1970s and 1980s. Significant changes occurred in the economy of the Tennessee Valley and the nation, prompted by an international oil embargo in 1973 and accelerating fuel costs later in the decade. The average cost of electricity in the Tennessee Valley increased fivefold from the early 1970s to the early 1980s. TVA canceled the construction of 12 nuclear power plants in the 1980s. The 1970s saw the last and most controversial of the TVA's large dam-reservoir projects, Tellico Dam.