Water Protection Program fact sheet
Division of Environmental Quality Director: Kyra Moore

The clean out and removal of dry process waste from storage structures at animal feeding operations (AFO) does not always occur at times that are best for land application, because of weather or cropping practices. A common practice is to store or stockpile dry process waste (also referred to as dry litter or solid manure) at sites until weather or cropping practices allow for land application.

Dry process waste is defined as a process waste mixture which may contain manure, litter or compost (including bedding, compost, mortality by-products, or other raw materials which is commingled with manure) and has less than 75% moisture and does not contain any free- draining liquids. Dry process waste is primarily associated with poultry operations but can also come from swine, beef or dairy cattle operations. Lagoon sludge can be stockpiled if it has less than 75% moisture and does not contain any free-draining liquids.

Dry process waste can develop free-draining liquids, called leachate, over time as precipitation and clean stormwater runoff that infiltrates into the stockpile adds liquid. Precipitation and stormwater runoff that comes into contact with a stockpile by running through or around it is then contaminated stormwater. The contaminated stormwater and leachate must be contained and not allowed to be discharged across property boundaries or into waters of the state.

Preventing the contamination of clean stormwater and containment of contaminated stormwater can be accomplished through the use of best management practices (BMPs). BMPs can be structural or non-structural measures that are used to control pollutants and prevent discharges. Nonstructural BMPs are operational procedures and management decisions that are intended to reduce the risk of a problem developing. These include limiting the amount of dry process waste stockpiled, and the location and placement of a stockpile. Structural BMPs are devices that are installed or constructed to control runoff such as berms, covers, and straw bales. Proper management and maintenance of stockpiles is the responsibility of the property owner the stockpile is located on. 

This guidance identifies laws and regulations applicable to stockpiles and BMPs that can be implemented to help prevent a discharge. The laws and regulations applicable to a specific stockpile are based on where the dry process waste originated and where the stockpile is located.

Statutes Applicable to All Stockpiles

Stockpiles of silage and other feed stocks are also subject to these laws.  Missouri Revised Statute 644.051.1(1) pertains to discharges of water contaminants.  A discharge from a stockpile in a location where it is likely to reach waters of the state is a violation. Once a discharge crosses a property boundary it is no longer contained by the responsible property owner and is considered a violation of state law.

Regulations for Stockpiles at Permitted Operations

Missouri Revised Statute 644.051.1(2) regulates water contaminants that have entered waters of the state and exceed water quality standards. The general criteria for water quality standards are set by the Missouri Clean Water Commission and are listed in 10 CSR 20-7.031(3). These standards are applicable to all waters of the state at all times. A discharge to waters of the state that prevents it from meeting the general criteria is a violation.  Specific criteria, such as that for ammonia, are listed in 10 CSR 20-7.031(4), may also be violated by a discharge from a stockpile. 

The regulations in 10 CSR 20-8.300(10) (B) apply to stockpiles of dry process waste that originated from a permitted operation that are stockpiled at a land application area. A land application area is defined as agricultural land under the operational control of the Concentrated Animal Feeding Operation (CAFO) owner or operator, whether it is owned, rented, or leased, to which manure, litter or process wastewater from the production area is or may be applied. For these stockpiles, the regulation requires the following BMPs to be implemented:

  • Any temporary stockpiles need to be placed in locations that prevent stormwater from draining into or through the pile. If stormwater does drain through the pile, a one foot berm is must be placed on the up-slope side of the pile to divert clean stormwater runoff.
  • No location shall be used for stockpiling for more the two weeks unless the pile is covered.
  • Setback distances shall be maintained between the stockpile and certain features as follows:
    • 300 feet from any losing stream, well, sinkhole, water supply for human consumption, non-owned dwelling or residence, public building, or public use area.
    • 100 feet from any intermittent or permanent flowing stream.
    • 50 feet from public roads and property lines.
  • Stockpiles shall not be placed on slopes steeper that 6%.
  • No stockpile shall be larger than two acres in size.
  • All piles shall be placed so as to minimize forming pockets, hollows, or mini-dams that would collect and hold water. The desirable design is one pile with an angle of repose so that it forms a crust and will tend to shed water off the pile. If there are two or more stockpiles, they should be placed far enough apart that they do not trap and hold water.

In addition, temporary stockpiling of uncovered dry process waste within the production area without runoff collection is prohibited. Application of manure, litter, or process wastewater including stockpiled dry process waste at land application areas shall be done in accordance with the operations nutrient management plan and the Missouri Concentrated Animal Feeding Operation Nutrient Management Technical Standard (NMTS).

Optional BMPs for Use at Any Stockpile

While the BMPs listed above are required for stockpiles at permitted operations, they should be considered for use at all stockpiles. The optional BMPs listed below can further reduce the risk of a discharge from stockpiles. Many of the BMPs listed can be easily implemented at little or no cost.

Stockpiles should be placed on well vegetated, elevated areas so as to receive little or no runoff.

The same site should not be used more than two years in a row. After two years the site should be used for row crop, hay or pasture to remove nutrients for at least one year before placing another stockpile at that site. The amount stockpiled at one area should be able to be land applied within six months.

Stockpiles should not be located in areas subject to flooding or on soils that have bedrock within 40 inches of the surface. This includes soils that are very shallow, shallow or moderately deep. The base of the stockpile should be at least two feet above the seasonal high water table.

If the stockpile is covered with tarps, plastic sheeting or other impermeable material, the covers should be anchored or weighted down to prevent blowing and damage.

Place a berm or other form of diversion on the upslope side of the stockpile to divert clean stormwater runoff away from the stockpile.

Driving over stockpiles with equipment or vehicles will compact the dry process waste and will help the pile to shed water and reduce infiltration.

If the stockpile develops free-draining liquids, additional material such as wood chips, straw or rice hulls, can be added to absorb the leachate. Straw bales, silt fence or a berm can be placed below the stockpile to contain the leachate. A vegetative buffer down slope of the stockpile will slow down the runoff and allow for better infiltration.

Inspections of the site should be conducted on a regular, routine basis and especially after precipitation events that produce runoff. Items to check include the stockpile for free draining liquids, structural BMPs for any damage and for any discharges. Maintenance and repair of structural BMPs should be conducted as soon as possible after any damage is discovered.

Consider developing a nutrient management plan for all land application fields. Application rates should be calculated annually and not exceed the planned crops’ nutrient requirements based on soil test results, manure analysis and realistic yield goals. When manure is obtained from a permitted operation, the recipient must be provided with a copy of the most recent manure analysis and a copy of the NMTS.

While the use of any BMP by itself or a combination of BMPs does not guarantee that a discharge resulting in a potential violation will not occur, they do provide protection to prevent a discharge.   

There is no requirement to obtain an operating permit for stockpiles if they are not part of an operation that already requires a permit; however, the Department can require an operating permit for a stockpile site if necessary to protect waters of the state. This could include stockpiles with ongoing or recurring violations.

Nothing in this document may be used to implement any enforcement action or levy any penalty unless promulgated by rule under chapter 536 or authorized by statute.

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