and the North Carolina Swine Industry
March 10, 1995
Introduction
It is difficult to imagine any resource of more value to society than clean water. Reliable sources of clean drinking water are vital to the existence of any population. Yet particularly in a state like North Carolina, it is arguable that clean water provides more than physical nourishment, that clean water contributes to the character, to the nourishment of the collective soul of the state. What would North Carolina be, after all, without the cold, clean creeks and streams that tumble out of its mountains, without the rivers that snake across the Coastal Plain, without the mirror-smooth swamps that reflect ancient cypress trees, without sounds and estuaries or the surf that relentlessly pounds the state's coast?
Keeping the state's waters clean and providing for the well being of its human population--especially as that population grows--can be conflicting goals. Many of the activities we consider progressive--activities that provide jobs, for example--pose potential hazards to water quality. Indeed, even that most basic of activities, growing food, entails potential threats to water quality.
The following pages deal with water quality and a particular type of agriculture--hog farming. What follows is not a scientific report in the sense that it contains technical language and citations. Citations and technical language were intentionally omitted in an effort to promote better understanding of complex issues. But this report is scientific in that it is based on the carefully documented studies of experts on water quality and agriculture.
and water quality
There is no way around it, raising hogs entails water-quality challenges, particularly when hog farming is done on the scale typical of North Carolina. The state is the second largest hog producer in the United States. The swine industry is worth roughly $1 billion annually to North Carolinians.
And there is no way around the fact that hogs produce manure. The more hogs; the more manure. If manure is not managed properly, water supplies can be endangered. And in the process of raising hogs, some of the animals inevitably die. If dead animals are not managed properly, water quality can be threatened.
Nutrients in hog manure can contaminate both ground water--water that exists beneath the soil--and surface waters--streams, rivers, ponds and lakes. Bacteria and microorganisms from dead animals can contaminate ground water.
Any agriculture, no matter the type, must deal with nitrogen. This colorless, gaseous element, which most farmers refer to simply as N, is an essential nutrient for both plants and animals. In order to grow, plants and animals must consume nitrogen.
Nitrogen exists in the soil in various forms, including organic nitrogen, ammonium and nitrate nitrogen; it also exists in the atmosphere as a gas, making up close to 80 percent of the air we breathe.
Most plants get nitrogen from the soil, taking it up through their roots. Animals consume nitrogen in protein when they eat plants. Animals, however, cannot use all the nitrogen they consume. On North Carolina farms, hogs typically retain from 40-60 percent of the nitrogen they consume. The remaining nitrogen is excreted as urine and feces.
It is nitrogen and other nutrients such as phosphorus in swine manure that appear to pose the greatest potential threat to water quality from hog farming in North Carolina.
The presence of contaminants in water supplies is typically measured in parts per million, sometimes in parts per billion. A water sample can be analyzed, for example, to determine how many parts per million of nitrate nitrogen exist per one million parts of water. The allowable limit for nitrate nitrogen in a drinking water supply is 10 parts of nitrate nitrogen per one million parts of water. In surface waters that are not used as drinking water supplies, any measurement of nitrite nitrogen, another form of nitrogen, over one part per million is considered cause for concern.
manage manure
North Carolina farmers who grow hogs typically collect manure in lagoons outside the barns in which hogs are raised. In the lagoons, manure is degraded by anaerobic bacteria; carbon-containing compounds decompose and become carbon dioxide and methane; organic nitrogen is converted to ammonia and ammonium.
Farmers usually use lagoon liquid as fertilizer, applying it to fields. Using the liquid in this way takes advantage of the nutrients in the manure. The liquid from lagoons is a nutrient resource, and proper management and use of this resource can reduce the need for commercial fertilizers.
Ground water quality can be affected when soil below the root zone contains unusually high levels of nitrate nitrogen and other nutrients. In some circumstances, nitrate nitrogen can move through the soil and into ground water. If nutrients in ground water reach a well that supplies drinking water, they can pose a human health hazard. Nitrate nitrogen may also be carried by ground water to streams and lakes, where it can be an environmental threat.
Consuming nitrate nitrogen can alter the body's ability to transport oxygen, causing a condition called methemoglobinemia, also known as Blue Baby Syndrome. This syndrome can be fatal to infants.
While there has never been a documented case of Blue Baby Syndrome in North Carolina, some wells do exceed the drinking water limit of 10 parts per million of nitrate nitrogen.
The North Carolina Cooperative Extension Service has tested over 10,000 wells throughout the state. In some Coastal Plain counties, as many as 10 percent of the wells tested exceeded the 10 parts per million standard. It is not clear that hog farms contributed to this contamination. Indeed, when an effort was made in Sampson County, which has the largest swine population in the state, to determine the cause of well contamination, sources other than hog farming appeared to be at fault.
Perhaps a greater potential threat to North Carolina water quality is surface water contamination. Propelled by ground water, nitrate nitrogen can move through the soil and into surface waters such as streams, rivers, lakes and ponds. Nitrate nitrogen can also be carried to surface waters in surface runoff, the water that flows across the soil surface rather than seeping into the ground.
Phosphorus, which is much less soluble than nitrate nitrogen, does not move with ground water into surface waters. It can, however, be transported to surface waters by runoff, as can other sediments. Sedimentation, the contamination of surface waters by sediment carried by runoff, is widely regarded as the most serious threat to surface water quality in North Carolina.
High levels of nitrogen and other nutrients in slow-moving or stagnant surface waters can cause a phenomenon called eutrophication. The nutrients fuel the growth of algae, which consume oxygen in the water. As the algae die and decompose, even more oxygen is consumed. Without oxygen, fish and other marine animals die.
can affect water quality
Poorly managed swine-growing operations can pose a potential threat to water quality in two ways. If growers apply too much lagoon liquid to fields, nutrient levels in the soil can rise to unacceptable levels, threatening ground and surface water quality.
And studies done by agricultural engineers at North Carolina State University indicate that lagoon liquid can seep out of some older lagoons. Lagoons that pose a seepage threat were constructed before clay liners, which appear to provide sufficient seepage protection, were widely used.
The studies also found that an evaluatin of soil at a lagoon site, including a detailed analysis of several pits or borings, is essential to detect pockets of permeable soil that can result in seepage. Liquid seeping from a lagoon appears to pose a human health concern only if shallow drinking water wells are located immediately downhill from the lagoon. Ground water, like surface water, flows downhill, so liquid escaping from a lagoon will flow downhill away from the lagoon.
Lagoon-construction standards now in effect appear to offer adequate protection against seepage, while standards regarding lagoon siting and design appear adequate to ensure that lagoons do not leak. The North Carolina Cooperative Extension Service has since the early 1970s provided hog growers with the latest information available on proper lagoon construction.
North Carolina State University studies have also found that if ground water contamination occurs, it is likely to be confined to the surficial aquifer, the layer of ground water immediately below the soil surface. Most deeper aquifers beneath North Carolinar's Coastal Plain, where the state's hog farming is centered, are protected by a layer of dense clay. However, some Coastal Plain residents get their drinking water from shallow wells that draw from the surficial aquifer, so the threat to this water source should not be discounted.
Nitrate nitrogen levels in surficial aquifers below Coastal Plain agricultural fields that receive fertilizers or animal manure are often higher than may be considered desirable. How are these nitrate nitrogen levels affecting water quality?
The dense layer of clay between the shallow ground water of surficial aquifers and deeper aquifers appears to protect the deeper aquifers. Unable to move into deep aquifers, shallow ground water flows laterally toward surface waters such as streams.
Fortunately for North Carolina surface water quality, most of the state's streams are protected by riparian buffers. A riparian buffer is simply a strip of trees and other vegetation growing along the banks of a stream. Riparian buffers prevent most of the nitrate nitrogen in ground water from reaching surface waters. The plants that form a riparian buffer take up, or consume, some of the nitrogen. Most of the nitrogen, however, is denitrified by bacteria that live in the wet soil near a stream and feed on the dead roots of vegetation. These bacteria turn nitrate nitrogen into a gaseous form and release it into the atmosphere.
If nitrate nitrogen levels in ground water become too high, however, riparian buffers can be overwhelmed, and surface waters will become contaminated. It is not clear how much nitrate nitrogen is too much. Neither is it clear how much riparian buffer is necessary to protect surface waters from a given nitrate nitrogen level.
Riparian buffers seem clearly to be an important component of water quality protection. That does not mean, however, that these areas of vegetation should be relied upon exclusively to mitigate excesses elsewhere. The presence of riparian buffers notwithstanding, anyone who puts nutrients into the soil must do so in a responsible manner.
There is concern among scientists familiar with the North Carolina swine industry about the practice being adopted by many hog growers of raising beef cattle along with their hogs. Cattle are seen by many hog growers as an economical addition to their operations. Lagoon liquid is applied to fields, where it serves as fertilizer for pasture. Cattle are then grazed in the fields.
Scientists are concerned that with the lagoon liquid application rates now typically used by growers, grazing cattle does not remove an optimum amount of nitrogen from the land. While the forage being grown in the fields does take up and use nitrogen from the lagoon liquid, cattle then eat the forage and redeposit some of the nitrogen in the fields in the form of urine and feces.
While raising cattle and hogs may be problematic, it also appears it is possible to accommodate both types of livestock without threatening water quality. Agricultural scientists are looking at strategies to remove nitrogen from the land while leaving cattle on it. For example, making at least one hay crop from the pastures on which cattle are now grazed would remove a significant amount of nitrogen. And adjusting lagoon liquid application rates to account for the presence of cattle is an effective method of ensuring that adequate amounts of nitrogen are removed from the system.
Dead animals also pose a potential threat to water quality. Some North Carolina hog growers dispose of dead animals by burying them, and it is possible that decaying carcasses could contaminate ground water.
However, most of the larger hog growing farms in the state rely on rendering services, which make animal food from carcasses, to dispose of dead animals. It is thought that more dead animals are disposed of by rendering than in any other way. Composting carcasses also appears to offer a disposal alternative. North Carolina State University scientists and engineers are experimenting with this environmentally friendly management method.
It may be instructive in considering the effect of the North Carolina swine industry on water quality to look at Sampson County. Sampson and next-door-neighbor Duplin County are the two largest hog-producing counties in the United States.
The North Carolina Cooperative Extension Service in 1991 tested the water from 317 private water supply wells in Sampson County. Fourteen of the wells had nitrate nitrogen concentrations higher than the 10 parts per million standard. Further investigation of these 14 wells revealed that in no case could the contamination be traced to a lagoon or animal feeding and housing facility. All of the contaminated wells were shallow, and most of the contamination was due to faulty well construction. In some cases, the wells were near septic lines, and the septic systems were thought responsible for the high nitrogen levels.
It is perhaps of note that portions of the Black and South rivers that flow through Sampson County were classified in 1994 as Outstanding Resource Waters by the North Carolina Division of Environmental Management. Only waters that have been tested for biological and chemical contamination and have been shown to be of excellent quality may be designated Outstanding Resource Waters.
The designation helps maintain water quality. New or expanded wastewater discharges from industry are not allowed in Outstanding Resource Waters, while new urban development activities within the watershed of Outstanding Resource Waters must limit density or use storm water control systems to manage storm water runoff.
North Carolina State University scientists have done studies in Sampson County and elsewhere aimed at determining the effect on water quality of putting different amounts of lagoon liquid on the land. While such studies are useful, they are not enough.
A better understanding of what happens to nutrients within entire watersheds, not just the relatively small plots of land that happen to be hog farms, is necessary if effective water quality protection strategies are to be developed. It is important, for example, to know the origin within a watershed of nitrogen and other nutrients. Hog farms are not the only source of nitrogen. The commercial fertilizers applied to fields contain nitrogen and other nutrients, as does the waste water from residential septic systems. Fertilizer is also applied to residential lawns, other landscaped areas and golf courses, all of which are sources of nitrogen and phosphorus.
It is also important, if strategies that protect ground water while also fostering economic activity are to be developed, to determine the nutrient load a given watershed can carry and to better understand the ability of riparian buffers to remove nutrients. Research at North Carolina State University is moving toward answering these questions.
Scientists at North Carolina State University and elsewhere are also looking at other methods of dealing with nutrients. Constructed wetlands, which transform nutrients in much the same way as riparian buffers, may offer one method of dealing with excess nutrients. Ongoing research also indicates that using lagoon liquid to fertilize hardwood forests may hold promise.
It may be possible to harvest nutrients from hog manure. Research just getting underway is aimed at understanding the formation of a substance called struvite, a salt that forms in wastewater handling systems. Struvite is usually considered a nuisance but has value as a slow-release fertilizer. It is conceivable that struvite could be harvested somewhere along the hog growing waste stream.
to protect water quality
Natural Resources Conservation Service standards concerning siting, soil types and construction appear adequate to prevent high seepage rates from lagoons. These standards play an important role in ensuring the integrity of lagoons. But just as important is the quality of lagoon constuction. Growers and others who build lagoons must pay careful attention to the quality of lining materials used in lagoons if high seepage rates are to be prevented.
Regulations became effective in 1993 that require growers to adopt whole-farm waste management plans. Plans must be approved and certified by a technical specialist.
The nutrient management portion of a waste management plan must specify how manure is to be stored, how much manure is to be applied to fields, the nutrient content of the manure, the crops to be grown on the land where it is applied, and rates and timing of application. Growers must also provide a vegetative buffer at least 25 feet wide between streams and fields to which manure is applied.
These manure management requirements are an important component of efforts to protect water quality.
It seems clear there is much to be learned about the effect of large hog farms on water quality. It is vital that research continue in this area. An annual research update would serve to keep growers and policy makers informed of the latest research.
and water quality?
Clearly, raising swine can pose potential threats to water quality. However, it is the prevailing opinion of agricultural scientists familiar with the large hog farms typical of North Carolina that it is possible for this important industry to exist while also protecting water quality.
It should be understood, however, that there are limits to the number of animals that can be produced within a given watershed without unduly threatening water quality. Only through solid research can we determine what these limits are and how they may be affected by improved agricultural management practices.
It is important also to understand that technology and knowledge alone are not enough to protect water quality. Hog growers arguably play the most important role in protecting water quality. The actions of growers--how well they manage their farms--ultimately determine whether water quality is endangered. We must, therefore, make every effort to make sure growers are aware of and encouraged to adopt improved manure management methods as they become available.
related to water quality and the swine industry
(Title, Investigators)
Selection of Plants for Constructed Wetlands for Wastewater Treatment, J. M. Stucky
Management of Animal Waste in Support of Sustainable Agriculture and Water Quality, P. W. Westerman
Genesis and Hydrologic Characteristics of Soils on the Piedmont Coastal Plain Fall Line (subsurface movement of waste), H. J. Kleiss
Groundwater Contamination Potentials of Agricultural Practices, R. L. Huffman
Environmentally Compatible Nursery Crop Production Practices (wastewater runoff and water quality), T. E. Bilderback
Functional Development of Constructed Wetlands and Coastal Dunes, S. W. Broome, E. D. Seneca
Watershed Management Strategies to Protect Water Quality, G. D. Jennings
Interactive Effects of Water Table Management and Fertilization on Water Quality, R. W. Skaggs , J. P. Lilly
Cumulative Impacts of Land Use and BMPs on Water Quality in Coastal Watersheds, R. W. Skaggs, J. P. Lilly
Molecular Phylogenetic Survey of Mehanogens in Waste-Treatment Systems, T. T. Brown
Predicting Nutrient Release from Food and Animal Waste Products, R. L. Mikkelsen, A. G. Wollum
Livestock and Poultry Manure Nutrient Assessment and Distribution in North Carolina, J. P. Zublena, J. C. Barker
Managing Pasture and Hay Fields Receiving Nutrients from Anaerobic Swine Waste Lagoons, J. P. Mueller, J. P. Zublena, M. H. Poore, J. C. Barker, J. T. Green, Jr.
Effect of Level of Nitrogen from Swine Lagoon Effluent on Forage Characteristics, Water Quality and Animal Performance, R. W. Harvey
Constructed Wetlands for Swine Wastewater Treatment, F. Humenik, S. W. Broome
Riparian Buffer Zones To Protect Water Quality, F. Humenik, M. Rice
Evaluation of Animal Waste Management Practices, T. Hoban, et. al.
Evaluation of Ground Water Impacts of Established Anaerobic Lagoons, R. L. Huffman, P. W. Westerman
Deep River Nonpoint Source Phosphorus Reduction Project, G. D. Jennings
Ground Water Impact of Irrigation of Swine Lagoon Effluent on Sandy Soils with High Water Table, P. W. Westerman
Recovery of Solids from Flushed Swine Manure for Utilization, P. W. Westerman
Investigation of a Seepage Plume from a Swine Waste Lagoon, R. L. Huffman
governing animal waste management systems
The following comparison of rgulations governing animal waste management systems in the Southeast was prepared by Jeri Gray of the Water Resources Research Institute of The University of North Carolina
Federal regulations under the Water Pollution Control Act prohibit discharge of wastes to waters of the U.S. without a permit. These regulations designate "concentrated" animal feeding operations as point sources of wastewater discharge subject to the National Pollutant Discharge Elimination System (NPDES) permitting program. A "concentrated" operation is defined as one with at least 1,000 animal units (about 2,500 swine larger than 55 pounds each) maintained for 45 days or more in a nonvegetated area. Regulations specifically state that discharge from animal feeding operations of any size to waters of the U.S. is prohibited except in the case of the 25-year, 24-hour storm, and that if there is a continuous discharge from an animal feeding operation, the operation shall be required to obtain an individual NPDES discharge permit. However, there are no provisions for NPDES discharge permits for animal feeding operations, so, in effect, no discharge from animal feeding operations is allowed. All state regulations of animal feeding operations are built on these minimum federal requirements.
Until recently most states dealt with discharges from animal feeding operations on a case-by-case basis. If investigation following a fish kill or citizen complaint documented a discharge from a feeding operation, that operation would be "designated" as a "concentrated" animal feeding operation subject to NPDES permitting requirements and would be required to implement (or upgrade) some form of waste management system (typically a lagoon) that would prevent all discharges except in the case of the 25-year, 24-hour storm. This kind of after-the-fact regulatory scheme, dependent as it was on citizen complaints, was not useful for preventing discharges, and in fact, amounted most of the time to no regulation. Indeed, regulatory agencies did not even have records of the numbers, sizes or locations of animal feeding operations.
As animal operations, particularly swine operations, grew in size and in number across the Southeast, the threat to water quality, drinking water sources and human health from these operations increased. Therefore, in the last few years, many states have adopted supplemental regulations through which they may more directly and systematically address the potential for water pollution from animal operations. This analysis compares animal waste management regulations in four Southeastern states experiencing substantial growth in large-scale animal operations: Georgia, Virginia, South Carolina, and North Carolina.
The general features of all the state animal waste management regulations examined are similar. First, they are all implemented cooperatively by a state regulatory agency in cooperation with an agency that provides technical assistance--either the federal Soil Conservation Service (now Natural Resources Conservation Service) and/or state soil and water conservation agencies and/or the Cooperative Extension Service (see following table). The degree to which states rely on the Soil Conervation Service and the Cooperative Extension Service for technical assistance and the degree to which they involve soil and water conservation districts in program implementation varies.
Another common feature of state programs is that they all set a size threshold below which operations are regulated much less stringently, although the size threshold varies considerably (see following table). In North Carolina, Virginia and Georgia, operations under the threshold size are still dealt with on a case-by-case basis. These smaller operations are required to have facilities that prevent discharge except in the case of the 25-year, 24-hour storm and are encouraged to use best management practices in the disposal of animal waste. However, they are not required to register and unless there is a reported discharge, they are, for all practical purposes, unregulated. In South Carolina, smaller operations are required to have the same permits as the larger operations, but the permit requirements are different.
The basic requirements of the four state programs are also similar. Each includes some mechanism (registration or permit application) for obtaining information on the location and size of operations and for obtaining from the operator assurances that technical requirements are being met. Essentially, animal operations are required to have a waste management plan which includes a properly designed and constructed waste lagoon and a plan for applying waste to appropriate crops at rates which assure the uptake of nutrients by plants. (Although land application of wastes is not always required, it is usually the only feasible method of disposal.)
No two states examined use the same regulatory mechanism, although the result is similar.
Virginia has recently developed a General Permit under which animal operations above the threshold size may be permitted. Between 1989 and 1994, Virginia had required individual nondischarge permits for animal operations above the threshold. However, the individual permitting process was felt by the regulated community to be cumbersome and time consuming, so the General Permit was developed and became effective in November 1994. To be permitted under the General Permit, an operator must submit a registration statement along with certification of its Nutrient Management Plan from the Department of Conservation and Recreation and, for new operations, notification from the governing body of the county, city or town where it is located. The General Permit is good for a maximum of 10 years. In Virginia, about 75 animal operations (including dairy, beef, swine and poultry) have been permitted under individual permits and the General Permit.
In Georgia, an operation with more than 2,500 swine each weighing 55 pounds or more that uses land application must obtain a Land Application System Permit. The LAS Permit application must include a letter from the Soil Conservation Service concurring with the design of the wastewater disposal system and a copy of the approved plans and specifications. The LAS Permit is good for a maximum of 5 years.
In South Carolina, which has been actively regulating all confined animal operations since 1956, animal waste lagoons are defined and regulated as treatment plants. All lagoons must have a Permit to Construct, with existing ones permitted on an as built basis. All lagoons must obtain a Permit to Operate. In order to obtain the permits, the applicant must have a Waste Management Plan designed and developed by the Soil Conservation Service or a professional engineer. Operations larger than 2,500 swine must have an expanded waste management plan, the requirements for which are decided on a case-by-case basis (with some designedto address odor concerns). A current issue facing the South Carolina program is permit renewal. State regulations provide that permit holders must reapply for permits (even permits to construct) every five years; however, the regulation has not been enforced. Officials are now considering whether to begin enforcing the requirement in order to capture expanding operations. South Carolina has issued 2,731 permit numbers, but officials estimate that only about 2,000 of these applications have resulted in permits to construct.
North Carolina requires that all operations with 250 or more swine register and submit certification that they have implemented a Waste Management Plan based on specifications in the SCS Field Office Technical Guide Section IV (or BMPs adopted by the N.C. Soil and Water Conservation Commission). The Soil and Water Conservation Commission designates technical specialists who may certify compliance with design and construction criteria and certify Waste Management Plans. Soil and Water Conservation Districts review the certification and it is filed with the N.C. Division of Environmental Management. North Carolina's regulations were implemented in 1992 with a phase in for existing systems so that all systems larger than 250 swine must be registered and certified by Jan. 1, 1997. So far, 2,512 swine operations with more than 250 swine have registered in the state.
North Carolina, Georgia, and South Carolina require that waste management systems be designed in accordance with the SCS Field Office Technical Guide. SCS Standard 312 defines and describes the purpose and components of a Waste Management System and principles of agricultural waste management. SCS Standard 359 contains minimum acceptable requirements for design, construction and operation of waste treatment lagoons. Some requirements are: locate lagoons a minimum distance of 300 ft from dwellings (750 ft for new operations); do not locate in floodplain unless protected from inundation by the 25-year frequency flood; locate on slowly permeable soils and avoid gravelly soils and shallow soils over fractured or cavernous rock; if self-sealing is not probable, use a synthetic or packed-soil liner; provide storage for the 25-year, 24-hour storm; follow specific loading guidelines for the geographic region. SCS Standard 633 includes guidelines for waste utilization or what may be called nutrient management. These guidelines recommend waste and soil analysis to determine application rates and provide tables for determining application rates for various crops.
There are additional requirements contained in each state's regulations, including, in some cases, ground water and surface water monitoring requirements. Virginia's General Permit includes specific requirements for animal waste management systems including lagoon siting and construction, buffers and monitoring. State technical requirements are summarized in the following table.
Some state programs include requirements for public notification or comment on permits for new facilities. Georgia provides a 30-day public comment period on proposed Land Application System Permits. In South Carolina, any property owner whose property lines are less than 1,000 ft from a proposed site is notified of the proposed permit and must consent in writing to new lagoons.