HARTWELL DAM AND LAKE
GEORGIA AND SOUTH CAROLINA

VII HARTWELL WATER CONTROL PLAN



H7-01. General Objectives.

The authorized purposes of the Hartwell project are to provide water supply, hydroelectric power, flood control, fish and wildlife, water quality and recreation benefits. The operation of the Hartwell project will be to maximize the benefits of these authorized purposes. The Savannah District is responsible for ensuring attainment of the maximum public benefits from each of its water resource projects consistent with the objectives and specific provisions of the authorizing legislation and applicable Corps of Engineers' directives for the project.


H7-02 . Overall Plan for Water Control .

Water control management decisions at the Hartwell Project consider hydrologic and climatologic factors, conditions at the downstream projects, potential threats of flood or drought, present and projected lake levels, and the constraints of recreation, wildlife management, water quality, water supply, and hydroelectric power production. Evaluation of these factors requires well qualified technically trained personnel with special experience in the field of modern hydrology, hydraulic engineering, and water control management. The Savannah District maintains this expertise in the Hydraulics Section of the Hydrology and Hydraulics Branch (the Water Control Center) with the assistance of fish and wildlife and recreation experts from the Operations Division. Close coordination with the plant operators, whose experience and on-site location makes them a vital part of the water control team, is essential. The Savannah District reports water control conditions and activities to the South Atlantic Division (SAD) office in Atlanta.

The Hartwell Project includes 35 feet of conservation storage (elevation 625 to 660 feet NGVD, 1,415,500 ac-ft) and 5 feet of flood control storage (elevation 660 to 665 feet NGVD, 293,100 ac-ft). The project has limited flood control storage during the spring and early summer but increases as the project follows the drawdown in accordance with the rule curve. The area capacity curve can be found on Plate H7.3.

a. System Management Decisions concerning water control for the Hartwell Project are part of a coordinated multi-reservoir system regulation for the Savannah River Basin, as well as part of the operation of the larger power network for the southeastern United States (coordinated through SAD).

Additional regulation is provided by several independent hydroelectric projects in the upland area of the basin. Duke Power Company entered into an operating agreement with the Corps of Engineers upon completion of the Keowee-Jocassee Project. The percentage of conservation storage remaining in lakes Keowee and Jocassee was to be kept in balance with the average percentage of storage remaining at the Hartwell and J. Strom Thurmond projects. This agreement was to minimize the impact of the headwater projects on the operation of the existing Corps projects. An outline of the agreement is shown as Exhibit C.

b. Compatibility Among Purposes . The primary uses of the Hartwell Project that would appear to conflict are flood control and hydroelectric power generation. Regulation for flood control minimizes the quantity of water held by the dam in anticipation of keeping the maximum amount of storage available for flood inflows. Regulation for power production maximizes the water quantity and water surface elevation behind the dam to meet power demands which vary daily, weekly, and seasonally. The objective, then, is to provide a maximum power pool (660 ft. NGVD) for hydropower generation while having sufficient storage to handle upstream flood flows. Additional flexibility is provided by the seasonality of flood flows, seasonal, weekly, and daily variations in peaking power demand, integrated basin regulation, and coordinated southeastern power system operations.

Other uses may also compete for water from the Hartwell Project. Potential for conflict exists among the following:

(1) Fish and wildlife or water quality and releases for flood control. During flood control operations, passing inflow through the project may have negative impacts on water quality or fisheries, both within the lake and downstream.

(2) Fish and wildlife or water quality and turbine releases for power (see section H7-11 below).

(3) Recreation and water supply and hydropower. Particularly during drought periods, potential exists for such a conflict. Continued power generation to meet contractual obligations for electrical power when pool elevations may negatively impact recreational users of the lake.

(4) Recreation and flood control. Due to the risk of flood damages and injuries, any necessary flood control regulation is given highest priority.

c. Normal Regulation Activities . Long term planning and supervision of the operation of rainfall and river stage reporting works is a responsibility of the Water Control Center. Weekly reservoir control activities are as follows:

(1) Weekly Water Volume Analysis . The Water Control Manager compiles necessary basic data on precipitation, river stages, reservoir elevations, and general streamflow conditions, and prepares inflow, discharge, storage and pool elevation predictions by noon each Wednesday for the following week and makes water generation availability analysis and forecasts for the three-reservoir system. Projections consider guide curves, power contract commitments, antecedent moisture conditions, expected rainfall, and rainfall-runoff relationships for the upper Savannah River Basin. Additional considerations that might affect discharges are powerplant maintenance activities, proposed operational changes that would affect power generation, and water level management activities related to fisheries or recreation. Input concerning these matters are normally received on Wednesdays from the Planning Division and the Technical Support Branch of Operations Division.

(2) Weekly Report To The South Atlantic Division (SAD) . The Water Control Center transmits the recommended schedule of power generation to the Water Management Branch at SAD by Wednesday afternoon. Following SAD consultation with the Southeastern Power Administration (SEPA), the marketing agency for federally generated power in the southeast, SAD coordinates any changes to the schedule with the Water Control Center.

(3) Weekly Meeting . Each Thursday morning the Water Control Manager conducts a meeting with Operations and Planning Division personnel to review storage and pool elevation projections and power generation availability analyses. The Water Control Manager transmits water control data to SAD.

(4) Final Generation Schedule . Following confirmation by SEPA, SAD advises the Water Control Center each Friday of the amount of energy to be taken from each of the three projects. SEPA's customers (the power companies) furnish hourly schedules directly to the Project Operator with copies furnished to the Water Control Center.


H7-03. Standing Instructions to Project Operator.

A summary of reservoir regulation procedures for the project operator during both normal and emergency situations is found in Exhibit H7-A. Standing instructions are essential to ensure efficient and safe operation of the project at all times: during normal conditions, communication outages, unforeseen and emergency events. These instructions clearly outline the physical operating constraints (spillway or outlet work restrictions) which ensure operation in a safe manner and within design limitations.



The Hydraulics Section, Hydrology and Hydraulics Branch, Engineering Division, is responsible for water control management within the Savannah District, including the regulation of the Hartwell Project to achieve its project purposes. Operations Division is responsible for the operation and maintenance of these projects. Assigning responsibility for water control management to the Hydraulics Section does not diminish the necessity for or the desirability of appropriate and adequate interstaff coordination. Hydraulics Section is responsible for insuring that such coordination has been effected and subsequent actions are taken. The Project Operator is responsible to the Water Control Manager for all water control actions.

Transmission of instructions from the Water Control Manager through several individuals or organizational units can be a source of delay and misunderstandings. Clear lines of communication and authority must be maintained. Occasionally, water control management decisions necessitate that the Water Control Manager (in Engineering Division) contact the Project Operator directly so that satisfactory instructions can be given or hydrologic data can be obtained. Particularly during time of emergencies, there must be no delay in transmission of instructions or hydrologic data between the Project Operator and the Water Control Manager. In these instances, the Project Operator will act on instructions received directly from the Water Control Manager on all matters regarding the regulation of water. Advisory notification is furnished to Operations Division as soon as possible.


H7-04 . Flood Control .

a. General Regulation . Normal conditions exist when there is no flood, drought or other emergency and none are anticipated. The Hartwell Project includes 5 feet of flood control storage (elevation 660 to 665 feet NGVD, 293,100 acre-feet). A seasonally varying guide curve, shown on Plate H7.8, from elevation 656 to 660 feet, NGVD, provides additional flood control during the winter and early spring.

b. Flood Regulation . The Water Control Manager performs flood routings and makes lake elevation and river stage forecasts, and coordinates and schedules lake releases during flood periods. Flood forecasting is accomplished using the Hydrologic Engineering Center (HEC) computer software HEC-1F, a rainfall model that uses real-time precipitation data to estimate inflows at the projects. HEC-5, an HEC model that simulates and analyzes the operation of reservoir systems, is a highly complex multi-purpose, multiple reservoir system simulation tool. The model is capable of evaluating a reservoir system to determine the best operation for water quantity and quality, evaluating operational concerns such as flood control, hydropower and water supply. Mod-5 is an interactive version of HEC-5, and will enable the Water Control Manager to model various release scenarios to best manage the projects.

During floods, the Water Control Manager forwards reports as necessary to SAD containing data on predicted peak stages and percentage of flood control storage utilized. The Water Control Manager informs responsible District personnel on critical weather and streamflow conditions affecting the public and District activities and coordinates with the Public Affairs Office to issue flood reports on flood emergencies. The Operations Division Readiness Branch (OP-E) coordinates implementation of evacuation plans with local government agencies in advance of any flood release, and dispatches flood survey teams to affected areas and notifies local officials that District facilities and personnel are available upon request to assist in emergency conditions.

When the possibility of flooding conditions at or downstream of the reservoirs exists, the Readiness Branch (OP-E) is contacted. The Water Control Manager furnishes a forecast of pool elevations and releases to be made to meet flood control requirements to the Water Management Branch, SAD. At least one of the following SAD personnel will be contacted at any time during a flood emergency:

Mr. Chris Smith Office N/A
Mr. Trent Ferguson Office N/A

After reviewing these directives, the Hydraulics Section advises SEPA of releases to be made, and then advises the Water Control Management Branch, SAD of arrangements made with SEPA. The Water Control Manager advises the Project Operator of the releases required by spillway gate operation. An advisory notification is then sent to Operations Division. The Water Control Manager will notify Operations Division and SAD of the arrangements made at the first opportunity during normal working hours.

Reservoir operation is dependent upon the various combinations of reservoir stages and runoff, and requires a flexible method of operation. Coordination with the Keowee-Toxaway Project of Duke Power Company, as well as Thurmond and Russell, is required for maximum protection of the Augusta damage center and downstream areas. Flood control storage at the Georgia Power Projects at the headwaters of the Savannah River is negligible, although they may provide useful inflow on during periods of deficit streamflow. All instructions pertaining to reservoir regulation for flood control are to come from the Savannah District. See Table 5-3 for a listing of Savannah District flood control personnel and their phone numbers.

c. Gate Operation . The Hartwell Lake Flood Control Release Schedule is found in Plate H7.4. When Hartwell Lake exceeds its flood control storage, use of the tainter gates according to the Spillway Gate Regulation Schedule (Plate H7.5) is required. All discharges other than through the turbines should be made through the spillway gates. When all spillway gates are to be opened, discharges should be made uniformly across the spillway, as nearly as practicable, by opening gates so that no gate opening is more than one foot larger or smaller than any other gate opening . Gates should be opened beginning near the center of the spillway (#6 and #7) and proceeding outward. When closing the gates, the order is reversed, with #1 and #12 closed first, and proceeding toward the center of the spillway. As during raising, the gates should be closed so that no gate opening is more than one foot larger or smaller than any other gate opening. The spillway gates are numbered 1 through 12 beginning with the gate nearest the (ft NGVD).


H7-05 . Recreation .

The impact of lake levels upon visitation is largely dependent upon the season of the year in which they occur and the duration of lower lake levels. The Hartwell Project's design fluctuation (drawdown) is 35 feet, between elevations 625 and 660 feet NGVD. The 35-foot drawdown causes severe impacts to recreation activities in and around the lake. Therefore, implementation of the Savannah River Basin Drought Plan is triggered by low lake levels that require reduced outflows in an attempt to lessen the rate of decline.


H7-06 . Water Quality .

The Clean Water Act established a national objective to restore and maintain the chemical, physical and biological integrity of the Nation's waters. The thrust of this objective is to protect all existing and future uses, including assimilative capacity, aquatic life and other water quality aspects, as well as related uses, such as municipal and industrial water supply, recreation and hydropower. Our National policy is that the Federal Government (in design, construction, management, operation and maintenance of facilities) provides leadership in the nationwide effort to protect and enhance the quality of air, water and land resources and complies with all Federal, state, interstate and local requirements in the same manner and extent as non-Federal entities. Accordingly, the following general water quality management objectives apply to all South Atlantic Division lake projects:

Ensure that water quality, as affected by the project and its operation, is suitable for project purposes, existing water uses, and public health and safety.

Define baseline water quality conditions for each project. This effort consists of a pre-project water quality evaluation, and a description of the post-construction water quality characteristics developed at the earliest time that data collection and evaluation are practical.

Establish and maintain a water quality monitoring and data evaluation program adequate to achieve water quality management objectives and demonstrate project performance.

Ensure that, to the extent practicable, water quality conditions associated with the project are in full compliance with applicable water quality standards.

Like all deep lakes in the Southeastern United States, Hartwell Lake stratifies during the summer months. A thermocline (temperature-density gradient in a layer called the metalimnion) is established during the summer months as the top waters (epilimnion) warm quicker than those at the bottom (hypolimnion). The thermocline essentially blocks circulation between the layers (which is normally provided by wind induced currents) from providing oxygen from the atmosphere and top waters to the bottom waters. Continued deposition of oxygen-demanding substances deplete the dissolved oxygen within the bottom waters, particularly at the mud - water interface. During hydropower generation in the summer, the waters discharged through the Hartwell Dam are drawn from the hypolimnion. As the summer progresses, the quality of these waters (dissolved oxygen content) degrades until "turnover," that is, the recirculation of the waters in the fall, when the surface water has cooled to the temperature of the bottom waters, eliminating the temperature/density gradient, and the layers mix.


H7-07 . Fish and Wildlife .

The Savannah District conducts the following Water Control Management for Fish Management Purposes:

a. Fish Spawning . Water control management for fish management purposes is conducted in accordance with SAD Regulation 1130-2-16 (Exhibit B). At the earliest possible date, Operations Division notifies the Water Control Manager of their estimate of the beginning and ending of the largemouth bass spawning period. During the spawning period, the Water Control Manager schedules releases (to the maximum extent possible without jeopardizing other project purposes) so that the downward fluctuation or lowering of the lake level will not exceed 6 inches from the maximum elevation reached during the spawning period. Should it appear that maintaining lake level fluctuations within the six inch limit will not be possible, the SAD Water Control Management Branch and the Project Manager are notified by the Water Control Manager as far in advance as possible.

b. Fish Entrainment . The Savannah District restricts discharges at the Hartwell Project when there is a threat of killing significant numbers of fish. Fish kills at the Hartwell Project have involved the blueback herring. The Savannah District consequently developed the Plan of Action to Prevent or Minimize Blueback Herring Entrainment at Hartwell Dam. (refer to Exhibit H7-C of this plan). The likelihood of a fish kill is determined by the Operations Division Fisheries Biologist at the project. Operations Division has a seasonal monitoring program conducted by the Waterways Experiment Station (WES) within the lakes to detect potential fish kills. Should a fish kill occur, notification of personnel will follow the procedures of the current Plan of Action to Prevent or Minimize Blueback Herring Entrainment. Power system emergencies which threaten interruption of power and/or brownouts override this policy.


H7-08 . Water Supply .

Although not a specifically authorized project purpose, water supply is an important consideration in the water control management of the upper Savannah River Basin. There are approximately 73 water users that obtain all or a portion of their municipal or industrial water supply from the Savannah River or from Hartwell, Russell and Thurmond Lakes. The Water Control Manager notifies water users of any impending interruption in their water supplies due to modified project releases, and forwards periodic reports to SAD during droughts showing projected reservoir stages including a "worst case" hydrologic condition.

HEC-5 is the computer model which we have chosen to predict pool fluctuations. This model takes into account predicted inflows, and hydropower demands, as well as various operating restrictions which are imposed during drought periods.


H7-09 . Hydroelectric Power .

All power produced at Federal projects (except the Tennessee Valley Authority and St. Stephens) in the states of Georgia, South Carolina, North Carolina, Virginia, Florida, Kentucky, Tennessee, West Virginia, and Alabama is marketed by the Southeastern Power Administration (SEPA). SEPA combines the three Savannah District projects with seven Mobile District projects (in the Alabama-Coosa and Apalachicola-Chattahoochee-Flint Basins) to form the Georgia-Alabama-South Carolina System. Hydropower may be supplied by any combination of projects within the ten plant system. Under normal circumstances, if one basin or portion of a basin is unable to meet the power production expected, that shortage can be transferred to, or "made up" in, another basin. SEPA markets the power through contracts negotiated with certain preferential customers for the delivery of energy and the ability to meet peaking demands.

The currently installed capacity of the Hartwell Project is four 66,000 kilowatt conventional generator units (numbered one through four), and one 84,000 kilowatt conventional generator (number five) for a total of 348 megawatts.

H7-10 . Navigation .

The authorizations for both the upstream Hartwell Project and downstream Thurmond Project include navigation on the lower Savannah River (downstream of the Thurmond Project). Lack of waterborne commerce on the Savannah River Below Augusta Navigation Project has fallen in recent decades to near zero and that navigation project is inactive. Consequently, there is no current operation of the three projects for navigation. Presently, the minimum flow requirement of 5800 cfs which was authorized at the Thurmond Project for navigation on the lower Savannah River has been succeeded by minimum Thurmond discharges which are based on the needs of downstream water supply withdrawals. However, should navigation become active again, Thurmond discharges, and accordingly Russell and Hartwell discharges, may be regulated to provide suitable navigation depths.


H7-11 . Major Constraints .

Constraints are conditions that arise subsequent to project design that prevents (or is allowed to prevent) the achievement of a water control objective. Such constraints may include physical, legal, political, and social factors as well as conflicts between purposes.

At present, the major constraint effecting the Hartwell Project is the seasonal fishkill of the blueback herring. In response to this occurrence the Savannah District has developed and implemented a plan of action to prevent or minimize the entrainment of the Blueback Herring (refer to Exhibit H7-C of this Water Management Plan).

Another constraint is the location of houses within the flood control pool. Presently there are several structures which experience flooding as Hartwell's pool level approaches 665 ft. NGVD. Efforts will be made to avoid flooding the residents of Hartwell Lake who live within the flood control pool but under the threat of a severe flood these structures would be impacted, as the safety and integrity of the dam takes precedence.


H7-12 . Deviation From Normal Regulation .

a. Emergency Regulation . Occasionally, a need may arise to temporarily modify the water releases from a project. Examples of these needs are for search and rescue or to control a downstream pollutant spill.

In the execution of the water control plan, appropriate attention is given to project safety to insure that the project is operated for the safety of its users and the general public. Care is exercised in the scheduling of reservoir releases to assure that controlled releases minimize project impacts and do not jeopardize the safety of persons engaged in activities downstream of the dam. These provisions require the issuance of adequate warnings or otherwise alerting all affected interests to possible hazards from project activities.

Should a person fall into the tailrace or intake section of the project or come into contact with an energized conductor within or feeding from the project, the powerplant operator or nearest responsible employee takes emergency actions in accordance with established procedures. The District Engineer is occasionally requested to deviate from normal regulation of the project. Deviation requests usually fall into the following categories:

Emergencies that can be expected to occur at some time are: accidents, including drowning, and failure of operation facilities. Necessary action under emergency conditions is taken immediately unless such action would create equal or worse conditions. The SAD Office is notified as soon as is practicable. A written confirmation showing the deviation and conditions will be furnished to SAD.

b. Unplanned Minor Variations . Unplanned variations may occur for non-emergencies, normally for construction for utilities or bridges, for a period of a few days or hours.

c. Planned deviations . An analysis of conditions, alternatives, expected benefits, probable effects will be coordinated with SAD by telephone, fax or E-mail. Examples of planned deviations could be to prevent fish entrainment, or for drought contingencies. A copy of the drought contingency plan is included as Exhibit M, while the drought plan action levels are shown on Plate H7.10.EXHIBIT H7-A



STANDING INSTRUCTIONS TO THE PROJECT OPERATOR
FOR WATER CONTROL

HARTWELL DAM AND LAKE PROJECT



  1. BACKGROUND AND RESPONSIBILITIES

a. General Information . These "Standing Instructions to the Project Operator for Water Control" are written in compliance with Paragraph 9-2 of Engineering Manual 1110-2-3600 (Engineering and Design, MANAGEMENT OF WATER CONTROL SYSTEMS, 30 November 1987) and with Engineer Regulation 1110-2-240 (Engineering and Design, WATER CONTROL MANAGEMENT, 8 October 1982).

(1) Project Purposes . The Hartwell Project is operated for Hydropower, Recreation, Fish and Wildlife, Flood Control, Water Supply and Water Quality .

(2) Chain of Command . The Project Operator is responsible to the Water Control Manager for all water control actions.

(3) Structure . The Hartwell Dam is located at Savannah River Mile 288.9, Hartwell County, Georgia. The dam is a concrete gravity and earth embankment structure with a concrete gravity ogee spillway. The Hartwell (ft NGVD) is located on the Georgia (west) side, immediately downstream of the dam.

(4) Operations and Maintenance (O&M). All O&M activities are the responsibility of the U.S. Army Corps of Engineers.

b. Role of the Project Operator .

(1) Normal Conditions (dependent on day-to-day situation ). During normal conditions, all releases will be made through the turbine units. The water control manager will coordinate the weekly water control actions with SEPA. The Project Operator will then receive instructions from SEPA. This communication will be increased to a daily basis if the need develops.

(2) Emergency Conditions (flood or drought) . The Project Operator will be instructed by water control managers on a daily or hourly basis for water control actions during flood events and other emergency conditions. In the event that communications with water control managers are cut off during a flood event, the operator should regulate plant discharge in accordance with Plate H7.4, Flood Control Release Schedule, Plate H7.5, Spillway Gate Regulation Schedule, and Plate H7.6, Tainter Gate Rating Curves.


  1. DATA COLLECTION AND REPORTING .


a. Normal Conditions . Project data is recorded hourly by the project operator. The data is retrieved hourly by the Water Control Manager and loaded into the Water Control Data System. The data is subsequently made available on the Water Management web site at http://water.sas.usace.army.mil:

(1) Pool Elevations in feet NGVD are collected hourly.

(2) Basin Average Precipitation in hundredths of an inch is estimated hourly from NWS doppler radar.

(3) Tailwater Elevations in feet NGVD are collected hourly.

(4) Discharge in cubic feet per second is collected hourly.

(5) Inflow to the lake in cubic feet per second is collected hourly.

(6) Scheduled and Actual Generation in megawatt-hours is collected hourly.

b. Emergency Conditions . Report hourly the elevation, turbine discharge, spillway discharge, and general project status to the Water Control Manager.

c. Regional Hydro-meteorological Conditions . The Project Operator will be informed by the Water Control Manager of regional hydrometeorological conditions that may impact the structure.

  1. WATER CONTROL ACTION AND REPORTING .

a. Normal Conditions . The Project Operator reports directly to the Water Control Manager.

b. Emergency Conditions . The Project Operator will follow the Savannah River Emergency Action Plan (District Pamphlet 1130-2-16, Appendix B) for emergency notification procedures.

c. Inquiries . All significant inquiries received by the Project Operator from citizens, constituents or interest groups regarding water control procedures or actions must be referred directly to the Water Control Manager.

d. Water Control Problems . The Project Operator must immediately notify the Water Control Manager, by the most rapid means available, in the event that an operational malfunction, erosion or other incident occurs that could impact project integrity in general, or water control capability in particular. Such incidents are discussed in Appendix A of DP 1130-2-16, the Emergency Action Plan.
EXHIBIT H7-B

PERTINENT DATA
HARTWELL DAM AND LAKE



LOCATION
In the Piedmont Physiographic Province at Latitude 34 o 21' north, Longitude 82o 48' west
On the Savannah River:
288.9 miles above the mouth
274.5 miles above Savannah, Georgia
89.3 miles above Augusta, Georgia
67.3 miles above Thurmond Dam
29.8 miles above Russell Dam
In Hart County, Georgia 7 miles east of Hartwell, Georgia 2300 feet upstream of U.S. Highway 29
DRAINAGE AREA percentage square miles
Above the mouth of the Savannah River 100 10,579
Above Augusta, Georgia (Butler Cr. gage) 71 7,508
Above J. Strom Thurmond Dam 58 6,144
Above Richard B. Russell Dam 27 2,890
Above Hartwell Dam 20 2,088
Basin between Russell Dam and Hartwell Dam 8 802
STORAGE VOLUMES Elevation (ft NGVD) Acre-feet
Spillway design flood 674.0 3,430,000
Standard project flood 667.9 3,020,000
Flood control pool 665.0 2,842,700
Maximum conservation pool 660.0 2,550,000
Minimum conservation pool 625.0 1,134,100
Conservation storage, usable 625 to 660 1,416,000
Flood storage 660 to 665 293,000
Surcharge storage 665 to 674 596,000
POWERPLANT ELEVATIONS Elevation (ft NGVD) 
Switchyard 513 
Distributor 484 
Bottom of draft tube 442 
RESERVOIR AREAS Elevation(ft NGVD) Acres
Spillway design flood (Max Surcharge Pool) 674.0 71,300
Standard project flood 667.9 64,800
Flood control pool 665.0 61,400
Maximum conservation pool 660.0 55,950
Minimum conservation pool 625.0 27,650
Limits of clearing 630 to 661 26,600
below 630 Partial clearing
DAM, SPILLWAY, INTAKE AND POOL ELEVATIONS Feet NGVD 
Top of dam 679.0 
Maximum Observed Pool 665.404/8/1964
Minimum Observed Pool 637.49 12/10/2008
Spillway design flood 674.0
Induced surcharge pool 674.0
Standard project flood 667.9
Top of tainter gates, closed 665.0
Flood control pool 665.0
Maximum conservation pool 660.0
Average conservation pool 652.0
Minimum conservation pool 625.0
Spillway crest 630.0
Intake invert for Hydropower 500.0
Spillway bucket lip 517.0
Elevation, bottom of sluice 500.0
Draft tube exit 442.0
DAM, SPILLWAY AND INTAKE DIMENSIONS
Concrete gravity and earth embankment with concrete gravity ogee spillway
Length of concrete sections 1900 feet 
Length of earth embankment 15,952 feet 
Maximum height of concrete section 204 feet 
Maximum height of earth embankment 106 feet 
Length of intake section 340 feet 
Number of sluices 2 
Width of sluices 5.67 feet 
Height of sluices 10 feet 
Gross length of spillway 568 feet 
Length of clear opening 568 feet 
Tainter gates (12) each 40 feet wide by 35.5 feet high 
Flip bucket 20 degrees 
Radius of bucket 40 feet 
TAILWATER ELEVATIONS Feet NGVD 
Spillway design flood 519.3565,000 cfs
Standard project flood 512.0420,000 cfs
(ft NGVD) Design flood 510.0380,000 cfs
Maximum pool of record 491.6 
Four units operating at average head 481.6 
Maximum static condition 482.6 
Streambed 475.0 
DESIGN FLOWS   Cubic feet per second
Spillway Design Flood Peak Reservoir Inflow 875,000 cfs
  Maximum Estimated Outflow 565,000 cfs
Standard Project Flood (SPF) Peak Reservoir Inflow 435,000 cfs
  Maximum Estimated Outflow 325,000 cfs
POWERPLANT EQUIPMENT
Initial units four conventional 
Supplimental Units one conventional 
Maximum net operating head 192 feet 
Average operating head 171 feet 
Minimum operation head 142 feet 
Turbine capacity at average head 91,500 hp per unit 
Maximum discharge at minimum head 6500 cfs per unit 
Length of draft tube 66 feet 
GENERATORS
Initial installation - four conventional units each at 66 MW initial 85 MW current
Supplemental installation - one conventional unit at 84 MW initial 90 MW current
Total installation 426 MW 
Average annual energy 457,342,000 kilowatt-hours 
Generator rating 90% pf, units 1-4; 95% pf, unit 5 66,000 kva
Generator speed 100 rpm 
Generator voltage 13.8 kV 
Transformer rating two 3-phase 56.6 mva
Transformer voltages, kV 13.2 to 230 
SWITCHYARD
Location west (Georgia) bank, downstream
Initial number of transformer bays 2 
Ultimate number of transformer bays 3 
Line positions 4 
Equipment voltage 230 kV