Water Protection Program fact sheet
Division of Environmental Quality Acting Director: Steve Feeler

Concentrated Animal Feeding Operations (CAFOs) in Missouri must meet protective design criteria that exceed design standards in federal regulations for manure storage facilities. Planning ahead and being prepared for these situations is paramount. The Missouri Department of Natural Resources has prepared this wet weather management guide to aid producers in decision making and planning. With due diligence and guidance, agricultural producers can make good decisions during adverse weather patterns that protect water quality. While this guidance has provisions for land application practices that are not typically allowed, there shall be no discharge as a result of these applications from land application fields.

At times, operators are faced with precipitation events that exceed the design criteria for their operation. Persistent heavy rain coupled with cool weather during a cropping season can create many challenges for livestock and poultry operations. Even under normal weather conditions, time is often limited for land application after fall harvest or before spring planting and wet weather tends to aggravate this situation.

During wet weather periods, CAFOs may experience high manure storage levels for extended periods of time. This can leave the environment and the CAFO at substantial risk of spills or overflows from uncovered liquid manure storage structures and these discharges must be prevented.

Good communication is also extremely important. Producers, integrators, environmental consultants and private land-application companies are all encouraged to work together, communicate and be accommodating. In addition, communication between department staff and permittees is highly encouraged and important. Producers should contact their Missouri Department of Natural Resources’ regional office to discuss solutions. The department is well equipped and ready to assist and guide CAFO operators to find solutions that ensure water quality is protected.

The department has site-specific CAFO NPDES permits and two CAFO general permits, a NPDES (MOG01) permit and the state no-discharge permit (MOGS1). Both permits have provisions for the implementation of the wet weather practices included in this publication.  MOGS1 permittees are not allowed to discharge.  NPDES permits allow for a discharge from an uncovered liquid storage structure when the criteria for a chronic weather event or catastrophic storm have been met and the operation has been maintained in accordance with permit conditions. However, this discharge shall not cause a violation of water quality standards. NPDES permitees must notify the department at least 24 hours in advance of implementing wet weather practices. Producers are encouraged to review their permit frequently and understand the requirements. Both permits are available at the department’s CAFO website at http://dnr.mo.gov/env/wpp/cafo/.

The wet weather management practice provision states:
“A chronic weather event is a series of wet weather events and conditions that can delay planting, harvesting, and prevent land application and dewatering practices at wastewater storage structures.  When wastewater storage structures are in danger of an overflow due to a chronic weather event, CAFO owners shall take reasonable steps to lower the liquid level in the structure through land application, or other suitable means, to prevent an overflow from the storage structure.  Reasonable steps may include, butare not limited to following the Department’s current guidance (PUB2422) entitled “Wet Weather Management Practices for CAFOs”.  This guide was designedspecifically to help minimize or eliminate water quality impacts from CAFOs during extreme wet weather periods. The Chronic Weatherdetermination will be based upon an evaluation of the1 in 10 year returnrainfall frequency over a 10-day, 90-day, 180-day, and 365-day operating period.”

The Missouri Climate Center will determine, within a reasonable timeframe, when a chronic weather event is occurring for any given county in Missouri. The department’s regional offices will be notified when a chronic weather event or catastrophic storm has occurred. These practices are intended to help minimize or eliminate water quality impacts from an overflow of an uncovered liquid storage structure during extreme wet weather periods. Once the liquid level in the storage structure is below the upper pump down level, land applications are to resume under normal conditions.

Wet Weather Management Practices

1.   Avoid allowing a lagoon or storage structure to overflow. Overflowing effluent can be highly concentrated and may cause a fish kill when it enters a stream or pond. Additionally, overflows may compromise the structural integrity of a lagoon’s berms, which may result in a more catastrophic discharge.

2.   Do not lower manure storages by pumping or siphoning wastewater directly onto the ground surface or into a stream. Such activity is a violation and subject to enforcement action regardless of the circumstance. In addition, do not attempt to increase lagoon storage levels by sandbagging or raising lagoon berms.

3.   Apply effluent to frozen or saturated soils, if necessary to prevent a lagoon from overflowing. Note: Surface application of manure to frozen, snow-covered or saturated soils during normal weather conditions is prohibited by the Concentrated Animal Feeding Operation Nutrient Management Technical Standard (NMTS) found on the departments CAFO website at www.dnr.mo.gov/env/wpp/permits/nutrient-management-tech-standard.pdf. The NMTS is incorporated into state CAFO regulations.

4.   Applying effluent fields used for hay or pasture is preferable to reduce runoff potential. If hay or pasture land is not available, apply to fields with high levels of crop residue. For better access to wet fields, fill tankers to less than full capacity to reduce weight.

5.   Fields that are owned, leased, or rented by the CAFO owner that are suited for land application may be used, even if the land is not in the operations nutrient management plan. Applications to these fields under this guide must follow all relevant Best Management Practices in the nutrient management plan, NMTS and permit. Keep complete records of all applications on those fields and submit them on a separate sheet with the annual report. Application to fields not owned, leased or rented by the CAFO owner is considered a manure transfer and records of the transfer are to be kept.

6.   Increase separation distance as much as possible between application areas and water ways, streams, lakes, etc. Required minimum separation distances for normal land application events are:

7.   Use land with the least slope to minimize runoff potential. Seek fields or even parts of fields with two percent slope or less. Avoid areas subject to flooding, have shallow groundwater tables.

8.   Application rates should be reduced to decrease runoff potential. Irrigation equipment should be calibrated and operated in a manner to ensure even distribution of applied wastewater. Surface applications less than 0.25 inches per pass and gun travel speeds of five feet per minute or more may be necessary.

9.   Monitor the pumping operation continuously to minimize runoff potential or equipment malfunction. Frequently observe points of potential runoff around the perimeter of the land application field. No discharge shall occur as a result of land application.

10. If overflow from a lagoon or runoff from land application does occur, start emergency secondary containment procedures by constructing berms or a dam to prevent wastewater from entering surface waters.

11. Report to the department all discharges of manure or process wastewater to waters of the state no later than 24 hours after becoming aware of the discharge. Record and maintain reports of the date, time, location, duration and estimated volume. To report a discharge, contact the department’s nearest regional office or the 24-Hour Emergency Response Line at 573-634-2436.

Record keeping is always recommended and is required for all permitted operations. During times of unusual weather, it is particularly important to be thorough about keeping complete precipitation, manure storage level and land application records.

Missouri Department of Natural Resources’ Regional Offices