SPECIAL NOTICE:  All locations within the City of Napa Water System are meeting the regulatory standard for Disinfection Byproducts in Drinking Water.  The particular byproducts at issue are Trihalomethanes (THMs).  If you have previously received a special notice in the mail regarding the presence of THMs caused by the reaction of chlorine with organic matter in potable water, the Water Division is pleased to report that the running annual averages for all sites are in compliance since April 2016, below the new regulatory threshold of 80 parts per billion (ppb).

This issue has led to inquiries to the Water Division for more information.  Water Division staff have spoken at length with many customers about the complex nature of the new water quality regulation (called DBPR-II, or Stage II of the Disinfection Byproduct Rule), the presence of THMs, the causes of THMs, and steps the Water Division has been taking to prevent their formation.  No specific corrective actions are needed by customers who receive a DBPR-II notice.  There is no need to boil water.

The Water Division held a public meeting on May 6, 2015, to discuss water system operations and preventative measures and answer questions.  Dr. Bruce Macler, a drinking water toxicology specialist from EPA Region IX, was on hand along with City staff.  Click to view a recording of this meeting.

FAQs, notifications with maps of affected areas, and other correspondence:


State Water Resources Control Board Original Citation-February 27, 2015

City of Napa Response to Original Citation-April 10, 2015

City of Napa Response to July 2015 Citation-September 8, 2015

City of Napa Response to October 2015 Citation-December 14, 2015

City of Napa Response to January 2016 Citation-February 25, 2016