Tennessee Valley Authority
Bradley and Hamilton Counties, Tennessee
Power System Upgrades
TVA has announced a preferred site for the proposed 500-kV substation in southeast Tennessee, as described below.
Preferred site
TVA evaluated four alternative sites for the substation, studying environmental and land use impacts and engineering and relative cost considerations. The evaluations were based on available data, aerial photography and limited onsite reviews, and public comments. Based on these evaluations, TVA has identified Site 1 and the associated 500-kV and 161-kV line arrangements as the preferred location for the new 500-kV substation.
View map of the preferred site (PDF, 243 kb).
Site 1 appears to minimize the overall environmental impacts to streams and aquatic resources, wetland areas, and sensitive species. In addition, the site would require less total land area for development of the substation and associated lines, resulting in less overall land use and environmental impact. It would affect fewer property owners, allow easy access, and apprears to be less expensive to develop. TVA will complete a detailed environmental review of the project and document a final decision as required by the National Environmental Policy Act (NEPA).
Purpose and benefits of proposed system upgrades
An increase in generation and growing power demands in the Chattanooga area could create reliability issues in TVA’s southeastern service area unless improvements are made to the transmission system in Bradley and Hamilton counties before 2007. These improvements include the proposed construction of a 500-kV substation in western Bradley County, Tennessee.
To help serve power demands in the region, which are growing 2 to 4 percent annually, TVA will increase generation output from Raccoon Mountain Pumped Storage facility by approximately 290 megawatts. (View map for electricity load growth per year, 1997 - 2001 for the TVA service area).
Increases in generation capacity, whether they result from TVA projects or another company’s use of the TVA transmission system, typically require upgrades of various parts of the system. Detailed analyses by TVA show where and under what circumstances the transmission system would not operate properly or not be able to maintain the stability of generating plants in the Chattanooga area.
Based on these assessments, TVA has determined that a variety of improvements to the transmission system are needed before 2007 in Bradley and Hamilton counties to ensure continued reliability in TVA’s southeastern service region. If the upgrades are not made, the existing transmission system may become overloaded or stability problems could cause damage to generating facilities in the Chattanooga area, as well as possible brownouts or power interruptions in the area, which are costly and inconvenient.
A significant amount of the construction and modification work associated with this transmission improvement project will take place at existing TVA facilities. (View map of region showing locations of project activities). The project also includes the proposed construction of a 500-kV substation near the border of Bradley and Hamilton counties.
The project also will involve the rebuilding of up to five miles of transmission line as a double-circuit line to connect Chattanooga EPB directly into the new substation and the stringing of about 6.6 miles of new line on the vacant side of a 161-kV line that is currently in service. The additional transmission line will help ensure a strong voltage source for the area and reliable power for consumers.
Major project activities
The transmission system improvement project includes the following proposed activities.
Construct new 500-kV substation
TVA is proposing the construction of a substation that will require a 50- to 60-acre site in western Bradley County near Apison, Tennessee. Four possible sites for the proposed substation have been identified. These are located primarily on property in Bradley County, with one site overlapping into Hamilton County. These sites are near the intersection of the Sequoyah-Conasauga 500-kV transmission line and the Concord-Sugar Grove 161 kV transmission line. (View map of region showing locations of project activities).
Constructing a substation at this location would allow these existing lines to connect directly to the new substation. The 500-kV lines will be built on single-circuit towers, and the total right-of-way width for the two parallel 500-kV lines will be 300 feet. This helps minimize new line right-of-way requirements and impacts to property owners and the environment.
A microwave tower will be required at the substation to monitor and control its operation. The height of the microwave tower will be determined after a site for the proposed substation has been selected. The tower will be lighted, as required by the Federal Aviation Administration. If the tower is over 200 feet, the FAA requires dual beacon and marker lights, which will be a white strobe during the day and red lights at night. If the tower is under 200 feet, an evaluation by TVA or the FAA will be needed to determine appropriate lighting for the tower.
Reconfigure the Raccoon Mountain switchyard
This reconfiguration will isolate two generators to the 500-kV bulk power transmission system to lessen load on the 161-kV system and prevent overloading of the system and potential equipment damage.
Connect a 161-kV line to the new substation
To ensure a strong voltage source for the area and to facilitate the even flow of power from TVA generating facilities to area substations, TVA will connect a transmission line, which now goes to Chattanooga EPB’s Apison Substation from TVA’s Concord-Sugar Grove transmission line, directly to the new 500-kV substation. This will require rebuilding approximately five miles of the existing Concord-Sugar Grove transmission line to hold two 161-kV lines.
Add six miles of 161-kV transmission line
A transmission line will be strung as a second line on a vacant side of TVA’s Sequoyah-Concord 161-kV line to create a new circuit between the Concord and Apison substations. This will help ensure a strong voltage source for the area and facilitate the even flow of power from TVA generating facilities to area substations.
Add 161-kV capacitor banks
For additional voltage support, two 161-kV capacitor banks will be added to each of the following TVA substations: Moccasin Substation (Chattanooga), Concord Substation (Chattanooga), and East Cleveland Substation (Cleveland).
Replace circuit breakers
Three 161-kV circuit breakers will be replaced at the East Cleveland Substation to prevent overstressing of the breakers and help ensure the proper operation of equipment.
Add relay protection
Relay protection changes will be made in TVA’s Sequoyah and Chickamauga Hydro switching stations to improve power system stability.
Rearrange the Concord Substation.
This facility will be rearranged to accept the new circuit to the Apison Substation and improve operating flexibility.
Maps
PDF files require Adobe Acrobat Reader. Please use the zoom tool to view details of the map and allow time for the map to reload. The numbers indicating alternative substation locations do not represent a ranking of preference.
Locations of project activities (PDF, 701 kb)
Property tracts by owners (PDF, 480 kb).
(Note: This information was provided by the GIS departments of Bradley and Hamilton counties.)
Electricity load growth per year, 1997 - 2001, for the TVA service area (PDF, 363 kb)
Environmental Review
In keeping with TVA’s commitment to resource stewardship, the appropriate National Environmental Policy Act reviews, such as an Environmental Assessment, will be conducted to ensure that the environmental impacts associated with this project are recognized and fully evaluated. TVA invites public comment on the scope of the environmental review and issues that should be addressed. If you are aware of any such issues or have concerns about potential environmental effects, please tell TVA about them by one of the methods outlined below. The comments will be used in determining the scope of the environmental review.
Public involvement
TVA representatives held an open house on Thursday, April 8, to receive comments, answer questions, and discuss the project. If you were not able to attend the open house but have questions or comments, you may send a letter or e-mail message to the contact person listed below.
TVA is interested in receiving comments on the potential of the proposed actions to affect people and the environment and in identifying any other issues associated with this proposal. These comments will be used in reaching location decisions and in detailed planning.
Along with your comments, please provide us with your name and address. The information is for TVA use only and will not be provided to outside parties for mailing lists. All written comments on this proposed action should be received no later than May 8, 2004.
Project timeline
| Activity | Date |
| Open house | April 8, 2004 |
| Comments due | May 8, 2004 |
| Determine substation location and transmission line routes | Summer 2004 |
| Announce site of substation and line routes | Summer 2004 |
| Begin obtaining property owners’ consent to survey | Summer 2004 |
| Begin surveying | Summer 2004 |
| Complete environmental review | Winter 2004-2005 |
| Begin acquisition of right-of-way and substation property | Fall 2005 |
| Begin construction on substation | Winter 2005-2006 |
| Project activities complete | Before 2007 |
Related information
Project fact sheet (PDF, 64 kb)
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