Officials are working on plans to make Nu'uanu Dam safer after a report listed it among nearly two dozen in the state with structural or functional deficiencies.

Edwin Matsuda, state dam safety engineer, said the Board of Water Supply has asked the state to help it develop short- and long-term plans for improvement.

The board owns Nu'uanu Dam, which, if it fails, could send a flood through a highly populated area, engineers have said.

Difficulties in monitoring seepage at the earthen dam, which is overgrown with trees and brush, are among the problems, engineers have said. Board officials have been meeting with Matsuda and Eric Hirano, chief engineer for the state Department of Land and Natural Resources, to address the problems.

The planning follows a report by the American Society of Civil Engineers that gave Hawai'i a "D" on dam safety.

An Oct. 23 Advertiser article on the report also elicited response from several of the owners of 22 "high-hazard" dams in the state, Matsuda said.

"Pretty much everyone has been responsive," Matsuda said of the owners.

Yesterday, Board of Water Supply officials addressed concerns about Nu'uanu Dam with City Council members Rod Tam and Ann Kobayashi during an informational meeting of the council's Public Works and Economic Development Committee.

"We're going to have to do something about those trees growing on the top of the dam," Barry Usagawa of the Board of Water Supply said.

Dam safety engineers have been recommending since 1978 that vegetation around the dam be removed so that inspectors can keep an eye on leakage.

Roots of a row of trees allowed to grow atop the dam may pose a hazard to the dam's integrity, engineers have warned.

In a 1999 report, one inspector estimated that it would cost $400,000 to clear the crest and upstream and downstream slopes of Nu'uanu Dam.

Some vegetation was recently removed, Usagawa said, but contractors may be needed to take care of parts of the dam.

He and Board of Water Supply acting manager and chief engineer Donna Kiyosaki said they hope to have a plan of attack for removing the vegetation and dealing with the trees within two months.

Kiyosaki told Tam and Kobayashi that although the Board of Water Supply "does not use or need the dam," the city agency is working with the state Department of Land and Natural Resources to make sure the dam is safe, and to that end the water level at the dam is kept at a fraction of capacity.

Wahiawa Dam is also getting some attention, Matsuda said.

He said Dole Food Co., which operates Wahiawa Dam on Lake Wilson, has been working to update emergency-action plans.

In addition, Matsuda said, $300,000 in state money has been allocated but not yet released to study ways to mitigate flooding downstream of the Wahiawa reservoir.

Otake Camp, downstream of the reservoir, was evacuated as a precaution against flooding three times in the past eight years, most recently in early October, civil defense officials said.

Reach Karen Blakeman at kblakeman@honoluluadvertiser.com.