By Riccardo Bastianello and Crispian Balmer
VENICE/ROME (Reuters) - If everything had gone according to plan, Tuesday's high tide should never have reached the lagoon city of Venice, let alone flood its basilica, submerge its squares and inundate its historic palaces.
But things in Italy rarely go according to plan, especially if you are talking about the execution of a mega infrastructure project involving massive public financing and complex, cutting-edge engineering.
Following the worst flooding in its history in 1966, the Italian government asked engineers to draw up plans to build a barrier at sea to defend one of the world's most picturesque yet fragile cities from the constant threat of high tides.
Fast forward to 2003 and construction finally started with completion set for 2011. But the project, known as Mose, has been plagued by the sort of problems that have come to characterize many major Italian construction programs -- corruption, cost overruns and prolonged delays.
Engineers are now predicting the sea defense system will go on line at the end of 2021 at a cost of 5.5 billion euros ($6.1 billion) against an original estimate of 1.6 billion euros.
"These delays are an embarrassment for all of Italy and we urgently need a solution," Alessandro Morelli, the head of parliament's transport commission said on Wednesday, promising to dispatch lawmakers to Venice to review the program.
The good news is they will discover that the building work is almost complete. The bad news is no-one is sure how it will cope with the growing phenomenon of flooding and whether it might prove too little, too late.
Mose is an acronym for "Modulo Sperimentale Elettromeccanico", or "Experimental Electromechanical Module", and refers to the biblical figure Moses who parted the Red Sea to enable the Israelites to flee to safety from Egypt.
The modern-day Moses consists of 78 bright yellow mobile barriers buried in the water that, when activated, will rise above the surface and prevent surging tides from the Adriatic Sea flooding the delicate Venetian lagoon.
"If Mose had been working, then we would have avoided this exceptional high tide," Venice Mayor Luigi Brugnaro said after Tuesday's floods, which followed a tide of 187 cm (6ft 2ins) -- the worst since the 194 cm recorded in 1966.
All 78 gates are now in place and engineers are working on the mechanics of raising them simultaneously once tides of more than 110 cm are forecast, with first testing expected next year.
But there is no guarantee it will go smoothly.
Part of the submerged infrastructure has already started to rust and a source close to the consortium building the mobile dam told Reuters on Wednesday it would cost some 100 million euros a year to maintain -- much higher than original estimates.
The source, who declined to be named, was confident that once operational, it could defend Venice from tides of up to 3 meters high, well beyond the current record.
But some experts worry that the system was not designed to deal with the sort of rising sea waters that recent climate-change models have predicted.
A report http://www.unesco.org/new/fileadmin/MULTIMEDIA/FIELD/Venice/pdf/rapporto1_very%20high%20res.pdf by the U.N.'s science and culture agency UNESCO says Mose was planned on a base scenario of sea levels in the northern Adriatic rising some 22 cm by 2100, but many scientists fear that assumption is far too optimistic.
"The planned mobile barriers might be able to avoid flooding for the next few decades, but the sea will eventually rise to a level where even continuous closures will not be able to protect the city from flooding," the 2011 UNESCO report concluded.
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(Writing by Crispian Balmer; Editing by Gareth Jones)