Appendix A: Contaminants of concern 

• 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.