A bill making it easier for shoreline property owners to put up retaining walls and other structures is advancing through the Honolulu City Council, although some members said they want more information before they’ll give it final approval.

Bill 17 was approved unanimously by the Council Zoning and Planning Committee on Thursday, with members Breene Harimoto and Ron Menor voicing reservations.

Harimoto said he’s bothered by objections raised by the city Department of Planning and Permitting, Sierra Club Hawaii and others that the bill is too permissive and could allow structures that accelerate the decline of Oahu’s beaches.

"I would like to hear from outside experts on this matter," Harimoto said. "I think one of our primary charges is to be sure that we preserve and protect the environment."

Menor said he wants "more careful legal analysis" of the bill after questions were raised that it could be pre-empted by state coastal laws. He said he’s also troubled by testimony warning that the bill "might lead to unintended negative environmental consequences that we’re not aware of."

Council Chairman Ernie Martin, who introduced the bill, said he wants to help owners of shoreline properties along Kaneohe Bay, Ewa Beach and other coastal zones who are struggling to control the erosion of their properties. Those landowners now need to spend tens of thousands of dollars going through a lengthy and cumbersome environmental review to obtain a variance from the Department of Planning and Permitting.

The bill would allow, through a permit, retaining walls and other "minor shoreline structures" deemed to have no environmental impacts, he said.

Only retaining walls set far enough back from the shoreline could be considered, while sea walls would still require a variance, Martin said.

But Deputy DPP Director Art Challacombe said what may be set back from the ocean now could be shoreline in 10 years due to sea-level rise and erosion. Retaining walls are not minor structures and sometimes divert water into neighboring properties, he said.