Module 8: Open Feedlot Construction and
Management for W ater and Air Quality Protection
By Jeff Lorimor, Iowa State University
Intended Outcomes
The clientele will
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Know whether their lots are CAFOs.
Understand how moisture affects dust emissions.
Understand how lot design affects water and air quality.
Become better feedlot managers environmentally.
Contents
1. Introduction
2. Regulatory Considerations for Water Quality
3. Runoff Control and Management
A. Sedimentation Structures
B. Containment Structures
4. Air Quality
A. Open Lot Design
B. Open Lot Maintenance
C. Stocking Density
D. Open Lot Surface Amendments
E. Sprinkling
F. Manure Stockpiles and Composting Operations
G. Mortality Management
5. Summary
6. References
7. Questions
Reviewers
The author wishes to thank Dave Schmidt, University of Minnesota, and Ron Sheffield, University of
Idaho, for their review of this module.
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Introduction
Open lots, or feedlots, are broadly defined as any outdoor facility where livestock are fed and the lot
area is devoid of vegetation. Local regulations often do not specify the facilities that operators of outdoor
paved and earthen lots for animal confinement need to control water pollution. However, feedlot
operators are responsible for maintaining the quality of ground or surface water near their operations.
Because uncontrolled feedlot runoff can be a source of significant water pollution, operators must
minimize potential pollution problems by designing, constructing, and managing appropriate rainfall
runoff systems. In addition to protecting water quality, operators must protect air quality. Odors and dust
are the primary air contaminants arising from feedlots. This module will discuss both water and air
quality issues relative to open lots.
Regulator y Considerations for Water Quality
The Environmental Protection Agency's (EPA’s) new concentrated animal feeding operation (CAFO)
rules are the guiding regulation for open lots. These federal regulations define a CAFO as a feedlot with
the capacity of 1,000 beef animals, 700 dairy cows, or 2,500 swine over 55 pounds. However, many states
have regulations that meet or exceed the federal regulations. To obtain environmental permits, feedlot
operators must follow their state's regulations, restrictions, and design specifications. Some types of
regulations that apply to CAFOs are as follows:
 Runoff from CAFOs may not discharge to waters of the United States except if the facility is
permitted and when there is a storm event greater than a 25-year, 24-hour storm.
 Minimum distances are specified between the lots and wells, reservoirs, or rural water lines.
 Rates of manure nutrient application to cropland or pasture must be based on agronomic rates.
 Records must be kept about manure application locations and rates applied.
 Records must be kept about the manure storage structure or treatment system. (CAFOs must keep
records for 5 years.)
 All storm water diversion devices must be inspected weekly.
 Depth markers must be placed in all surface and liquid containment structures.
 Mortality must not be disposed of in liquid manure storage structures.
Feedlot operators should check with state and/or federal regulatory authorities to determine which
feedlot regulations are applicable for their particular situation.
Runoff Control and Management
Livestock housed in open lots should not have direct access to lakes, creeks, or streams. Regardless of
size, lots should not drain directly into road ditches, creeks or streams, drainage ditches, tile surface inlets,
or other channels because of the pollution potential. Once water is concentrated into a channel, it will
rapidly reach “waters of the state.”
The two basic types of runoff control options are containment and discharge. Containment or nondischarge runoff control systems collect and hold all runoff from the feedlot for application on land
owned or contracted by the feedlot operator. Discharge runoff systems are designed to release the runoff
(usually after some treatment) to adjacent land. In either case, frequent cleaning of open lots and proper
application of this solid manure onto cropland or pasture will reduce the nutrients in the runoff, and
hence, its pollution potential.
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Federal regulations require runoff containment systems for operations defined as CAFOs (e.g., 1,000
head of beef cattle). Most containment systems include a method for separating the liquids and the solids.
The solids are deposited in a sedimentation structure that allows the liquid to drain from the solids. The
solids are then removed and applied to land as fertilizer. The majority of plant nutrients leaving the
feedlot are found in the solids. The liquid portion of the runoff drains from the sedimentation structure
into a containment structure. The captured liquid is later pumped onto cropland or pasture at proper
nutrient management rates.
Regulations for non-CAFO feedlot operations are different for each state. However, all feedlot
operations should have a sedimentation, or settling, structure as a minimum control measure even if there
are currently no regulations on runoff control. While these structures have different names in different
states, they all have the same purpose: to remove solids from the liquid runoff stream.
Sedimentation Structures
Sedimentation structures, also called debris basins, settling basins, settling channels, etc., are used to
separate feedlot runoff solids from feedlot runoff liquids before the liquid is discharged into an infiltration
pond, holding pond or lagoon, or grass filter strip. Settling structures are relatively inexpensive. Often the
earth removed to construct a sedimentation structure is used to construct mounds and establish proper pen
drainage. Normally, the trapped sediment will contain about 50% of the nitrogen leaving the open lots.
Unless specified by state regulations, the sediment structure should be sized to contain 1/3 to 2/3 of the
runoff volume generated by a 25-year, 24-hour storm. Sediment basins should not capture and retain
runoff; they should just slow it down and then release the liquid to a containment structure or to a
treatment area (some state regulations may differ). Sediment basins should be cleaned frequently and
managed so that the captured solids dry out as quickly as possible, facilitating their removal in
preparation for the next storm. Porous outlets should be unplugged soon after rainfall events (even while
runoff is still occurring) to allow rapid drainage and drying. Liquids left standing in settling areas increase
the risk of water pollution should another runoff event occur prior to cleaning and drying.
To summarize, it is important to remove solids from settling areas. Solids should be scraped and
removed as soon as possible after runoff events so the settling structure is ready for the next event. Most
of the manure nutrients from feeding operations are in the solids, whether scraped during routine
maintenance or settled from runoff. After settling, the runoff liquid contains only a small portion of the
total nutrients but has high enough concentrations of pollutants to cause serious water quality problems.
Containment Structures
Proper management of the total runoff containment structures present at some feedlots is extremely
important. Poor management increases the risk of an accidental spill that can have disastrous
environmental effects. In humid areas, the most important management task is making sure the basin is
pumped out before it overfills and overflows. Containment structures are designed to hold a predetermined amount of runoff, depending on the local climate and the planned pumpout schedule. They must be
pumped out when they still have enough capacity to hold the runoff from the design storm. By law, large
lots (CAFOs) should always have the capacity to hold the runoff from a 25-year, 24-hour storm. Containment basins should have a depth marker that shows when the liquid level reaches the pumpout elevation.
Other management demands include checking the structure for any leakage through the berm, keeping the
banks mowed, watching for rodents or rodent holes, and controlling bank erosion, both inside and outside
the basin. Of all of these, timely pumpout is the most important.
Air Quality
Dust and odors are the two primary air quality contaminants from feedlots. Emission of these two
contaminants is controlled primarily by the moisture content of the feedlot surface. Dust is the pre-
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Dust/Odor Potential
dominate problem at low moisture content, and odor at high moisture content, so minimizing both dust
and odor by moisture management alone is impossible. Researchers have found that when the moisture
content of the open lot surface is between 25% and 40%, both dust and odor potential are at manageable
levels (Figure 8-1). In the optimum moisture range of 25% to 40% (wet basis), other properties such as
manure depth, bulk density, and texture become the most important determinants of dust and odor
potential.
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Dust Pote ntial
Odor Pote ntial
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Figure 8-1. Conceptual, qualitative relationship between dust potential and odor potential as a function of the
moisture content of an open lot surface
Animal feeding operations (AFOs) are subject to several layers of air quality regulations. Congress
has delegated the authority to regulate sources of any air quality impairment to the EPA. In turn, the EPA
has delegated the responsibility to the states. Some states have adopted additional air quality regulations
that are more stringent than the federal standards. Municipalities and other local units of government may
also impose air quality standards that exceed federal and state requirements.
The most important principle of odor control is to avoid anaerobic (contains no oxygen) conditions by
keeping
 Manure and other organic materials as dry as practical.
 Manure storages and surfaces exposed to oxygen.
 Open lot surfaces hard, smooth, and free of loose manure.
Open Lot Design
The key to improving air quality from open lots is the proper design and maintenance of these lots.
Moisture control is the primary factor in minimizing odor, gas, and dust emissions. Although some
moisture is beneficial as a means of controlling dust, excessive moisture will lead to odor problems and
excessive emissions of ammonia and other gases. Therefore, open lots must be designed to reduce the
ponding of water on the lot and the buildup of manure along fence lines and bunk areas. These design
parameters include:
 Slope surfaces between 3% and 5%.
 Slope lots that minimize pen-to-pen drainage.
 Convenient access to the open lots for manure removal.
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Using open lot soils that are firm, stable, and not easily eroded.
Maintaining a supply of fill soil for filling low spots and correcting ponding problems.
Designing pens that are conducive to edge-to-edge manure removal.
Choosing a site or constructing a berm to prevent temporary flooding.
Diverting clean water from lots.
Constructing mounds to avoid moisture collection around the base (construct parallel to slope).
Open Lot Maintenance
No matter how well an open lot AFO has been designed, lot maintenance will make or break the AFO
with respect to air emissions. The following management recommendations assist in water quality
protection as well as odor and dust reduction. The key is to keep the lot surface hard, smooth, and as dry
as possible, maintaining a firm 1- to 2-inch base of compacted manure above the mineral soil. The general
approach to dust control consists of (1) removing dry, loose manure from the lot surface; (2) manipulating
the moisture at the lot surface to achieve optimum moisture content; and (3) attempting to reduce peak
cattle activity during the critical late afternoon hours.
Frequent, proper manure harvesting
Remove loose material on lot surfaces; maintain a compacted layer of manure 1 to 2 inches thick.
Frequent harvesting of loose, dry manure from the feedlot surface improves manure quality for land
application and reduces the amount of material that may be pulverized and suspended in the air by hoof
action. Open lot dairies are frequently capable of daily manure removal while the cows are in the milking
parlor. However, daily manure removal may be too frequent, especially if manure removal equipment
cannot be adjusted to maintain a 1- to 2-inch layer of compacted manure above mineral soil. Weekly
manure removal may be a better option, both operationally and economically.
In earthen beef cattle feedlots, on the other hand, manure removal typically occurs only after each lot
of cattle is emptied for slaughter or transfer, an interval of 120 to 180 days. In flat feedlots or where
rainfall is plentiful, an interval of 120 days or more between manure removal activities will almost
certainly lead to lot conditions that generate odor. A few modern, large (capacity > 35,000) feedlots in
Texas have experimented with continuous manure harvesting in which two or three tractors with box
scrapers operate continuously across the yard, even with cattle present. Lot conditions are excellent, and
managers report little to no depression in feed-to-gain performance or increased cattle stress.
Operator training in manure-harvesting objectives and techniques
As with any essential AFO function, employees need to be trained both in the techniques of manure
harvesting and in the justification, motivation, and objectives of the manure-harvesting function.
Machinery operators who understand both the “what” and the “why” will be more apt to make sound
decisions when managers are not around to answer questions.
Frequent inspection for and correction of pits, holes, and wallows
Bunk readers, feed truck drivers, pen riders, and nighttime security providers employed by a feedlot
or dairy should be trained and equipped to note pits and holes developing in the lots. Such lot damage
should be corrected with compacted fill dirt as soon as practical. Managers should assign high priority to
holes and wallows near water troughs and feed aprons, where spilled and excreted water may collect even
during dry weather.
Manure mounds for flat lots
The construction of manure mounds serves a threefold purpose: (1) a temporary storage for excess
manure; (2) a cattle refuge from muddy, wet, and cold conditions; and (3) a means of enhancing the
water-shedding efficiency of lots with little or no slope. Do not rebuild mounds with manure; use good
soil. However, manure may be temporarily pushed up on mounds to help it dry before it is removed.
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Mounds help with water quality issues and also enhance cattle performance, especially on flat lots in
humid climates. They should be located so that they run up and down the slope, not across it. Mounds
should extend onto feed bunk aprons so cattle do not have to wade through a pothole to get from the
apron to the mound.
“Pull” blade vs. “push” blade
It is physically more difficult to ensure that a pushed scraper blade (e.g., front-end loader) leaves an
even, smooth surface than a pulled blade (e.g., box scraper). Blades that gouge and scar the lot surface
reduce the lot’s water-shedding efficiency and puncture the anaerobic interface that is desired to prevent
leaching. If possible, use a box scraper to dress up and clean lots.
Rigorous maintenance of overflow waterers, misters, and water distribution systems
Water leakage in lots, near feed bunks, and near manure storage areas can contribute significantly to
odor. Feedlot employees should be trained to look for signs of leaky distribution systems and water
troughs.
Frequent inspection of fence lines for manure ridges, especially before rainfall events
The moist manure that accumulates under fence lines as a result of hoof action is a fertile breeding
ground for flies. When rainfall occurs, these ridges also function as dams, creating puddles and wet spots
that generate odors. Especially when rainfall is expected or when flies are becoming a major nuisance,
these ridges should be removed or knocked down and the manure spread out across the lot to dry.
Stocking Density
Stocking density (number of animals per unit of lot area) or its inverse, animal spacing, may be
adjusted to compensate for increases in net evaporative demand (evaporation depth less the effective or
retained precipitation), shifting the moisture balance in favor of dust control. Auvermann and Romanillos
(2000) evaluated this option experimentally on a commercial feedlot in the Texas Panhandle and found
that decreasing the cattle spacing from 150 ft2/head to 75 ft2/ head reduced net (measured less
background) PM10 (particulate matter < 10 microns in diameter) concentrations at the lot fence line by
about 20%. As daily net evaporation increases, the effectiveness of increased stocking density is likely to
decrease; furthermore, increasing the stocking density may induce behavioral problems and reduce
overall feed-to-gain performance.
Open Lot Surface Amendments
Open lot surface amendments are still in the experimental phase with respect to dust and odor control.
Crop residue mulches (waste hay, cotton gin trash) may cushion hoof impact and reduce the shearing that
causes dust, and they may decrease the net evaporative demand by storing additional water and reducing
evaporation rates. Resins and petroleum-based products, which have been shown to reduce dust emissions
significantly from unpaved roadways, may also be effective, although the continuous deposition of
manure on the lot surface suggests that these compounds would need to be reapplied frequently and
would therefore be cost prohibitive.
Sprinkling
Solid-set sprinkler systems are an effective but expensive means of dust control in cattle feedlots.
Research in California showed that interior lot dust concentrations increased 850% after sprinkler
operation was stopped for two days. Sprinkler systems require a great deal of site-specific design based
on seasonal water balance calculations, but in general, systems should have sufficient capacity to deliver
0.25 inch or more of water per day across the entire yard. Sprinkler patterns should overlap by 50% of the
diameter of throw, and sprinklers should be located so that their throw does not extend all the way to the
feed apron.
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Manure Stockpiles and Composting Operations
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If possible, avoid long-term stockpiling of manure. Unmanaged stockpiles will eventually
exclude oxygen, and even if the stockpiles are not odorous, old, stockpiled manure releases more
odor when land applied than manure exposed to oxygen. If stockpiling is necessary, minimize
stockpile size.
To avoid overheating, put manure up dry (< 45% moisture). When land applied, charred
stockpiles release intense, uniquely disagreeable odors.
Locate stockpiles and composting operations upwind relative to prevailing winds and the AFO
center. Because of the odor potential of stockpiles and storage areas, they should be located as far
upwind of the principal downwind property line as topography or other operational considerations
permit.
Provide supplemental carbon for composting. A proper carbon-to nitrogen ratio in a compost pile
or windrow encourages faster composting and reduces odors over the long term.
Mortality Management
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Carcasses should be quickly removed from lots and disposed of properly, especially in warm
weather.
Short-term mortality storage should not be visible from off-site or located near the property line.
Deads should be removed frequently. If rendering services cannot provide timely services,
another type of disposal should be considered.
Some beef feedlot operators are composting deads. Dead animal composting has been shown to
work well for poultry and swine, including large sows. Adequate cover, proper moisture, good
co-compost material, and timely turning or mixing result in odor-free, effective carcass
breakdown. Cover must be maintained deep enough to control odors and prevent predators from
disturbing the carcasses.
Summary
Open feedlot management that minimizes water and air pollution requires continuous, conscientious
efforts by all personnel associated with the lot. In addition to good location and adequate runoff control
facilities, keeping the lot clean, firm, and dry are the key elements to having an environmentally friendly
lot. Timely pumpout of runoff holding basins is the most important element of preventing water and air
pollution in humid areas.
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References
Auvermann, B.W., and A. Romanillos. 2000. Effect of increased stocking density on fugitive emissions
of PM10 from cattle feedyards. Presented at the International Meeting of the Air and Waste Management
Association, Salt Lake City, UT, June 18-22.
Romanillos, A. 2000. Assessing the effect of stocking density on fugitive PM10 emissions from cattle
feedyards and development of a cattle feedyard emission factor. M.S. thesis, Texas A&M University,
College Station.
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Questions
1. At what capacity do feedlots become CAFOs and thus subject to EPA regulations and NPDES
criteria?
Answer: 1,000 head of beef cattle, 700 head of dairy cows
2. Where are most of the nutrients from a feedlot found? Runoff water or solids? (circle one)
Answer: Solids
3. How should mounds run on a slope? Across the slope or up and down the slope? (circle one)
Answer: Up and down the slope
4. Increasing lot surface moisture helps control dust. (True or False)
Answer: True
5. Increasing lot surface moisture helps control odor. (True or False)
Answer: False
6. It is good to let manure accumulate to more than 2 inches in depth on the feedlot surface. (True or
False)
Answer: False
7. What is the optimum moisture range for feedlot surfaces?
Answer: 25%-40%
8. What kind of blade best scrapes feedlot surfaces? A pull blade or a push blade? (circle one)
Answer: Pull blade
9. Can a 1,500-head beef feedlot legally discharge runoff water after settling solids? (Yes or No)
Answer: No
10. To minimize water and air pollution, it is important to keep feedlot surfaces clean, firm, and dry.
(True or False)
Answer: True
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