A State Implementation Plan (SIP) is a United States state plan for complying with the federal Clean Air Act, administered by the Environmental Protection Agency. The SIP consists of narrative, rules, technical documentation, and agreements that an individual state will use to clean up polluted areas.
In Ohio between the dates of 1970 and 1977 a rule in the Clean Air Act required a reduction in the measured SO2 emitted by coal fired power plants into the air. The State Implementation Plan to decrease the SO2 emitted by such plants was to increase the height of the smokestacks on the plants. The result was that the SO2 was carried in the wind out of the state and there was a reduction in the measured SO2. These kinds of exploits in the Clean Air Act were solved in the 1977 revision of the Clean Air Act when the NSPS were introduced. NSPS measures the concentration and amount of pollution put into the air, thus making a taller smoke stack useless under the new standard.