Excessive outdoor lighting alters the community character of rural areas. 

Even in Sonoma Valley and on the mountains that define Sonoma Valley, increasing development of previously vacant land has resulted in significant increases in nighttime light, which is produced primarily by upward pointing or upward reflected light from outdoor lighting. 

Light trespass is a result of “spill light” shining in undesirable locations, such as a neighbor’s backyard or bedroom window. Spill light is light cast beyond the parameters of useful light or the intended area to be lit. Typical examples include security lights or landscape lights that are not angled or shielded correctly and invade areas on a neighbor’s property that are desired to be kept darker.

Spill light shining into neighboring homes at night can disrupt sleep patterns and internal cycles in humans. In addition, disturbing the natural patterns of light and dark in adjacent habitats can disrupt many aspects of animal behaviors and life cycles, including nesting, feeding, and pollination. 
 
While other jurisdictions such as San Diego County and the City of Malibu have developed ordinances that are patterned on Dark Sky International, Sonoma County has thus far limited its mandates to a section of the Taylor/Sonoma/Mayacamas Scenic Guidelines (Code of Ordinances 26-90-120).

 
Since Diamond A is located within the boundaries defined by this ordinance, we strongly recommend adhering to the following provisions:

1. Exterior lighting shall be downward facing, fully shielded, and located at the lowest possible point to the ground to prevent glare and light pollution.
2. Light fixtures shall not be located at the periphery of the property and shall not spill over onto adjacent properties or into the night sky.
3. Luminaires shall have a maximum output of 1000 lumens per fixture.
4. Total illuminance beyond the property line created by simultaneous operation of all exterior lighting shall not exceed 1.0 lux.
5. All roadway, parking, and driveway lights shall be low profile utilizing full cut-off fixtures.
6. Flood lights are not allowed.
7. If security lighting is necessary, it shall be motion-sensor activated only.

A printable pdf of these guidelines is available here.