E-20 Wurzbach Parkway: Segment 1

Project Details

Open-Shield Methods

  • 54-in and 36-in FRP gravity sewer pipeline
  • 2,900 feet of trenchless in two crossings
  • 72″ and 54″ steel casing

Geotechnical Conditions

  • Primarily hard clay and marlstone
  • Some very loose to loose poorly-graded gravel transitioning to loose to dense clayey gravel with sand
  • Groundwater encountered in some locations


  • Mixed face conditions in some locations
  • Risk of over-excavation and creation of voids

Project Overview

BTE served as trenchless design sub-consultant to Kimley-Horn on the design and construction of SAWS’ E-20 sewer replacement project.  The project provides increased capacity in the E-20 sewer segment through the installation of over 13,000’ of new 54” and 36” fiberglass gravity sewer.  BTE provided trenchless design services for over 2,900’ of the pipeline to be constructed using open-shield methods.  The trenchless reaches involve installation of 72” and 54” steel casing or tunnel liner plate for containment of the gravity sewer pipe.  Ground conditions along the majority of the alignment consist of stiff to hard clay soils and marlstone bedrock which favor hand mining or open-shield pipejacking methods.  At the crossing of Salado Creek, near the downstream end of the pipeline, saturated sandy and gravelly conditions lead to the recommendation of watertight microtunneling methods.  BTE provided review of the anticipated ground conditions and provided recommendations for appropriate trenchless methods at each crossing location.