Earth Retention

Location: Astoria, OR

Project Partner: P&C Construction

Challenge: Installation of temporary shoring in extremely unstable geologic conditions.

Overview: Condon-Johnson was contracted to install temporary shoring at the Clatsop Community College in Astoria, OR. The site was located on top of an abandoned basalt rock quarry, creating one of the most unique and difficult conditions to shore. Condon-Johnson quickly realized that no traditional shoring system would be feasible in this location due to the loose rubble and presence of 15 foot+ boulders.

Results: Working directly with the engineer, Condon-Johnson developed the concept for a shoring system consisting of pairs of micropiles acting as the main lateral support structural elements of the shoring wall. Multiple rows of tiebacks were drilled between the micropile pairs to support the excavation. A mesh reinforced shotcrete facing was installed and acted as the basement wall form. This project showcased Condon-Johnson’s ability to work closely with engineers to create a constructible design in extremely challenging conditions.