The board overseeing Hawaii’s largest-ever, multibillion-dollar public works project grew this week by four members — but city and state leaders continue to debate whether that increase was even legal.

Wesley Machida, Kalbert Young, Kamani Kuala‘au and Tobias “Toby” Martin all joined the Honolulu Authority for Rapid Transportation board during its meeting Monday. Their addition comes as part of Act 1 — the state’s latest, $2.5 billion rail-funding bailout.

Gov. David Ige and legislative leaders hope their presence — even as nonvoting members — will bring added scrutiny and build public confidence in rail following three years of startling cost increases.

The expansion boosts the HART board to 14 from 10 seats. However, Honolulu’s City Charter states the board can have only 10 seats.

That puts the city’s mayor, Kirk Caldwell, in a delicate position trying to solve what he sees as a legal conflict while not appearing to reject further rail scrutiny.

“It is my concern that the legislative appointments provided for in Act 1 conflict with the Revised Charter … in violation of the state Constitution,” Caldwell told City Council members in an Oct. 16 letter. He suggested they try to fix the problem by putting a charter amendment before voters next year that adjusts the board’s membership.

The mayor still has those concerns, but he “welcomed the addition of the four new members because they will provide different perspectives and insights to help guide the rail project,” Caldwell spokesman Jesse Broder Van Dyke said in a follow-up statement Wednesday.

Corporation Counsel Donna Leong echoed Caldwell’s concerns at a Nov. 1 Council hearing. The board expansion could leave rail vulnerable to lawsuits by its opponents, she said.

On Monday, Leong met with other members of the HART board in closed session before the four new members took their seats, according to a HART spokesman.

State leaders maintain the board expansion is on solid ground.

“We did review those questions, and obviously anyone can file a lawsuit, but we do believe the bill as signed into law is defensible,” Ige said at a Sept. 5 news conference on Act 1.

“I think the Legislature did a good job of establishing a record that explained what was the rationale for asking what they wanted,” Attorney General Douglas Chin added during the news conference. “That includes … having four appointees sit as nonvoting members.”

In its first week the board expansion also had unintended effects. With 14 members the increased quorum requirements delayed several key votes on rail.

Two voting members, Terri Fujii and John Henry Felix, had to leave Monday’s meeting early. Thus, the board could not vote on a nearly $18 million change order for design and engineering work, according to HART spokesman Bill Brennan.

Furthermore, the board did not discuss as planned efforts to eventually extend rail to the University of Hawaii at Manoa under the city’s “locally preferred alternative.”

The board scheduled a new meeting Friday to revisit those issues.

“When you have change orders, you don’t want the contractors thinking, ‘Hey, we’re going to get strung out by HART because they can’t get the required approvals in a timely manner,’” board Vice Chairman Terrence Lee said Friday. “This may happen more frequently” until voters pass a charter amendment to fix the problem, he said.

He added, however, that he thinks the new members will “add a lot to the quality of deliberations that we engage in.”

House Speaker Scott Saiki, who helped craft Act 1, said legislators did consider that adding four new board members might pose logistical challenges. However, “at this point the city needs to take every step to build public confidence in the rail project,” Saiki added.

Star-Advertiser reporter Gordon Y.K. Pang contributed to this story.