Teamwork in Trenchless Projects: The Martha Lake Gateway Experience: Fid-Bau Portal

Teamwork in Trenchless Projects: The Martha Lake Gateway Experience

Schey, Eric / Nelson, Ben / Kucker, Michael / Pease, Matthew / Richart, Paul

The I-5 / 164th Martha Lake Gateway Sewer and Water Improvement project, completed in November of 2014, provides a new gravity sewer system and water transmission main for the Alderwood Water and Wastewater District (AWWD) in the vicinity of Interstate 5 (I-5) and 164th Street SW just north of Seattle, Washington. An earlier study performed for the District determined that the most desirable method of providing sewer service to the sewer basin would require a 532-foot trenchless crossing under I-5 as well as a 200-foot crossing of 164th Street Sw. This paper examines the trenchless crossings of I-5 and 164th Street SW with respect to the geotechnical conditions and explores how these conditions influenced the design of the crossings as well as the execution of the contract once construction was underway. The first section focuses on project history and design of the crossings and discusses how the soil conditions directed the trenchless evaluation and selection of the trenchless method for each crossing. The second section focuses on the geotechnical baseline report (GBR) and examines how specific baselines were determined through a collaborative process between the District and design consultants. This process allowed the District to apportion the various risks between themselves and the trenchless contractor. The final section discusses the execution of both trenchless crossings and examines how various elements of the GBR were utilized during construction.