Saint Petersburg Dam

Flood control dam complex near Saint Petersburg, Russia

The Saint Petersburg Flood Prevention Facility Complex , unofficially the Saint Petersburg Dam, is a long complex of dams for flood control near Saint Petersburg, Russia. The dam extends from Lomonosov northward to Kotlin Island (and the city of Kronstadt), then turns east toward Cape Lisiy Nos near Sestroretsk. The complex is intended to protect Saint Petersburg from storm surges by separating the Neva Bay from the rest of the Gulf of Finland. The dam's tunnel also serves as the final leg of the Saint Petersburg Ring Road. The northern and southern parts of the dam act like two giant bridges, providing access from the mainland to Kotlin Island and Kronstadt. Historically, storm surges from the gulf have caused over 300 floods of varying severity within the city, some with devastating effects. The dam has the capability to protect the city from water rising up to This prevented what would have been the 309th flood in the recorded history of the city, saving some 1.3 billion roubles of projected damage. 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 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, part of a larger program to clean the water in the Neva Bay. In the early literature, high winds from the Gulf of Finland were often cited as the cause of Neva flooding, but scientists now understand the more complex hydrometeorological chain of events behind it. A low pressure region in the North Atlantic moves onshore, giving rise to cyclonic lows on the Baltic Sea. The low pressure of the cyclone draws greater than normal quantities of water into the virtually landlocked Baltic. As the cyclone continues inland, long low frequency seiche waves are established in the Baltic. When the waves reach the narrow and shallow Neva Bay, they become much higher, ultimately breaching the Neva embankments. The worst such flood occurred on 19 November 1824, when the water level rose above normal. The playwright Alexander Griboyedov wrote, "The embankments of the various canals had disappeared and all the canals had united into one. Hundred year old trees in the Summer Garden were ripped from the ground and lying in rows, roots upward." When the waters receded 569 people were dead, with thousands more injured or made ill – more than 300 buildings had been washed away. The 1824 inundation is the setting for Alexander Pushkin's famous poem, The Bronze Horseman (1834). Other disastrous floods took place in 1777 and 1924. One of the most recent floods occurred on 18–19 October 1998, when the water level rose to .

For years, prominent scientists and statesmen of imperial Russia developed various plans for flood protection, and the Soviet Union implemented the idea. The flood of 1955 finally made it clear that the city needed a protective dam. Many options were considered before the Soviet government decided on a complex of 11 dams, including a six lane highway on the top. The project was begun in 1979, and construction continued through 1995, at which point the dam was around 70% complete, when due to difficulties obtaining financing after the fall of the Soviet Union the project was suspended until 2005, when President Vladimir Putin ordered its resumption. Construction was completed in 2011, and the formal opening of the complex was on 12 August 2011. The entire project cost roughly 109 billion rubles ($3.85 billion), Damming an estuary and altering its flow pattern generates a number of physical and biological impacts; the disruption of the normal flow obstructs natural current and affects the water's habitat. The 60 canals and rivers that flow through Saint Petersburg will all discharge into the dammed area. Currently the Neva's water is good enough to serve as a source for drinking water. To address the problem of water pollution, the city's government adopted a plan to upgrade the city's sewage system to limit the amount of untreated wastewater release to less than 0.1%. The measures being taken seem to be quite efficient – after the launch of the modern long awaited South West Wastewater Treatment Plant in 2006 the amount of biological and phosphate waste is expected to be lowered by 60% and 25%, respectively. Over 30 water purification installations are placed around the complex, a part of a larger effort to clean the water in Neva Bay.