Publication Detail

Proposed Mobil Source Offset Provisions in California May Negatively Impact Air Quality



Suggested Citation:
Guensler, Randall L. (1990) Proposed Mobil Source Offset Provisions in California May Negatively Impact Air Quality. Environs Law & Policy Journal 4 (1), 7 - 12

Sources of air pollutant emissions can be generally separated into four categories: stationary sources, area sources, mobile sources, and indirect sources.
  • (1) Stationary sources are typically industrial operations such as utility boilers, petroleum refinery equipment, surface coating (painting) operations, graphic art printers, etc. Generally, stationary source emissions come from "point sources," or single emission points that require a local agency permit to operate.
  • (2) Area sources are usually diffuse emission sources, such as sewage treatment plants, or point sources that are too small to be individually tracked by the local agency (e.g. residential fireplaces or water heaters).
  • (3) Mobile source emissions are from automobiles, heavy duty vehicles, aircraft, railroads, construction equipment, or similar sources.
  • (4) An indirect source is a facility that attracts mobile source activity. Thus, an indirect source is responsible for the trips, mileage, and emissions that mobile sources produce when transporting people and goods to and from the facility. Common indirect sources include: shopping malls, business parks, industrial parks, airports, residential developments, video rental outlets, and local convenience stores.
Local air pollution control districts are responsible for developing Air Quality Management Plans (AQMPs) designed to bring their local air basin into attainment with National Ambient Air Quality Standards (NAAQS). Based upon the AQMPs, the local districts and the State promulgate a State Implementation Plan (SIP) in accordance with the federal Clean Air Act.

In California, the SIP consists of one set of regulations from each of the 41 local air pollution control districts within the state. Each local regulation is designed to achieve a specific emission reduction. The total estimated emission reductions resulting from regulations in each air basin are projected to yield local attainment of the NAAQS.

New Source Review (NSR) programs are a major component of the SIP for each local district. NSR regulations are designed to mitigate emissions from new facilities (where "new" is relative to the adoption date of the local NSR regulation) and from the modification of existing operations. Between 1979 and 1982, most districts in California adopted permit regulations that contained NSR provisions. These regulations were based upon the California model rule adopted in 1979 by the California Air Resources Board. California NSR requirements are more stringent than the federal NSR requirements.

Under NSR, when a facility increases emissions beyond the threshold value established by the regulation (typically ranging from 50 pounds per day to 250 pounds per day), the facility is required to apply Best Available Control Technology (BACT) to their process. Depending upon the magnitude of the emission increase, NSR may also require the facility to provide emission offsets that mitigate the emission increases. Emission offsets are certified reductions of emissions at the same or another facility. Under NSR, offsets are usually provided at a ratio of greater than 1:1. Thus, when new sources are permitted, offset requirements will theoretically reduce the net emissions in the basin by some percentage.