Product: AB Ashlar Blend
Size: 55,000 ft2 (5,110 m2)
Miller Wall Company
400 North Link Lane
Fort Collins, CO 80524
Allan Block Manufacturer:
Level Surface for Candelas Medical Development
In Arvada, CO the residential development market is expanding exponentially, which in turn requires the medical infrastructure to grow as well. The Candelas Medical office building is the first phase in the Candelas Master Development plan, making a retaining wall a necessity to level out the uneven site for future construction.
CTL Thomas was contracted to determine the best solution for leveling out the site while satisfying visual concerns of the surrounding housing developments. Over the planning stages the retaining wall underwent multiple iterations of terraced configurations to achieve the optimal grade changes to facilitate site development, while reducing the cost of the project. The final layout resulted in a terraced application that transitions from a single wall up to 7 walls for a total height of ~35 ft (10.7 m) using the Allan Block Ashlar Pattern elevated the aesthetics of the project.
CTL Thompson has been involved with many retaining wall designs before, therefore a multi – terraced wall that consisted of corners and curves was not a problem. Following industry best practices the retaining wall design maintained a 2-course grid spacing throughout the tiers with a grid length of 60% of the overall structure. Other design recommendations that were included focused on the elevations between the tiers (Best Practices 10.3).
Terraced Height and Grading
- The top of the lower terrace should be at the same elevation as the bottom of the next terrace.
- Grade the soil between the terraces starting at the back of the lower wall and sloped to bury at least one full block of the upper terrace.
CTL Thompson wanted to ensure that the upper terraces would not be subject to excessive settlement since the upper walls’ foundations would be the infill of the lower walls. To prevent excessive settlement, the engineers used a select structural fill and extended the top grid of each wall 4 ft (1.2 m) past the toe of the upper tiers. By doing this, the loading of the upper walls is distributed along the geogrid and reduces pressure on the foundation soil. The engineers also emphasized the need for proper compaction of the infill soils to reduce the potential settlement, especially where the walls divide into multiple terraces.
Once the plans and design were finalized, construction could begin. Miller Wall Company has been installing retaining walls since 1984, making them an excellent team for the job. With the scale of this project, managing logistics and truck efficiency was the biggest challenge, but they worked through it with open communication and planning.
Donnie Farmer with Miller Wall Company had this to say about the project:
“50,000 square feet (4645 m2)of block and 50,000 tons of structural fill were delivered and installed in 125 working days. We had 2,000 Linear feet (610 m) of retaining wall, up to 7 tiers in some places- with only rear access. We had a successful build, and we are very proud to have been a part of this project.”
We all know that flat buildable land is a premium and site developers need to get creative. For a site this large, multiple walls and terracing were required to allow this particular property to be developed. Once again, Allan Block was used to successfully provide the best solution.