Helical Piers in Wetlands

“Wetlands” can imply many conditions. It could imply a lake, river, or swampy area. It could be a soft wetland that has standing water at certain times during the year. Maybe it’s a site with a high water table, making the soil soft and compressible. Often, these are organic sites, such as muck or marl.

What happens if you want to build on these sites? Is it possible? Will helical piers help? The answer is yes.

But the first issue is not foundations but permits. The local and state rules often control your options. Grandfather rules, existing buildings on the site, and other factors can affect the results. Use of the structure can also influence permits. Generally time consuming processes and engineering are implicit in the goals.

If options are open, helicals are a very viable option.

So what might be the project? A cottage, permanent home, storage building, garage, or even a boat garage might be your idea. Yes, helicals have potential for all of these. But in such bad conditions, how can these be effective?

The first thing to know is that, almost undoubtedly, there is good bearing soil there. The problem is that it might be 10, 20, 40, or more feet below the surface. This is OK because helicals can be turned deep into the “bad stuff” to get to the “good stuff”. Even in the lake bottom that is organic, helicals can extend through the loose stratum. Clearly, a soil boring would be helpful to predict depths, but it doesn’t change how deep it will go.

Your structure should be engineered for pier placement and loading. From that information, helicals can be designed and installed. The top of the helical can have a custom cap to accommodate what you need, such as concrete grade beams, pre-cast concrete beams, wood or steel beams. Top bracket designs can vary widely.

Two huge advantages, among many, include no vibrations during installation. Close neighbors have nothing to worry about. Additionally, small equipment or even hand held equipment can be used to install helicals. This gives great flexibility. One could even install them through frozen areas in winter which, in some situations, solve some access problems.

Design of the pier itself is very important. An extended length of very soft soils would require a design that might include any of: over specifying for a stiffer column shaft, grout tubular members, using re-rod to strengthen grout, x-brace piers shafts above grade, or using lateral piers to resist lateral movement. Clearly, a quality contractor and engineer are very important.

For construction on a desirable wetland site, helicals will be the key component to make it work.