Rebuilding Fengman Beside the Old Dam

Fengman’s older dam had been reinforced and maintained over many years, but an energy-sector account says it was classified as a “sick dam” in 2007. The phrase was a technical safety category. In October 2012, the National Energy Administration approved a comprehensive treatment and reconstruction project. The approval called for six new 200-megawatt units and retained two existing 140-megawatt third-phase units; these were planned project figures, not a statement of current configuration.

The station sits above a large reservoir and a downstream river system, so a new structure had to address the old dam’s condition while maintaining control over stored water. Construction was a long transition rather than a single replacement day. The old structure continued to impound water while its successor moved from approval into construction, linking the engineering schedule to reservoir management.

The new dam was built about 120 metres downstream from the old one, with main work beginning in 2014. For several years the two structures occupied the same reach. The old dam continued to hold the reservoir while crews built the successor, so engineers had to coordinate the new foundations and concrete work with water levels and the operation of the existing project.

That arrangement makes “reconstruction” more accurate than a simple equipment swap. A dam is tied to the riverbed, its gates, the reservoir and the system that moves water downstream. The new structure had to be ready to receive the reservoir before the old one could relinquish that task. During the transition, construction sequence and water management were inseparable: one barrier remained in service while the other was made ready to take over.

On 20 May 2019, a 5-metre opening was blasted through a reserved retaining sill in the old dam. Songhua Lake water flowed into the space between the old and new structures, and the new dam began holding water. The contemporary report described a further stage planned for about 10–12 days later: after water levels equalized, retaining sills in the other sections would be dismantled.

Songhua Lake is an artificial reservoir formed by the Fengman project. A provincial environmental account lists water supply, power generation, flood control, irrigation, navigation, fisheries and recreation among its functions. It also describes reservoir water continuing through the Songhua reach in Jilin City to serve the city’s waterworks. These uses help explain why work on the dam concerned more than the generating units: stored water had to be transferred into a system serving several purposes.

The handover joined construction to the management of stored water. Keeping the old dam in place during the downstream works, then opening a controlled passage between them, let the project move from one retaining structure toward another in stages.