Western Terminus Replacement Project

Project Details


  • 42-inch HDPE treated effluent
  • 1,200-foot wetland crossing

Geotechnical Conditions

  • Young Bay Mud
  • High groundwater


  • Accelerated design timeline
  • Environmental restrictions
  • Minimizing impacts to residents

Project Overview

As a subconsultant to Brown and Caldwell, Bennett Trenchless Engineers provided trenchless design services for the HDD installation of 1,200 feet of 42-inch HDPE treated effluent pipeline under an environmentally sensitive area in San Lorenzo, CA. Challenges included the large diameter and length of the HDD crossing, and the presence of soft Young Bay Mud soils. The more severe challenges of the project included a significantly accelerated design timeline, work area constraints, numerous environmental restrictions, a very tight construction window, maintaining access to a bike path that ran through the construction zone, minimizing disruption to nearby residents, and managing a high risk of hydrofracture.

In addition, the project had a significantly accelerated design timeline; construction was completed within one year of receiving the Notice to Proceed for design. Bennett Trenchless provided preliminary and final design services, specifications, hydrofracture and settlement risk evaluations, cost and schedule estimates, and submittal review assistance.