Pipeline Maintenance Completed in Southeast Napa

August  05, 2012

Napa Sanitation District has completed a project to reduce wet weather sewer flows in an area of southwest Napa. This area south of downtown Napa, bounded by Madrona Street to the north, Hemlock Street to the south, South Jefferson Street to the east and South Seymour Street to the west, is a portion of a larger area that the District refers to as “Basin L”. Basin L was identified in the District’s Collection System Master Plan as an area with significant inflow and infiltration.

Inflow and infiltration (I&I) is water that flows into sewer pipes from groundwater and stormwater. Groundwater (infiltration) seeps into sewer pipes through holes, cracks, joint failures, and faulty connections. Stormwater (inflow) rapidly flows into sewers via roof drain downspouts, foundation drains, storm drain cross-connections, and through holes in manhole covers. Most I&I is caused by aging infrastructure that needs maintenance or replacement.

The Basin L Pipeline Rehabilitation Project included sewer main pipe in roadways and lower lateral lines that run from the sewer main to the property line, which were rehabilitated utilizing a method called pipe bursting. Pipe bursting is a trenchless method of pipe replacement, where a breaking device called an expander head is pulled through the defective pipeline from a launching pit. As it travels through the pipeline toward the receiving pit, the expander head breaks the pipe into many small pieces, pushing the pieces into the surrounding soil. New pipe is attached to the back of the expander head, replacing the line immediately.

This project was completed on time and within budget, and will reduce the incidence of sewer overflows during winter storms.

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