Georgia Power has received the final major permit needed for its new nuclear units under construction at Vogtle with the issuance of a water discharge permit from state environmental regulators.

The National Pollutant Discharge Elimination System (NPDES) permit, issued by the Georgia Environmental Protection Division, authorizes the discharge of clean, recirculated water used in power production at Vogtle units 3 and 4 back into the Savannah River. It also sets monitoring and reporting guidelines.

The company said that it returns nearly 90% of the water it withdraws for use in power production across the state into waterways. Like the two existing Vogtle units, the new units will use cooling towers to reduce the volume of water used in plant operations. The towers also regulate the temperature of water returned to the river.

Within the past week, the project to build two Westinghouse AP1000 pressurized water reactors has reached construction milestones with the completion of the placement of the “turbine tabletop” for unit 3 and the arrival on site of the last of the four steam generators for the new units.

The turbine tabletop is a 3 metre thick concrete pedestal that will support the unit’s turbines. Georgia Power announced the completion of the placement, which involved a 15-hour continuous concrete pour, on 18 November.

The next day, the company announced the arrival on site of the last of the steam generators from South Korea. Each unit has two steam generators, which convert water into steam using the heat produced in a nuclear reactor core. The components weighs about 600 tonnes each and are over 24 metres long.

Vogtle 3 and 4 are the first new nuclear units to be licensed and begin construction in the USA in over 30 years. Construction began on unit 3 in March 2013 and on unit 4 in November that year. The units are expected to enter service by mid-2019 and mid-2020, respectively.

Georgia Power, a subsidiary of Southern Company, owns 45.7 % of the Vogtle project, with co-owners Oglethorpe Power Corporation, the Municipal Electric Authority of Georgia and Dalton Utiltities. Construction is being overseen by Southern Nuclear, who will also operate the units on behalf of Georgia Power.