Stormwater management regulatory requirements are based on the Clean Water Act. Over time there has been an evolution and growth in these requirements from peak discharge reduction to water quality criteria to onsite retention. The stormwater management device being developed by Infiltronics Environmental has a variety of applications in stormwater management and can meet certain regulatory requirements. These include meeting onsite retention requirements, acting as part of a treatment train, mitigating erosion issues, supporting base flow, stormwater management for site redevelopment or retrofit, reduction in basin size, stormwater management in tight or unusual spaces, reduction of overland pollutant transport, and reduction of flow to combined sewer systems.
Test sites are very important in the development of the stormwater management device. They provide data on how the device works, which is important for adoption of the device in real world projects and for the creation of a design tool. The test sites also allow different configurations and use cases to be tested and valuable information is also gained on how the installation process should be conducted. Infiltronics Environmental currently has several test sites, more specific information is below, and is working to secure several more.
Soil moisture data is being collected from the test sites. Soil moisture sensors are placed in a three dimensional grid around the installations so water movement in those three directions can be tracked. This data is being used for development of a design tool for engineers specifying the product and as evidence of the device's functionality for consulting engineers and regulatory bodies.
Maintenance is an incredibly important consideration for any stormwater management method. It is particularly important for this device because clogging is something that needs to be avoided. Sedimentation boxes are used to settle out debris before water enters the installations. The lids of these boxes are flush with the ground level and can easily be accessed for periodic cleaning. The installation is composed of a collection of separate units installed end to end in a shallow excavation. If clogging of the device were to occur, it would primarily occur in the first section of the installation which could easily be accessed and replaced.
The device is a tubular structure composed of aggregate-filled geotextile segments. It produces 3-D flow dictated by differences in the hydraulic conductivities as a result of different aggregate sizes. It is a modular system of devices, with many individual units being placed end to end in an installation. Soil characteristics, site slope, impervious cover, rain fall, site layout, and applicable regulations are considered when a particular mix, number of units, and layout are determined. Pictures of the device can be found in the patent and in photos below.
It is true that clay does not move water as quickly as other soil textures, 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 a variety of areas. These include meeting onsite retention requirements, acting as part of a treatment train, mitigating erosion issues, supporting base flow, stormwater management for site redevelopment or retrofit, reduction in basin size, stormwater management in tight or unusual spaces, reduction of overland pollutant transport, and reduction of flow to combined sewer systems
This product will be used by consulting civil engineers. The engineers will use this technology in development projects, redevelopment projects, erosion mitigation projects, and a variety of other applications. 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.
To quantifiably see how the devices in our test sites are functioning, we install a collection of soil moisture sensors around the installations. With these sensors we can see water after a storm move through our system and out in a "plume" around the units.
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 pipe in the trench helps to move the water quickly, but also greatly reduces the possible infiltration in the french drain.