Mixing Zone Policy

 Proposed Amendment to the Water Quality Control Plan for the North Coast Region (Basin Plan) to Implement a Mixing Zone Policy


The 2007-2010 Triennial Review Priority List included the development of a “Mixing Zone Policy” (Rank 12 of 29 issues).  As described in the Initial “Staff Report for the 2007 Triennial Review” (June 18, 2007), this “policy would be focused only on pollutant limits intended to protect municipal supply (nitrates, chlorine break-down products, etc).  Examples of where limitations would be set, might include: a mixing zone established at a wastewater outfall that would be of limited size and would not be located near any existing or potential drinking water intake.” 

The development of a “Mixing Zones Policy for Human Health Related Constituents”, or any Basin Plan amendment, requires the compilation of substantial background information to inform the environmental impacts and alternatives analysis required for a Basin Plan amendment.  Regional Water Board planning staff resources were not available to develop this background information.  Therefore, Regional Water Board staff and staff representing Publicly Owned Treatment Works (POTW) developed a “Scope of Work” that described the process by which the interested municipal discharge community would developed some of the necessary background information needed by Regional Water Board staff to pursue this proposed Basin Plan amendment. 

The report, titled “Evaluation of a Mixing Zone Policy for Health-Related Constituents” (January 11, 2011), was submitted to the Regional Water Board on January 27, 2011.  The report contains:

  • A description of the existing regulations and policies.
  • Basin Plan Amendment Alternatives
  • Environmental Analysis
  • References
  • Appendices
This report, and the associated Appendix A is available below

The report will be used to provide background information in the development of Regional Water Board staff’s project description for a proposed Basin Plan amendment to consider a “Mixing Zones Policy for Human Health Related Constituents”.  

Available Documents

Mailing List

We encourage users interested in the Mixing Zone Policy and other basin planning issues to subscribe to the Basin Planning email list .

If you would like to be added to the hard-copy mailing list, please contact Lisa Bernard at 707-576-2677 or
5550 Skylane Blvd, Suite A,
Santa Rosa, CA 95403.

Contact Us

For information, comments, or questions concerning the Mixing Zone Policy please contact:

Lisa Bernard

  (Page last updated 7/5/23)