ANSWERING QUESTIONS NOW
Our experts answer your questions about nitrate pollution
Our team of scientists, lawyers, and subject-matter experts have been diving deep into Minnesota's nitrate pollution issue. MCEA has compiled frequently asked questions about this subject. Explore what folks are asking and see answers from our experts.
Karst region groundwater pollution
Answered by MCEA Water Program Director, Carly Griffith
Karst is a unique topography characterized by dramatic bluffs and cliffs as well as sinkholes, caves, and springs. Much of the area in southeastern Minnesota has karst geology, which developed over millions of years.
In karst country, the bedrock lies under little soil and is normally fractured in “swiss cheese-like” formations, allowing for the rapid water movement between surface and groundwater aquifers. Because of this unique geology, pollutants can quickly move from the land surface, through the craggy and porous sediment and bedrock, and into the complex groundwater network below. In the karst region of Minnesota, nearly everyone relies on well water sourced from the area’s aquifers.
Answered by MCEA Project Manager Katie Cashman
In the karst region, groundwater is particularly susceptible to pollution because of the porous geology which allows for surface water to flow into groundwater sources quickly and easily. Scientists conduct a test called “dye tracing” to illustrate the rapid rate at which contaminants can move through the water. Contaminants in karst country travel between 60 to 90 meters from the point of injection within 1 to 5 days.The sensitivity of the karst to groundwater pollution has been well documented for three decades. The most recent data from Minnesota Pollution Control Agency shows that 16% of wells tested across Southeast Minnesota exceed the federal human health limit for nitrate of 10 mg/L. In some townships, such as Utica and Fremont, over 40% of wells tested exceed the human health limit for nitrate.
Answered by MCEA Water Program Director, Carly Griffith
The primary source of nitrate pollution in southeast Minnesota is industrial agriculture – specifically excessive nitrogen from commercial fertilizer and animal manure that is applied to cropland. Nitrogen is a nutrient that comes in many different forms and exists in the atmosphere, in our soils, and in the water. When applied at reasonable rates, nitrogen is a critical nutrient for plant growth. However when it is applied to soils it is converted to nitrate, an inorganic form of nitrogen that is dangerous for human health, as well as the health of fish and other aquatic life. Commercial fertilizer contains an inorganic form of nitrogen and manure contains mainly an organic form. When manure is applied to land, the organic forms of nitrogen are converted to nitrate by bacteria in the soil. For both commercial fertilizer and animal manure, excess nitrate leaches through the soil into the groundwater. In areas of the state that are heavily drain tiled like the Minnesota River Valley, agricultural drain tile carries nitrate to streams and rivers. In fact, nitrogen from cropland groundwater and agricultural drain tile accounts for more than 70% of the nitrogen found in Minnesota’s waters.
While organic nitrogen is a primary nutrient for plant growth, nitrate is dangerous for public health, as well as the health of fish and other aquatic life. As we’ve seen industrial scale agriculture balloon over the past 30 years–most evident in the growth of animal feedlots and the row crop production of corn–we’ve watched nitrate levels rise to crisis proportions in certain regions of our state.
Today, there are approximately 24,000 feedlots in Minnesota. Large Concentrated Animal Feeding Operations (CAFOs), which are feedlots with 1,000 or more animal units (one animal unit is the equivalent of a 1,000 pound animal like a heifer or a cow/calf pair) are just 4 percent of feeding operations in Minnesota, but they produce nearly a third of the manure. And the number of CAFOs in Minnesota continues to rise: in fact it has tripled since 1991.
Row crop agriculture also dominates the agricultural landscape in Minnesota. Minnesota currently has 20 million acres of cropland (nearly half of Minnesotan land) of which 15 million acres are used for corn and soy crops. These corn and soy crops are largely used for biofuels and animal feed, not human consumption. Environmental impacts worsen when we convert natural grasslands and wetlands to row crop agriculture. In 2015 scientists documented that the most dramatic period of Minnesotan land conversion was the 250,000 acres of Minnesotan grasslands, forests and wetlands converted to corn and soy cropland between 2008 and 2013, largely driven by federal biofuels incentives. Corn requires high nitrogen inputs (through manure and commercial fertilizer) so cropland expansion across the state means that more nitrogen is being applied to the landscape.
Answered by MCEA Director of Strategic Litigation Leigh Currie
The federal safe drinking water limit for nitrate was set at 10 mg/L in 1962, in response to research that documented that increased levels of nitrate can lead to methemoglobinemia, also known as blue-baby syndrome. Blue-baby syndrome occurs when nitrate limits the ability of blood to carry oxygen, thus causing the skin to turn blue and potentially leading to serious injury or death. While 10 mg/L may be the threshold for blue-baby syndrome, more recent research has concluded that nitrate levels below the regulatory limit may still present health risks such as a variety of cancers in adults, in addition to other pregnancy/birth complications like spontaneous abortion, fetal death, premature births, low-birth weights, and congenital malformations.
Answered by MCEA Supervising Attorney Joy Anderson
Based on a 2020 study by the Environmental Working Group, over 500,000 Minnesotans are exposed to high levels of nitrate in their drinking water–in both public water systems and private wells. In the karst region, approximately 380,000 area residents drink from private wells or public water supplies that are highly vulnerable to nitrate contamination. Data from Minnesota state agencies shows that approximately 16% of wells tested in Southeast Minnesota exceed the human health standard of 10 mg/L. In some townships like Utica and Fremont, over 40% of wells tested exceed the limit.
The pervasiveness of nitrate contamination in private wells is not fully documented as only a fraction of private wells have been tested. Our partners, the Minnesota Well Owners Organization, run well-testing clinics throughout the karst region, educating private well owners on how to take care of their water and ensure that they have safe drinking water. If the groundwater is polluted, then MNWOO can provide advice and resources for treatment.
Click here to find out more on the Minnesota Well Owners Organization webpage
Answered by MCEA Director of Strategic Litigation Leigh Currie
We are calling on the state regulatory agencies to treat the drinking water crisis with the urgency it deserves. We are asking for the Minnesota Pollution Control Agency to regulate feedlot and manure management practices in a way that prioritizes public health. A Minnesota Department of Agriculture survey revealed that almost three-fourths of farmers did not know how much nitrogen their manure contained, a basic requirement for good manure and fertilizer management. The same survey showed that almost two-thirds of farmers apply manure in the fall, a practice that increases the risk of nitrogen and phosphorus loss from manured fields.
Solutions include banning fall and winter application of manure on fields, limiting the expansion of large feedlots (CAFOs) through animal unit caps at the local level or location restrictions and expansion limitations in the state feedlot rules, and providing incentives for small and medium-sized feedlots to improve manure storage capacity and practice manure composting. Additionally, planting cover crops in fall and winter reduces pollution from manure, but is drastically underused.
Agricultural Drainage
Answered by MCEA Water Program Director, Carly Griffith
Drain tile is an agricultural land management practice where perforated pipe is installed below the soil surface on farm fields to lower the water table and drain “excess” water to nearby ditches and eventually to streams and rivers. Minnesota has over 20,000 miles of ditches and channelized streams and many thousands more miles of subsurface drain tile, though the total number is unknown.
Answered by MCEA Water Program Director, Carly Griffith
Drainage systems can, and have, significantly impacted Minnesota’s rivers, lakes, and streams in ways that have led to increased erosion and downstream floods, increased nutrient loads from cropland runoff, and the destruction of thousands of acres of wetlands, along with their critical ecosystem functions. The Minnesota Pollution Control Agency has reported that agricultural drainage accounts for an estimated 37% of nitrogen contributions to surface waters statewide in an average precipitation year and 43% in a wet year.
When people think about drainage, they sometimes think that the damage has already been done, since the state was extensively drained from the late 19th through the 20th century to transform marshy wetlands areas into productive cropland. But in fact, the impacts of drainage on our public resources continue to intensify. For example, since the early 1990s flow volumes in the Lower Minnesota River have more than doubled: this has led to severe erosion in the Minnesota River Valley that has destroyed homes and led to the loss of historically productive cropland. In large part because they have been heavily drain-tiled, streams in the Greater Blue Earth River basin are on the state impaired waters list for high turbidity (TSS)–a key test of water quality–and fail to meet water quality standards that protect fish, insects, and other aquatic life.
Answered by MCEA Water Program Director, Carly Griffith
Luckily, there are multiple ways to design drainage systems to treat and reduce nitrate pollution. Those include controlled drainage systems that increase water retention and storage within the soil profile, which can reduce the total drainage volume and associated nutrient loads from tile-drained agriculture. Specific practices like two-stage ditches and denitrifying woodchip reactors have proven particularly effective to treat nitrate pollution from agricultural drainage water. Without a broader investment in practices like these, we will not meet our nitrogen reduction goals laid out in our State’s Nutrient Reduction Strategy. That means we will continue to put public health and aquatic life in Minnesota at risk, and contribute to the dead zone in the Gulf of Mexico.
Answered by MCEA Director of Strategic Litigation Leigh Currie
There is currently a lot of activity around new proposed drainage projects in Minnesota. This is because older drainage system infrastructure are starting to deteriorate, more land is going into monoculture crop production, and climate change is increasing the frequency and intensity of precipitation. This means that right now we have a critical opportunity to create more transparency in the drainage process and rethink how to design drainage projects in a way that balances agricultural production needs with the equally important needs to improve water quality, protect downstream landowners, and enhance natural resources. MCEA is working with partner organizations to modernize public notice for proposed drainage projects, address stream degradation from the cumulative impacts of drainage projects in the Minnesota River Valley, and integrate water quality concerns more meaningfully into drainage project review.