The Thác Bà Hydropower Plant is a major hydropower project located within the province on the Chay River, built between 1964 and 1971 with assistance from the Soviet Union. Construction began on August 19, 1964. Despite frequent air strikes by the United States Air Force during this period, the first unit of the power plant was commissioned on October 5, 1971; the second unit followed on August 1972, and the third unit on May 19, 1972. The power plant currently has a capacity of 120 MW, and has an energy generating potential of 400 million kWh/year. The project as built has a dam 48 m high and 657 m long, creating a gross storage capacity of 2.49 cubic kilometres with a live storage of 2.16 cubic kilometres on the Chay River draining a catchment of 6430 km at the dam site. The reservoir is 60 km with a water spread of 235 km at the Full Reservoir Level of +58 m. The project has been designed for a maximum flood discharge of 3,650 m/s. The other ruling levels of the project are: dead storage level in the reservoir +46.0m and maximum flood level of +59.65 for a thousand-year flood.