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Importance of Manure Application Setbacks for Protecting Private Drinking Water

By Danielle Rhea

In Pennsylvania, all farms or landowners that have livestock, horses, poultry, or other farm animals that produce manure or that apply manure to fields or pastures are required to follow manure management regulations.  Farms classified as either concentrated animal operations (CAOs) or concentrated animal feeding operations (CAFOs), which typically have more animals and/or a higher density of livestock are required to develop more detailed nutrient management plans. While there are differences in the specific requirements between manure management and nutrient management regulations, there are several similarities, one of which is following manure application setbacks from environmentally sensitive areas on and around the farm. The purpose of this article is not to delve into the details of the regulations, but instead to provide perspective on the importance and purpose behind some manure application setbacks, specific to private drinking water resources. For more specific information on manure and nutrient management regulations in Pennsylvania, visit the Pennsylvania Nutrient Management Program Webpage.

Many wells in Pennsylvania lack sanitary construction. Photo: Danielle Rhea, Penn State

Manure is made up of many valuable components for growing crops and improving soil health, such as organic matter and nutrients.  While these components are beneficial in agricultural settings, they are considered harmful in water resources. In surface waters, extra nutrients can cause excessive algae growth and reduced dissolved oxygen. In groundwater or surface water used for drinking water, extra nitrogen and bacteria can harm human health. Consequently, manure application setbacks are required for a variety of environmentally sensitive areas meaning that it is mandatory to stay a certain distance away when applying manure near surface water and groundwater resources.

Generally speaking, setbacks of at least 100 feet are required for environmentally sensitive areas. In some cases, setbacks around surface waters (streams, lakes, ponds, etc.) and sinkholes can be reduced depending on what management practices may be in place. For example, setbacks around surface waters can be reduced to 35 feet if there is a permanent vegetative buffer in place because of the ability of vegetation to filter runoff and take up nutrients. However, on no occasion can the setback between manure application and private drinking water wells or springs be less than 100 feet. Setback distances are explained in Pennsylvania Manure Application Setbacks and Requirements.

We often think of groundwater as being safer than surface water because the water in our aquifers first flows through many layers of soil and rock, filtering out many surface pollutants. Unfortunately, it is more complicated than that. Springs are particularly vulnerable to surface pollutants because they are formed from very shallow groundwater and there is less filtration happening between the soil surface and the groundwater. As far as wells, you can think of drilling a well as piercing a hole in the ground, creating a shortcut from the ground to the aquifer. Water always takes the path of least resistance, and a large hole in the ground is much easier for runoff to flow down compared to filtering through the soil. You may be thinking that a well is more than just a hole in the ground, that there is a casing and (hopefully) a cap.  While that should be true, sadly, it takes more than a cap and casing to prevent runoff from impacting a well, and many Pennsylvania wells are not constructed in a sanitary way.

A major challenge for private water system users in Pennsylvania is that there are no statewide private water system regulations. This means that private well and spring owners are voluntarily responsible for managing their water supply. The lack of statewide requirements means that many wells or springs may be poorly constructed, may not be maintained over time, and may have never been tested to see if the water is safe to drink. While not required in Pennsylvania, sanitary well construction is an important step for preventing surface contamination of wells and involves the following five components:

  1. The well casing extends about one-foot above the ground.
  2. The well casing continues down to bedrock.
  3. The ground around the wellhead slopes away from the wellhead.
  4. A grout seal pumped into the entire space between the casing and outside of the borehole.
  5. A sanitary, water-tight, vermin-proof well cap.

There are over one million private water wells being used by farms and rural residences in Pennsylvania and only about 20% are considered to have sanitary construction. Consequently, establishing a wellhead (or spring) protection area is essential for preventing surface water contamination of groundwater aquifers and observing the 100-foot manure application setback is crucial for reducing nitrogen and bacteria contamination of wells and springs on and around farms.

Another important consideration is that groundwater moves below ground in a downward direction. Aquifer contamination upslope of a well may eventually reach downslope wells over time. Neighboring wells, unproperly abandoned wells, and sinkholes may all be susceptible points in the landscape where contamination could occur and affect downslope users. It is best practice for wells to be located at least 100 feet from the property line; however, the lack of regulations means that this is not always the case. While it can be a challenge to locate wells on adjacent properties, manure application setbacks still apply. Likewise, abandoned wells are not addressed in all regulations but it would also be best practice not to apply manure within 100 feet of an unproperly abandoned well because it could share an aquifer with an active water well.  Finally, sinkholes provide a direct connection between the surface and groundwater, which is why manure application setbacks are also required for these sensitive areas.

For manure, nitrates  and bacteria  are the primary contamination concerns in drinking water because both can cause health issues. It is important to note that elevated levels of nitrates and bacteria may also be caused by unmaintained or failing septic systems. Neither of these contaminants are easily detected by the water's appearance, smell, or taste, meaning that testing would need to be done in order to know if a well has excess levels. If a well is contaminated by nitrogen or bacteria, there are several treatment options for removing either of these contaminants; however, all water treatment systems will have lifelong maintenance and expense. Therefore, preventing contamination is a better long-term solution than maintaining water treatment over time. Proper well construction, creating a wellhead or spring protection area (including observing manure application setbacks), maintaining septic systems, and regular water testing are some of the steps that private water system users can take to help safeguard their drinking water.

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