Dry wells are the best kept secret in pavement maintenance for handling localized drainage issues and preserve and protect the surrounding pavement.
An old adage in the business is that “water does not flow uphill.” Taking care of drainage problems where they are naturally occurring is much simpler and less expensive than extensive re-grading of the surface, or installing hundreds of feet of underground pipe to connect to an existing storm water system. And sometimes there is no stormwater system anywhere in the vicinity.
Most people are familiar with the idea of a french drain, which is an open ditch filled with drain rock used in landscaping situations to collect — and slowly dissipate — rainwater to avoid erosion, ponding or other problems. The concept is very similar, but instead we go further vertical underground and the opening is (usually) covered at the surface.
The process is simple.
- Dig an underground pit — usually square like an underground box.
- Place a fabric liner along the bottom and sidewalls of the pit.
- Install a catch basin either at the top of the pit or outside at the lowest spot in the immediate area.
- Connect a discharge pipe from the catch basin to the top and center of the pit.
- Fill the pit to within a few inches of final grade with drain rock, quarry spalls, ballast or another type of large rock without any fines (small aggregates like sand).
- Backfill the pit and/or pipe trench with a few inches of crushed rock, then install pavement (either asphalt or concrete) up to final grade at an appropriate depth for the weight bearing requirements (i.e. a foot path doesn’t need to be as deep as a shipping-receiving warehouse for heavy semi-trucks).
Dry wells also have the advantage of not needing to dedicate valuable area at the surface for a pond, swale or ditch. They can be hidden in landscape areas (like underneath a lawn) or underneath the pavement as described above.
The size of the dry well will depend on the square footage of hard surface area that will be collecting into the dry well, and the type of soil underneath (and adjacent to) the dry well. For example, clay will not disperse water at a very fast rate, river rock will disperse very fast, and other types of soils are somewhere in the middle.
We are glad to design a specific solution to solve your drainage and pavement problems. We also do more traditional drainage work, too, and you can learn more HERE.
More information about dry wells can be found on Wikipedia and from the venerable Bob Villa.
