Bundled Recycled Water and Sewer Main Pipelines Tunnel Under Napa River

November  19, 2013

2,250 feet of bundled recycled water and sewer main pipeline made its way under the Napa River on November 19. Construction crews had been at work for more than a month drilling the tunnel for the two pipelines, a 24” recycled water pipeline and an 8” sewer main. The larger pipe will carry recycled water to Stanly Ranch and Los Carneros Water District, while the sewer main provides sanitary sewer service for future development at Stanly Ranch. 


According to the drilling contractor, this project is one of the longest drills for a bundled pipe project in the Northern California area.  Where the tunnel passes under the Napa River, it’s 36 feet below the river bottom. Special directional equipment guides the drill as it navigates underground. Once the drill reaches the opposite end of the tunnel, it’s connected to the pipe and the drill pulls it back through the tunnel.

The construction contractor used Horizontal Directional Drilling (HDD) technology to create the 42” diameter tunnel for the two pipelines. HDD can save time and money when installing utilities under roads, rivers, buildings or other obstacles. Most of the ground surface remains undisturbed during the process, as the drilling follows a “u” shape underground from the point of origin to the end point. In this case, the process allowed the pipeline to cross underneath the Napa River without creating an impact to the river.

This project is being funded and constructed by the Stanly Ranch Vineyards LLC, with oversight from the Napa Sanitation District.  Los Carneros Water District (LCWD) joined the project in March 2013, when its members voted to fund the oversizing of the recycled water pipeline under the Napa River to the Stanly Ranch area, so that the LCWD area could be served by recycled water from the District as well. LCWD and Stanly Ranch Vineyards LLC shared the cost of this $1.7 million project.

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