ACADIA NATIONAL PARK – The historic carriage road bridges built by John D. Rockefeller Jr. will be reconditioned for future generations under a plan being proposed by the National Park Service.

The project, which is estimated to cost $3 million, represents the first time in the history of the famed carriage road system at Acadia that a major public effort has been undertaken to repair and recondition the bridges, according to park officials.

Officials hope to start the work this spring, but must secure both federal and state permits.

“We consider [the bridges] to be among the most important cultural resources the park has, so we treat them accordingly,” said Lee Terzis, Acadia cultural resources program manager, on Wednesday.

The project would include all 25 of the bridges and would entail full stabilization, cleaning and repointing of all stone and capstone work.

The park’s plan, now available for public review and comment, also calls for a system that would prevent water from infiltrating the bridges – the prime cause of deterioration over the years.

The project also would improve adjacent sections of historic hiking trails, as well as elements of the surrounding cultural landscape.

The park already has done the Stanley Brook Bridge and the Jordan Stream Little Bridge in order to better understand what would be involved, including costs.

Rockefeller designed and supervised construction of the 25 bridges, which include 15 masonry arch bridges, nine steel stringer bridges and one concrete culvert.

The bridges are part of Acadia’s beloved 57-mile carriage road system, which includes 12 miles of roads that are privately owned but open to the public.

Rockefeller’s crews maintained the carriage road system and bridges until his death in 1960. The National Park Service assumed responsibility for the system after Rockefeller’s death, but has not done any major improvements to the bridges in the past 40 years.

The carriage road system, which was resurfaced in the early 1990s, as well as 13 of the masonry bridges, have been listed in the National Register of Historic Places since 1979, park officials said. The remaining bridges are eligible for the same designation.

Although park officials predict that the bridge work will have an impact on wildlife, landscape and water quality, they expect it to be minor and short-lived.

Public comments will be accepted until March 4. Copies of the environmental assessment have been delivered to public libraries and town offices for public review.

Comments should be mailed to Len Bobinchock, acting Acadia superintendent, at P.O. Box 177, Bar Harbor 04609-0177.