Definition of a UIC well
An Underground Injection Control (UIC) well is a manmade subsurface fluid distribution system designed to discharge fluids into the ground and consists of an assemblage of perforated pipes, drain tiles, or other similar mechanisms, or a dug hole that is deeper than the largest surface dimension (WAC 173-218-030).
Typical UIC stormwater wells (drywells)
Subsurface infiltration systems include drywells, pipe or French drains, drain fields, and other similar devices that are used to discharge stormwater directly into the ground. Drywells are UIC wells completed above the water table so that the bottom and sides are typically dry except when receiving fluids. Drywells may be stand-alone or as part of a larger drainage system, such as the overflow for a bio-infiltration swale or other stormwater treatment BMP.
Infiltration trenches with perforated pipe surrounded by a drain rock envelope are considered to be UIC wells.
The following are not UIC wells:
- Buried pipe and/or tile networks that serve to collect water and discharge that water to a conveyance system or to surface water.
- Surface infiltration basins and flow dispersion stormwater infiltration facilities.
- Infiltration trenches designed without perforated pipe or a similar mechanism.
Residential UIC wells used for roof runoff or basement flooding control are exempt from the registration requirement. All other UIC wells must be registered. The registration form can be found at the Ecology Web site at: http://www.ecy.wa.gov/programs/wq/grndwtr/uic/registration/regforms.html.
UIC wells constructed prior to February 3, 2006, are considered to be “existing.”
- Owners of 50 wells or fewer must register their wells by February 3, 2009, and complete their well assessment by February 3, 2011.
- Owners of more than 50 wells must register their wells by February 3, 2011, and complete their well assessment by February 3, 2013.
UIC wells constructed on or after February 3, 2006 are considered to be new. The registration provides the department with information needed to determine if the new UIC well meets the conditions to be rule-authorized.
- The registration form must be submitted prior to construction.
- The non-endangerment standard must be met (see the UIC Guidance document located at http://www.ecy.wa.gov/biblio/0510067.html).
Existing UIC wells
UIC wells that were constructed before February 3, 2006, have different requirements than wells constructed on or after the revised rule became effective. Existing UIC wells are grandfathered in with respect to the rules that became effective on February 3, 2006. A well assessment must be completed to determine if any of the existing UIC wells are a high threat to ground water. UIC wells that are a high threat to ground water must be retrofitted to protect ground water quality.
UIC wells constructed prior to February 3, 2006, must also be registered, if this was not previously done.
The following is the definition of a well assessment (WAC 173-218-030):
Well assessment means an evaluation of the potential risks to ground water from the use of UIC wells. A well assessment includes information such as the land use around the well which may affect the quality of the discharge and whether the UIC well is located in a ground water protection area. It may include the local geology and depth of the ground water in relation to the UIC well if the well is considered a high threat to ground water.
The UIC Guidance document (http://www.ecy.wa.gov/biblio/0510067.html) may be used as a helpful guide for the well assessment. Here is an excerpt from WAC 173-218-090(2): “The approach to conducting the well assessment will be determined by the owner. The well assessment evaluates the potential risks to ground water from the use of UIC wells and includes information such as the land use around the well which may affect the quality of the discharge, and whether the UIC well is located in a ground water protection area. It may include the local geology and depth of the ground water in relation to the UIC well if the well is considered a high threat to ground water. The well assessment requirements will be met if an owner or operator applies the storm water best management practices contained in a guidance document approved by the department to their UIC wells and determines if the UIC well is located in a ground water protection area.”