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coming from stormwater runoff with expanding development in the area and from agricultural practices. Sedimentation covers up the streambed habitats, filling crevices used by invertebrates and insects that are food for fish, and covering fish nesting areas. Biologically, these stresses alter species diversity in the streams as sensitive species are eliminated and more tolerant species increase. Sediment can also be rich in fertilizer and other sources of nutrients that foster algal growth that can dramatically reduce oxygen in the water, especially during low flow conditions. This section of the Harpeth River is also heavily influenced by the effluent from the city of Franklin’s sewage treatment plant and suffers from low oxygen levels because of algal growth.
The Harpeth River Watershed Association (HRWA) began a preliminary environmental assessment of the proposed transmission line corridor along the West Harpeth in June. The HRWA also just completed a visual survey of sedimentation problems and habitat quality along the entire length of the Harpeth River. Based on this work, we are very concerned with the number of river crossings. Current transmission line crossings across the Harpeth River were found in our survey to be the sites of the worst bank erosion areas along the river, as illustrated below in Figure 1. At such sites, huge chunks of the bank the size of automobiles were falling into the river. Exposed banks are a major source of sedimentation. It appears that transmission lines in this area are handled with drastic vegetation removal programs up to the water’s edge, along with the heavy use of herbicides, both of which contribute silt and chemical pollutants to the water. Clearing the streamside vegetation also eliminates shade that protects the river from high water temperatures that contribute to water quality degradation.
Figure 1: Transmission line crossing of Harpeth River just north of Old Hillsboro Road in May 2001. Exposed banks are eroding and are source of sediment in the Harpeth River. © Mike Walton.
A transmission line corridor requires vegetation management to keep trees below the lowest point in the line across the width of the corridor, 100 feet for this proposed route. According to MTEMC, the height will be as low as 30 feet. This will require the removal of the canopy trees for any wooded habitat that the corridor crosses. Both the West Harpeth and Harpeth have mature canopy riparian corridors along the banks; thus, each crossing could entail clearing a 100-foot swath in this canopy.
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In addition, the proposed route would cut through a section of wooded wetland habitat that occurs in the West Harpeth floodplain and cut through numerous hedgerow habitats.
All streams and river segments proposed to be crossed by this transmission line have been identified as impaired by TDEC under section 305 of the federal Clean Water Act and are on the 303(d) List that is compiled by TDEC based on regular assessments. All streams and lakes on the 303(d) List are considered “water quality limited” and in need of additional pollution controls. Once a stream has been placed on the 303(d) List, it is considered a priority for water quality improvement efforts.
Both the 303(d) list and recent 305(b) report are available on the TDEC web site. However, the best way to visualize all the streams in the Harpeth River watershed on the 303(d) list is to look at the watershed map produced by the Cumberland River Compact and partially funded by the HRWA. These are available upon request.
The proposed transmission line route will add further sediment loading
and entail loss of important riparian habitat to all these stressed river and
stream segments that already have been identified by TDEC as priority areas for
restoration. The HRWA has already begun
working with landowners along this segment of the West Harpeth to identify
opportunities to stabilize streambanks and encourage native habitats in the
riparian zone and floodplain. Also, the
HRWA has just received a grant from the TN Department of Agriculture’s Nonpoint
Source Program to survey all the 303(d) listed streams in the entire watershed
in order identify priorities for reducing stresses and improve habitat
integrity. This proposed transmission line
route could significantly reduce these efforts and those of other groups to
restore the West Harpeth and Harpeth River in and around Franklin.
a) West Harpeth— The entire length of the West Harpeth and some of its tributaries are on the 303(d) List because of siltation problems from pasture grazing in the riparian zone, upland, and because of “livestock in streams,” according to the latest TDEC report, The Status of Water Quality in Tennessee Year 2000 305(b) Report. Along the 2.5-mile segment of relevance to the proposed transmission line corridor, much of the streambank supports a riparian zone with mature tree canopy, though it is not wide. In one ¼ mile segment where the line is proposed to span a bend in the river and make two crossings, much of the mature tree canopy was lost two years ago during a straight-line storm. Removing the remaining canopy over the river for the crossings would expose much of the river in this section to direct sunlight. Degrading the water quality, especially by increasing algal growth and reduced oxygen levels, will affect the Harpeth River which receives the water from the West Harpeth about 2 miles downstream. The water from the West Harpeth currently provides needed oxygen and dilution to the main Harpeth to ameliorate the stress from nutrient laden algal growth that can drive oxygen levels down low in the summer conditions.
b) Harpeth River— The segment of the Harpeth River from its headwaters to the confluence with the West Harpeth is listed on the 303(d) List because of siltation, loss of riparian habitat and other habitat alterations. All these problems stem from development and stormwater runoff as well as from agricultural practices that were described above for the West Harpeth. In addition, the section of the Harpeth downstream of Spencer Creek where the effluent enters from the sewage treatment plant until the confluence with the West Harpeth is impaired because of stormwater runoff and nutrient enrichment and low oxygen levels in the water. The two new transmission line river crossings within 1.5 miles of each other will cut across a bend in the river just after it flows under Hillsboro Road. Based on the HRWA visual assessment survey, these line crossings will remove riparian habitat with mature tree canopy. This will increase sedimentation as these denuded banks are affected by high flows during storms, and remove important shade cover. This stretch of the river is used recreationally for canoeing. Transmission line crossings will add a further challenge to developing the Total Daily Maximum Load implementation plan
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required under the Clean Water Act for the Harpeth River to address all sources for nutrient enrichment and low dissolved oxygen. This TMDL is under development by the EPA.
Recommendations:
1. This proposed route for the transmission line does not appear to reflect much consideration for ecological issues involved in this corridor across the northern area of Franklin, TN. Before surveying this proposed route, we recommend that TVA’s transmission and power supply division contact the environment division to review the proposed route. We believe that the number of crossings over such short river segments would be identified as a problem for water quality and stream habitat integrity without having to even go on site.
2. Before further work is done by TVA on this proposed route to survey and conduct environmental assessments, the HRWA is willing to work with TVA and MTEMC and all other stakeholders to assess whether there is a possible route across the northern area of Franklin that addresses all the issues comprehensively: protection of ecological integrity, historic resources, archeological resources, open space, recreational uses, and aesthetic values. The HRWA recognizes the challenge in siting transmission lines, especially in a developing area like Franklin, and is willing to work closely with all interested parties on whether a corridor exists across northern Franklin to balance all these values. However, concerns with this proposed corridor does not mean that the HRWA supports a particular route at this time or supports the current assertions that such a transmission line and proposed substation are the best approaches to addressing electrical load needs in the area.
3. Because of the many issues involved in this corridor across northern Franklin, it appears that TVA and MTEMC need to evaluate other options besides the proposed substation and high voltage transmission line. The HRWA is willing to work with TVA, MTEMC, and energy experts on ways to integrate programs to reduce peak load demand, plan for power supply, and upgrade distribution systems that could also be applied to other areas in the 870 square-mile Harpeth River watershed.
4. If TVA feels compelled to continue to the next stop in the process with this proposed route, the cumulative effects of all these crossings over such short river segments must be assessed in the Environmental Assessment that is performed for any proposed route, especially since all three waterways that the transmission line is currently proposed to cross are interconnected.
Contact:
Dorene Bolze
Executive Director
Harpeth River Watershed Association
P.O. Box 1127
Franklin, TN 37065
615-790-9767
The mission of the Harpeth River Watershed Association mission is to protect and restore the Harpeth River. Only two years old, the HRWA is committed to re-building and maintaining the ecological integrity of the watershed amidst the various human uses of the landscape. We are doing this by forging partnerships in order to provide information, training, and programs that enable homeowners, landowners, farmers, families, businesses, researchers, government agencies, and elected officials to directly enhance areas of the Harpeth River watershed.