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The Underground Injection Control Program (UIC) protects groundwater quality by regulating discharges to UIC wells.
UIC wells are manmade structures used to discharge fluids into the subsurface. Examples are drywells, infiltration trenches with perforated pipe, and any structure deeper than the widest surface dimension. The majority of UIC wells in Washington are used to manage storm water (i.e., drywells) and sanitary waste (large on-site systems), return water to the ground, and help clean up contaminated sites. The potential for groundwater contamination from injection wells depends upon well construction and location; quality of the fluids injected; and the geographic and hydrologic settings in which the injection occurs.
Examples of UIC wells: drywells, infiltration trenches with perforated pipe, storm chamber systems, geo probes or push probes, and septic system drain fields serving 20 or more people per day.
Guidance for UIC Wells that Manage Stormwater
This document provides the design and best management practices (BMPs) to reduce solids, metals and oil from UIC wells used along roads, parking areas or used to collect roof runoff (if using the presumptive approach). This Guidance is not to be used for the design of infiltration trenches with perforated pipe (see following section).
Clarification from EPA on which stormwater infiltration practices/technologies have the potential to be regulated as "Class V" Wells by the UIC Program
Note: this memo is available in Adobe Acrobat (.PDF file) format. To view and/or print PDF files, you first will need to download and install Adobe Acrobat Reader.
Infiltration Trenches with Perforated Pipe
Infiltration trenches with perforated pipe must be registered (except for trenches that receive only roof runoff from single family homes or duplexes or used to control basement flooding). They are designed, constructed, operated, and maintained according to either the current Stormwater Management Manual for Western (2012 or 2005) or Eastern (2004) Washington, or an equivalent approved manual. Note: Section 5.6, Subsurface Infiltration of the Stormwater Management Manual for Eastern Washington Manual (which was replaced by the Guidance for UIC Wells that Manage Stormwater) does not apply to infiltration trenches. View a summary of the infiltration trench design requirements for Eastern and Western WA. If an infiltration trench will be located in Western WA and in an National Pollutant Discharge Elimination System (NPDES) stormwater-permitted community, use the manual that is required in the stormwater permit. For trenches located in Western Washington and not in an NPDES permitted community, use the 2012 Stormwater Management Manual for Western Washington to design and maintain the infiltration trench.
Infiltration trenches used at a single family home and receiving only residential roof runoff are exempt from registering.
Approved treatment Best Management Practices (BMPs) for UIC wells
If a UIC well requires a treatment BMP for rule authorization, the BMP must be an Ecology-approved BMP. For the list of approved BMPs go to treatment options for E and W WA and Ecology’s Evaluation of Emerging Stormwater Treatment Technologies page for approved treatment products. Click on the Approved SW Technologies link (left side of the page near the bottom).
Well Assessment Example for Vehicle and Metal Recyclers
The purpose of a UIC well assessment is to determine if UIC wells are a high threat to groundwater. A well assessment is required for all UIC wells built and in use prior to February 2, 2006 and used to manage stormwater. Wells constructed after 2/3/2006 must be built to the current UIC Program rule, chapter 173-218-WAC UIC Program and the current Ecology stormwater management manual for the location of the well.
Heat pump/air conditioning return flow wells are used to return ground water back to the subsurface that has been circulated through an open-loop, heat pump/air conditioning (HAC) system. UIC rule authorization (approval) is granted for wells if the discharge water will not impair beneficial uses of ground water or nearby surface water. Return flow wells in hydraulic connection with surface water bodies or wells requiring a water right permit are not automatically rule authorized, and additional information is required for registration.
Do you know where your floor drain discharges? Many floor drains send untreated waste fluids directly to UIC wells, such as septic systems, drywells, or to a pit or cesspool. The waste fluids could reach the ground water, or go to a lake or stream.
More information on drain fields
Read "Pain in the Drain" article on page 3 of Shoptalk, Volume 20, No. 1, February 2010.
Groundwater remediation projects where Ecology regulatory resolution is required should be conducted through the Toxics Cleanup Program. UIC registration would be part of a voluntary cleanup process (www.ecy.wa.gov/programs/tcp/vcp/Vcpmain.htm) or formal MTCA order.
Registration forms have been updated; infiltration questions were added.
What is the UIC Program?
UIC Class 5 Well Fact Sheet (EPA)
A search-able, read-only version search tool for the UIC database is available. It can be queried several ways. A UIC number is assigned to each site and entered into the database. Assignment of a UIC number does not mean the site qualifies as Rule Authorized or is in compliance. The UIC well system has to meet the ground water protection requirements of the program to be rule authorized.
Frequently Asked Questions
For more information on the UIC program please contact:
Mary Shaleen Hansen
Water Quality Program
WA Department of Ecology
P. O. Box 47600
Olympia, WA 98504-7600
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