Often called “Napa Valley’s Main Street,” the City of St. Helena is located in the heart of Northern California wine country, about an hour and a half from San Francisco. It has a small-town, rural charm that attracts tourists from around the world. Despite the many visitors who come to St. Helena and California’s wine country each year, the population of this small community is just over 5,400 residents.
St. Helena Masonic Hall on Main St. built in 1825. Photy by Roni Gehlke
Across the U.S., small towns and cities like St. Helena, which was incorporated in 1876, depend on infrastructure that is often as old as the cities themselves. While this may contribute to the charm of these quaint communities, with their main streets still intact and buildings listed on the National Register of Historic Places, it also means these locales are often reliant on 100-year-old sewer and water systems.
That is the issue that the City of St. Helena is currently grappling with. Many of the city’s sewer pipes are aging and need repairs or replacement altogether. Late last year, the city launched a major replacement project to rebuild a part of the downtown sewer infrastructure.
“The current project we’re working on involves about 5,000 feet or roughly one mile of sewer replacement,” said Mario Traverso, City of St. Helena Public Works Project Manager. “Some components of the original system are over 100 years old (circa 1910), and were originally built as a combined sewer.”
Traverso explained that in the 1940s, the city installed a new sewer line in the project area, but today the clay pipes are cracked, offset, and missing sections, leading to significant water intrusion and infiltration. This project involves replacing the aging sewer main pipeline, manholes, and sewer laterals.
“We are seeing excessive flows to our wastewater treatment plant, particularly during winter,” Traverso said. “In the dry season, we have about half a million gallons come through the pipes per day. That number changes to five MGD in wet weather months.”
He further explained that many of the excess flows are linked to the system’s storm drain connections to the sewer system. There are also problems with the old system geometry, with much of it being installed at 45-degree angles. The new system will use 90-degree angles.
Using 90-degree-angle sewer pipes, especially long-turn or “sweep” elbows, improves flow efficiency and complies with current plumbing standards, such as the California Plumbing Code (CPC). This code often requires sweep bends when transitioning from vertical to horizontal pipes. These pipes help ensure smoother effluent flow, which is vital for preventing clogs in older, narrower, or more complex sewage systems.
“During the 70s and 80s, many clay pipes were replaced with transite, which have not fared well,” Traverso said. “Those pipes are deteriorating worse than the earlier clay pipes.”
Transite pipes, also known as asbestos-cement (A-C) pipes, were extensively used for wastewater, storm, and water lines from the 1930s through the 1980s. They contain up to 20% asbestos, which can pose health risks if the pipes are damaged or become friable, necessitating special precautions during removal. Typically, these pipes are replaced after 50 years of service.
Broken clay sewer pipe installed in early 1900s by Roni Gehlke
The clay pipes being replaced in St. Helena’s current project will be exchanged with SDR 26 – 8-inch pipes, which are thick-walled PVC or HDPE pipes with a Standard Dimension Ratio (SDR) of 26, indicating that their outer diameter is 26 times their wall thickness. These are heavy-duty pipes primarily used for high-pressure water, sewer, and irrigation systems, designed to offer greater durability and strength than clay and transite pipes used decades ago.
Traverso mentioned that this current project will be the City’s first major sewer infrastructure upgrade in more than 30 years, marking a significant step toward modernizing its system.
In February of this year, the City of St. Helena completed construction of a membrane bioreactor facility at a cost of $18.8 million. The new Wastewater Treatment and Reclamation Plant replaces an aging plant built in 1967, which could no longer meet regulatory standards. In 2016, the city received a Cease-and-Desist Order from the state regarding its wastewater plant discharge into the Napa River. The new plant treats approximately 500,000 gallons of wastewater daily and allows for water reuse.
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