An attorney for a hui that opposes a city plan to develop a portion of Waimanalo Bay Beach Park said Saturday that he plans further legal action, including an injunction to stop the project and equitable relief to get it returned to its pre-construction condition.

Tim Vandeveer, who filed a lawsuit Thursday in District Court, made his remarks during a press conference at the beach park, which was attended by some 140 protesters and project opponents.

The city wants to clear about 4 acres of the park’s 74-acre forest, known as Sherwood Forest, to make room for a multipurpose field, a playground and an 11-stall parking lot, Andrew Pereira, spokesman for Mayor Kirk Caldwell, said Saturday. The current $1.43 million project represents a compromise from the city’s original 2012 plan to develop a $32 million sports complex and 470-stall parking lot on the site, Pereira said.

“Mayor Caldwell respects the right of protesters to express their views, but he’s going to continue with Phase I of the project, which the community fought for and approved,” Pereira said. “He has listened and he has already compromised. Those who support the project deserve as much attention as those who are opposed to it.”

But the lawsuit Vandeveer filed alleges the city failed to adhere to federal land use controls, violated federal and state historic preservation law, conducted an inadequate environmental assessment and used a flawed permit approval process that distorted the primary and special purposes of the beach park.

“It’s really a process to go through and consider the true impact on the natural resources, the cultural and historical resources, and that’s what we are asking the city to do — not just in this process, but all across the state,” Vandeveer said.

Beatriz Cantelmo, Amnesty International Honolulu Chapter co-director, also called the city out Saturday for how it shut down a Thursday protest, which led to the arrest of 28 protesters who were blocking police and construction workers.

“Aside from the arrests, which are bad enough, this is probably the first time that we have documentation of law enforcement using an LRAD 100X sonic weapon device,” Cantelmo said. “The manufacturer says that it can be used as a microphone but this is also a military weapon. This was used in Cuba, in Russia, this has been used in war. This has been used to torture people.”

Cantelmo said she doesn’t think the device was used as a weapon Thursday. However, she said its frequencies can cause nausea, headaches and dizziness. It also can harm hearing and cause brain damage, she added.

“The mere presence has no place in Hawaii in a nonviolent protest,” she said.

Pereira denied the city used excessive force Thursday. So far, there have been no reports that the LRAD, which was used Thursday as a public address speaker, was deployed in any other way.

“You can judge by what happened that there was cooperation and collaboration on both sides,” he said.

Protests, which have been ongoing for months, intensified after a Sept. 18 meeting, hosted by Caldwell, where contractors were told to resume construction. Protesters have been camping out since Monday at the site, which on Saturday had established a learning center, keiki area and place where voters could register.

Maureen Harnisch, who opposes the project, disputes Caldwell’s version that “many in the community” want construction to proceed at Waimanalo Bay Beach Park. She said early pushback was limited because Waimanalo and surrounding communities were left out of critical stages of the project’s planning process.

Upon closer examination of the city’s plans, some opponents fear the project could lead to more development of rural Waimanalo and cause overwhelming increases in traffic and tourism. They say the project intrudes into what they consider a “culturally significant area” that contains roughly 90 sets of human burials estimated to be up to 1,500 years old. Caldwell has said the project would not disturb the iwi.

Some opponents also have questioned the city’s decision to move forward at Sherwood Forest when nearby Albert H. Azevedo Field, which serves the same purpose, needs maintenance.

Pereira said an issue with the clay at the Albert H. Azevedo Field has prevented field repairs. But Pereira said other aspects of deferred maintenance there eventually would be addressed.

Since 2015, the city has made 512 improvements to 156 of its 299 parks islandwide. It’s also recently completed two large capital improvement projects in Waimanalo, including removal of a pavilion and extensive renovation of a district park gym.

But these city efforts have “come too little, too late” for some critics and are irrelevant for others, who don’t feel the city should have jurisdiction over the historic coastal forest.

Kalani Kalima, a 44-year-old Waimanalo resident who was arrested for obstruction Thursday, said he and others have reached the point where “it’s enough.”

“Because if if we don’t do it, our kids gonna have to continue to fight, my grandkids gonna have to continue to fight,” Kalima said. “My motto is if there’s a struggle to be had, let it be in my time, not in my son’s time.”