An aerial map of the project area with color lines showing existing and new sewer lines.

Alvarado Trunk Sewer Phase IV

Built in the mid-1960s, the Alvarado Trunk Sewer is in need of replacement and upsizing to meet the demand of the area’s growing population. The existing sewer alignment is located within residential and commercial areas, as well as across highways and environmentally sensitive areas, making access for maintenance and construction difficult. Aiming to increase capacity and improve access, the City of San Diego undertook its largest trunk sewer project—an approximately $45 million initiative to upsize and relocate the sewer away from residences and businesses and minimize community impacts.

What We Did

To accommodate future peak flows of up to 25 million gallons per day (MGD), the project team evaluated alternatives to relocate the existing pipeline, which ranges between 21 and 30 inches in diameter, and designed the selected pipeline alignment that ranges between 27 and 42 inches in diameter for a length of 3.5 miles. The project also includes sliplining the existing trunk sewer along segments where existing lateral flows need to be diverted to the new trunk sewer.

Segments of the sewer will be constructed through Environmentally Sensitive Areas and within the highly congested Alvarado Road, a key access corridor to San Diego State University and the Alvarado Hospital. The project also includes nine trenchless drives, including microtunneling and jack and bore segments, to cross highways, as well as large storm drain culverts, permitting, and easement acquisitions.

Key Features

  • 3.5-mile sewer replacement upgrades 50-year-old pipeline and increases system capacity.
  • Hydraulic analyses ensure proper functionality of pipeline realignment.
  • 1.5-mile sliplined section eliminates need for trenching to reduce construction disruption.
  • Plumbing cleanouts provide access for maintaining connecting lines.


  • Increased sewer system capacity improves reliability.
  • Easement acquisitions for up to 20 parcels.
  • Relocated majority of the trunk sewer to public right-of-way to minimize community impacts.
  • Trenchless drives designed to minimize permitting and to mitigate environmental impacts.


City of San Diego


San Diego, Calif.


Design, Environmental Studies, Permitting, Construction Services

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