With passenger elevators out of service at Carlsbad Caverns National Park, visitors hoping to see the Big Room have to hike down, and then back up, this steep walkway into the Natural Entrance/NPS

Seeing "the Grand Canyon with a roof over it" at Carlsbad Caverns National Park of late has has been more strenuous for those seeking to marvel at the park's Big Room, as safety issues with the elevators used to lower visitors into the cave and back out again have taken them out of service. Instead, you face a long, steep hike in and out of the cave entrance in addition to the more-than-a-mile walk through the room.

Add it all up, and your walk will be closing in on four miles by the time you've hiked down the zig-zagging walkway into the cave in southern New Mexico and toured the Big Room. With any luck, though, one set of elevators could be back in service around Memorial Day Weekend, according to National Park Service officials.

“We’re working to make it happen as fast as we can," said Rick Frost, associate regional director for communications in the Park Service's Intermountain Region office in Denver.

Out of commission are both the elevators that normally take visitors down into the cave and back up to the surface, as well as the freight elevators that are viewed as a backup to the passenger elevators. The passenger elevators, which had had their motors overhauled in 2007 and at the time were thought to be good for another 20 years, were shut down in mid-November after one of the two motors broke down, said the official. Using just one of the elevators wasn't considered wise, he said, as there would be no backup in case it failed, too.

“Both of the motors were overhauled at the same time, both of the motors were manufactured at the same time, so there was a concern that if one failed, the other might fail," Mr. Frost explained.

To get by while officials discussed the best approach to dealing with the failed motor, park officials have wanted to turn to the two freight elevators to haul passengers. But those elevators were shut down last March after an inspection found structural issues with their steel supports. As a result, the cave has been without elevator service since mid-November, forcing visitors who wanted to see the room that Will Rogers once compared to the "Grand Canyon with a roof" to hoof it in and out.

The problems point to the maintenance struggles the National Park Service faces across its 84-million-acre domain. Keeping mechanical equipment and its infrastructure functioning in the humid climate of the cave is challenging, said Mr. Frost on Friday. And replacing the motors used for the passenger elevators will be no easy task, either, he said.

“The firm that’s looking at the passenger elevators says if we take these motors off the elevators and replace them, the motors are 10,000 pounds each. That’s going to take a crane. We’ll have to have a crane pull the motors out of the shaft and replace them with new motors. That process takes a very long time. Six months or more," Mr. Frost said.

These two motors normally power the passenger elevators at Carlsbad Caverns. However, the rotor shaft in motor No. 4 broke in November 2015, and officials took the elevators out of service/NPS

So while officials debate the best answer to that issue, this week they'll ask for bids on repairing the structural issues with the freight elevators, he said. If things go smoothly, a contract could be issued by mid-March, work could commence in April, and the freight elevators could be back in service by the end of May, said Mr. Frost.

Cost-wise, of the $44 million worth of deferred maintenance at Carlsbad Caverns, roughly half of that total has been earmarked for repairs and renovations on the elevators, according to park officials. However, the vital role of the elevators in getting visitors into and out of the cave has placed a priority on gettting the freight elevators back in service as soon as possible, said the regional official.

“The elevators are critical enough infrastructure, that gets attention as soon as it needs it," said Mr. Frost.

The loss of the elevators has had an impact on visitation to the national park. Since mid-November, when the passenger elevators were taken off-line, through this past week ticket sales were down 14 percent when compared to the same period a year ago, he said.