oEPA
United States
Environmental Protection
Agency
Office of Water
Washington, DC 20460
July 1987
Nonpoint Source Pollution
Control: a Guide
Executive Summary
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Executive Summary
Nonpoint Source Pollution
Control: a Guide
U.S. Environmental Protection Agency
Criteria and Standards Division
Washington, DC
1987
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Prepared under contract 68-01 -6986 for the U.S. Environmental Protection
Agency. Research and technical information by Battelle Columbus Divi-
sion; reviewed by Criteria and Standards Division, U.S. Environmental
Protection Agency. Manuscript and design by JT&A, Inc. Approval for
publication does not signify that the contents necessarily reflect the views
and policies of the Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or recom-
mendation for use.
PHOTOGRAPHS: The Federal Highway Administration, the National Ag-
ricultural Library, and the Soil Conservation Service and Forest Service
of the U.S. Department of Agriculture.
COVER ART: David Stolar.
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Contents
Foreword v
Introduction 1
Evaluation of Modeling and Other Assessment Techniques ... 3
Best Management Practices 13
Agriculture 15
Urban and Construction 21
Silviculture 25
Mining 29
Multicategory 31
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Foreword
The Guide to Nonpoint Source Pollution
Control is a user's guide to the techni-
ques now available for controlling non-
point source pollution. This Executive
Summary provides a detailed outline of
the Guide. It is intended for the decision-
maker who is knowledgeable enough
about nonpoint source pollution to
choose the appropriate computer model
and/or BMP without a great deal of ex-
planation.
The Executive Summary contains
source addresses for model information,
model documentation, and floppy disk
copies of models where available. Also in-
cluded are the figures and tables from the
Guide, as well as several of the illustrating
photographs. All endnotes and bibliog-
raphic material, however, remain in the
Guide only and can be researched in that
book. The Executive Summary does in-
clude the glossary of terms for quick
reference.
As the Guide to Nonpoint Source Pollu-
tion Control is a practical guide for the
water professional and State and local
decisionmaker, so the Executive Sum-
mary to the Guide comprises an overview
for quick reference to the information in
the Guide.
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Introduction
Under the Clean Water Act of 1972 this Nation
has made steady progress toward its national
water quality goals. By regulating the disposal of
municipal and industrial waste (point sources),
we have been controlling and decreasing pollu-
tion from waste that continually pours from pipes.
Less obviously, nonpoint sources land, fields,
and streets contribute considerably to our waters'
pollution. While pollution from pipes is continuous
and easily identifiable, nonpoint source pollution
is extremely variable, occurring only during
precipitation events.
Rain washes pollutants from our land into our
water. Understanding the relationship between
hydrology and the variability of the specific cir-
cumstances is the key to understanding nonpoint
source pollution. While it may not lend itself to
traditional collection and discharge control
methods, nonpoint source pollution can be
analyzed statistically. And that analysis can point
the way to solutions.
The water professional's first task is to educate
his public. The terms "runoff1 and "nonpoint
source pollution" must become as familiar to the
citizen as "sewers" and "pipes." Citizens must un-
derstand that runoff originates in their yards, on
their farms, and in their streets, and that when
they change some of the ways they do things,
they prevent this pollution. The widespread insis-
tence on nonphosphate detergents is an example
of public acceptance of such a challenge.
Backed by a knowledgeable public, State and
local governments can develop management
strategies to control nonpoint source pollution.
Agricultural pollutants are the most pervasive,
with urban sources next in importance. In addi-
tion, runoff from highways and waste disposal
sites, failed septic systems, mining and logging
activities, and construction sites contribute to the
Nation's water pollution.
Pollutants carried by these nonpoint sources
can be grouped by source and effects:
Sediments resulting from erosion (of both
cropland and streambanks), livestock activities
and construction site runoff comprise the greatest
volume by weight of materials transported.
Fertilizers, phosphorus and nitrogen, are
found in both point and nonpoint discharges, and
are largely responsible for accelerating the aging
and decay (eutrophication) of lakes and streams.
Pathogenic (disease-bearing) microor-
ganisms may be introduced from agricultural
sources such as livestock feedlots and from leaky
septic tank systems and leach fields. These
microorganisms may encourage the spread of in-
fectious diseases, eventually creating a major
public health problem.
Pesticides, herbicides, metals, and other
toxics, particularly from agriculture, silviculture,
mining, and lawn and landscape care not only
threaten surface water but are also being found
with increasing frequency in ground water. In
northern climates, trace contaminants and road
salts also contribute to the pollution.
Studies demonstrate that controlling nonpoint
source pollution produces economic benefits
beyond the obvious relationship between ap-
parent lake water quality and its use by swimmers
and boaters. For example, farmers can reduce
cultivation costs by using conservation tillage;
with preventive methods such as tillage, com-
munities can cut dredging costs and improve
recreation.
Even beyond the economic benefits are the
health benefits that result from nonpoint source
pollution control. Historically, we know that dis-
eases can travel almost invisibly through drinking
water that is drawn from ground water.
The goal here is to give the water professional
at the State and local level an outline of the most
effective technical solutions so that he is able to
move fast, backed by an informed public, to
reduce nonpoint source pollution of our surface
and ground waters.
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Evaluation of Modeling and
Other Assessment Techniques
This section identifies criteria for selecting and
evaluating decisionmaking tools, and describes
the most useful categories for managing nonpoint
source pollution. Emphasized are techniques that
Account for the role hydrology plays in in-
fluencing pollutant behavior.
Address spatial and temporal variability in
pollutant generation, transport, and
delivery.
Relate contaminant concentrations and
loads to best management practices
(BMPs).
The nonpoint source assessment techniques
either employ statistics or deterministic models to
simulate the transport process. They use
hydrologic characteristics to estimate pollutant
delivery to receiving waters from land use in
agricultural, silvicultural, construction, mining,
and urban areas.
The information developed from these techni-
ques can be used to identify the environmental ef-
fects of nonpoint source pollution.
PHYSICAL MODELS
Nonpoint source models are divided into two
categories physical and decision-oriented (see
Figure 1). Physical models predict runoff and
mass transport. They are based on deterministic
or stochastic simulation of the physical processes
(physical, chemical, and biological) involved. The
methods can range from simple techniques that
estimate average annual pollutant loadings to
ones that predict detailed temporal and spatial
distribution of pollutants.
Physical models do not need address every
parameter that affects water quality. Users may
modify and adapt them to specific cases, and
may use them to link a specific loading rate of
pollutant to different receiving water bodies.
DECISION-ORIENTED MODELS
The decision-oriented techniques assume
relationships between BMPs and water quality,
approach ecosystems and watersheds as an in-
tegrated whole, and in a few instances, permit a
benefit/cost evaluation of BMPs. Many of them
are modifications of physical models, which are
process oriented, simulating hydrologic;
transport; and other physical, chemical, and
biological processes.
Selecting the Right Model
The decisionmaker's specific requirements deter-
mine how any model, or combination of models,
is to be applied. That is, one may employ a
decision-oriented technique to screen several
management practices based on a cost/benefit
analysis or an environmental impact analysis,
after which physical models can comprehensively
analyze the selected procedures.
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Figure 2 illustrates how to evaluate and select
a technique. In this approach, one first identifies
available environmental and managerial models
and characterizes them according to the flow-
chart in Figure 1.
The next question lies in whether or not the
chosen technique has been verified; unverified
models should be treated with extreme caution, if
at all, because of potential Inaccuracies and un-
acceptability of results.
Verified models are evaluated by comparing
the information desired with the costs of using the
model. The decisionmaker should carefully study
the value of the information to be gained versus
costs to determine whether a particular model
can achieve the expected goals within resources
available.
NONPOINT SOURCE POLLUTION ASSESSMENT TECHNIQUES
(AGRICULTURE, SILVICULTURE, URBAN RUNOFF, CONSTRUCTION)
STATISTICAL
DETERMINISTIC
PHYSICAL MODELS
DECISION-ORIENTED
TECHNIQUES
ATTRIBUTES*:
Predict mass transport and loading
Calculate average annual or time varying
pollutant loads
Estimate pollutant concentrations in various
environmental compartments
May simulate chemical/physical/biological
processes
May predict water quality changes in receiving
bodies
ATTRIBUTES:
Include BMPs
Link capital, operation and management cost
of BMPs to water quality benefits
Permit risk/benefit analysis of different BMPs
on beneficial receiving water uses
Address impacts on the environments
'These attributes also may be relevant to Decision-Oriented Techniques.
Figure 1.-
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TECHNIQUE CHARACTERIZATION (PHYSICAL VERSUS DECISION)
DEVELOPMENT OF INFORMATION FOR THE STUDY
Are the Study Objectives,
Information Development
and Scope of the
Technique Compatible?
YES
Has the Technique
Been Validated?
YES
VALUE
Model Parameters of Interest
Model Processes of Interest
Results/Output Options
Documentation and Availability
of User Assistance
Incorporates BMPs, Policy Choices*
NO
NO
1
Risk/Benefit
Analysis
1
Capital Investment
O&M Cost
'For Decision Models
Choose
Another
Technique
Validate After
Studying Values
and Cost
COST
Model Acquisition
Data Gathering/Generation
Model Calibration/Trial Runs
Model Execution for
Different Scenarios
Cost to Validate the Model
Figure 2. Selection of NPS pollution assessment techniques.
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NONPOINT SOURCE POLLUTION MODELS
The models discussed in this section of the Guide
estimate one or more of the following parameters:
(1) runoff, (2) sediment concentrations, and (3)
nonpoint source pollutant loads. Although Tables
1 and 2 list both physical and decision-oriented
models, only the latter are described here be-
cause they focus on implementation. These
models are operational, having been used suc-
cessfully at least once.
Table 3 lists a third category, receiving water
models. Although not developed specifically for
nonpoint source pollution, these models can
simulate effects on the receiving water an ability
some of the physical and decision-oriented
models lack. Decisionmakers can use receiving
water models to select appropriate implementa-
tion models.
The capability of a model to simulate the fol-
lowing parameters also needs to be considered:
Meteorology (rainfall, temperature, snow-
fall), hydrology (subsurface flow, surface
runoff, stream flow), and water body (lakes,
estuaries, oceans).
Spatial (single catchment, multiple catch-
ments) and temporal (annual, event-based,
continuous) simulations.
Land use (agricultural, silvicultural, con-
struction, urban).
Policy choices, BMPs, and associated costs
of implementation.
Environmental effects on beneficial use of
receiving waters.
Simulations on a field or land management
unit basis.
Other considerations include
Extent of input data required (detailed,
moderate, minimal), type of data, and rela-
tive availability.
Need to modify or calibrate model for
specific applications.
User-friendliness of the model.
Availability of user's manuals, reports, and
support to facilitate implementation of the
program.
Hardware and software required.
Costs associated with purchasing neces-
sary items, services, and implementation.
Table 1.-NPS pollution assessment techniques/models: physical models.
TITLE
ACIMO
DR3M
EPA Screening Procedures
ILLUDAS
MUNP
PRMS
PRS
STORM
UTM-TOX
WLFNPS
OBJECTIVE
To simulate runoff and transport from agricultural lands
To simulate urban watershed runoff, sediment yield and water quality
To estimate nonpoint source loads
To estimate urban runoff using an event-based analysis
To estimate the accumulation of pollutants on urban streets
To evaluate the effects of precipitation, climate and land use or
general basin hydrology
To simulate runoff and other hydrologic quantities
To estimate the runoff, sediment and pollutant delivery of
urban watersheds
To estimate the concentrations of pollutants and theirfate and transport
in the environment
To estimate runoff, sediment and pollutant concentrations in runoff in large
agricultural watersheds
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Table 2.-NPS pollution assessment techniques/models: decision models.
TITLE
AGNPS
ARM
ANSWERS
CREAMS/CREAMS 2
COWFISH
ESRFPP(Feedlot model)
GAWS
GLEAMS
NPS
NURP
SWAM
SWMM: Level I
SWMM
WRENS
OBJECTIVE
To simulate sediment, nutrient and pollutant transport in an
agricultural watershed
To simulate runoff and other contributions in streams
To predict hydrologic and erosion response of agricultural watersheds
To simulate hydrologic quantities, erosion and chemical transport
To assess the effect of current and past livestock grazing on associated
aquatic resources
To evaluate and rate the pollution potential of feedlot operations
To assess the effect of sediment yields on stream habitat and fish
populations for planning purposes
To simulate pesticides and nutrients leaching from agricultural watersheds
To continuously simulate hydrologic processes
To evaluate the effect of urban location, management practices, etc.
on urban runoff and receiving water bodies
To evaluate the effects of different land use and management practices
on a small watershed
To estimate runoff and water quality in an urban watershed
To simulate runoff, sediment and nutrient transport in an urban watershed
To evaluate the alternative management decisions used in silviculture
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Table 3.-Receiving water models.
TITLE
CHNTRN
CTAP
DEM
EXAMS
FETRA
LAKECO
MEXAMS
MichRIV
Ms. CLEANER
QUAL-II
RECEIV-IT
SERATRA
SLSA
TODAM
TOXIC
TOXIWASP
WASP/AESOP
WASTOX
OBJECTIVE
To simulate time varying distributions of sediments and chemicals
in receiving waters
To account for dissolved and steady-state concentrations of pollutants
in the water column and bed sediment
To simulate the unsteady tidal flow and dispersion characteristics
of an estuary
Rapid screening and evaluation of the behavior of synthetic organic
chemicals in freshwater ecosystems
To simulate the transport of sediments and contaminants in rivers
and estuaries
To evaluate the consequences of remedial measures for lakes
To estimate the quantities of metals likely to be in solution
To simulate the advective transport of dissolved and adsorbed pollutants
T&evaluate nonlinear, nutrient-algae cycles, multi species
and phytoplankton
To simulate the dispersion and flow characteristics of stream systems
and rivers
To evaluate receiving water by representing physical properties
To predict distributions of sediments and toxic contaminants in rivers
To analyze chemicals in simplified lake and stream settings
To simulate sediment transport, dissolved contaminant transport,
and sorbed contaminant transport
To simulate the behavior of pesticides in a reservoir and bioconcentration
of pesticides in aquatic life
To simulate the transport and transformation of organic toxic chemicals
in the water column and the sediment of stratified lakes, reservoirs, rivers,
estuaries and coastal waters
To allow the specification of time-variable exchange coefficients,
advective flows, wasteloads, and water quality boundary conditions
To simulate the transport and transformation of organic chemicals in the
water column and the sediment of streams and estuaries
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AGRICULTURAL NONPOINT SOURCE POLLUTION MODEL
AGNPS
AGNPS is a. single event-based model that
predicts runoff volume and peak rate, eroded and
delivered sediment, nutrient (nitrogen and phos-
phorus) concentration, and chemical oxygen
demand in the runoff, and the sediment for single
storm events. The model simulates individual
cells within a watershed or for the entire water-
shed. The model is being adapted for annual cal-
culations and for pesticides.
For further information, contact Robert A.
Young, Agricultural Research Service, USDA,
North Central Soil Conservation Research Lab,
Morris, Minn. 56267; phone 612/589-3411.
AERIAL NONPOINT SOURCE WATERSHED ENVIRONMENT
RESPONSE SIMULATION
ANSWERS
ANSWERS simulates single events to estimate
hydrologic and erosion response of agricultural
watersheds. The model simulates interception, in-
filtration, surface storage, surface and subsurface
flow, and sediment detachment, transport, and
deposition. By subdividing the area to be studied
into a finite number of square grids, the model is
capable of considering spatial variation of
hydrologic and sediment processes.
Documentation and a user's manual are avail-
able free from U.S. EPA Region V. For further in-
formation, contact Professor Beasley,
Department of Agricultural Engineering, Purdue
University, West Lafayette, Ind. 47907; phone
317/494-1198.
AGRICULTURAL RUNOFF MANAGEMENT MODEL
ARM
This model simulates the hydrologic, sediment
production, pesticide, and nutrient processes on
the land surface and in the soil profile that deter-
mine the quantity and quality of runoff in small
agricultural watersheds (less than 5 km2 (1.9
m!2)). To do this, detailed input data as well as
calibration and verification data are required; and,
while the model can simulate single events or
continuous conditions, it does not link the cost
associated with different BMPs to pollutant load-
ings.
The model is available through Tom Barnwell
at the Water Quality Modeling Center, Environ-
mental Research Laboratory, U.S. EPA, College
Station Rd., Athens, Ga. 30613; phone 404/546-
3175.
CHEMICALS, RUNOFF, AND EROSION FROM AGRICULTURAL
SYSTEMS
CREAMS
CREAMS and CREAMS 2 are field-scale models
that simulate several processes to evaluate BMPs
such as aerial spraying or soil incorporation of
pesticides, animal waste management, and mini-
mum tillage and terracing. CREAMS 2 is undergo-
ing modification to become more user friendly. It
does not require special calibration for a specific
watershed. Most of the required parameter values
are physically measurable. The model represents
soil processes with reasonable accuracy; but the
maximum size of simulation area is limited to field
plots, and receiving waters are not simulated.
Program manuals, tapes, and floppy disks are
available from the USDA-ARS Southeast Water-
shed Research Laboratory, P.O. Box 946, Tifton,
Ga. 31793; phone 912/386-3462.
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COWS AND FISH
COWFISH
The COWFISH model uses existing environmen-
tal information to derive an initial indication of
how livestock grazing may be affecting trout
populations. Requiring field data, the model con-
siders six variables to determine a stream's
suitability to support trout. The model can be
used throughout the western United States and
can analyze a wide variety of riparian and stream
types; however, it is less accurate for streams
with rocky streambanks that do not follow the
natural development of undercut banks.
The COWFISH model is available from USDA
Forest Services, Federal Bldg., P.O. Box 7669,
Missoula, Mont. 59807; phone 406/329-3101.
EVALUATION SYSTEM TO RATE FEEDLOT POLLUTION
POTENTIAL
ESRFPP
Developed to evaluate and rate the pollution
potential of feedlot operations, the model con-
sists of two parts: (1) a simple screening proce-
dure that evaluates the potential pollution hazard
associated with a feedlot, and (2) a more detailed
analysis that can identify feedlots that are not
potential pollution hazards. The model uses
simple techniques to evaluate the effects of dif-
ferent land management practices; but it is limited
in scope in that its calculations may not be valid
for tributary areas larger than 100 acres, it does
not deal with receiving water bodies, its defined
discharge point may be difficult to apply in the
field, and the potential threats to ground water are
treated lightly.
Documentation and assistance are available
from Robert A. Young, North Central Soil Conser-
vation Research Lab, Agricultural Research Ser-
vice, USDA, Morris, Minn. 56267; phone
612/589-3411.
GROUNDWATER LEACHING EFFECTS ON AGRICULTURAL
MANAGEMENT SYSTEMS
GLEAMS
An extension of USDA'S CREAMS models,
GLEAMS simulates leaching of pesticides and
nutrients from agricultural watersheds. The leach-
ing behavior of pesticides in root zones has been
tested and validated. The model is in develop-
ment/testing stage. For more information contact
Walter G. Knisel, Jr., USDA-ARS, Southeast
Watershed Research Laboratory, P.O. Box 946,
Tifton, Ga. 31793; phone 912/386-3462.
GUIDE FOR PREDICTING SALMONID RESPONSE TO SEDIMENT
YIELDS IN IDAHO BATHOLITH WATERSHEDS
GAWS
This guide is not a computer program. Rather, it
provides a standard method for predicting the ef-
fect of sediment on stream habitat and fish
populations. The model helps land managers
quantify existing and potential impacts and
evaluate trade-offs to fish resources from forest
management. The guide may be obtained from
the U.S. Forest Service's Northern Region and In-
termountain Region, Federal Bldg., P.O. Box
7669, Missoula, Mont. 59807; phone 406/329-
3101.
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HYDROLOGICAL SIMULATION PROGRAM FORTRAN
HSPF
The HSPF is a series of fully integrated computer
codes that simulate watershed hydrology and the
behavior of conventional and organic pollutants
in surface runoff and receiving waters. The sys-
tematic modular framework of the HSPF allows a
variety of modes; the model integrates nonpoint
source loading and receiving water quality
simulation into a single package. It can analyze
relative contributions arid effects of both point
and nonpoint sources. Calibration is necessary
for site-specific applications. Use of the model re-
quires some expertise on the part of the user; two
to three months may be required to learn its
operational details. Also, depending on the extent
of model use, computer costs for operation and
data storage can be a significant fraction (10-15
percent) of total application costs.
HSPF is in the public domain and can be ob-
tained from the Center for Water Quality Model-
ing, Environmental Research Laboratory, U.S.
EPA, College Station Rd., Athens, Ga. 30613;
phone 404/546-3175.
NONPOINT SOURCE LOADING MODEL
NPS
The NPS model simulates sediment and nutrient
transport processes and can simulate nonpoint
pollution from a maximum of five different land
use practices in a single application. It requires
extensive input data, including those related to
model operation, parameter evaluation, and
calibration. Among its output, NPS includes the
option of interfacing with other models.
The model is available through EPA's Water
Quality Modeling Center, Environmental
Research Laboratory, College Station Rd.,
Athens, Ga. 30613; phone 404/546-3175.
STORMWATER MANAGEMENT MODEL
U.S. EPA's Stormwater Management Model pack-
age has several versions whose use depends on
the level of effort available and the amount of in-
formation required to estimate runoff and water
quality in an urban watershed. These versions in-
SWMM
SWMM is a comprehensive, mathematical model
that can represent urban stormwater runoff and
combined sewer overflow phenomena. This
model contains its own receiving water model,
RECEIV. It can be linked to several other
SWMM-LEVEL I
This relatively simple model is designed as a
screening tool to provide a rough estimate of
quantity and quality during a precipitation event
that lasts a few hours in an urban watershed. The
SWMM-SIMPLIFIED
This model simulates runoff and nutrient transport
in an urban watershed. Five tasks are performed
including data preparation, rainfall characteriza-
tion, storage-treatment balance, overflow-quality
elude: SWMM-Level I, Simplified SWMM, and
SWMM. Technical manuals and information on
these models are available from EPA's Nonpoint
Source Branch, 401 M St., S.W., Washington,
D.C. 20460.
simplified receiving water models. SWMM is
capable of a wide range of applications, but its
statistical summaries are limited and its data
management facilities are not advanced. The
model is well documented.
calculations can be performed with a hand cal-
culator. A graphic procedure permits the analyst
to examine a wide variety of controls operating
either parallel or in series with one another.
assessment, and receiving water response. In-
complete documentation and inadequate user
support are problems with using the model.
11
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SMALL WATERSHED MODEL
SWAM
SWAM is an integrated and complex watershed
model that estimates change in hydrologic, sedi-
ment and chemical characteristics of a small
agricultural watershed in response to various land
use and management practices. The model uses
a dynamic version of CREAMS 2 to estimate over-
land flow and pollutant transport. However, the
model is still being tested and has not been
released yet. It is not practical for long-term (20
years or more) simulations. For more information
and to obtain SWAM when it becomes available,
contact Dr. Donald DeCoursey, USDA-ARS, P.O.
Box E, Fort Collins, Colo. 80522; phone 303/221-
0578.
URBAN RUNOFF PROGRAM
NURP
NURP is not a computer model, rather, a statisti-
cal-based technique that addresses the effects of
urban locations and management practices
among other factors on urban runoff and receiv-
ing waters. The methodologies and information
included in NURP facilitate decisionmaking by
using qualitative statements, quantitative es-
timates, and graphic illustrations.
The reports resulting from this program are
available from the National Technical Information
Service, U.S. Department of Commerce, 5285
Port Royal Rd., Springfield, Va. 22161; phone
703/487-4650. For additional information or to ob-
tain a floppy disk containing the program, write to
the EPA Headquarters Nonpoint Sources Branch,
WH-585, 401 M St., S.W., Washington, D.C.
20460.
WATER RESOURCES EVALUATION OF NONPOINT
SILVICULTURAL SOURCES
WRENS
WRENS is a procedural handbook for evaluating
the effects of forest-related activities on water
quality and making management decisions. Al-
though no computer is required to use the proce-
dures, they can be used to estimate some
physical and chemical characteristics. The hand-
book is available from the National Technical In-
formation Service, U.S. Department of Com-
merce, 5825 Port Royal Rd., Springfield, Va.
22161; phone 703/487-4650. Specify No. EPA
600/8-80-012. Cost: $58.95.
12
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Best Management Practices
The specific methods developed to minimize both
the land disturbances and their resulting runoff
which comprise the nonpoint sources polluting
our waters are designated "best management
practices" (BMPs). BMPs are those methods,
measures, or practices designed to prevent or
reduce pollution. They include, but are not
limited to, structural and nonstructural controls
and operation and maintenance procedures.
They often are used in varying combinations to
prevent or control pollution from a given nonpoint
source.
In an attempt to describe the most commonly
used BMPs, the Guide classifies them into broad
categories defined by land use:
agriculture
construction/urban runoff
silviculture
mining
Another classification in the Guide, multi-
category, includes BMPs that are used in all the
above categories.
9 * M
13
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Agriculture: Agricultural BMPs have become
particularly well known because agriculture is
regarded as the primary contributor of phos-
phorus and nitrogen to water. More information
on agricultural BMPs is available from the Nation-
al Water Quality Evaluation Project, North
Carolina State University, 615 Oberlin Rd.,
Raleigh 27605; (919) 737-3723. NWQEP is a
USDA-EPA cooperative venture to control
agricultural nonpoint source pollution at the
watershed level.
Mining: Each phase of mining from the extrac-
tion of minerals to the transport, exploration,
processing, storage, and waste disposal has its
own potential for polluting water, either during
operation or following shutdown. EPA has
developed a list of 17 general control principles to
be considered when choosing BMPs for mining:
1. Choose least hazardous methods.
2. Manage water.
3. Control erosion and trap sediment.
4. Segregate water from toxics.
5. Collect and treat runoff when other ap-
proaches fail.
6. Quickly stabilize disturbed area.
Table 4. Best management practice activity matrix.
7. Properly store minerals and dispose of
mineral wastes.
8. Correct pollution-causing hydrologic distur-
bances.
9. Prevent and control pollution from roads.
10. Avoid disturbing streambeds, streambanks,
and natural drainageways.
11. Use stringent controls in high-risk areas.
12. Apply sound engineering.
13. Properly locate and seal shafts and
boreholes.
14. Control fugitive dust.
15. Maintain control measures.
16. Use temporary stabilization and control
when needed.
17. Prevent and
closedown.
control pollution after
Table 4 provides a matrix relating the individual
BMPs in all categories to one another, and to the
total management plan. By combining Table 4
with the text, which includes cost information for
each BMP, the decisionmaker can weigh the al-
ternative solutions to specific nonpoint source
pollution problems.
BMP
AGRICULTURE
Conservation tillage
Contouring
Contour strip cropping
Cover crops
Integrated pest management
Range and pasture management
Sod-based rotations
Terraces
Waste management practices
CONSTRUCTION & URBAN RUNOFF
Structural control practices
Nonvegetative soil stablization
Porous pavements
Runoff detention/retention
Street cleaning
Surface roughening
SILVICULTURE
Limiting disturbed areas
Log removal techniques
Ground cover
Removal of debris
Proper handling of haul roads
MINING
Water diversion
Underdrains
Block-cut or haul-back
MULTICATEGORY
Buffer Strips
Grassed waterway
Devices to encourage infiltration
Interception/diversion
Material ground cover
Sediment traps
Vegetative stabilization/mulching
14
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Agriculture
CONSERVATION TILLAGE
Conservation tillage refers to any planting system
that reduces soil disturbance and water loss by
retaining crop residues on the land and leaving
the surface rough, porous, cloddy, or ridged.
Conservation tillage (also called minimum tillage,
reduced tillage, stubble mulching) includes no-till,
ridge-till, strip-till, mulch-till, and reduced-tilt. Con-
servation tillage reduces runoff and directly
benefits farmers, but may require special equip-
ment and additional costs.
The preferred conservation tillage method
depends on the soil. Reduced tillage is more
widely adaptable than no-till planting but is some-
what less effective in controlling water pollution.
Reduced tillage is considered more suitable to
cold and wet soils than no-till, with soil drainage
largely determining its economic success. No-till
is most applicable on highly erodible, well-
drained, coarse to medium-textured soils planted
in dormant grass or small grain crops. Farm use
of conservation tillage is increasing rapidly; the
Conservation Technology Information Center in
1986 estimated a 2.8 million-acre increase in con-
servation tillage practices from 1984 to 1985.
Conservation tillage practices often decrease
overall capital expense and increase net return:
thus, their rising popularity. Various studies have
found decreases in diesel fuel consumption over
consumption for conventional tillage; decreased
equipment and labor costs seem to offset any in-
crease in material costs.
All conservation tillage practices reduce
erosion potential below that of conventional til-
lage, in some estimates by 30 percent, with runoff
declining by about 61 percent. In particular, con-
servation tillage effectively controls sediment loss
and phosphorus and pesticide transport; the rate
of effectiveness depends on the soil type, climate,
slope, and so forth, and typically ranges from 40
to 90 percent for conservation tillage to 50 to 95
percent for no-tillage. Studies have recorded no
runoff from conservation tillage compared with
runoff from only 2.0 cm rainfall with conventional
tillage. Conservation tillage could contribute more
groundwater contamination from pesticide use,
but research has shown that conservation tillage
does not necessarily require more pesticide
usage.
15
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CONTOURING
Plowing follows the contours of the field (perpen-
dicular to the slope of the land). Crops are then
planted along these tilled contours.
Contouring is limited by soil, climate, and
topography (suited to 2 to 8 percent slope), and
may not be usable with large farming equipment
under some topographic conditions.
Costs are slight because contouring does not
require specialized farm equipment, nor does it
affect fertilizer or pesticide rates. A proper plow-
ing design must be established.
Contouring can reduce average soil loss (and,
therefore, runoff) more on moderate slopes than
on steep grades. Contouring loses its effective-
ness if the rows break down, so for long slopes
terraces may be necessary; and the practice also
loses its effectiveness during extreme storms
when rainfall exceeds the surface storage
capacity. Contouring should be practiced along
with terracing or strip cropping on moderate
slopes for maximum effectiveness in reducing
erosion.
1 STRIPCROPPING
Stripcropping alternates plowed strips of row
crops and close-grown crops such as pasture,
hay, or grasses to reduce erosion on tilled soils.
The method of laying out the strips nearly perpen-
dicular to the direction of the slope is called con-
tour Stripcropping.
The primary advantage of Stripcropping is that
it permits row crops on slopes; it is particularly
applicable for 8 to 15 percent slopes. Contour
Stripcropping is nearly twice as effective in con-
trolling erosion as seeding grain in the fall to
replace pasture.
Contour Stripcropping does not require the
purchase of specialized farming equipment, nor
does it affect fertilizer and pesticide application
rates. However, a farmer must have a use for the
various crops being grown for the method to be
truly cost effective.
The practice reduces the velocity of the water
as it leaves the tilled areas, because the buffer
strip absorbs runoff and retains soil particles, thus
minimizing nutrient and pesticide entry into sur-
face water bodies.
16
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COVER CROPS
Cover crops are grown when the ground is nor-
mally fallow, to protect the soil from leaching and
erosion. Crops that leave large quantities of
residue after harvest offer more soil protection
than crops with small quantities of residue.
The cover crop technique is applicable to all
cropland. Winter cover crops provide a good
base for the next spring planting in some
climates. Many cover crops are left on the soil as
protective mulch or are plowed under to improve
the soil.
Cover cropping requires moderate expendi-
ture. No special equipment is needed, but plant-
ing will require seed; man hours; and machine
use, maintenance, and fuel.
Cover crops reduce water and soil loss, mini-
mizing less of nutrients and pesticides (if
present), and may even provide nitrogen. In
general, cover crops provide better protection
from the erosive effects of precipitation than does
continuous intertilling.
W''f. .4-
FERTILIZER MANAGEMENT
Fertilizers, while they add to the productivity of
the land, increase the potential amount of pol-
lutants leachable by rainfall. The judicious use of
fertilizers is advisable to both increase net profits
and minimize groundwater pollution.
The quantity of fertilizer used depends mostly
on crop needs (and absorption rates) and exist-
ing soil fertility. Another important consideration
in choosing a fertilizer is each one's propensity to
be carried away by water and sediment. Fer-
tilizers are capable of increasing root density,
which will make a soil more permeable and fur-
ther facilitate the plants' nutrient uptake.
According to EPA's Great Lakes National
Program Office Special Workshop, good fertilizer
management can include
optimizing crop planting time
optimizing fertilizer formulation
optimizing time of day for application
optimizing date of application
using lower application rates
optimizing placement of fertilizer
Improved fertilizer management is cost effec-
tive, capable of reducing the capital invested in
fertilizer as well as the man hours, equipment,
and fuel involved in applying it.
17
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INTEGRATED PEST MANAGEMENT
Integrated pest management combines tradition-
al pest control methods (crop rotation and pes-
ticides) with sophisticated measures (life cycle
analysis and monitoring). Pesticides are applied
at a minimal rate, the method and timing carefully
selected according to the targeted pest. The
newer pesticides are less persistent in the en-
vironment and, therefore, have fewer long-term
impacts; but they are also more likely to be water
soluble. These waterborne toxic chemicals may
cause serious short-term surface water problems
and eventually degrade groundwater resources.
According to EPA's Great Lakes National
Program Office Special Workshop, farmers can
help control pesticide losses by
combining mechanical cultivation with dis-
ease-resistant crop varieties,
trying other pesticides,
optimizing pesticide placement with respect
to loss,
rotating crops,
optimizing crop planting date,
optimizing pesticide formulation,
reducing excessive treatment, and
optimizing time of day for pesticide applica-
tion.
Other practices with limited applicability are:
using lower pesticide application rates,
optimizing date of pesticide applicability,
using integrated control programs,
using biological control methods,
managing aerial applications, and
planting between rows in minimum tillage.
An effective integrated pesticide management
program can reduce pollutant loadings by 20 to
40 percent, depending on the pesticide, the crop,
and the practices used.
Pesticide management is highly cost effective,
improving profits and decreasing input costs.
As in fertilizer management, conservation til-
lage practiced without the appropriate pesticide
management is not considered an acceptable
BMP.
RANGE AND PASTURE MANAGEMENT
Lands used for grazing vary in climate, topog-
raphy, soils, and vegetative type and condition, a
diversity that creates the potential for varying
degrees of erosion. Overgrazing changes the soil
structure (because the soil compacts, becoming
less permeable) and the density, vigor, and
species composition of vegetation, thus exposing
the soil to the erosive forces of wind and water.
Grazing management practices should restrict
livestock use to the carrying capacity of the land,
thus minimizing erosion.
Recommended practices for rangeland and
pasture management include rotation grazing (al-
lowing fields to recover vegetation)seasonal graz-
ing (allowing a specific vegetation's reseed-
ing)water supply dispersal (distributing the
livestock better by avoiding overuse of water
supply areas) creating ponds in pastures (conser-
ves water) salt, mineral, and feed supplement site
relocation and/or dispersal restriction of access
to highly erodible areas.
Most of these management practices involve
applying common sense to land use; a farmer or
rancher must know such factors as stocking rates
and vegetation types and conditions.
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SOD-BASED CROP ROTATION
Sod-based crop rotation involves planting a
planned sequence of crops in regular succession
on the same land, rather than cultivating one crop
continuously. Sod-forming grasses and legumes
are used, with hay a part of the cycle. Sod-based
rotations may be used on all cropland, particular-
ly those farm operations with livestock that can
eat the hay grown as part of the cycle.
Soil and water loss from a good quality grass
and legume meadow is negligible, snd plowing
the sod improves infiltration and soil structure in
general and reduces erosion. Sod-based rota-
tions help control some diseases and pests and
also give the farmer more fertilizer placement op-
tions.
Sod-based rotations can be costly since the
farm's income is reduced by substituting hay for
feed; but special equipment is not necessary.
Labor costs may be increased.
TERRACING
A terrace is a ridge or embankment constructed
across a slope to control erosion. Terracing is
generally applied to fields where contouring,
stripcropping, and tillage operations are not ade-
quate. By shortening long sloping areas, terrac-
ing slows runoff and prevents the formation of
gullies, reduces soil loss, and conserves soil
moisture. Terraces have proven to be more effec-
tive in reducing erosion than in reducing total
runoff.
Terraces often require new management prac-
tices to maintain their desired effects. Many com-
puter programs are available to select the best
terracing design. Initially, they involve substantial
cost and may require periodic maintenance ex-
penditures; but, over time, income usually in-
creases.
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WASTE MANAGEMENT
Effective containment of animal waste can reduce
phosphorus runoff by as much as 50 to 70 per-
cent, thereby minimizing water quality impacts
and conserving fertilizer for food production
during the summer months. Animal waste
management practices must be designed to meet
site conditions, type of animal wastes, and farm
management practices. In addition to storage
facilities for animal waste, runoff diversion struc-
tures are often needed in barnyard areas to
reduce waste transport.
Given the variability of site topography and
layout of barns, each farm requires an individually
designed system. Waste management practices
are generally costly, requiring significant personal
investment from farmers in pollution control (see
Table 5). Because of the costs involved, the waste
management system must appeal to a farmer as
being beneficial to overall management and
productivity. Sometimes gutters and diversions
can accomplish much pollution control at low
cost for barnyards.
Table 5. Typical manure storage facilities and costs.
MANURE SYSTEM
TYPE FARM COMPONENTS
TOTAL
COST
Dairy
90 milkers
20 youngstock
freestall
Dairy
28 milkers
20 youngstock
stanchion
Dairy Replacement
20 animals
stanchion
Poultry Litter
Stacking Site
20,000 Broilers
50'x80'x 10'
Concrete storage
with push off ramps
and roof
Equipment
40' x 40'
Asphalt Pad with
8' Concrete headwall
and earth sides
Equipment
37' x 37' x 4'
Concrete storage
Asphalted barnyard
Runoff controls:
holding basin
450' diversion
40' x 40 '
Concrete Pad
with earth berms
39,578
3,080
14,168
4,774
$61,600
1,848
9,856
2,772
6,776
$21,252
7,469
3,234
693
2,310
$13,706
4,466
4,774
$ 9,240
Costs have been updated to 1985 dollars Source: U.S EPA. 1980c
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Urban and Construction
STRUCTURAL CONTROLS
Structural controls are used when vegetation
alone will not protect a site from erosion or runoff
problems, or when flow concentrates in a specific
area as it does in drainage courses. Structures
should be built to provide maximum site protec-
tion. On urban construction sites and major high-
way projects where storm drains are used,
preventing sediment damage to the drainage sys-
tem becomes especially important; and it is also
important to remove sediment from settling
ponds and sediment basins.
Many complex factors influence effectiveness,
including soil erodibility, climate, types of control
practices being used, sediment characteristics,
and flow characteristics. Bank protection struc-
tures and grade stabilization structures help con-
trol channel erosion in drainageways. However,
standard design and construction criteria are not
available for many practices for varying slope
conditions. Sediment basins are generally
designed to have a minimum of 70 percent effec-
tiveness.
Costs vary widely according to the complexity
of the structure and its maintenance require-
ments. Some control structures require daily in-
spection; and, actually, the best time to inspect
most structural controls is during a major storm
to correct any problems that might lead to sedi-
ment damage or higher operating costs.
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NONVEGETATIVE SOIL STABILIZATION
Npnvegetative stabilization can be used
anywhere erosive gradients exist, particularly at
gully headlands. Temporary stabilization, using
covers and binders to shield the surface from
rainfall and runoff or to bind the soil particles into
a resistant mass, protects the land during distur-
bances (such as construction activities) or while
permanent vegetation is developing. Where
plants will not take care of the problem (such as
on excessively steep slopes), permanent
stabilization is necessary.
On-site nonvegetative stabilization techniques
have been found to reduce erosion by 75 to 90
percent. Costs vary widely because of the many
available techniques.
POROUS PAVEMENTS
The primary benefit of porous pavements is that
they significantly reduce runoff from otherwise
impervious areas. Most porous pavements are
made from asphalt in which the fine filling par-
ticles are missing; this is installed on top of a
gravel base. This type of pavement can be in-
stalled over existing impervious pavements, an
advantage in cities with combined sewers (reduc-
ing overflow) or in areas with inadequate storm
drainage.
Pollution loading by surface runoff from a
porous pavement should be zero if all water in-
filtrates. This may not happen, especially if the
pavement is installed on an impervious surface.
However, even when the ground is impervious,
the porous pavement and gravel base are benefi-
cial: together the pavement and base act as a fil-
ter, with the base serving as a storage area for
water needing treatment.
Although porous pavements for parking lots,
roads, and other urban surfaces may cost more
than conventional surfaces, enough savings
should be realized in sewer and drainage costs,
as well as in treatment costs, to offset the installa-
tion. Porous pavements rely on proper main-
tenance to achieve maximum benefit.
RUNOFF DETENTION/RETENTION
Runoff storage facilities can prevent or reduce
storm water runoff. Detention facilities treat pol-
lutants, by holding the water and treatment is
through settling. Retention facilities control peak
flows from storm events, but provide little treat-
ment.
Storage and gradual release of storm water
lessens the downstream impacts of flooding,
stream bank erosion, resuspension of bottom
sediment, and disruption of aquatic habitats. The
Nationwide Urban Runoff Program (NURP) has
found wet basins to provide better water quality
control than dry basins. NURP monitoring also
revealed a great variety in performance among
basins. The variability in effectiveness
demonstrates the critical importance of designing
a basin carefully in relation to the target urban
area. Costs will vary accordingly to type and size
of the facility designed.
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1 STREET CLEANING
Street cleaning includes sweeping streets and
parking lots with mechanical vehicles or flushing
from tanker trucks. Sweeping (common in the
United States) handles coarser dust and litter par-
ticles, and flushing (practiced in Europe) carries
away the finer fractions.
Studies indicate that street cleaning is not ef-
fective in controlling heavy metals, and moderate-
ly effective in controlling oil and grease, floating
matter, and salts. Studies also showed that street
cleaning is ineffective in decreasing pollution;
however, one reported a significant improvement
in water quality in areas with regular sweeping
practices.
Machinery costs for sweepers range from
about $62,000 to $72,000; labor averages
$9/hour.
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Silviculture
LIMITING DISTURBED AREAS
In areas of intensive logging activities, limiting the
space in which work is done can help exercise
maximum control over potential nonpoint source
pollution. Operating in a clearly defined area,
while controlling potential pollution sources, will
generally not increase costs if it is fully integrated
into operations to make the most effective use of
equipment, labor, and management. Operating
costs may decline because management is con-
centrated on a smaller area of operation.
:
- ^
25
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LOG REMOVAL TECHNIQUES
Log transport (yarding) methods, moving
logs from the felling location to a landing or
transfer point, can vary drastically in their
effect on the environment. The methods
and the access roads associated with them
are primary causes of erosion and
sedimentation.
Tractor skidding is the most common
transport method in the Northeast and
South and on some of the lower sloped
lands in the Intermountain, Northwestern,
and California operations. It is the worst
technique in terms of erosion, exposing
more soil than any of the other methods.
Better than tractoring is high lead transport,
in which a metal tower about 23 meters (75
feet) high and mounted on a mobile frame
is attached by guy lines to a winch and cable
to drag the logs to a yarding area. By this
method, deep profile niches may be cut into
repeatedly used paths.
Skyline, balloon, and helicoptertransport
systems all get the logs off the ground.
Skyline cable confines soil disturbance to
yarding and loading areas. Helicoptering is
especially versatile for moving logs from fell-
ing sites to loading areas.
Ballooning and helicoptering are the two
most effective and the most expensive of the
techniques. The high cost of heavy helicop-
ters restricts their use to inaccessible
terrain.
26
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GROUND COVER
Maintaining ground cover in a disturbed area will
help prevent erosion while the vegetation even-
tually reestablishes. Grass, shrubs, small trees,
and sod provide good ground cover for forests
disturbed by logging. By retaining moisture and
the physical condition of the soil, the vegetation
planted after tree felling helps return the site to
prelogging conditions. Because of the difficulty in
establishing grass in some soil types or land
topographies, jute mats or excelsior pads may be
necessary to keep the seeds in place. The costs
of this management technique include plant
material, fertilizer, and labor expenditures.
1 REMOVAL OF DEBRIS
Maintaining stream channels by preventing the
buildup of debris from logging activities will sig-
nificantly reduce the impact on the water course.
Debris that deflects or constricts waterflow ac-
celerates bank and channel erosion. Streams
near logging operations must be properly and
regularly checked for buildup of such debris, but
ultimately this management practice should cost
nothing. The only requirement is enough super-
vision over logging operations to ensure the
proper removal and disposal of debris. Cleanup
costs have varied, averaging $500 per station
when about 5 tons of material were removed.
27
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PROPER ROADS AND TRAILS
Appropriate location and design of haul roads will
help prevent erosion in disturbed areas. Road-
ways should be built away from water courses
and according to recommended guidelines for
gradient, drainage, soil stabilization, and filter
strips in the area. Where possible, roads should
be rooted across slopes. Road coverings such as
gravel or grass reduce sediment loss; gravel
cover will last several years, whereas grass must
be replenished routinely and loses effectiveness
on highly traveled roads. Use of haul roads
should be restricted during wet weather, and the
roads should be closed when not in use.
Although the prelogging construction of an
adequate access route may cost the company a
great deal, it is important that the road causes the
least environmental impact. Grasses are cheaper
than the various rock roadbeds but require main-
tenance and periodic replanting.
-.,#
28
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Mining
WATER DIVERSION
Water diversion involves collecting the water
before it enters the mine, then conveying it
around the mine site. A water diversion system
should be properly designed to accommodate
expected volumes and water velocities. Ditches,
flumes, pipes, trench drains, and dikes are com-
monly used for water diversion. Riprap and
dumped rock are sometimes used in the con-
veyance system. Surface water diversion is an ef-
fective technique for preventing water pollution; it
can be applied to almost any surface mine or
waste pile. Costs vary according to the site, type
of mine and operation, and design and materials
used. Water diversion reduces treatment costs by
reducing the volume of water that needs to be
treated.
UNDERDRAINS
Underdrains of tile, rock, or perforated pipe can
be placed below pollution-forming materials to
quickly discharge infiltrating water. These devices
shorten the flow path and residence time of water
in the waste materials. They should be used only
in piles where the water table fluctuates and flow
is in direct response to rainfall. Underdrains
operate most efficiently and are relatively cheap
to install if built before the pile is created. Filter
fabric is also installed to preclude the clogging of
fines when the underdrain is in use.
BLOCK CUTTING
Block cutting makes it possible to mine on
steeper slopes without the danger of slides and
with minimal disturbance. By depositing the over-
burden in the previous cut, topsoil is saved and
the outcrop barrier is left intact; in short, reclama-
tion is integrated with mining. The block-cut
method is no more expensive and may be less
than conventional dragline pullback mining.
Reclamation costs are lower because the over-
burden is handled only once instead of two or
three times.
29
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Multicategory
BUFFER STRIPS
Buffer zones are strips of grass or other erosion-
resistant vegetation planted between a waterway
and intensively used land. By retarding water
flow, the strips increase infiltration and detention
of paniculate matter. Although applicable to all
stream, lake, and open channel areas, buffer
strips often don't work when used along stream
banks. They also require maintenance. In addi-
tion, this management practice does not address
the source of pollutants and may remove agricul-
tural land from production and other land from
development. Buffer strips require moderate ex-
penditure and should be incorporated as needed
along waterways.
GRASSED WATERWAYS
Grassed waterways are natural or constructed
drainage channels used to conduct surface
runoff. The waterways are usually broad and shal-
low, covered with erosion-resistant grasses.
Agricultural grassed waterways are used for safe
disposal of runoff from fields, diversions, terraces,
and for other conservation measures. This BMP
has application in residential and construction
areas as well. Grassed waterways can prevent 60
to 80 percent of suspended particles from moving
to adjacent surface waters. Agricultural grassed
outlets involve costs to establish and maintain
and may interfere with the use of large equip-
ment. But this technique is probably the most ef-
fective and economical means of conveying
water. Proper design is necessary to ensure max-
imum efficiency from the waterway.
INFILTRATION DEVICES
Infiltration, which is the gradual downward move-
ment of water from the surface into the subsoil,
may totally remove fine soil particles and other
particulates as well as dissolved solids. Increased
infiltration improves recharge into groundwater
aquifers, and the most popular method of in-
creasing infiltration is the use of trenches, or
ponds. Other ways to induce infiltration include
dry wells, wet and dry ponds, evaporation ponds,
and special impoundments.
Infiltration devices can be an acceptable ap-
proach to managing stormwater runoff, but they
must be limited to good quality storm water to
prevent contamination of the ground water. A per-
vious subsoil is necessary to dispose of water at
an adequate rate. Although these systems may
require a great deal of maintenance (because of
clogging), routing the water over grass, vegeta-
tive filters, or sediment traps before it enters the
infiltration device can substantially correct for the
problem.
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INTERCEPTION/DIVERSION PRACTICES
Basically, diversion structures are designed to in-
tercept runoff before it has a chance to come in
contact with an erodible soil surface. Diversion
structures include soil or stone dikes, ditches (or
swales), terraces, and benches. These structures
can be temporary or permanent and should not
cause in-channel erosion. The practice is par-
ticularly applicable on slopes of up to 12 percent
and above feedlots on any slope. The diversion
structure should allow a shallow, random flow.
Pertinent for construction sites, urban and
agricultural lands, and highway areas, the struc-
tures are usually used to protect bottom lands
from hillside runoff, divert water from areal sour-
ces of nonpoint pollution, or protect structures
from runoff. Diversion structures require some en-
gineering design; the costs can vary from inex-
pensive earth channel to a very expensive
concrete waterway. Maintenance is generally re-
quired, and cultivation, or the activity the struc-
ture is built to protect, may suffer slightly from the
interference.
MATERIAL GROUND COVER
Riprap (loose rock, aggregate, mulches, or
fabric), layered over an erodible surface, provides
an excellent erosion control for all nonpoint sour-
ces. The technique has wide application, from
storm drain outlets to roadside ditches, lake
shores, and drop structures. Vinyl or geo-fabrics
should be placed beneath the riprap to protect
from fine particulates and sediment being pulled
down with the water.
Costs vary tremendously depending on the
amount of damage already done at a site, the
material to be used, and the size of the area to be
covered. In areas where the practice has been
undertaken, visual inspection has concluded that
riprap has protected severely eroded shorelines
and is expected to discourage further erosion.
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SEDIMENT TRAPS
Sediment traps are small, temporary structures
used at various points within or near disturbed
areas to detain runoff for a short period and trap
coarser sediment particles. Various types of traps
include sandbags, straw bales, stone or prefabri-
cated check dams, log and pole structures, ex-
cavated ditches, and small pits. A stone trap
placed across stream channels can temporarily
detain flow and trap sediment; this type is con-
structed of randomly placed stone, sized accord-
ing to predicted flow rates. Sediment traps should
be cleaned when the sediment reaches 50 per-
cent of the trap's depth.
Sediment traps are usually inexpensive to build
and maintain, although they do require periodic
inspection and cleaning. They can be incor-
porated into any construction project.
VEGETATIVE STABILIZATION
Vegetation is a very desirable material for control-
ling erosion because it shields the soil from the
direct impact of raindrops, retards surface flow of
water (thereby increasing infiltration), maintains a
pervious, absorptive soil surface, and removes
excess water from the soil by transpiration.
Stabilization can be achieved with either tem-
porary or permanent plant cover. Installation of
the plants requires preparing the soil and good
planting techniques. Grasses and legumes are
considered superior to trees, shrubs, and ground
covers initially because of their fibrous root sys-
tems. Vegetative cover both reduces pollution to
lakes and streams and improves the aesthetics of
the environment, including providing wildlife
habitat.
Costs vary depending on the size and purpose
of the area to be planted. Grass next to a highway
costs less than an urban landscaping project.
Also, the condition of the soil before planting is an
important consideration. Once the vegetation be-
comes established, regular maintenance is
necessary to achieve long-term cover and ade-
quate erosion control. In certain areas, low-main-
tenance plant material is feasible.
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