Contra Costa County, CA Outdoor Lighting: Dark Sky Rules (2026)

Contra Costa County does not have a single comprehensive dark-sky ordinance, but outdoor lighting in unincorporated areas is regulated through several mechanisms. Ordinance Code Title 8 (Zoning) requires that lighting for commercial, industrial, and multi-family uses be shielded and directed downward to minimize glare and light trespass onto adjacent properties. California Energy Code Title 24, Part 6, regulates outdoor lighting efficiency, maximum lumens per site, and automatic shut-off controls. CEQA review for new development typically requires lighting plans demonstrating dark-sky-friendly design, especially for properties near Mt. Diablo State Park, Morgan Territory, Los Vaqueros Watershed, or other sensitive open-space areas. Residential lighting is less strictly regulated but must not create a nuisance for neighbors (Ord. Code standards on nuisance lighting). Mt. Diablo State Park and the Lindsay Wildlife Experience have advocated for reduced light pollution in surrounding unincorporated communities (Clayton, Morgan Territory, Blackhawk). Full cutoff (full-shielded) fixtures that emit no direct light above the horizontal plane are the industry best practice and are increasingly required in discretionary project approvals. Unshielded floodlights that illuminate neighboring parcels can be cited as a zoning or nuisance violation. New agricultural lighting (greenhouses) may have specific shielding and curfew requirements.