Tsawwassen Springs Golf Course Expansion

Tsawwassen is a suburban community and the southernmost part of the greater Vancouver area. Located on a peninsula near Point Roberts along the Strait of Georgia, the city has a population of about 21,000 residents. Despite its modest size, Tsawwassen experiences significant visitor traffic due to the nearby Tsawwassen Ferry Terminal, Roberts Bank Superport, and several popular golf courses.

One of these destinations is Tsawwassen Springs Golf Course, which expanded its facilities in 2015. That project included additional parking supported by Allan Block retaining walls that created usable flat land for the expanded lot. For that expansion, the course owners worked with Expocrete, the producer of Allan Block products in Western Canada, and LANDTEC Consultants LTD to design the retaining wall system.

Just two years later, continued growth required another expansion and even more parking. This phase, however, presented new challenges due to site constraints that had been avoided during the original construction.

Plan

The only remaining area available for parking contained a 10-inch (250 mm) high-pressure water main that could not be relocated and had to remain accessible for future maintenance. The site designers evaluated several options and initially concluded that a cast-in-place cantilever retaining wall with a toe-forward footing would be the only design capable of positioning the wall close enough to the water main to allow room for parking.

The golf course owners were dissatisfied with this option because they wanted the new walls to visually match the Allan Block walls built during the 2015 expansion. The project team reached out to LANDTEC to review whether Allan Block products could again be used while accommodating the tight site restrictions.

With extensive experience designing Allan Block systems, LANDTEC developed a hybrid solution that could meet both structural and aesthetic requirements.

Design

LANDTEC proposed a hybrid retaining wall system combining Allan Block masonry construction with a traditional geogrid-reinforced segmental wall.

The lower two-thirds of the wall would function as a masonry cantilever structure built with Allan Block Classic units. The hollow cores and high compressive strength of the blocks allowed them to perform similarly to a cast-in-place concrete wall while maintaining the appearance of the existing retaining walls.

LANDTEC collaborated with Lang Structural Engineering Inc. to design the cantilever system. Engineers analyzed overturning forces at the tallest section of the wall, approximately 10.5 ft (3.2 m) high, and sized vertical reinforcement accordingly. Steel dowels were positioned roughly 18 inches (460 mm) on center and aligned with the block cores to simplify installation.

To further increase overturning and shear resistance, the design incorporated a cast-in-place concrete stem poured directly behind the Allan Block units. The back of the block units and removable plywood formwork created the mold for this reinforced concrete section. The cantilever footing dimensions were calculated using traditional cantilever wall design principles, including a forward toe extension and a thickened footing slab. A shear key was also added beneath the footing to increase sliding resistance.

The top 4 ft (1.2 m) of the wall was designed as a conventional geogrid-reinforced segmental retaining wall. This portion allowed easier construction, maintained access to the water main if needed in the future, and allowed the reinforcement layers to account for the overturning forces generated by the fence installed along the top of the wall.

Build

To ensure proper installation, the project specifications required that the retaining wall contractor be an Allan Block Certified installer. Canadian Landscape and Civil Services (CLCS), led by Allan Block Master Wall Builder Darryl Grassick, won the bid and brought the equipment, experience, and training needed to complete the complex project.

Construction began with site clearing and extremely careful excavation near the water main. Although the utility company had already marked the pipeline location, the CLCS crew took additional precautions to physically locate the pipe during excavation to avoid any risk of damage.

Wet weather slowed early construction, but once conditions improved the shear key, footing, and reinforcement dowels were installed and cast. The first course of Allan Block units was placed in a mortar bed on top of the footing to ensure perfect leveling before stacking additional courses.

Concrete was poured in stages, with no more than four block courses filled during each pour to maintain stability. Plywood formwork was used to shape the cast-in-place concrete stem behind the blocks. The crew carefully managed each pour to ensure clean cold joints between placements and thoroughly cleaned the block faces to prevent staining.

Once the masonry portion of the wall reached two-thirds height and cured, the backfill was completed and the upper geogrid-reinforced section was constructed. CLCS then coordinated with fence installers to place construction tubes for the future fence posts.

After the wall caps were installed, the landscaping crew completed final grading, installed the fence, and added sod and landscaping. The parking lot paving soon followed, and the new parking area opened for use.

Through careful planning, innovative design, and skilled construction, the project team successfully completed this complex retaining wall system in just two weeks and within budget, delivering both the performance and appearance the golf course owners wanted.