After 15 years of debate and stalling, a 25-km flood protection barrier designed to protect St. Petersburg's historic neighborhoods from flooding seems set to go ahead.

The structure, which will cross the Neva Bay to Kotlin Island, is expected to cost $420 million to complete. Late last month, officials held public consultations on a new environmental-impact assessment prepared by Dutch consulting firm Consortium NEDECO, which concluded the barrier would have no significant negative effects on the environment or water quality in the Neva Bay or the Gulf of Finland.

Opponents of the barrier have argued that, by interfering with the water's flow, what already exists of the barrier has allowed pollutants to build up in Neva Bay – and that the completion of the barrier could make this problem worse.

St. Petersburg was founded on a river delta, in a low-lying area where the Neva River meets the Gulf of Finland, which leaves it vulnerable to flooding. If the water levels in St. Petersburg were to rise more than three meters, flooding would be expected across most of Vasilevsky Island and throughout much of the city's central Admiraltiisky district, where the bulk of the city's historic buildings are located. Streets would be under water, basements flooded and parts of the metro flooded, and the city's water purification plants would overflow, bringing sewage into the city's streets.

Since the city's founding in 1703, 295 floods have been recorded, an average of almost one a year. The most serious flood occurred in 1824, when water levels reached 421 centimeters and more than 300 people died. Planning for modern flood defenses began in the 1960s after a major flood in 1955, though the issue has remained controversial.

Today, the barrier is about 65 percent complete. The dam sections and some of the water passages have been built; the water passages have steel gates that can be lowered when water levels rise.

The barrier – as it stands – provides a degree of flood protection, but it would not protect the city in the case of very high water levels, like those recorded in 1824. NEDECO's Herman Gerritsen, the environmental assessment's project leader, said statistical trends suggest that major floods of around three meters occur every 50 years or so, which suggests St. Petersburg could suffer another major flood soon.

"Floods generally occur in the winter and early spring," Gerritsen said. "The last one was in March this year. They occur when strong winds in the central Baltic Sea blow water into the eastern part of the Gulf of Finland, causing water to pile up in the Neva Bay. Water then flows into the Neva and through the city's various canals, which allow water to inundate the city very quickly and from numerous points."

The public consultation showed significant opposition to the project remains. A long-term opponent of the barrier, Dr. Vladimir Znamensky, said that by interfering with the water flows, the barrier has disturbed the natural self-cleansing processes of the area's water systems, which has meant that pollutants have built up in the Neva Bay.

The Neva Bay has been damaged by chemical and organic pollutants, and fish catches have decreased significantly in the last 20 years. Greenpeace campaign manager Ivan Blokov, who believes the barrier is a greater threat to St. Petersburg's environment than floods, also warned that NEDECO could not properly estimate the barrier's impact on water flow.

However, the environmental-impact report argues that the environmental impact of the barrier to date has been negligible compared to the impact of wastewater, industrial discharge and heavy-metals and oil pollution. At the same time, it said, flooding causes around $69 million in damage every year, and floods are becoming more frequent.

"The completion of the barrier is not going to influence the ecological condition of the Neva Bay," said Rosa Mikhailenko, from Morzashita, the city Government agency responsible for the barrier project. "The influence of the barrier on the environment will be about 1 percent compared to other factors like sewage dumping and the development of new housing in swamp areas around the Neva Bay."

The EIA report says once the barrier is completed, just under 5 percent of additional coastal area along the northern and southern shores of Neva Bay will have its water circulation slowed. The eastern part of the bay will only be marginally affected.

"The areas with low velocity will be small," said Gerritsen. "When the water velocity is lower, it leads to increased growth of reeds and water plants, and that can actually be beneficial for fish spawning and birds," he added.

The report's conclusions mean that the European Bank for Reconstruction and Develop-ment (EBRD) is likely to approve the loan for the project and that construction works will probably begin soon. A starting date has not been set because the EBRD will not be able to disburse the funds until funding for the entire project has been secured. Nevertheless, Mikhailenko from Morzashita said that the City Government expects the barrier to be completed by 2008.

It is expected that the EBRD will provide credit for about half of the cost. The recent assessment and public consultation were part of the EBRD's screening process of the project. A loan for $215 million is expected to be approved by the EBRD board of directors in October.

The Russian government has announced it will fund between 17 and 20 percent of the project, and the Nordic Investment Bank and the Kuwait Fund for Arab Economic Development are considering contributing to the remaining costs.