Fetters Hot Springs–Agua Caliente Sewer Upgrade: What Phase 5B Means for Sonoma Valley

FETTERS HOT SPRINGS–AGUA CALIENTE, Sonoma County — October 28, 2026. An important piece of underground infrastructure is being modernized in Sonoma Valley. The Sonoma Valley County Sanitation District is advancing a multi-year project to replace an aging trunk sewer main serving the city of Sonoma and surrounding unincorporated communities, including Fetters Hot Springs and Agua Caliente.

Where is the current phase?

The district identifies the next stage as Phase 5B, divided into two sections. The Johnson Avenue section covers approximately 562 linear feet of 24-inch sewer main from the Johnson Avenue and Lichtenberg Avenue intersection to the terminus of Johnson Avenue. The official project page anticipated a July 2026 construction start, with weekday working hours from 7 a.m. to 7 p.m., excluding holidays.

The next section, between Johnson Avenue and Las Flores Drive, is planned for construction before October 2029. Those are the district’s reported planning dates, not independent confirmation that a contractor was on site at a particular moment on October 28.

Will sewer service stop?

According to the sanitation district, construction can bring temporary traffic changes, noise and dust near the Johnson Avenue work corridor. However, its public project description says sewer service will not be affected by the planned work. Residents should use the latest project updates for current traffic conditions, because changing construction stages may change where crews and equipment are present.

Why replace the main?

The agency says the pipe being replaced is roughly 60 years old and has reached the end of its expected life. The upgrade is intended to handle normal and wet-weather wastewater flows more reliably and reduce leaks or sewer overflows that could otherwise affect creeks during heavy rain. The Johnson Avenue work is being coordinated with road restoration to avoid unnecessary repeated excavation and paving.

With this phase completed, the district expects almost 33,600 linear feet of trunk sewer main to have been replaced since the first phase in 2003. That cumulative number refers to many construction stages across Sonoma Valley, not only the Fetters neighborhood.

How to follow the work

Fetters Hot Springs and Agua Caliente residents can consult Sonoma Water’s official sewer trunk main replacement page for project maps, phase descriptions and contact information. A separate Sonoma County proposal for Donald Gap walking and cycling safety concerns nearby road access and is not the same construction project.

Source: Sonoma Water / Sonoma Valley County Sanitation District’s current Phase 5B project description, checked October 28, 2026. This article covers existing public infrastructure work, not a newly announced sewer outage.

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