Important Terms & Concepts

Open Space

Open space is defined as any parcel or area of land or water essentially unimproved and set aside, designated, dedicated, or reserved for public or private use or enjoyment.

California Register of Historical Resources

The California Register of Historical Resources (California Register) is an authoritative listing and guide to be used by state and local agencies, private groups, and citizens in identifying the existing historical resources of the state. By definition, the California Register includes all "properties formally determined eligible for, or listed in, the National Register of Historic Places," and certain specified State Historical Landmarks.

The California Register also includes resources that are listed following procedures and criteria adopted by the State Historical Resources Commission, as well as resources that are nominated by an application and listed after a public hearing process. The minimum age criterion for the California Register is 50 years. Properties less than 50 years old may be eligible for listing on the California Register "if it can be demonstrated that sufficient time has passed to understand its historical importance" (California Code of Regulations, Sections 4850.1 through 4852).

Air Quality Terms

The South Coast Air Quality Management District, or SCAQMD, is the regional agency responsible for implementing state and federal laws that mandate the improvement of air quality in the South Coast Air Basin. The South Coast Air Basin is a 6,600 square mile area bounded by the Pacific Ocean on the west and south, and the San Gabriel, San Bernardino, and San Jacinto mountains on the north and east. The Basin includes all of Orange County and non-desert portions of Los Angeles, Riverside, and San Bernardino counties.


The topography and climate of Southern California combine to make the Basin an area of high air pollution potential. During the summer months, a warm air mass frequently descends over the cool, moist marine layer produced by the interaction between the ocean's surface and the lowest layer of the atmosphere. The warm upper layer forms a cup over the cool marine layer, which prevents pollution from dispersing upward. This inversion allows pollutants to accumulate within the lower layer. Light winds during the summer further limit ventilation.


Due to the low average wind speeds in the summer and a persistent daytime temperature inversion, emissions of hydrocarbons and oxides of nitrogen have an opportunity to combine with sunlight in a complex series of reactions. These reactions produce a photochemical oxidant, more commonly known as smog. Since the Los Angeles region experiences more days of sunlight than any other major urban area in the United States except Phoenix, the smog potential in the region is higher than in most other major metropolitan areas in the country.