National City P-1 Trunk Sewer Upsizing

Aerial shot of utility workers on the P-1 Trunk Sewer Upsizing project in National City, CA

National City P-1 Trunk Sewer Upsizing

Successful Collaboration Led to Limited Community and Environmental Impact  

In National City, California, community growth and increased wastewater flow volumes taxed an existing half-mile P1 Sewer pipeline. The new 12-inch polyvinyl chloride pipeline is designed to replace approximately 1,490 feet of an existing 8-inch vitrified clay pipeline. Sizing of the new pipe followed projections from the City’s sewer system master plan to accommodate future development. 

Before design, our team conducted biological and cultural assessments to determine potential impacts that could present challenges. The project maintains a habitat for San Diego ambrosia, a federally endangered species, migrating birds and common animals found throughout San Diego, including snakes, squirrels and raccoons.

To avoid potential disruption, the chosen alignment follows the existing sewer path, which required access to Sweetwater Union High School’s athletic fields, trenchless crossings under a former Duck Pond landfill, then under 30th Street, and on to National City Boulevard. When the pipeline reached 30th Street, the team turned to trenchless jack-and-bore installation methods to bypass utilities and avoid potential challenges from the landfill. The new pipeline also improves access for maintenance crews, replacing 48-inch maintenance holes with 60-inch ones. 

The team worked closely alongside the City, residents and property owners as construction passed through each private property, including the school. Working together, the team determined the required care for each site and restored them to their original status upon project completion.

Aerial shot of utility workers on the P-1 Trunk Sewer Upsizing project in National City, CA
City of National City

National City, CA
United States


Project of the Year Award (2024)
Utilities, $2-5 Million Category
American Public Works Association, San Diego and Imperial Counties Chapter