Last week, I received a call from a long-term customer asking us to get involved with a new civil project. The catch? It starts in 10 days. Wow—that’s a nice problem to have these days. The site is full of challenges we like: wetlands, a stream relocation, a Federal Highway Administration (FHWA) interface along a major interstate, a new 4-lane public bridge, underground storm water retention and a 800’ long by 25’ high segmental retaining wall.
In regards to the segmental retaining walls, we have had our share of successes and not-so-successes. Here is what we have learned:
Make design the core of your project. All walls that retain earth, even the smallest, should be built using engineered drawings. These should be prepared by a designer who has experience with the wall systems and the site-specific conditions.
Test to give the designer the best starting point. Proper testing is specific to the area of the site where the wall is going to be constructed, prolific enough to provide a complete analysis of the area from one end of the wall to the other, and give an engineer the data that he needs to properly design the wall.
Work together. Successful wall projects have a cohesive team of professionals including the civil engineer, wall designer and geotechnical engineer. Everyone should review and coordinate with each other’s work. It is important to look beyond the design of the wall itself, to the global stability of the soils and slopes that the wall is sitting on. Consider storm water drainage effects, methods for installing fences, guardrails and landscaping and other features beyond the scope of the wall.
We have learned from experience that it is a lot cheaper to resolve conflicts before construction starts, when you’re dealing with lines on paper. A wise engineer once told me, “Whenever there is a design change during construction the cost will always go up.” I’ve found that to be true. We’re planning ahead on this job, trying to foresee difficulties before they cost us time and money.