Williamson Creek Wastewater Interceptor
Austin, TX

Williamson Creek Wastewater Interceptor | Austin, TX

Austin Water has acknowledged the need to provide additional capacity to convey wastewater flows in the current Williamson Creek Interceptor.  Dating back to 1963, the 36-inch and 42-inch segments of the existing interceptor are at capacity during heavy rain events. Coupled with unprecedented growth in the Williamson Creek Basin, upgrading capacity of this 50-year old facility is critical in the City’s ongoing program to eliminate SSO from the system and provide consistent uninterrupted service to residents.  CAS is the prime design firm for this $42 Million project, currently projected as an 18,000-foot, 72-inch diameter tunneled pipeline.

The recommended solution, as presented in the Final Preliminary Engineering Report, includes a tunneled application for the interceptor, design for 27 cutover main connections from the adjacent collection system, and 3,000 feet of rehabilitation for existing interceptor that must continue in service, and abandonment and/or removal of all other facilities.  The entire length of the existing interceptor is in South/Central Austin in a highly visible, environmentally sensitive riparian and wetland environment.

As the prime consultant, CAS has completed preliminary engineering services and is transitoning into final design. In determining the recommended solution, CAS and our team partners: performed review of historic project documents; multi-sensor condition assessment, hydraulic analysis and flow projections of the existing interceptor and cutover mains; evaluation of construction methods; route analysis/final alignment determination including consideration for 27 connections; review of existing land uses; determination of easement requirements; evaluation of limitations and efficacy of keeping sections of the existing interceptor in service; preliminary utility investigation and geotechnical/subsurface assessment; determined site constraints; performed an environmental constraints mapping/evaluation/report leading to inventory of special requirements and detailing environmental impact of chosen route; identified endangered species, critical environmental features and water quality zones; developed a project phasing plan and construction schedule; and prepared a cost estimate and implementation schedule.

CAS anticipates design to commence in June 2018.

Project Cost: $42M (Est.)

Owner: City of Austin