An excavator and a bulldozer were set on fire near the entrance of Waimanalo Bay Beach Park, also known as Sherwoods and Sherwood Forest, where preliminary work for a much- protested city project is underway.

The city began clearing ironwood trees and brush to build a playground and sports field in April despite strong opposition from the Waimanalo community.

“Whether you oppose this project or support it, we must all agree this type of criminal activity is unacceptable and hurts everyone. Anyone who is found to have done these illegal and destructive acts will be prosecuted to the fullest extent of the law,” Mayor Kirk Caldwell said in a written statement.

Police said unknown persons set fire to the equipment at 10:35 p.m. Wednes­day. Police have opened a first-degree arson investigation. No arrests have been made.

The Honolulu Fire Department estimated damage at about $250,000, the city said. The city said prior to this that “several individuals have threatened, intimidated and unlawfully entered the construction zone.”

A group of opponents who have been sign-waving in protest at the park entrance deny any involvement.

They said there is no need to call attention to their cause through vandalism because they have already gained momentum, having collected 15,000 online signatures and 2,000 written signatures on a petition to stop the project.

“We like to have a peaceful (protest),” said Wai­ma­nalo resident Paul Kekauoha, 57, one of the sign wavers. “We can talk our heart. Now they might start blaming us, too, on this kind of craziness.”

Kukana Kama-Toth, one of the opponents’ organizers, said the subcontractor whose equipment was burned is a Waimanalo resident, and she is sympathetic to how the vandalism hurts this subcontractor’s livelihood.

“For opposing people to go over and light it on fire is tough for me,” she said. “This is throwing a wrench into our progress.”

Many beachgoers opposed the project, saying there seem to be enough parks in Waimanalo.

“They got all the other parks. Fix them up,” Jonny Hanawahine, 45, of Waimanalo said. “I think it would make more traffic.”

As for the vandalism, he said, “Lame. No look too good for the people who don’t want it.”

Justin Cordero, 26, of Makiki, a first-time visitor to the beach park, added, “It’s like a waste of money. If they build it, more people would come. Would kill the vibe.”

A city worker who asked not to be identified said not enough is being done to maintain the other city parks, and that a sliver of the cost for this project could have been used to address existing problems, including Waimanalo District Park’s Azevedo Field, which is unusable for sports.

That field is cracking because of its clay soil, making it unsafe. The city said it would cost twice as much to fix that park as it would to create the new field at the beach park.

The estimate for Phase 1, the only part of the master plan currently being pursued, is $1.43 million, and there is no budget for the rest of the improvements in the plan, the city said.

“This decision was made based on community input and desire to review the findings outlined in the Master Plan,” the city said in a written response. “Their voices are being heard, but expressing an opinion through violence will not be tolerated.”

Kama-Toth said, “Whatever political deal is happening, this is actually really huge because when you look at a community of 5,600 people and 95% are in an uproar but you continue to go through with something they’re demanding to stop, ignoring the people’s voice, there must be something bigger than a playground.”

The City Council’s Committee on Parks, Community Services and Intergovernmental Affairs is holding a special meeting on the topic at 10 a.m. Wednesday at Honolulu Hale. Public testimony will be taken.