By Mark Hubbard // 2020-08-10
A drywell is a bored, drilled, or driven shaft or hole with a depth that is greater than its width and that is designed and constructed specifically for the disposal of stormwater (Arizona Revised Statutes (A.R.S.) § 49-331(3)). Since stormwater may flow over a variety surfaces it has the potential to pick up and transport many pollutants. In 1987 Arizona Department of Environmental Quality (ADEQ) established standards for the regulation of new and existing stormwater dry wells. The purpose was to establish a framework that limited stormwater dry wells for stormwater use only and also to prevent groundwater contamination by hazardous chemicals. The regulations applied to new development whether it was intended for commercial development, homebuilding or recreational areas.
Dry well registration process has been made easy by ADEQ through the online myDEQ (paper registration is no longer accepted). This registration is required for a person who owns an existing or proposed drywell. There is a registration fee of $100 per drywell and is valid for the life of the drywell, until it is decommissioned.
As dry wells are typically installed during site development and although they may be completely relegated to the interior of the site; it is important to remember that any stormwater flow into the dry well is considered an off-site discharge. Therefore, attention should be given to the planning and protection of all dry wells through routine inspections to ensure that “Best Management Practices” (BMP) are followed. The most common BMP for a dry well is to cover the grate with filter fabric as this is low cost and requires minimal maintenance. Other methods of protection may include berms, wattles, haybales or drop in sediment baskets. Development of a site-specific stormwater plan should also include a list all onsite dry wells as well as those off site but near the project.
Although stormwater only dry wells do not require a permit the registration of these wells helps ADEQ maintain a statewide database/ inventory. As part of the registration process, owners of registered drywells are notified of aquifer protection permitting requirements.
Typical Dry Well Configuration: