Southern Company Generation. 241 Ralph McGill Boulevard, NE BIN 10193 Atlanta, GA 30308-3374 404 506 7219 tel
November 10, 2017 Wallace Dam Project (FERC No. 2413-117) Wallace Dam Relicensing Study Results Meeting Summary – Second Season Ms. Kimberly D. Bose, Secretary Federal Energy Regulatory Commission 888 First Street, N.E. Room 1-A- Dockets Room Washington, D.C. 20426 Dear Secretary Bose: On behalf of Georgia Power Company, Southern Company is filing with the Federal Energy Regulatory Commission (Commission) the Wallace Dam relicensing study results meeting summary for our second season of study in compliance with the Commission’s Integrated Licensing Process regulations at 18 CFR § 5.15(c)(1). Along with this cover letter, this filing consists of the following parts: Attachment A – Study Results Meeting Summary Attachment B – Study Results Meeting Agenda Attachment C – Study Results Meeting Sign-In Sheets Attachment D – Study Results Meeting Presentations Attachment E – Study Results Meeting Transcripts
If you require further information, please contact me at 404.506.7219 or [email protected]. Sincerely, Courtenay R. O’Mara, P.E. Hydro Licensing & Compliance Supervisor Attachments cc: FERC/OEP – Allan Creamer Geosyntec – Steve Layman, Ph.D. Troutman Sanders – Hallie Meushaw, Fitzgerald Veira
ATTACHMENT A STUDY RESULTS MEETING SUMMARY
Wallace Dam Relicensing FERC No. P-2413-117
Summary of Updated Study Results Meeting
October 17, 2017
Rock Eagle 4H Center 350 Rock Eagle Road, Eatonton, GA 31024
The Project Operations Overview was provided and the results of the Water Resources Updated Study and Aeration Methods to Enhance Summer Dissolved Oxygen in the Wallace Dam Tailrace Area Study were presented.
There were no questions about the studies and no objections to the study methods were raised.
There were no requests for study modifications or additional studies.
The meeting presentations and court reporter transcript for this meeting were filed concurrently with this summary with the Federal Energy Regulatory Commission.
ATTACHMENT B STUDY RESULTS MEETING AGENDA
Wallace Dam / Lake Oconee FERC Relicensing (P-2413-117)
Updated Study Results and Preliminary Licensing Proposal Meetings October 17, 2017
Rock Eagle 4-H Center Sutton Hall
AGENDA
Updated Study Results Meeting (9:00 – 11:30 a.m.):
9:00 a.m. – Introductions, Safety, Review of Operations
9:30 a.m. – Updated Study Results
9:30 a.m. - Presentation of “Water Resources” Updated Study Results (2nd Year)
10:30 a.m. - Presentation of “Aeration Methods to Enhance Summer Dissolved Oxygen in the Wallace Dam Tailrace Area” Study Results
11:30 a.m. – Lunch
Preliminary Licensing Proposal Meeting (1:00 – 3:00 p.m.):
1:00 p.m. - Review of 1st Year Study Results from All Studies
2:00 p.m. – Presentation of Georgia Power’s PLP & Discussion of PLP
3:00 p.m. – Next Steps/Review of Schedule/Adjourn
ATTACHMENT C STUDY RESULTS MEETING SIGN-IN SHEETS
ATTACHMENT D STUDY RESULTS MEETING PRESENTATIONS
Updated Study Results Meeting
October 17, 2017Rock Eagle 4H Center
Introduction
Courtenay O’Mara, P.E.Southern Company
3
Tuesday, October 17, 2017Updated Study Results Meeting: 9:00 a.m. – 11:30 a.m.
• Introductions/Safety/ Review of Operations (9:00 – 9:30 a.m.)• Presentation of “Water Resources” Updated Study Results (9:30 – 10:30 a.m.)• Presentation of “Aeration Methods to Enhance Summer Dissolved Oxygen in
the Wallace Dam Tailrace Area” Study Results (10:30 – 11:30 a.m.)
Lunch will be provided 11:30 a.m.
Preliminary Licensing Proposal Meeting: 1:00 – 3:00 p.m.
• Review of 1st Year Study Results from All Studies (1:00 – 2:00 p.m.)• Presentation of Georgia Power’s PLP & Discussion of PLP (2:00 – 3:00 p.m.)• Next Steps / Review of Schedule/Adjourn
Updated Study Results &Preliminary Licensing Proposal
Meeting Agenda
4
Oct 2017
5
Master Schedule for 2nd Season Study Implementation
Activity Start Date Completion Date or Deadline
Conduct Field Studies:Water Resources October 1, 2016 September 30, 2017Aeration Methods to Enhance
Summer Dissolved Oxygen in Tailrace Area
April 1, 2016 September 30, 2017
File Progress Reports (2nd Season) NA August 31, 2017File Final Study Reports (2nd Season) NA October 11, 2017Hold Study Results Meetings (2nd
Season)October 17, 2017
File Updated Study Results Meeting Summary
November 10, 2017
File Update Study Results Meeting Summary Disagreements
December 11, 2017
File Response to Updated Study Results Meeting Summary Disagreements
January 9, 2018
FERC Resolves Meeting Summary Disagreements
February 8, 2018
6
Project Boundary
Project Recreation Facilities
U.S. Forest Service Recreation Access
Parks Ferry Park
Sugar CreekBoat Ramp
Armour BridgeOld Salem Park
Long ShoalsBoat Ramp
Lawrence Shoals Park
Tailrace Fishing Area
Redlands Recreation Area
Swords Recreation Area
Dyar Pasture Recreation Area
Project Boundary
Downstream Extent of Project Boundary
within Lake Sinclair
Project Operations
Laurie Munn, P.E.Southern Company
8
Project Facilities
Lake Oconee
Powerhouse
Spillway
Flow
Tailrace Fishing
AreaTransmission
Line
9
Oconee River: RM 172.7 Begin Power Delivery: 1979 Number of Units: 6 Production Capacity: 321,300 kW Reservoir Area: 19,050 Acres Normal Full Pool: 435 feet Full Reservoir Storage: 370,000 ac-ft Useable Storage 345,000 ac-ft Normal Operating Range: 433.5 feet to 435.00 feet Average Annual Inflow: 2,037 cfs Operation: Pumped Storage
Project Statistics
10
What is Pumped Storage?
• Move water between two reservoirs located at different elevations.
• Upper reservoir generates power during peak times and pumps water back from lower reservoir during off-peak times.
• Wallace Dam Project operates Lake Oconee as the upper reservoir.
• Sinclair Dam Project operates Lake Sinclair as the lower reservoir.
11
Normal Operations at Wallace Dam
• Powerhouse contains 6 units, 2 conventional units and 4 reversible units.
• Total generating capacity is 321.3 MW
• Generation cycle starts at or near elevation 435 ft. and ends near elevation 433.5 ft.
• During nighttime pumping, Lake Oconee refills to elevation 435 ft.
• Generation is typically highest during the summer months when the electricity demand is the highest.
12
Design Characteristics of the Wallace Dam Units
Unit Nameplate Capacity of Turbines (HP)
Nameplate Capacityof Generators
(MW)
Maximum Hydraulic Capacity (cfs)
Best Gate Hydraulic Capacity (cfs)
Commercial Operation Date
1a 73,000 52.20 8,390 7,200 19802a 73,000 52.20 8,825 7,250 19803 78,000 56.25 8,600 7,900 19804 78,000 56.25 8,600 7,900 19805a 73,000 52.20 8,210 7,250 19806a 73,000 52.20 7,920 7,250 1979Total 321.3 50,545 NA
13
Average Inflows
14
Total Generation 2012 - 2016
Year MW hr % of Generation from Pumpback Annual Inflows
2012 Total 356,364 96.13% Low Inflow
Conventional 13,774 735 cfs
Pumpback 342,590
2013 Total 303,976 72.85% Average Inflow
Conventional 82,527 2851 cfs
Pumpback 221,449
2014 Total 317,511 81.14% Average Inflow
Conventional 59,889 1977 cfs
Pumpback 257,622
2015 Total 342,111 69.81% Average Inflow
Conventional 103,300 2847 cfs
Pumpback 238,811
2016 Total 361,227 84.68% Average Inflow
Conventional 55,358 1814 cfs
Pumpback 305,869
15
Wallace Dam Weekly Operations
Normal Inflow Week of 1,591 cfs, Average Annual Inflow = 2,037 cfs
16
Reservoir Elevations-Normal Year 2013
430.00
431.00
432.00
433.00
434.00
435.00
436.00
Jan-13 Feb-13 Apr-13 Jun-13 Jul-13 Sep-13 Oct-13 Dec-13
Lake OconeeDaily Maximum and Minimum Elevations
2013
Daily Maximum Elevation Daily Minimum Elevation
17
Reservoir Elevations-Drought 2007
430.00
431.00
432.00
433.00
434.00
435.00
436.00
Jan-07 Feb-07 Apr-07 Jun-07 Jul-07 Sep-07 Oct-07 Dec-07
Lake OconeeDaily Maximum and Minimum Elevations
2007
Daily Maximum Elevation Daily Minimum Elevation
18
Lake Levels in Recent Droughts
19
Wallace Dam Operations Summary
• Large Reservoir Built for Peaking Power Generation and Pumpback.
• No minimum flow – Wallace Dam discharges directly into Lake Sinclair. There is no riverine stretch between Lake Oconee and Lake Sinclair.
• Reservoir elevation fluctuations are less than 2.0 feet for 100% of the time (433 to 435).
20
Questions?
Updated Water Resources Study
Study Results Meeting
Tony DoddOctober 17, 2017
2
Study Objective – Second Season of Water Quality Monitoring
• Characterize the effects of continued project operation on water quality in Lake Oconee and the tailrace area within the project boundary
• Initial Water Resources Study Report filed in November 2016 presented results of first season of water quality monitoring (Jul 2015 – Sep 2016)
• Updated Water Resources Study Report filed in October 2017 presents results of second season of water quality monitoring (Oct 2016 – Sep 2017), including:
• Continuous tailrace water quality monitoring
• Quarterly reservoir water quality monitoring
3
Study Plan Included Two Seasons (Years) of Water Quality Monitoring
1st Season (2015-2016)
Water quality monitoring in Lake Oconee• Monthly vertical profiles• Quarterly water chemistry• Hourly vertical profiles of summer
pumpback/generationWater quality monitoring in the tailrace• Continuous monitoring of dissolved oxygen
(DO) and water temperature• Hourly transect monitoring of summer
pumpback/generation
2nd Season (2016-2017)
Water quality monitoring in the tailrace• Continuous monitoring of DO and water
temperatureWater quality monitoring in Lake Oconee• Quarterly vertical profiles• Quarterly water chemistry
Initial Water Resources Study Report Updated Water Resources Study Report
4
Study Area
• Lake Oconee and the Wallace Dam tailrace area downstream to the project boundary at Georgia Hwy 16
• 19,050 acres• Classified uses: recreation,
drinking-water and fishing Lake Oconee
Tailrace
Project Boundary
Study Methods
6
Continuous Water Quality Monitoring in the Tailrace
• Same methods as first season of monitoring• Solar powered buoy with remote telemetry
installed July 2015• YSI 6600 data sonde• Continuous (hourly) monitoring of:
• Dissolved oxygen• Water temperature• pH• Turbidity• Specific conductivity
• Routine monthly maintenance• Operated through Sep 30, 2017
Station OCTR – continuous tailrace monitoring was conducted from July 2015 through September 2017
7
Data Analysis for Continuous Tailrace Monitoring
• Continuous DO and temperature data aligned with real-time project operational data
Generation begins
8
Lake Oconee Water Quality Monitoring Locations – Second Season
• Same stations as first season of monitoring
OC1
OC2
OC3
OC4
OC5
OC6
OC7
OC8
OC9
OCTR
StationMainstem Reservoir
Tributary Embayment
Quarterly Vertical Profile
Quarterly Water
Chemistry
OC1
OC2
OC3
OC4
OC5
OC6
OC7
OC8
OC9
9
Quarterly Water Quality Monitoring in Lake Oconee
• Vertical profiles• 9 locations• Measured water temperature, DO, pH,
and conductivity from surface to bottom at 1-meter intervals
• Water chemistry • 6 locations (OC1,2,4,7,8,9)• Grab samples collected at 1-m depth• 12 parameters analyzed
Water Chemistry Parameters
Alkalinity (mg/L)Turbidity (NTU)Magnesium (mg/L)Calcium (mg/L)Hardness (mg/L as CaCO3)Total Phosphorus (mg/L)Nitrate (mg/L)Nitrite (mg/L)Ammonia (mg/L)Chlorophyll a (mg/L)Biochemical oxygen demand (mg/L)Chemical oxygen demand (mg/L)
Study Results – Continuous Water Quality in the Tailrace
11
Summary of First Season of Tailrace Monitoring (2015-2016)
• Continuous water quality monitoring in the tailrace demonstrated DO values below 4.0 mg/L limited to June, July, and first week of August
• Hourly water quality transects in the tailrace showed relatively uniform water quality throughout the study area
• DO values decreased in the tailrace after generation and remained lower until the daylight interim period began, due in part to photosynthesis
12
Daily Average Water Temperature and DO from Over 2+ Years of Monitoring
• Days of monitoring• 2015: 184 days
• 2016: 366 days
• 2017: 273 days• Seasonal variation similar
between years
• Warmer winter water temperatures in 2017
• Lower summer DO concentrations in 2017
2016 20172015
13
Summary of Continuous Tailrace Water Quality Data
Attribute Year 1 (WY 2016)10/1/15 – 9/30/16
Year 2 (WY 2017)10/1/16 – 9/30/17
Hourly readings 8,803 8,712
Days of missing data 3 11
Average temperature 20.2°C (68.4°F) 20.6°C (69.1°F)
Average DO (mg/L) 7.0 7.0
No. of hourly readings <4 mg/L 755 1,216
% of hourly readings <4 mg/L 8.6% 14.0%
14
Tailrace Weekly Plot – November 2016
• DO range: 7.4 – 8.9 mg/L• Temperature range: 20.7 – 22.9°C (69.3 – 73.2°F)
15
Tailrace Weekly Plot – May 2017
• DO range: 3.4 – 6.8 mg/L• Temperature range: 21.0 – 25.5°C (69.8 – 77.9°F)
16
Tailrace Weekly Plot – July 2017
• DO range: 1.5 – 4.9 mg/L• Temperature range: 27.4 – 30.8°C (81.3 – 87.4°F)
17
Tailrace Weekly Plot – September 2017
• DO range: 4.9 – 7.5 mg/L• Temperature range: 27.8 – 29.0°C (82.0 – 84.2°F)
Study Results – Quarterly Water Quality in Lake Oconee
19
Summary of First Season of Reservoir Water Quality Monitoring
• Monthly water quality profiles characterize the extent of mixing in Lake Oconee due to pumped storage operations
• Forebay and other mainstem locations weakly stratified in early summer; completely mixed by August
• Quarterly water quality profiles over many years indicate more complete mixing in mainstem reservoir locations when compared to tributary embayments or upper reservoir stations
• Quarterly water chemistry indicated good overall water quality and mesotrophic conditions
• Hourly water quality profiles in the reservoir indicated temporal stratification during generation and quiescent phases of Wallace Dam operation
20
Quarterly Vertical Profiles, 2016-2017
Station OC1 – Wallace Dam Forebay
21
Quarterly Vertical Profiles, 2016-2017
Station OC2 – Richland Creek Embayment
22
Quarterly Vertical Profiles, 2016-2017
Station OC3 – Mainstem Reservoir
23
Quarterly Vertical Profiles, 2016-2017
Station OC4 – Lick Creek Embayment
24
Quarterly Vertical Profiles, 2016-2017
Station OC5 – Mainstem Reservoir at Hwy 44
25
Quarterly Vertical Profiles, 2016-2017
Station OC6 – Mainstem Reservoir at I-20
26
Quarterly Vertical Profiles, 2016-2017
Station OC7 – Apalachee River Embayment
27
Quarterly Vertical Profiles, 2017-2017
Station OC8 – Oconee River Embayment
28
Quarterly Vertical Profiles, 2016-2017
Station OC9 – Sugar Creek Embayment
29
Quarterly Temperature and DO Profiles,2003-2017
• 2016-2017 profiles consistent with longer history of profile data for Lake Oconee
• Vertical stratification occurs during spring in Wallace Dam forebay (OC1)
• By summer, water column warmer and well mixed due to pumpback operations
• Effects of mixing most evident at OC1 and to a lesser extent at other mainstem reservoir stations
OC1
30
Water Chemistry Analyses Indicate Good Overall Water Quality Conditions
• Results similar to first season of study and data from previous years• Higher concentrations of total phosphorus and turbidity at upstream stations
(OC7, OC8, OC9) indicative of nutrient loading from upstream watershed• Mean trophic state index (TSI) values ranging from 47 to 52 indicate continuing
mesotrophic conditions in Lake Oconee TSI for Lake Oconee, 2014-2017
Trophic state refers to the biological productivity of a waterbody related to nutrients; TSI values can range from 0 to 100
TSI Value Trophic Status
< 30 Oligotrophic
30-60 Mesotrophic
>60 Eutrophic
31
Proposed Nutrient Criteria for Lake Oconee
• Nutrient criteria for Lake Oconee would contribute to improvements in water quality and downstream DO levels in the future
• Georgia EPD is proposing site-specific lake standards that include numeric chlorophyll and nutrient criteria for Lake Oconee to reduce nutrient enrichment from human activities and natural sources in the upstream watershed
• Proposed criteria to include:
• Growing-season average chlorophyll-a limits for the Oconee River arm, the Richland Creek arm, and upstream from the Wallace Dam forebay
• Growing-season average limits in the photic zone for total nitrogen and total phosphorus
32
Updated Water Resources Study Summary
• Continuous water quality monitoring in the tailrace exhibited similar overall seasonal patterns in water quality as the first season of study
• Summer tailrace DO depressions below 4.0 mg/L occurred daily during periods in May, June, July, and August 2017 and were correlated with generation
• Pumpback operations and photosynthesis during interim daytime periods corresponded with increases in tailrace DO values, usually to above 4.0 mg/L
• Seasonal vertical water quality profiles in Lake Oconee showed similar trends as the first season of study, including the influence of pumpback operations on maintaining a well-mixed water column in the forebay during summer
• Water chemistry results indicated good overall water quality in Lake Oconee, mesotrophic conditions, and influences from upstream non-point sources
Aeration Methods to Enhance Summer Dissolved Oxygen in the Wallace Dam Tailrace Area
Study Results Meeting
Steve LaymanOctober 17, 2017
2
Study Objectives
• Identify and evaluate, using data collected during the first season of study, technically feasible and cost-effective aeration methods for increasing summer dissolved oxygen (DO) levels in the Wallace Dam tailrace area
• Tailrace monitoring in 2015-2016 found that generation correlated with DO depressions below 4 mg/L during June-early August periods
• Second season of tailrace monitoring in 2016-2017 since detected DO depressions below 4 mg/L during May-August periods
Lake Oconee
Google Earth
OCTR
3
Assessment Approach
Aeration Methods Assessment
• Characterize and model the water withdrawal zone at the turbine intakes
• Screen full range of aeration alternatives for technical feasibility and efficacy
• Model turbine aeration to assess the potential for turbine venting and the addition of forced air
• Model in-lake aeration approaches at the conceptual level of design
Oxygen Diffuser System Site Visit
• Visit two in-lake oxygen diffuser systems operated by the U.S. Army Corps of Engineers (USACE) in large reservoirs on the Savannah River
4
Aeration Methods Assessment
• Performed by a team of highly experienced water quality management specialists:
• Richard J, (Jim) Ruane, M.S., of Reservoir Environmental Management, Inc.
• Mark H. Mobley, P.E., of Mobley Engineering, Inc.
• Paul J. Wolff, Ph.D. of Wolffware, Ltd.
• Experts in water quality, modeling, and aeration; formerly with Tennessee Valley Authority (TVA)
• Assessment report provided as Appendix A
5
Study Area
• Wallace Dam, the lower end of Lake Oconee just upstream of the dam (the forebay), and the Wallace Dam tailrace area downstream to the project boundary at Georgia Highway 16
Project Boundary
Lake Oconee
Tailrace
Forebay
Study Methods
7
Withdrawal Zone Analysis
• Reviewed water quality monitoring data and bathymetry• Applied hourly vertical profile data to develop a withdrawal
zone model using USACE Waterways Experiment Station SELECT model
• Characterize vertical extent of forebay withdrawal zone under different flow scenarios
• Predict DO concentrations in the penstock• DO enhancement target defined as difference between
inflow DO value and numeric DO criteria for the tailrace
• 5.0 mg/L daily average, 4.0 mg/L instantaneous
Station OC1 (Forebay)Hourly Profile Data, 7/27-28/2016
Generation 2p-7pInterim 7p-1amPumpback 1a-7a
8
Screening of Alternative Aeration Methods
• Evaluated range of ten different DO enhancement methods applied at other hydropower projects
• Screened for technical feasibility and efficacy for improving summer DO concentrations in the Wallace Dam tailrace
Source: USDOE
Turbine Venting
Source: Mobley
Forebay Surface Water Pumps
9
Detailed Analysis of Two Most Feasible Aeration Alternatives
Forebay oxygen line diffuser system• Forebay bubble plume model developed to evaluate conceptual design• Withdrawal zone model was used to develop design inputs
Draft tube aeration using compressed air• Discrete Bubble Model set up for Wallace Dam draft tubes• Model calibrated using 2015 and 2016 water quality data• Simulated DO uptake over range of operations and water quality conditions to
determine how much air flow needed to achieve DO improvementsComparative Analysis
• Estimated installation and annual operation costs• Considered practicality of system deployment and maintenance
10
Oxygen Line Diffuser System Site Visit
• Georgia Power visited two oxygen line diffuser systems on the Savannah River
• J. Strom Thurmond Lake
• Richard B. Russell Lake
• Similar in overall design to concept evaluated for Wallace Dam
• Site visit conducted on August 3, 2017, when both systems operating
Richard B. Russell Lake
J. Strom Thurmond Lake
Lake Oconee
Results
12
Summer Vertical Profiles in Forebay
• Prevailing trend during operations:
• Complete vertical mixing of water column during pumpback at night
• Gradual stratification during interim period following pumpback
• Increasing stratification during generation; highest DO values and warmest temperature water near surface
Forebay (OC1) Hourly Profile Data, 7/27-28/201
Generation Pumpback Generation Pumpback
Source: Ruane, Mobley, and Wolff (2017)
13
Generation Withdrawal Zone
• Intake draws generation flows primarily from the upper layers of the forebay, even though the centerline of the intake is 70 feet deep
• As generation flows increase, the withdrawal zone shifts to higher in the water column
Source: Ruane, Mobley, and Wolff (2017)
14
Review of Alternative Aeration Methods (Page 1 of 2)
MethodTechnically Feasible?
Turbine venting – passive venting of air into draft tubes; pressures in draft tube prevent air from being drawn in passively
No
Forebay oxygen line diffuser system – oxygen bubbles passively diffuse into reservoir through porous hose installed in forebay
Yes
Forebay surface water pumps or mixing units – pumps blend high-DO water near surface with low-DO water near withdrawal zone; limited benefit at Wallace Dam because withdrawal zone already draws from upper water column and pumpback operation mixes water column vertically
No
Draft tube aeration using compressed air – adds air to draft tubes using compressors; would allow for acceptable gas transfer efficiency
Yes
Forebay aeration line diffuser system – air diffuses into reservoir through porous hose using compressed air; requires much larger and more costly system than forebay oxygen line diffuser system
No
15
Review of Alternative Aeration Methods (Page 2 of 2)
MethodTechnically Feasible?
Forebay mixing system – mixes water column by upwelling bottom waters into upper layers; mixing induced by pumpback eliminates any benefit of forebay mixing system
No
Forebay skimmer devices – placement of barrier (e.g. submersed weir, curtain) along channel bottom upstream of intake to limit withdrawal zone to high-DO water near surface; withdrawal zone already draws from upper water column
No
Multi-level intake structure – intake allowing selective withdrawal from water levels in reservoir; insufficient to meet DO objectives after pumpback, costly, and unlikely to work with existing pumpback turbines
No
Tailwater aeration structures – aeration weirs or structures that aerate water as it passes and drops in elevation; not feasible due to obstruction of pumpback flows
No
Side-stream supersaturation system – pumps side stream of flow through oxygen transfer device (e.g., Speece Cone), where gaseous oxygen injected and dissolves under high pressure; then flow blended back into waterbody; determined to be too costly in previous hydropower applications
No
16
Forebay Oxygen Line Diffuser System
• Places oxygen in a reservoir in areas of low DO to meet a target DO concentration in the dam releases
• Porous diffuser lines spread oxygen bubbles over large area
• Systems currently being operated at 15 hydropower projects in U.S.
• Applications in the Southeast include 9 TVA reservoirs, 2 USACE reservoirs, and Duke Energy’s Tillery development Source: Ruane, Mobley, and Wolff (2017)
17
Components and Features of Oxygen Line Diffusers
Source: Ruane, Mobley, and Wolff (2017)
18
Conceptual Design of Forebay Oxygen Line Diffuser System for Wallace Dam
• Two sets of diffuser lines about 0.7 mile long for operational flexibility
• Upstream set to inject low level of oxygen continuously to maintain oxygenated forebay volume during non-generation
• Downstream set to boost oxygen output during generation
• Diffuser lines placed at various levels above bottom to optimize aeration of withdrawal zone
• Maximum oxygen capacity of 200 tons/day for worst-case conditions; median use of 60 tons/day
Source: Ruane, Mobley, and Wolff (2017)
19
Cost Analysis of Forebay Oxygen Line Diffuser System at Wallace Dam
Estimated Capital Cost Estimated Annual Liquid Oxygen Costs
$4,699,000 $150,000 to $240,000
• Includes diffuser lines, supply lines, and liquid oxygen storage and supply facility
• Based on tailrace monitoring data for 2015 and 2016
• Up to 8 or 9 tanker trucks would deliver liquid oxygen each week during peak oxygen demand periods
20
Oxygen Line Diffuser System Site Visit to USACE Reservoirs
• On-shore elements of J. Strom Thurmond aeration system:
Liquid Oxygen Tanks and Piping Vaporizer System Oxygen Flow Control Valves
21
Draft Tube Aeration Using Compressed Air
• Active design using compressors/blowers to force air into the draft tube immediately below the turbine units
• Air-water mixture passes through draft tubes prior to being released into the tailrace
• Pressure and time of water passage would allow for acceptable gas transfer efficiency at Wallace Dam
• Potential limitations include loss of unit efficiency from blower operation and excessive TDG in draft tube releases
Draft Tube Tailrace
Forced Air
22
Conceptual Design of Draft Tube Aeration Using Compressed Air
• Discrete Bubble Model used geometry of draft tube to simulate gas transfer through draft tube to the surface of the tailwater
• Model predicted airflows required to achieve DO target of 5 mg/L daily average and resulting TDG levels
• Airflows moderated to reduce energy losses and levels of TDG• Estimated sizes and numbers of compressors required, piping, and electrical work
Source: Ruane, Mobley, and Wolff (2017)
23
TDG Considerations for Draft Tube Aeration Using Compressed Air
• TDG results from air mixing in water; nitrogen (N) accounts for 78% of atmosphere, oxygen 21%; forced air also increases dissolved N in turbine releases
• Turbine releases can become supersaturated with dissolved gas• Background TDG can exceed saturation by 5 to 25% in turbine releases
• Sensitivity analysis bracketing range of dissolved N levels indicated TDG supersaturation could exceed 110% a substantial portion of the time
Source: Ruane, Mobley, and Wolff (2017)
24
Cost of Draft Tube Aeration Using Compressed Air
• In addition to high costs, other potential issues for use of this method at Wallace Dam included elevated levels of TDG, maintenance costs, and noise of the blowers
Estimated Capital Cost Estimated Annual Costs
$15,190,000 $140,000
• Assumes two blowers per turbine• Includes quotes from equipment
manufacturers and sizing based on evaluation of historical DO data
• Does not include piping design and more site-specific information
• Due to losses in net generation
25
Conclusion
• A forebay oxygen line diffuser system is the most technically feasible and cost-effective approach for enhancing summer DO concentrations in the Wallace Dam tailrace
• Benefits of forebay oxygen line diffuser system:• Installation costs $10 million less than draft tube aeration
using compressed air• No modifications to powerhouse or turbines
• No impacts to unit efficiency or operations
• Avoidance of TDG concerns in turbine releases
26
Aeration Methods Study Summary
• Ten aeration approaches were reviewed and evaluated for their technical feasibility and efficacy for enhancing summer DO conditions in the Wallace Dam tailrace
• Conceptual designs were developed and installation costs estimated for two alternatives identified as being technically feasible:
• Forebay oxygen line diffuser system• Draft tube aeration using compressed air
• A site visit of two oxygen line diffuser systems in large reservoirs provided valuable insight into the practicality of system deployment
• The study concluded that a forebay oxygen line diffuser system would be the most technically feasible, cost-effective, and practical approach for enhancing summer DO concentrations in the Wallace Dam tailrace area
ATTACHMENT E STUDY RESULTS MEETING TRANSCRIPTS
TSG Reporting - Worldwide 877-702-9580
Page 1
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2
3
4
5
6
7
8
9
10
11 WALLACE DAM/LAKE OCONEE
12 FERC RELICENSING (P-2413-117)
13 UPDATED STUDY RESULTS AND PRELIMINARY LICENSING
14 PROPOSAL MEETING
15
16 10-17-2017
17
18
19
20 PRESENTERS: Todd Dodd
Dr. Steve Layman
21
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23 REPORTED BY: TANYA L. VERHOVEN-PAGE,
CCR-B-1790
24
25 FILE NO. 132042
TSG Reporting - Worldwide 877-702-9580
Page 2
1 FERC MEETING
2 EATONTON, GEORGIA; TUESDAY, OCTOBER 17, 2017
3 9:38 A.M.
4
5 P R O C E E D I N G S
6
7 MS. O'MARA: Okay. Thank you,
8 Laura. So now we're going to go ahead
9 and move into the updated study results
10 presentations. Our first one up will be
11 water resources and second is aeration
12 method.
13 So I think Tony is going to be our
14 presenter for water resources, and I just
15 realized I had not pulled his up in
16 advance, but I will do it now.
17 So this is Tony Dodd. He's our
18 water resources expert within Georgia
19 Power.
20 MR. DODD: Good morning, again
21 everybody.
22 MS. O'MARA: Good morning.
23 MR. DODD: Again, I'm Tony Dodd
24 here to represent the updated water
25 resources study which was designed as a
TSG Reporting - Worldwide 877-702-9580
Page 3
1 FERC MEETING
2 two-year study.
3 The study objective -- so during
4 the second season monitoring was to
5 characterize the effects of continued
6 projection of operation on water quality
7 in Lake Oconee, and within the projected
8 boundary the first was submitted in
9 September 2016, and last year we
10 presented the results of that study which
11 carried us from July '15 into the end
12 of -- in between September of 2016 last
13 year.
14 The second season or second year of
15 studies really picked up where that one
16 had left off and terminated in the
17 September that we just left behind, and
18 the main study components in the second
19 year study were, again, to continue to
20 look at water quality and tailrace of the
21 dam to monitor that in a continuous way
22 and also to look at the -- to really a
23 continuation of what we were doing for
24 years past with our typical reservoir
25 monitoring program to, again, collect
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2 quarterly reservoir quality data, which
3 actually that second point wasn't
4 actually required in our first approved
5 study plan, but since it's what we
6 normally do anyway, it continued a longer
7 data set and gave us more data for
8 comparison.
9 So each of those years included
10 monitoring in the reservoir as well in
11 the tailrace. The first year included
12 collection of monthly vertical profiles
13 in the lake, otherwise characterizing the
14 water column with certain data parameters
15 and poor water quality chemistry and two
16 intensive summertime studies where we
17 looked hourly on changes and dissolved to
18 try understand the affects of the pump
19 back and the generation cycles on water
20 quality, the water profile upstream of
21 the dam with those operation changes, and
22 then tailrace again.
23 That first year we're looking at in
24 the continuous way dissolved oxygen and
25 water temperature and tailrace, and they
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2 were also intensive surveys there done on
3 top that to look at hourly changes with
4 operations. The second season has a
5 little more focus to what we learned in
6 the second season. The focus continued
7 with the water DO and water temperature
8 and also the vertical profiles of water
9 chemistry on a quarter basis.
10 The lake's classified uses are for
11 recreation, drinking water and fishing,
12 and among those uses there are water
13 quality standards that support those, and
14 one of those standards is in regard to
15 dissolved oxygen.
16 The state standard for dissolved
17 oxygen instantaneous concentration not to
18 fall below 4.0 milligrams per liter or
19 the daily average that's greater than 5.0
20 milligrams per liter, and I mention that
21 here specifically because that's really
22 the focus of our tailrace monitoring
23 results later. So you'll see reference
24 to the 4.0 milligrams liter
25 instantaneous, DO or dissolved oxygen
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2 concentration.
3 As for the study methods, they were
4 really the same in the second year as
5 they were in the first year.
6 In the tailrace shown here in this
7 photographs -- you can see a buoy in the
8 foreground and a dam in the background.
9 We refer to this station as OCPR for
10 Oconee tailrace. The buoy is
11 solar-powered and was able to remotely
12 telemeter or send out data so people
13 could monitor the DO from their desktops
14 many miles away and look at realtime
15 what's happening during the course of the
16 day. The type of equipment we use is
17 YSI. It's sort of a common type of
18 equipment used for lake study, and,
19 again, the data collection was
20 continuously or hourly. That's what we
21 mean by continuous in this case is
22 hourly, and we looked at these several
23 parameters, dissolved oxygen, water
24 temperature, pH, the turbidity and the
25 conductivity, as well, and, of course,
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2 with any equipment -- especially around
3 lakes, they need routine maintenance, and
4 anyone who has done lake work knows their
5 uphill battles with maintenance and
6 equipment, and this was no exception. We
7 did have a few dates where we were able
8 to attach the -- whatever the air logs
9 it, whether it was in the data logger or
10 some physical ailment with the buoy, the
11 realtime telemetry allowed our crews to
12 get out there and fix those things right
13 away and keep it going, and, of course,
14 we've operated that through -- through
15 just September this last month.
16 I'm going to pause on this map just
17 for a second just to set up -- you're
18 going to see a few more graphs like this
19 later, but the goal of collecting data
20 from the tailrace in a continuous way is
21 to not only have the data and look at the
22 concentrations and changes and the actual
23 data for temperature and DO or -- but
24 also to align it, synchronize it with our
25 operations during the same period, but
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2 this is an example graph, probably a
3 snippet of data from the year before,
4 where we show concentrations and trend
5 lines for water temperature in red and
6 dissolved oxygen in blue, and the units
7 of measure for those are on the left-hand
8 axis, and through time, which is on the
9 horizontal axis, those are days of the
10 week, and that's overlaid with our
11 operations, and, again, I'll just pause
12 for our second so you understand at a
13 glance of what this is about later when
14 you see the other graphs. Where the bars
15 are lightly colored, there are smaller
16 increments -- smaller increments within
17 this bit bar set.
18 Each increment represents an hour
19 of operation followed by no bars. Really
20 there's no operation in here. It's a
21 quiet or a quiescent period where there's
22 no generation of pump back, and then the
23 next period is generation in the gray
24 bars, also hourly increments during the
25 time it's generated, and then for the
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2 amplitude or output of the generation or
3 pump back the right hand axis tells us
4 how many units were operated for any
5 given period of time, and then, of
6 course -- and we'll talk about these
7 later what we see on the graphs, but
8 there are certain responses in the trend
9 line to whether we were pumping back or
10 generating or not operating at all.
11 Also, one last feature is where the graph
12 is labeled at a tick mark, that's the
13 beginning of a 24-hour period, and so
14 this would be at midnight and following
15 to noon to the next day and then into the
16 evening of the next night.
17 Turning our attention to the lake
18 water quality monitoring, there were nine
19 stations that were in use throughout Lake
20 Oconee for the water quality monitoring.
21 The table on the left shows how those
22 sampling locations were distributed.
23 Some were in the main stem of the
24 reservoir. Obviously the original
25 reading flow of the waterway, and a
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2 number of those were in tributary
3 embedments, and the idea, of course, is
4 to have something that's representative
5 of the -- through the bathymetric and
6 habitat changes of the reservoir. So we
7 get a good overall picture, and for water
8 quality profiles, it reflected
9 quarterly -- the samples were taken every
10 month, and -- or I'm sorry every
11 location, rather, and then during
12 quarterly water chemistry, there was a
13 subset of those nine locations that were
14 designed still to capture information
15 about main stem locations or tributaries
16 or even like a major confluence so we
17 could detect changes in the water, and or
18 the tenth station was -- I mentioned
19 earlier -- was OCTR, the tailrace
20 location, and I'll point out, too, that
21 the data that we collected in tailrace
22 was collected at 1 meter depth.
23 One meter is where the State
24 standard is measured. So the buoy is
25 collected at about a meter, and also when
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2 the intensive surveys are done hourly
3 from above with a roving piece of
4 equipment in the tailrace, those are also
5 at 1 meter so we could have some basis
6 for comparing the data that we see to the
7 State criteria.
8 For the water quality monitoring of
9 the lake, as I mentioned, the profiles
10 are in all nine locations, and we
11 collected information with this
12 electronic equipment. It's a multi-ray
13 probe. One lowers to depth, and each
14 liter interval from the surface to the
15 bottom we electronically record
16 information for dissolved oxygen, pH, and
17 temperature and conductivity. For water
18 chemistry at that subset location shown
19 here it's really a discreet sample. It's
20 a water collection device that literally
21 grabs an alga, a sample from that depth,
22 and then that's handled in a laboratory
23 way in a chain of and custody and sent to
24 a lab for analysis, and they are analyzed
25 through these 12 parameters. These
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2 twelve parameters are pretty classic in
3 their application from looking at the
4 general health and water quality
5 condition. There are parameters here
6 that speak to chemical nature, physical
7 nature, particularly with turbidity,
8 light penetration and also some
9 biological measures along with nutrients.
10 So I'll jump back now. We're going
11 to talk about the results from the water
12 quality in the tailrace -- from the
13 tailrace monitoring. And I'm going to
14 back up one step more and sort of capture
15 where we left off in the first year,
16 which is really a summary point of what
17 we learned after the first year. All
18 that data that we collected in the first
19 year it demonstrated that we have DO
20 values that sank below that instantaneous
21 4.0 milligrams per liter criteria, and
22 when it occurred, it was limited to these
23 summer months. It's when it's the
24 hottest time of the year, and it's when
25 we expect to see DO depressed, generally
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2 speaking, in surface waters, and we'll
3 talk more about that as we go, but when
4 it occurred, it was in June, July and the
5 early part of August, and in the
6 tailrace, the hourly transects shows the
7 uniform quality throughout the area.
8 What that means is when we were roving
9 with a boat with a piece equipment at a
10 meter deep, while we were generating and
11 collecting information from the dam all
12 the way down to Highway 16, wherever we
13 went, there wasn't much change in the
14 apparent DO or temperature, and then
15 during another period -- maybe during --
16 maybe when we're not pumping back or
17 generating an intensive hourly data
18 collection through that area, even though
19 the DO and temperature might be different
20 during that non-operational period, there
21 was very little change throughout that
22 whole 6,000-foot reach or whatever it is.
23 That's really what that means. And then
24 overall, the big picture take away from
25 that first year, was that when the DO
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2 values decreased in the tailrace with and
3 after generation, they usually would
4 remain lower until daylight hours, and we
5 would see a DO begin to recover, due in
6 part to photosynthesis, and there's a lot
7 of other things that can be in play
8 depending on environmental conditions
9 that day. Maybe it's raining, maybe it's
10 cloudy, maybe there's a wind-driven
11 surface turbulence. Obviously, it's
12 going to the effect DO near the surface.
13 So we see variations, and later, when we
14 look at these graphs where we have bars
15 and peaks and trends, if you see little
16 bumps between the valleys, sometimes it
17 could be explained by those little daily
18 occurrences of changes in the water and
19 the weather conditions.
20 So looking back over the whole
21 two-year period or two and a half year
22 period, really, for monitoring in the
23 tailrace, in 2015 there's a bunch of days
24 of monitoring. 2015 184 days out of that
25 year every day in our 2016 leap year we
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2 were collecting data, and in 2017, 273
3 days which culminated here in the end of
4 September that I mentioned a little while
5 ago.
6 What we learned -- this graph is
7 showing us the relationship between
8 dissolved oxygen in blue and the water
9 temperature in red. And is you see the
10 seasonal variation between those years,
11 and really what this speaks to is what is
12 known about just oxygen solubility in
13 water.
14 When water temperatures are warmer,
15 they hold less temperature. When water
16 temperatures are cooler, they hold more
17 oxygen, and so this is reflecting that
18 seasonal trend throughout the year, and
19 this is what you expect to see looking at
20 water data from any lake or deep pond in
21 our area.
22 We learned from the graph that --
23 in analyzing the data at a closer level,
24 that the winter temperatures were a
25 little bit warmer in 2017 and also the DO
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2 in the summer, this past summer -- the
3 second year -- were also lower than in
4 the first year.
5 So -- and I'll point to another
6 thing, if I may. This is the dissolved
7 oxygen again. Here is the 4-milligram
8 per liter line. You can see during parts
9 of the year where clearly the
10 instantaneous values steep below that,
11 but if you look at the graph, those are
12 usually associated with those -- with
13 those warmer periods, and another way to
14 look at the summary -- summary of the
15 data is that we collect a similar number
16 of readings between both of those years
17 in the tailrace. There were a few days
18 of missing data that we addressed as well
19 as we could with typical range or array
20 of -- maintaining equipment.
21 The average temperature was
22 slightly higher in the second year. The
23 average dissolved oxygen over the entire
24 monitoring periods, each period was the
25 same. The number of hourly readings that
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2 were below that 4.0-milligram per liter
3 were higher in year two than in year one,
4 and then the relative percentage, among
5 all the data points that were recorded,
6 14 percent of those were below four in
7 the second year and 8.6 percent of
8 those -- all those readings were below
9 four in the first year.
10 So here is one of -- one of those
11 graphs that we stopped to talk about a
12 few minutes ago. There's a series of
13 four here, and the scale -- units of the
14 measurements of the scale might change
15 slightly from slide to slide, but it's
16 the same basic information.
17 What I want to show you is where we
18 left. Again, with this graph, this is
19 where we left off at the end of the first
20 year of study, and I'll take you to --
21 from this cooling period in November to a
22 warmer period the following spring to the
23 hottest part of the year in the summer
24 and back up into the fall as our ambient
25 conditions changed, and you'll see the
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2 change in dissolved oxygen and
3 temperature in those line graphs as we go
4 through those four different figures, and
5 we'll also look at some of the trends
6 there.
7 So, at first glance, one could
8 readily see how this is -- early to mid
9 November how just generally depicted by
10 the red line how temperature is starting
11 out in the 22-degree, 23-degree Celsius
12 range and starting cool. This is just
13 the effect of seasonal cooling just of
14 the course of just one week, and DO range
15 during this period of time was 7.4 to
16 8.9 milligrams per liter, and the other
17 thing I think that jumps out right away
18 are these apparent peaks and declines,
19 and you'll notice here -- and you'll see
20 it other graphs, too, everywhere where
21 there's a peak, it's usually in a period
22 where there's no generation or pump back,
23 and then there's a very steep decline in
24 dissolved oxygen typically when
25 generation begins. So what we're seeing
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2 in this graph -- and we'll it in the
3 others -- is the effect of the
4 correlation or generation between -- or
5 generation period and what we see in the
6 water quality. We're just passing water
7 at that time from the dam down passed the
8 tailrace and past this buoy, and we're
9 detecting that.
10 So during a non-generation period,
11 one can actually see where dissolved
12 oxygen actually begins to -- actually
13 begins to recover in -- during the pump
14 back cycle where we turn on the pump back
15 units and pump from St. Claire back into
16 Oconee. The DO is at least stable if not
17 increasing. Remember we're pulling
18 shallower surface waters from St. Claire
19 now back up into Oconee when we're taking
20 that change, but as we're -- when we're
21 finished with that period and we shut off
22 the pump back, it's this quiet phase in
23 the tailrace of Lake St. Claire, and this
24 is during the peak daytime. So during
25 the day we're getting surface warming.
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2 You're getting natural solution and
3 mixing in the surface layers of Lake
4 St. Claire. Whatever is driving the DO
5 here is undoubtedly related to
6 photosynthesis, as well. The alga
7 community makes oxygen and sunlight and
8 it respires oxygen in the acid in some
9 way.
10 So this is a typical -- some of
11 this is sort of overlaying by the typical
12 photosynthesis DO by day and respiration
13 and consuming DO by night, and you'll see
14 that same theme throughout.
15 So, again, November. We move into
16 the spring of the next year. Right away
17 you can see how the DO generally is
18 lower, temperatures are higher, same sort
19 of peaks and valleys. Some of those
20 little bumps that might change daily with
21 weather changes or wind changes. Some of
22 the instantaneous valleys now by May --
23 late May are dipping below that 4.0
24 milligrams per liter criteria, and then
25 in summer, things have really warmed up
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2 now. Now we're up to almost 31 degrees
3 at times during this representative week
4 here in mid August. And the DO is 1.5 to
5 4.9. Of course, the blue line readily
6 conveys how the water we're seeing is
7 coming through the dam generation and
8 it's definitely lower, but the same sort
9 of peaks and trend with some increase in
10 pump back, a lot of increase in DO during
11 the hot and sunny part of the day, and we
12 generate, and we see the water again
13 comes through the dam through the
14 tailrace, and then by September, I guess,
15 we're getting some relief now from the
16 summer temperature effect. Temperatures
17 are now back down between 70 and 90
18 degrees, and the DO is correspondingly
19 now higher as it was in the fall before,
20 and the same things are appearing.
21 So real quickly I thought this was
22 interesting, even though the -- even
23 though -- the scale on these graphs it
24 changes a little bit. You'll get the
25 idea. I'll scroll through these real
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2 quickly, and if you watch the blue line,
3 you can see how it changes from fall to
4 summer and back up. You can see the
5 effect of the season on DO. It gets
6 lower, lower and then by September it
7 starts to recover.
8 As for the quarterly water quality
9 stamping in the lake, we'll capture a
10 little bit of that first season, too,
11 what we learn in the first season before
12 we talk about the second season. The
13 monthly profiles that were collected in
14 told us something about the extent of
15 mixing up in Lake Oconee. In other
16 words, the literal mixing that happens
17 when water is pumped back from St. Claire
18 up to Lake Oconee.
19 Also the forebay and mainstream
20 locations they are weekly stratified in
21 early summer. We'll learn more about
22 that in the next few graphs, and then
23 it's completely mixed by August.
24 The quarterly profiles -- we look
25 at 15 years of Georgia Power profile data
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2 to do a more detailed comparison with,
3 and we can clearly see where there's a
4 lot more just mixing effect from the
5 pumping and moving of water in the main
6 stem locations as compared to an
7 embayment, which doesn't have that kind
8 of connection to the main land or even
9 way upstream in the upper tributaries.
10 In fact, that the upper reservoir
11 stations have their own dynamic. They're
12 shallower. It's more of a constant
13 flowing condition. There are stumps and
14 bridge pilings and things that complicate
15 those upper tributary locations, but they
16 are different than the main stem. They
17 don't have the same mixing effect, and on
18 a quarterly basis there are also
19 chemistry samples demonstrated in the
20 lake. Overall it has a good water
21 quality, and it results in this
22 mesotrophic condition. It's a condition
23 which speaks to the state of productivity
24 in the lake, and we'll touch on that,
25 too, in a few minutes, and the hourly
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2 profiles. These were the more intensive
3 data collection that was made a vertical
4 water column at these locations in the
5 reservoir indicated this temporary
6 stratification during generation and
7 quiet periods when we weren't generating.
8 So stratification means that typically --
9 and you'll see it in a couple of graphs
10 here. Typically in the summer, when the
11 reservoir warms, the warmest waters in
12 the lake buoy to the surface, and the
13 colder -- deeper waters are colder and
14 are more dense, and you'll see a
15 corresponding effect on temperature.
16 Higher temperatures at the top and lower
17 temperatures at the bottom, and also not
18 only temperature but the effects of all
19 the oxygen demanding constituents that
20 are in the lake. Dissolved oxygen shows
21 a similar profile on the stratification
22 in the summer. Higher levels near the
23 surface and lower concentrations near the
24 bottom. That's what that speaks to.
25 We'll move onto the -- a couple
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2 graphs that speak to the second year of
3 study. On the left-hand side, the main
4 graph is -- is depicting a horizontal
5 profile -- quarterly profiles of water
6 temperature with depth on the left-hand
7 axis and temperature across the
8 horizontal axis, and it's corresponding
9 it's counterpart with dissolved oxygen at
10 those same depths at the same time, and
11 right away you can see where the blue
12 line, which is a time period in the
13 spring, when we were out in the
14 springtime recording the information, the
15 lake has this stratified effect that I
16 was just talking about where you have
17 higher temperature, higher concentrations
18 near the surface and at depth, it tends
19 to taper off and with lower concentration
20 and lower temperature, but really
21 interestingly -- and this speaks to the
22 mixing effect that I was just talking
23 about a few minutes ago. The orange line
24 is for mid summer. This is the time of
25 the year when the stratification in a
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2 reservoir that's not influenced by pump
3 back has a much more severe
4 stratification effect. Otherwise normal.
5 So here the gold line or summary is just
6 telling us that the condition at the
7 forebay in front of the dam are just
8 completely mixed from top to bottom.
9 Same temperature, same DO top to bottom.
10 In contrast, if you go to a part of the
11 lake that's not affected by a mixing,
12 pump back mixing. Like here this is in
13 Richland Creek shown on the map off to
14 the side. Same set graph set. You can
15 see here that in spring the
16 stratification begins to set up as we
17 normally expect to see, and by summer
18 it's just even more severely set for the
19 season, and then by fall in the red line,
20 as the lake mixes, surface temperatures
21 cool, the water column mixes, we see
22 really the same DO and temperatures
23 distributed throughout the water column.
24 Again, that's just normal. That's what
25 you expect to see for lakes and lake
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2 flood mixing under the conditions without
3 a pump back influence.
4 So these are some graphs. There
5 are a number of these. I'll go through
6 some of them more quickly because they
7 are very similar, but the ones thing I
8 wanted to point out as we go, the ones in
9 the main stem show more of the mixing
10 effect in the summer, and the ones that
11 are off stream or in the tributaries tend
12 to show more of the stratification
13 effect, and the same thing, too,
14 particularly in the shallow stations
15 here, we'll see near the end of this
16 series of the seven or eight slides, in
17 the shallow stations, those are more
18 readily effected by these daily
19 influences of temperature and rain and
20 whatnot. So -- and usually they are
21 shallower. There's not a lot to see, but
22 we'll go through these pretty quickly.
23 This is station OC-3. This is about five
24 and a half miles upstream to Wallace Dam,
25 and here we can see the stratification
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2 effect particularly with DO. Not so much
3 with temperature.
4 So this is indicating that there's
5 some things, probably the biological and
6 chemical constituents that are affecting
7 the dissolved oxygen in the absence of
8 light near the bottom, and yet the water
9 is a bit mixed because of -- as you can
10 see in the temperatures, and the other
11 thing that's unknown, when we look at
12 these, we'll look for subtle changes or
13 explanations why one profile looks
14 different than the other. I don't know
15 what time of day necessarily that profile
16 was collected. Whether it was near the
17 end of the day versus the middle of the
18 day or in the middle of a quiet period or
19 just at the end of a generation period,
20 it could alter that slightly. But the
21 point is that there's some mixing going
22 on in the main stem. OC-04 that's over
23 in Lick Creek. Also shown off to the
24 west side of the lake on -- in the
25 figure.
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2 It's an embayment so we expect to
3 see a mixing in the stratification in the
4 spring and summer, which we do here.
5 Another main stem location Highway 44.
6 Those who know the lake know the lake
7 really narrows down at that point. When
8 the water is moving, whether it's pump
9 back or flowing, it actually has sort of
10 a physical confining or mixing effect
11 there at Highway 44. So that's probably
12 playing a role in why we see the profiles
13 the way we do here. The same thing.
14 Interesting in spring, the lake is trying
15 to set up and start a stratified
16 condition, but the effects of pump back
17 or normal a pump back operations mix that
18 by summertime. This is another main stem
19 location much further up at the I-20
20 bridge. This is one of those areas
21 that's more dynamic with shallows and
22 in-flows. Another embayment. This is
23 the same stratifying effect. Oconee
24 River at the upper end above I-20 very
25 shallow. Not much to see. Nevertheless
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2 we can still see how it's stratified.
3 Anybody who has been swimming in the lake
4 in the summer, you hot in the hot water
5 and you feel the cold water in your toes.
6 That's what that is. It's colder
7 underneath than it is right at the top.
8 And Sugar Creek also has -- because it's
9 deeper you can see more clearly how it
10 stratifies in the summer -- spring and
11 summer.
12 So this fifteen-year data set that
13 I talked about earlier we included the
14 last two years of quarterly profiles in
15 that longer term data set just to
16 validate what we were seeing the last few
17 years in the way of pump back and mixing
18 and this graph shows that the last two
19 years of study data are -- they are
20 consistent with the longer term
21 characteristics, mixing characteristics
22 of Lake Oconee. Again, the
23 stratification tries to set up the
24 springtime. This is just for -- all
25 these graphs are seasonal depictions of
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2 what's happening just at the location in
3 front of Wallace Dam.
4 Springtime the stratification
5 begins to set up. You see that by mid
6 summer pump back mixing makes the mixes
7 the water column. The warmest
8 temperatures are mixing, and by fall
9 temperatures are going down and dissolved
10 oxygen concentrations are going back up,
11 and it's certainly affected by pump back
12 mixing, but this is also what we expect
13 to see in the fall when the lake changes
14 and mixes naturally.
15 Overall, as I mentioned before, the
16 water chemistry indicated there's good
17 conditions in Lake Oconee. The results
18 were very similar between both years, and
19 really compared to our whole long-term
20 data set there's not much change in water
21 quality in Oconee. It's been relatively
22 good the whole time. The data set does
23 collect the input of nutrients. A little
24 bit elevated nutrients, particularly
25 phosphorous in the upper end of the
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2 reservoir, our main influence. We have
3 had point source discharges. There's a
4 lot of agricultural land uses around
5 Oconee that influence its conditions and
6 its productivity, which, again, is
7 measured -- each productivity is measured
8 as a TSI or a Trophic State Index. A
9 trophic state index is a standardized
10 measure to relay information about
11 productivity of a lake. Typically the --
12 an index is calculated based on
13 concentrations of chlorophyll A or
14 phosphorous or even just water
15 transparency. This means second the
16 water transparency, and the mean of those
17 over time can give you an idea of the
18 trend of condition, at least productivity
19 of the lake.
20 So it falls in this mesotrophic
21 range, but what does that mean? If the
22 lake were to be -- in the extremes, if
23 the lake were to be oligotrophic, it
24 means it's undernourished. Very clear
25 waters, an unproductive fishery, and not
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2 many aquatic plants and on the other end
3 of the extreme if a lake is determined to
4 be eutrophic, it's really getting a lot
5 of nutrients.
6 As a matter of fact, not just a lot
7 of nutrients. Excess nutrients that
8 create undesirable water quality
9 conditions and lead to nuisance growths
10 of aquatic plants often and fishery is --
11 is abundant to say the least, and offers
12 really a lot of challenges in managing a
13 fishery in a eutrophic setting. In the
14 long-term TSI speaks to the aging of
15 lakes, and lakes age over hundreds or
16 thousands of the years, depending on the
17 lake and the TSI gives a point in time
18 about the condition of the lake.
19 So Oconee is good. This is good
20 news for Oconee. It remains in a
21 mesotrophic condition. The nutrients --
22 nutrients and Lake Oconee are of interest
23 to not only us for lake condition but
24 also to our agencies and not just EPD,
25 Georgia EPD but EPA. For years now EPA
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2 has been rolling out an initiative to
3 try -- they recognized that as
4 development and demographics grow
5 nationwide, including in our Georgia
6 lakes, there are more pressures on the
7 lake, more runoff with nutrients,
8 difficulty controlling the discharges
9 that come from, you know, our regulated
10 discharge points, and so to help preserve
11 long-term condition in our nation's water
12 ways, they propose nutrient criteria or
13 limits on the amount of phosphorous that
14 they want to see in our lakes, and
15 Georgia EPD has adopted those -- that
16 same idea and working with EPA to -- to
17 try to regulate nutrients, and so this
18 next slide speaks a little bit to that.
19 Criteria had been developed by EPD,
20 Georgia EPD for Lake Oconee. In fact, we
21 went out here at Rock Eagle just last
22 week where there were talking more about
23 their intended plan to set the nutrient
24 criteria and chlorophyll A limits also
25 for Lake Oconee. And just to put a note
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2 on that, Lake Oconee -- admittedly so,
3 EPD is about five years behind in
4 implementing this plan to set nutrient
5 criteria for Georgia lakes.
6 Oconee is a head of the stack and
7 they are going to continue to do that for
8 all of our Georgia lakes.
9 So that second bullet is about
10 that, and these standards are about
11 limiting nutrient enrichment to help
12 preserve our water quality going forward.
13 The chlorophyll limits are going to be
14 numerical limits for chlorophyll A
15 concentration are proposed, and they'll
16 be measured at three different place in
17 Lake Oconee. EPD has modeled the lake
18 and the inputs, and there are -- it's
19 sensitive enough to detect changes in
20 different parts of our watershed, which
21 is why they are proposing three different
22 monitoring points for chlorophyll A and
23 also for phosphorous, in particular --
24 nitrogen and phosphorus is drivers for
25 nutrient enrichment, they are proposing
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2 numerical limits for those as well. It's
3 a good thing for all of our waterways if
4 we're giving this kind can of attention
5 and -- for all of our lakes, and if you
6 want to learn more about this
7 specifically, you know, contact EPD or
8 our regional EPA, and there's lots of
9 information about what's going on now
10 with nutrient criteria, and real quickly
11 a summary about everything we just
12 covered. The monitoring in the tailrace,
13 the continuous monitoring really had the
14 same patterns the second year that they
15 did the first year. The DO impressions
16 that we saw in the tailrace that were
17 below four occurred during May, June,
18 July and August. So we -- actually, the
19 period in the second year was slightly
20 extended as compared to the first year.
21 The pump back operations and I
22 mentioned photosynthesis we believe is a
23 driver and aids to that recovery of DO
24 after the generation cycles and usually
25 to the concentrations that are above the
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2 criteria in the 4.0 criteria.
3 The seasonal quarter profiles show
4 similar trends, including and sort of
5 highlighting the mixing effect of the
6 pump back operations, especially in the
7 summer, and the water chemistry overall
8 is good and indicating that Lake Oconee's
9 condition is still steady on a weekly
10 trophic range, and it did pick up or
11 detect these -- still look like elevated
12 nutrient levels upstream.
13 And that is my last slide. We're
14 at a point -- with our whole team here,
15 we'd be glad to answer any questions that
16 we can about the water resources
17 presentation. If you have questions,
18 carry those over to lunch or carry them
19 to the afternoon and then just round me
20 up or Courtney and we'll be glad to help
21 answer any questions that may be
22 afterthoughts.
23 So thank you.
24 MS. O'MARA: Okay. Y'all Steve
25 introduced himself a little bit earlier.
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2 He is our consultant who works very
3 closely with us on preparing all our
4 documents and heading up studies and
5 stuff, and he is going to take us through
6 the aeration desktop study that we did,
7 and I'm so excited that they set up
8 because there's coffee in the break.
9 So do you want to take a quick
10 coffee break to get coffee. Why don't we
11 do that. Five minutes.
12 (Brief pause.)
13 MS. O'MARA: This is Steve Layman.
14 He's actually Dr. Steve Layman. He's
15 going to take us through our aeration
16 methods study that we did this past
17 summer.
18 So with that, I'm going to turn it
19 over to Steve.
20 MR. LAYMAN: Thank you. Okay. The
21 title of this study was Aeration Methods
22 to Enhance Summer Dissolved Oxygen in the
23 Wallace Dam Tailrace Area.
24 Georgia Power filed a study plan to
25 investigate aeration methods in February
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2 of 2017, and that was done in response to
3 some comments from the Georgia Department
4 of Natural Resources Wildlife Resources
5 Division, and understanding the results
6 of the first season's study, that was
7 approved by FERC in March of 2017. So
8 this study has been conducted over the
9 course of 2017, and the specific
10 objectives of the study were to identify
11 and evaluate using the data collected
12 during the first year of study
13 technically feasible and cost-effective
14 aeration methods for increasing summer
15 dissolved oxygen or DEO levels in the
16 Wallace Dam tailrace area, and as Tony
17 spoke to you about this morning, the
18 tailrace monitoring in the first season
19 of monitoring in 2015, 2016 found a
20 generation correlated with DO going below
21 4 milligrams per liter, and that pattern
22 was replicated again this past summer
23 with DO following below four for portions
24 between May and August.
25 So the study consisted of an
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2 aeration methods assessment to
3 characterize a model of withdrawal zone
4 at the turbine intake. So the withdrawal
5 zone in Lake Oconee just upstream from
6 Wallace Dam, which we refer to as the
7 forebay. It also screened a flow age
8 variation alternatives for technical
9 feasibility and efficacy or effectiveness
10 to enhance DO. It modeled turbine
11 aeration to assess the potential for
12 turbine venting or the addition of forced
13 air in the turbines themselves, and it
14 also looked at an in-lake approach for
15 enhancing dissolved oxygen, a conceptual
16 level of design.
17 In addition, Georgia Power
18 conducted a site visit this summer to two
19 different in-lake oxygen diffuser systems
20 that are operated by the Corps of
21 Engineers on the Savannah River. So to
22 get a firsthand look at one of these
23 particular methods.
24 The aeration assessment portion of
25 the study was performed by a team of
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2 highly experienced water quality
3 specialist, Jim Ruane from Reservoir
4 Environmental Management, Mark Mobley of
5 Mobley Engineering and Paul Wolff of
6 WolffWare Limited, and all three of these
7 guys worked together and collaborate
8 on -- they collaborated on this project,
9 but they are heavily involved in looking
10 at water quality studies on other
11 reservoirs throughout the eastern and
12 whole United states. They have all
13 formerly worked with Tennessee Valley
14 Authority. Their assessment report --
15 their complete report is provided as an
16 appendix to the report that Georgia Power
17 filed. So I'm going to summarize a lot
18 of what they've done for you today.
19 So the study area, much like the
20 water quality monitoring, consisted of
21 Wallace Dam, the lower end of Lake Oconee
22 just upstream from the Dam are or forebay
23 and the Wallace Dam tailrace going
24 downstream to Georgia 16 Highway bridge.
25 That's the downstream extend of project
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2 boundary within the water of the upper
3 end of Lake St. Claire.
4 So Ruane, Mobley and Wolff used the
5 following methods. First they reviewed
6 the water quality monitoring data from
7 the first season of monitoring in 2015
8 and 2016 for both of the reservoirs and
9 tailrace, and they looked at available
10 bathymetry data for the lake, you know,
11 the bottom contours, the depth, the
12 profile at the bottom, and they found
13 data like these on the right-hand side,
14 which Tony touched on a little bit. They
15 found these particularly useful for
16 characterizing the withdrawal zone of the
17 lake. So this is the profile of
18 dissolved oxygen and depth in the
19 reservoir or vertical profile over a
20 24-hour period. So each line represents
21 a different hour, and during pump back,
22 the green lines, you see a very straight
23 vertical line. That's the forebay
24 becoming well mixed, top to bottom. It's
25 the same dissolved oxygen, and during
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2 generation at the interim period, you see
3 some stratification where you have higher
4 levels of dissolved oxygen at the top
5 than at the bottom, and this kind of data
6 helped them model the withdrawal zone and
7 to predict the DO concentrations that
8 occured in the pen stock at the
9 powerhouse, and pen stock is the pipe
10 that takes water from the lake into the
11 turbines, and so then you would compare
12 the dissolved oxygens predicted in the
13 withdrawal zone with the criteria that
14 applied to the tailrace to define what
15 levels of enhancement you're going to
16 need. So as Tony, mentioned the
17 dissolved oxygen criteria applicable to
18 the tailrace are 5 milligrams per liter
19 on a daily average basis and 4 milligrams
20 per liter instantaneous at all times.
21 They then had took this information
22 understanding the withdrawal zone
23 distribution of the dissolved oxygen, and
24 screened about ten different enhancement
25 methods, aeration methods that are
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2 commonly applied in reservoirs or other
3 hydropower projects and there are two of
4 them up there that are shown up here.
5 We'll talk about some others as we go on,
6 but on the left side the most common
7 approach is turbine venting where you
8 admit air passively into the turbine and
9 it mixes with the water and adds
10 dissolved oxygen and releases downstream,
11 and on the left side, it's basically a
12 cross-section of a turbine with colored
13 areas showing different ways to vent air
14 into a turbine depending on its design
15 and what options might be available.
16 On the right side, another example
17 that uses a different method, is a
18 forebay surface water pump, which would
19 use the propellor -- propellor like
20 device to drive water deeper into the
21 lake. So if there's higher dissolved
22 oxygen water at the surface, you drive it
23 deeper in front of the withdrawal zone of
24 the intake as you get more favorable
25 dissolved oxygen water going through the
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2 turbine. So those are two of the methods
3 they looked at.
4 I'm foreshadowing the results a
5 little bit because they found that two of
6 them were the most feasible and looked at
7 those in much greater detail. One was
8 the forebay oxygen line diffuser system
9 under the forebay upstream to the dam.
10 So that's an in-lake aeration system, and
11 the other was draft tube aeration using
12 compressed air. So it's similar to
13 that -- that last image I showed you, the
14 turbine cross-section, where you could
15 force air into the turbine.
16 So for the forebay oxygen line
17 diffuser system, they did some modeling.
18 They used a forebay bubble plume model
19 that would help them develop a conceptual
20 design, and the withdrawal zone model was
21 used for -- for the inputs to that model.
22 For the draft tube aeration, using
23 compressed air, they used another model
24 called a discreet bubble model that is
25 set up just to model dissolved oxygen
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2 within the turbines, and they used data
3 from 2015 and 2016 monitoring as the
4 input data of dissolved oxygen, and they
5 simulated dissolved oxygen uptake over
6 age operations and water quality
7 conditions to determine how much air flow
8 would be needed to meet a target
9 improvement to meet the DO criteria. And
10 then they compared these two methods in
11 terms of costs, the installation to put
12 in the systems plus the annual cost to
13 operate them, and in addition, Georgia
14 Power considered the practicality of
15 deploying the system and maintaining the
16 type of system, and as part of that, they
17 conducted site visits.
18 So Georgia Power went over and took
19 a close look at in-lake aeration systems
20 used by the Corps of Engineers on the
21 Savannah River, and the two lakes that
22 they looked at systems on were J. Strom
23 Thurmond Lake and Richard B. Russell
24 Lake. They are right in line upstream of
25 Augusta and on the Savannah River, and
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2 you can see Lake Oconee is reasonably
3 close by. So these are also very large
4 reservoir systems, similar physiography,
5 similar climate. The Richard B. Russell
6 Lake also operates in a pump back
7 fashion, and their aeration system is an
8 in-lake forebay system at the dam similar
9 to the design that would be done at
10 Wallace, and Strom Thurmond Lake their
11 aeration system is located about 5 miles
12 upstream of the dam, and it's for a
13 different purpose. It's to place oxygen
14 in a portion of the lake with suitable
15 temperature range for Stripe Bass and to
16 help enhance fishery habitat.
17 The site visit was conducted at
18 the -- in August of this year when both
19 systems were operating, and it was led by
20 the fishery's lead and operations
21 personnel at Richard B. Russell dam. So
22 it was a great opportunity to see the
23 system in operation, ask questions,
24 understand the performance, the
25 maintenance issues and so forth that they
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2 encountered in operating these each
3 summer at both of those lakes.
4 So let's talk about the results.
5 These two plots on the right show similar
6 data as the vertical profiles that I
7 showed you earlier, the hourly vertical
8 profiles just in a slightly different
9 format. The X axis is timed and of --
10 there's a 24-hour event over the course
11 of a day as operation changes from
12 generation to an interim period where
13 there's not doing anything to pump back,
14 and you think it would go back to the
15 interim period generation and so forth.
16 So it picked up a full day of operation
17 in the summer, and on the Y axis, on the
18 side, you have depth in the lake. So
19 it's another way to give you a vertical
20 profile but on an hourly basis. The plot
21 on the left is water temperature, and the
22 plot on the right is dissolved oxygen,
23 and the colors just indicate, you know,
24 temperatures of that same value or a
25 narrow range. So it's showing you all
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2 the reds, the same temperature all the
3 yellow is the same temperature and so
4 forth, and what you see from this is,
5 during pump back, both here and -- both
6 for temperature and DO, it's almost the
7 same color top to bottom, which means
8 it's well mixed top to bottom. During
9 the generation and the interim period,
10 you can see -- you start to see some
11 layering or stratification where your
12 higher dissolved oxygen and warmer
13 temperature are on the top layer, and
14 that gets disrupted and every day, when
15 you get pump back, it gets mixed again.
16 So the prevailing trend -- and Tony
17 touched on this -- is that you get
18 complete vertical mixing of the water
19 model during pump back at night. After
20 that's finished, you start to get some
21 gradual stratification of the water
22 column, and it increases as the
23 generation begins as you start to pull in
24 fresh water from upstream and you have
25 photosynthesis occurring in the daytime.
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2 The DO level goes up on the surface, and
3 why is this important? This is just
4 important to understand where the high
5 dissolved oxygen water is in the water
6 column when you're looking at alternative
7 aeration methods.
8 Their modeling of the withdrawal
9 zone of -- upstream of the dam found that
10 the generation flows primarily come from
11 the upper layer of the forebay, even
12 though the center line of the intake is
13 about 70 feet deep. So what that is
14 trying to say is that most of the water
15 that's drawn in when they generate power,
16 most of it is coming from the upper
17 portion of the water column in the lake.
18 The in-take is fairly deep, but it still
19 pulls a lot from the upper end and -- the
20 upper water column, and the reason that
21 is partly the orientation of the dam
22 itself. The red line is a perpendicular
23 line straight out in front of the dam,
24 and you can see it's pulling water from
25 over on that southwest shoreline of the
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2 lake. So it's pulling from the shallower
3 zone, in general, and then the V-shape
4 bottom of the lake and just the fact that
5 they are pulling so much water that
6 there's way more water in the upper water
7 than below. So that's the -- the trend
8 is they found is the turbines pulled
9 generally from the upper portion of the
10 lake, and, again, that's important in
11 understanding the kind of aeration
12 options available.
13 Okay. So they screened ten
14 different aeration methods, and I'll show
15 you there's five on each screen here.
16 This is just a quick attempt at
17 summarizing some of the considerations
18 that were involved in the screening and
19 in a simple yes/no whether they have
20 decided whether it's technically feasible
21 or not on the scale needed on Wallace
22 Dam. Some of these might be effective on
23 a small scale, but at the scale needed
24 when you're generating power at 20,000
25 plus CFS, at least, you know, that's a
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2 major consideration or major limitation.
3 So the first one, for example,
4 turbine venting, that's the most common
5 approach used in hydroelectric plants
6 across the nation for aerating turbine
7 release, but it's -- they determined it
8 was not feasible because of the pressures
9 in the draft to -- were not negative
10 enough or low enough to create the vacuum
11 needed to pull air passively into the
12 turbines. That wasn't feasible due to
13 the site specific set up of the turbine
14 at Wallace. The second option -- we're
15 going to talk about here in a little more
16 detail the forebay oxygen line diffuser
17 system, and that's a passive system where
18 oxygen bubbles are diffused into the
19 reservoir upstream of the dam, and then
20 that area of the water was discharged
21 during generation to go downstream. That
22 is technically fees able at Wallace.
23 Forebay surface water pumps, those
24 are pumps that would blend high dissolved
25 oxygen water near the surface with water
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2 down lower in the water column, but that
3 did really to benefit Wallace Dam because
4 the withdrawal zone already is pulling
5 from the upper portion of the water
6 column and the pump back keeps everything
7 well-mixed anyway.
8 So this is just some examples of
9 the process they went through in
10 evaluating different options.
11 The fourth one: Draft two
12 variation using the compressed air. It's
13 similar to number one above, turbine
14 venting, but it's forcing the air in and
15 using compressors to force air into
16 the -- into the -- below the turbine into
17 the draft to mass technically feasible.
18 So we're going to look at that in more
19 detail.
20 The bottom one is a forebay
21 aeration line diffuser system which
22 sounds a lot like the second one, the
23 forebay oxygen line diffuser system. The
24 difference is that the oxygen one uses
25 pure liquid oxygen as the source.
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2 The airline diffusers -- aeration
3 line uses air, and air is only comprised
4 of 20 percent oxygen. So you need a lot
5 more air to go into that system, and,
6 furthermore, you have to compress it and
7 force it in. So it's a bigger system,
8 and it costs a lot more money. It's not
9 as feasible. So it was not done. So I'm
10 not going to go through that level with
11 this next page. They kind of went
12 further down in, I think, applicability
13 and potential. Other various mixing
14 systems, forebay, skimmer devices,
15 multi-level intake structures. I'll stop
16 on one more because this comes out. Tail
17 water aeration structure. Why can't you
18 just put aeration down in the tailrace
19 like constructing a weir or some other
20 structure that's going to aerate the
21 waters that it pass it downstream. Well
22 weirs and things like that involve a
23 change in elevation, water falling and
24 getting aerated, and that's not going to
25 work during pump back. You know, as
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2 you've heard, at night, the turbines
3 reverse and the flow is going upstream
4 into the lake, and these -- a lot of
5 these types of measures would obstruct
6 that flow or wouldn't be technically
7 feasible going upstream.
8 Okay. So let's look at the forebay
9 oxygen line diffuser system and what it
10 entails. And so this is a diagram on the
11 right of the -- of a forebay of the lake.
12 I didn't explain this earlier. I thought
13 it looked pretty clear. Here is the dam,
14 here is the lake, the water is going that
15 way downstream. It doesn't show the
16 turbines or the powerhouse.
17 It's just showing simple flow of
18 water. So this one the diffuser line is
19 along the bottom here, and it's placing
20 oxygen down beneath the withdrawal zone
21 and the bubbles move upward in the water
22 column, aerate a large volume of water
23 and then the generation begins. That
24 water is pushed downstream and into the
25 higher dissolved oxygen content.
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2 There are about 15 -- at least 15
3 systems like this currently in use in the
4 United States. Many of them are in the
5 southeast. They were innovated at TVA.
6 They have about nine in use. The Corps
7 has two that we mentioned on the Savannah
8 River, and Duke Power has one at the
9 Tillery development that they just began
10 operating a few years ago in North
11 Carolina. These are some other
12 components of the oxygen line diffuser.
13 This is a close up of the diffuser line
14 on the bottom right here, and we're --
15 really what it just shows you is some of
16 the elements that are involved. You have
17 that yellow tube that's -- it's a
18 buoyancy pipe that you can -- it's filled
19 with air or you can fill it with water,
20 and that's used to raise or sink the line
21 to the bottom of the lake as needed. The
22 black line is an oxygen supply line
23 that's coming from your onshore facility,
24 and on this thinner line, it kind of
25 loops, that's the diffuser line. So the
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2 oxygen goes into that, the porous hose,
3 and doubles out and moves up into the
4 surface, up into the water column above,
5 and you can see that it's tethered to
6 anchors at the bottom of the lake in this
7 case, and they can be elevated any
8 elevation above the bottom of the lake
9 that's desired depending on the modeling,
10 how you can best optimize oxygen transfer
11 into the water column.
12 This is the conceptual design of a
13 forebay oxygen line diffuser system for
14 Wallace Dam, in particular, that Ruane,
15 Mobley and Wolff developed. This design
16 would have two sets of diffuser lines.
17 So you can see the red lines going up the
18 lake would be the porous hose that would
19 be distributing oxygen in a relatively
20 large area, and there would be two sets
21 of them. There's a longer upstream set
22 and a shorter set near the dam.
23 The upstream set would inject a low
24 level of oxygen continuously to maintain
25 a certain critical mass of dissolved
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2 oxygen in the forebay, and then the
3 shorter set of lines just upstream of the
4 dam would be used only during generation
5 to boost the oxygen output right when
6 generation is beginning and the water is
7 going downstream into the tailwater.
8 The maximum oxygen capacity of this
9 system was estimated to be about 200 tons
10 per day of oxygen for the worst case
11 condition. So the worst hottest days of
12 summer when dissolved oxygen drops below
13 four the most that you would need a rate
14 of 200 tons per day, and that doesn't
15 mean much probably for me to say that.
16 It will on the slide when I tell you how
17 often that has to be supplied, but the
18 medium use is about 60 tons per day in
19 the assessment that they did.
20 So here is the cost analysis of the
21 forebay oxygen line diffuser system at
22 Wallace Dam. They estimated a capital
23 cost of about $4.7 million. That
24 includes installing the diffuser lines,
25 the supply lines, liquid oxygen storage
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2 and the supply facility. In addition,
3 the estimated annual cost of liquid
4 oxygen would run from -- based on the
5 modeling they did -- I'm sorry -- based
6 on the water quality monitoring in 2015
7 and 2016 would range from about 150 to
8 $24,000 per year. Up to eight or nine
9 tanker trucks would deliver liquid oxygen
10 each week during the high oxygen demand
11 periods. So that might be just a few
12 weeks each summer, but still during those
13 highest peaks, it would require a
14 constant delivery of oxygen to the
15 system.
16 This is a series of photos from the
17 site visit to the J. Strom Thurmond
18 aeration system to give you an idea of
19 the onshore facilities. You can see the
20 liquid oxygen tanks and piping on the
21 left side, and the vaporizer system. So
22 the oxygen is liquid in the tanks. It's
23 released through the piping system and
24 valves to the vaporizer which uses the
25 atmospheric condition to warm it up and
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2 convert it to gas, and the pressure in
3 that system pushes it into the diffuser
4 lines, and it's regulated by the oxygen
5 flow control valves.
6 This is a biologist's explanation.
7 I'm sure an engineer could do much
8 better.
9 Okay. Let's shift gears and look
10 at the draft tube aeration using
11 compressed air, and what would be
12 involved with it. This is an active
13 design that would use compressors or
14 blowers to force air into the draft tube
15 immediately blowing the turbine unit. So
16 the turbine is sitting there. Use the
17 prime tube that comes out of the
18 tailwater and you can see just kind of
19 the flow of oxygen as it's released
20 through that system.
21 The pressure and the time of water
22 passage would allow for acceptable gas
23 transfer. That was part of their
24 analysis that you could transfer
25 sufficient dissolved oxygen to -- to
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2 achieve the DO targets, but there are
3 potential implications to this system in
4 terms of loss of unit efficiency from the
5 power that's used to operate the blowers
6 and the compressors and excessive total
7 dissolved gases, which we'll refer to as
8 TDG, Total Dissolved Gases. Not just
9 oxygen but nitrogen, and the releases can
10 be a concern, and I'll touch on that in a
11 moment.
12 So their conceptual design for
13 Wallace they modeled it using the
14 discreet bubble model that was based on
15 the geometry of the draft tube and to
16 simulate the gas transfer that would
17 occur through that system. So the model
18 predicted air flows that would be
19 required to achieve dissolved oxygen on a
20 daily average of 5 milligrams per liter,
21 as well as the resulting total dissolved
22 gas levels, TDG levels, and they made
23 assumptions to moderate energy losses and
24 moderate levels of total dissolved gas in
25 their effort, and through this modeling,
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2 they estimated the sizes and numbers of
3 compressors that would be required and
4 the piping and the electrical work, all
5 that's needed to come up with a cost
6 estimate, as well.
7 The plots on the bottom show you
8 the types of output that their model
9 produced. So on the left side, it's days
10 along the bottom. So it's like during
11 the summer how much flow is occurring
12 through the units. Those are the blue
13 vertical lines, and then how much
14 dissolved oxygen is needed to bring it up
15 to the target level, and then that was
16 used to determine how much air flow would
17 be needed through the compressor to
18 achieve that.
19 So the right-hand graph shows the
20 same dates in the summer and then the
21 levels of air flow that would need to be
22 pumped into there to achieve those
23 improvements.
24 They also looked at total dissolved
25 gas, and that's something that has to be
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2 measured in the water which, we didn't
3 have the benefit of having measurements
4 of total dissolved gas in the tailrace.
5 As I mentioned, you know, if you mix air
6 with water with compressed air, you're
7 not only getting dissolved oxygen.
8 You're getting dissolved nitrogen, and
9 maybe small amounts of dissolved methane
10 and other minor components, but you're
11 increasing all the gases and turbine
12 releases can become super saturated with
13 gas, even without thought adding
14 additional air. Apparently below
15 downstream of dams you can have total
16 dissolved gas exceeding the saturation by
17 5 to 25 percent.
18 So this wasn't measured, but they
19 made some assumptions, and they bracketed
20 a range of background total dissolved
21 nitrogen in the water, and then they
22 predicted in the modeling if you add all
23 this compressed air to achieve the DO
24 performance what would the total
25 dissolved gas be in the discharge, and so
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2 there are three scenarios represented
3 here by the blue, red and purple lines
4 and total dissolved gas percent
5 saturation on the left side. This is an
6 exceedance plot. So it says what
7 proportion of the time and certain level
8 of total dissolved gas would be exceeded.
9 So let's say you pick 110 percent
10 saturation, which is starting to get into
11 a level of concern for aquatic bio tay in
12 terms of dissolved gas. So 110 percent
13 at this medium level -- here is
14 110 percent. So about 45 percent of the
15 time in that scenario the total dissolved
16 gas would be above 110 percent
17 saturation. If you went to their most
18 extreme assumption on their bracketed
19 range, it would always be above
20 110 percent in that instance. So while
21 they might have site-specific data and
22 they made some reasonable assumptions, if
23 Georgia Power had selected this method
24 and wanted to move forward, they would
25 probably be advised to study that in more
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2 detail.
3 So here is the cost analysis of
4 draft two variation using compressed air.
5 The estimated capital cost is
6 $15.2 million, and that assumes two
7 blowers per turbine including some quotes
8 from your equipment manufacturers and p
9 sizing based on evaluation of the
10 historical DO data, and there's some
11 elements that it doesn't include like
12 piping design and some of the more site
13 specific information, but it's still
14 substantially higher than the in-lake
15 forebay oxygen line diffuser system. The
16 losses due to generation on annual basis
17 are estimated about $140,000 per year.
18 As I mentioned, the other concerns for
19 compressed -- using the compressed air
20 would be the potential issues with total
21 dissolved gas, noise of the blowers,
22 maintenance and that type of thing.
23 So we're winding down here to the
24 conclusion of the assessment by Ruane,
25 Mobley and Wolff. A forebay oxygen line
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2 diffuser system is the most technically
3 feasible and cost effective approach for
4 enhancing some review of concentrations
5 in the Wallace dam tail trace.
6 The benefits of this system of
7 compressed air would be that the
8 installation costs are $10 million less.
9 There are no obligations to the
10 powerhouse and turbines. There would be
11 no impacts to unit efficiency or
12 operations, and it would avoid total
13 dissolved gas concerns in turbine
14 releases.
15 So, in summary, ten aeration
16 approaches were reviewed and evaluated
17 for there technical feasibility and
18 efficacy for reducing summer DO at
19 Wallace Dam. We looked at conceptual
20 designs and installation costs for a
21 forebay oxygen line diffuser system and
22 draft tube aeration using compressed air.
23 A site visit was conducted, which
24 provided valuable incite into the
25 practical callet of the system deployment
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2 and the study conclude that the forebay
3 oxygen line diffuser system would be the
4 most tangibly feasible and cost-effective
5 and practical approach, and with that,
6 I'll open the floor to questions, and
7 then Courtney and Greg can add?
8 MS. FOSTER: What happens if you
9 don't do anything? I mean, we just saw
10 this presentation that the dissolved
11 oxygen looked good?
12 MR. LAYMAN: Well, if we don't do
13 anything, it would continue to operate
14 the same way it does now, and so you
15 would have summers -- in the summertime
16 you would get the dissolved oxygen
17 dropping below the numeric criteria that
18 the state has as a requirement for
19 achieving water quality standards.
20 So that's the implication -- one
21 implication. A primary one to consider
22 is it still wouldn't be meeting that
23 water quality criteria.
24 Anybody?
25 MS. O'MARA: I realize -- so now
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2 that we've looked at the study results
3 for our second season of studies, I
4 realized -- thank you, Steve -- that I
5 got too gung ho and I skipped over just a
6 few of the slides, and I just have one in
7 particular I want to go back to and it
8 takes us back to where we are in the
9 schedule. So if you can hang on, I'm
10 going to pull up our timeline, and I
11 still think we'll meet our lunchtime.
12 So remember I said we're about
13 three years into this five-year -- we're
14 about three and a half years in.
15 So I just want to -- this is not
16 really an important slide, but -- well,
17 it is because it's FERC's timeline for
18 the integrated licensing process.
19 So the top part is the blue, and
20 that's what we've been doing. We've been
21 meeting. We've been filing reports. So
22 we have two more bubbles that we're
23 hitting. This is -- the red circled one
24 is what we're doing today. We'll file
25 our licensing proposal and then license
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2 application. Those are the two major
3 deadlines, and then all of the green
4 things are what FERC is doing, and there
5 is actually some deadlines for some of
6 our agencies within that green time
7 frame, as well, but what I really just
8 sort of want to take you to was to this
9 next slide to take you back to the main
10 schedule that we have for the overall
11 project.
12 So we filed our progress reports on
13 the second season's studies in -- at the
14 end of August, and then last week we
15 filed, on October 11th, the final study
16 reports, and that's for the second season
17 reports. Remember, we had a first season
18 where we filed final study reports for
19 those at the end of last year. So
20 October 17, that's today. We're here.
21 Your next deadline -- well, actually it's
22 my deadline -- is November 10th. I'm
23 going to file a meeting summary of this
24 meeting. So that's why we have the court
25 reporter. I include the sign-in sheets.
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2 So if you haven't signed your name on the
3 sign-in sheet, please do so when you go
4 to lunch. We'll include who was here.
5 We'll include copies of our slides, and I
6 think we did a separate summary, too,
7 just an overall -- we'll include the
8 agenda, that type of thing. So all of
9 that goes into the FERC record, and you
10 can get any document off of the FERC's
11 electronic library. You just use the
12 project number for Wallace, which is at
13 the top of your agenda. It's P-2413-117.
14 So especially for anybody that
15 wants more detail behind the studies, the
16 studies are already up there on the
17 electronic library. You just need to
18 pull them up. They were filed
19 October 11th. So I'll file the November
20 10th study results meeting summary. Then
21 December 11th is y'all's chance to file
22 something, and it's if you disagree with
23 the meeting or maybe anything that we've
24 said in the summary if you recall it
25 differently, and then January 9th we get
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2 a chance to respond to your comments if
3 there are any, and then in February 8th
4 FERC resolves the disagreements because
5 they are here.
6 So this is one part of the master
7 timeline. There's sort of a parallel
8 path that goes on at the same time for
9 the preliminary licensing proposal, which
10 is what we're doing after lunch.
11 So we'll have a separate table for
12 this that deals with just the preliminary
13 licensing proposal.
14 So after lunch we're going to
15 present to y'all what we are proposing
16 today for this next license. This is
17 what we would send up to FERC, and FERC
18 is going to take everyone's comments and
19 balance, and then we would we get a
20 license at the end of it that is a
21 balance of what everyone wants
22 essentially.
23 So, anyway, this is just the second
24 season study comment timeline. So that's
25 all I wanted to say.
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2 Lunch is supposed to be ready at
3 11:30.
4 Does anyone have any comments or
5 questions about any of this first part?
6 Okay. So I'm going to basically
7 adjourn the updated study results
8 meetings, and then our lunch will be
9 held, if you walk up -- if you go out one
10 of these back doors, which is open, just
11 walk up the steps. The building right
12 behind us is the new cafeteria. You go
13 right in that side door. Go to the
14 right. We have a private room. This is
15 where we've been eating before. Just
16 hang a right once you get in that
17 building.
18 Okay. That's it. Thank you.
19
20 (Thereupon, the meeting was
21 concluded at approximately 11:15 a.m.)
22
23
24
25
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1
2 C E R T I F I C A T E
3
4 STATE OF GEORGIA:
5 FULTON COUNTY:
6
7 I hereby certify that the foregoing
8 deposition was reported, as stated in the
9 caption, and the questions and answers
10 thereto were reduced to written page
11 under my direction, that the preceding
12 pages represent a true and correct
13 transcript of the evidence given by said
14 witness.
15 I further certify that I am not of
16 kin or counsel to the parties in the
17 case, am not in the regular employ of
18 counsel for any of said parties, nor am I
19 in any way financially interested in the
20 result of said case.
21 Dated this 20th day of October,
22 2017.
23
24 _______________________________
Tanya L. Verhoven-Page,
25 Certified Court Reporter,
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