On Jan. 14, Metro-North Railroad's oldest movable span on the New Haven Line -- the four-track Walk bridge in South Norwalk -- was covered with snow and ice and became stuck all four times it was opened to allow passage of ships into Norwalk Harbor, Metro-North President Howard Permut said.

The first two openings of the 114-year-old movable South Norwalk bridge, at 6:30 and 9:36 a.m., were made to allow ice-breaking ships to pass, resulting in rail delays of 50 minutes and 1 hour and 17 minutes when the bridge got stuck open, according to Metro-North records.

In the evening, the bridge got stuck again at 6:49 and 9:17 p.m., remaining open 40 and 36 minutes in those instances.

The episode is one example of the need to overhaul four of five New Haven Line movable bridges, which are more than a century old and often become stuck as they await replacement or major upgrades, Permut said. The fifth span, the Peck Bridge over the Pequonnock River in Bridgeport, was replaced in 1998 and generally operates well, the railroad says.

"I want to emphasize first off that the bridges are safe, but the operations of opening them and maintaining infrastructure of such advanced age is pretty expensive," Permut said. "Whenever the bridges are stuck, there are serious delays."

The challenge to maintain the Walk span and three other older bridges -- in Westport, Greenwich and the Devon section of Milford -- is heightened by frequent openings dictated by a federal requirement, Permut said.

The railroad is required to move the spans on demand for commercial vessels, and at regular intervals for recreational craft.

"There is no way the government is going to let us turn them into stationary bridges because the waterways have to serve the maritime community," Permut said.

In 2010, the five movable rail spans failed to close about 70 of 747 times they were opened, causing about 75 delayed trains, with that unreliability directly linked to their age, Permut said.

In 2010, the Cos Cob bridge in Greenwich over the Mianus River saw 26 malfunctions during 406 openings, while the Devon bridge had 16 malfunctions during 108 openings, the Saga bridge in Westport had six problems in 31 openings, and the Walk had five in 206 openings, and the Peck bridge had four malfunctions.

Because bridge malfunctions cause extended service disruptions, Metro-North keeps a maintenance squad of six bridge mechanics, engineers and others on hand for each of hundreds of annual bridge openings on the New Haven Line to address any emergencies, a cost neither boaters nor the federal government defray, Permut said.

"Keeping equipment and infrastructure this old in working order is a considerable investment, and if we didn't keep the maintenance crews on hand the delays would be much, much longer," he said. "When we need to open the bridges there is, besides the manpower issues, the higher probability that the bridges will not work and stop service."

The state Department of Transportation is designing projects to revamp the Walk bridge, built in 1896, and the Saga bridge, built in 1904. Plans for both are about 60 percent complete and are to be ready for public bidding in February 2014, DOT spokesman Judd Everhart said.

A recent study concluded the Devon Bridge, built in 1905, will need full replacement, while a study to be completed in October will consider whether to rehabilitate or replace the Cos Cob bridge, he said.

The bridges are subject to differing rules governing opening and closing, changes adopted a decade ago when Metro-North sought relief from some bridge opening requirements during peak hours, Permut said.

In the case of the Walk bridge, Metro-North has received some relief after the U.S. Coast Guard approved new regulations allowing the bridge to stay down weekdays between 7 and 8:45 a.m. and 4 and 6 p.m.

Additional restrictions on opening bridges during peak times would help prevent rail delays and wear and tear on the aging bridges, Permut said.

"Throughout the years, all of these bridges have experienced issues with their mechanicals, and that is to be expected of bridges of this age," Everhart said. "To date, Metro-North's capable maintenance forces have responded when such problems arise and have been able to correct them as expeditiously as possible to keep our rail riders moving and to meet the needs of the maritime community."

Regulations governing opening and closing of moveable bridges vary from bridge to bridge said Lt. Judson Coleman, chief of the Waterways Management Division of the U.S. Coast Guard Sector Long Island Sound.

"We need to provide for the safety of navigable waterways and ensure that reasonable needs of navigation are accommodated," Coleman said.