The proposed Bristol Ridge project sits above Halls Hill Road.

An island environmental group is fighting a proposed residential subdivision at the crest of Halls Hill, saying the development could destabilize the slope and endanger homes along Blakely Harbor.

Island Keepers has appealed city approval of a plan by developer Kelly Samson to divide two lots on Halls Hill Road into nine residential parcels.

The appeal of the Bristol Ridge short plat goes before the city hearing examiner on Thursday at 10 a.m.

Residents named on the appeal declined comment, referring inquiries to Island Keepers’ notice of appeal, which was filed with the city in November.

The appeal characterizes residential development on Halls Hill’s south slope, which overlooks Blakely Harbor, as an “extraordinary geological hazard” that allegedly violates numerous land use regulations.

Recent plant removal and other activities on city and Samson-owned properties have “aggravated the erosion and slide conditions” along Halls Hill’s south slope, according to the appeal.

Testimony from a geotechnical expert and state Department of Natural Resources staff citing unstable soils are noted. Recent slides along Halls Hill Road and the closure of portions of Blakely Hill Road, on the hill’s west side, are also mentioned.

Additional development could cause “potentially fatal” erosion along Seaborn Road, where numerous homes line the bank of the harbor.

“I don’t think the appeal of the city’s short plat approval is about the short plat at all,” Samson said Tuesday. “It is really about the public road. It would seem to me more productive if all of the energy, time and resource being spent on the appeal process was directed towards actually cooperating on fixing the road.”

Halls Hill Road was closed by the City Council last year after some south-end neighbors raised concerns about the hill’s stability, especially after heavy rains washed soil onto Seaborn. City engineers deemed the hill safe and the road was reopened a few days later.

The city conceded that the hillside above the road, which is owned by the city, had not been properly replanted after a road improvement project. City staff vowed to plant the area as had been proscribed by the planning department.

Island Keepers, which formed last spring, has rallied support for dock restrictions in the harbor and other environmental issues. In July, the group hired a geotechnical engineer to assess the stability of Halls Hill Road and the impact of Samson’s proposed development.

The engineer’s report said the city had not adequately investigated the link between the development and erosion.