Statement Submitted to Environmental Protection Agency for the Public Meeting, February 22, 1978, San Francisco Regarding Modification of Secondary Treatment Requirements

The principal technical reason for having a waiver provision for secondary treatment for municipal discharges is that for some outfall systems the dilution is so high that very good ambient water quality can be achieved with less than secondary treatment. Therefore, the criteria for a waiver of the secondary treatment requirement must give full consideration to the dilution obtained by the outfall system. In a high performance outfall diffuser, such as those used by major dischargers in California and Hawaii, initial dilutions are typically 100:1, and may range up to 1000:1 in very favorable circumstances.