HDPE Geogrid on the Low Level Road Project for the City of North Vancouver and Port Metro Vancouver

This paper will focus on the diversity of retaining walls, steepened slopes, and wall transition
sections as utilized on this 2.6 km road realignment project. With retaining heights rising to 14
metres, this project was a significant undertaking for both the City of North Vancouver (CNV)
and Port Metro Vancouver (PMV).

For this project, the unique challenges associated with retaining wall design in steeply sloping
terrain included:

• Raise and realign the new road section.
• Adding rail lines at the down-slope section of the project by way of a grade separation.
• Improving existing slope stability, and quickly completing the task in 16 months.

This was achieved with 23 000 m2 of SierraScape® and 4 000 m2 of Sierra® Retaining System.
The versatility of these systems during site installation by the field crew was a unique advantage
when selecting a wall system to quickly conform to irregular/steep terrain in a timely
construction fashion.

The paper focuses on technical aspects of the design that include:

• A rectangular section and trapezoidal section (where slope stability restraints existed).
• False abutment (pile supported) walls for bridge design at Neptune/Cargill Overpass
• Wall inclinations ranging from vertical to 1H: 10V, and slopes leaning back at 3H: 8V.
• Seismic design analysis for 475-yr and 975-yr return periods.
• Geotechnical conditions, generally comprised of very dense gravelly sand soils of glacial origin.

This project also has the distinction to be the “First Transportation Project to be awarded the
Envision Platinum Award for Sustainable Infrastructure”.