The shutdown of the L train’s East River tunnel will be painful for commuters no matter how long it lasts.

But the MTA has to find ways to limit the pain and make sure the project doesn’t run into any delays like those that have affected other large public transit efforts, notably the Second Avenue subway.

Problems on the L train line, from crowded platforms to delays in service, are nothing new. But come 2019, most L train riders will find themselves without a train at all, when the Canarsie Tunnel closes for Superstorm Sandy-related repairs. They’ll need alternatives — from buses to bike lanes — and plenty of patience.

That’s why it’s so important that the $477 million project be on time and on budget. And that’s why the MTA will need to pay close attention to every stage of the project from day one, with plenty of checks along the way.

The joint venture selected to do the $477 million project is Judlau Contracting and TC Electric, and it’ll have to get the work done right. But Judlau was partly responsible for Second Avenue subway work delays, according to MTA board member Charles Moerdler.

MTA officials said the company’s other work, including the R train’s Montague Tunnel repair, was successful. And officials say they have built in daily penalties for any delays in the L train project, and incentives to finish early.

If the MTA board approves the contract, as it is expected to do, Judlau and TC Electric will be tasked with fixing the Canarsie Tunnel, making two stations accessible and adding a power substation to enable more trains to run. The project is to start April 2019 and take 15 months.

Judlau and other contractors didn’t meet Second Avenue subway goals until Gov. Andrew Cuomo put pressure on them to do so. Similar problems with the L repairs would cause a far more severe impact. Commuters make more than 200,000 trips under the East River via the L every day.

The stoppage won’t be easy in the best of circumstances. The MTA can’t let the L train be held in the station any longer than absolutely necessary.