Potential Sources of Contamination
As groundwater migrates, any associated nutrients or toxins will migrate with it. Contamination migration refers to groundwater that has been contaminated and is migrating toward a well.
Crop Fertilizers & Pesticides
Irrigated crops are 1 of the highest risks to public drinking water in Oregon. Fertilizers and pesticides used in large agricultural operations can cover thousands of acres. Potential contamination can be associated with the timing, amount, and placement of fertilizers and pesticides. Over watering after application may transport contaminants or sediments to the drinking water source through runoff.
Feedlots concentrate large numbers of livestock animals in confined area, thus producing a tremendous amount of waste. Improper storage and management of animal wastes may impact drinking water. Potential contaminants include bacteria, nitrate, phosphate, and insect control sprays into groundwater and surface water sources.
Cutting and yarding of trees may contribute to increased erosion, resulting in turbidity and chemical changes (nitrate for example) in drinking water. Over application or improper handling of pesticides or fertilizers may also impact drinking water. Road building and maintenance for forestry practices may contribute to erosion and slope failure causing increased sediment in drinking water. Vehicle usage also increases the risks of leaks or spills of petroleum products or other hazardous materials.
Prized for their greenery, golf courses can be a source of excess nutrients or pesticides that make their way into public drinking water supplies. Over application or improper handling of pesticides or fertilizers can cause contamination. Excessive irrigation may cause transport of contaminates to groundwater or surface water through runoff. Furthermore, many golf courses tend to be within or adjacent to residential areas that are within drinking water source areas.
House & Yard Chemicals
Chemicals used in the house or yard can potentially leak into the groundwater or run off the land during rain events into rivers or streams and contaminate drinking water sources. Spills, leaks, or improper handling of chemicals, fuels, and other materials during transportation, use, storage, and disposal may impact the drinking water supply.
When rainwater hits an uncovered pile of manure it can cause bacteria, pathogens, and nitrate to leach into groundwater or run off into surface water. Manure piles should be at least 100 feet from wellheads and waterways, on higher ground, and away from drainage ways. Covering piles with tarps or structures prevents runoff and leaching issues during the rainy season. Covered manure can be composted and used as a nutrient rich soil amendment.
Rain often washes chemicals such as gasoline, oil, solvents, pesticides over impervious surfaces (roads, parking lots, driveways) and into rivers and streams. Urban areas in particular are often responsible for a significant amount of runoff. Minimizing stormwater runoff helps to protect drinking water supplies.
Public Water Supply
Clean drinking water is a primary determinant of public health. Provided through public utilities, the public water supply is responsible for providing clean water via surface and/or groundwater sources to schools, campgrounds, businesses, and cities. Public water supplies are routinely monitored to be checked for things like bacteria and nitrate.
Residential Yard Fertilizers & Pesticides
When applied in excessive amounts or during the wrong season, yard fertilizers and pesticides can be washed into a stream or from the yard to the street, and eventually into drainages that make their way to streams and rivers. If fertilizer is not completely taken up by plants nutrients can also move into the groundwater and taint drinking water supplies. Overwatering after application may transport contaminants to the drinking water source through runoff.
Rural Home Well
Most rural residents depend on domestic wells for drinking water. Groundwater that supplies these wells can be contaminated by the same things that contaminate public water supplies like failing septic systems, household chemicals, spills. It is important to protect the land around wells and minimize potentially harmful activities in these crucial areas. Domestic wells are not required to be routinely monitored, so it is up to the homeowner to have the quality of their water checked.
Sand & Gravel Aquifer
Aquifers, like the Willamette aquifer house groundwater between the pore spaces of sand and gravel. According to the U.S. Geologic Survey, "more than 80% of the groundwater used in the Willamette Basin is pumped from the alluvial aquifer," the shallow portion of the aquifer made up of sediments. Sand and gravel aquifers are generally very permeable, making them potentially vulnerable to contamination.
Septic tanks and their associated drainfields can be very effective ways of treating domestic waste from rural homes. However, it is crucial to regularly maintain these systems. If they fail they can release untreated sewage into the groundwater and potentially into rivers and streams.
The water table is the top most level at which sub surface water settles. An aquifer is established below the water table through percolation of above ground water sources. A number of factors can influence the level of the water table including rainfall amounts, permeability, geologic features, and drafting of water from pumps and wells.
Water Treatment Plants / Lagoons
Improper management of wastewater, treatment chemicals, or equipment maintenance materials may impact drinking water. Sewage can leach into groundwater especially if soils are permeable and there is no liner or barrier between the lagoon and the groundwater.