The future of stormwater management

It is true that clay does not move water as quickly as other soil types, but that does not mean that it does not move it at all. An important fact to remember is that soil infiltration studies are conducted on ground up samples. When considering soil infiltration rates the soil structure (such as roots and worm holes) need to be taken into account since they are natural paths into the soil. Additionally, since the device redistributes water around a site, and not just in one location, like swales or infiltration trenches do, any portion of soil only needs to take a part of the total. On our first test site we had a consultation and site analysis conducted by a soil scientist. The site is composed of 6" lifts composed of compacted glacial till and 40% clay, traditionally not ideal for infiltration. However, even with this soil we are seeing water infiltrating three-dimensionally.

Clogging is definitely something we are aware of and working to avoid. In our first installation we used sedimentation basins to remove as many solids as possible from the water before it enters the units. These are located flush to ground level so they can easily be accessed for inspection and maintenance. The fabric we use is commonly used in construction and landscaping applications when water needs to move between two layers of separated media. Any loss of flow from clogging has been shown to level off over time and this reduction can be considered in design, like sedimentation in a pond would be. Finally, the units are installed in only 18" deep trenches and are installed in 3' lengths. If clogging were to occur, it would be in the first segment, and that could easily be excavated and replaced by a new 3' segment. 

We see this product being used in three main areas. First, as a part of a treatment train in new and redevelopment projects to help reduce the size of required ponds by utilizing our device under green space such as landscaping and lawns. Second, in special cases such as reducing flow into combined sewer systems from places like home gutters and to meet special requirements such as keeping a portion of stormwater onsite. Third, for erosion mitigation and prevention on sites that do not require additional stormwater management but are dealing with erosion issues from parking lots, drain pipes, other sources of concentrated water, and severe overland flow. 

This product will be used by consulting civil engineers and specially trained landscapers. The engineers will use this technology in development projects, redevelopment projects, and erosion mitigation projects. They will be working on behalf of their clients, usually developers and municipalities who hire them to make sure the project is designed to meet their needs, is safe, and follows all regulations it is subject to. The landscapers will also use this product for projects dealing with erosion mitigation, but on a smaller scale than the engineers, such as individual homes. 

To quantifiably see how the system in our first test site is functioning we installed a collection of soil moisture sensors around the installation. With these sensors we can see water after a storm move through our system and out in a "plume" around the units. The video below displays this. 

French drains are composed of a trench lined with geotextile fabric and filled with gravel and a perforated pipe. They work to convey water away from a location, such as a foundation, as quickly as possible. The trench in the pipe helps to move the water quickly, but also greatly reduces the possible infiltration in the french drain.