Brightwater Conveyance System

(King and Snohomish Counties, WA)  Landau Associates was a primary team member on the CDM team, which was selected by King County to provide geotechnical services for the Brightwater Conveyance System. This regional wastewater system is one of the largest public works infrastructure projects undertaken in the Northwest since the 1960s and carries treated wastewater from the Brightwater plant to Point Wells and into Puget Sound. The conveyance system consists of a deep-bore tunneled pipeline system and one of the world’s deepest municipal outfalls. Routing of these structures occurs through terrain of complex topography and geology, and under densely populated areas. The pipeline alignment involves 14 miles of deep tunnels (up to 440ft below the ground surface and at considerable depth below the groundwater table).

The team provided geotechnical services for all aspects of the conveyance system, including final alignment and marine outfall. Landau Associates participated in the field investigation and geotechnical laboratory testing for the tunnel and pipeline alignments, led the geotechnical design team for the three microtunneling and trench sections, led the geotechnical design element for the marine outfall to 30 percent design, and provided technical support and design review for the design-build portion of the project.  

The outfall pipeline is one of the deepest municipal marine outfalls in the world and included both a nearshore 84-inch diameter steel pipe segment and twin 63-inch diameter HDPE pipelines extending about 5,000 ft offshore in water depths of more than 600 ft. Landau Associates supported King County in the evaluation and design review of the design-build contract for the marine outfall. Review services included providing geotechnical review of competing design-build proposals, and geotechnical review of the design by the selected design-build team. In addition to reviewing the overall design, the review focused on the Geotechnical Data Report, Geotechnical Interpretive Report, Geotechnical Baseline Report, and Geotechnical Reconciliation Report documents prepared by the design-build team.

The Brightwater Marine Outfall Design-Build Project has received a dozen national and regional awards including the American Public Works Association-Washington Project of the Year in the category of "Environment – $25-$75 million," an Honor Award from the Seattle Section of the American Society of Civil Engineers for Local Outstanding Civil Engineering Achievement, and was recognized by McGraw-Hill Construction with regional and national "Best of the Best" awards for civil/public works projects.