Alpine County

Alpine County Building/Planning Department issues all ADU permits in the county because every parcel is unincorporated. Practical permitting frictions are not regulatory but environmental: very high fire severity zones (CAL FIRE State Responsibility Area covers nearly the entire county), Lake Tahoe Basin TRPA jurisdiction along the northern edge near Hope Valley/Kirkwood corridors (TRPA review can add discretionary layers for Tahoe Basin parcels), Sierra snow loads requiring 200+ psf structural design at elevation, septic/well constraints with limited public sewer (only Markleeville and Bear Valley have any community service districts), and short summer build seasons (typical practical window is May to October).

Process overview: Standard ministerial 60-day review per Sec. 65852.2(b) for compliant ADU applications. Tahoe Basin parcels (north of Carson Pass) trigger Tahoe Regional Planning Agency (TRPA) review on top of county review, which is discretionary and materially extends timelines. Parcels in the very high fire severity zone require Chapter 7A ignition-resistant construction documentation and may trigger fire department defensible-space conditions of approval.

Impact fees: SB 13 fee waivers apply to ADUs under 750 sqft (no impact fees). Larger ADUs are charged proportionally to the primary dwelling. The county does not assess school district fees on ADUs at the county level (school fees flow through the local school district, Alpine USD).

The Alpine County Assessor's Office maintains parcel-level assessment records for the entire county. ADU additions are captured as improvements to the host parcel via shared permit data with the building department. California Proposition 13 caps base-year valuation increases at 2 percent per year on the existing structure; new improvement value (the ADU) is added as a separate line item assessed at fair market value at completion. Alpine County's small assessment roll (under 4,000 parcels including unimproved Forest Service inholdings) means assessor response times are typically fast.

Assessment policy: ADU improvement value is added on the next regular revaluation cycle following completion, not at permit issuance. Per Prop 13, the ADU's value is taxed at 1 percent of fair market value at completion (plus voter-approved local rates), while the existing structure remains at its base-year value plus 2 percent annual cap. Conversion ADUs (within existing structure) typically generate smaller incremental assessments than new detached ADUs.

Alpine County overlays of consequence: CAL FIRE Very High Fire Hazard Severity Zone (FHSZ) covers nearly the entire county; Tahoe Regional Planning Agency (TRPA) jurisdiction over the Lake Tahoe Basin on the northern edge; FEMA SFHA along the East Fork Carson, Markleeville Creek, and West Walker drainages; and the California Wildland-Urban Interface (WUI) Chapter 7A applies broadly. The county is almost entirely within the Humboldt-Toiyabe and Eldorado National Forests, so most parcel boundaries abut federal land - relevant for fire setbacks and access-easement issues but not for county zoning per se.

• CAL FIRE State Responsibility Area / Very High FHSZ
• Tahoe Regional Planning Agency (TRPA) jurisdiction — TRPA jurisdiction overlays a small portion of northern Alpine County; the bulk of the county (Markleeville south, Bear Valley, Hermit Valley) is outside TRPA.
• FEMA SFHA - Carson and Walker River drainages
• California Scenic Highway System - SR-89 / SR-4 / SR-88