Kaiser Steel Corporation operates a steel mill at Fontana, California, about 50 mi east of Los Angeles. The facility is a fully integrated steel mill with basic coke, iron and steel production processes and a full range of finishing operations. It is the only integrated mill in California. The basic coke, iron and steel processes result in the emission to the atmosphere of excessive levels of particulate air pollutants, despite the installation of various air pollution control devices. On 11 July 1974, the Corporation entered into a Consent Order with EPA-Region IX to control these emissions. The Order specified various steps to be taken by the Corporation, including process modifications and installation of air pollution control devices. The objectives of the study were to determine the status of compliance with the Consent Order and to observe sources of visible emissions to determine compliance with applicable County regulations.