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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

August 1999

groundwater logo

Threats to groundwater

Air pollution is water pollution, too
Fertilizer and manure storage and application
Use and misuse of pesticides
Ponds, lagoons and land disposal of wastewater
Private onsite wastewater treatment systems

Spills and illegal dumping
Leaking underground storage tanks
Landfills
Abandoned and drainage wells
Sources of natural contamination
Overuse
Groundwater cleanup

Complete table of contents

"The land ethic simply enlarges the boundaries of the community to include soils, waters, plants and animals or collectively: the land."
Aldo Leopold, "A Sand County Almanac and Sketches Here and There," 1948

You name it – gasoline, fertilizer, paint thinner, bug spray – if it's used or abused by humans and dissolves in water or soaks through soil, it may show up in Wisconsin's groundwater. Urban areas require large quantities of groundwater to serve many people. Activities in urban areas that pose significant threats to groundwater quality include industrial and municipal waste disposal, road salting, and the storage of petroleum products and other hazardous materials.

To order printed copies of "Groundwater: Protecting Wisconsin's buried treasure," send an email message to Laura Chern with your name, address and number of copies desired.

In rural areas, less groundwater is used and different threats to groundwater quality exist. Animal waste, septic systems, fertilizers and pesticides are the primary pollution sources in rural areas.

Air pollution is water pollution, too

Particles clouding the air from car exhaust, smokestacks and dust from city streets or farm fields can contribute to groundwater contamination. These particles of hydrocarbons and pesticides settle on the ground, only to be washed into the soil by rain, eventually to trickle into aquifers. And while a rain shower may disperse the particles from the air, the rains can carry the pollutants down into the ground as the water hits land.

Fertilizer and manure storage and application

"Spread the word &. It's good fertilizer!" is the word about manure from the UW Extension's Nutrient and Pest Management Program. To produce good yields, farmers need to apply the nitrogen, phosphorus and other nutrients in manure and fertilizer to their crops. Those nutrients plants can't use will leach into groundwater. Excessive or improper application of manure and fertilizer is Wisconsin's leading source of nitrate pollution in groundwater. Plants can be over-fertilized if farmers don't account for the nutrients contained in the manure they spread on their fields. Proper crediting of the nitrogen and phosphorus in manure saves farmers the cost of purchasing extra commercial fertilizer – and also protects groundwater.

About 10 percent of the private well samples analyzed for nitrate in rural areas show groundwater contamination above the state groundwater standard. Infants under six months and pregnant women should not drink water with nitrate levels above 10 parts per million – Wisconsin's groundwater standard. Mixing baby formula with high nitrate water does threaten infants under the age of six months, because their stomach acid isn't strong enough to kill certain types of bacteria capable of converting nitrates to harmful nitrites. Nitrites bind hemoglobin in the blood, preventing oxygen from getting to the rest of the body; the baby may lose its natural color and turn blue. Methemoglobinemia, or "blue baby syndrome" can cause suffocation. Using bottled water or water with low levels of nitrate can prevent the condition. Nitrate is not usually harmful to adults or older children, though scientists are currently studying the potential health effects.

Use and misuse of pesticides

Insecticides, herbicides and fungicides have been used in Wisconsin agriculture for a long time. These pesticides can reach groundwater when spilled at storage, mixing and loading sites, or when over-applied to fields. "Empty" pesticide containers not properly disposed of are another source of trouble. Just a little spill of most pesticides can have a big impact on groundwater quality. For example, three parts per billion of atrazine in groundwater is enough to increase the risk of cancer in drinking water.

Protecting groundwater from pesticide contamination while maintaining farm profitability isn't easy – too much pesticide and the environment suffers; too little and crop yield goes down. Integrated pest management, or IPM, is a pest control strategy that uses all appropriate control methods (chemical and nonchemical) to keep pest populations below economically damaging levels while minimizing harm to the environment.

Here's how it works: Farmer Johnson "scouts" her fields for weeds and pests. After she has identified what is present, she purchases and applies the minimum amount of herbicides and insecticides only in the areas where weeds and bugs are a problem. Farmers using IPM find they spend less on pesticides. It's a bargain for the environment, too.

Landfills

Thanks to your recycling efforts during the last decade, the amount of waste going into Wisconsin's landfills has been reduced by 40 percent. The wastes we can't reuse are disposed of in properly sited, designed, constructed and maintained landfills, which prevent leachate (the foul liquid that forms when water percolates through solid waste) from polluting groundwater. There are 86 highly engineered licensed landfills in Wisconsin that do a good job of protecting groundwater.

We weren't always so fortunate. In the early 1970s about 2,000 dumps were identified by DNR. Those located near navigable waters, within floodplains, wetlands or critical habitat were ordered closed. Remaining landfills posing a threat to the environment due to hydrogeologic setting or poor operation were required to monitor groundwater and surface water. The monitoring data indicated that some landfills and open dumps were causing groundwater pollution.

Based on the data, and current state and federal regulations, all landfills are now required to have a composite liner system (a plastic membrane on top of four feet of compacted clay) and a leachate collection system to keep liquid waste out of the groundwater. Municipal dumps that did not meet design standards were closed in 1992.

Ponds, lagoons and land disposal of wastewater

Municipal, industrial and private businesses use ponds, lagoons and other methods to store, treat and dispose of wastewater on their property. A familiar example is the small community sewage plant, where a lagoon may be used as the final step in treatment before purified waste is released to rivers or streams, or applied to land.

Lagoons are sealed with compacted clay or plastic liners. Nevertheless, burrowing animals or movement of the soils over time can cause leaks. Routine inspections are necessary to keep lagoons in good repair. Open-air lagoons also are subject to wet and cold weather, which can interfere with the treatment process.

Some industries dispose of their wastewater by applying it to farm fields. The waste is applied according to how much water and nutrients soil and crops can absorb. If the system isn't managed properly, and too much waste and water are applied to the land, or if the operator fails to adjust the amount of liquid applied to account for rainfall, groundwater can be contaminated.

Private onsite wastewater treatment systems

There are almost 690,000 private onsite wastewater treatment systems (septic systems) in Wisconsin – serving approximately 30 percent of all households in the state. Most septic systems are located in unincorporated areas. Here's how septic systems work: waste flows from the house to a settling tank where solids settle out. Liquids continue out to an absorption field. Bacteria in the settling tank break down solid waste leaving a sludge that needs to be removed periodically by a "honey wagon." The liquid seeps into the soil and is used by plants, or leaches into soils and groundwater.

When systems fail, bacteria, nitrate, viruses, detergents, household chemicals and chloride may contaminate groundwater and surface water, and pose public health threats. Even properly installed septic systems may pollute groundwater if they are not used and maintained correctly. About nine percent of the nitrate reaching groundwater in Wisconsin comes from septic systems. Substances such as paint thinner and pesticides can easily leach to groundwater through the absorption field and should never be flushed down a home septic system. Follow this link for tips on maintaining septic systems.

Spills and illegal dumping of industrial and commercial chemicals

When paint thinners, degreasers, electroplating solutions, dry cleaning chemicals, used oil, and a host of other hazardous materials trickle into the groundwater, they contaminate the precious liquid that keeps us all alive.

Accidents happen – over 1,200 spills of toxic or hazardous materials are reported each year in Wisconsin. Luckily, many of those spills are small and can be cleaned up quickly, before an unwanted substance penetrates groundwater.

In the past, first responders to the scene of a spill would attempt to eliminate a fire or safety hazard by flushing the spilled material to a ditch or sewer – bad news for the environment. Thanks to better training, most response efforts now focus on containing and removing the hazardous material to a proper disposal facility. This protects both groundwater and surface waters from becoming contaminated.

An undetermined number of spills go unreported, their presence a secret until area wells become polluted. Although there are strict regulations governing the transport, storage, and disposal of toxic and hazardous wastes, illegal dumping of dangerous compounds continues. Problems from past practices that occurred before regulations were in place still surface periodically.

The threat to groundwater from these toxic products is real. That's why state and federal resources are devoted to finding these sites and cleaning them up. Many programs exist to clean up sites, from the federal Superfund program to address the worst sites in the nation, to the state cleanup program that includes spill response, leaking underground storage tanks, the state Superfund program, and a focus on cleaning up "brownfields." Brownfields are properties that have been abandoned or are underutilized because of actual or perceived contamination. By cleaning up and reusing these properties, we protect surrounding "green fields" from being developed and paved over. This helps keep groundwater replenished, reduces urban sprawl, and prevents future contamination of clean areas.

Leaking underground storage tanks

People in the environmental cleanup business call them LUSTs; for all of us, it spells trouble. Many old leaking underground storage tanks that used to hold gasoline, diesel and fuel oil have slowly corroded and released their contents into the soil and groundwater. Over 13,000 of Wisconsin's older tank systems have leaked as rust took its toll on the tanks and dispensing lines. Even small leaks have caused significant groundwater contamination. Many small leaks went undetected for years. It only takes a little gasoline in water to make it undrinkable; larger quantities seeping into wells or basements can cause explosions.

When corroded underground storage tanks leak, the contents – usually gasoline or oil – can contaminate groundwater.

© DNR Photo
When corroded underground storage tanks leak, the contents – usually gasoline or oil – can contaminate groundwater. © DNR Photo

Property owners and their environmental consultants have been at work cleaning up LUST leaks. Regulations, in place for 10 years now, will help prevent future problems. Rules adopted by the Department of Commerce require that tank systems have corrosion protection, leak detection systems, and spill and overfill containment devices. Older tanks are required to either be upgraded to current standards or to be emptied and removed. The soil is sampled under commercial storage tanks that are removed.

The nature of cleanup operations has changed significantly over the years. Monitoring petroleum contamination as it breaks down into harmless by-products has in many cases replaced soil excavation and groundwater "pump and treat" at locations where the contamination is not spreading.

Abandoned and drainage wells

Years ago, wells were dug by hand with picks and shovels. Hand dug wells were gradually replaced with "well pits" – a six to 10-foot-deep hole through which a well was drilled or driven. Both types are now being replaced by wells that provide more sanitary water.

What happens to the old well can determine how the new well functions. If old wells are not properly filled with cement, bentonite clay or other impermeable materials, they provide a direct channel for pollutants from the surface to groundwater and to other nearby wells. Many thousands of old wells that are no longer used, but still open at the soil surface threaten Wisconsin's groundwater. Whenever you see an old windmill in the country, it's likely there's an improperly abandoned well underneath.

Windmills and old wells make picturesque rural images, but may not produce sanitary water.

© ClickArt, T/Maker Company/Broderbund Software, Inc.
Windmills and old wells make picturesque rural images, but may not produce sanitary water. © ClickArt, T/Maker Company/Broderbund Software, Inc

Wisconsin law allows well owners to abandon certain types of wells using procedures developed by the DNR. Licensed well drillers and pump installers are routinely hired to fill old wells. Follow this link for tips on abandoning wells.

Drainage wells are used to draw water off a section of wet ground by piercing a clay layer, and allowing surface water to run directly into groundwater. Drainage wells have been prohibited in Wisconsin since 1936, but they do turn up occasionally, often when a problem is discovered in a well at a nearby home or farm.

Sources of natural contamination

Minerals existing naturally in soils and rocks dissolve in groundwater, giving it a particular taste, odor or color. Some minerals, such as calcium and magnesium, are beneficial to health. Radium, radon gas, uranium, arsenic, barium, fluoride, lead, zinc, iron, manganese and sulfur are undesirable ingredients found in Wisconsin groundwater. Naturally occurring radioactivity in groundwater, including uranium, radium and radon, has recently become a concern in Wisconsin. Radioactive contaminants expose those drinking the water to risk of cancer.

The state now tests groundwater for radioactivity. Recent sampling has detected radionuclides in some north central Wisconsin groundwater. Gross alpha activity and radium have also been found in water supplies in eastern Wisconsin. The EPA has set drinking water standards for radium and radon.

The problem posed by most natural contaminants is aesthetic rather than safety. Iron is found throughout the state. It stains plumbing fixtures and laundry, and can give drinking water an unpleasant taste and odor. Excess levels of fluoride, manganese, sulfur, lead and arsenic are less common and more localized. In some parts of Wisconsin the groundwater is naturally acidic and can corrode pipes and plumbing, leading to elevated levels of lead and copper in drinking water.

Overuse

Despite a general abundance of groundwater in Wisconsin, there is growing concern about the availability of good quality groundwater for municipal, industrial, agricultural and domestic use, and for adequate baseflow to our lakes, streams and wetlands. Natural shortages of groundwater have occurred due to weather conditions and geologic setting (e.g., prolonged drought and crystalline bedrock aquifers with low yields).

Human activities also cause quantity problems. Groundwater withdrawals in the Lower Fox River Valley, southeastern Wisconsin and Dane County have caused substantial declines in groundwater levels. Human-caused pollution has limited groundwater use in some areas of the state such as Wausau, where industrial pollutants were present in the only aquifer able to supply water to the city. The presence of naturally occurring substances in groundwater such as iron, sulfate or arsenic also limit groundwater availability in some areas. And, when large areas of land are paved over, there is less space for water to seep into the ground and recharge our aquifers.

Groundwater cleanup

Groundwater contamination can be linked to land use. What goes on the ground can seep through the soil and turn up in drinking water, lakes, rivers, streams and wetlands. Tracking down and stopping sources of pollution can be expensive and time consuming. It's usually impossible to completely remove all traces of a pollutant and clean up the aquifer to a usable condition. The cost of even a partial cleanup can be enough to empty the deepest pockets.

Who pays the enormous cost of groundwater cleanup? Logically, the owner or operator of the facility causing the pollution should shoulder the cleanup cost. What happens when the owner is bankrupt, out of business or dead? Then, taxpayers must step in. Federal and state money is used for cleaning up sites and enforcing laws governing disposal of wastes.

When it comes to groundwater, the best strategy is prevention. Prevention means looking at the many ways we pollute groundwater, and finding methods to keep those pollutants at bay. Landfills and wastewater lagoons need to be sited, designed and operated to prevent infiltration to groundwater. Illegal dumping must be prosecuted to the fullest extent of the law. Pesticides must be applied according to need and label instructions, and nutrients should be applied in carefully calibrated amounts to enhance crops without damaging the environment. With vigilance and care, we can protect our buried treasure.