Public Utilities Regulatory Priorities Act of 1978 (PURPA) and Hydroelectric Power: Mine Falls, NH

In 1978, in response to the international oil crisis of the mid-1970s, Congress and the administration of President Jimmy Carter collaborated to pass and enact the Public Utilities Regulatory Policies Act (PURPA). The purpose of PURPA was to both promote energy conservation and to stimulate the production of domestic energy, particularly from cogeneration and renewable sources. Among the sources of renewable energy, hydroelectric power was most important. In particular, PURPA focused on the development of small hydroelectric projects at existing dams. During the past couple of years I’ve had the good fortune to conduct cultural resources evaluation of several of these small hydro facilities. In 2022, this included the Mine Falls Project on the Nashua River in Nashua, NH in collaboration with my colleagues at the Northeast Archaeology Research Center. The Mine Falls Project is owned by the City of Nashua, NH.

One of the ways that PURPA sought to stimulate new low-head hydroelectric facilities was to allow “non-utility generators” to produce power for consumer use, thus breaking the monopoly on power production held by a relatively small number of energy-producing utilities. PURPA led to a dramatic increase in the number of small and low-head hydroelectric projects on waterways that, because of their scale, had not been feasible for development by the larger utilities but which would fill more local and regional power consumption needs. The economic feasibility of these smaller facilities was created by the requirement in PURPA that states create mandatory purchase requirements from them. 

Following passage of PURPA in 1978, it took several years for hydro developers to identify sites and complete the initial planning. By the early 1980s, however, a large number of small hydroelectric projects were being developed on streams and rivers throughout the nation. Nearly all are of similar design: small in scale and constructed of reinforced concrete with few or no architectural embellishments. Most were licensed in the early and mid-1980s for 40-year terms, making for a significant number of relicensing projects in the early and mid-2020s. In order to qualify for the preferential loans and rates under PURPA, these new small hydroelectric facilities were required, among other things, to be located at existing dams. As a result, cultural resources are always an important consideration in the recent relicensing efforts.

Although PURPA required that new hydroelectric facilities make use of existing dams, the Federal Energy Regulatory Commission (FERC) allowed a great deal of leeway in the interpretation of this requirement. The development of the Mine Falls Hydroelectric Project (FERC No. 3442), in Nashua, NH, provides a useful example. The project emerged first in late 1978, not in the context of taking advantage of PURPA but for strictly local concerns. The City of Nashua suffered an immense blow in the late 1940s when its largest employer, the Nashua Manufacturing Company, a vast textile factory complex by then owned by Textron, Inc. announced that it was ceasing operations. This meant that more than 10% of Nashua’s total population would be out of a job. The City’s business and political leaders quickly got to work, and by the 1970s had nearly filled the Textron complex with new businesses, to the point that the city needed more electricity.

The US Army Corps of Engineers in late 1978 identified the historic Mine Falls dam, which had been built in the 1820s as part of the massive, and historically significant, water power complex in Nashua, as likely site for a new hydroelectric project. The dam, and the power canal that led from the Mine Falls to downtown Nashua, continued to serve as a source of water power into the mid-20th century, though the dam, which had been extensively renovated in the 1920s, had not been used for power generation in decades. Plans were approved and funding was in place by the early 1980s, and construction began in May 1984. Once work on the Project began, the developers found that the original dam lacked the structural stability to provide both sufficient water power and downstream safety, and in early 1985 was demolished and the current concrete dam built in the same location.

Because the Mine Falls Project was built in the mid-1980s, it had not yet reach the 50-year threshold for being considered eligible for the National Register of Historic Places under standard criteria of eligibility. Instead, I evaluated the Project facilities, including the dam, intake canal, and powerhouse, under Criterion Consideration G, which allows resources to be determined eligible for the NRHP if they exhibit exceptional significance. The New Hampshire SHPO concurred in my recommendation that the Project is not eligible at this time, but that it should be evaluated again when it reaches 50 years of age.