Main Street Bridge Water Main Replacement Project

Project Details


  • 16-inch HDPE water pipeline
  • 400-foot crossing of Pilarcitos Creek

Geotechnical Conditions

  • Alternating layers of stiff fat clay and medium dense to dense sand with clay and clayey sand
  • High groundwater


  • Permeable soils
  • Mitigate impact to existing utilities
  • Work area constraints

Project Overview

BTE served as a trenchless design sub-consultant to Erler & Kalinowski, Inc. (EKI) on the design of a water main replacement project in Half Moon Bay, CA.  The existing line crossed above Pilarcitos Creek, attached to the deteriorating Main Street Bridge.  CCWD relocated the 16-inch pipeline under the creek, downstream of the bridge, prior to the bridge being renovated.  During preliminary design both microtunneling and HDD were evaluated as feasible replacement method for the 400-foot creek crossing, however HDD was chosen as the trenchless construction method.  Project challenges included high permeability sands and direct groundwater recharge from the creek, and constricted work areas in the developed urban setting of downtown Half Moon Bay.