Cultural resources include archaeological and historical sites. These sites are important because they provide insights into past cultures and religions. Some of these sites are threatened and are listed on the National Registry of Historic Places. The National Historic Preservation Act of 1966, amended in 2000, was enacted to preserve historic properties throughout the United States.
The impact on cultural resources from electric transmission lines are most likely to occur during the construction phase. In addition, access to remote areas of archaeological significance may result, especially if access roads are left in place after construction is complete.
Historic sites can be impacted visually by the completed lines, resulting in fewer visitors to the site. Potentially, pollution can also affect the site.
Here is an example of how an endangered historic site can impact electric generation. In 2008, the Great Falls Portage, Great Falls, Montana, was listed as one of the 11 Most Endangered Historic Places in the United States. The Great Falls Portage, one of the best preserved and most accessible landscapes along the Lewis and Clark Trail, is a windblown, undeveloped rural area surrounded by mountains and a panorama of blue Montana skies. This National Historic Landmark marks the location where, in 1805, the Lewis and Clark expedition faced its most challenging obstacle —the 18-mile, 31-day portage around the Great Falls of the Missouri River.
In May of 2008, the Southern Montana Electric Generation and Transmission Cooperative, Inc. (SME) sought financial support from the USDA Rural Utilities Service to build the Highwood Generating station, a $720 million coal-fired power plant that would produce 250 megawatts of power and serve up to 120,000 rural electricity customers from Great Portage to Billings. The plant was proposed inside the boundaries of the Great Falls Portage National Historic Landmark, raising grave concerns about the impact that project would have on the site. Construction plans included a large 435-acre power generating facility with a 400-foot smokestack, four 262-foot wind turbines, secondary buildings, access roads, transmission lines, lights, and miles of railroad tracks. Despite receiving 1,500 letters of protest from concerned citizens, the Cascade County Commission voted in 2006, and, most recently, in January 2008, to rezone this agricultural land to allow for industrial activity.
In March of 2009, the USDA Rural Utilities Service ceased providing funding for the project and SME was modifying its plans to include a natural gas generation facility that could be an alternative to, or supplemental to, earlier plans for a coal-fired facility. Currently, the United States Army Corps of Engineers needs to issue a Section 10 water intake permit for the facility and is now the lead federal agency for the project. The National Trust along with a large group of partner organizations are participating in the National Historic Preservation Act Section 106 consultation process for the project. Concerns about the impact to the cultural landscape of the Portage site remain unresolved.
In November of 2009, the SME took a loss of $9.1M because it abandoned the plans for a coal-fired generating facility and opted for a gas-fired generating facility, and the site has been removed from the list of most endangered historic places in the United States.
During the siting process, a cultural impact assessment is usually conducted. This includes identification of properties on or eligible for the National Register of Historic Places located within and adjacent to the proposed electric transmission line or generating facility. At a minimum, the following actions are included in the assessment:
- Contacting the State Historic Preservation Office to determine if any archaeological or historic sites are located in the area of the proposed transmission line.
- Conducting background research on the site by compiling data on previously recorded prehistoric and historic sites and historical structures and other cultural resources.
- Defining an area within a set distance from the center line of a proposed transmission, usually 0.25 miles, as the corridor study boundary. Sites within and immediately adjacent to the corridor should be included in the impact assessment.
- Determining the potential and/or probability of the existence of prehistoric, historic, and archaeological sites, based on historic and prehistoric human activities.
- Conducting cultural resource surveys as directed by the State Historic Preservation Office.
- Determining the potential visual impact to the affected archaeological and historical sites.
Much of this information can be included as a layer used in the GIS analysis of transmission line route selection.
Because of the sensitivity of this data, each State Historic Preservation Office may have special requirements for the release and use of archaeological and historic site information.
- Judicious route selection
- Compliance with all applicable state and federal requirements and permit restrictions
- Development of a mitigation plan to be followed during construction
- Flagging of cultural sites identified within the transmission line right-of-way
- Immediately contacting the State Historic Preservation Office should archaeological artifacts be uncovered during construction