ACADIA NATIONAL PARK — All four members of Maine’s congressional delegation expressed their concerns to federal officials Thursday about a proposed change in companies that handle concessions in Maine’s only national park.

Reps. Mike Michaud and Chellie Pingree sent a letter Thursday to the U.S. House Natural Resources Committee asking lawmakers on the panel to review the National Park Service’s procedures for awarding concessions contracts.

Acadia Corp., based in Bar Harbor, has been in the retail business in Acadia National Park for 80 years. In September, it lost the park’s concessions contract when the National Park Service awarded a 10-year contract to Dawnland LLC to take over the park’s concessions next spring.

“We question, however, whether or not the NPS’ decision not to renew an agreement with the corporation that has served [Acadia] for more than 80 years was the best decision for the park and the local economy,” Michaud and Pingree said in the letter.

Sens. Susan Collins and Angus King also issued a jointly written letter to John Jarvis, head of the National Park Service, on Thursday. In their letter, Collins and King say they believe there are “serious flaws” in the process that led to Dawnland being awarded the contract. They ask in the letter:

— Why was Acadia Corp’s long-standing and exemplary experience as a concessionaire at Acadia not considered?

— Why was the perspective of a technical adviser from Acadia National Park not considered by the panel during the five-day selection process?

— How will the National Park Service re-evaluate the selection process to ensure fairness and transparency?

“We are deeply troubled by the process that the NPS employed in considering applications for concessions operations at Acadia,” Collins and King wrote.

The contract still must go through a 60-day review period in Congress before it becomes final. That review period is expected to start next month when the park service submits the proposed contract to the Natural Resources Committee, according to Michaud and Pingree’s letter.

Dave Woodside, president of Acadia Corp., said Thursday in an email that he is excited to hear that Maine’s congressional delegation continues to look into the matter.

“It is gratifying to know that the efforts are continuing to overturn this poor decision,” Woodside wrote. “The outpouring of support for Acadia Corp. retaining the contract have been overwhelming.”

Starting in March, Dawnland LLC is expected to take over operations at three seasonal retail sites in the park — at the Cadillac Mountain summit, Jordan Pond and Thunder Hole. There is a gift shop at each of the three sites and, at Jordan Pond, a restaurant that serves approximately 1,000 people per day and has roots that go back to the 1870s.

Dawnland’s parent company, New Mexico-based Ortega National Parks LLC, holds concessions contracts in Death Valley, Hawaii Volcanoes and Carlsbad Caverns national parks and at the Muir Woods and White Sands national monuments. Ortega also owns or operates beach clubs, restaurants and shops in New York, Golden Gate Park in San Francisco, and Santa Fe, N.M.

The decision to not award the contract to Acadia Corp. has been met with objections by some residents and business leaders who say that having a New Mexico firm profit from the park’s concessions will lessen the impact of sales in the park on the local economy. As of Wednesday, an online petition asking Congress to investigate the award of the contract to Ortega had attracted nearly 6,100 signatures.

Ortega has said it plans to offer jobs to people who have worked in the park for Acadia Corp. Acadia Corp. has other retail shops in downtown Bar Harbor that it plans to continue operating.

Michaud and Pingree note in their letter that the recent shutdown of the federal government forced Acadia Corp. to close its park operations for 17 days. Woodside has said the temporary closure of the restaurant and three gift shops for more than two weeks in early October resulted in estimated revenue losses of nearly $700,000.

“The catastrophic impact of the shutdown on access to the restaurant at the height of Maine’s fall foliage season cannot be overstated,” Michaud and Pingree said.

Acadia Corp. closed down its operations in Acadia last month, and Dawnland is expected to begin operations there next March, when the contract is scheduled to go into effect.

“Acadia is a critical part of eastern Maine’s economy, with a significant impact on our entire state,” Michaud and Pingree wrote in the letter. “The NPS recently estimated that visitors to ANP in 2012 created $186 million in local economic benefits. As visits to NPS lands across the country decline, the time is long overdue for Congress to take a serious look at how the NPS regulates access to its parks and facilities for members of the public and private contractors.”