Board approves Diablo Canyon preliminary plat: 38 lots, 2/3 of site preserved as open space

The Coconino County Board of Supervisors on Sept. 23 adopted Resolution 2025‑53 approving the preliminary plat for the Diablo Canyon subdivision: a 38‑lot cluster layout on roughly 334.89 acres located about 1.5 miles northeast of Mormon Lake. The planning and zoning commission had unanimously recommended approval; the board’s vote was unanimous.

Deputy Director of Community Development Jess McNeely summarized the proposal: the 335‑acre property would be divided into 38 clustered residential lots with roughly 202 acres set aside as permanent open space. The design relies on conservation‑oriented clustering incentives in the county subdivision ordinance that allow smaller lots in exchange for significant protected open space.

Key details provided by staff and the applicant - Lot and density: The subdivision uses clustering incentives to reduce lot sizes down to as small as 2.5 acres while preserving approximately two‑thirds of the land as open space. The applicant received a density bonus to increase lots from a baseline entitlement of 33 to 38 lots by providing additional open space and using privately maintained internal roads. - Access and utilities: Primary and emergency access are provided by four service roads; internal roads will be privately maintained. Electricity is planned through APS; the development is a “hold water” subdivision with individual lots using on‑site wastewater (septic) systems. Water hauling arrangements were noted in staff materials. - Environmental and wildlife protections: The design preserves meadow and stock‑tank ponds and protects environmentally sensitive features with building envelopes and road design. Staff said the applicant coordinated with Arizona Game and Fish, which recommended construction‑period measures, minimization of invasive species introduction, and wildlife‑friendly fencing. Trails within the open space will be publicly accessible, the staff report said.

Applicant Thomas Lampeau of Norris Design told the board the applicants accept staff conditions and support the commission’s unanimous recommendation. Supervisors praised the conservation‑focused design during brief comments.

Why this matters The approved preliminary plat advances a conservation‑oriented model of rural subdivision that preserves large contiguous open space, protects wildlife water sources and provides clustered housing in a region that is otherwise prone to fragmented lot‑by‑lot development. The final plat and construction plans must substantially conform to the approved preliminary plat and return to county processes for final approval and implementation steps.

Procedural note and next steps The board approved the preliminary plat by motion (Supervisor Ontiveros moved; Supervisor Horstman seconded) and adopted Resolution 2025‑53. A final plat and related infrastructure or construction permits will be required before building can begin; staff will monitor compliance with the approved conditions.

Provenance - topicintro: transcript excerpt where the preliminary plat item is introduced and handed to staff (s=4156.395–s=4203.1553). - topicfinish: transcript excerpt recording the motion, second and unanimous board approval (s=5304.33–s=5375.625).