The federal UIC program was enacted in 1974, under the Safe Drinking Water Act, and is administered under 40 Code of Federal Regulations part 144-146. The UIC program's goal is to protect freshwater aquifers from contamination due to underground injection systems. In 1984, EPA gave DEQ authority to regulate UIC systems on EPA’s behalf, and re-authorized the program in 1991. DEQ regulates the UIC Program under Oregon Administrative Rules Chapter 340, Division 44.
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.
DEQ operates Oregon's UIC Program through authorization from the Environmental Protection Agency. 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.
Contaminants of Concern
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 allow the contaminants to travel greater distances more rapidly, while clay minerals and organic matter the most restrictive to movement of contaminants.
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).
- Heavy metals are associated with runoff from streets, parking and landscaped areas. Generally up to 70% of the total metal concentration will bind with sediments; however, some metals are more mobile or soluble in water than others. Those in order of concern (based on mobility in water) are: zinc, lead, cadmium, manganese, copper, iron, chromium, nickel and aluminum.
- Toxic organics are most often associated with industrial and commercial sites which use, sell or produce gasoline, wood preservatives, oil, grease, asphalt, insecticides, plastics, fumigants, solvents, paints and pesticides. Vehicle service areas have the greatest frequency and quantities of organics.
- Volatile Organic Compounds (VOC) commonly found in groundwater include: carbon tetrachloride, chloroform, tetrachloroethene, 1,1,1-trichloroethane, trichloroethylene, and trichloroethene. VOCs are most commonly associated with urban groundwater contamination because of the large numbers of sources for these pollutants. Polycyclic aromatic hydrocarbons (PAH) are associated with industrial sites. Groundwater contamination from organics occurs more readily in areas with sandy soils and high water tables.
- Nutrients of concern in Oregon are most often nitrates and phosphorus. Nitrates are the most frequently encountered contaminant in groundwater, since they are highly soluble and stay in solution for a long time. Nitrate concentrations tend to be highest in groundwater that has low dissolved oxygen concentrations and in areas of high soil permeability. To a large degree nitrate concentrations in groundwater reflect land use practices at the time the water infiltrated into the soil. The U.S. Geological Survey (USGS) found that nitrate concentrations in groundwater were highest down gradient of irrigated lands as opposed to non irrigated land.
- Pesticide use in both urban and agricultural areas can result in groundwater contamination from stormwater runoff. Pesticides decompose in soil and water, but the total decomposition time can vary from days to years. Pesticides are mobile in areas with coarse-grained or sandy soils without a hardpan layer, and in soils, which are low in clay and organic matter and have high permeability. Infiltration of rain and irrigation water facilitates the transportation of pesticides to groundwater. USGS studies found most pesticides detected in groundwater were herbicides such as atropine, simazine, metolachlor, diuron, DCPA, and propanil.
- Salts used for deicing of roads and airports are also of concern since they can contaminate groundwater and impact drinking water supplies. The most commonly used deicing agents are sodium chloride, calcium magnesium (CMA), motech or CMS-B, CG90 surface saver and Verglimit. Road salt also contains a number of impurities including several nutrients and metals, which can impact groundwater.
- Microorganisms such as, bacteria and viruses have been detected in groundwater where stormwater recharge basins were located short distances above an aquifer.
- Pathogens of concern include enteroviruses, pseudomonas aeruginosa, Shigella, cryptosporidium and protozoa. Microorganisms are associated with discharges from onsite septic systems, sewage drill holes, stormwater injection systems and cesspools.
The following activities will not be considered UICs under the Oregon DEQ 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).
- Injection for the purpose of storing hydrocarbons that are gases at standard pressure and temperature.
- Any dug hole, blasted or drilled hole, excavated or bored shaft not used to discharge to the subsurface.
- Single family residential roof drains. There is no requirement for vertical separation distance from groundwater for roof drains.
- 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.