Planners recommend capped density on 103-acre Thunder Mountain site amid slope and drainage constraints

Planner Reynolds presented the Thunder Mountain rezoning, a county case involving approximately 103 acres in the Seymour area that the applicant seeks to rezone to planned residential.

Reynolds said staff is recommending PR up to 2 dwelling units per acre (the applicant requested up to 3), subject to conditions including: no clearing or grading until the development plan is approved by the planning commission, and that land disturbance in the hillside‑protection (HP) area not exceed the slope‑analysis recommended disturbance budget unless the planning commission grants an exception. Reynolds emphasized the site’s steep topography: substantial portions of the property fall within the HP area, with tens of acres in the 25–40% slope bands and a significant area above 40% slope.

Staff explained the recommendation reflects an intent to protect hillside resources and limit erosion or drainage impacts; Reynolds noted some of the substandard nearby side streets could require improvements should development materially increase trips. Conditions discussed include temporary cul‑de‑sacs versus t‑turnarounds and requests for right‑of‑way to enable safer future street connections. Staff recommended postponement for certain related rezonings but presented the site‑specific conditions and the rationale behind the density cap.

Reynolds said the slope analysis suggests a recommended disturbance allowance that is smaller than portions of the HP area and that the planning commission should require development‑plan review before grading. Commissioners asked clarifying questions about past court involvement on a prior withdrawn concept plan and about which portions of the parcel were included in the current request; Reynolds confirmed this application is not the same as a withdrawn 2022 concept plan.