The following highlights the main permit conditions that must be met when considering the use of a UIC. A copy of ODOT’s UIC permit is available on the
ODOT stormwater webpage.
Design Elements
Project designs that incorporate UICs require close coordination between the Statewide Project Delivery Branch’s Environmental and Hydraulic Engineering Section, the Maintenance and Operations Branch and individual maintenance districts, and region staff in order for ODOT to fulfill all permit obligations. For UIC design guidance, see Chapter 14 of the HDM.
Location
A UIC may not be installed within the horizontal or vertical setback area (described below) without first obtaining a design deviation endorsed by the region tech center manager and approved by the State Hydraulic Engineer. UICs that discharge directly to groundwater are prohibited. Do not use UICs in geologically unstable areas. Additionally, do not use UICs where there is existing ground or groundwater contamination. Stormwater injection can cause, accelerate, or change the direction of movement of the contamination.
If it is necessary to place a UIC within the horizontal setback, the engineer of record must conduct a groundwater protectiveness demonstration and receive approval by DEQ prior to installation. Additional information about groundwater protectiveness demonstration, including a list of areas where groundwater demonstrations have been conducted, is included in the Groundwater Protectiveness Demonstrations for UIC Permits Fact Sheet from DEQ.
The Project Team must coordinate with the region senior hydraulic engineer prior to designing a UIC in the setback area, and to provide any exception approval paperwork received from DEQ.
Horizontal Setbacks
The required setback is:
- Outside the 2-year time-of-travel zone for public water wells (see the DEQ Drinking Water Program Maps and Data website), if one has been determined by the Oregon Health Authority (OHA), or
- More than 500 feet from known public drinking water, private drinking water or irrigation supply wells, if OHA has not designated the 2-year time-of-travel zone.
Vertical Setbacks
The bottom of the UIC must be at least 5 feet above the seasonal high groundwater table elevation in order to meet the groundwater protectiveness requirements outlined in ODOT’s permit. Sufficient site information demonstrating that the vertical separation requirement is met must be collected prior to installation.
General Considerations
- Evaluate soils at the site to determine design infiltration rates as outlined in Chapter 14, Section 14.9.6.2 of ODOT’s Hydraulic Design Manual.
- Avoid placing UICs where they will receive stormwater from non-ODOT drainage.
- Place UICs and associated BMPs in locations that can be safely accessed by maintenance.
- Provide adequate right of way for the UIC footprint including the area needed to accommodate all facility components, maintenance access roads, and maintenance operational areas.
Discovery of Existing UICs
If an existing UIC is discovered during construction ODOT must notify DEQ by email at UIC@deq.state.or.us. Contact the Senior Stormwater Hydraulic Engineer to determine if the UIC is already registered. Confirm with the Senior Stormwater Hydraulic Engineer if registration is warranted and register if necessary (see Documentation). Determine if meets setbacks. If doesn’t meet setbacks provide a protectiveness demonstration. Retrofit if necessary. Decommission if necessary.
Pre-Treatment
New UICs must include or be preceded by a structural Best Management Practice (BMP) that effectively removes sediment and oil. Pre-treatment BMPs are described in the Hydraulic Manual. Existing UICs that will be used to manage project stormwater must be retrofitted with a structural BMP when a new project requires work on the UIC or drainage in a highway section that includes a UIC.
Spill Protection
Provision must be made so the UIC can be isolated from spills of hazardous material and other potential pollutants. This can be done by including a shut-off valve between the final inlet to the drainage system prior to the UIC, or by confirming that all inlets to the drainage system can be blocked off. The latter approach is not appropriate where the drainage system serves properties that are not owned or operated by ODOT because ODOT staff may not have access to the affected inlets. Protocols for dealing with spills must be included in the UIC’s operation and maintenance manual.
Retrofit Strategy
The agency target for implementation of a statewide Stormwater Retrofit Program is March 31, 2027. If a statewide Stormwater Retrofit Program has not yet been established, then a region may prepare an interim region-specific retrofit plan that strategically prioritizes structural BMP retrofit projects in the future with approval from the state hydraulic engineer. A design deviation may be requested to postpone a structural BMP retrofit of an existing UIC. Postponement requires the UIC be included under a statewide stormwater retrofit program.
Decommissioning
There are three steps to decommissioning an ODOT stormwater UIC: Step 1 (Notification), Step 2 (Sampling), and Step 3 (Closure). Step 1 involves giving notification to the ODOT Senior Stormwater Hydraulic Engineer and the Clean Water Coordinator to document the closure. ODOT’s UIC Permit allows ODOT self-approval for UIC closures and a Pre-Closure Notification Form submittal to DEQ is not required. For UICs that are high risk (i.e. signs of improper practices, samples show contamination, etc.), ODOT must communicate this information to DEQ immediately by email at UIC@deq.oregon.gov with a copy to the Senior Stormwater Hydraulic Engineer and the Clean Water Coordinator.
Step 2 involves coordinating with ODOT region hazardous material geologist and collecting samples. DEQ requires sampling of sediment in UICs where field screening of sediment inside the UIC indicates the presence of contamination or of a spill, or if the sediment inside the UIC is going to be transported it must be sampled to determine if it must be handled as hazardous waste or non-hazardous waste. Sampling is not required for stormwater UICs that drain runoff solely from roofs or private driveways. The material must be analyzed to determine if the sediment needs to be managed as a hazardous waste. Additional analyses may need to be conducted if evidence of a chemical spill is found during closure. Coordinate this task with the ODOT region hazardous material geologist.
The final step is closure of the UIC. Close the UIC in a manner that prevents vertical fluid movement. If you are closing a vertical UIC, remove the top four feet of the UIC structure and backfill with fill material. At a minimum, the upper four feet of the hole must be backfilled with impermeable material (a fill material of 300 pounds per square inch controlled density fill meets or exceeds Oregon Water Resource Department abandonment requirements) that mushrooms out over the top of the UIC. Horizontal UICs can be closed by installing a permanent plug comprised of controlled density fill. Closure must be overseen by a licensed geologist or engineer, which is necessary to ensure that decommissioning meets the standards of OAR 340-044-0040.
For additional information on UIC closure, refer to DEQ’s UIC Frequently Asked Questions webpage.
Documentation
The permit requires that all new, newly discovered, retrofitted and decommissioned UICs be documented and reported in the annual report to DEQ. To support the annual report requirement, the project team must fill out the UIC Registration Form and submit the form to the Senior Stormwater Hydraulic Engineer for entry into ODOT’s UIC inventory, unless the UIC is determined not to need registration. In addition to the registration form, each UIC requires a drainage facility identification (DFI) number assignment for tracking in ODOT’s asset management system. DFI numbers are assigned by contacting ODOT’s Senior Stormwater Hydraulic Engineer to obtain a unique “DFI”. The project hydraulic designer requests drainage facility IDs during the project’s PE phase as discussed in Chapter 17 of ODOT’s Hydraulic Design Manual. The DFI for a UIC refers to both the UIC BMP itself and the associated pretreatment BMP(s). The UIC Registration and DFI Request Forms are available on the ODOT hydraulics webpage in the Design Resources, Project Design Process Forms section.
Both the registration form and the DFI number are to be requested concurrently during a project’s preliminary engineering phase, and prior to completion of the Stormwater Design Report. A copy of the DEQ approval for installation or decommissioning of a UIC must be provided to the Senior Stormwater Hydraulic Engineer.
The information necessary for registration is detailed in the UIC Registration Form. Refer to the ODOT Hydraulics Design Manual, Chapter 17 for DFI registration requirements.
Operation and Maintenance (O&M) Manuals
The purpose of O&M manuals are to support maintenance, protect water quality and ensure compliance with permit commitments. An O&M Manual describes the type of facility and how it operates, outlines an inspection schedule, and summarizes maintenance actions. Guidance on preparing O&M Manuals is outlined in Hydraulics Design Manual, Chapter 4 and technical bulletin GE16-02(B).