Background and Overview

Most counties and numerous cities in Oregon do not have municipal stormwater systems as part of their infrastructure, or are only partially served. In addition, parts of the metropolitan area of Portland still have no access to sewer lines. Jurisdictions often use drywells to discharge runoff from public roads and other publicly owned facilities. Private businesses, usually without access to sewer or stormwater systems, also discharge their process wastes into sumps, drywells, trench drains, floor drains, septic tanks and drainfields. These types of disposal practices release wastes directly into the ground and over time pollute groundwater. The pollutants can enter lakes, streams, wetlands, springs, private wells, and public water systems. Contaminated groundwater can have major consequences for a community or industry relying on well water for industrial processing, irrigation of food crops or drinking water.

Surface water and groundwater are hydrologically linked. An estimated 40% or more of the water recharging lakes, rivers and streams in the summer is from groundwater, and conversely during the winter surface water recharges groundwater resources. Due to recent rapid development and growth in Oregon, less groundwater recharge is occurring as water is diverted from natural infiltration to surface water, which is exacerbating the already low summer flows in some areas. Untreated runoff is allowing pollution of groundwater resources. Once groundwater is contaminated, clean up is very costly and it is difficult to restore its quality, and meet health standards needed as a drinking water resource.

Background

The federal government started the Underground Injection Control Program in 1974 as means of implementing the Safe Drinking Water Act (SDWA). The programs goal is to protect freshwater aquifers from contamination due to underground injection systems.

An underground injection system places fluids (mainly stormwater, but also septic effluent, treated drinking water and other fluids) below the ground. The most common UIC systems in Oregon are stormwater drywells, which are usually found on large parking lot surfaces. Large onsite septic systems that have a volume of greater than 2,500 gallons per day or serve 20 or more people are also underground injection systems. Auto repair shops commonly used UICs in the past, but these UICs are now prohibited under federal regulations.

DEQ operates Oregon's UIC Program through authorization from the U.S. Environmental Protection Agency (EPA). Under this program, DEQ issues permits to UIC system operators, handles enforcement of systems to make sure theyre working properly, and conducts rule revisions when program changes are necessary. The program is administered under the Code of Federal Regulations title 40, parts 144 to 146.

Because of inadequate funding and staffing resources, DEQ had been prepared to return the UIC program to EPA in 2006. The Oregon Environmental Quality Commission, however, directed DEQ to propose a fee schedule during the 2007 Legislative Session to bolster program resources. EPA was to take over the program if the legislative proposal was unsuccessful. The proposal, HB 2118, won legislative support and was passed in May 2007.

• Underground Injection Control Stormwater Fact Sheet PDF

DEQ is very concerned that, with the implementation of the Phase II National Pollutant Discharge Elimination Permit System (NPDES) stormwater rules, listing of endangered species, number of water quality limited streams, and Measure 37 claims more jurisdictions and agencies will turn to injection systems for stormwater disposal not realizing the potential environmental impacts.

Contaminants of Concern

Potential problem pollutants have been identified based on their mobility through the unsaturated soil zone above groundwater, their abundance in stormwater, their treatability before discharge, and occurrence in Oregon based on DEQs clean up site database (ESCI). In general, runoff from residential areas are the least likely to pollute groundwater as compared to runoff from industrial, commercial or transportation activities. The risk of pollution depends upon the quality and volume of the injected fluid, pretreatment prior to discharge, depth of injection, depth to seasonal high water table, nature and thickness of the unsaturated zone, soil profile and surfical geology. For example, fractured rock and coarse-grained sediments provide the least attenuation, while clay minerals and organic matter provide the most attenuation.

Cumulative impacts to water quality must also be considered along with the risks to human health. Common pollutants include: heavy metals, toxic organics and others, nutrients, pesticides, salts and microorganisms (e.g. cryptosporidium, E. Coli). For more information on these contaminants of concern please see Appendix A.

Exclusions

It will be DEQ's policy to exclude the following activities from the UIC program:

• Single family residential septic and cesspool systems receiving only domestic waste with drainfields.
• Non-residential septic systems and cesspools with drainfields handling only human sanitary waste and designed to serve less than 20 people per day or with a design flow of less than 2,500 gallons per day (cumulative).
• Hydrocarbon storage at standard pressures (gas) and temperature.
• Any dug hole, blasted or drilled hole, excavated or bored shaft not used to discharge to the subsurface.
• Single residential roof drains and footing drains receiving only rain water provided there is 5 feet of soil between the bottom of the drywell and the high seasonal perched aquifer to protect from bacteria contamination.
• Infiltration and injection systems used for collection (e.g. tile drains, bioswales) which discharge to surface water. Detention ponds, wetlands, rivers and the ocean waste disposal are considered to be surface water discharges. Note; use of perforated piping under a detention pond would constitute installation of an injection system.
• Short term drinking water well disinfection.

Prohibition of Groundwater Contamination

Federal and state rules prohibit the construction, operation, maintenance, conversion, plugging or abandonment of any type of injection system or activity that would allow the direct or indirect movement of contaminated fluids into groundwater if the presence of the contamination may cause a violation of the SDWA MCLs or fails to comply with the Groundwater Act requirements in OAR 340-040. The Groundwater act basically requires discharges to meet existing background water quality at the site.

According to Federal rules, the burden of proof is on the owner/operator of the system, not DEQ to prove that an injection activity does not have the potential to cause a violation of the primary drinking water standards, adversely impact groundwater quality, human health or the environment. All owner/operators of an injection system must register their injection systems and gain written DEQ approval to operate either by; 1) qualifying as a rule authorized; 2) applying for a state permit or; 3) closing the injection system. DEQ can require owners to add pre-treatment, sample and monitor, acquire a permit or closure given situation to prevent potential or existing groundwater contamination.

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