The increasing concerns of groundwater pollution

Posted 5/18/22

High school intern, Washington Conservation District We all want clean water. In Washington County, 100% of drinking water and water used for irrigation comes directly from groundwater, so it’s …

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The increasing concerns of groundwater pollution


High school intern, Washington Conservation District

We all want clean water. In Washington County, 100% of drinking water and water used for irrigation comes directly from groundwater, so it’s important that it remains clean and plentiful. Clean groundwater is also crucial to the ecological communities surrounding our lakes and streams. What can community residents do to maintain a healthy groundwater supply?

Water Education Senior Specialist at Washington Conservation District, Angie Hong, presented on May 2 to the Afton Planning Commission on the importance of maintaining a healthy groundwater supply and the main concerns that face Afton. Most issues covered weren’t just of concern for Afton but also other cities in Washington County. While cities need to encourage and enforce the best groundwater practices, there are many actions community residents can take to help protect groundwater.

First, to help something, you have to know what it is. What is groundwater? Most of us have seen the brightly colored cartoon images with a giant blue pool underneath the city or a field where all of our water supposedly comes from. In reality, there isn’t a swimming pool of water underneath our backyards. Groundwater is the water held underground in pores and rocks.

Sandstone layers create aquifers because it is a porous rock, meaning it holds water and protects it from contamination. Then, a layer of limestone blocks water, acting as a divider between sandstone aquifers. In southern Washington County, where Afton is located, there is karst topography, meaning that there are fractures in the limestone that allow the water to travel quickly between aquifers instead of the water being soaked into sandstone and held. The karst topography creates the streams and springs in Washington County and creates all the beautiful, natural, water-filled areas that we all love.

At the May 2 session, the Afton Planning Commission learned that the regional aquifer is at risk of overuse and contamination. Afton’s planning commission was concerned about how the nearby larger cities affect their groundwater supply. Wells pump groundwater from the sandstone aquifers, creating a cone-shaped zone around the well. The cone’s point is where the well pumps water from, and because the water pressure pulls water to the pump, the groundwater is lower around the site. Larger cities, such as Woodbury, which has 19 wells, drain the groundwater supply for nearby cities and towns. While Woodbury needs those wells to meet the demand of people and companies in the city, Afton is vulnerable to a lower groundwater supply. The process of pumping groundwater also spreads pollutants.

Three main pollutants threaten Afton’s groundwater and provide an opportunity for individuals to help protect their water. Nitrate levels have been rising for years, and roughly 10-20% of the private wells in nearby Cottage Grove and Denmark Township have nitrate levels above the health risk limit established by the Minnesota Department of Health. Nitrate levels increase because of improper well construction and the overuse and improper disposal of fertilizers. To help decrease nitrate levels, the Minnesota Department of Agriculture (MDA) restricts fertilizer application during the fall and on frozen ground. The MDA and the Washington Conservation District are working with local farmers to develop nitrogen best practices. Community residents can help by reducing the amount of fertilizer used on lawns and gardens. For lawns, Minnesota Extension recommends only one application of slow-release nitrogen fertilizer around Labor Day.

There are also high levels of E. coli in Valley Creek, which recently caused the stream to be added to Minnesota’s impaired water list. E. coli is a bacteria found in human and animal feces. Watershed managers don’t yet know the source of E. Coli in Valley Creek but previously determined that E. Coli in nearby Kelle’s Creek is caused by failing septic systems in the surrounding watershed. Washington County requires compliance inspections for septic systems when a property is sold, or a landowner can request an inspection to determine if their system is functioning properly.

Additionally, Hong talked about the growing risk of chloride contamination from road salt and water-friendly landscaping options, including planting native plants, which help filter pollutants from stormwater and runoff before reaching the groundwater supply. The Afton Planning Commission requested that Hong provide them with contacts in the county, watershed district, and the state to follow up with. The group will discuss potential policies the city could enact to address groundwater pollution concerns. Humans and animals all need clean water. Therefore it’s important for individuals, companies, and organizations to reduce their pollution.