he Saint Petersburg Flood Prevention Facility Complex , unofficially the Saint Petersburg Dam, is a 25 km (16 mi) complex of dams for flood control near Saint Petersburg, Russia. The dam extend from Lomonosov northward to Kotlin Island (and the city of Kronstadt), then turns east toward Cape Lisiy Nos nearSestroretsk.
The complex is intended to protect Saint Petersburg from storm surges by separating the Neva Bay from the rest of the Gulf of Finland. Historically, the storm surges from the gulf had causedover 300 floods in the city, several of which had a massive devastating effect. The dam has the capability to protect the city from water rising up to 5 m (16 ft).
The construction of the flood prevention complex started in 1978 and became one of the longest construction projects in Russia. After a protracted halt in the 1990s and early 2000s, construction was resumed in 2005 due to the intervention of Russia’s President Vladimir Putin, a native of Saint Petersburg. Putin finally inaugurated the finished complex in 2011,when all the facilities at the southern part of the dam were completed, along with the 1.2 km (0.75 mi) long underwater roadway tunnel below the main southern lock, the longest undersea tunnel in Russia.
Over 30 water purification installations are placed around the dam, a part of a larger program to clean the water in the Neva Bay.The dam tunnel is also the last completed part of the Saint Petersburg Ring Road. The northern and southern parts of the dam act like two giant bridges and provide an easy access from mainland to Kotlin Island and Kronstadt.