Slopes and walls are fundamental components of geotechnical engineering, addressing the critical need to manage earth materials and maintain stable ground conditions. In Surrey, this category encompasses the analysis, design, and remediation of both natural and engineered slopes, as well as the structural systems used to retain soil. The importance of these services cannot be overstated in a region experiencing rapid urban expansion, where development often pushes into areas with challenging topography. From safeguarding hillside properties against landslides to creating level building pads for new subdivisions, effective slope and wall solutions are essential for public safety and infrastructure longevity.
Surrey’s geological setting presents specific challenges that demand specialized local expertise. Much of the city is underlain by complex glacial and interglacial deposits from the Fraser Glaciation, including dense lodgement till, glaciomarine silts, and outwash sands. The South Surrey area, in particular, features rolling terrain with steep ravines descending toward the Nicomekl and Serpentine Rivers. These sensitive, low-permeability silts and clays can be prone to instability when saturated, making thorough slope stability analysis a non-negotiable first step for any project near a ravine or riverbank.
All slope and wall designs in Surrey must strictly adhere to the British Columbia Building Code (BCBC) and the City of Surrey’s Engineering Design Criteria and Subdivision Bylaw. These regulations mandate a geotechnical investigation for any permanent cut or fill exceeding 1.2 meters in height. The design of retaining structures typically follows the limit states design principles of the Canadian Foundation Engineering Manual (CFEM), with seismic considerations governed by the national seismic hazard maps. For walls over a certain height or those supporting critical infrastructure, the city requires a Professional Engineer’s sealed design, ensuring robust retaining wall design that accounts for both static and dynamic loading conditions.
This category of work is integral to a diverse range of projects across Surrey. Residential developments on sloping lots frequently require engineered cut and fill slopes or segmental block walls to create usable yard areas. Major transportation corridors, such as the ongoing expansions of Highway 15 and the Fraser Highway, rely on mechanically stabilized earth (MSE) walls and soil nail walls to support roadway embankments. Commercial and industrial developments in the Campbell Heights area often need tall, structural retaining systems to maximize flat floor space. For deep excavations or walls with restricted access, specialized active/passive anchor design provides a secure and efficient solution by tying the wall back into competent soil or rock.
A slope stability analysis evaluates the safety factor of an existing or proposed slope against a rotational or translational failure, without necessarily including a structural element. Retaining wall design is the structural engineering process of dimensioning a wall to provide external stability against sliding, overturning, and bearing failure, while also structurally reinforcing it to resist bending and shear forces. The analysis often informs the magnitude of lateral earth pressure the wall must be designed to withstand.
The City of Surrey requires a geotechnical investigation and a Professional Engineer’s sealed design for any permanent engineered cut or fill slope over 1.2 meters in height, and for all retaining walls supporting a surcharge or exceeding 1.2 meters in exposed height. This report must assess soil stratigraphy, groundwater conditions, and seismic liquefaction potential, providing the design parameters needed to meet the safety requirements of the BC Building Code.
Common causes include prolonged heavy rainfall that saturates the near-surface silty soils, reducing their suction and shear strength, and uncontrolled surface runoff that erodes the slope toe. Undercutting of slopes by stream meandering in ravines and poor construction practices, such as un-engineered fill placement or cutting a slope too steeply without support, are also frequent triggers. The local glaciomarine deposits are particularly susceptible to instability when disturbed.
The choice depends on site constraints, wall height, and soil conditions. Gravity walls, including MSE and large block systems, rely on their mass to resist earth pressures and require a wider excavation footprint. Anchored walls use high-strength steel tendons grouted into stable ground behind the failure plane, making them ideal for tight spaces, tall single-lift walls, or when supporting deep excavations where a wide excavation is not feasible.