L 17-Sep 7-Sep NA+ 26-Jul
Longest duration of DO < 5.0 mg/L (hours) 36.3 19.0 18.8 34.8
Start of longest duration of DO < 5.0 mg/L 24-Jun 5-Jul 19-Jul 3-Jul
'NA = Not Applicable.
¶ Mean of all measurements for the monitoring period of May 1 to October 31, 2007.
7-2
Section 7
11
10--
9--
8
7
N
of 6
a
X
O 6
d
4
0
N
N
p 3
2
1
0 1---
05/01/07
06(01107 07101107 08/01/07 09101107 10/01107
Date
- TYCM1-1 - TYCM2 - TYCPM TYCM4
11/01/07
Figure 7-1 Weekly mean dissolved oxygen concentrations at continuous monitor stations
in Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 1
to October 31, 2007.
2007 Water Quality Results
Tillery Reach 1 - 2007
7-3
Section 7
Tillery Reach 1, Station CM1-1 - 2007
19
18
17
16
15
14
J 13
E 12
? 11
>' 10
X
O 9
v
> 8
Cn 7
0 6
5
4
3
2
1
O
2007 Water Quality Results
051`01/2007 06/01/2007 07/01/2007 08/01/2007 09/01/2007 10/01/2007 11/01/2007 12101/2007
Date
Tillery Reach 1, Station CM2 - 2007
19
18
17
16
15
14
:a 13-
E 12-
>1 lo- W
07/01/2307 tea, ,?, .aa,? 11/01/2007 12101/2307
Date
051`01/2007 06/01/2007 07/01/2307 Figure 7-2 Daily averages (black line) and ranges (vertical bars) of dissolved oxygen
concentrations at Stations TYCM1-1, TYCM2, TYCM3 and TYCM4 in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
November 30, 2007.
7-4
Section 7
2007 Water Quality Results
Tillery Reach 1, Station CM3 - 2007
19
18
17
16
15
14
J 13
0-
12
? 11
>, lo-
x
O g
v
d 8
0
rn 7
0 6-
5- 4
3
2
1
0
05/01/2007 06/01/2007 07/01/2007 08/01/2007 09/01/2007 10/01/2007 11/01/2007
Date
Tillery Reach 1, Station C IM - 2007
19
18
17
16
15
14
13
E 12
C 11
d
a 10
x
O g
> 8
w 7
0 6
5
4
3
2
1
0
12/01/2007
05?01/2007 06/01/2007 07/01/2007
Figure 7-2 (continued).
08/01/2007 09/01/2007 10/01/2007 11/01/2007 12/0112007
Date
7-5
Section 7
Weekly mean DO concentrations varied throughout Reach 1 (Figure 7-3). However, weekly
mean DO concentrations for Station TYCM2, TYCM3, and TYCM4 were typically greater than
weekly mean DO concentrations at Station TYCM1-1.
Station TYCM1-1 had more instantaneous DO concentrations below 4.0 mg/L (37.9%) than
other stations in Reach 1 (7.1 to 25.3%) (Table 7-1 and Figure 7-3). Frequency distributions of
DO concentrations for Stations TYCM3 and TYCM4 were similar (Figure 7-3). Station
TYCM1-1 also had a greater percentage of DO concentrations less than 5.0 mg/L and a lower
percentage of DO concentrations above 5.0 mg/L when compared to the other Reach 1 stations.
Station TYCM2 differed from other stations with a wider distribution of DO concentrations,
including a greater percentage of DO concentrations exceeding 10.0 mg/L (Figure 7-3).
TilleryReach 1- 2007
25
20
C
m
v
15
a
a
C
as
10
Cr
GD
L
LL
5
0
TYCM14 ? TYCM2 ? TYCM3 TYCM4
Figure 7-3 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant, May 1 to October 31, 2007.
2007 Water Quality Results

0-1 1-2 2-3 3-4 4-6 5-6 6-7 7-8 8-9 9-10 10-1111-1212-1313-1414-1515-1616-17
Dissolved Oxygen (ni /L)
7-6
Section 7 2007 Water Quality Results
The percentage of instantaneous DO concentrations below 5.0 mg/L in Reach 1 generally
decreased with increased distance from the Tillery Hydroelectric Plant. Nearly 50 percent of the
instantaneous DO concentrations recorded at Station TYCM1-1 were < 5.0 mg/L from May
through October (Table 7-1). The percent of DO concentrations below 5.0 mg/L decreased at
downstream stations to a low of 16.7 percent at Station TYCM4.
In Reach 1, instantaneous DO concentrations first decreased below 5.0 mg/L on May 3 at Station
TYCM2 (Table 7-1). Dissolved oxygen concentrations below 5.0 mg/L were recorded on many
days at stations in Reach 1 through October. The last DO concentration below 5.0 mg/L in
Reach 1 was recorded at Station TYCM1-1 on October 25.
The lowest recorded instantaneous DO concentration during the study period was 0.1 mg/L at
Station TYCM4. Dissolved oxygen concentrations remained below 5.0 mg/L for about 1.5
consecutive days at Station TYCM1-1 and TYCM4 (Table 7-1), the longest period for the four
monitored stations in Reach 1.
7.1.2 North Carolina Water Quality Standards for DO in Reach 1
The North Carolina water quality standards for DO require a daily average DO concentration of
at least 5.0 mg/L and all instantaneous DO concentrations must be at least 4.0 mg/L (NCDWQ
2007). Dissolved oxygen concentrations were below one or both North Carolina water quality
standards at all four stations in Reach 1 for varying periods of time. The North Carolina water
quality standards were not met for at least 46 days from May through October, depending on the
station (Table 7-2; Figures 7-1 and 7-2). The period during which the water quality standard for
daily average DO (5.0 mg/1) was not met in Reach 1 extended from May 29 to October 22.
Instantaneous DO concentrations (water quality standard 4.0 mg/L) in Reach 1 initially
decreased below 4.0 mg/L on May 26 and concentrations less than 4.0 mg/L were recorded on
some days until October 19 (Table 7-2).
7-7
Section 7
2007 Water Quality Results
Table 7-2 Assessments of daily dissolved oxygen concentrations from May 1 to October
31, 2007 at stations in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant compared to the North Carolina dissolved oxygen water
quality standards.
Reach 1 Stations
North Carolina Water Quality Standard TYCM1 TYCM2 TYCM3 TYCM4
Daily average DO (5.0 mg/L)
Number of days not meeting standard 91 14 24 24
First day standard was not met 29-May 25-Jun 20-Jun 2-Jun
Last day standard was not met 22-Oct 13-Sep 12-Sep 7-Sep
Instantaneous DO (4.0 mg/L)
Number of days not meeting standard 115 99 56 45
First day standard was not met 26-May 27-May 18-Jun I-Jun
Last day standard was not met 19-Oct 19-Sep 14-Sep 14-Sep
Number of days either standard was not met+ 117 99 56 46
Number of days assessed¶ 214 214 214 214
+The total number of days that one or both of the North Carolina water quality standards for daily average
(5.0 mg/L) and instantaneous (4.0 mg/L) DO concentrations were not met.
¶The number of days assessed was the total number of days from May 1 to October 31 when DO concentrations
were recorded for at least half of the day.
Dissolved oxygen concentrations were below each of the North Carolina water quality standards
more frequently at Station TYCM1-1 than at other Reach 1 stations. At Station TYCM1-1, DO
concentrations were below one or both water quality standards on 117 non-consecutive days
from May 26 to October 19 (Table 7-2 and Figure 7-2). At Station TYCM1-1, DO
concentrations below 4.0 mg/L and daily average DO concentrations below 5.0 mg/L usually
occurred on the same days.
At Station TYCM2, DO concentrations were below one or both North Carolina water quality
standards for 99 non-consecutive days from May 27 to September 19 (Table 7-2 and Figure 7-2).
Instantaneous DO concentrations below 4.0 mg/L and daily average concentrations below
5.0 mg/L occurred on the same days. At Station TYCM2, DO concentrations below 4.0 mg/L
occurred on 99 days whereas daily average DO concentrations less than 5.0 mg/L occurred on 14
days from May-September.
At Station TYCM3, DO concentrations were below one or both North Carolina water quality
standards for 56 non-consecutive days from June 18 to September 14 (Table 7-2 and Figure 7-2).
7-8
Section 7 2007 Water Quality Results
Instantaneous DO concentrations below 4.0 mg/L and daily average concentrations below
5.0 mg/L typically did not occurred on the same days. At Station TYCM3, DO concentrations
below 4.0 mg/L occurred on 56 days whereas daily average DO concentrations less than
5.0 mg/L occurred on 24 days from June-September.
At Station TYCM4, DO concentrations were below one or both North Carolina water quality
standards for 46 non-consecutive days from June 1 to September 14 (Table 7-2 and Figure 7-2).
Instantaneous DO concentrations below 4.0 mg/L and daily average DO concentrations less than
5.0 mg/L typically did not occurred on the same days. At Station TYCM4, DO concentrations
below 4.0 mg/L occurred on 45 days whereas daily average DO concentrations below 5.0 mg/L
occurred on 24 days from June-September.
7.1.3 Operational Effects of the Tillery Hydroelectric Plant
Dissolved oxygen concentrations in Reach 1 were affected by algal respiration/photosynthesis
diel cycles, tributary inflow, and power plant operations. The relative degree of algal
respiration/photosynthesis, and tributary inflow effect on DO concentrations compared to power
plant operations could not be readily partitioned out with this monitoring program. Similar to
observations in previous years (Progress Energy 2005b), there were strong diel cycles in DO
concentrations at all monitored stations. This temporal pattern likely reflected the influence of
algal photosynthesis and respiration on DO dynamics at these stations. These diel cycles were
apparent on days of no power plant generation (Figure 7-4). Dissolved oxygen concentrations
typically changed by 4 to 8 mg/L during a 24-hour period at all monitored stations. On days
without power generation, the DO concentrations would begin to rise around dawn; peak during
early afternoon; decrease through the early evening; and then remain low until the next day
(Figure 7-4). When water levels increased with power generation, the DO concentrations
correspondingly decreased. This effect was particularly evident when generation began several
hours after DO concentrations began to rise in the morning hours. Dissolved oxygen
concentrations would then decline to levels just above the pre-dawn concentrations. The diel
response of DO also showed seasonal shifts with greater peaks in DO concentrations during the
days of longer daylight length and warmer temperatures in the warmest months (May-
September) when there was greater photosynthetic activity as opposed to the days of shorter
daylight length, and cooler water temperatures in the cooler periods (early May and October).
7-9
Section 7
6/16/2007
16.0
J
E 12.0
C
8.0
a
x
O 4.0
w
0 0.0 '
0 0:00 4:00 8:00 12:00 16:00 20:00
Time
TYCM1-1 TYCM2 k TYCM3 TYCM4
7/14/2007
16.0
J
bA
E 12.0
C
W
a 8.0
x
O
4.0
0
0 0.0
0:00
2007 Water Quality Results
4:00 8:00 12:00 16:00 20:00
Time
TYCM1-1 TYCM2 A TYCM3 TYCM4
8/5/2007
16.0
J
bA
E 12.0
C
N
X 8.0
O
4.0
0
p 0.0 '
0:00 4:00 8:00 12:00 16:00 20:00
Time
TYCM1-1 TYCM2 a -TYCM3 TYCM4
Figure 7-4 Dissolved oxygen concentrations (mg/L) on select days (June 16, July 14 and
August 5) with no power plant generation at Stations TYCM1-1, TYCM2,
TYCM3 and TYCM4.
7-10
Section 7
2007 Water Quality Results
Even on days when no power generation occurred, the DO concentrations were not always high
enough to meet both North Carolina water quality standards at Station TYCM1-1, and TYCM1-2
in early August (Table 7-3). From May 1 to October 31, the number of days without any power
generation during a 24-hour period at the Tillery Hydroelectric Plant totaled 26 days. Of these
26 days, daily mean DO concentrations were less than 5.0 mg/L on 8 days at Station TYCM1-1;
1 day at Station TYCM3: and 3 days at Station TYCM4. Dissolved oxygen concentrations below
4.0 mg/L occurred on 14 days at Station TYCM1-1; 12 days at Station TYCM2; 6 days at Station
TYCM3; and 4 days at Station TYCM4 (Table 7-3). These results indicated that algal
respiration, tributary inflow, and/or wicket gate leakage from the power plant influenced DO
dynamics during non-generation periods.
7-11
Section 7 2007 Water Quality Results
Table 7-3 Days that no power was generated at the Tillery Hydroelectric Plant and
assessments of dissolved oxygen concentrations at stations in Reach 1 to
determine if they met the North Carolina water quality standards for daily
average and instantaneous dissolved oxygen concentrations during 2007.+
Reach 1 Stations
TYCMI-1 TYCM2 TYCM3 TYCM4
< 5.0 < 4.0 < 5.0 < 4.0 < 5.0 < 4.0 < 5.0 < 4.0
Date mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L

May 13
May 19
May 27 X X
May 29 X X X
June 16 X
June 24 X X
June 30 X X
July 4 X X X X X
July 14 X X
July 21 X X X X X
July 22 X X
July 28 X X X X X X X
August 4 X X X X X X
August 5 X
September 2 X X X X
September 8 X X
September 15 X X
September 16 X X
September 28
September 29
October 11
October 13
October 14
October 20
October 27
October 28
Total 8 14 0 12 1 6 3 4
'Days when the daily average DO was < 5.0 mg/L and days when an instantaneous DO concentration was
< 4.0 mg/L are denoted with an "X". Days that the water quality standards were met are not marked.
7-12
Section 7 2007 Water Quality Results
7.1.4 Dissolved Oxygen - Blewett Falls Dam to Below Hitchcock Creek
(Reach 2)
For the May through October study period, instantaneous DO concentrations ranged from 0.1 to
14.3 mg/L at four monitoring stations in Reach 2 (Table 7-4). Mean DO concentrations at these
four stations ranged from 5.3 to 7.3 mg/L for the May through October period (Table 7-4).
Generally, DO concentrations at Stations within Reach 1 decreased during May and June;
remained low during July and August; and increased during early September through October
(Figure 7-5).
Weekly average DO concentrations were usually lowest at Stations BFCMIA and BFCM2.
Generally, the weekly average DO concentrations at the four stations differed by less than 3.0
mg/L. Weekly average DO concentrations followed a similar spatial trend throughout the
monitoring period. Weekly average DO concentrations were lowest at Stations BFCMIA and
BFCM2 during the mid to late part of August.
7-13
Section 7
2007 Water Quality Results
Table 7-4 Dissolved oxygen concentration summary for Reach 2 of the Pee Dee River
below the Blewett Falls Hydroelectric Plant, May 1 to October 31, 2007.

Dissolved Oxygen (DO) Variable
BFCMl Reach 2 stations
BFCNIIA BFCM2
BFCM3
Mean DO (mg/L) ¶ 6.2 5.9 5.3 7.3
Range of DO (mg/L) 1.4-11.5 0.5-13.5 0.1-10.7 2.4-14.3
Percent of DO concentrations < 5.0 mg/L 24.9% 38.4% 45.5% 19.7%
Percent of DO concentrations < 4.0 mg/L 9.5% 16.6% 25.8% 4.9%
Percent of DO concentrations < 3.0 mg/L 1.7% 6.2% 10.9% 0.1%
Percent of DO concentrations < 2.0 mg/L 0.1% 1.7% 5.2% NA+
Date of lowest DO concentration 24-Jul 11-Jul 14-Sep 25-Aug
First DO concentration < 5.0 mg/L 21-May 3-May 6-May 27-May
Last DO concentration < 5.0 mg/L 18-Oct 24-Oct 27-Oct 10-Oct
First DO concentration < 4.0 mg/L 1-Jun 29-May 29-May 7-Jun
Last DO concentration < 4.0 mg/L 11-Oct 16-Oct 11-Oct 25-Aug
First DO concentration < 3.0 mg/L 24-Jun 31-May 7-Jun 21-Aug
Last DO concentration < 3.0 mg/L 28-Sep 5-Sep 2-Oct 25-Aug
First DO concentration < 2.0 mg/L 15-Jul 8-Jul 12-Jul NA+
Last DO concentration < 2.0 mg/L 24-Jul 5-Sep 19-Sep NA+
Longest duration of DO < 5.0 mg/L (hours) 49.0 92.8 39.8 16.0
Start of longest duration of DO < 5.0 mg/L 28-Jul 14-Aug 13-Jul 24-Aug
'NA = Not Applicable.
¶ Mean of all measurements for the monitoring period of May 1 to October 31, 2007.
Dissolved oxygen concentrations < 5.0 mg/L had the greatest occurrences at Stations BFCMIA
and BFCM2 (38.4 and 45.5 % of the DO measurements were < 5.0 mg/L, respectively)
(Table 7-4). Dissolved oxygen concentrations below 5.0 mg/L represented less than 25% of the
measurements at Stations BFCM1 and BFCM3. The percentage of DO concentrations below
4.0 mg/L was the greatest at Stations BFCMIA (16.6%) and BFCM2 (25.8%). Frequency
distributions indicated that Station BFCM2 had the most DO concentrations < 3.0 mg/L, while
Station BFCM3 had the most DO concentrations > 9.0 mg/L (Figure 7-6).
7-14
Section 7
11
10
9
_ 8
E 7
N
6
X
O 5
a?
4
0
p 3
2007 Water Quality Results
Blemett Falls Reach 2 - 2007
2
1
0?
05/01/07
06/01107 07101107 08101107 09/01/07 001107
Date
BFCM1 - BFCM1A - BFCM2 BFCM3
11/01/07
Figure 7-5 Weekly mean dissolved oxygen concentrations at continuous monitor stations
in Reach 2 of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2007.
M
7-15
Section 7
2007 Water Quality Results
Blejnett Falls Reach 2 - 2007
25
20
c
a?
15
CL
c
a?
10
Cr
a?
L
LL
5
0
BFCM1 IIIIIIi BFCM1A IIIIIIi BFCM2 BFCM3
Figure 7-6 Frequency distributions of dissolve oxygen concentrations at continuous
monitor stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, May 1 to October 31, 2007.
Dissolved oxygen concentrations in Reach 2 initially declined below 5.0 mg/L on May 3 at
Station BFCMIA (Table 7-4). Dissolved oxygen concentrations below 5.0 mg/L were recorded
in Reach 2 until October 27 at Station BFCM2 (Table 7-4). Instantaneous DO concentrations
below 4.0 mg/L persisted into October at all stations except BFCM3.
The minimum DO concentration for Reach 2 was 0.1 mg/L at Station BFCM2 (Table 7-4). The
lowest DO concentrations occurred at all stations during the late July to late August period. The
longest duration of DO concentrations below 5.0 mg/L also occurred during this time period.

Ja il ? I II L? . .
0-1 1-2 2-3 34 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-14 14-15
Dissolved Oxygen (mg1L)
7-16
Section 7
2007 Water Quality Results
7.1.5 North Carolina Water Quality Standards for DO in Reach 2
Dissolved oxygen concentrations at Stations in Reach 2 were below one or both North Carolina
water quality standards for at least 42 days from May through October, depending on the station
(Table 7-5). All four stations had DO concentrations < 4.0 mg/L and daily average DO
concentrations < 5.0 mg/L during this period (Figure 7-7). Daily average DO concentrations
were below the water quality standard for some days in Reach 2 from May 29 to October 10.
Dissolved oxygen concentrations below the water quality standard 4.0 mg/L were recorded on
some days in Reach 2 beginning May 29 and ending October 16. Dissolved oxygen
concentrations were below one or both North Carolina water quality standards at Station BFCM3
on 42 days, the fewest of any stations in Reach 2.
Table 7-5 Assessments of daily dissolved oxygen concentrations from May 1 to October
31, 2007 at stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant compared to the North Carolina dissolved oxygen water
quality standards.
Reach 2 Station
North Carolina Water Quality Standard Variable BFCMI BFCMIA BFCM2 BFCM3
Daily average DO (5.0 mg/L)
Number of days not meeting standard 52 58 106 2
First day standard was not met 11-Jun 29-May 29-May 6-Aug
Last day standard was not met 26-Sep 12-Sep 10-Oct 25-Aug
Instantaneous DO (4.0 mg/L)
Number of days not meeting standard 67 92 119 41
First day standard was not met 1-Jun 29-May 29-May 7-Jun
Last day standard was not met 11-Oct 16-Oct 11-Oct 25-Aug
Number of days either standard was not met+ 71 93 121 42
Number of days assessed¶ 202 214 214 204
+ The total number of days that one or both of the North Carolina water quality standards for daily average
(5.0 mg/L) and instantaneous (4.0 mg/L) DO concentrations were not met.
¶ The number of days assessed was the total number of days from May 1 to October 31 when DO concentrations
were recorded for at least half of the day.
7-17
Section 7
Blewett Falls Reach 2, Station CM1 - 2007
15
14
13
12
11
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2007 Water Quality Results

051`01/2007 06/01/2007 07/01/2007 08/01/2007 09/01/2007 10/01/2007 11/01/2007 12101/2007
Date
Blewett Falls Reach 2, Station CM1A - 2007
15-
14-
13-
12-
11
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v 7
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0 5
4
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051`01/2007 06/01/2007 07/01/2007 08/01/2007 091`01/2007 101`01/2007 11/01/2007 12101/2007
Date
Figure 7-7 Daily averages (black line) and ranges (vertical bars) of dissolved oxygen
concentrations at Stations BFCM1, BFCMIA, BFCM2, and BFCM3 in
Reach 2 of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to November 30, 2007.
7-18
Section 7
Blevwd Falls Reach 2, Station CM2 - 2007
15
14
13
12
11
J 10
a?
E
9
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a? 8
xx
O 7
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y 5
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2007 Water Quality Results
05/01/2007 06/01/2007 07/01/2007 08/01/2007 09/01/2007 10/01/2007 11/01/2007 12101/2007
Date
Blewett Falls Reach 2, Station CM3 - 2007
15
14
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05?01/2007 06/01/2007 07/01/2007 08/01/2007 09/01/2007 10/01/2007 11/01/2007 12/0112007
Date
Figure 7-7 (continued).
7-19
Section 7 2007 Water Quality Results
At Station BFCM1, DO water quality standards were not met for 71 days between June 1 and
October 11 (Table 7-5 and Figure 7-7). The daily average DO concentration was below
5.0 mg/L on 52 days from June 11 to September 26. Instantaneous DO concentrations were
below 4.0 mg/L on 67 days between June 1 and October 11.
At Station BFCMIA, the DO water quality standards for 93 days starting on May 29 and ending
on October 16 (Table 7-5 and Figure 7-7). The daily average DO concentration was below
5.0 mg/L on 58 days between May 29 and September 12. Instantaneous DO concentrations were
below 4.0 mg/L on 92 days between May 29 and October 16.
Dissolved oxygen concentrations were below the water quality standards on more days at Station
BFCM2 than the other stations. Dissolved oxygen concentrations were below water quality
standards for a total of 121 days. At Station BFCM2, daily average DO concentrations were less
than 5.0 mg/L for 106 days (May 29 through October 10). Instantaneous DO concentrations were
below 4.0 mg/L on 119 days (May 29 through October 11) (Table 7-5 and Figure 7-7).
At Station BFCM3, DO concentrations were below the North Carolina water quality standards
for 42 non-consecutive days from June 7 to August 25 (Table 7-5 and Figure 7-7). For 41 of the
42 days, the DO concentrations were below 4.0 mg/L. Daily average DO concentrations were
< 5.0 mg/L for 2 days beginning August 2 and ending August 25. Instantaneous DO
concentrations were less than 4.0 mg/L for 41 days beginning August 6 and ending August 25.
7.1.6 Operational Effects of the Blewett Falls Hydroelectric Plant
On days when no power generation occurred, the DO concentrations were not always high
enough to meet both North Carolina water quality standards at all monitored stations. From
May 1 to October 31, the number of days without any power generation during a 24-hour period
at the Blewett Falls Hydroelectric Plant totaled 9 days. Of these 9 days, daily average DO
concentrations were < 5.0 mg/L on 5 days at Station BFCM1; and 8 days at station BFCM2.
Dissolved oxygen concentrations < 4.0 mg/L occurred on 7 days at Station BFCM1; 5 days at
station BFCMIA; 8 days at station BFCM2; and 7 days at station BFCM3 (Table 7-6). Algal
respiration, tributary inflow, and/or wicket gate leakage from the power plant likely influenced
DO dynamics during these few non-generation periods.
7-20
Section 7
2007 Water Quality Results
Table 7-6 Days that no power was generated at the Blewett Falls Hydroelectric Plant
and assessments of dissolved oxygen concentrations at stations in Reach 1 to
determine if they met the North Carolina water quality standards for daily
average and instantaneous dissolved oxygen concentrations during 2007.+
Reach 1 Station
BFCMI BFCMIA BFCM2 BFCM3
< 5.0 < 4.0 < 5.0 < 4.0 < 5.0 < 4.0 < 5.0 < 4.0
Date mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L
30-June X X
4-July X X X
14-July X X X X X
15-July X X X X X X
21-July X X X X
22-July X X X X
23-July X X X X X X
28-July X X X X X
29-July X X X X X
Total 5 7 0 5 8 8 0 7
'Days when the daily average DO was < 5.0 mg/L and days when an instantaneous DO concentration was
< 4.0 mg/L are denoted with an "X". Days that the water quality standards were met are not marked.
7.2 Water Temperature in the Pee Dee River
7.2.1 Reach 1 - Tillery Dam to Turkey Top Creek
Water temperatures ranged from 10.0 to 33.7°C in Reach 1 from May through October
(Table 7-7). Mean water temperatures in Reach 1 from May through October ranged from
23.2°C at Station TYCM1-1 to 24.3°C at Station TYCM4 (Table 7-7). The Reach 1 maximum
instantaneous temperature of 33.7°C occurred at Station TYCM2 on August 8 and Station
TYCM4 on August 9. Weekly mean temperatures were generally lower at Station TYCM1-1
than the other stations from May through July (Figure 7-8). Weekly mean temperatures at
Station TYCM1 were more similar to the other stations from August to October. Weekly mean
temperatures were similar at the other stations and usually slightly greater at Station TYCM4.
7-21
Section 7 2007 Water Quality Results
Table 7-7 Summary statistics of water quality variables from stations in Reach 1 of the
Pee Dee River below the Tillery Hydroelectric Plant, May 1 to October 31,
2007.

Water Quality Variable
TYCMl-1 Reach 1 Station
TYCM2 TYCM3
TYCM4
Mean temperature (°C) 23.2 23.5 24.0 24.3
Temperature range (°C) 13.2-30.2 10.0-33.7 10.2-32.8 10.6-33.7
Median pH 6.8 7.0 7.2 7.2
pH range 6.1-9.3 6.0-10.1 6.2-9.3 6.2-9.6
Mean specific conductance (p S/cm) 97 97 114 118
Specific conductance range (pS/cm) 81-114 75-122 84-328 87-314
30
Tillery Reach 1 - 2007
a?
C9
R
L
P
LV
U
rn
N
N
L
L
10
L
Q
E
0i
0&01/07
06/01/07 07/01/07 08101/07 09/01/07 10/01/07
Date
e e a TYCM1-1 TYCM2 TYCM3 TYCIM
11/01/07
Figure 7-8 Weekly mean temperatures at continuous monitor stations in Reach 1 of the
Pee Dee River below the Tillery Hydroelectric Plant, May 1 to October 31,
2007.
7-22
Section 7 2007 Water Quality Results
Temperature values greater than the North Carolina water quality standard of 32°C were most
often observed at Station TYCM2 during July and August. Infrequent excursions above 32°C
were noted at Stations TYCM3 and TYCM4. Temperature measurements greater than 32°C at
Station TYCM2 accounted for approximately 2% (n = 407) of the total number of instantaneous
temperature measurements at this Station (n = 20,256 measurements). There were 248
measurements that were greater than 32°C at Station TYCM4 (n = 20,064) and 31 measurements
that were greater than 32°C at Station TYCM3 (n = 19,872).
7.2.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek
Water temperatures ranged from 9.1 to 35.9°C at from May through October in Reach 2
(Table 7-8). Mean water temperatures ranged from 24.3°C at BFCM3 to 24.7°C at BFCMIA
(Table 7-8). The maximum instantaneous temperature of 35.9°C occurred at Station BFCM3 on
August 10.
Weekly average water temperatures at all four stations were similar throughout the monitoring
(Figure 7-9). Weekly mean temperatures peaked around 30°C at all stations during the last
week of July.
Table 7-8 Summary statistics of water quality variables from stations in Reach 2 of the
Pee Dee River below the Blewett Falls Hydroelectric Plant, May 1 to October
31, 2007.
Reach 2 Station
Water Quality Variable BFCMI BFCMIA BFCM2 BFCM3
Mean temperature ff) 24.6 24.7 24.5 24.3
Temperature range ff) 12.5-32.0 10.6-33.4 10.9-33.0 9.1-35.9
Median pH 7.1 7.2 7.0 7.3
pH range 6.5-8.9 6.2-9.3 6.5-8.7 6.7-9.7
Mean specific conductance (pS/cm) 115 116 116 114
Specific conductance range (pS/cm) 91-153 25-154 92-153 86-185
7-23
Section 7
Blewett Falls Reach 2 - 2007
40
a?
30
LM
a?
U
U)
d
d
L 20
d
d
L
L
d
E 10
d
H
2007 Water Quality Results
04----
0501/07
06101107 07101107 08101107 09/01107 10/01107 11101107
Date
- BFCM1 - BFCM1A - BFC1W BFCM3
Figure 7-9 Weekly mean temperatures at continuous monitor stations in Reach 2 of the
Pee Dee River below the Blewett Falls Hydroelectric Plant, May 1 to October
31, 2007.
Temperature values greater than the North Carolina water quality standard of 32°C were most
often observed at Station BFCM3 during July and August. Infrequent excursions above 32°C
were noted at Stations BFCM1, BFCMIA, and BFCM2. Temperature measurements greater
than 32°C at Station BFCM3 accounted for less than 2.5% (n = 477) of the total number of
measurements at this station (n = 19,721). There were 54 measurements that were > 32°C at
Station BFCMIA (n = 20,256); 38 measurements that were > 32°C at Station BFCM2
(n = 20,160); and 2 measurements that were > 32°C at Station BFCM1 (n = 20,352).
7.3 pH in the Pee Dee River
7.3.1 Reach 1 - Tillery Dam to Turkey Top Creek
Median pH values at stations in Reach 1 were slightly acidic to near neutral (6.8 to 7.2) for the
monitoring period (Table 7-7). Instantaneous pH values ranged from 6.0 to 10.1. Weekly mean
pH values ranged from 6.3 to 8.0 at all stations (Figure 7-10). Station TYCM1-1 typically had
the lowest weekly mean pH values while Stations TYCM2 and TYCM4 usually had higher
weekly mean pH values. There was variation in weekly mean pH values.
7-24
Section 7
9
8
7
6
5
2
Q
4
3
2
1
0
05/01/07
06101107 07101107 08101107 09101107 V01107
Date
- - - TYCM1-1 n TY(IVI2 , ?, , TYCM3 T
11/01/07
Figure 7-10 Weekly mean pH values at continuous monitor stations in Reach 1 of the Pee
Dee River below the Tillery Hydroelectric Plant, May 1 to October 31, 2007.
The daily pH values fluctuated considerably at Station TYCM2 and values often exceeded 9.0,
particularly during May. These instantaneous pH values exceeded the upper limit (9.0) of the
North Carolina water quality standard for pH (NCDWQ 2007). Approximately 10.0% of the
total number of pH measurements (n = 20,256) at Station TYCM2 exceeded 9.0. Instantaneous
pH values > 9.0, occurred less than 1% at the other monitoring stations. These pH fluctuations at
Station TYCM2 corresponded with DO trends, a likely result of algal photosynthesis and
respiration (Figure 7-11).
2007 Water Quality Results
Tillery Reach 1 - 2007
7-25
Section 7
18
16
14
J
by
E 12
c
10
a
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0 6
4
2
2007 Water Quality Results
i 12
10
8
6 a

4

2
0
0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00
Time
Dissolved Oxygen pH
0
Figure 7-11 Dissolved oxygen concentrations and pH values at Station TYCM2 in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 14
to 21, 2007.
7.3.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek
Median pH values at stations in Reach 2 were near neutral (7.0 to 7.3) for the monitoring period
(Table 7-8). Instantaneous pH values ranged from 6.2 at Station BFCMIA to 9.7 at Station
BFCM3. Weekly mean pH values ranged from 6.5 to 7.9 (Figure 7-12). Generally, Station
BFCM3 had greater weekly mean pH values more often than the other stations. There was also
more daily variation in pH values at Station BFCM3 due to the greater amount of algal growth
and subsequent photosynthesis and respiration (Table 7-8).
7-26
Section 7
Blevw ft Falls Reach 2 - 2007
9
2
Q
4
2007 Water Quality Results
0-1----
0501/07
=01107 07101107 =01107 09101107 10/01107
Date
ewe BFCM1 - BFCM1A ° ° BFCM2 BFCM3
11/01/07
Figure 7-12 Weekly mean pH values at continuous monitor stations in Reach 2 of the Pee
Dee River below the Blewett Falls Hydroelectric Plant, May 1 to October 31,
2007.
Approximately 7.2 percent of the total number of instantaneous pH values (n = 19,872) at Station
BFCM3 exceeded the North Carolina water quality standard of 9.0. Instantaneous pH values
> 9.0, occurred less than 1% of the total measurements (n = 20,256) at Station BFCMIA.
7.4 Specific Conductance in the Pee Dee River
7.4.1 Reach 1 - Tillery Dam to Turkey Top Creek
Mean specific conductance values for stations within Reach 1 from May through October ranged
from 97 µS/cm to 118 µS/cm (Table 7-7). Instantaneous specific conductance values ranged
from 81 to 328 µS/cm. Weekly mean specific conductance values were always greater at
Stations TYCM3 and TYCM4 than at Stations TYCM1 and TYCM2 (Figure 7-13).
Weekly specific conductance values approached 160 µS/cm at Stations TYCM3 and TYCM4
while weekly specific conductance values at Stations TYCM1 and TYCM2 were below 110
µS/cm (Figure 7-13). The Rocky River and Brown Creek enter the Pee Dee River between
7-27
Section 7 2007 Water Quality Results
Stations TYCM2 and TYCM3, and high specific conductance in the Rocky River has been
documented by the NCDWQ (2010) and Progress Energy (2003, 2006a). Stations TYCM3 and
TYCM4 were influenced by Rocky River and Brown Creek inflow, as evidenced by greater
specific conductance values.
Tillery Reach 1- 2007
16(
150
140
130
E 120
110
a? 100
CU 90
80
3
70
0
U 60
50
C 40
N
30
20
10
0?
05/01/07
06/01107 07101107 08101107 09101107 1001107
Date
e e ? TYCM1-1 El El El TYCIM ? TYCIM TYCM4
11/01/07
Figure 7-13 Weekly mean specific conductance values at continuous monitor stations in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
October 31, 2007.
7.4.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek
Mean specific conductance values in Reach 2 ranged from 114 to 116 µS/cm from May through
October (Table 7-8). Instantaneous specific conductance values ranged from 25 to 185 µS/cm.
Weekly mean specific conductance values at each Station showed similar temporal trends during
the monitoring period (Figure 7-14). Generally specific conductance measurements increased
from May through October and likely reflected less rainfall and inflow into the river basin.
7-28
Section 7
150
140
130
E
2007 Water Quality Results
Blewett Falls Reach 2 - 2007
110
N
100
d
90
C
80
3
70
C
0 60
U
w 50
40
Q
N 30
20
10
0?
05101/07
06/01/07 07/01/07 =01107 001/07 001/07
Date
o BFCM1 El El El BFCM1A ?? BFCM2 BFCM3
11/01/07
Figure 7-14 Weekly mean specific conductance values at continuous monitor stations in
Reach 2 of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2007.
120
7-29
Section 8 - 2008 Water Quality Results
8.1 Water Quality in the Pee Dee River, 2008
8. 1.1 Dissolved Oxygen - Tillery Dam to Turkey Top Creek (Reach 1)
During the May through October monitoring period, instantaneous DO concentrations in Reach 1
ranged from 0.6 to 17.1 mg/L at the six monitoring stations in Reach 1 (Table 8-1). Mean DO
concentrations ranged from 4.7 to 7.6 mg/L for the May through October period (Table 8-1).
Throughout Reach 1, DO concentrations exhibited a seasonal trend by decreasing during May
and June; remaining low during July and August; rising during early September; and fluctuating
during September and early October; and then rising in mid and late October (Figure 8-1).
Dissolved oxygen concentrations were <1.0 mg/L on August 8 and 30 at Station TYCM1-1.
However, these DO concentrations below 1.0 mg/L only occurred for a short period (< 1% of
total observations) of time. At Station TYCM1-2 and TYCM1-3, the lowest DO concentrations
occurred throughout July and August (Figure 8-2). At station TYCM1-3, the lowest DO
concentration (1.1 mg/L) occurred on August 11 (Table 8-1). At Station TYCM2, DO
concentrations were low throughout August, but the lowest DO concentration occurred on
August 28 (1.8 mg/L). During the limited sampling period of May to mid June at Stations
TYCM3 and TYCM4, DO concentrations never dropped below 5.0 mg/L (Figure 8-2).
Dissolved oxygen concentrations throughout Reach 1 fluctuated widely on most days during the
study period (Figure 8-2). These fluctuations were most apparent at Station TYCM2 where daily
DO concentrations often fluctuated by more than 10 mg/L during May. Dissolved oxygen
concentrations at Station TYCM2 were often supersaturated (200% saturation) and exceeded
17 mg/L on some occasions during May. Station TYCM2 was the shallowest of the monitoring
stations, and the range of flows, coupled with diurnal fluctuations associated with algal
photosynthesis and respiration, likely contributed to these DO conditions.
8-1
Section 8
2008 Water Quality Results
Table 8-1 Dissolved oxygen concentration summary for Reach 1 of the Pee Dee River
below the Tillery Hydroelectric Plant, May 1 to October 31, 2008.
Reach 1 Stations
Dissolved Oxygen (DO) Variable TYCM1-1 TYCM1-2¶ TYCM1-3¶ TYCM2 TYCM3¥ TYCM4¥
Mean DO (mg/L)§ 5.1 4.7 5.8 6.8 7.2 7.6
Range of DO (mg/L) 0.6-12.6 1.2-11.6 1.1-14.4 1.8-17.1 5.1-11.9 5.3-11.0
Percent of DO concentrations < 5.0 mg/L 47.1% 62.5% 47.0% 35.9% NA+ NA+
Percent of DO concentrations < 4.0 mg/L 37.0% 50.8% 37.0% 17.0% NA+ NA+
Percent of DO concentrations < 3.0 mg/L 24.6% 31.3% 18.2% 2.0% NA+ NA+
Percent of DO concentrations < 2.0 mg/L 3.3% 5.5% 2.6% 0.1% NA+ NA+
Date of lowest DO concentration 30-Aug 26-Jul 11-Aug 28-Aug 28-May 10-Jun
First DO concentration < 5.0 mg/L 10-May 12-Jun 12-Jun 15-May NA+ NA+
Last DO concentration < 5.0 mg/L 9-Oct 11-Oct 17-Oct 10-Oct NA+ NA+
First DO concentration < 4.0 mg/L 30-May 12-Jun 12-Jun 7-Jun NA+ NA+
Last DO concentration < 4.0 mg/L 11-Sep 21-Sep 23-Sep 18-Sep NA+ NA+
First DO concentration < 3.0 mg/L 14-Jun 13-Jun 13-Jun 4-Jul NA+ NA+
Last DO concentration < 3.0 mg/L 11-Sep 16-Sep 16-Sep 14-Sep NA+ NA+
First DO concentration < 2.0 mg/L 29-Jun 4-Jul 23-Jun 28-Aug NA+ NA+
Last DO concentration < 2.0 mg/L 31-Aug 31-Aug 1-Sep 28-Aug NA+ NA+
Longest duration of DO < 5.0 mg/L (hours) 49.8 22.5 21.0 44.0 NA+ NA+
Start of longest duration of DO < 5.0 mg/L 29-Aug 11-Sep 9-Sep 27-Aug 27-Aug 27-Aug
+NA = Not Applicable
¶ Sample period June 12 - October 31, 2008.
¥ Sample period May 1 - June 12, 2008.
§ Mean of all measurements for the monitoring period of May 1 to October 31, 2008.
8-2
Section 8
Tillery Reach 1 - 2008

1^
1
1
J
a?
X
O
a?
0
0
2008 Water Quality Results
1
D
9--
3--
2--
0601/08 06/01/08 07/01/08 08/01/00 09/01100 001/08 11/01/00
Date
e ?e TYC M1-1 ?e TYC M1-2 TYC M1-3 TYC M2 T T T TYC M3 TYC M4
Figure 8-1 Weekly mean dissolved oxygen concentrations at continuous monitor stations
in Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 1
to October 31, 2008.
8-3
Section 8
Tillery Reach 1, Station CM1-1 - 2008
19
18
17
16
15
14
13
12
11
a 10
X
O 9
> 8
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6
5
4
3
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2008 Water Quality Results

05/01/2008 06/01/2008 07/01/2008 08/01/2008 09/01/2008 10/01/2008
Date
Tillery Reach 1, Station CM1-2 - 2008
19
18
17
16
15
14
J 13
E 12
? 11
d
>' 10
X
O 9
v
> 8
0
rn 7
C3 6
5
4
3
2
1
O
11/01/2008
06/01/2008 07/01/2008 08/01/2008 09/01/2008 10/01/2008 11/01/2008
Date
Figure 8-2 Daily averages (black line) and ranges (vertical bars) of dissolved oxygen
concentrations at Stations TYCM1-1, TYCM1-2, TYCM1-3, TYCM2,
TYCM3, and TYCM4 in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant, May 1 to October 31, 2008.
8-4
Section 8
Tillery Reach 1, Station CM1-3 - 2008
19
18
17
16
15
14
J 13
E 12
? 11
>, 10
x
O g
v
> 8
0
m 7
Mn
0 6
5
4
3
2
1
O
2008 Water Quality Results
06/01/2008 07/01/2008 08/01/2008 09/01/2008 10/01/2008 11/01/2008
Date
19-
18-
17-
16-
15-
14-
13-
E 12-
C 11
d
a lo-
x
O g-
8-
0
N 7
N_
0 6
5
4
3
2
1
O
05?01/2008
06/01/2008 07/01/2008 08/01/2008 09/01/2008 10101/2008 11/01/2008
Date
Figure 8-2 (continued).
8-5
Tillery Reach 1, Station CM2 - 2008
Section 8
Tillery Reach 1, Station CM3 - 2008
19
18
17
16
15
14
J 13
E 12
? 11
a 10
x
O 9
> 8
N 7
N_
0 6
5
4
3
2
1
0
2008 Water Quality Results
04127/2008 050412008 05?11/2008 OS1812008 05?25?2008 06/01/2008 06/08/2008 06/15?2008
Date
Tillery Reach 1, Station CM4 - 2008
19
18
17
16
15
14
3 13
E 12
? 11
a 10
x
O 9
> 8
0
v! 7
N
0 6
5
4
3
2
1
0
M18/2008 05?25?2008 06/01/2008 06/08/2008 06/15?2008
Date
Figure 8-4 (continued).
8-6
Section 8
2008 Water Quality Results
Weekly mean DO concentrations varied throughout Reach 1 (Figure 8-1). However, weekly
mean DO concentrations for Station TYCM1-1, TYCM1-2, and TYCM1-3 were typically lower
than at the other stations downstream.
Station TYCM1-2 had more instantaneous DO concentrations below 4.0 mg/L (50.8%) than
other stations in Reach 1 (17.4 to 37.0%) (Table 8-1, Figures 8-3 and 8-4). Frequency
distributions of DO concentrations for Stations TYCM3 and TYCM4 were similar
(Figures 8-3 and 8-4). Station TYCM1-2 also had a higher percentage of DO concentrations
< 5.0 mg/L when compared to the other Reach 1 stations (Figures 8-3 and 8-4). Station TYCM2
differed from other stations with a wider distribution of DO concentrations, including a greater
percentage of DO concentrations greater than 10.0 mg/L (Figures 8-3 and 8-4).
TilleryReach 1- 2008
35
30
25
C
a?
L
a 20
4) 15
n
Cr
a?
L
U- 10
5
0
? TYCM1-1 ? TYCM2 ? TYCM3 TYCM4
Figure 8-3 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant, May 1 to June 11, 2008.
0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 94010411142124313-1414-1515-1616-1717-18
Dissolved Oxygen (mglL)
8-7
Section 8
2008 Water Quality Results
TilleryReach 1- 2008
35
30
25
a?
L
d 20
L
o 15
3
rr
d
L
LL 10
5
0
TYCM1-1 ? TYCM1 2 ? TYCM1-3 TYCM2
Figure 8-4 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant, June 11 to October 31, 2008.
The percentage of instantaneous DO concentrations below 5.0 mg/L in Reach 1 generally
decreased with increased distance from the Tillery Hydroelectric Plant. Approximately 47% of
the instantaneous DO concentrations recorded at Station TYCM1-1 from May through October
were less than 5.0 mg/L (Table 8-1). The percent of DO concentrations <5.0 mg/L decreased to
36% at Station TYCM2.
In Reach 1, instantaneous DO concentrations first decreased < 5.0 mg/L on May 10 at Station
TYCM1-1 (Table 8-1). Dissolved oxygen concentrations below 5.0 mg/L were recorded on
many days at stations in Reach 1 through October. The last DO concentration <5.0 mg/L in
Reach 1 was recorded at Station TYCM1-3 on October 17.
The lowest recorded instantaneous DO concentration during the study period was 0.6 mg/L at
Station TYCM1-1. Dissolved oxygen concentrations remained below 5.0 mg/L for over two
consecutive days at Stations TYCM1-1 and for nearly two consecutive days at Station TYCM2
(Table 8-1).
0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 1142 12-13 13-14 14-15
Dissolved Oxygen (mg/L)
8-8
Section 8
2008 Water Quality Results
8.1.2 North Carolina Water Quality Standards for DO in Reach 1
The North Carolina water quality standards for DO require a daily average DO concentration of
at least 5.0 mg/L and all instantaneous DO concentrations must be at least 4.0 mg/L (NCDWQ
2007). Dissolved oxygen concentrations were below one or both North Carolina water quality
standards at all four stations in Reach 1 for varying periods of time during 2008. The water
quality standards were not met from 78 to 95 days from June through October, depending on the
station (Table 8-2 and Figure 8-2). The period during which the water quality standard for daily
average DO of 5.0 mg/L was not met in Reach 1 extended from June 12 to October 8 at Station
TYCM1-1. Instantaneous dissolved oxygen concentrations <4.0 mg/L initially occurred on May
30 and persisted through September 23 (Table 8-2).
Table 8-2 Assessments of daily dissolved oxygen concentrations from May 1 to October
31, 2008 at stations in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant compared to the North Carolina dissolved oxygen water
quality standards.

North Carolina Water Quality
Standard

TYCM1-1

TYCM1-2+ Reach 1 Stations

TYCMI-3+ TYCM2

TYCM31

TYCM41
Daily average DO (5.0 mg/L)
Number of days not meeting 79 80 29 10 0 0
standard
First day standard was not met 12-Jun 12-Jun 23-Jun 26-Jun
Last day standard was not met 8-Oct 17-Sep 15-Sep 14-Sep
Instantaneous DO (4.0 mg/L)
Number of days not meeting 94 91 93 77 0 0
standard
First day standard was not met 30-May 12-Jun 12-Jun 7-Jun
Last day standard was not met 11-Sep 21-Sep 23-Sep 18-Sep
Number of days either standard was
95
91
93
78
0
0
not met*
Number of days assesse& 161 110 134 169 42 23
+ Sample period June 12 - October 31, 2008.
¶ Sample period May 1 - June 12, 2008.
¥ The total number of days that one or both of the North Carolina water quality standards for daily average
(5.0 mg/L) and instantaneous (4.0 mg/L) DO concentrations were not met.
§ The number of days assessed was the total number of days from May 1 to October 31 when DO concentrations
were recorded for at least half of the day.
8-9
Section 8 2008 Water Quality Results
Dissolved oxygen concentrations were below one or both of the North Carolina water quality
standards more frequently at Station TYCM1-l. At Station TYCM1-1, DO concentrations were
below one or both water quality standards on 95 non-consecutive days from June to October
(Table 8-2 and Figure 8-2). Dissolved oxygen concentrations were below one or both water
quality standards at Station TYCM1-1 for 11 days prior to TYCM1-2, and TYCM1-3 being
deployed in early June. At Station TYCM1-1, DO concentrations < 4.0 mg/L and daily average
concentrations < 5.0 mg/L usually occurred on the same days.
At Station TYCM1-2, DO concentrations were below one or both water quality standards for 91
non-consecutive days from June 12 to September 21 (Table 8-2 and Figure 8-2). Dissolved
oxygen concentrations < 4.0 mg/L and daily average concentrations < 5.0 mg/L usually occurred
on the same days.
At Station TYCM1-3, DO concentrations were below one or both North Carolina water quality
standards for 93 non-consecutive days from June 12 to September 23 (Table 8-2 and Figure 8-2).
Instantaneous DO concentrations < 4.0 mg/L and daily average concentrations < 5.0 mg/L
typically did not occurred on the same days.
At Station TYCM2, DO concentrations were below one or both North Carolina water quality
standards for 78 non-consecutive days from June 7 to September 18 (Table 8-2 and Figure 8-2).
For 77 of the 78 days, the instantaneous water quality standard or 4.0 mg/L was not met. Daily
average DO concentrations were < 5.0 mg/L for 10 days beginning June 26 and ending
September 14.
8.1.3 Operational Effects of the Tillery Hydroelectric Plant
Similar to observations in previous monitoring years, concentrations in Reach 1 were affected in
varying degrees by natural diel cycles, tributary inflows and power plant operations. There was a
strong diel cycles in instantaneous DO concentrations at all monitored stations (Progress Energy
2005b, 2006d, this report). This temporal pattern reflected the influence of algal photosynthesis
and respiration dynamics on DO concentrations. This diel cycle was apparent on days of no
power plant generation (Figure 8-5). Dissolved oxygen concentrations typically changed by 4 to
8 mg/L during a 24-hour period at the monitored stations. On days without power generation, the
DO concentrations would begin to rise around dawn; peak during early afternoon; decrease
through the early evening; and then remain low until the next day (Figure 8-5). When water
levels increased with power generation, the DO concentrations correspondingly decreased. This
effect was particularly evident when generation began several hours after DO concentrations
began to rise in the morning hours. Dissolved oxygen concentrations would then decline to
levels just above the pre-dawn concentrations. The diel response of DO also showed seasonal
shifts with greater peaks in DO concentrations during the days of longer daylight length and
higher water temperatures in the warmer months (May-September) when there was greater
photosynthetic activity as opposed to the days of shorter daylight length and lower water
temperatures in the cooler months (early May and October).
8-10
Section 8
14
12
E 10
c
w 8
a
x
O
6
w
0 4
0
2
0
2008 Water Quality Results
0:00 6:00 12:00 18:00 0:00 6:00 12:00 18:00
Time
I TYCM1-1 TYCM1-2 TYCM1-3 TYCM2
Figure 8-5 Dissolved oxygen concentrations (mg/L) on select days (August 1-2) with no
power plant generation at Stations TYCM1-1, TYCM1-2, TYCM1-3 and
TYCM4, May 1 to October 31, 2008.
Even on days when no power generation occurred, the DO concentrations were not always high
enough to meet both North Carolina water quality standards at Station TYCM1-1, and TYCM1-2
in early August (Table 8-3). From May 1 to October 31, the number of days without any power
generation during a 24-hour period at the Tillery Hydroelectric Plant totaled 2 days. Of these 2
days, daily mean DO concentrations were less than 5.0 mg/L on 2 days and instantaneous DO
concentrations below 4.0 mg/L occurred on 2 days at Station TYCM1-1, and TYCM1-2
(Table 8-3). These results indicated that algal respiration and/or wicket gate leakage from the
power plant influenced DO dynamics during non-generation periods at Station TYCM1-1 and
TYCM 1-2.
The daily average DO concentration of 5.0 mg/L was met on the 2 non-power generation days at
Stations TYCM1-3 and TYCM2 (Table 8-3). Instantaneous DO concentrations < 4.0 mg/L
occurred on both days at these two stations in August.
8-11
Section 8
2008 Water Quality Results
Table 8-3 Days that no power was generated at the Tillery Hydroelectric Plant and
assessments of dissolved oxygen concentrations at stations in Reach 1 to
determine if they met the North Carolina water quality standards for daily
average and instantaneous dissolved oxygen concentrations during 2008.+
Reach 1 Station
TYCMl-1 TYC M1-2 TYCM1-3 TYCM2
< 5.0 < 4.0 < 5.0 < 4.0 < 5.0 < 4.0 < 5.0 < 4.0
Date mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L
August 1 x x x x x x
August 2 x x x x x x
Total 2 2 2 2 0 2 0 2
'Days when the daily average DO < 5.0 mg/L and days when an instantaneous DO concentration was < 4.0 mg/L
are denoted with an "x". Days that the water quality standards were met are not marked.
8.1.4 Dissolved Oxygen - Blewett Falls Dam to Below Hitchcock Creek
(Reach 2)
For the May through October monitoring period, DO concentrations ranged from 0.1 to 13.0
mg/L at five monitored stations in Reach 2 (Table 8-4). Mean DO concentrations ranged from
4.9 to 7.2 mg/L (Table 8-4). Typical seasonal patterns of high DO concentrations in spring and
fall months and lower DO concentrations in spring occurred during the monitored period
(Figure 8-6).
Weekly average DO concentrations were usually lowest at Stations BFCMIA and BFCM2A.
Generally, the weekly average DO concentrations differed by < 2.0 mg/L. Weekly average DO
concentrations were typically lower at Station BFCMIA during the monitoring period
(Figure 8-6).
8-12
Section 8 2008 Water Quality Results
Table 8-4 Dissolved oxygen concentration summary for Reach 2 of the Pee Dee River
below the Blewett Falls Hydroelectric Plant, May 1 to October 31, 2008.
Dissolved Oxv2en (DO) Variable
Mean DO (mg/L) §
Range of DO (mg/L)
Percent of DO concentrations < 5.0 mg/L
Percent of DO concentrations < 4.0 mg/L
Percent of DO concentrations < 3.0 mg/L
Percent of DO concentrations < 2.0 mg/L
Date of lowest DO concentration
First DO concentration < 5.0 mg/L
Last DO concentration < 5.0 mg/L
First DO concentration < 4.0 mg/L
Last DO concentration < 4.0 mg/L
First DO concentration < 3.0 mg/L
Last DO concentration < 3.0 mg/L
First DO concentration < 2.0 mg/L
Last DO concentration < 2.0 mg/L
Longest duration of DO < 5.0 mg/L
(hours)
Start of longest duration of DO < 5.0
mg/L
Reach 2 Station
BFCMI BFCMIA BFCM2+ BFCM2A¶ BFCM31
5.8 4.9 6.6 5.1 7.2
0.2-10.7 0.1-10.2 1.6-9.6 0.2-10.8 2.7-13.0
32.0% 47.5% 14.8% 48.2% 14.3%
16.8% 32.1% 6.1% 31.0% 6.1%
7.8% 18.5% 1.6% 16.1% 0.3%
3.2% 12.0% NA+ 8.1% NA+
7-Aug 5-Aug 11-Jun 6-Aug 10-Jun
30-May 5-May 24-May 12-Jun 27-May
17-Sep 17-Oct 11-Jun 8-Oct 11-Jun
3-Jun 6-May 4-Jun 12-Jun 5-Jun
14-Sep 17-Sep 11-Jun 8-Oct 11-Jun
8-Jun 23-May 7-Jun 13-Jun 8-Jun
27-Aug 17-Sep 11-Jun 24-Sep 10-Jun
20-Jun 24-May 11-Jun 19-Jun NA+
27-Aug 10-Sep 11-Jun 23-Sep NA+
64.5 222.3 16.0 67.5 14.0
28-Aug 29-Jul 3-Jun 25-Jul 9-Jun
+ Sample period May 1 - June 12, 2008.
¶Sample period June 12 - October 31, 2008.
*NA = Not Applicable
§ Mean of all measurements for the monitoring period of May 1 to October 31, 2008.
Dissolved oxygen concentrations < 5.0 mg/L were greatest at Station BFCMIA and BFCM2A
(47.5 and 48.2% of DO concentrations, respectively) (Table 8-4). The percentage of DO
concentrations < 4.0 mg/L were greatest at Stations BFCMIA (32.1%) and BFCM2A (30.0%).
Frequency distributions indicated that Station BFCMIA had the most instantaneous DO
concentrations < 3.0 mg/L (Figures 8-7 and 8-8).
8-13
Section 8
2008 Water Quality Results
Blewett Falls Reach 2 - 2008
9
8
7
J_
of 6
5
a?
x
O 4
as
U) 3
N
0
2
1
O
05/01108 06/01/08 07101106 08/01/06 09/01/08 10(01/08 11/01/08
Date
e9a BFCM1 n BFCM1A ° BFCM2 BFCM2A T T T BFCM3
Figure 8-6 Weekly mean dissolved oxygen concentrations at continuous monitor stations
in Reach 2 of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2008.
Blewett Falls Reach 2 - 2008
30
26
20
v
a>
a
16
a>
Cr
ED 10
U-
6
O -_-
0-1
1-2 23 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13
Dissolved Oxygen (nig/L)
BFCM1 ? BFCM1A ? BFCM2 BFCM3
Figure 8-7 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, May 1 to June 11, 2008.
8-14
Section 8
2008 Water Quality Results
Blewett Falls Ruch 2 - 2008
25
20
c
as
15
a
c
as
n 10
Cr
as
L
LL
5
0
0-1 1-2 2-3 34 4-5 5-6 6-7 7-8 8-9 9-10 10-11
Dissolved Oxygen (mg/L)
BFCM1 ?BFCM1A ?BFCWA
Figure 8-8 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, June 12 to October 31, 2008.
Dissolved oxygen concentrations in Reach 2 initially declined below 5.0 mg/L on May 5 at
Station BFCMIA (Table 8-4). Dissolved oxygen concentrations < 5.0 mg/L were recorded in
until October 17 at Station BFCMIA (Table 8-4). Instantaneous DO concentrations < 5.0 mg/L
persisted into October at Stations BFCMIA and BFCM2A.
The minimum DO concentration for Reach 2 was 0.1 mg/L at Station BFCMIA (Table 8-4).
The lowest DO concentrations at all monitored stations occurred during the first week of August.
The longest duration of DO concentrations < 5.0 mg/L also occurred during this time period.
8.1.5 North Carolina Water Quality Standards for DO in Reach 2
Dissolved oxygen concentrations at Stations BFCM1, BFCMIA and BFCM2A were below one
or both water quality standards for at least 75 days from May through October, depending on the
station (Table 8-5). All monitored stations had instantaneous DO concentrations less than
4.0 mg/L and daily average DO concentrations below 5.0 mg/L during this period (Table 8-5 and
8-15
Section 8
2008 Water Quality Results
Figures 8-9). Daily average DO concentrations were below the water quality standard for some
days in Reach 2 from May 23 to September 23. Dissolved oxygen concentrations below the
instantaneous water quality standard (4.0 mg/L) were recorded on some days in Reach 2
beginning May 6 and ending October 8.
Table 8-5 Assessments of daily dissolved oxygen concentrations from May 1 to October
31, 2008 at stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant compared to the North Carolina dissolved oxygen water
quality standards.
Reach 2 stations
North Carolina Water Quality
Standard Variable BFCMI BFCMIA BFCM2+ BFCM2A¶ BFCM3+
Daily average DO (5.0 mg/L)
Number of days not meeting standard
First day standard was not met
Last day standard was not met
Instantaneous DO (4.0 mg/L)
Number of days not meeting standard
First day standard was not met
Last day standard was not met
Number of days either standard was
not met*
Number of days assesse&
+ Sample period May 1 - June 12, 2008.
¶ Sample period June 12 - October 31, 2008.
57 91 5 72 1
7-Jun 23-May 7-Jun 12-Jun 11-Jun
14-Sep 20-Sep 11-Jun 23-Sep 11-Jun
71 105 8 90 7
3-Jun 6-May 4-Jun 12-Jun 5-Jun
14-Sep 17-Sep 11-Jun 8-Oct 11-Jun
75 106 8 93 7
177 176 42 136 41
¥The total number of days that one or both of the North Carolina water quality standards for daily average
(5.0 mg/L) and instantaneous (4.0 mg/L) DO concentrations were not met.
§The number of days assessed was the total number of days from May 1 to October 31 when DO concentrations
were recorded for at least half of the day.
8-16
Section 8
Blewett Falls Reach 2, Station CM1 - 2008
15
14
13
12
11
J 10
a?
c
d
a? 8
a
X
O 7
d
6
0
N
5
4
3
2
1
O
2008 Water Quality Results
05/0'/2008 06/0'/2008 07/0'12008 08/0'/2008 09/0'/2008
Date
Blewett Falls Reach 2, Station CM1A - 2008
15
14
13
12
11
J 10
a?
E
c
d
a? 8
a
x
O 7
d
6
0
N
0 5
4
3
2
1
O
10/0'/2008 1'/0'/2008
05/0'/2008 06/0'/2008 07/0'/2008 08/0'/2008 09/0'/2008 10/0'/2008 1'/0'/2008
Date
Figure 8-9 Daily averages (black line) and ranges (vertical bars) of dissolved oxygen
concentrations at Stations BFCM1, BFCMIA, BFCM2, BFCM2A, and
BFCM3 in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, May 1 to October 31, 2008.
8-17
Section 8
Blewe# Falls Reach 2, Station CM2 - 2008
15
14
13
12
11
J 10
a?
E
9
c
d
a? 8
xx
O 7
d
6
O
N
H 5
D
4
3
2
1
O
2008 Water Quality Results
04127/2008 0&0412008 05?11/2008 051812008 05?25/2008 06/01/2008 06/08/2008 06/15?2008
Date
Blevwett Falls Reach 2, Station CM2A - 2008
15
14
13
12
11
J 10
a?
E
9
c
a?
a? 8
xx
O 7
v
a?
6
0
y
i5 5
4
3
2
1
O
06/01/2008 07/01/2008 08/01/2008 09/01/2008 10/01/2008 11/01/2008
Date
Figure 8-9 (continued).
8-18
Section 8
Blewett Falls Reach 2, Station CM3 - 2008
15
14
13
12
11
J 10
a?
9
c
a?
a? 8
a
X
O 7
v
a?
6
0
y
6 5
2008 Water Quality Results
O1
04/27/2008
05/04/2008 05/11/2008 05/18/2008 05/25/2008 06/01/2008 06/08/2008 06/15/2008
Date
Figure 8-9 (continued).
At Station BFCM1, the instantaneous DO concentration of 4.0 mg/L was not met 71 days
non-consecutive days from June 3 to September 14 (Table 8-5 and Figure 8-9). The daily
average DO concentration of 5.0 mg/L was not met on 57 days from June 7 to September 14.
Dissolved oxygen concentrations were below the water quality standards on more days at Station
BFCMIA than at Stations BFCM1 and BFCM2A. At Station BFCMIA, the DO water quality
standard of 4.0 mg/l was not met on 105 non-consecutive days starting on May 6 and ending on
September 17 (Table 8-5 and Figure 8-9). The daily average DO concentration was < 5.0 mg/L
was not met on 91 days at this station.
At Station BFCM2, instantaneous DO concentrations below 4.0 mg/L were recorded on 8 days
and daily average DO concentrations were less than 5.0 mg/L for 5 days (Table 8-5 and
Figure 8-9). Station BFCM2 was removed from the monitoring program on June 11, per
NCDWQ approval.
At Station BFCM2A, DO concentrations were below one or both North Carolina water quality
standards for 93 non-consecutive days from June 12 to October 8 (Table 8-5 and Figure 8-9).
The instantaneous water quality standard was not meet on 90 days. Daily average DO
concentrations were <5.0 mg/L occurred on 72 non-consecutive days beginning June 12 and
ending September 23. The monitoring sonde was deployed at Station BFCM2A on June 11.
8-19
Section 8 2008 Water Quality Results
At Station BFCM3, the daily average DO concentration of 5.0 mg/L was not met on 1 day while
the instantaneous DO concentration of 4.0 mg/L was not meet 7 days (Table 8-5 and Figure 8-9).
Dissolved oxygen concentrations were below both North Carolina water quality standards on
June 11. The monitoring sonde was removed from Station BFCM3 on June 11, per NCDWQ
approval.
8.1.6 Operational Effects of the Blewett Falls Hydroelectric Plant
10
8000
6000
U
4000 3
0
LL
2000
0
J
bA 8
E
c
6
O
a 4
W
J
N 2
V1
0
0
0:00 6:00 12:00 18:00 0:00 6:00 12:00 18:00 0:00 6:00 12:00 18:00
Time
BFCM1 BFCMIA BFCM2A Power Plant Flow
Figure 8-10 Dissolved oxygen concentrations at Stations BFCM1, BFCMIA, and
BFCM2A and power plant generation at the Blewett Falls Hydroelectric
Plant, July 12 to 14, 2008.
Dissolved oxygen concentrations at Stations BFCM1, BFCMIA, and BFCM2A fluctuated
throughout the monitoring period (Figures 8-6 and 8-9). Operation of the Blewett Falls Plant
affected DO concentrations in Reach 2 during the period of lake stratification (Figure 8-10). A
detailed examination of DO concentrations and power plant generated flows from July 12-14
showed a decline in DO concentrations at all stations as generation flow increased.
8.2 Water Temperature in the Pee Dee River
8.2.1 Reach 1 - Tillery Dam to Turkey Top Creek
Water temperatures ranged from 13.7 to 36.7°C in Reach 1 from May through October
(Table 8-6) at Stations TYCM1-1, TYCM1-2, TYCM1-3 and TYCM2. Mean water
temperatures ranged from 21.0°C at Station TYCM1-3 to 24.6°C at Station TYCM1-2
(Table 8-6). The Reach 1 maximum instantaneous temperature of 36.7°C occurred at Station
TYCM1-3. Weekly mean temperatures were generally lower at Station TYCM1-1 than the other
stations from May through August (Figure 8-11). Weekly mean temperatures at all stations
followed the same temporal pattern with peak summer values (Figure 8-11).
8-20
Section 8 2008 Water Quality Results
Table 8-6 Summary statistics of water quality variables from stations in Reach 1 of the
Pee Dee River below the Tillery Hydroelectric Plant, May 1 to October 31,
2008.
Reach 1 Stations
Water Quality
Variable TYCMl-1 TYCM1-2+ TYCM1-3+ TYCM2 TYCM3¶ TYCM4¶
Mean temperature 22
7
(°C) .
Temperature range 15
8-28
9
(°C) .
.
Median pH 6.9
pH range 6.1-8.9
Mean specific 101
conductance (,uS/cm)
Specific conductance 37-133
range (pS/cm)
24.6 23.8 23.3 21.0 23.2
19.0-32.2 11.4-36.7 13.7-34.8 16.1-31.3 19.2-31.6
6.9 6.9 7.1 7.0 7.1
6.3-8.9 6.3-9.1 6.4-10.2 6.7-8.8 6.7-8.5
102 102 102 110 112
56-149 77-122 84-125 94-239 94-213
+ Sample period June 12 - October 31, 2008.
¶ Sample period May 1 - June 12, 2008.
8-21
Section 8
Tillery Reach 1 - 2008
30
a?
L
20
U
N
a?
L
L
10
L
Q
E
2008 Water Quality Results
0+----
05/01/08
06/01/08 07/01/08 08/01/08 09/01/08 10/01/08 11/01/08
Date
e Ce TYC M1-1 E E Q TYC M1-2 ?? TYC M1-3 TYC M2 T T T TYC M3 TYC M4
Figure 8-11 Weekly mean temperatures (°C) at continuous monitor stations in Reach 1 of
the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to October
31, 2008.
Temperature values greater than the North Carolina water quality standard of 32°C were most
often observed at Station TYCM1-3 from June to August. Infrequent excursions above 32°C
were noted at Stations TYCM1-2 and TYCM2. Temperature measurements > 32°C at Station
TYCM1-3 accounted for 3% (n = 381) of the total number of measurements (n = 12,656). There
were 152 measurements that were > 32°C at Station TYCM2 (n = 16,017) and 2 measurements
at Station TYCM1-2 (n = 10,170).
8.2.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek
Water temperatures ranged from 13.0 to 33.4°C at Stations BFCM1, BFCMIA, and 13FCM2A
from the May through October monitoring period (Table 8-7). Mean water temperatures in
Reach 2 ranged from 22.4°C at BFCM2 to 25.2°C at BFCMIA (Table 8-7). The Reach 2
maximum instantaneous temperature of 33.4°C occurred at Station BFCMIA on August 8.
Weekly average water temperatures were similar throughout the monitoring period
(Figure 8-12).
8-22
Section 8 2008 Water Quality Results
Table 8-7 Summary statistics of water quality variables from stations in Reach 2 of the
Pee Dee River below the Blewett Falls Hydroelectric Plant, May 1 to October
31, 2008.
Reach 2 Stations
Water Quality
Variable BFCM1 BFCMIA BFCM2+ BFCM2V BFCM3+
Mean temperature (°C) 24.4 24.5 22.4 25.2 23.0
Temperature range (°C) 15.1-31.3 13.0-33.4 17.3 -30.2 13.8-32.8 18.0-33.3
Median pH 7.2 7.0 7.0 6.9 7.0
pH range 6.3-9.2 5.9-9.2 6.7-7.8 6.2-8.8 6.7-9.4
Mean specific conductance 111 115 106 120 109
(PS/CM)
Specific conductance range 64-142 38-170 90-119 39-164 100-121
(PS/CM)
+ Sample period May 1 - June 12, 2008.
¶ Sample period June 12 - October 31, 2008
8-23
Section 8
Blewett Falls Reach 2 - 2008
4C
a?
30
LM
a?
U
N
d
d
L 20
d
d
L
L
d
E 10
2008 Water Quality Results
d
H
0+-
05/01/08
06/01/08 07/01/08 08!01/08 09/01/08 10/01/08 11/01/08
Data
b e e BFCM1 - BFCM1A ° BFCM2 BFCM2A II I BFCM3
Figure 8-12 Weekly mean temperatures at continuous monitor stations in Reach 2 of the
Pee Dee River below the Blewett Falls Hydroelectric Plant, May 1 to October
31, 2008.
Temperature values greater than the North Carolina water quality standard of 32°C were most
often observed at Station BFCM3 in June. The monitoring sonde at Station BFCM3 was
removed on June 11, per NCDWQ approval. Temperature measurements were > 32°C less than
2% (n = 65) of the total number of measurements (n = 3,819) occured at Station BFCM3.
Infrequent excursions (< 1%) above 32°C occurred at Stations BFCMIA and BFCM2A.
8.3 pH in the Pee Dee River
8.3.1 Reach 1 - Tillery Dam to Turkey Top Creek
Median pH values at stations in Reach 1 were slightly acidic to nearly neutral (6.9 - 7.1) for the
monitoring period (Table 8-7). Instantaneous pH values in Reach 1 ranged from 6.1 at Station
TYCM1-1 to 10.2 at Station TYCM2. Weekly mean pH values ranged from 6.4 to 8.6
(Figure 8-13). Weekly mean pH mean values were less than 8.0 except at Station TYCM2
during early May. Station TYCM1-1 typically had the lowest weekly mean pH values while
Station TYCM2 usually had the highest weekly mean pH values.
8-24
Section 8
2008 Water Quality Results
Tillery Reach 1 - 2008
9
2
Q
4
0?
05/01/08
06/01/08 07/01/08 08/01108 09/01/08 10/01/08 11/01/06
Date
-0a TYC M1-1 ?e TYC M1-2 TYC M1-3 TYC M2 ! ! + TYC M3 TYC M4
Figure 8-13 Weekly mean pH values at continuous monitor stations in Reach 1 of the Pee
Dee River below the Tillery Hydroelectric Plant, May 1 to October 31, 2008.
The daily pH values fluctuated widely at Station TYCM2 and instantaneous values often
exceeded 9.0, particularly during May. These instantaneous pH values exceeded the upper limit
(9.0) of the North Carolina water quality standard for pH (NCDWQ 2007). Approximately 11.0
percent of the total number of measurements (n = 16,017 measurements) at Station TYCM2
exceeded 9.0. Infrequent excursions (<1.0% of total measurements) above 9.0 were also noted at
Station TYCM1-3. The pH fluctuations at Station TYCM2 followed DO trends, and likely
reflect algal photosynthesis and respiration (Figure 8-14).
8-25
Section 8
18
16
14
2008 Water Quality Results

bbb
12
c

a 10

O
8

w

0
6

D A
12
10
8
6 a
4
2
2

0 0
0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00
Time
Dissolved Oxygen (mg/1) pH
Figure 8-14 Dissolved oxygen concentrations and pH values at Station TYCM2 in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 4 to
11, 2008.
8.3.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek
All Reach 2 stations had median pH values near neutral (6.9 to 7.0) (Table 8-7). Instantaneous
pH values in Reach 2 ranged from 5.9 to 9.4. Weekly mean pH values ranged from 6.5 to 8.0
(Figure 8-15). There was no consistent spatial trend in pH among monitored stations
(Figure 8-15).
8-26
Section 8
Blewefx Falls Reach 2 - 2008
= 4
Q
2008 Water Quality Results
01---
05/01/00
06/01/08 07101108 08/01/08 09/01/00 10/01/08 11/01/08
Date
- BFCM1 - BFCM1A ° BFC1W BFCrVM I I I BFCM3
Figure 8-15 Weekly mean pH values at continuous monitor stations in Reach 2 of the Pee
Dee River below the Blewett Falls Hydroelectric Plant, May 1 to October 31,
2008.
8.4 Specific Conductance in the Pee Dee River
8.4.1 Reach 1 - Tillery Dam to Turkey Top Creek
Mean specific conductance values for Reach 1 stations from May through October ranged from
101 to 102 µS/cm at Stations TYCM1-1, TYCM1-2, TYCM1-3 and TYCM2 (Table 8-6).
Instantaneous specific conductance values within Reach 1 ranged from 37 to 149 ,uS/cm. For the
limited data sets weekly mean specific conductance values were always greater at Stations
TYCM3 and TYCM4 than at other monitored stations. Weekly mean specific conductance
values at Stations TYCM1-1, TYCM1-2, TYCM1-3 and TYCM2 ranged from 101 to 102 µS/cm
while values at Stations TYCM3 and TYCM4 were 110 and 112 µS/cm respectively.
The Rocky River and Brown Creek enter the Pee Dee River between Stations TYCM2 and
TYCM3, and high specific conductance in the Rocky River has been documented by the
NCDWQ (2010) and Progress Energy (2003, 2006a).
8-27
Section 8
Tillery Reach 1 - 2008
120
110
100
2008 Water Quality Results
E 90
Cn
80
d
70
60
o 50
U
w 40
C 30
Cn
20
10
0'
0501/08 06/01/08 07/01/08 08/01/08 09f01/08 1001/08 11/01/08
Date
e ?e TYC M1-1 ?Q TYC M1-2 TYC M1-3 TYC M2 TYC M3 TYC M4
Figure 8-16 Weekly mean specific conductance values at continuous monitor stations in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
October 31, 2008.
8.4.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek
Mean specific conductance values at stations in Reach 2 ranged from 111 to 120 US/cm for
Stations BFCM1, BFCMIA, and BFCM2A from the May through October monitoring period
(Table 8-7). Instantaneous specific conductance values ranged from 38 to 170 ,uS/cm. Weekly
mean specific conductance values at each station showed similar temporal trends during the
monitoring period (Figure 8-17).
8-28
Section 8
150
140
130
- 120
E
110
N
100
d
90
C9 80
3
70
U O 60
50
40
Q
N 30
20
10
0'
05/01/08 06(01/08 07101108 09101/08 09/01/08 10/01/08
Date
e g BFCM1 BFCM1A ° BFCM2 BFCWA +-+-+ BFCW
11/01/08
Figure 8-17 Weekly mean specific conductance values at continuous monitor stations in
Reach 2 of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2008.
Blewett Falls Reach 2 - 2008
2008 Water Quality Results
8-29
Section 9 - 2009 Water Quality Results
9.1 Water Quality in the Pee Dee River, 2009
9. 1.1 Dissolved Oxygen - Tillery Dam to Rocky River Confluence (Reach 1)
During the May through October study period, instantaneous DO concentrations in Reach 1
ranged from 0.1 to 18.7 mg/L (Table 9-1). Mean DO concentrations ranged from 5.2 to 6.2
mg/L (Table 9-1). Throughout Reach 1, DO concentrations exhibited a seasonal trend with
lowest values occurring during the summer months of July through August (Figure 9-1).
Table 9-1 Dissolved oxygen concentration summary for Reach 1 of the Pee Dee River
below the Tillery Hydroelectric Plant, May 1 to October 31, 2009.

Dissolved Oxygen (DO) Variable
TYCMl-1 Reach 1 Stations
TZCMl-2 TYCMl-3
TYCM2
Mean DO (mg/L) + 5.2 5.6 5.9 6.2
Range of DO (mg/L) 0.1-12.3 1.4-13.8 0.9-15.8 0.5-18.7
Percent of DO concentrations < 5.0 mg/L 43.7% 41.7% 39.5% 36.1%
Percent of DO concentrations < 4.0 mg/L 30.8% 27.5% 28.1% 22.4%
Percent of DO concentrations < 3.0 mg/L 21.4% 16.8% 15.8% 7.0%
Percent of DO concentrations < 2.0 mg/L 13.4% 6.3% 3.3% 0.4%
Date of lowest DO concentration 23-Aug 20-Aug 23-Aug 13-Jul
First DO concentration < 5.0 mg/L 10-May 4-May 4-May 2-May
Last DO concentration < 5.0 mg/L 7-Oct 10-Oct 10-Oct 10-Oct
First DO concentration < 4.0 mg/L 27-Jun 5-May 5-May 21-Jun
Last DO concentration < 4.0 mg/L 27-Sep 28-Sep 25-Sep 21-Sep
First DO concentration < 3.0 mg/L 5-Jul 30-Jun 10-May 30-Jun
Last DO concentration < 3.0 mg/L 21-Sep 3-Sep 20-Sep 28-Aug
First DO concentration < 2.0 mg/L 12-Jul 16-Jul 16-Jul 11-Jul
Last DO concentration < 2.0 mg/L 3-Sep 31-Aug 3-Sep 20-Aug
Longest duration of DO < 5.0 mg/L (hours) 48.25 39.25 20.75 21.75
Start of longest duration of DO < 5.0 mg/L 27-Aug 12-Jul 26-Aug 27-Jul
+Mean of all measurements for the monitoring period of May 1 to October 31, 2009 .
9-1
Section 9
2009 Water Quality Results
Weekly mean DO concentrations varied throughout Reach 1 (Figure 9-1). However, weekly
mean DO concentrations for Station TYCM1-1, TYCM1-2, and TYCM1-3 were typically lower
than Station TYCM2.
Station TYCM1-1 had more instantaneous DO concentrations below 4.0 mg/L (30.8%) than
other stations in Reach 1 (22.4 to 28.1%) (Table 9-1 and Figure 9.2). Frequency distributions of
DO concentrations for Stations TYCM1-1, TYCM1-2, and TYCM1-3 were similar (Figure 9-2).
Station TYCM2 differed from other stations with a wider distribution of DO concentrations,
including a higher frequency of DO concentrations > 10.0 mg/L.
Tillery Reach 1 - 2009
10
9
8
J 7
E
r 6
d
X 5
O
4
O
N
N 3
0
2
1
0
05/01/09
06/01/09 07101109 08/01/09 09/01/09 10/01/09
Date
eeg TYCM1-1 - TYCM1-2 - TYCM1-3 TYCM2
11/01/09
Figure 9-1 Weekly mean dissolved oxygen concentrations at continuous monitor stations
in Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 1
to October 31, 2009.
9-2
Section 9
2009 Water Quality Results
TilleryReaeh 1 - 2009
20
15
a
as
v
as
a
10
as
Cr
as
LL
rz+
0
TYCM1-1 ? TYCM1 2 ? TYCM1-3 TYCM2
Figure 9-2 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant, May 1 to October 31, 2009.
The percentage of instantaneous DO concentrations below 5.0 mg/L in Reach 1 generally
decreased with increased distance from the Tillery Hydroelectric Plant. Approximately 40-44%
percent of the DO concentrations recorded at Stations TYCM1-1, TYCM1-2 and TYCM1-3
were <5.0 mg/L (Table 9-1). The percent of DO concentrations below 5.0 mg/L was 36.1% at
the downstream Station TYCM2.
There was a spatial difference in DO concentrations at the Stations TYCM1-1, TYCM1-2, and
TYCM1-3. Generally DO concentrations would increase from the east side of the channel
(Station TYCM1-1) to the west side of the channel (Station TYCM1-3) (Table 9-1).
Dissolved oxygen concentrations decreased below 5.0 mg/L at all stations by early May
(Table 9-1). Dissolved oxygen concentrations below 5.0 mg/L were recorded on many days at
stations in Reach 1 through October. The last DO concentration below 5.0 mg/L in Reach 1
occurred on October 10.
0-1 1-2 2-3 3-4 4-6 6-6 6-7 7-8 8-9 9-1010-1111-1212-1313-1414-1816-1616-1717-18 8-19
Dissolved Oxygen (mg/L)
9-3
Section 9
2009 Water Quality Results
9.1.2 North Carolina Water Quality Standards for DO in Reach 1
The North Carolina water quality standards for DO require a daily average DO concentration of
at least 5.0 mg/L and all instantaneous DO concentrations must be at least 4.0 mg/L
(NCDWQ 2007). Dissolved oxygen concentrations were below one or both water quality
standards at all four stations in Reach 1 for varying periods of time during 2009. The water
quality standards were not met for 59 to 94 non-consecutive days depending upon the station
(Table 9-2 and Figure 9-3). The period during which the water quality standard for daily average
DO (5.0 mg/L) were not meet began in late June-early July and ended in late September.
Instantaneous dissolved oxygen concentrations in Reach 1 initially decreased below 4.0 mg/L on
May 5 and concentrations < 4.0 mg/L were recorded on some days until September 28
(Table 9-2).
Table 9-2 Assessments of daily dissolved oxygen concentrations from May 1 to October
31, 2009 at Stations in Reach 1 of the Pee Dee River below the Tillery
Hydroelectric Plant compared to the North Carolina dissolved oxygen water
quality standards.
North Carolina Water Quality Standard
Daily average DO (5.0 mg/L)
Number of days not meeting standard
First day standard was not met
Last day standard was not met
Reach 1 Stations
TYCM1-1 TYCM1-2 TYCM1-3 TYCM2
70 45 38 27
25-Jun 30-Jun 2-Jul 1-Jul
27-Sep 28-Sep 21-Sep 31-Aug
Instantaneous DO (4.0 mg/L)
Number of days not meeting standard
First day standard was not met
Last day standard was not met
Number of days either standard was not met+
Number of days assessed¶
68 70 94 59
27-Jun 5-May 5-May 21-Jun
27-Sep 28-Sep 25-Sep 21-Sep
74 70 94 59
168 143 165 169
+The total number of days that one or both of the North Carolina water quality standards for daily average
(5.0 mg/L) and instantaneous (4.0 mg/L) DO concentrations were not met.
¶The number of days assessed was the total number of days from May 1 to October 31 when DO concentrations
were recorded for at least half of the day.
9-4
Section 9
Tillery Reach 1, Station CM1-1 - 2009
19
18
17
16
15
14
J 13
E 12
? 11
>' 10
X
O 9
v
> 8
to 7
6
5
4
3
2
1
0
2009 Water Quality Results
05/01/2009 06/01/2009 C710112009 08/01/2009 09/01/2009 10/01/2009
Date
Tillery Reach 1, Station CM1-2 - 2009
19
18
17
16
15
14
J 13
E 12
? 11
a?
>' 10
X
O 9
v
> 8
U) 7
U)
6
5
4
3
2
1
0
11/01/2009
05/01/2009 06/01/2009 07/01/2009 08/01/2009 09/01/2009 10/01/2009 11/01/2009
Date
Figure 9-3 Daily averages (black line) and ranges (vertical bars) of dissolved oxygen
concentrations at Stations TYCM1-1, TYCM1-2, TYCM1-3, and TYCM2 in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
October 31, 2009.
9-5
Section 9
19-
18-
17-
16-
15-
14-
13-
E 12
? 11
a?
>, lo-
x
O g
v
> 8
U) 7-
U) MI/
0 6
5
4
3
2
1
0
05/01/2009
19
18
17
16
15
14
J 13
E 12
C 11
a 10
x
O g
> 8
N 7
N_
0 6
5
4
3
2
1
0
vwv?icvva viiv ?i cvva voiv ?icwa vaiv ?icvva
Date
Tillery Reach 1, Station CM2 - 2009
2009 Water Quality Results
10/01/2009 11/01/2009
05?01/2009 06/01/2009 07/01/2009 08/01/2009 09/01/2009 10101/2009 11/01/2009
Date
Figure 9-3 (continued).
9-6
Tillery Reach 1, Station CM1-3 - 2009
Section 9 2009 Water Quality Results
At Station TYCM1-1, DO concentrations were below one or both North Carolina water quality
standards for 74 non-consecutive days from late June to late September (Table 9-2 and
Figure 9-3). Instantaneous DO concentrations below 4.0 mg/L and daily average concentrations
less than 5.0 mg/L usually occurred on the same days.
At Station TYCM1-2, DO concentrations were below one or both North Carolina water quality
standards for 70 non-consecutive days from May 5 to September 28 (Table 9-2 and Figure 9-3).
Instantaneous DO concentrations below 4.0 mg/L and daily average concentrations less than
5.0 mg/L typically did not occurred on the same days. Of the 70 days that either water quality
standard was not met, daily average DO (5.0 mg/L) accounted for 45 days (Table 9-2).
Dissolved oxygen concentrations were below the water quality standards more frequently at
Station TYCM1-3 than at other Reach 1 stations. At Station TYCM1-3, DO concentrations were
below one or both water quality standards on 94 non-consecutive days from May 5 to
September 25 (Table 9-2 and Figure 9-3). DO concentrations below 4.0 mg/L and daily average
concentrations less than 5.0 mg/L typically did not occurred on the same days. Of the 94 days
either standard was not met, daily average DO (5.0 mg/L) accounted for 38 days (Table 9-2).
At Station TYCM2, DO concentrations were below one or both North Carolina water quality
standards for 59 non-consecutive days from June 21 to September 21 (Table 9-2 and Figure 9-3).
Dissolved oxygen concentrations below 4.0 mg/L and daily average concentrations less than
5.0 mg/L typically did not occurred on the same days. Of the 59 days that either water quality
standard was not met, daily average DO (5.0 mg/L) accounted for 27 days (Table 9-2).
9.1.3 Operational Effects of the Tillery Hydroelectric Plant
Dissolved oxygen concentrations in Reach 1 were affected by algal respiration/photosynthesis,
diel cycles, tributary inflow, and power plant operations. Similar to observations in previous
years (Progress Energy 2005b,2006d, and this report), there were pronounced diel cycles in DO
concentrations at all monitored stations. This DO fluctuation likely reflected the influence of
algal photosynthesis and respiration. This diel cycle was apparent on days of no power plant
generation (Figure 9-4). Dissolved oxygen concentrations typically changed by 3 to 6 mg/L
during a 24-hour period at all monitored stations. On days without power generation, the DO
concentrations would begin to rise around dawn, peak during early afternoon, decrease through
the early evening, and then remain low until the next day (Figure 9-4). When flows increased
with power generation, the DO concentrations correspondingly decreased. This effect was
particularly evident when generation began several hours after DO concentrations began to rise
in the morning hours. Dissolved oxygen concentrations would then decline to levels just above
the pre-dawn concentrations (Progress Energy 2005b, 2006d). The diel response of DO also
showed seasonal shifts with greater peaks in DO concentrations during the days of longer
daylight length and warmer water temperatures in the warmer months (May-September) when
there was greater photosynthetic activity as opposed to the days of shorter daylight length and
lower water temperatures in the cooler periods (early May and October) (Progress Energy 2005b,
2006c).
9-7
Section 9
12.0
10.0
o?io
8.0
c
w
ao
0 6.0
w
O 4.0
N
2.0
0.0
2009 Water Quality Results
Time
I TYCM1-1 TYCM1-2 - TYCM1-3 TYCM2
Figure 9-4 Dissolved oxygen concentrations (mg/L) on select days (October 10-13 2009)
with no generation at Stations TYCM1-1, TYCM1-2, TYCM1-3 and
TYCM2.
Even on days when no power generation occurred, the DO concentrations were not always high
enough to meet both North Carolina water quality standards at Stations TYCM1-1, TYCM1-3,
and TYCM2 (Table 9-3). From May 1 to October 31, the number of days without any power
generation during a 24-hour period at the Tillery Hydroelectric Plant totaled 7 days. Of these 7
days, daily mean DO concentrations were less than 5.0 mg/L on 1 day at Station TYCM1-1 and
2 days at Stations TYCM2 and TYCM1-3, and instantaneous DO concentrations below 4.0 mg/L
occurred on 1 day at Station TYCM2 and 2 days at Station TYCM1-3 (Table 9-3). These results
indicated that algal respiration, tributary inflow, retainer gate leakage and/or wicket gate leakage
from the power plant influenced DO dynamics during non-generation periods at all stations.
9-8
0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00
Section 9
2009 Water Quality Results
Table 9-3 Days that no power was generated at the Tillery Hydroelectric Plant and
assessments of dissolved oxygen concentrations at stations in Reach 1 to
determine if they met the North Carolina water quality standards for daily
average and instantaneous dissolved oxygen concentrations during 2009.+
Reach 1 Stations
TYCM1-1 TYCM1-2 TYCM1-3 TYCM2
< 5.0 < 4.0 < 5.0 < 4.0 < 5.0 < 4.0 < 5.0 < 4.0
Date mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L
July 11 x x x x
August 1
September 18 x x x x
October 10
October 11
October 12
October 13
Total 1 0 0 0 2 2 2 1
'Days when the daily average DO was < 5.0 mg/L and days when an instantaneous DO concentration was
< 4.0 mg/L are denoted with an "x". Days that the water quality standards were met are not marked.
9.1.4 Dissolved Oxygen - Blewett Falls Dam to Below Hitchcock Creek
(Reach 2)
For the May through October monitoring period, DO concentrations ranged from 0.1 to
11.6 mg/L at the stations in Reach 2 (Table 9-4). Mean DO concentrations ranged from 5.5 to
6.4 mg/L for (Table 9-4). Generally, DO concentrations cycled seasonally, with lower values
during the summer (Figures 9-5 and 9-7).
Weekly average DO concentrations were usually lower at Stations BFCMIA and BFCM2A
compared to Station BFCM1. Generally, the weekly average DO concentrations at the three
stations differed by < 3.0 mg/L. Weekly average DO concentrations for all three stations
followed a similar seasonal trend (Figure 9-5).
Instantaneous dissolved oxygen concentrations recorded from May through October in Reach 2
were lowest at Station BFCM2A where 34.5% of the DO measurements were below 5.0 mg/L,
(Table 9-4 and Figure 9-6). Dissolved oxygen concentrations less than 5.0 mg/L represented less
than 27% of the measurements at Stations BFCM1 and BFCMIA. The percentage of DO
concentrations < 4.0 mg/L was highest at Stations BFCMIA (12.9%) and BFCM2A (22.4 %).
9-9
Section 9 2009 Water Quality Results
Table 9-4 Dissolved oxygen concentration summary for Reach 2 of the Pee Dee River
below the Blewett Falls Hydroelectric Plant, May 1 to October 31, 2009.

Dissolved Oxygen (DO) Variable
BFCMl Reach 2 Stations
BFCMIA BFCM2A
Mean DO (mg/L) + 6.4 5.9 5.5
Range of DO (mg/L) 1.0-11.6 0.7-11.1 0.1-10.3
Percent of DO concentrations < 5.0 mg/L 18.4% 26.9% 34.5%
Percent of DO concentrations < 4.0 mg/L 6.3% 12.9% 22.4%
Percent of DO concentrations < 3.0 mg/L 1.3% 4.3% 14.4%
Percent of DO concentrations < 2.0 mg/L 0.1% 0.8% 8.1%
Date of lowest DO concentration 3-Aug 2-Aug 15-Jul
First DO concentration < 5.0 mg/L 16-Jun 16-May 16-May
Last DO concentration < 5.0 mg/L 28-Sep 17-Oct 7-Oct
First DO concentration < 4.0 mg/L 16-Jun 26-Jun 26-Jun
Last DO concentration < 4.0 mg/L 24-Sep 24-Sep 27-Sep
First DO concentration < 3.0 mg/L 29-Jun 26-Jun 28-Jun
Last DO concentration < 3.0 mg/L 31-Aug 31-Aug 21-Sep
First DO concentration < 2.0 mg/L 2-Aug 29-Jun 5-Jul
Last DO concentration < 2.0 mg/L 30-Aug 23-Aug 21-Sep
Longest duration of DO < 5.0 mg/L (hours) 45.75 59.25 122.5
Start of longest duration of DO < 5.0 mg/L 31-Jul 26-Jul 24-Jul
+Mean of all measurements for the monitoring period of May 1 to October 31, 2009.
9-10
Section 9
2009 Water Quality Results
Blewett Fal Is Reach 2 - 2009
9
8
7
J_
CD 6
E
C
4)6
a
x
4
0 3
U)
0
2
0+----
05J01/09
Figure 9-5
06/01/09 07/01/09 08/01/09 091101/09 10101/09 11/01/09
Date
e? BFCM1 E BFCM1A BFCM2A
Weekly mean dissolved oxygen concentrations at continuous monitor stations
in Reach 2 of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2009.
9-11
Section 9
BleMt Falls Ruch 2 - 2009
35
2009 Water Quality Results
30
25
C
a?
L
d 20
L
C 15
3
Cr
d
L
LL 10
5
0
0-1 1-2 2-3 34 4-5 5-6 6-7 7-8 8-9 9-10 1041 1142
Dissolved Oxygen (mg/L)
BFCM1 ?BFCM1A ?BFCWA
Figure 9-6 Frequency distributions of dissolved oxygen concentrations at continuous
monitor stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant, May 1 to October 31, 2009.
Dissolved oxygen concentrations in Reach 2 initially declined below 5.0 mg/L on May 16 at
Stations BFCMIA and BFCM2A (Table 9-4). Dissolved oxygen concentrations below 5.0 mg/L
persisted into October at Stations BFCMIA, and BFCM2A.
The minimum DO concentration for Reach 2 was 0.1 mg/L at Station BFCM2A (Table 9-4). All
measured lowest DO concentrations at Stations BFCM1, BFCMIA, and BFCM2A occurred
during the middle of July and the first week of August. The longest duration of DO
concentrations below 5.0 mg/L also occurred during this time period (Table 9-4).
9-12
Section 9
2009 Water Quality Results
9.1.5 North Carolina Water Quality Standards for DO in Reach 2
Dissolved oxygen concentrations at stations in Reach 2 were below one or both water quality
standards from 39 to 67 non-consecutive days from May through October, depending upon the
station (Table 9-5). All three stations had instantaneous DO concentrations < 4.0 mg/L and daily
average DO concentrations < 5.0 mg/L during this period (Table 9-5 and Figure 9-7). Dissolved
oxygen concentrations were below the daily average water quality standard (5.0 mg/L) from late
June to late September. Instantaneous DO concentrations were below the water quality standard
(4.0 mg/L) from mid June to late September. Dissolved oxygen concentrations were below one
or both North Carolina water quality standards at Station BFCMI on 39 non-consecutive days,
the fewest days of any stations monitored in Reach 2.
Table 9-5 Assessments of daily dissolved oxygen concentrations from May 1 to October
31, 2009 at stations in Reach 2 of the Pee Dee River below the Blewett Falls
Hydroelectric Plant compared to the North Carolina dissolved oxygen water
quality standards.
Reach 2 Stations
North Carolina Water Oualitv Standard
Daily average DO (5.0 mg/L)
Number of days not meeting standard
First day standard was not met
Last day standard was not met
Instantaneous DO (4.0 mg/L)
Number of days not meeting standard
First day standard was not met
Last day standard was not met
Number of days either standard was not met+
Number of days assessed¶
BFCMI BFCMIA BFCM2A
26 45 51
5-Jul 26-Jun 29-Jun
24-Sep 24-Sep 27-Sep
36 61 66
16-Jun 26-Jun 26-Jun
24-Sep 24-Sep 27-Sep
39 63 67
163 176 152
+The total number of days that one or both of the North Carolina water quality standards for daily average
(5.0 mg/L) and instantaneous (4.0 mg/L) DO concentrations were not met.
¶The number of days assessed was the total number of days from May 1 to October 31 when DO concentrations
were recorded for at least half of the day.
9-13
Section 9
Blewett Falls Reach 2, Station CM1 - 2009
15
14
13
12
11
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a? 8
a
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v
a?
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2009 Water Quality Results
05/01/2009 06/01/2009 07/01/2009 08/01/2009 09/01/2009
Date
Blewett Falls Reach 2, Station CM1A - 2009
15
14
13
12
11
J 10
a?
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9
c
d
a? 8
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v
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2
1
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10/01/2009 11/01/2009
05/01/2009 06/01/2009 C710112009 08/01/2009 09/01/2009 10/01/2009 11/01/2009
Date
Figure 9-7 Daily averages (black line) and ranges (vertical bars) of dissolved oxygen
concentrations at Stations BFCM1, BFCMIA and BFCM2A in Reach 2 of
the Pee Dee River below the Blewett Falls Hydroelectric Plant, May 1 to
October 31, 2009.
9-14
Section 9
Blewett Falls Reach 2, Station CM2A - 2009
15
14
13
12
11
J 10
2009 Water Quality Results
a?
9
c
a?
a? 8
a
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v
a?
6
0
y
6 5
0
05/01/2009 06/01/2009 07/01/2009 08/01/2009 09/01/2009 10/01/2009 11/01/2009
Date
Figure 9-7 (continued).
Dissolved oxygen concentrations below one or both the water quality standards occurred during
39 non-consecutive days from mid June through late September at Station BFCM1 (Table 9-5
and Figure 9-7). The daily average DO concentration was < 5.0 mg/L on 26 non-consecutive
days from early July through late September. The daily minimum DO concentration was
< 4.0 mg/L on 36 non-consecutive days from mid June through late September.
At Station BFCMIA, DO concentrations were below one or both North Carolina water quality
standards for 63 non-consecutive days from late June through late September (Table 9-5 and
Figure 9-7). The daily average DO concentration was < 5.0 mg/L on 45 non-consecutive days
during the study period. The daily minimum DO concentration was < 4.0 mg/L on 61
non-consecutive days from late June through late September.
Dissolved oxygen concentrations were below one or both North Carolina water quality standards
for a total of 67 non-consecutive days from late June through late September (Table 9-5 and
Figure 9-7). For 66 of the 67 days, the North Carolina water quality standard was not met for
instantaneous DO concentrations <4.0 mg/L. Daily average DO concentrations were < 5.0 mg/L
for 51 non-consecutive days from late June through late September.
9-15
Section 9
2009 Water Quality Results
9.1.6 Operational Effects of the Blewett Falls Hydroelectric Plant
Dissolved oxygen concentrations at Stations BFCM1, BFCMIA, and BFCM2A fluctuated
throughout the study period (Figures 9-7 and 9-8). The operation of Blewett Falls Plant
influenced DO concentrations in Reach 2 during periods of lake stratification (Figure 9-8). An
examination of DO concentrations and generation flows from July 7-12 showed a distinct DO
cycle at all stations with power plant generation. Blewett Falls Plant operations have an effect on
DO levels in Reach 2, but the effect is dependent upon the degree of lake stratification and the
amount of water released from the plant.
ao
E
c
w
T
O
w
0
0
10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00
Time
BFCM1 BFCMIA BFCMIA Generation
8000
7000
6000
5000 v
w
4000 Lo
M
t
3000
0
2000
1000
0
Figure 9-8 Dissolved oxygen concentrations at Stations BFCM1, BFCMIA, and
BFCM2A, and power plant generation at the Blewett Falls Hydroelectric
Plant, July 7 to 12, 2009.
9.1.7 Comparison of DO Temporal Trends, 2004 - 2009
A comparison was made between temporal and spatial trends observed in DO concentrations in
each power plant tailwaters between the 2004 and 2005-2009 monitoring programs. Although
the monitoring period duration and station locations differed between years (i.e., May-November
in 2004 and May-October in 2005-2009), some general trends can be described relative to DO
concentrations in power plant tailwaters.
9-16
Section 9 2009 Water Quality Results
Generally, the means and ranges of DO concentrations were similar between 2004 and
2005-2009 although there some differences in the lower end of measured DO concentrations
depending upon station location (Table 9-6). The period that DO concentrations did not meet the
water quality standards occurred later in the year during 2007 from two to four weeks (i.e., mid
May to early October) compared to the period documented in other years (i.e., late May through
early September). This temporal difference was attributable to climatological differences,
reservoir stratification patterns, and subsequent power plant generation. The year 2007 was
marked by a dry, warm spring and hot summer. There were also a greater percentage of DO
values that were in the 2-5 mg/L range in 2007 compared to other years at most continuous
monitoring stations in both river reaches.
Generally, spatial trends in both river reaches were consistent between monitoring years. The
stations closest to the power plants have the greatest occurrence of DO values below the DO
water quality standards with the frequency of occurrence of low DO values decreasing with
increasing distance downstream of each power plant.
Table 9-6 Comparison of DO summary statistics between the 2004-2009 continuous
monitoring programs for the Tillery and the Blewett Falls Hydroelectric
Plants.
Tillerv Hvdroelectric Plant
Reach 1 Station
TYCMI-I
Dissolved Oxygen (DO) Variable 2004 2005 2006 2007 2008 2009
Mean DO (mg/L) 5.3 5.4 5.4 5.2 5.1 5.2
Range of DO (mg/L) 1.2-11.1 0.4-13.1 0.9-13.8 0.2-14.0 0.6-12.6 0.1-12.3
Percent of DO concentrations < 5.0 mg/L 42.5% 45.7% 46.8% 50.8% 47.1% 43.7%
Percent of DO concentrations < 4.0 mg/L 28.8% 31.3% 34.6% 37.9% 37.7% 30.8%
Percent of DO concentrations < 3.0 mg/L 8.7% 14.4% 21.9% 27.6% 24.6% 21.4%
Percent of DO concentrations < 2.0 mg/L 0.5% 1.3% 6.3% 10.3% 3.3% 13.4%
Daily average DO (5.0 mg/L)
Number of days not meeting standard 83 76 81 91 79 70
First day standard was not met June 3 June 30 10-Jun 29-May 12-Jun 25-Jun
Last day standard was not met Sep 7 Oct 7 14-Sep 22-Oct 8-Oct 27-Sep
Instantaneous DO (4.0 mg/L)
Number of days not meeting standard 91 87 97 115 94 68
First day standard was not met June 1 June 10 25-May 26-May 30-May 27-Jun
Last day standard was not met Sep 8 Oct 7 14-Sep 19-Oct 11-Sep 27-Sep
Number of days either standard was not
me 94 88 98 117 95 74
Number of days assessed 140 169 195 214 161 168
9-17
Section 9
Table 9-6 (continued).
2009 Water Quality Results
Reach 1 Stations
TYC M1-2 TYCM1-3
Dissolved Oxygen (DO) Variable 2008 2009 2008 2009
Mean DO (mg/L) 4.7 5.6 5.8 5.9
Range of DO (mg/L) 1.2-11.6 1.4-13.8 1.1-14.4 0.9-15.8
Percent of DO concentrations < 5.0 mg/L 62.5% 41.7% 47.0% 39.5%
Percent of DO concentrations < 4.0 mg/L 50.8% 27.5% 37.4% 28.1%
Percent of DO concentrations < 3.0 mg/L 31.3% 16.8% 18.2% 15.8%
Percent of DO concentrations < 2.0 mg/L 5.5% 6.3% 2.6% 3.3%
Daily average DO (5.0 mg/L)
Number of days not meeting standard 80 45 29 38
First day standard was not met 12-Jun 30-Jun 23-Jun 2-Jul
Last day standard was not met 17-Sep 28-Sep 15-Sep 21-Sep
Instantaneous DO (4.0 mg/L)
Number of days not meeting standard 91 70 93 94
First day standard was not met 12-Jun 5-May 12-Jun 5-May
Last day standard was not met 21-Sep 28-Sep 23-Sep 25-Sep
Number of days either standard was not met+ 91 P70 93 94
Number of days assessed 110 43 134 165
Reach 1 Station
TYCM2
Dissolved Oxygen (DO) Variable 2004 2005 2006 2007 2008 2009
Mean DO (mg/L) 6.7 6.8 7.2 6.9 6.8 6.2
Range of DO (mg/L) 2.1-16.9 0.9-17.7 1.8-17.5 1.8-17.0 1.8-17.1 0.5-18.7
Percent of DO concentrations < 5.0 mg/L 24.1% 32.3% 29.8% 37.6% 35.9% 36.1%
Percent of DO concentrations < 4.0 mg/L 8.0% 20.3% 15.5% 25.3% 17.3% 22.4%
Percent of DO concentrations < 3.0 mg/L 0.6% 5.6% 5.1% 8.8% 2.8% 7.0%
Percent of DO concentrations < 2.0 mg/L 0.0% 0.2% 0.2% 0.2% 0.1% 0.4%
Daily average DO (5.0 mg/L)
Number of days not meeting standard 23 38 22 14 10 27
First day standard was not met June 10 July 5 28-Jun 25-Jun 26-Jun 1-Jul
Last day standard was not met Aug 13 Aug 30 15-Sep 13-Sep 14-Sep 31-Aug
Instantaneous DO (4.0 m )
Number of days not meeting standard 52 69 56 99 77 59
First day standard was not met May 23 June 12 25-Jun 27-May 7-Jun 21-Jun
Last day standard was not met Sep 8 Sep 28 15-Sep 19-Sep 18-Sep 21-Sep
Number of days either standard was not
met+
53
70
59
99
78
59
Number of days assessed 145 169 193 214 169 169
9-18
Section 9
Table 9-6 (continued).
2009 Water Quality Results
Reach 1 Station
TYCM3
Dissolved Oxygen (DO) Variable 2004 2005 2006 2007 2008
Mean DO (mg/L) 6.5 6.6 6.6 6.6 7.2
Range of DO (mg/L) 1.2-11.6 1.5-13.0 2.7-12.4 2.6-14.1 5.1-11.9
Percent of DO concentrations < 5.0 mg/L 16.2% 17.7% 21.2% 22.0% 0.0%
Percent of DO concentrations < 4.0 mg/L 2.6% 6.1% 5.9% 8.7% 0.0%
Percent of DO concentrations < 3.0 mg/L 0.3% 0.5% 0.8% 0.2% 0.0%
Percent of DO concentrations < 2.0 mg/L 0.1% 0.1% 0.0% 0.0% 0.0%
Daily average DO (5.0 mg/L)
Number of days not meeting standard 24 25 31 24
First day standard was not met June 15 July 7 25-Jun 20-Jun
Last day standard was not met Aug 13 Aug 31 13-Sep 12-Sep
Instantaneous DO (4.0 mg/L)
Number of days not meeting standard 25 35 28 56
First day standard was not met June 14 July 7 26-Jun 18-Jun
Last day standard was not met Aug 11 Sep 3 5-Sep 14-Sep
Number of days either standard was not met+ 32 36 38
F 56
Number of days assessed 142 184 2 214 42
Reach 1 Station
TYCM4
Dissolved Oxygen (DO) Variable 2004 2005 2006 2007 2008
Mean DO (mg/L) 6.7 6.7 6.6 6.8 7.2
Range of DO (mg/L) 3.1-12.3 2.2-12.7 0.7-12.2 0.1-13.6 5.1-11.9
Percent of DO concentrations < 5.0 mg/L 10.6% 16.7% 19.6% 16.7% 0.0%
Percent of DO concentrations < 4.0 mg/L 1.4% 5.0% 5.5% 7.1% 0.0%
Percent of DO concentrations < 3.0 mg/L 0.0% 0.3% 1.0% 1.1% 0.0%
Percent of DO concentrations < 2.0 mg/L 0.0% 0.0% 0.3% 0.2% 0.0%
Dail average DO (5.0 m )
Number of days not meeting standard 13 28 37 24
First day standard was not met June 18 July 7 18-Jun 2-Jun
Last day standard was not met Sep 1 Aug 31 13-Sep 7-Sep
Instantaneous DO (4.0 m )
Number of days not meeting standard 9 27 31 45
First day standard was not met July 13 July 8 6-Jul 1-Jun
Last day standard was not met Aug 11 Aug 31 17-Sep 14-Sep
Number of days either standard was not met+ 15 33 44 46
Number of days assessed 141 180 211 214 42
9-19
Section 9
Table 9-6 (continued).
Blewett Falls Hydroelectric Plant
2009 Water Quality Results
Reach 2 Station
BF CM1
Dissolved Oxygen (DO) Variable 2004 2005 2006 2007 2008 2009
Mean DO (mg/L) 6.7 6.4 6.3 6.2 5.8 6.4
Range of DO (mg/L) 2.1-11.5 2.5-10.7 1.5-11.8 1.4-11.5 0.2-10.7 1.0-11.6
Percent of DO concentrations < 5.0 mg/L 7.1% 16.3% 20.3% 24.9% 32.0% 18.4%
Percent of DO concentrations < 4.0 mg/L 0.9% 2.4% 7.3% 9.5% 16.8% 6.3%
Percent of DO concentrations < 3.0 mg/L 0.2% <0.1% 1.1% 1.7% 7.8% 1.3%
Percent of DO concentrations < 2.0 mg/L 0.0% 0.0% 0.2% 0.1% 3.2% 0.1%
Dail average DO (5.0 m L)
Number of days not meeting standard 7 21 38 52 57 26
First day standard was not met June 14 July 1 12-Jun 11-Jun 7-Jun 5-Jul
Last day standard was not met Sept 2 Oct 3 19-Sep 26-Sep 14-Sep 24-Sep
Instantaneous DO (4.0 m L)
Number of days not meeting standard 12 27 40 67 71 36
First day standard was not met May 31 June 26 10-Jun 1-Jun 3-Jun 16-Jun
Last day standard was not met Sept 6 Oct 3 20-Sep 11-Oct 14-Sep 24-Sep
Number of days either standard was not
met'
12
33
47
71
75
39
Number of days assessed 141 183 192 202 177 163
Reach 2 Station
BFCMIA
Dissolved Oxygen (DO) Variable 2004 2005 2006 2007 2008 2009
Mean DO (mg/L) 6.6 5.8 5.9 5.9 5.0 5.9
Range of DO (mg/L) 2.5-10.0 0.3-11.6 0.1-11.7 0.5-13.5 0.1-10.2 0.7-11.1
Percent of DO concentrations < 5.0 mg/L 12.0% 33.3% 33.0% 38.4% 46.5% 26.9%
Percent of DO concentrations < 4.0 mg/L 3.2% 13.6% 17.2% 16.6% 30.9% 12.9%
Percent of DO concentrations < 3.0 mg/L 0.2% 4.6% 6.7% 6.2% 17.0% 4.3%
Percent of DO concentrations < 2.0 mg/L 0.0% 1.8% 3.2% 1.7% 10.4% 0.8%
Dail average DO (5.0 m L)
Number of days not meeting standard 11 54 63 58 90 45
First day standard was not met July 30 May 30 1-Jun 29-May 23-May 26-Jun
Last day standard was not met Sept 6 Oct 5 9-Sep 12-Sep 20-Sep 24-Sep
Instantaneous DO (4.0 mg/L)
Number of days not meeting standard 23 58 89 92 104 61
First day standard was not met July 30 June 6 23-May 29-May 6-May 26-Jun
Last day standard was not met Sept 6 Oct 5 13-Sep 16-Oct 17-Sep 24-Sep
Number of days either standard was not
met'
23
66
91
93
F 105
63
Number of days assessed 63 164 217 214 175 176
9-20
Section 9
Table 9-6 (continued).
2009 Water Quality Results
Reach 2 Station
BFCM2
Dissolved Oxygen (DO) Variable 2004 2005 2006 2007 2008
Mean DO (mg/L) 6.0 5.8 5.8 5.3 6.6
Range of DO (mg/L) 2.3-10.2 0.5-11.6 0.2-13.0 0.1-10.7 1.6-9.6
Percent of DO concentrations < 5.0 mg/L 24.4% 34.3% 35.1% 45.4% 14.8%
Percent of DO concentrations < 4.0 mg/L 8.6% 12.4% 17.4% 25.5% 6.1%
Percent of DO concentrations < 3.0 mg/L 0.7% 2.8% 4.5% 10.6% 1.6%
Percent of DO concentrations < 2.0 mg/L 0.0% 0.4% 1.2% 4.9% 0.0%
Daily average DO (5.0 mg/L)
Number of days not meeting standard 51 63 77 106 5
First day standard was not met May 15 May 14 1-Jun 29-May 7-Jun
Last day standard was not met Sept 6 Oct 3 6-Oct 10-Oct 11-Jun
Instantaneous DO (4.0 mg/L)
Number of days not meeting standard 58 65 84 119 8
First day standard was not met May 15 May 15 1-Jun 29-May 4-Jun
Last day standard was not met Sept 7 Oct 3 13-Sep 11-Oct 11-Jun
Number of days either standard was not met+ 62 72 88 121 8
Number of days assessed 150 183 217 214 42
Reach 2 Station
BFCM2A
Dissolved Oxygen (DO) Variable 2008 2009
Mean DO (mg/L) 5.1 5.5
Range of DO (mg/L) 0.2-10.8 0.1-10.3
Percent of DO concentrations < 5.0 mg/L 48.2% 34.5%
Percent of DO concentrations < 4.0 mg/L 31.0% 22.4%
Percent of DO concentrations < 3.0 mg/L 16.1% 14.4%
Percent of DO concentrations < 2.0 mg/L 8.1% 8.1%
Dail average DO (5.0 m )
Number of days not meeting standard 72 51
First day standard was not met 12-Jun 29-Jun
Last day standard was not met 23-Sep 27-Sep
Instantaneous DO (4.0 m )
Number of days not meeting standard 90 66
First day standard was not met 12-Jun 26-Jun
Last day standard was not met 8-Oct 27-Sep
Number of days either standard was not met+ 93 67
Number of days assessed 136 152
9-21
Section 9
Table 9-6 (continued).
2009 Water Quality Results
Reach 2 Station
BFCM3
Dissolved Oxygen (DO) Variable 2004 2005 2006 2007 2008
Mean DO (mg/L) 6.9 6.6 7.3 7.3 7.2
Range of DO (mg/L) 1.5-13.3 3.8-13.4 0.3-13.7 2.4-14.3 2.7-13.0
Percent of DO concentrations < 5.0 mg/L 5.3% 13.9% 18.6% 19.7% 14.3%
Percent of DO concentrations < 4.0 mg/L 0.7% 0.3% 6.0% 4.9% 6.1%
Percent of DO concentrations < 3.0 mg/L 0.1% 0.0% 0.7% 0.1% 0.3%
Percent of DO concentrations < 2.0 mg/L <0.1% 0.0% 0.1% 0.0% 0.0%
Daily average DO (5.0 mg/L)
Number of days not meeting standard 0 14 7 2 1
First day standard was not met NA July 1 9-Jun 6-Aug 11-Jun
Last day standard was not met NA Aug 30 24-Aug 25-Aug 11-Jun
Instantaneous DO (4.0 mg/L)
Number of days not meeting standard 14 4 41 41 7
First day standard was not met June 6 July 1 28-May 7-Jun 5-Jun
Last day standard was not met Aug 8 Aug 24 5-Sep 25-Aug 11-Jun
Number of days either standard was not met+ 14 15 42 42 7
Number of days assessed 147 183 207 204 41
+The total number of days that one or both of the North Carolina water quality standards for daily average
(5.0 mg/L) and instantaneous (4.0 mg/L) DO concentrations were not met.
¶The number of days assessed was the total number of days from May 1 to October 31 when DO concentrations
were recorded for at least half of the day.
"Station BFCMIA was added to the monitoring program on July 29, 2004.
§ Stations TYCM3, TYCM4, BFCM2, and BFCM3 were removed from the monitoring program on June 11, 2008.
"Stations TYCMI-2, TYCMI-3, and BFCM2A were added to the monitoring program on June 12, 2008.
9-22
Section 9 2009 Water Quality Results
9.2 Water Temperature in the Pee Dee River
9.2.1 Reach 1 - Tillery Dam to Turkey Top Creek
Water temperatures ranged from 12.8 to 34.4°C in Reach 1 from May through October
(Table 9-7). Mean water temperatures ranged from 23.4°C at Station TYCM1-3 to 23.9°C at
Station TYCM1-1 (Table 9-7). The maximum instantaneous temperature of 34.4°C occurred at
Station TYCM1-3 on July 12. Weekly mean temperatures were generally similar at all stations
throughout Reach 1 and exhibited a predictable seasonal trend of similar maximum temperature
(Figure 9-9). Weekly maximum mean temperatures occurred during the mid-August
(27.0 to 28.0°C) (Figure 9-9).
Table 9-7 Summary statistics of water quality variables from stations in Reach 1 of the
Pee Dee River below the Tillery Hydroelectric Plant, May 1 to October 31,
2009.

Water Quality Variable
TYCMl-1 Reach 1 stations
TYCMl-2 TYCMl-3
TYCM2
Mean temperature (°C) 23.9 23.6 23.4 23.8
Temperature range (°C) 15.8-29.9 13.9-32.1 12.8-34.4 13.1-32.5
Median pH 6.7 7.0 6.9 7.0
pH range 6.1-9.5 5.8-9.4 6.1-9.8 6.2-10.3
Mean specific conductance (p S/cm) 90 92 88 90
Specific conductance range (pS/cm) 22 - 138 69 - 118 66 - 105 67 - 156
9-23
Section 9
Tillery Reach 1 - 2009
30
d
R
L
0
U
N
d
d
L
L
a
L
Q
E
r
2009 Water Quality Results
20
0i
05/01/09
06/01/09 07/01/09 06/01/09 09/01/09 10/01/09 11/01/09
Date
6aa TYCM1-1 - TYCM1-2 - TYCM1-3 TYCM2
Figure 9-9 Weekly mean temperatures at continuous monitor stations in Reach 1 of the
Pee Dee River below the Tillery Hydroelectric Plant, May 1 to October 31,
2009.
9.2.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek
Water temperatures ranged from 16.2 to 32.0°C in Reach 2 during the May-October monitoring
period (Table 9-8). Mean water temperatures ranged from 24.3°C at Station BFCM1 to 24.5°C at
Station BFCMIA (Table 9-8). The Reach 2 maximum instantaneous temperature of 32.0°C
occurred at Station BFCMIA on August 21.
Weekly average water temperatures were similar throughout the monitoring period with a
summer time maximum (Figure 9-10). Weekly mean temperatures peaked around 29°C at all
stations during the second week of August.
10
9-24
Section 9 2009 Water Quality Results
Table 9-8 Summary statistics of water quality varia bles from stations in Reach 2 of the
Pee Dee River below the Bl ewett Falls Hy droelectric Plant, May 1 to October
31, 2009.
Reach 2 stations
Water Quality Variable BFCMI BFCMIA BFCM2A
Mean temperature (°C) 24.3 24.5 24.4
Temperature range (°C) 16.3 -29.8 16.8-32.0 16.2-31.4
Median pH 7.2 7.0 7.1
pH range 6.4-9.1 6.3-9.0 6.3-9.7
Mean specific conductance (p S/cm) 101 111 106
Specific conductance range (pS/cm) 79 - 141 73 -188 81 - 172
Blewett Falls Reach 2 - 2009
30
a?
ea
L
9
W
d
U
N
N
N
L
d
d
L
3
10
L
d
Q
E
d
01
06/01/09 06/01/09 07/01/09 08/01/09 09/01/09 10/01/09 11/01/09
Date
e e g BFCM1 - BFCM1A ° BFCWA
Figure 9-10 Weekly mean temperatures at continuous monitor stations in Reach 2 of the
Pee Dee River below the Blewett Falls Hydroelectric Plant, May 1 to October
31, 2009.
9-25
Section 9 2009 Water Quality Results
9.3 pH in the Pee Dee River
9.3.1 Reach 1 - Tillery Dam to Turkey Top Creek
Median pH values at stations in Reach 1 were slightly acidic nearly neutral (6.7 to 7.0)
(Table 9-7). Instantaneous pH values in Reach 1 ranged from 5.8 at Stations TYCM1 and
TYCM2 to 10.3 at Station TYCM2. Weekly mean pH values were less than 8.0 except at Station
TYCM1-1 during early May. Station TYCM2 typically had greater weekly mean pH values.
Tillery Reach 1 - 2009
10
9-
8
7
6
= 5
Q
4
3
2
1
0
05/01/09
06/01/09 07101109 08/01/09 09/01/09 10/01/09 11/01/09
Date
6aa TYCM1-1 -- TYCM1-2 TYCM1-3 TYCM2
Figure 9-11 Weekly mean pH values at continuous monitor stations in Reach 1 of the Pee
Dee River below the Tillery Hydroelectric Plant, May 1 to October 31, 2009.
The daily pH values fluctuated over a large range at Station TYCM2 and instantaneous values
often exceeded 9.0, particularly during May. These instantaneous pH values exceeded the upper
limit (9.0) of the North Carolina water quality standard for pH (NCDWQ 2007). Approximately
3.7% of the total number of measurements (n = 15,648) at Station TYCM2 exceeded 9.0.
Instantaneous pH values > 9.0 at the other monitoring stations occurred < 2.0% at the other
monitoring stations. The pH fluctuations at Station TYCM2 followed DO trends, probably as a
result of algal photosynthesis and respiration (Figure 9-12).
9-26
Section 9
11.0
10.0
9.0
8.0
x
Q.
7.0
6.0
5.0
20.0
18.0
16.0
J
14.0 E
c
12.0
a
x
10.0
w
8.0 0
W
0
6.0
4.0
4.0 2.0
0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00
Time
pH Dissolved Oxygen
Figure 9-12 Dissolved oxygen concentrations and pH values at Station TYCM2 in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
6, 2009.
9.3.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek
Median pH values were neutral (7.0 to 7.2) at Reach 2 stations (Table 9-8). Instantaneous pH
values in Reach 2 ranged from 6.3 at Stations BFCMIA and BFCM2A to 9.7 at Station
BFCM2A. Weekly mean pH values ranged from 6.5 to 8.2 (Figure 9-13). There was more daily
variation in pH values at Station 13FCM2A due to the greater amount of algal growth and
subsequent photosynthesis and respiration (Table 9-8).
2009 Water Quality Results
9-27
Section 9
9
8
7
6
5
2
Q
4
3
2
1
0
05f01/09
06/01/09 07101109 08/01/09 09/01/09
Date
eee BFCM1 - BFCM1A - BFCM2A
10/01/09 11/01/09
Figure 9-13 Weekly mean pH values at continuous monitor stations in Reach 2 of the Pee
Dee River below the Blewett Falls Hydroelectric Plant, May 1 to October 31,
2009.
Variation in pH was greatest throughout Reach 2 from late August through September which
coincided with a period of lower flow and warmer than average air temperatures. Less than one
percent of the total number of instantaneous pH values at all stations exceeded the North
Carolina water quality standard of 9.0.
9.4 Specific Conductance in the Pee Dee River
9.4.1 Reach 1 - Tillery Dam to Turkey Top Creek
Mean specific conductance values within Reach 1 ranged from 88 ,uS/cm at Station TYCM1-3
to 92 µS/cm at Station TYCM1-2 (Table 9-7). Instantaneous specific conductance values ranged
from 22 to 156 uS/cm. Weekly mean specific conductance values were higher especially at
Stations TYCM1-1 and TYCM1-2 than at Stations TYCM1-3 and TYCM2 (Figure 9-14).
Weekly mean specific conductance values at Stations TYCM1-1 and TYCM1-2 ranged from 75
to 109 µS/cm while values at Stations TYCM1-3 and TYCM2 ranged from 76 to 98 µS/cm.
Blewett Falls Reach 2 - 2009
2009 Water Quality Results
9-28
Section 9
2009 Water Quality Results
Tillery Reach 1 - 2009
110
M
100
_ 90
v 80
N
3
d 70
v
tv 60
3
59
O
U 40
v
!ft
N 30
Q
N
2D
10
0 i
05/01/09
06/01/09 07/01/09 08/01/09 09/01/09 10/01/09
Date
eee TYCM1-1 - TYCM1-2 - TYCM1-3 TYCM2
11/01/09
Figure 9-14 Weekly mean specific conductance values at continuous monitor stations in
Reach 1 of the Pee Dee River below the Tillery Hydroelectric Plant, May 1 to
October 31, 2009.
9-29
Section 9 2009 Water Quality Results
9.4.2 Reach 2 - Blewett Falls Dam to Below Hitchcock Creek
Mean specific conductance values at stations in Reach 2 ranged from 101 to 111 ,uS/cm for the
period from May through October (Table 9-8). Instantaneous specific conductance values
ranged from 73 to 188 PS/cm. Weekly mean specific conductance values at each station showed
similar temporal trends during the first two months of the monitoring period but were variable
during September and October (Figure 9-15).
Blewett Falls Reach 2 - 2009
180
170
160
150
ff 140
v 130
N
120
v 110
CU 100
3 90
80
O 70
U
60
d 5D
Q
N 40
30
2D
10
0
05/01/09 06/01/09 07/01/09 08/01/09 09/01/09 10/01/09 11/01/09
Date
6a BFCM1 - BFCM1A ° BFCM2A
Figure 9-15 Weekly mean specific conductance values at continuous monitor stations in
Reach 2 of the Pee Dee River below the Blewett Falls Hydroelectric Plant,
May 1 to October 31, 2009.
9-30
Section 10 - Summary
This monitoring program assessed the spatial and temporal patterns of DO concentrations in the
Pee Dee River downstream of the Tillery and Blewett Falls Hydroelectric Plants using in-situ
continuous water quality monitors from May through October, 2006-2009. The monitoring
program evaluated the longitudinal (upstream to downstream) and latitudinal (east bank to west
bank) differences in the DO regimes in the river associated with power plant operations over a
seasonal period of stratification and de-stratification of the Project reservoirs. The monitoring
program also evaluated spatial and temporal patterns of temperature, pH, and specific
conductance in both reaches below each power plant.
Continuous monitors were placed in the river below each power plant and within the sections
currently or previously designated by the NCDWQ under Section 303(d) of the Clean Water Act
as impaired due to low DO concentrations. The NCDWQ listed the 15.3-mile reach from the
Tillery Dam to the mouth of Turkey Top Creek and the 6.3 mile reach from the Blewett Falls
Dam to the mouth of Hitchcock Creek has been previously listed due to low DO concentrations.
Dissolved oxygen concentrations in the Pee Dee River from the Tillery Hydroelectric Plant to the
Turkey Top Creek confluence were below one or both water quality standards on some days
from mid-May to early October depending upon station location. This period corresponded with
stratification of the hypolimnion of Lake Tillery and the subsequent low DO concentrations of
lake water released during power plant generation into the river.
Dissolved oxygen concentrations generally increased throughout Reach 1 with increased distance
from the Tillery Hydroelectric Plant due to re-aeration in the river channel and tributary inflow.
Dissolved oxygen concentrations also generally increased from east river bank to west river bank
along the N.C. Highway 731 Bridge. Dissolved oxygen concentrations in Reach 1 were affected
by natural diel cycles of algal photosynthesis and respiration, tributary inflow, and power plant
generated flows. Dissolved oxygen concentrations usually increased during daylight hours and
decreased at night as a function of algal photosynthesis and respiration. Power plant generation
flows affect on DO dynamics were most evident when power generation occurred after DO
concentrations began to rise during the morning hours. Dissolved oxygen concentrations in the
river would decrease when the hypolimnetic water from Lake Tillery was released during power
generation. This effect was most evident at Station TYCM1-1, located approximately 0.2 miles
downstream of the Tillery Plant.
Dissolved oxygen concentrations in Reach 1 were below the instantaneous and daily average DO
water quality standards on days that the Tillery Hydroelectric Plant did not generate power.
Dissolved oxygen concentrations at Station TYCM1-1 were below one or both water quality
standards on non-power generation days more than other stations in Reach 1.
Dissolved oxygen concentrations in the Pee Dee River below the Blewett Falls Hydroelectric
Plant were below one or both water quality standards on some days from mid-May to early
October. The period of lowest DO concentrations in Reach 2 also corresponded with stratified
DO conditions in Blewett Falls Lake when hypolimnetic DO concentrations were below
5.0 mg/L.
10-1
Section 10 Summary
Dissolved oxygen concentrations did not increase throughout Reach 2 with increased distance
from the Blewett Falls Hydroelectric Plant. Both water quality standards were met more often at
Station BFCM3, the lowermost monitoring station. The number of days not meeting the water
quality standards for DO concentrations and the percentage of DO concentrations less than
5.0 mg/L were the greatest at Station BFCM2, located approximately 3.4 miles downstream of
the power plant.
Filamentous algae that accumulated on the continuous monitor at Station BFCM3 during late
July and August contributed to periods of low DO concentrations and fluctuations in daily pH
values at this station. The accumulated algae caused wide fluctuations in DO concentrations and
affected the continuous monitor's ability to measure DO concentrations accurately. There
appeared to be a source of nutrients entering the river upstream of this continuous DO monitor
that contributed to the profuse algal growth.
The period that DO concentrations did not meet the water quality standards occurred later in the
year during 2007 in both Reaches 1 and 2 (i.e., mid May through mid October) compared to the
period documented in other years (i.e., late May through early September). This temporal
difference was attributable to climatological differences, reservoir stratification patterns, and
subsequent power plant generation. The year 2007 was marked by a warm, dry spring and hot
summer. However, in all years, reservoir destratification and attainment of the state water
quality standards occurred by early to late September to mid October depending the annual
climatological conditions, reservoir inflow, and station location. Spatial trends in DO
concentrations in the two river reaches were similar during all years.
Water temperatures in both reaches corresponded to changes in ambient air temperatures and
precipitation. Weekly mean temperatures peaked during the mid to late August in Reach 1 and
peaked during late July in Reach 2. Temperatures were more consistent among stations within
Reach 2 over the study period due to the shorter length of the reach and fewer major tributaries
within Reach 2. Changes in water temperatures were minimal in both study reaches with the
arrival of hypolimnetic water released from the power plants.
The median pH values for stations in Reaches 1 and 2 were slightly acidic to near neutral (6.7 to
7.3). There was considerable temporal variation in weekly median pH values for both reaches.
This variability was mainly attributed to algal photosynthesis and respiration diel cycles. The
weekly mean pH values ranged from 6.3 to 8.6 in Reach 1, while weekly mean pH values ranged
from 6.4 to 8.2 in Reach 2. Stations TYCM2 and BFCM3 had periods of large daily fluctuations
and high pH values that likely resulted from algal photosynthesis and respiration cycles.
Specific conductance concentrations were more similar among Reach 2 stations than among
Reach 1 stations. At stations in Reach 2, mean specific conductance concentrations only ranged
from 101 to 120 uS/cm. Reach 2 was shorter with fewer large tributaries. In contrast, Reach 1
had several large tributaries, including the Rocky River and Brown Creek, which influenced
specific conductance concentrations with increasing distance downstream of the Tillery
Hydroelectric Plant. In Reach 1, mean specific conductance concentrations were lowest at
Stations TYCM1-1, TYCM1-2, TYCM1-3 and TYCM2 but increased substantially at Stations
TYCM3 and TYCM4 located below the Rocky River and Brown Creek, respectively.
10-2
Section 11 - References
North Carolina Division of Water Quality. 2006. North Carolina water quality assessment and
impaired waters list (2006 integrated 305(b) and 3030(d) list). Public review draft.
February 2006. North Carolina Department of Environment and Natural Resources,
Division of Water Quality, Raleigh, North Carolina.
2007. NC DENR-Division of Water Quality "Redbook." Surface waters and wetlands
standards. NC Administrative Code 15A NCAC 0213.0100, .0200 & .0300. Amended
effective: May 1, 2007. North Carolina Department of Environment and Natural
Resources, Division of Water Quality, Raleigh, North Carolina.
2008. Basinwide Water Quality Plans-Yadkin-Pee Dee River Basin. North Carolina
Department of Environment and Natural Resources, Division of Water Quality, Raleigh,
North Carolina.
2010. North Carolina water quality assessment and impaired waters list (2010 integrated
305(b) and 3030(d) list). EPA Approved. August 2010. North Carolina Department of
Environment and Natural Resources, Division of Water Quality, Raleigh, North Carolina.
Progress Energy. 2003. Initial consultation document. Yadkin-Pee Dee River Project FERC
No. 2206. February 2003. Progress Energy, Raleigh, NC.
2004. RWG meeting summary notes, templates, and study plans. Yadkin-Pee Dee River
Project FERC No. 2206. January 2004. Progress Energy.
2005a. Yadkin-Pee Dee River Project FERC No. 2206. Intensive temperature and
dissolved oxygen study of the Pee Dee River below the Tillery and Blewett Falls
Hydroelectric Plants. Water Resources Group. Issues Nos. 7 and 8 - Lake Tillery and
Blewett Falls Lakes and Tailwaters Water Quality. November 2005. Progress Energy.
2005b. Yadkin-Pee Dee River Project FERC No. 2206. Continuous water quality
monitoring in the Pee Dee River below the Tillery and Blewett Falls Hydroelectric
Plants. Water Resources Group. Issues Nos. 7 and 8 - Lake Tillery and Blewett Falls
Lakes and Tailwaters Water Quality. November 2005. Progress Energy.
2006a. Yadkin-Pee Dee River Project FERC No. 2206. Monthly water quality
monitoring study of Lake Tillery, Blewett Falls Lake, and associated tailwaters. Water
Resources Group. Issues Nos. 7 and 8 - Lake Tillery and Blewett Falls Lakes and
Tailwaters Water Quality. April 2006. Progress Energy. April 2006.
2006b. Application for license. Yadkin-Pee Dee River Project FERC No. 2206.
Submitted by Progress Energy, Raleigh, North Carolina.
11-1
Section II
References
2006c. Yadkin-Pee Dee River Hydroelectric Project FERC No. 2206. Continuous water
quality monitoring in the Pee Dee River below the Tillery and Blewett Falls
Hydroelectric Plants, May-October 2005.
2007a. Biology Program Procedures Manual (Procedures NR-00058, NR-00069, and
NR-00071). Progress Energy Carolinas, Inc., Raleigh, North Carolina.
2007b. Biology Program Quality Assurance Manual. Progress Energy Carolinas, Inc.,
Raleigh, NC.
2007c. Application for Water Quality Certification Pursuit to Section 401 (a) (1) of the
Clean Water Act. Yadkin-Pee Dee River Hydroelectric Project, FERC Project No. 2206.
Progress Energy Carolinas, INC., Raleigh, NC. May 2007.
2008. Biology Program Procedures Manual (Procedures NR-00071). Progress Energy
Carolinas, Inc., Raleigh, North Carolina.
Southeast Regional Climate Center. 2009. Historic climate summaries for Wadesboro, NC
COOP Station 318964. http://www.dnr.state.sc.us. Columbia, South Carolina.
State Climate Office of North Carolina. 2009
Wadesboro, NC COOP Station 318964.
Carolina.
Precipitation and mean daily temperature for
http://www.nc-climate.ncsu.edu Raleigh, North
YSI. 2003. Environmental Monitoring Systems Operations Manual. YSI Incorporated. Yellow
Springs, Ohio.
11-2
APPENDICES
APPENDIX A
SUMMARY OF CONTINUOUS MONITOR PERFORMANCE IN REACHES I AND 2 OF
THE PEE DEE RIVER BELOW THE TILLERY AND BLEWETT FALLS
HYDROELECTRIC PLANTS, 2006-2009
Table A-1 Number and percentage of water quality parameter readings that were
recorded and retained for stations in Reaches 1 and 2 of the Pee Dee River
below the Tillery and Blewett Falls Hydroelectric Plants, May 1 to
October 31, 2006.
Number of Water Quality Parameter Readings
Specific
Station Temperature Dissolved Oxygen Conductance pH

Reach 1
TYCMI-1 17,856 17,856 17,856 17,856
TYCM2 17,760 17,760 17,760 17,760
TYCM3 19,776 19,776 19,776 19,776
TYCM4 18,624 18,624 18,624 18,624
Reach 2
BFCMI 17,376 17,376 17,376 17,376
BFCMIA 19,968 19,907 19,968 19,968
BFCM2 19,968 19,967 19,968 19,968
BFCM3 18,720 18,720 18,720 18,720
Percentage of Water Quality Parameter Readings
Specific
Station Temperature Dissolved Oxygen Conductance pH
Reach 1
TYCM1-1 100.0% 100.0% 100.0% 100.0%
TYCM2 100.0% 100.0% 100.0% 100.0%
TYCM3 100.0% 100.0% 100.0% 100.0%
TYCM4 100.0% 100.0% 100.0% 100.0%
Reach 2
BFCM1 100.0% 100.0% 100.0% 100.0%
BFCMIA 100.0% 99.7% 100.0% 100.0%
BFCM2 100.0% 100.0% 100.0% 100.0%
BFCM3 100.0% 100.0% 100.0% 100.0%
Mean 100.0% 100.0% 100.0% 100.0%
Appendix A-1
Table A-2 Number and percentage of water quality parameter readings that were
recorded and retained for stations in Reaches 1 and 2 of the Pee Dee River
below the Tillery and Blewett Falls Hydroelectric Plants, May 1 to
October 31, 2007.
Number of Water Quality Parameter Readings
Specific
Station Temperature Dissolved Oxygen Conductance pH

Reach 1
TYCM I -1 20,160 20,160 20,160 20,160
TYCM2 20,256 20,256 20,256 20,256
TYCM3 19,872 19,872 19,872 19,872
TYCM4 20,064 20,064 20,064 20,064
Reach 2
BFCMI 20,352 19,111 20,352 20,352
BFCMIA 20,256 20,256 20,256 20,256
BFCM2 20,160 20,160 20,160 20,160
BFCM3 19,721 18,706 19,721 19,872
Percentage of Water Quality Parameter Readings
Specific
Station Temperature Dissolved Oxygen Conductance pH
Reach 1
TYCM1-1 100.0% 100.0% 100.0% 100.0%
TYCM2 100.0% 100.0% 100.0% 100.0%
TYCM3 100.0% 100.0% 100.0% 100.0%
TYCM4 100.0% 100.0% 100.0% 100.0%
Reach 2
BFCM1 100.0% 93.9% 100.0% 100.0%
BFCMIA 100.0% 100.0% 100.0% 100.0%
BFCM2 100.0% 100.0% 100.0% 100.0%
BFCM3 99.2% 94.1% 99.2% 100.0%
Mean 99.9% 98.5% 99.9% 100.0%
Appendix A-2
Table A-3 Number and percentage of water quality parameter readings that were
recorded and retained for stations in Reaches 1 and 2 of the Pee Dee River
below the Tillery and Blewett Falls Hydroelectric Plants, May 1 to
October 31, 2008.
Number of Water Quality Parameter Readings
Specific
Station Temperature Dissolved Oxygen Conductance pH
Reach 1
TYCMI-1 16,460 16,460 16,460 16,460
TYCM I -2 10,170 10,170 10,170 10,170
TYCMI-3 12,656 12,656 12,565 9,967
TYCM2 16,017 16,017 16,017 16,017
TYCM3 3,765 3,765 3,765 3,765
TYCM4 2,134 2,134 2,134 2,134
Reach 2
BFCMI 16,745 16,745 16,745 16,745
BFCMIA 16,737 16,737 16,737 16,737
BFCM2 3,975 3,975 3,975 3,975
BFCM2A 12,750 12,750 12,750 12,750
BFCM3 3,819 3,819 3,819 3,819
Percentage of Water Quality Parameter Readings
Specific
Station Temperature Dissolved Oxygen Conductance pH
Reach 1
TYCM1-1 99.6% 91.4% 99.6% 99.6%
TYCM1-2 80.9% 80.9% 80.9% 80.9%
TYCM1-3 99.9% 99.9% 99.9% 99.9%
TYCM2 96.9% 96.9% 96.9% 96.9%
TYCM3 99.5% 99.5% 99.5% 99.5%
TYCM4 56.3% 56.3% 56.3% 56.3%
Reach 2
BFCM1 99.9% 99.9% 99.9% 99.9%
BFCMIA 99.9% 89.9% 99.9% 99.9%
BFCM2 99.9% 99.9% 99.9% 99.9%
BFCM2A 99.9% 99.9% 99.9% 99.9%
BFCM3 96.0% 96.0% 96.0% 96.0%
Mean 93.4% 92.9% 93.9% 93.9%
Appendix A-3
Table A-4 Number and percentage of water quality parameter readings that were
recorded and retained for stations in Reaches 1 and 2 of the Pee Dee River
below the Tillery and Blewett Falls Hydroelectric Plants, May 1 to
October 31, 2009.
Number of Water Quality Parameter Readings
Specific
Station Temperature Dissolved Oxygen Conductance pH
Reach 1
TYCMI-1 15,552 15,552 15,552 15,552
TYCMI-2 14,304 13,300 14,304 14,304
TYCMI-3 15,264 15,264 15,264 15,264
TYCM2 15,648 15,648 15,648 15,648
Reach 2
BFCMI 15,431 15,388 14,163 15,431
BFCMIA 16,320 16,320 15,337 16,320
BFCM2A 16,128 13,569 16,128 16,128
Percentage of Water Quality Parameter Readings
Specific
Station Temperature Dissolved Oxygen Conductance pH
Reach 1
TYCM1-1 100.0% 100.0% 100.0% 100.0%
TYCM1-2 100.0% 93.0% 100.0% 100.0%
TYCM1-3 100.0% 100.0% 100.0% 100.0%
TYCM2 100.0% 100.0% 100.0% 100.0%
Reach 2
BFCMI 91.9% 91.7% 84.4% 91.7%
BFCMIA 100.0% 100.0% 94.0% 100.0%
BFCM2A 100.0% 84.1% 100.0% 100.0%
Mean 98.8% 95.5% 96.1% 98.8%
Appendix A-4
Table A-5 Periods that water quality data were not recorded by YSI° 600XLM
continuous monitors or data were omitted upon review for stations in
Reaches 1 and 2 during 2007.
Parameters
Station Duration Affected+ Description
BFCMI October 31- DO DO charge ranged from 99-100. DO probe was determined to
November 13 be bad and replaced.
BFCM3 August 4-10 Temp, DO, Readings were erratic and considered invalid.
Sp Cond
BFCM3 August 4- DO DO probe was bad upon pulling meter. All DO data
September 5 considered invalid.
-'Parameters monitored were temperature (Temp), dissolved oxygen (DO), pH, and specific conductance (sp Cond).
All represents all four monitored parameters.
Table A-6 Periods that water quality data were not recorded by YSI° 600XLM
continuous monitors or data were omitted upon review for stations in
Reaches 1 and 2 during 2008.
Parameters
Station Duration Affected+ Description
TYCM4 May 3-20 All Meter was lost.
TYCMI-1 September 11-25 DO DO charge decreased to 0. A small tear was visible in the
DO membrane.
TYCM1-3 September 11- pH Original pH probe was deemed bad upon retrieval and the
October 9 next pH probe was deemed bad upon retrieval as well.
TYCMI-2 September 30- All Batteries failed and monitor stopped logging data.
Ocober 9
TYCMI-2 October 14- All Batteries failed and monitor stopped logging data.
October 31
BFCM3 May 1 All Meter was not deployed until the 2nd of May.
-'Parameters monitored were temperature (Temp), dissolved oxygen (DO), pH, and specific conductance (sp Cond).
All represents all four monitored parameters.
Appendix A-5
Table A-7 Periods that water quality data were not recorded by YSI® 600XLM
continuous monitors or data were omitted upon review for stations in
Reaches 1 and 2 during 2009.
Parameters
Station Duration Affected+ Description
TYCM1-2 June 19-June 29 DO DO charge dropped to 0. A small hole was noticed in DO
membrane.
BFCMI September 8- All Battery power. Battery connection circuit was determined to
September 22 be bad.
BFCMI October 7- Sp Cond Specific conductance was reading out of range when field
October 20 calibrating. All specific conductance data considered invalid
for this time period.
BFCMIA October 20- Sp Cond Specific conductance was reading out of range when field
October 31 calibrating. All specific conductance data considered invalid
for this time period.
BFCM2A August 27 - DO Air bubble in membrane when meter was pulled.
September 8
-'Parameters monitored were temperature (Temp), dissolved oxygen (DO), pH, and specific conductance (sp Cond).
All represents all four monitored parameters.
Appendix A-6