Board approves 38-lot Diablo Canyon preliminary plat with two-thirds protected as open space

The Coconino County Board of Supervisors unanimously adopted Resolution 2025-53 on Sept. 23, 2025, approving a preliminary plat for a 38-lot subdivision on roughly 334.89 acres about 1.5 miles northeast of New Mormon Lake.

The project, dubbed the Diablo Canyon subdivision, clusters 38 lots on the eastern edge of the property and designates nearly two-thirds of the acreage as protected open space with public trails, water features and preserved meadows. The action implements incentives in the county subdivision ordinance that allow density bonuses in exchange for conservation-focused designs.

Jess McNeely, deputy director of the Community Development Department, described the site and staff's analysis: utilities will include APS electricity; the development will be a hold-water subdivision (lots will not be on a community water system) and all lots will use on-site wastewater systems. The proposal includes private internal roads and annexation into the Mormon Lake Fire District for emergency services. McNeely said the design protects environmentally sensitive features such as large trees, rock outcroppings and several stock tanks used by wildlife and that Arizona Game and Fish offered recommended mitigations, including wildlife-friendly fencing and construction-season restrictions.

McNeely said the applicant used the county's cluster-conservation incentives to reduce lot sizes to a minimum of 2.5 acres and secure the open-space dedication; without clustering the g-zone density would have yielded 33 lots instead of 38. The planning and zoning commission reviewed the proposal and forwarded a unanimous recommendation of approval to the board.

Supervisor Judy B. Horstman praised the conservation design and said she hopes to see the clustered approach used more widely. Supervisor Tammy Ontiveros, who said she reviewed the packet and the commission's findings, moved to adopt the resolution; Supervisor Horstman seconded the motion. The board voted unanimously to approve the preliminary plat.

The vote approves the preliminary plat only; the developer must return with a final plat in substantial conformance with the approved preliminary design. Staff noted the subdivision will be subject to specific conditions listed in Resolution 2025-53, including protection of environmentally sensitive features, wildlife best-practices recommended by Arizona Game and Fish, and requirements for emergency access and private road maintenance.

Project proponents told the board they agree with staff recommendations and conditions and said they would proceed with final-plat work. The county noted public access trails are planned through the protected open space and that staff received 13 letters of support and a small number of attendees at the required citizen participation meeting.

Next steps: the applicant will prepare a final plat and satisfy the resolution's conditions before the board's final-plat review.