Extending the safety areas on the shorter of Green Airport’s two runways is going to cost “considerably more” than the $77 million initially projected, while the $88 million estimated for extension of the main runway remains on target, Peter Frazier, interim director of the Rhode Island Airport Corporation, said Tuesday.

Design of the two projects ramped up as soon RIAC and the City Council reached a memorandum of understanding in March that ended the council’s challenge to the Federal Aviation Administration’s decision approving the projects. Immediately after reaching the agreement, RIAC applied for a FAA grant for the safety improvements and a LOI, or letter of intent, that would enable the agency to bond for the runway extension with the guarantee that a portion of it – RIAC is hopeful of 75 percent funding – would be repaid by the FAA. Word on those requests is not expected until later this month.

But the higher than projected costs for the runway safety areas on Runway 16-34 raises questions over the plan to convert about seven acres of Buckeye Brook wetlands to the east and relocate the Airport and Post Road intersection on the west to meet FAA safety standards. Those standards call for a 1,000-foot safety area at both ends of the runway. However, because of space limitations, RIAC is planning to install EMAS, emergency material arresting systems, at the end of the runway; collapsing cement blocks designed to stop an aircraft that has overshot the runway. The use of EMAS reduces the space needed to meet the standard to about 600 feet.

Frazier did not say how much more the safety areas would cost, but when asked if the amount is about $100 million, he said that would qualify as considerable.

How could planners be so far off on their estimates?

Frazier explained the process of cost estimating a project is somewhat inverted as it starts with an environmental impact study, not with an engineering design. Further, as compared to the runway extension, the runway safety area is a more complex project. It involves the removal of a hangar, the acquisition of 10 businesses and a single residence, relocation of the intersection to the north in the vicinity of the Ann & Hope entrance and the filling of the wetlands.

As a result of the higher than projected estimates, Frazier said RIAC is not proceeding at this point with acquisition of the businesses and the residence. But that doesn’t mean people will be left dangling.

He said RIAC and the FAA are “collaborating” on both of the projects, adding that one of the provisions sought by the council in the agreement is a timeline for the projects.

“We’re on target with the time line,” he said, “so people’s lives won’t have to be put on hold.” Answers could be coming by the middle of this month.

Assuming the funding is approved, RIAC CEO Kevin Dillon, who left Rhode Island last month to take a similar post at the Connecticut Aviation Authority, had been hopeful of starting construction next year. Work would begin on the Post Road end of Runway 16-34, followed by the runway extension to 5-23 and then finally the safety areas on the Buckeye Brook end of the shorter runway.

Frazier cautioned, “I don’t want to create any false sense of concern.”

He said the objective is “to make the best decision possible as soon as possible.”

The runway extension, the source of more than a decade of controversy, would lengthen Runway 5-23 from 7,166 to 8,700 feet, giving airlines the capability of offering non-stop service to the West Coast. The extension to the south end of the runway would require the looping of Main Avenue. Also as part of the project, Winslow Park softball and soccer fields would be relocated. Where those fields will end up is in the process of being discussed. The Knight Campus of CCRI has been proposed, although at this point it appears the college could not accommodate all the existing fields. RIAC has designated land in the Lakeshore Drive neighborhood that it cleared of homes for the fields if an alternative site or sites can’t be found. Under the terms of the agreement, the city is to select an alternate location by September or the fields will go to the Lakeshore Drive area.

Camille Vella-Wilkinson, Ward 3 councilwoman, confirmed a recent meeting with CCRI, the city and RIAC about the fields, but did not have anything to report as of Tuesday.