Modesto, CA

North Valley Regional Recycled Water

City of Modesto


The North Valley Regional Recycled Water Program (NVRRWP) will convey treated recycled water from the City of Modesto to the Delta-Mendota Canal for agricultural use by the Del Puerto Water District and for wildlife refuge use by United States Bureau of Reclamation. The ability to use recycled water provides the City of Modesto with an additional water resource for the municipal supply. In addition to open-cut sections, the recycled water pipeline project required trenchless undercrossings at the San Joaquin River and Caltrans Highway 33/​Railroad. The undercrossings ranged from 250 to over 2,600 feet (76 to 792 m) in length, with an internal diameter of 42 inches (1,070 mm).

Fast Facts
  • Undercrossings up to 2,600 feet (792 m) long
  • 42-inch (1,070 mm) internal diameter microtunnels
  • 19 borings drilled for trenchless undercrossings

Scope of Work

Delve Underground, as part of a team, provided Owner Advisor services, tunnel methods evaluation, geotechnical investigations, trenchless design, and design-build engineering services for the City of Modesto’s North Valley Regional Recycled Water Program. In addition, the firm supported the 100% design of the Caltrans Highway 33/​Railroad crossing for the permit application with Caltrans.

Challenges & Innovations

The San Joaquin River undercrossing design included the preparation of pipe stress and pipe pullback calculations, a hydrofracture analysis, and preparation of the undercrossing plan and profile in order to satisfy requirements of the permit application.

To accelerate permit acquisitions with the Central Valley Flood Control District, Delve Underground performed the geotechnical investigations at both crossings and provided 60% design for the trenchless San Joaquin River crossing.