With storm water regulations getting more and more strict, keeping drainage and storm water on-site has become more and more important. The best way to handle storm water on a site is grade the side to maximize natural infiltration into the soil.
Sometimes a site is too small, or the grades are too restrictive to allow for infiltration without some assistance. Typically this is done with a dry well. But the traditional dry well has its limitations. A dry well (dispersion field, dissipater field) is an excavated area constructed to allow for the infiltration of water, typically filled with 3/4″ crushed gravel. The main problem with dry wells is that half the volume of the well is filled with gravel, thereby limiting the amount of water that can enter the system and infiltrate into the soil. Take this example:
If you have a dry well that is 8′ long x 4′ wide x 2′ deep filled with gravel its capacity is only about 240 gallons of water at any one time. Let’s say you were trying to drain a 1,000 sq.ft. roof into the dry well. In a 1″ storm the roof would discharge about 550 gallons of water.
Fortunately, with the increased focus on stormwater management, there are some newer products that help with this problem.
Cudo Cube, based out of Sonoma County, offers a great customizable modular product that is 2′x2′x2′ and can store about 50 gallons of water as well. The Cudo system can also be customized for maintenance access, discharge point, and filtration. The units can be combined to create large drainage fields.
NDS has a couple of products that allow for easier drainage installations. The Flo-Well is a customizable plastic drum that holds about 50 gallons of water and can be plumbed into a drainage system or off a downspout. These units can also be connected together.
NDS also makes the new EZFlow french drainage pipe, that incorporates a traditional black corrugated pipe with a synthetic drainage medium that looks like a packing peanut. A 10″ EZFlow (4″ pipe with 6″ of drainage peanuts) can store about 2 gallons of water per linear foot.
ADS also has a number of products designed for stormwater and leachfields on a larger scale. Their AdvanEdge product is another useful alternative to French drains to help drain against retaining walls, into dry fields or under wet areas.