Corrosion Protection

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.

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).

Construction to Start on Petaluma Boulevard for Corrosion Protection Project for Water Supply Aqueduct

A construction project on Petaluma Boulevard to protect the one of the main drinking water pipelines that serves Petaluma will get underway the week of Aug. 27, and will cause some traffic delays, lane closures, and restricted pedestrian access in some areas along the city’s main thoroughfare.

Work at five sites along Petaluma Boulevard will take place Monday through Friday beginning the week of Aug. 27, 2018 starting near East Washington Street and proceeding south to Petaluma Boulevard South at Mountain View Avenue. This phase of construction is expected to last approximately three weeks.

Sonoma Water is performing maintenance on one of its main water delivery pipelines, the Petaluma Aqueduct, which travels through downtown Petaluma along Petaluma Boulevard. Work will take place from Monday through Friday, between 8 a.m. and 5 p.m. at various locations along Petaluma Boulevard.

Construction on the pipeline may interfere with normal traffic and pedestrian patterns in the roadway near homes and businesses. At each site there may be lane closures, but traffic will remain open in both directions. Construction will only take place Monday through Friday during normal working hours.

The Petaluma Aqueduct is one of the pipelines that helps deliver drinking water to more than 600,000 residents in Sonoma and Marin counties, including the City of Petaluma. The current project will update the corrosion prevention system currently installed on the aqueduct and helps prevent the metal portion of the pipeline from corroding.

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.

Santa Rosa and Cotati Aqueducts

Questions? Please contact Hannah Salafia at or 707-524-6435.