Detention And water quality is nearly ALWAYS required for any new development or
redevelopment. Everybody knows about the standard wet pond, dry pond, and even
underground arch-style detention. Here are a few alternatives to look at that could save time,
space, and/or $$.
1. Planted/River Rock Swale
In very specific circumstances, a small swale at minimum slope can be used to slow
down the water and extend the proposed time of concentration. This can help reduce or
even eliminate required detention and can sometimes be used for water quality.
LandWorx recently used this on a small industrial site in combination with some pervious
pavement which allowed the owner to avoid detention altogether!
2. Bio-retention/Raingarden
This has the potential to provide both detention and water quality in one fell swoop.
There are restrictions depending on the AHJ (Authority Having Jurisdiction) and will
require plantings, but can provide long-term protection and beauty to a site.
3. Alternative Underground Solutions
Podium solutions can provide more bang for your buck than traditional arch- or pipe
underground detention systems. They provide over 90% voids in the volume installed, so
the overall footprint can be much smaller while still providing the potential for infiltration.
LandWorx has used Stormbrixx systems recently and they have been a solid and easyto -construct solution in small footprint situations.
4. Green Roof
While an expensive option, this can lead to avoiding detention altogether by slowing
down stormwater and taking away impervious cover. The structural trade-offs are
sometimes worth it on very tight sites and can provide a benefit through a rooftop deck.
LandWorx completed a mixed-use building in the Near Northside of Indianapolis in which
a partial green roof allowed for the rooftop deck and saved from having to construct an
underground system that would have had to be under the building!
5. Infiltration Trench
This is a gravel-filled trench that provides volume for detention AND treatment. It can be
combined with infiltration or have an underdrain for an outlet. It works as both water
quality and detention and, depending on AHJ requirements, can even be covered with
grass for easy maintenance and a clean look. No solution is one-size-fits-all and your site situation may dictate what is needed to meet local requirements. That said – combinations of the above or other options may be the best solution. Ask questions – For instance, owners are sometimes not aware that spending $100k for upgraded structural and a green roof may save them $250k in underground detention costs or that a rain garden may save $150k in pipe and provide an aesthetic that will make the property worth more in the long run.