Former U.S. Rep. Colleen Hanabusa is resigning from the Honolulu Authority for Rapid Transportation board of directors effective at the end of this month, citing personal reasons, according to board Vice Chair Kika Bukoski.

The other board members on Friday adopted a resolution honoring Hanabusa for her contributions to the $10 billion Honolulu rail project, and rail authority CEO Lori Kahikina said she recommended Mayor Rick Blangiardi designate Oct. 1 as “Colleen Hanabusa Day” in her honor.

The departure of Hanabusa, who is also former president of the state Senate, represents a major loss of political acumen and institutional memory for the rail board. Hanabusa was also an outspoken board member who demonstrated she was willing to publicly challenge the HART authority leadership.

Hanabusa often asked pointed, well-informed questions of staff at public meetings of HART and very publicly butted heads with Kahikina over the resignation of a key staff member last year.

Kahikina later accused Hanabusa of workplace bullying, and Hanabusa asked the city to investigate that complaint.

City Managing Director Mike Formby, who previously served as Hanabusa’s chief of staff in Congress, was to handle that investigation. City Communications Director Scott Humber said in a written statement Friday “the Managing Director looked at and considered the totality of the circumstances and handled the matter through discussions with both sides.” He added that “the matter is considered closed.”

Hanabusa was first appointed to the rail board in mid-2015, and served there until fall of 2016 when she won a special election to serve in Congress.

She left Congress to run for governor in 2018, but lost that race in the Democratic primary to then-Gov. David Ige. She went on to lobby for HART at the Legislature in 2021, and was awarded an 18-month contract worth $216,000 to continue that work on behalf of the rail authority’s board that spring.

A month later she reversed course and declined the lobbying contract as some questioned the arrangement. Blangiardi instead appointed Hanabusa that May to an unpaid seat on the rail authority board, and she was elected chair of the board by the other members. She has held that post ever since.

Hanabusa used the HART meetings to dig deeply into areas where she suspected contractors or landowners might be taking advantage of the HART, including Hawaiian Electric Co.

She also continued her lobbying efforts on behalf of the project, with HART board member Anthony Aalto crediting Hanabusa with the successful push to have additional hotel room tax revenue earmarked for rail in 2021. That extra tax revenue will contribute more than $500 million to help pay for the current project.

Hanabusa has missed several board meetings in the past few months, which is unusual for her.

“Colleen’s leadership, experience, and steady guidance have been invaluable to the progress of this critical project for our city,” Blangiardi said in a written statement Friday. “On behalf of the people of Honolulu, I thank her for her commitment and the many contributions she has made to moving Skyline forward.”

“As we look ahead, we will work with the community  to fill this important position and ensure that the Board continues to benefit from strong, capable leadership,” Blangiardi wrote.

Bukoski said Hanabusa “has made tremendous contributions to this board and to this project, and to HART in general, and I’m going to miss her on the board.”

Kahikina told the board Friday that despite the differences she has had with Hanabusa, “I can honestly say I have learned quite a bit from her.”