Our Story

The Napa Sanitation District (NSD), located in the Napa Valley, provides wastewater collection, treatment and disposal services to the residents and businesses in the City of Napa and surrounding unincorporated areas of Napa County. NSD has been serving the public since it was organized under the California Health and Safety Code in November 1945.

Napa Sanitation District (NSD) is an independent special district. Special districts are a form of local government created by a local community to meet a specific need, in this case, wastewater treatment and disposal. NSD is governed by a five-member Board of Directors, comprising three elected officials from the City of Napa (2) and Napa County (1) and two public appointees.

NSD Mission Statement:

To collect, treat, beneficially reuse, and dispose of wastewater in an effective and economical manner that respects the environment, maintains the public's health and meets or exceeds all local, state and Federal regulations. 

History of the Napa Sanitation District 

Before the Napa Sanitation District began serving the community in 1945, untreated sewage and stormwater drained together to the Napa River. The river became unsafe for swimming and fish die-offs were common in the summer. In 1945, residents voted to form the Napa Sanitation District and change this legacy of water pollution. The District’s first treatment system focused on removal of solid materials, ranging from rags and trash to smaller floating particles. The original treatment plant was built on Imola Avenue next to the Napa River, just north of the present day Maxwell Bridge.  

Growing population, expanding treatment 

As the population of Napa grew and wastewater treatment technology improved, the District continued to upgrade and expand its facilities. Throughout the 1960’s and into the early 1970’s the District completed the separation of sewer and stormwater pipes, greatly reducing sewage overflows during winter storms. Treatment ponds were added at the site of the current Soscol Water Recycling Facility near the airport. These ponds store the wastewater while microorganisms living in them feed on the waste.

Soscol Water Recycling Facility 

In the late 1970’s, the District moved most of its treatment operations to the current site of the Soscol Water Recycling Facility, along the Napa River just south of the Highway 29 bridge. This plant, which was a joint project with the American Canyon County Water District, offered primary and secondary treatment. The recycled water produced was used to irrigate golf courses.

Wastewater treatment at Soscol Water Recycling Facility 

Today, the Soscol Water Recycling Facility (SWRF) is a state-of-the-art wastewater treatment and water recycling plant. All treatment operations were consolidated at this plant during the late 1990’s, and the treatment facilities at the Imola plant were demolished.

Wastewater that enters the Soscol Water Recycling Facility from the City of Napa and surrounding unincorporated areas goes through a complex series of steps to remove contaminants. These steps include removal of solid, floating and dissolved materials, removal of waste by microorganisms, followed by filtration and chlorination. The water receives tertiary treatment, making it safe for discharge to the Napa River or for reuse as recycled water in irrigation. Recycled water is now used to irrgate golf courses, vineyards, parks and pastureland.