Passionate opponents of the plan to use artificial turf as the centerpiece of an athletics field overhaul at the Martha’s Vineyard Regional High school had their turn before the Oak Bluffs planning board Thursday night.

“I support this project with a properly maintained grass field,” said Richard Toole. “We need to do this without the safety of our drinking water being challenged.”

He was one of many critics who focused on the potential impacts on the water table from PFAS — known as forever chemicals because they break down slowly. The long-term effects of the chemicals are believed to be harmful to human health and still being studied.

The $11 million phase one project to renovate and realign the school playing fields, including a new track, is in its final phase of permitting after receiving approval from the Martha’s Vineyard Commission last summer. A special permit is needed from the planning board because the project lies in a water resource protection overlay district.

On Thursday, speakers lined up for two hours to urge the planning board to reject the artificial turf field and require a grass field instead.

Nearly every speaker echoed the same theme, saying the potential dangers of PFAS outweigh any benefits that a turf field would bring.

At previous hearings high school coaches, teachers and athletes all expressed the strongest support for a turf field, saying among other things that it would reduce the risk of injury.

But on Thursday many who spoke said a properly maintained grass field would provide the same benefits as artificial turf.

“We all need water . . . without it, everything else is impossible,” Scarlet Johnson said. “I believe the alternative is simple: grass.”

Ms. Johnson and others proposed that the school instead install a grass field maintained by low or no-nitrogen fertilizers, coupled with a rigorous maintenance schedule.

Jeremy Houser, a biologist and staff member who works for the Vineyard Conservation Society, noted the lack of support for the project from Island environmental groups.

“The number of environmental groups that have weighed in support of it is zero,” Mr. Houser said.An environmental advocacy group, VCS has opposed the artificial turf project at hearings and in its Conservation Almanac, a regular newsletter.

Mr. Houser took note of recent events on Nantucket, where plans to install a turf field have been halted. “Nantucket’s issues are really very similar to our own,” he said. “Despite that, the school there decided not to move forward.”

Off-Island advocates who had spoken out against PFAS during recent Oak Bluffs board of health meetings attended the hearing as well, reiterating warnings about the dangers of PFAS.

“You have heard, or will hear, that there are safe PFAS,” said Kyla Bennett, New England director for the Public Employees for Environmental Responsibility. “This is simply not true . . . There is no safe level of this carcinogen.”

The hearing continues next Thursday, when planning board members will ask questions about the project, and give high school spokesmen an opportunity to respond to comments.

The meeting begins at 6:30 p.m.