By Leon Worden/SCVNEWS.com

Unincorporated Santa Clarita Valley residents living within the Castaic, San Francisquito Canyon and other community standards districts are in for some subtle changes – at least after the sun goes down.

On Tuesday the Los Angeles County Board of Supervisors will consider a plan that would establish a rural outdoor lighting overlay zone – i.e., control light pollution – throughout the unincorporated Santa Clarita and Antelope valleys and the Santa Monica Mountains.

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Supervisors Michael D. Antonovich and Zev Yaroslavsky called for the plan in December 2010, noting that inconsistencies have developed over the years in regulating light pollution in the different unincorporated areas.

Eight community standards districts have regulations for outdoor lighting – Castaic, San Franciscquito Canyon, Leona Valley, Acton, Santa Monica Mountains North Area, Juniper Hills, Southeast Antelope Valley, Elizabeth Lake and Lake Hughes – to control glare from street lights and private property owners’ floodlights. Other unincorporated areas are unregulated.

The new lighting plan would remove the regulations from the community standards district documents and put all affected areas under the new ordinance, which the Regional Planning Commission approved Nov. 9.

“Residents of the county’s unincorporated rural areas … value dark night skies that are unimpeded by light pollution,” Antonovich and Yaroslavsky said in their 2010 motion. “Dark night skies are one of the many qualities that set rural areas apart from urban and suburban communities.”

The piecemeal approach to curbing light pollution through a patchwork of regulations via community standards districts “has been problematic for rural areas that are not currently in a CSD, as there are no standards to preserve and enhance dark night skies in those areas.”

Their request for a “baseline set of objective, measurable standards” resulted in a plan that tiers off of the state’s definitions of lighting zones. Zone 1 is dark illumination, for state parks and wildlife preserves; Zone 2, low illumination for rural areas as defined by the 2000 Census; Zone 3, medium illumination for urban areas; and Zone 4, high illumination areas.

The new county ordinance would align with state definitions using the 2000 Census. As a result, 40 specific areas on the urban fringe that are currently considered “urban” (Zone 3) – locally, the mouths of San Francisquito, Bouquet and Mint canyons, and a small part of Sand Canyon – would be reclassified as rural (Zone 2) for the purpose of outdoor lighting (see map above).

See below for rural outdoor lighting guidelines from the Los Angeles County Department of Regional Planning (October 2011).