Deep Foundations

Location: Seattle, WA

Project Partner: Manson Construction Co.

Challenge: Installation of high capacity permanent tiebacks in sensitive material, while working over an active waterway inside a MARSEC Level 1 Controlled facility.

Overview: Condon-Johnson was contracted to install the permanent tieback anchors in a newly constructed bulkhead at the Seattle BP Fuel Terminal on the Duwamish Waterway in Seattle. Condon-Johnson was an active partner for years in the preconstruction phase of this project – providing a test program to better define soil properties, several rounds of budgeting, and constant input on the final design.

Results: Through the tireless efforts of the project team, the tiebacks were completed successfully and ahead of schedule. Additional thought and care was put into the drill spoil containment to limit contamination of the waterway. Condon-Johnson and Manson Construction worked side-by-side to develop methods of containing drill spoils and preventing any environmental issues. An added complication of the project was that the fuel terminal needed to remain operational during the construction of the new bulkhead, which forced Condon-Johnson to work within a very narrow pathway, approximately 12 feet wide between the seawall and a fence. The very narrow work area made coordination of crew and equipment paramount to complete the job safely and efficiently.

Condon-Johnson was contracted three years before the construction to perform a test program to test the feasibility of installing high capacity anchors in the soil. There was great concern about the achievable capacity in the very soft marine layers where the anchors were to be installed. The test program was a success and the data was used in the final design. The project team equipped with accurate full scale data, allowed the final anchors to be designed to the verge of geotechnical failure, which decreased project cost substantially.