Concerns about rockfalls, traffic and flooding were aired last night by about 100 residents who packed the 'Aina Haina Elementary School cafeteria to discuss a proposed hillside residential development.

The newly formed grassroots group 'Aina Haina Hui organized the meeting to hear developer Kent Untermann's plan to build a 15-unit housing project on the steep slope above the school. The "cluster" housing plan calls for two three-story buildings with six units in each and a three-unit building on the west side of the three-acre property between 'Aina Haina and Wai'alae Iki.

Untermann said he is willing to try to work out solutions to residents' concerns.

"We gave up the best views on the lot for the density," he said. "The bottom line is even if it's approved, it doesn't mean we will develop it. The intention of the cluster development is to create a smaller building footprint."

The decision to approve the cluster permit for Wailupe Mauka lies with the city Department of Planning and Permitting, which must approve or deny the permit request by Oct. 9. The proposed project is allowed on residential-zoned land by the city building laws. Untermann told residents that he would continue to meet with them.

The Kuli'ou'ou/Kalani Iki Neighborhood Board earlier this month said it opposes the project and sent a letter to the city outlining community concerns.

Jean Ohta, an 'Aina Haina resident, said that in 1962 a boulder crashed into an area home and killed an 8-year-old child. She reminded residents of the valley's history of homes sliding and how the city spent $6.7 million to buy a block of homes on Leighton and Ailuna streets because unstable soil caused a sewer pipe to crack under the homes.

" 'Aina Haina is notorious for flooding and unstable soil," said Charlie Palumbo, a Niu Valley resident.

Reach Suzanne Roig at sroig@honoluluadvertiser.com.