Modoc County

The Modoc County Planning and Building Department issues all ADU permits in unincorporated areas (the great majority of the county outside Alturas city limits). Practical permitting frictions: federal-land adjacency (most private parcels are checkerboarded with or adjacent to Forest Service / BLM land - access easements, fire-defensible-space coordination with federal fire crews, and federal Endangered Species Act consultation may apply on parcels near sensitive habitat), severe winter snow loads (design loads of 50-90 psf depending on elevation), short construction window, septic/well dependence with deep groundwater requiring purpose-drilled wells in the South Warner / Surprise Valley areas, and very limited contractor availability (Alturas-based contractors are few; most projects rely on contractors traveling from Klamath Falls OR or Reno NV).

Process overview: Standard ministerial 60-day review per Sec. 65852.2(b) for compliant ADU applications. The department's small staff (single-digit FTE) typically reviews quickly when applications are complete. Septic/well parcels require Environmental Health review (well permit, percolation test, septic system design). Parcels in the State Responsibility Area along the Warner Mountains and Devils Garden plateau require Chapter 7A ignition-resistant construction. Federal-adjacent parcels may require coordination with the Modoc National Forest or BLM Surprise Field Office on access easements, fire defensible space, and (in the small set of parcels near sage-grouse priority habitat) federal habitat consultation under the Endangered Species Act / candidate-species framework.

Impact fees: SB 13 fee waivers apply to ADUs under 750 sqft (no impact fees). Larger ADUs are charged proportionally to the primary dwelling. School district fees apply to ADUs over 500 sqft per Education Code Sec. 17620 (Modoc Joint USD covers most of the county; Tulelake Basin JUSD overlaps the western county).

The Modoc County Assessor's Office maintains parcel-level assessment records for the entire county. ADU additions on unincorporated parcels are captured as improvements via shared permit data with the Planning and 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. Modoc County's small assessment roll (under 11,000 parcels including significant unimproved high-desert ranching parcels) means assessor response times are typically fast. Federal land (Modoc NF, Lava Beds NM, Modoc NWR, BLM, Clear Lake NWR) generates no assessment roll because federal land is not taxable.

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. Williamson Act ranching contracts under Cal. Gov't Code Sec. 51200 cover significant Surprise Valley and Big Valley ranching parcels.

Modoc County overlays of consequence: extensive federal land coverage (Modoc National Forest, Lava Beds National Monument, Modoc National Wildlife Refuge, BLM Surprise Resource Area, Clear Lake National Wildlife Refuge - together covering the majority of the county and outside county zoning entirely); CAL FIRE State Responsibility Area along Warner Mountains and Devils Garden (Very High and High FHSZ); FEMA SFHA along the Pit River, North Fork Pit River, South Fork Pit River, Goose Lake (intermittent), and Surprise Valley playas; greater sage-grouse priority habitat overlay across South Warner / Surprise Valley sagebrush-steppe (federal candidate-species consultation potential); Williamson Act ranching contracts in Surprise Valley and Big Valley; and the seasonally-flooded Tule Lake / Lower Klamath agricultural-lease parcels in the western corner straddling the Siskiyou County line.

• Modoc National Forest / Lava Beds National Monument / Modoc NWR / BLM Surprise / Clear Lake NWR
• CAL FIRE State Responsibility Area / Warner Mountains and Devils Garden FHSZ
• FEMA SFHA - Pit River, Goose Lake, Surprise Valley playas
• Greater sage-grouse priority habitat (South Warner / Surprise Valley)
• Williamson Act ranching contracts - Surprise Valley and Big Valley