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Final Environmental Impact Statement-500-kV Transmission Line in Middle Tennessee

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Information about this document as published in the Federal Register.

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Tennessee Valley Authority (TVA).


Issuance of Record of Decision.


This notice is provided in accordance with the Council on Environmental Quality's regulations (40 CFR parts 1500 to 1508) and TVA's procedures implementing the National Environmental Policy Act. TVA has decided to implement the preferred alternative identified in its Final Environmental Impact Statement (EIS), 500-kV Transmission Line in Middle Tennessee.

In implementing Alternative 1, TVA has decided to construct and operate the new 500-kV transmission line between Cumberland Fossil Plant in Stewart County, Tennessee, and TVA's Montgomery 500-kV Substation in Montgomery County, Tennessee. The 38.5-mile transmission line would be constructed within Corridor B and on the Cumberland River South and Industrial Park Central alternative alignments described in the Final EIS.

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Charles P. Nicholson, Senior NEPA Specialist, Environmental Policy and Planning, Tennessee Valley Authority, 400 West Summit Hill Drive WT 9B, Knoxville, Tennessee 37902-1401; telephone (865) 632-3582 or e-mail

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TVA owns and operates a system of transmission lines that move electricity throughout the TVA service area, which comprises most of Tennessee and portions of six adjacent States, and to adjacent utilities. Electric loads on portions of this system in the Middle Tennessee area have grown steadily in the recent past and are projected to continue to grow. This load growth will soon exceed the capability of high-capacity transmission lines serving this area. In addition, the loss of two or more of these lines could result in the loss of service over a wide area and possible damage to generating equipment in at least two locations. Therefore, TVA needs to increase transmission capacity in this area.

TVA published a Notice of Intent to prepare this EIS in the Federal Register on November 27, 2001. Two public scoping meetings were held in December 2001 and attended by about 50 people. Written scoping comments were received from two Federal agencies, two State agencies, and several individuals. The Notice of Availability of the Draft EIS was published in the Federal Register on April 18, 2003. TVA held two public meetings on the Draft EIS in May 2003 and accepted comments through early July. During this period, TVA also accepted comments received during a series of eight open houses held in June 2003 to review potential transmission line routes. Comments on the Draft EIS were received from about 200 individuals and several State and Federal agencies. TVA also received petitions signed by about 400 individuals expressing opposition to various potential transmission line routes. The Notice of Availability for the Final EIS was published in the Federal Register on July 22, 2005. Although not required, TVA provided 30 days for comments on the Final EIS. Appendix I of the Final EIS contains summaries of and responses to the comments TVA received on the Draft EIS.

Alternatives Considered

TVA uses a detailed, comprehensive siting process when it plans its transmission line projects. This is an iterative process that takes into account important environmental and cultural resource features that become constraints on locating proposed lines. Broad study corridors are initially defined and potential line routes are subsequently located within the study corridors. Because transmission line right-of-ways (ROWs) are much narrower than the study corridors, important features that are associated with specific corridors can often be avoided when final line routes are selected. It is at this point that potential environmental impacts are more fully identifiable.

TVA identified three alternatives in the EIS.

Under Alternative 1—Cumberland-Montgomery Study Area, TVA would construct and operate a 500-kV transmission line from Cumberland Fossil Plant to the Montgomery 500-kV Substation. A new bay and additional 500-kV breakers would be installed at the Montgomery Substation. Four broad alternative corridors for this transmission line were analyzed in the EIS. Two of these corridors, the 37-mile Corridor B around the south and west side of the city of Clarksville and the 32-mile Corridor D around the north of Clarksville, were identified as identified in the Draft EIS as preferred by TVA. Following the release of the Draft EIS and the subsequent public meetings and open houses, TVA identified proposed transmission line routes within Corridors B and D. Alternative alignments were developed for some segments of both the Corridor B and D routes. Depending on the alternative alignments being considered, the Corridor B route is between 38.1 and 38.9 miles long, and the Corridor D route is between 31.8 and 37.7 miles long.

Under Alternative 2—Cumberland-Davidson Study Area, TVA would construct and operate a 500-kV transmission line from Cumberland Fossil Plant to TVA's Davidson 500-kV Substation in Davidson County, Tennessee. A new bay containing a 500-kV breaker would be installed at the Davidson Substation. Two broad alternative corridors about 50 and 51 miles long were analyzed in the EIS.

Under Alternative 3—No Action, TVA would not construct the proposed transmission line. This would result in the risk of loss of electric service in a portion of Middle Tennessee with a total load of over 4,000 megawatts. There would also be risk of loss of system stability and resultant damage to generators at TVA's Cumberland and Paradise generating plants. In order to minimize the risk of instability, generation would have to be reduced at these plants during some system conditions, further exacerbating the risk to service in Middle Tennessee.

The construction and operation of the proposed transmission line would be similar under Alternatives 1 and 2. The transmission line would use self-supporting galvanized, laced steel structures about 85 to 125 feet tall. The average distance between structures would be about 1,000 feet. The electrical conductors would consist of three sets Start Printed Page 65959of three cables suspended beneath the structure cross-arms by insulators.

The transmission line would be built on a ROW 175 feet in width. TVA would purchase easements from landowners for the new ROW. Because of the need to maintain adequate clearance between tall vegetation and the transmission line conductors, as well as to provide access for construction equipment, most trees and shrubs would initially be removed from the entire width of the ROW. Trees outside of the ROW which are tall enough to pass within 10 feet of a conductor if they fell towards the line would also be removed. Following line construction, the ROW would be revegetated with low-growing plants. The ROW can be used by the landowner for many purposes that do not interfere with the maintenance and operation of the line. TVA would periodically inspect and conduct maintenance activities on the completed line. The major maintenance activity is vegetation management, conducted to maintain adequate clearance around the conductors. This would consist of both felling tall trees adjacent to the ROW and control of vegetation within the ROW. Management of vegetation within the ROW would use an integrated vegetation management approach based primarily on mechanical mowing and herbicide application.

Under both action alternatives, TVA would also construct a new bay containing a 500-kV breaker at Cumberland Fossil Plant. Depending on the transmission line route selected, an additional length of new bus work would be needed inside the plant switchyard to connect the new bay to a line pull-off structure.

TVA identified the Alternative 1 as the preferred alternative in the Draft EIS. In the Final EIS, TVA identified the Corridor B Route in the Alternative 1 Cumberland-Montgomery Study Area, with the Cumberland River South and Industrial Park Central alternative alignments, as preferred.

Comments on the Final EIS

TVA received comments on the Final EIS from six State and Federal Government agencies and from two individuals.

Some commenters stated that TVA did not adequately consider all viable alternatives to constructing a new 500-kV transmission line, including upgrading existing 161-kV transmission lines to 500-kV capacity. TVA evaluated four corridors for the Cumberland-Montgomery alternative. Corridor C, as described in Section of the FEIS, offered the potential for using the right-of-ways of several existing 161-kV transmission lines and interconnecting pieces of new right-of-way. This corridor was not preferred, and subsequently not evaluated in detail in the FEIS, because of its relatively high land use impacts and because of engineering considerations. One of these considerations was the need to deenergize and dismantle 161-kV lines 18 to 24 months prior to the scheduled line completion date. This extended line outage would have presented an unacceptable risk to area electrical service. Another consideration was that the 161-kV transmission line segments have right-of-ways that are 100 feet wide and to accommodate both the 500-kV and 161-kV lines, these right-of-ways would have to be expanded to at least 175 feet wide. Numerous houses and commercial buildings occur along these 161-kV right-of-ways, and the number that would have to be purchased and demolished would be considerably greater than for either the Corridor B or Corridor D routes. These considerations would also apply to other potential routes involving upgrading existing 161-kV transmission lines to 500-kV capacity.

The Environmental Protection Agency (EPA) requested more discussion of the suitability of other types of utility rights-of-ways for co-location of a transmission line. Using non-electric rights of way to route transmission lines is often unsafe and avoided for that reason. A transmission line can cause induced currents in natural gas and petroleum pipelines, resulting in increased corrosion. While this can be addressed by retrofitting the pipeline, to do so is expensive. Conductor to ground faults from the transmission line are also a potential hazard to pipelines. TVA typically does not site transmission lines parallel to and within railroad rights-of-ways because of interference with railroad communication systems. The need to maintain electrical clearance to allow safe train passage also requires that the transmission line be some distance from the railroad, resulting in minimal overlap of right-of-ways and little savings in the required land area.

The EPA noted that the preferred route and alignments identified in the FEIS would have greater impacts on wetlands than several other route/alignment combinations analyzed in detail, and asked for more explanation of the basis for the selection. This is given below in the “Decision” section. The EPA also questioned how this mitigation ratio relates to permitting requirement and noted that the proposed 1:1 mitigation ratio for impacts to high quality wetlands is likely inadequate.

TVA has not yet submitted a Clean Water Act Section 404 permit application to the U.S. Army Corps of Engineers (COE). Based on the types of wetlands impacts that would occur (primarily conversion of forested wetlands to scrub-shrub and emergent wetlands, and small areas of fill for transmission structure foundations and access roads), the project will likely qualify for Section 404 Nationwide Permit 12—Utility Line Activities. It has been TVA's experience that the Nashville District COE typically does not require any compensatory wetlands mitigation in this kind of situation. The proposed 1:1 mitigation for impacts to 3.8 acres of high quality forested wetlands is amount that TVA believes is appropriate, and if COE requires additional mitigation as part of its approval, TVA would comply with this requirement.

The preferred route would affect a total of 23.2 acres of wetlands. The majority of this wetland area, 17.0 acres, is comprised of non-forested wetland types where the level of impacts would be low and wetland functionality would not be materially affected. Impacts to the affected 6.2 acres of forested wetlands would be different because of the long-term conversion of these wetlands to non-forested wetland types. While all wetlands share many important functions, forested wetlands have additional functions and attributes. As explained in the FEIS, 2.4 acres of these forested wetlands were classified as moderate quality (Category 2) and 3.8 acres were classified as high quality (Category 3). The potential for impacts is greatest for these high quality wetlands, and thus they are the focus of TVA's mitigation efforts. The 1:1 mitigation ratio would offset the overall loss of forested wetland functions that would result from the conversion from forested to non-forested wetland types and is consistent with the 1990 Memorandum of Agreement between EPA and COE on determining mitigation under Section 404 guidelines.

The EPA requested additional discussion on the application of the 300/1200 foot buffers to reduce exposure to electric and magnetic field (EMF) buffers from transmission lines paralleling highways. During the line routing process, TVA establishes 300-foot buffers around occupied buildings other than schools and 1200-foot buffers around schools. TVA does not establish buffers along highways, although in practice stretches of highways are buffered from the transmission line due Start Printed Page 65960to the buffers around buildings adjacent to highways.

The EPA requested clarification of the environmental justice information. TVA considers potential environmental justice effects as a matter of policy. FEIS Figure 4-1 shows the percent nonwhite population by census block group for the Cumberland-Montgomery study area and Table 4-5 lists the actual percentages for the census tracts along the Corridor B and Corridor D routes. The individual census tracts were not mapped because their small size would make interpretation of the map difficult. All of the census block groups with nonwhite populations greater than 25 percent are in Montgomery County in the immediate vicinity of Clarksville or north of U.S. Highway 79. Nonwhites comprise 4.7, 26.8, and 19.8 percent of the populations of Stewart County, Montgomery County, and Tennessee, respectively. None of the census blocks along the Corridor B route in Montgomery County have nonwhite populations that exceed county-wide or state proportions. The nonwhite population for the one Corridor B census block in Stewart County is 6.9 percent, higher than the county average and much lower than the state average.

The proportions of the population below poverty level in Stewart County, Montgomery County, and Tennessee are 12.4, 10.0, and 13.5 percent, respectively. None of the census tracts along the Corridor B route (listed in FEIS Table 4-5) have poverty rates significantly greater than the state rate and three tracts slightly exceed the local county rates. Because of the low potential for disproportionate impacts to disadvantaged populations that would result from selection of the Corridor B route, TVA has determined that measures to mitigate environmental justice impacts are not necessary.


TVA has decided to implement the preferred alternative identified in the Final EIS, Alternative 1 with the Corridor B route and Cumberland River South and Industrial Park Central alternative alignments.

Alternative 1—Cumberland-Montgomery Study Area was selected over Alternative 2—Cumberland-Davidson Study Area because of the shorter line length, lower level of impacts to several natural resources, and lower cost. Within the Alternative 1 study area, Corridors B and D were selected as the preferred corridors in the Draft EIS based on a combination of engineering attributes, natural and cultural features, and land use attributes. Among other attributes, these two corridors were the shortest and contained the smallest area of forest. The Final EIS contains a detailed comparison of proposed line routes in Alternative 1—Cumberland Montgomery Study Area Corridors B and D.

The selection of the Alternative 1 Cumberland-Montgomery Study Area Corridor B Route over the Corridor D route was based on several factors. While shorter and with less impacts on wetlands and less forest fragmentation, the Corridor D Route would require the relocation of more residences and have a greater impact on planned residential and commercial development. A portion of it would have been located on or very close to Fort Campbell Military Base, potentially interfering with aircraft operations. It would also have affected the Ringgold Mill Complex historic site.

The Cumberland River South alternative alignment of the Corridor B Route was selected over the Cumberland River North alignment in order to avoid ongoing residential development and land suitable for future development. The selected alignment also avoids an agricultural area with extensive underground drainage that the Cumberland River North alignment would have crossed.

At the eastern end of the Corridor B Route, the Industrial Park Central alternative alignment was selected over the Industrial Park East and Industrial Park West alignments because of its shorter length and reduced amount of right-of-way to be acquired. The Industrial Park Central alignment also runs parallel to and shares part of the right-of-way of an existing 500-kV transmission line, further reducing the amount of new right-of-way to be acquired and land use impacts.

In reaching this decision, TVA has carefully considered the comments and concerns voiced by the public. Based on the comments TVA received during the scoping and EIS review processes, the effects on landowners from having the transmission line built on or near their property was a major concern. TVA has attempted to minimize these impacts during the transmission line siting process, and the selected route affects slightly fewer landowners than the Corridor D Route. It also would require fewer residential relocations and have fewer buildings within 300 feet of the line. Commenters also expressed concerns about impacts to cultural and natural resources. The selected Corridor B Route would have less impact on cultural resources than the Corridor D Route, and the Tennessee State Historic Preservation Officer has concurred with TVA's determination that the Corridor B Route would not adversely affect any archaeological or historic sites eligible for or listed in the National Register of Historic Places. The U.S. Fish and Wildlife Service has concurred with TVA's determination that the Corridor B Route would not adversely affect species listed under the Endangered Species Act.

Environmentally Preferred Alternative

Alternative 3—No Action is the environmentally preferred alternative because the impacts associated with constructing and operating a high voltage transmission line would not occur. This alternative, however, would result in the risk of the loss of electrical service to a large area of Middle Tennessee with a total load of over 4000 megawatts and is considered unreasonable. The loss of this electrical service would result in social and economic impacts.

Of the two action alternatives, Alternative 1—Cumberland-Montgomery Study Area is environmentally preferred over Alternative 2—Cumberland-Davidson Study Area. Potential transmission line routes in the Alternative 1 study area average about 20 percent shorter than those in the Alternative 2 study area and would require the purchase of less right-of-way and have less impact to forests, wildlife populations, and streams.

Neither of the two Alternative 1—Cumberland-Montgomery Study Area transmission line routes studied in further detail, the Corridor B route and the Corridor D route, is clearly environmentally preferable over the other. Of the various alternative alignments for the selected Corridor B route, the Cumberland River North alignment is environmentally preferable over the selected Cumberland River South alignment because of less impact on wetlands, ecologically significant sites, and forested stream crossings. None of the Industrial Park alternative alignments are clearly environmentally preferable over the others.

Environmental Commitments

For the reasons discussed in the Final EIS and summarized here, TVA is committing to the following measures to avoid, reduce, or mitigate the potential environmental impacts associated with these actions:

  • In order to reduce potential impacts to groundwater, TVA will not apply herbicides aerially along the ROW between a point about 0.4 miles northeast of Highway 12 (at transmission line structure 136) and the Montgomery 500-kV Substation. The Start Printed Page 65961use of fertilizers will also be avoided or minimized in this area.
  • In order to reduce the impacts to wetlands, TVA will provide compensatory mitigation for 3.8 acres of high quality forested wetlands at a 1:1 ratio. Compensatory mitigation measures include, but are not limited to, the purchase of credits in an existing mitigation bank within the hydrologic unit for the project area or an adjacent hydrologic unit, and restoration of forested wetlands in or adjacent to the project area hydrologic unit by TVA or through an in-lieu-fee agreement with a state agency or private conservation organization. A higher mitigation ratio will be used if required by the Section 404 permit issued by the Corps of Engineers.
  • No invasive plant species will be planted on the new ROW.
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Dated: October 20, 2005

W. David Hall,

Vice President, Electric System Projects.

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[FR Doc. 05-21696 Filed 10-31-05; 8:45 am]