Two-and-a-half years ago, the leaders of the MTA embarked on a massive public outreach campaign to convince New Yorkers that there was "simply no other option" but to fully shut down the L train for more than a year. Led by longtime transit planners and engineers, they cited a slew of complicated findings and internal expertise that ultimately led them to conclude that the tunnel's bench wall, which holds the all-important electrical cables, would have to be rebuilt from scratch.

If Governor Andrew Cuomo's surprise intervention last week is to be trusted, none of that was ever true—or perhaps it was, and the governor's decision to overturn years of planning because of a random street encounter will prove to be a catastrophic mistake. There is a lot we can't yet know.

Then there are the things we thought we knew. For years, the MTA has warned of dangerous particle dust in the damaged bench wall, which they claim made a partial shutdown impossible. The problem was laid out in a bleak video of the decrepit tunnels shown at public hearings across the city. It noted that the damage cause by Superstorm Sandy was "just too much for a nights and weekends closure," due primarily to the "special precautions and procedures" necessary to mitigate dangerous silica dust kicked up by the crumbling wall.

"Even if we did shut down the tunnel for the weekend," a narrator explains, "we couldn't bring back normal service until the following Tuesday or Wednesday because of the time we'd need for the cleanup and silica testing." In order to mitigate the risk of the tiny molecule—which is known to elevate the risk of lung cancer in certain doses—the city had reportedly purchased a ventilation and filtration machine the length of a football field. Workers were instructed to wear respirators, while the hermetically sealed tunnel would ensure that passengers remained out of harm's way.

So, what's changed? Under the MTA's new plan, the work will take place one tube at a time during nights and weekends, and will involve hanging the new cables along the tunnel wall. While the full 32,000 feet of duct bank no longer has to be removed, the most damaged bits of the bench wall will still need to ripped out. The current plan was developed by people who spent a total of one hour evaluating the Canarsie Tunnel in person, and at this point it's unclear how much of the wall will need to be demolished—and thus, how much of the dangerous dust will make its way into the air.

In a brief phone interview with Gothamist on Tuesday, New York City Transit President Andy Byford said that the dust issue was one of the "key safety concepts" that he plans to explore as part of his forthcoming review of the proposal. But while he expects a "vastly reduced" amount of silica dust under the new plan, the transit leader conceded that a final determination can't be made until engineers conduct a full examination of the bench.

"I will not be giving my blessing to the plan going forward until the question of safe dust management and mitigation has been assured," he said, adding that an independent third party would also review the plan. "I will not be pressured on this due diligence exercise. It will be done properly."

Still, some transit leaders are wondering whether it was premature for the MTA to "accept" the governor's proposal without first ensuring that it would keep workers and passengers safe.

"There are real questions about the actual dust from this new plan, and how you stop that from coming into trains," MTA board member Andrew Albert told Gothamist. "How do you make sure you get everything out in time for the morning rush? How do you get the trash trains in there? Where do you store all this debris that you've removed so it's not a threat to the public?"

Figuring out that process could take much longer than anyone behind the plan is currently admitting. According to Lisa Daglian, the executive director of the Permanent Citizens Advisory Committee to the MTA, it could be up to a year before the new project is fully designed and deemed safe by both local and federal oversight authorities. A new NEPA evaluation may need to happen, she says, which would be carried out by the presently-furloughed Federal Transit Administration. (For his part, Byford says that starting the work on April 27th is "still our intention, if possible.")

"If certain things don't fall into place, I'm not sure this can start in April," admitted Albert. "The plans really are apples to oranges."

Meanwhile, the new racking system may present its own set of dust problems. Daglian says there are concerns that securely affixing cables to the tunnel could send dangerous dust airborne, potentially attaching to work trains that move through the system. "We haven't seen a plan or design, so we don't know what level of drilling is going to have to happen to make sure this racking system is safe and secure," she said. "You're going into a space that potentially hasn't been disturbed in 100 years."

"This is untested technology for a subway rehabilitation plan in the United States," added Daglian. "All of these things shouldn't just be on the minds of advocates, but on the mind of every New Yorker who uses the subway system."

UPDATE: Following publication of this article, MTA spokesperson Shams Tarek reached out to Gothamist to emphasize that Byford supports the plan and will work to ensure it happens. “As Andy Byford said in today's interview he welcomes the new plan and as a former safety director and president of NYC Transit he will make sure that officials follow all due diligence, with independent validation and environmental monitoring, to ensure complete customer and worker safety,” the spokesperson said.