A system under strain

Another cautions that a retaining wall beside commuter rail tracks in Quincy is deteriorating, risking its collapse onto the tracks and train derailment.

And a third describes a set of circuit breakers, 30 years old and unreliable, on the Orange Line that could expose passengers and employees alike to extreme electrical fault currents: “The potential damage includes explosions, fire, flying debris, and release of hazardous materials.’’

These are among the 51 unfunded Massachusetts Bay Transportation Authority projects, categorized by the agency itself as dangers to “life and limb,’’ that were referred to in an alarming independent review last month but never publicly listed or explained.

A Globe review of the specific projects, obtained through a public records request, reveals numerous potential hazards as a result of inadequate funding in a system where many cables, signals, and other pieces of equipment have been in service well beyond their recommended life span.

But the agency, whose own staff previously ranked the projects as essential, now says some are not as urgent as once suggested. And following the release of the report, the agency said 10 of the projects would be funded from either the yearly operating budget or federal grants. William A. Mitchell Jr., the interim general manager, said last week that all pieces of the transit system identified in the review by former John Hancock chairman David F. D’Alessandro have been addressed or monitored and are in at least “stable condition.’’

The Quincy retaining wall, for example, was patched a few months ago to the point that it is no longer in danger of falling, but still needs to be replaced eventually.

“We don’t agree 100 percent with Mr. D’Alessandro’s report as to whether they were’’ critical safety issues or not, Mitchell said last week in response to questions from the Massachusetts Department of Transportation board, which recently began overseeing the T.

The conflicting messages from the MBTA raise questions about the agency’s internal ranking system, in addition to those already raised about the safety of T equipment. The Globe review found some of the projects that ranked as safety priorities seemed to have a more obvious effect on reliability than safety. And many unfunded projects not included in the top 51 safety concerns may in fact be more pressing than those that received the highest possible safety ranking.

“They need a much different process that has professional safety and engineering people reviewing’’ projects, D’Alessandro said. “And I think these people should be outsiders.’’

Last week, at the urging of Governor Deval Patrick, the T selected an outside consulting firm to review its process of selecting which projects to fund from its limited budget.

“It’s an art, not a science,’’ Jonathan Davis, deputy MBTA director, said of the ranking process.

Though Patrick ordered both of the recent reviews, he has not identified a new source of money to pay for the costliest projects.

The transit system, already heavily in debt, spends almost all of its $500 million capital budget every year on projects designed to maintain the system and the purchase of replacement train and bus fleets, yet still finds its $3 billion backlog of projects growing.

“This wouldn’t happen if we had a brand-new system,’’ said Victor Rivas, the MBTA’s deputy director of capital budget, who leads a small team of people who sift through the funding requests from various department supervisors every year. “We don’t know where the surprises are going to happen, but we have to prepare for where they might be.’’

Some of the problems identified within the 51 projects are unseen by riders, but still have an effect on safety or service. For example, it would cost more than $3 million to build platforms needed to fix Green Line and Blue Line cars in MBTA garages. Workers on the Green Line now rely on temporary wooden platforms to repair cars, a safety and liability risk to workers and a drag on the time it takes to fix trolleys, according to one memo.

Every year, the MBTA amends its five-year capital spending plan to add projects. The current total value of the plan is $3.7 billion.

But only about $200 million was available last year to spend on new projects, which had not already been included in the five-year plan. And the competition for that money inside the MBTA is fierce. More than a dozen departments submit hundreds of requests.

A three-member budget team (soon to add a fourth member) then ranks the projects on safety, health, environmental impact, operational impact, costs vs. benefits, effect on legal commitments, and the degree to which they improve the system’s overall infrastructure.

To rank projects, the team reads questionnaires submitted by each department and then interviews department leaders.

Safety concerns, though they drew the most attention in last month’s external review of the T, are worth a maximum of 10 points on the T’s 100-point rating system.

And some projects that did not receive the most urgent rating of 10 on the safety scale seemed to pose a greater risk than those that did.

Managers on the Orange Line, for example, say the wheel bearings on the train cars have been in use since the early 1980s and have outlived their useful life of 1 million miles by about 10 percent. If the bearing system fails, trains could derail, according to a memo requesting an additional $4 million to complete an overhaul that has already received $2 million. One such wheel bearing has already failed while a train was carrying passengers, according to the memo.

“An emergency replacement of all . . . must be undertaken,’’ the memo stated.

The $4 million to complete the project was not added to the capital budget, though the T hopes it eventually qualifies for stimulus money for an expanded revamp.

John C. Lewis, acting chief operating officer, said in an e-mail that the failure of the wheel bearing during passenger service was detected when the crew noticed a strange odor. Passengers got off the train and the car was removed from service for a day so workers could replace the part. Though inconvenienced, the passengers were not at risk, he said.

Though the T has a safety department, its members are not part of the group that decides which projects to fund. But the T says its chief operating officer, its design and construction chief, and its general manager all play a role in approving the plans.

“This is a joint effort and the discussions go on not once every year, but throughout the year,’’ said Rivas.

Davis said the T’s operations staff holds primary responsibility for safety on a daily level.

“These people would not let [passenger] service out there in an unsafe condition,’’ Davis said.

But the documents provide a rare record of the MBTA’s deficiencies written by the same men and women who run it.

And D’Alessandro is concerned that the system forces these managers to scramble too often, finding money from one pot to cover the most urgent needs as they arise, while depriving other projects. Bridge projects that take several years, for example, are funded one year at a time, meaning engineers have to work on faith that they will get the money to complete the projects.

“Where’s the commitment?’’ D’Alessandro said. “Tell me where it is for sure that you’re going to be doing this over the next four years? And that each of those years, there’s a commitment to follow up?’’

Noah Bierman can be reached at nbierman@globe.com.