Behind the scenes look at the repair work ahead this summer at Penn Station

PENN STATION, Manhattan (WABC) -- Making repairs to train tracks might sound simple, but at the country's busiest train station, repairs often come with delays.

On Thursday, we got a real eye-opening look down below Penn Station, and saw how much work there is to do.

One of the most critical junctions is an intricate web of tracks Amtrak calls 'A' interlocking, where two tracks spider web out to 21 tracks.

It is where the railroad is set to begin complex repair work.

"It is the replacement of the ballast. It's the replacement of ties, new steel, new switches," said Amtrak's Vice President of Operations Mike DeCataldo. "It all works as one component."

It is work that is expected to take out 20 percent of NJ Transit, LIRR and Amtrak trains during the summer.

"We will be required to adjust some schedules and we are working with Long Island and New Jersey Transit to do so," said DeCataldo.

He showed me the type of switch that needs to be replaced. There are many of them.

"Looking out at the interlocking, you see the number of switches we have together that produces the complexity that's needed to route the number of trains that we have on hand in the station," said DeCataldo.

Amtrak has already started some work on the weekends, but admits the last time there was work in 'A' interlocking was 25 years ago.

The work begins July 7th and runs through August.

"They have really done a lot of analysis and we are very confident that the schedule we have prepared is something that we can deliver," said DeCataldo.

There are safety issues too, officials stress. In a picture of repair work after a recent derailment, you can see the number of workers spread out over the area.

It will also be a big task for train dispatchers.

"Between the complexity of the options they have, the number of trains, it is one of the more daunting tasks on our railroad for a train dispatcher," said DeCataldo.

There is signal repair that also has to be done, but that, officials say, will be taken on at a later date.