Sonoma Water has 79 miles of pipelines, also known as aqueducts, which deliver drinking water throughout portions of Sonoma and Marin counties. Made from concrete cylinder metallic pipe, our oldest aqueducts were installed in 1957; and range from 16-inches to 54-inches in diameter.

Our pipelines deliver naturally filtered, safe and reliable drinking water to more than 600,000 residents in Sonoma and Marin counties. It is vital that we maintain our assets and continue to provide a high level of service to our community.

What is cathodic protection?

Cathodic protection is a technique used to control corrosion of something metallic, such as a metal pipe, by causing it to act as the cathode of an electro-chemical reaction.  To help prevent the pipes from corroding, sacrificial anodes are buried next to the pipe, which are designed to corrode instead of the pipe.  Installing new anodes will extend the life of the existing pipelines by up to 50 years.

Notice of Preparation of Initial Study

The Proposed Project would allow Sonoma Water to update the existing, aging cathodic protection system. Sonoma Water’s aqueducts are currently protected by a galvanic cathodic protection system (galvanic system). The galvanic system includes buried anodes that are attached to the aqueduct. The anodes provide a material that corrodes more readily than the aqueduct, so the corrosive materials in the environment around the aqueduct degrade the anodes rather than the aqueduct. This system also includes cathodic test stations, which consist of a wire lead from the aqueduct up to a test station mounted above the ground surface that allows staff to test the level of cathodic protection without excavating to the aqueduct. The anodes in the current galvanic cathodic protection system are aging and, therefore, depleted and no longer provide adequate protection against corrosion. Failing to replace the existing anodes could result in corrosion and failure of sections of the aqueducts in the future.

The objective of the proposed project is to extend the service lives of the Santa Rosa and Cotati aqueducts by installing an updated cathodic protection system, which will protect the aqueducts from corrosion.

View Notice of Preparation of Initial Study (PDF)

Upcoming Corrosion Prevention Projects

Over the course of the next several years Sonoma Water will undertake a project to ensure the reliability of our water transmission system.

The planned project will update the cathodic protection system that is currently installed on the Santa Rosa and Cotati aqueducts (see map below).

Santa Rosa and Cotati Aqueducts