United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory
Ada OK 74820
Research and Development
EPA-600/S2-83-079 Nov. 1983
v>EPA Project Summary
Evaluating Swine Drylot
Runoff Impact on a Coastal
Plain Stream
James C. Barker, Frank J. Humenik, Michael R. Overcash, and Steve W. Tedder
The objectives of this study were: 1)
to establish sampling methodologies
for intensive monitoring of the environ-
mental impact of animal feedlot runoff
on in-stream water quality, 2) to
determine chemical changes in stream
water quality as a result of rainfall
runoff from swine drylots on deep
sands by comparing these resultant
stream concentrations with those from
a background reach of stream, and 3) to
determine any changes in the stream
biota as a result of the drylot runoff.
A drylot unit was selected for investi-
gation which annually markets approxi-
mately 4000 hogs on dirt lots with deep
sandy soils and which typifies physical
and management factors common to
Coastal Plain swine production. Stream
samples were collected at sites above,
adjacent to, and downstream of the
drylots and analyzed for chemical
oxygen demand (COD), total Kjeldahl
nitrogen (TKN), nitrate-nitrogen (NO3-
N),total phosphorus (TP), and chlorides
(Cl) over a 40-month period. These
measurements as well as dissolved
oxygen (DO) and stream flow were
taken under low-flow conditions by
grab sampling techniques while stream
samples were collected under rainfall
conditions by instrumented sampling
stations. Biological surveys of the
stream flora and fauna were also
conducted. These results are discussed
as well as the study approach, site
selection, and sampling methodologies.
Field results indicated that approximate-
ly 2% of the nutrient and organic load of
the defecated swine wastes are trans-
ported from the sandy drylot surface
during rainfall runoff. The constituent
levels of this lot runoff are further
reduced 20- to 40-fold by swamp and
vegetative buffer filtering action prior
to stream input. Background stream
constituent concentrations were very
similar to levels measured in geographic-
ally similar well-drained Coastal Plain
watersheds. Nutrient levels, except for
phosphorus, below the drylot were
similar to background levels under low-
flow conditions. Nitrogen and chloride
stream levels were approximately
doubled by rainfall runoff from the
drylot while phosphorus was elevated
approximately 5-fold. Despite these
nutrient level increases, however, no
significant alteration of the stream
biology was detected. It would appear
from this study that more emphasis
should be placed on the actual in-
stream biological changes that may
occur as a result of point-source and
nonpoint-source inputs to reinforce
conclusions drawn from nutrient and
organic measurements.
This Project Summary was developed
by EPA's Robert S. Kerr Environmental
Research Laboratory, Ada, OK, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Effluent from farm animal production
areas is proclaimed as a significant
contributor to surface water pollution.
Different climatic, geographic, soil, and
vegetative conditions, as well as manage-
ment practices, however, profoundly
affect the quality and amount of rainfall
runoff and resulting stream impact from
these animal production units. Concerns
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arise, then, over the implementation of
uniform national criteria for effluent
guidelines and limitations for concen-
trated animal feeding operations as
designated in the Federal Water Pollution
Control Act Amendments of 1972 and the
March 18, 1976 FederalRegister. Regula-
tory criteria should be responsive to the
needs and desire of the indigenous
population as it supports national goals.
The prudent balance between comprehen-
sive regulations and criteria that are
regionally responsive to both quality
environment and food production must
be maintained.
Decisions concerning control of rainfall
runoff from animal production units in a
specific location should include an
evaluation of whether the constituents
adversely affect the quality of a particular
receiving water. It would be a misuse of
resources to attempt complete control of
any of these sources where they do not
have an adverse effect or where such
control will not produce a positive effect
on water quality. Such decisions require
more factual information on the magni-
tude of the waste inputs to a stream, the
chemical and biological effects on in-
stream water quality, and benefits and
costs associated with control possibilities.
Open swine production facilities (drylots)
on soils not supporting vegetation are
classified as concentrated animal feeding
operations subject to the criteria outlined
in the National Pollutant Discharge
Elimination System (NPDES) guidelines.
Approximately 45% of the 3.1 million
swine in North Carolina are grown on
such drylot units since they represent
the minimum housing investment. A
large majority of these drylots are on deep
sandy soils in the Coastal Plain section of
eastern North Carolina. Since a producer
may be able to finish up to three times as
many hogs in an open lot system as he
could afford m confined housing, he may
have several hectares (ha) of drylots with
stocking densities ranging from 500-
1250 market hogs per ha. Stocking
densities in this range quickly denude lots
of vegetation and will eventually kill any
trees within the confined area. Manure
buildup and soil compaction are minimal
since animal activity tends to keep the
wastes well mixed with the sandy surface
of the well-drained soils.
Drylots are rotated after one year's
production to control disease and parasites
and to allow rejuvenation of the soil
surface. These lots are then seeded to
grasses or allowed to remain fallow for at
least 2 years before being put back into
production. Large swine drylots character-
istic of the Coastal Plain are usually
located on sloping topography but separated
from a drainageway or stream by a
wooded or vegetated buffer strip. These
streams are ill defined and often traverse
through low-lying wet areas. The actual
control of runoff contaminants is to a
large extent affected through proper site
selection and management practices.
The major objectives of this study were:
1. to establish sampling methodologies
for intensive monitoring of the envi-
ronmental impact of animal feedlot
runoff on in-stream water quality.
2. to determine chemical changes in
stream water quality as a result of
rainfall runoff from swine drylots on
deep sands by comparing these
resultant stream concentrations with
those from a background reach of
stream.
3. to determine any changes in the
stream biota as a result of the drylot
runoff.
Conclusions
The results of 40 months of intensive
field monitoring of a Coastal Plain stream
receiving rainfall runoff from a swine
drylot have indicated that although
stream nutrient levels are elevated
during rainfall events, the drylot is having
minimal impact on the receiving stream
biology.
1. Approximately 2% of the defecated
swine wastes is transported from the
sandy drylot surface during rainfall
runoff. Nutrient and organic constituent
levels of lot runoff are further reduced 20-
to 40-fold by swamp and vegetative
buffer filtering action.
2. Background stream constituent
concentrations were very similar to levels
measured in geographically similar well-
drained Coastal Plain watersheds. Nutrient
levels, except for phosphorus, below the
drylot were similar to background levels
under low-flow conditions.
3. Surface runoff and tile drainage
from row-crop land appears to have an
equal or greater impact on stream
nitrogen levels under low-flow conditions
than drainage from the swine drylot.
Nitrogen concentrations cycled seasonally
with peaks during the wet winter months
of low evapotranspiration and an additional
spike shortly after spring fertilizer
application.
4. Nitrogen and chloride stream levels
were approximately doubled by rainfall
runoff from the drylot while phosphorus
was elevated approximately 5-fold
Despite these nutrient level increases,
however, no significant alteration of the
stream biology was detected through
biological analyses.
5. Acquisition of flow data from
sluggish, unstable Coastal Plain streams
proved to be very difficult, costly and
time-consuming rendering the cost
benefits of obtaining such data question-
able.
6. Benefits have already accrued from
the cooperative effort of this investigation
with the state regulatory agency. It has
enhanced the working relationship
between educational and regulatory
agencies, and the livestock producer
resulting in more logical implementation
of regulations which are responsive to
local conditions and needs, yet compatible
with national water quality goals.
Major Findings
In-stream flow measurements proved
to be very difficult to obtain due to the
sluggishness and unstable organic
bottom of this Coastal Plain stream.
Consideration should be given in similar
related studies to the importance of mass
transport and just how flow data will be
used before expending the efforts neces-
sary to obtain such information.
Average and extreme constituent
concentrations are listed in Table 1 for
the primary sampling sites on the
receiving stream under low-flow conditions.
Only a very slight dissolved oxygen sag
occurs in the receiving stream at the point
of maximum drylot impact, but this DO
concentration recovers and exceeds
background levels through a downstream
reach. The minimum measured DO
throughout the 40-month period of study
was 4.0 mg/l which still met water
quality standards applicable to the
surface waters of North Carolina.
Highest stream total nitrogen levels,
particularly nitrate nitrogen, under low-
flow conditions were measured near the
headwaters. This was probably due to tile
drain inputs from an adjacent row-crop
field since a seasonal cycling trend
emerged with the nitrogen peak concentra-
tions occurring around January through
March with an additional spike in May.
This would indicate that during the
growing season nitrogen losses are
reduced due to crop uptake and less
moisture for soil-water transport, but
after harvest more nitrogen becomes
available due to residue decomposition
and less evapotranspiration resulting in
greater soil-water transport. The additional
spike m May occurs after spring fertilizer
applications. Nitrogen levels below the
drylot, although elevated, were still
comparable to a geographically similar
North Carolina watershed free of point
source inputs.
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Table 1. Mean Constituent Concentrations of Receiving Stream Under Lo w-Flow Conditions
Water Quality
Parameter
DO.
COD.
TKN,
NOa-N.
TP.
Cl,
Flow,
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
cfs
Sampling Site
Headwaters
4.3*
1.2-10.2"*
27.12
11.76-75.10
1.37
0.45-4.35
1.46
0.23-4.33
0.13
0.02-0.43
7.2
5.0-12.1
0.099
0.021-0.260
Background
6.2
3.2-11.9
23.02
3.93-49.43
1.11
0.34-4.97
0.27
0 -2.00
0.07
0.02-0.15
5.9
4.0-8.5
0.207
0.009-0.768
Below Drylot
7.0
4.0-12.1
44.80
15.81-100.97
1.73
0.49-5.55
0.49
0 -2.60
0.41
0.09-1.35
7.0
2.6-12.6
0.404
0.076-1.062
Recovery
9.4
6.1-15.2
39.48
15. 75-75. 10
1.60
0.42-6.20
0.50
0 -2.48
0.38
0.12-0.78
7.1
2.7-12.9
0.458
0.091-0.923
*Mean of approximately 50 sampling dates over a 40-month study period.
* Range of values.
Stream phosphorus levels were substan-
tially higher below the drylot under low-
flow conditions than background levels.
Visual inspection of the stream channel
indicates that most of the sediment
transported from the lot in runoff is
settled or trapped by a swamp buffer
before it reaches the stream. Organic
wastes leaving the lot surface probably
also settle in the swamp where the
phosphorus content of that waste is
gradually and continually released to the
stream through drainage and subsurface
flow.
The average coefficient of variation for
organic, nitrogen, and phosphorus stream
levels during individual rainfall runoff
events was 30%. Table 2 gives the mean
constituent concentrations of the receiving
stream as well as drylot runoff under
rainfall runoff conditions. Organic concen-
trations of lot runoff decreased by
approximately 20-fold when compared to
stream concentrations indicating the
filtering capability of the swampy buffer.
In terms of mass transport based on five
runoff events, approximately 2% of the
wastes defecated by the animals actually
left the lot surface during runoff.
Total nitrogen levels of lot drainage
during rainfall runoff events decreased by
40-fold when compared to stream levels
indicating the effects of swamp filtering,
denitrification, and stream dilution. Total
N stream levels below the drylot were ap-
proximately double background levels.
Stream phosphorus levels during
rainfall runoff indicated a 40-fold decrease
in the lot runoff levels. An average
phosphorus stream concentration of 0.74
mg/l below the drylot represented a 6-
fold increase over background levels.
Biological surveys of stream periphyton
and stream benthos under low-flow and
rainfall runoff conditions yielded no
variations between sampling sites for the
specific biological evaluation techniques
employed in this study. Examination of
the biological data indicated that the
impact of drainage from the drylot on the
stream biota is minimal over the period of
time studied, however instream nutrient
and organic concentrations increased as
a result of drylot runoff.
Table 2. Mean Constituent Concentrations of Drylot Runoff and Receiving Stream Under
Rainfall Runoff Conditions
Water Quality
Parameter
COD,
TKN,
NO3-N,
TP,
Cl,
mg/l
mg/l
mg/l
mg/l
mg/l
Sampling Site
Headwaters
26.77*
3.90- 180.54*"
1.12
0.15-4.59
1.36
0 -3.70
0.10
004-0.50
7.76
3.00-14.40
Background
48.28
10.00- 166.03
1.46
0.45-4.88
049
0 -276
0.13
0.04-0.53
6.37
4.00-10.90
Below Drylot
78.08
29.00-577.00
2.61
0.75-21.01
1.77
0 -8.60
0.74
0.16-10.13
10.13
4.00-19.00
Drylot Runoff
1521.
403-3946.
105.
49 8-204.
7.25
0.03-26.80
31.00
8.40-54.00
96.6
50.6-169.
"Mean of approximately 40 rainfall runoff events over a 30-month study period.
**Flange of values.
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James C. Barker, Frank J. Humenik, and Michael R. Overcash are with North
Carolina State University. Raleigh. NC 27650; and Steve W. Tedder is with the
North Carolina Department of Natural Resources and Community Development.
Raleigh, NC 27611.
R. Douglas Kreis is the EPA Project Officer (see below).
The complete report, entitled "Evaluating Swine Dry lot Runoff Impact on a Coastal
Plain Stream," (Order No. PB 83-263 699; Cost: $ 13.00. subject to change) will
be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Robert E. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
GOVERNMENT PRINTING OFFICE 1983-659-017/7225
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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