St Petersburg’s 25.4km flood protection barrier, designed to hold back rising waters from the Gulf of Finland, is nearing completion. Built at a cost of GBP1.8 billion (USD 2.7), the barrier also serves as a vital element of the St Petersburg Ring Road – a 115km highway which will encircle the city.
The need for the construction of a ring road around St Petersburg was first recorded in the 1965 General Development Plan of Leningrad (now St Petersburg). In 1984 the authorities of Leningrad and the Leningrad region started construction works.
However, construction was temporarily halted, firstly by the Soviet economic crisis of 1989, and then again by the dissolution of the Soviet Union in December 1991. In 1992, construction was stopped again as concerns were raised about the possible ecological damage resulting from the construction of the St Petersburg Flood Barrier.
In 2001, construction of the ring road was restarted, and, as environmental fears were allayed and concerns about climate change and rising sea levels grew, construction of the flood barrier continued in 2005 – almost 30 years since construction began.
Halcrow was awarded the overall design responsibility for the St Petersburg Flood Protection Barrier project. The project management responsibility is shared between the PM/E (Project Manager/Engineer) and the PIU (Project Implementation Unit) – which are both Russian led consultancies.
The road tunnel
The cut and cover road tunnel runs beneath the flood barrier’s 200m main navigation channel. Comprising two 13.25m wide main tunnels, each with a three-lane highway, and emergency access and cable tunnels, the 42.1m wide tunnel structure has been formed from reinforced concrete, with a double PVC waterproofing membrane on the outside.
US Tariffs are shifting - will you react or anticipate?
Don’t let policy changes catch you off guard. Stay proactive with real-time data and expert analysis.
By GlobalDataA 3m service tunnel runs between the two main highway tunnels, whilst other service tunnels to the side of the main carriageways carry cables and utilities, serve as an additional emergency access and exit route.
The initial section of the road tunnel, which now runs beneath the navigation channel, had already been built by the time construction re-started in 2005.
Left to deteriorate, the initial works involved the rehabilitation of the existing construction and studies to determine the most effective way of linking the existing tunnel sections with the new sections needed to complete the project.
Nine of the tunnel sections, each up to 60m long, were originally constructed during the 1980s, but not connected with movement joints. The movement joint design posed some engineering challenges, since once in situ, it would be impossible to access them for maintenance or repair – necessitating a design specification which called for a lengthy, high-performance lifetime.
The contract was awarded to Trelleborg Engineered Systems and the solution chosen represented the first use of their 40m-wide, 7m-high Omega seals, named after the similarity of their cross-sectional profile to the Greek letter, in a cut-and-cover tunnel of this kind.
Needing to exclude water at high pressure, but still maintain adequate three-dimensional flexibility, the installation uses a double-seal approach, an inner Omega seal backing up the outer one, built to withstand temperatures from -30 to +70 degrees Celsius.
The structure of the connecting sections, together with the Omega seals allows them to support the navigation pass’ foundations, water pressure on the tunnel walls and the high traffic load from cars and lorries.
In 2008, the navigation channel was opened, submerging the tunnel and completing 70 per cent of the tunnel works. Work continued to build the remaining 30 per cent, involving another 362m of tunnel and a 356m ramp.
Founded on some 1,835 cast-in-situ piles with diameters up to 1200mm and up to 23m long, this stage of the project requires 176,900 cubic metres of concrete, 26,400t reinforcement, 4,900t of sheet pile walls and 2,200t of constructional steel.
Construction of the tunnel and approach roads is being undertaken by Boskalis, with responsibility for earthworks, dredging and backfilling; whilst Hochtief is responsible for the concrete and piling works.
The first section of the ring road was opened to traffic on the 26 December 2002. In December 2007 the Northern sections of the road were opened, linking up with the St Petersburg Flood Barrier from Kronstadt and also connecting with the train station at Gorskaya and other northern and eastern elements of the motorway. The southern half of the ring road is under construction.
St Petersburg flood barrier
St Petersburg has an amazing history – one that is blighted by a succession of catastrophic floods. Since 1703, the city has been flooded more than 300 times, the most catastrophic was in 1824 when the water level rose by 4.21m; the second , one hundred years later, was in 1924 when levels reached 3.6m. It has been 85 years since the last major flood.
At the worst the city would be flooded to a depth of 5.15m with up to three million of St Petersburg’s five million inhabitants directly affected. Some of the world’s most precious monuments would be swamped at unimaginable cost.
The barrier will help protect one of the world’s most beautiful cities. Its lavish architecture, an extraordinary history; and rich cultural traditions have inspired and nurtured some of the modern world’s greatest literature, music, and visual arts.
And it’s for this reason, the Directorate for the Flood Protection Barrier of the Ministry of Regional Development of the Russian Federation, assisted by Halcrow, is spearheading the completion of the St Petersburg Flood Protection Barrier.
The two huge 4,500t steel gates across the main 200m wide navigation channel were recently closed for the first time. Each the size of an ocean-going vessel some 122m long, 23.5m high and 4.7m deep. Together, they are capable of holding back storm surges that would otherwise wreak havoc on the city.
Navigation S1
The second navigation channel for local shipping has a channel with horizontal width of 110m, a lift gate of 119m width, depth 12m and thickness is 9m. The gate sits in a concrete slot below cill level. The closing time is 30mins. Navigation draught for ships is 7m. The lift bridge rises from 16m above the channel to 25m to allow ships through.
Navigation S2
At navigation S1 the channel is 16m deep. The gate is 23.5m high. The floating gates are moved out of their docking chambers by tractors that push them through a connecting arm. Each ‘A’ frame arm is 130m long, and 65m wide. They each revolve around 1.5m dia. solid steel ball hinges encased in a bronze bushing with a pressurised lubrication system.
Floods
59 floods in the last 30 years, 20% of all the floods in the city’s 306 year history.
Sea sluice
Designed to minimize the impact of the barrier on water-flow conditions. Each sluice has 10 to 12 steel radial gates. Each gate is of 24m horizontal width, 2.5m to 5m deep. Hydraulic cylinders help push the gates down through up to 600mm of ICE but the gates are concrete filled to provide additional weight to assist the hydraulic cylinders.
Navigation S1 Navigation S2 Floods Sea sluice
