Manual of Construction Source
Predictive Techniques
and
Preventive Control Technologies
U.S. Environmental Protection Agency
Region VIII Denver, Colorado
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MANUAL OF CONSTRUCTION SOURCt
PREDICTIVE TECHNIQUES
AND
PREVENTIVE CONTROL TECHNOLOGIES
U.S. EPA Region 8 Library
80C-L
999 18th St., Suite 500
Denver. CO 80202-2466
s.
Reg i on
Protection Agency
Environmenta 1 . .
• Denver, Colorado
VIII
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CONTENTS
Figures v
Tables vii
SECTION 1 - INTRODUCTION 1
SECTION 2 - MEASURING AND ESTIMATING THE EXTENT
OF THE PROBLEM 4
Introduction 4
Regional Perspective 5
Erosion and Sedimentation Processes 6
-Erosion 6
-Sedimentation 10
Field Documentation 11
Measurement 13
Remote Sensing Techniques 15
Mathematical Predictive Techniques 17
-Background 17
-Computational Techniques for Soil
Loss From Sheet and Rill Erosion 17
-Musgrave Formula 18
-Modified Musgrave Formula 18
-SCS Modification to Musgrave
Formula 19
-Universal Soil Loss Equation.... 19
-Rainfall factor 21
-Soil erodibility factor.... 23
-Slope length and steepness
factors 23
-Soil cover and management
factor 25
-Erosion control practice
factor 25
-Example computation 28
-Discussion 31
-Gully Erosion 33
-Wind Erosion 35
-Sediment Yield and Delivery 36
References 39
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SECTION 3 - SEDIMENT CONTROL TECHNOLOGY 41
Introduction 41
Control Principles 42
-Site Planning 43
-Construction Planning 44
-Erosion Prevention 45
-Sediment Retention 46
-Maintenance 46
Control Practices 47
-Soil Stabilization Practices 47
-Areas Subject to Sheet Flow.... 48
-Vegetative Stabilization.. 48
-Nonvegetative Stabiliza
tion 50
-Areas Subject to Concentrated
Flow 57
-Vegetative Stabilization.. 57
-Nonvegetative Stabiliza
tion 58
-Runoff Control Practices 60
-Reduction of Runoff Volume and
Velocity 62
-Staging of Operations 62
-Manipulation of Soil
Surfaces 63
-Manipulation of Slope
Length and Gradient 65
-Interception and Diversion 65
-Handling and Disposal of
Concentrated Flow 66
-Detention of Runoff 71
-Pre-Sediment Pond Tech
niques 71
-Sediment Basins 75
Maintenance of Control Practices 82
-Vegetative Maintenance 83
-Structural Maintenance 83
Control Strategy 84
-Site Inventory and Interpretation... 85
-Preparation of Control Plan 85
-Clearing and Grading Schedule.. 86
-Timing and Location of Control
Measures 86
-Traf f i c Control 87
-Stream Erosion 87
-Planting Schedule 87
-Grading Delays 87
-Planning Assistance 88
-Control Strategies for Specific
Developments 88
References 91
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SECTION 4 - INSTITUTIONAL APPROACHES TO
PREVENTION AND CONTROL 92
The Institutional Setting 9 2
Regulatory Devices 96
-Permits 9 7
-Building Codes and Subdivision
Regulations 98
-Site Oriented Devices 99
-Planning and Zoning 100
-Zoning Amendments 100
-Critical Areas 100
-Public Lands 100
Institutional Arrangements 101
Legal Authority 105
-Home Rule Jurisdiction 106
-Delegated Powers 106
-The Police Power 107
-Some General Constraints Upon
Regulatory Authority 107
-The Limited Use of Implied
Powers 107
-The Test of Reasonableness 108
-Due Process 108
-The "Taking Issue" lo8
-The "Equal Protection" Issue 109
-General Procedures for Obtaining
Needed Regulatory Authority 109
Funding 110
-Costs Ill
-Sources of Funding and Cost
Allocation 112
Public Support 114
Implementation Strategy 115
-Planning as Close to Implementation
As You Dare 115
-Periodic Review and Revision 115
-Enforcement 115
References 117
APPENDIX A - LIST OF PUBLISHED SOIL SURVEYS
IN THE STUDY AREA 118
Glossary 120
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FIGURES
Number Page
1 Soil pillars left by raindrop impact 8
2 Rills formed by soil erosion on a slope 8
3 Suspended sediment in runoff 12
4 Deposited sediment 12
5 Vacuum type of automatic water sampler 15
6 Values of the rainfall factor, R 22
7 Soil erodibility nomograph 24
8 Slope effect chart 26
9 Equivalent slope lengths 27
10 Open space along a stream in a residential
area 44
11 Staging of grading and stabilization activities
at a roadway construction site 45
12 Wood fiber mulch and seed being applied with
a hydroseeder 51
13 Straw mulch being anchored with a mulch
crimper 56
14 Jute netting being installed in a drainageway... 59
15 Stone riprap placed at bend in stream 59
16 Grade control/energy dissipation structure
made of gabions 61
17 Grade control structure consisting of grouted
riprap and placed at storm drain outfall 61
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18 Vegetated buffer area below graded highway
slope collecting sediment 62
19 Properly "tracked" slope 64
20 Vegetated fill slope with contour furrows 64
21 Diversion ditch protecting lower lying waterway. 68
22 Bituminous concrete flume 68
23 Flexible downdrain 69
24 Sectional, or half-round, downdrain structure... 69
25 Stone riprap energy dissipation at storm drain
outfall 70
26 Permanent concrete grade control structure
in a lined ditch 70
27 Gravel filter at storm drain inlet detaining
and filtering runoff 73
28 Filter berm placed across a graded roadway
right-of-way ' 73
29 Grassed filter strip between drainageway and
roadway construction 74
30 Temporary straw bale sediment trap along
roadway 74
31 Sediment accumulated in a dry trap at a highway
storm drain inlet 76
32 Dry sediment basin at perimeter of a large
residential development 76
33 Ideal settling velocity for a sphere 78
34 Regulatory building blocks 95
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TABLES
Number Page
1 "P" Values for Various Types of Control
Practices 28
2 Detailed Soil Description 30
3 Description of Gullies and Drainage Area 34
4 Characteristics of Commonly Used Mulches 52
5 Summary of Chemical Binders and Tacks 54
6 Minimum Sediment Pond Area Requirements 80
7 Short Circuiting for Settling Tanks 82
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SECTION I
INTRODUCTION
Large-scale urban development is projected to accompany
large-scale energy development in the Western United States.
Much attention has been given to the reclamation plans
proposed for surface mines in the region. Land disturbing
activities associated with the urbanization process also
have the potential to generate sediment that can damage
property and water quality in downstream areas. Many of
these construction activities will take place outside the
scope of individual mine development and reclamation plans.
Further, urbanization induced by the energy boom is likely
to take place very rapidly.
In order to prevent these adverse effects of urbaniza-
tion, the local planner in the Western States must be
equipped with the technical and institutional means to deal
with the problem. This manual is a part of the EPA Region
VIII Energy Program intended to provide these tools to the
planner. It cannot, however, be used as a simple cookbook.
The manual presents principles and practices that have been
used effectively in other applications. The missing in-
gredients are the planner's own energy, imagination, and
first-hand sensitivity to specific local circumstances.
A study-area, characteristic of energy-impacted regions
in the Western States, was used in the development of this
manual. The study area consisted of the following counties:
• Montana
Sweet Grass
Sti11 water
Carbon
Yellowstone
Big Horn
Treasure
Rosebud
Powder River
Custer
Carter
Fal1 on
• Wyomi ng
Sheridan
Johnson
Campbel1
e Colorado
Moffat
Rio Blanco
Garfield
Mesa
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• Utah - Daggett
- Duchesne
- Unitah
- Carbon
- Emery
- Grand
Most of the material presented in this manual should be
applicable throughout Region VIII.
Section II, entitled "Measuring and Estimating the
Extent of the Problem," describes erosion and sedimentation
processes in the western arid zone. Techniques of measurement
and estimation are eseentially attempts at modelling these
natural processes. A number of such techniques are pre-
sented.
As with any empirical models, actual field data are
requisite to the acievement of a reasonable level of ac-
curacy. In the arid zone of the Western United States, there
is a critical absence of such empirical research. Even the
Universal Soil Loss Equation - the workhorse of sediment
control planning in most of the country - is of limited
utility in the West due to this lack of empirical data.
Nonetheless, the Universal Soil Loss Equation and other
similar techniques are important to the western planner as
accurate framework for the appropirate variables. With an
understanding of the uncertainties involved, planners should
be able to make the best use of these tools by:
(1) relying on the experienced judgement of
professional engineers familiar with the
area, and
(2) relying more heavily on the control tech-
hiques and institutional practices presented
in Sections III and IV of this manual.
Section III is a practical guide to the most commonly
used sediment control practices. The application of all the
major types are fully described and illustrated. The sec-
tion is prefaced with a discussion of sediment control
principles. These should be closely studied by the planner.
The choice of control techniques on any given site is an
integrated design problem. It is only through proper appli-
cation of the basic principles of sediment control that the
planner can make the right choices of control techniques.
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Section IV presents a broad range of institutional
strategies that the planner may apply to make sediment
control a reality. The intensive nature and the rate
of energy boom-town development suggest that the planner,
in order to be most effective, should procure more than
adequate institutional muscle before development has
begun. It must be noted, however, that the initiation
of an institutional program is also a complex design
problem. The planner's success will hinge on his
creativity in making such programs acceptable and his
flexibility in making them work.
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SECTION 2
MEASURING AND ESTIMATING THE EXTENT OF THE PROBLEM
INTRODUCTION
Measuring and estimating the extent of sediment prob-^
lems at construction sites in the study area is not an easy
task and should not be based solely on "cookbook" approaches
if reasonably accurate results are expected. Field and
mathematical techniques will not normally provide defensible
data unless they are utilized by trained and experienced
technicians. Values of parameters used in the Universal
Soil Loss Equation, for example, cannot always be extracted
from tables or from laboratory testing, but must be esti-
mated based on the field data on hand. As in any computa-
tion, poor input equals poor output.
The computational technique itself can also be a source
of error in estimating the extent of construction related
sediment problems. It must be remembered that hydrology is
an inexact science based both on the laws of physics and
statistical information gathered from laboratory and field
studies. In that some techniques such as the Universal Soil
Loss Equation, for example, have been formulated using
fairly localized data, caution should be exercised in their
use until they can be corroborated with actual field measure-
ments. This is particularly true in the study area, where
construction related sediment problems are only now becoming
a major concern, where little experience has been gained in
predicting soil loss and sediment yield, and where field
data has not been gathered with which to evaluate the
effectiveness of predictive techniques and calibrate them to
the conditions on hand. Calibration or customizing of
predictive techniques for the study area cannot be done
solely on paper, but must be done using statistical infor-
mation gathered from laboratory and field studies.
This section of the manual presents in a summary
manner, several procedures that can be used in the study
area for obtaining gross esimates of the extent of the
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sediment problems. Prior to presenting these procedures,
background information on the hydrologic setting within the
study area and erosion and sedimentation processes are dis-
cussed.
REGIONAL PERSPECTIVE
Water found in arid and semiarid areas, such as the
study area, can be grouped into two general categories ac-
cording to its origins. The first category is regional
water that is derived from the precipitation actually oc-
curring within the area and appears as streamflow or ground-
water. The second category is water that originates from
more humid areas and enters arid and semiarid zones as
streamflow or as extensive groundwater reserves which are in
turn recharged from aquifers that extend beyond the arid
and semiarid region.
One of the main features of precipitation in arid
regions is the high variability in the amount received. In
fact, the standard deviation of the mean annual rainfall may
exceed the mean value. Precipitation characteristics reflect
a high variability in space and time of individual storms,
of seasonal rainfall, and of annual and cyclical totals.
In many arid regions, rain frequently falls, particu-
larly in the winter, in groups of several wet days associ-
ated with area-wide weather influences. In summer, pro-
longed rainfall can follow the intrusion of moist air into
the area, but thunderstorm activity is more customary. This
results in rain seldom falling on two or more days in a row.
Despite variations due to differences of structure and
geomorphic history, surface runoff in most semiarid and arid
areas has many common characteristic features. Upland
sectors of relatively organized-incised channels, plain
tracts across which larger channels persist, and terminal
lowlands which have extensive sand cover are included in
these typical features. Drainage activity is erosive in the
uplands and becomes more uniform in grade of deposited
material in the lower zones.
The low density of vegetation in these areas is an
important factor in landform evolution. Natural vegetation
plays a reduced role in the weathering process and is
relatively ineffective in binding detrital mantles or in
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preserving minor channel forms. Lack of dense vegetation
provides incomplete protection against raindrop impact and
scour by runoff. With inefficient storage of rainfall by
natural vegetation and soils, runoff is not regulated.
EROSION AND SEDIMENTATION PROCESSES
Erosion
Erosion may be defined as the group of processes
whereby soil or rock materials are loosened or dissolved
and removed from any part of the earth's surface. The
major forces which remove these materials are the actions
of wind, water, ice and gravity. On construction sites in
the western United States, wind and water are the two prime
erosive forces, with gravity also acting as an agent of
erosion in small, localized areas.
In particularly young geologic areas, such as the
study area, where soil materials are not well established
and acidity contributes to sparse vegetation, natural
erosion (i.e., in areas undisturbed by human activities)
may be severe and account for high sediment transport loads
by streams. Disturbances by construction activities of a
previously natural area increases or accelerates this ero-
sion even more.
In the wind erosion process, soil particles are picked
up and transported by the wind. The amount of wind erosion
which occurs on a construction site depends upon the climatic
conditions and soil characteristics at the site. The most
severe wind erosion will occur in arid areas where rainfall
is scarce and little vegetation exists, and in areas of
fine-grained soils, i.e., silts and clays.
Wind erosion rarely causes extensive damage to a con-
struction site from a soil loss standpoint. The main con-
cern with wind erosion is the increase in airborne dust and
resultant air pollution.
Gravity-related erosion usually occurs through land-
slides and soil slippage. Mass movements of soil may
result from the construction of excessively steep or other-
wise unstable slopes. This form of erosion can be a serious
source of sediment pollution along waterways where slippage
or sloughing of soil results in the direct introduction of
the soil into the waterway. Massive earth-moving activities
along waterways, such as dam construction and major highway
construction, have the most potential for causing water
pollution due to gravity erosion.
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Erosion by water is the most prevalent form of erosion
on most construction sites. There are two main kinds of
water-caused erosion: overland or sheet flow erosion, and
erosion initiated by concentrated flows such as those which
occur in gullies and streambeds.
Overland erosion begins through the action of "rain-
splash." Rainsplash is the impact of a raindrop on a bare
soil surface. The force of the impact breaks larger soil
aggregates down into finer particles, which are more vulner-
able to removal by ensuing runoff. The impact also dis-
lodges the finer soil particles and starts their transpor-
tation away from the area by sheet flow. Additional damage
is also done when finer particles settle or are driven into
soil pores, causing a decrease in the rate that water pene-
trates into the soil. As a result of this "surface sealing,"
runoff increases and additional soil is detached and trans-
ported downslope. The magnitude of soil loss resulting
from rainsplash can best be seen on a gravelly or stony
soil. The striking raindrops dislodge the soil not shielded
by stones, leaving a pillar of soil under each stone. The
pillars shown on Figure 1 are up to an inch (three centi-
meters) in height. It would not be unreasonable to assume
that an average of about a half.inch (1-1/2 centimeters) of
soil was removed from this surface. That much removal
reflects a soil loss of approximately 100 tons per acre
(224 metric tons per hectare).
When enough rain has fallen, it begins to accumulate
on the surface and flow downhill. As well as carrying away
soil particles detached by rainsplash, the flowing water
detaches additional soil. This thin layer of flowing water
is often referred to as "sheet flow."
As the water begins to collect in small rivulets, con-
centrated flows begin. These concentrated flows start to
erode more soil and form rills. Rills are localized small
washes in defined channels which are small enough to eli-
minate by normal agricultural tilling methods (Figure 2).
Eventually, these rills may evolve into large gullies or
arroyos many feet (meters) deep and hundreds of feet (meters)
long.
When surface stormwater reaches a stream it may cause
accelerated stream channel erosion. This form of erosion
often takes place in intermittent or permanent stream
channels as a result of such factors as increased runoff
from developing areas, the removal of natural vegetation
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Figure 1. Soil pillars left by raindrop impact.
Figure 2. Rills formed by soil erosion on a slope.
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from stream banks, and channel alteration on construction
projects. Stream channel erosion causes the greatest
damage in urbanizing areas where a large increase in runoff,
coupled with construction encroachment onto floodplains,
results in massive channel degradation and increased
capability to transport sediment downstream. The severity
of the erosion which takes place on any construction site
is influenced by a number of factors. Of prime importance
are the physical factors of climate, vegetative cover,
soil, and length and steepness of the slope.
The climatic factors affecting erosion include the
amount, intensity, and frequency of rainfall and the
ambient temperature. Although it is not possible to modify
the climatic factors in order to control erosion on a con-
struction site, it is necessary to understand the influence
which these factors have on erosion potential so that ade-
quate protection can be designed.
Erosion is normally more severe in areas having
abundant rainfall than in areas having little rainfall.
However, intensity and frequency of rainfall must be con-
sidered when comparing areas of similar precipitation.
Both of these factors influence the amount of runoff.
Runoff occurs when the intensity of the rainfall exceeds
the infiltration rate of the soil. Frequency of rainfall
influences the moisture content of the soil, which in turn
has a major influence on the infiltration rate. The
higher the moisture content, the lower the infiltration
rate and the greater the potential for runoff.
In regions of the country subject to prolonged ground
freeze and considerable snowfall, temperature has a major
influence on erosion. A frozen and/or snow covered soil is
highly resistant to erosion. However, rapid thawing
brought on by warm spring rains can lead to serious erosion.
Vegetation is one of the most desirable materials for
controlling soil erosion. It performs a number of important
functions, including shielding the soil from the impact of
raindrops, retarding surface flow of water thereby permit-
ting greater infiltration, maintaining a pervious soil
surface capable of absorbing water, and removing subsurface
water between rainstorms by transpiration. To perform well
as a check on erosion, vegetation should be in good condition.
Soil properties most closely associated with erodi-
bility are texture, structure, and moisture content.
Texture refers to the relative distribution of the various
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size soil particles. A fine-textured soil having large
amounts of silt and fine sand or highly expansive clay
minerals is most susceptible to erosion. Soil structure,
on the other hand, refers to the arrangement of particles.
It influences both the ability of the soil to absorb water
and its physical resistance to erosion. Granular struc-
tured soils containing large amounts of fine sands and
silts with little clay are usually more erodible than soils
with a blocky or massive structure or those which contain
more clay. Exposed subsoils generally have little struc-
ture and are highly erodible.
All other factors being equal, a long slope will
collect more runoff than a short slope. The more water
collected, the greater will be the concentration of water
flowing over the surface and, consequently, the greater the
likelihood that erosion will occur. The steepness of the
slope influences the speed at which the water flows. As
the steepness increases, water velocity and the amount of
soil erosion also increase. Another factor influencing
water velocity is surface roughness. The rougher the slope,
the slower the water flows, and as water velocity decreases,
erosion decreases.
Sedimentation
Soil erosion is only the first part of an overall
cycle during which soil or rock particles are detached and
moved. Sedimentation is the second part. This process
begins at the time the particles are removed and includes
both the transportation and deposition of these particles.
These two processes are closely interrelated because the
same set of physical factors determines whether sediment is
transported or deposited. Water actually transports soil
particles in two ways, these two ways are referred to as
suspended and bedload transportation. Suspended sediment
consists of the soil particles that are actually carried
and supported (suspended) by the water itself. It is
mainly the suspended sediment that gives runoff water the
cloudy or muddy appearance, as illustrated in Figure 3.
Bedload sediment consists of the larger soil particles that
slide, roll, or bounce along the channel bottom.
Three physical factors affect sedimentation: the
characteristics of the flow, the nature of the particles,
and the nature of the flowing fluid. The interactions of
these three factors will determine how sediment is trans-
ported and deposited.
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The first factor, the characteristics of the flow,
refers to the velocity and turbulence of the moving water.
The greater the velocity or turbulence, the greater will be
the amount of sediment transported in suspension and as
bedload. As the velocity and turbulence of flow is reduced,
the amount of sediment which can be transported is also
reduced, and some of the sediment which had been carried at
higher velocities will be deposited (Figure 4).
The second factor, the nature of the particles, relates
to the actual size, shape, and density of the particles in
the water. Smaller, lighter particles, such as silts,
clays, and fine sands, are more easily transported by
water. Larger, heavier particles, such as coarse sands,
are harder to transport and thus are the first to be deposit-
ed as the water velocity and turbulence decrease. The
lightest particles of clay are the last to settle out. In
fact, even after standing for several weeks in totally calm
water, many clay particles still remain in suspension.
The third factor which affects sedimentation, the
nature of the transporting fluid, is a relatively minor one
with respect to construction site conditions. The transport-
ing fluid is, of course, water, and both the temperature
and density of the water will affect the amount of sediment
which can be transported. However, taking into account the
range of both water temperature and density which occurs
naturally on construction sites as well as the expected
influence of all the other factors affecting sedimentation,
changes in these water characteristics will produce only
minor variances in sedimentation.
FIELD DOCUMENTATION
One of the most important activities which will help
to identify the nature and extent of sedimentation problems
which could occur on a specific construction site is the
on-site survey. Surveys should be conducted both before
and during construction in order to adequately plan for
erosion and sediment control and to make any necessary
changes in the plans as construction progresses.
Before construction, on-site surveys are needed to
identify potential problem areas which are not apparent
from the maps or other literature on the site. Site aspects
which should be looked for during these preconstruction
surveys include:
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Figure 3. Suspended sediment in runoff.
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0 Areas of sparse native vegetation;
a Evidence of stream bank cutting and bottom
eros i on;
o Steep stream gradients;
0 Critical slopes;
s Vegetation which should be preserved;
o Areas of highly erosive soils.
Evidence of any of the above conditions may warrant a
revision in the preliminary sediment control plans for the
site. The purpose of the preconstruction site survey is to
identify conditions such as those above which may produce
some additional problems in terms of nonpoint source
pollution as development progresses. If the appropriate
actions are taken during the planning stages, many of the
problems which could develop would be avoided.
During construction it is equally important that site
inspections for sediment pollution control be conducted.
Critical areas which were identified during the preconstruc-
tion site visits should be observed for any signs of deteri-
oration. Slopes should be observed for any rill formation,
which is a precursor of more serious erosion. Streams
should be observed for any signs of increased sedimentation
or degradation. Sediment located in relatively still or
flat gradient parts of streams is a sign of erosion problems
upstream. Bottom degradation and/or bank cutting indicate
excess storm flows. If such indicators are noticed in
time, corrective action can be taken before more serious
and, consequently, more costly erosion takes place.
MEASUREMENT
The amount of sediment in the runoff generated by a
construction site is a direct indication of the effectiveness
of the site's sediment control measures. Measurement of
the concentration of sediment in the runoff, then, is
important in order to determine the true nature and extent
of any erosion problems. Sediment concentration measure-
ments should be taken both before and during construction.
In this way, background sediment concentrations can be
determined and compared to during construction readings.
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Measurements should be taken at points where the
runoff becomes concentrated, downstream of critical areas
of the site, and at least one measurement should be taken
downstream of the entire construction site. It is also
important to obtain sediment measurements during rainfall
events, both before and during construction, since these
will be the times corresponding to increased erosion poten-
tial.
As discussed previously, sediment in runoff consists
of two components: bedload and suspended. It is extremely
difficult to measure the amount of bedload sediment which
is being transported by a stream and, especially, to make
comparisons between normal background bedload and that con-
tributed by erosion from a construction site [1]. There-
fore, in measuring sediment in streams, obtaining values
for the amount of suspended solids in the stream should be
stressed. These values are usually obtained by collecting
samples at selected sampling points and analyzing the sam-
ples in a laboratory for the concentration of suspended
solids. Instruments are available which can be installed by
the side of a stream to automatically measure the turbidity
of a pumped-through sample as the stream rises. However,
these instruments are fairly troublesome when used on con-
struction sites [1].
Sample collection can be done either by hand or through
the use of automatic flow samplers. There are over 60
models of commercially available or custom-designed auto-
matic samplers [2]. Although automatic flow samplers have
the advantage of preventing someone from getting wet while
collecting samples during a rainstorm, they cannot always
be relied upon to obtain representative samples of the
flow. For an accurate representation of the suspended
solids in the flow, a sample should be taken throughout the
entire cross section of the flow. Thus, a sample collected
with an automatic sampler with a fixed, single point intake
(illustrated in Figure 5), might not be representative of
the overall suspended solids concentration in the flow.
Probably the simplest way to implement a runoff moni-
toring program is to have samples taken on a regular,
periodic basis at designated spots by the construction con-
tractor's personnel. The results of the analyses can be
forwarded to the cognizant regulatory agency for review.
If the sampling results indicate increased soil loss, on-
site surveys by the appropriate personnel can be conducted,
and corrective action recommended.
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Figure 5. Vacuum type of automatic water sampler.
REMOTE SENSING TECHNIQUES
Remote sensing, in the form of aerial photographs, can
be a useful tool in the mitigation of pollutant runoff from
construction sites. Aerial photographs taken from both
satellite and airplane platforms are available for general
public use. However, vertical photographs taken from
airplanes are the most practical for use in identifying
potential sources of pollution at construction sites..
A number of different types of aerial photographic
images are available, including standard black and white,
color, and false-color infrared prints. Conventional
panchromatic aerial film is generally exposed through a
minus-blue filter and permits the recording of blue-green,
yellow, orange, and red light. When color film is used,
the entire visible light spectrum is usually recorded, and
thus a greater number of color differences can be distin-
guished than if conventional black-and-white film were
used. Special photographs, such as those taken with color
film used with filters, special color film, or infrared
sensitive film permit the accentuation of features which
are important in certain investigations. For example,
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false-color infrared prints can highlight areas where
vegetation is under stress, thus helping to identify poten-
tial problem areas such as where poor drainage exists or
where droughty, highly erodible soils are present.
The important elements of the photo image which aid in
interpretation are: relative photographic tone, color,
texture, pattern, the relation of one feature to its sur-
roundings, shape of a feature, size, and combinations of
the above recognition elements. Many of the above photo
recognition elements are only important when they are
analyzed by trained personnel in context with the general
characteristics of the study area. Thus, it is important
that persons both skilled in the interpretation of aerial
photographs and familiar with the physical and ecologic
features of the area of interest be involved in the inter-
pretation if remote sensing techniques are to be utilized.
Aerial photographs can be used both before a site is
disturbed by construction activity to determine the physical
parameters and erosional characteristics of the soils at a
site, and while construction is in progress to identify the
location and extent of any nonpoint source pollution prob-
lems. Preconstruction site photographs can be obtained at
a scale of 1:40,000 or larger, in most cases, through the
U.S. Geological Survey. The Survey maintains an extensive
computer bank of virtually all overhead photography obtained
by government agencies in the United States [3].
During a preconstruction site survey via aerial photo-
graphy, the most important group of characteristics which
should be investigated are those elements which collectively
comprise what is known as the "soil pattern" of an area.
The soil pattern refers to the physical conditions of a
soil and is reflected in the following characteristics
which can be interpreted from aerial photographs: landform,
drainage characteristics, erosional characteristics, rela-
tive photographic tone, color, vegetative cover, and land
use. Discussions of how each of these parameters affect
the soil characteristics which are important to construc-
tion site investigations have been given by Raz [4] and
Strandberg [5].
16
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MATHEMATICAL PREDICTIVE TECHNIQUES
Background
Another important tool in understanding the possible
consequences of erosion on construction sites is the use of
mathematical computational techniques to estimate the
amount of soil expected to be lost from a construction
site. In order to appreciate the consequences of erosion
from a construction site, the relationships between soil
loss, sediment yield, and sediment delivery ratio must be
understood.
Soil loss is the gross, or total, amount of soil actu-
ally removed by erosion from a given watershed. It is the
summation of all types of erosion occurring within the
watershed. The total amount of sediment outflow from a
watershed or drainage basin, measured at a reference cross
section in a specified period of time, is referred to as
the sediment yield. The sediment yield of a given area
varies with changing patterns of precipitation, vegetative
cover, and land use. The sediment delivery ratio is that
fraction of the soil removed by gross erosion which is
delivered to any designated downstream location. All three
of these terms are related by the expression:
where:
D = sediment delivery ratio
Y = the sediment yield
E = gross erosion
Computational Techniques for Soil Loss from Sheet and Rill
Erosion
Recognizing the importance of the need for predicting
soil loss and sediment yield, numerous empirical methods
for estimating these parameters have been developed.
However, their use is limited primarily to the areas east
of the Rocky Mountains. Recently, some research as been
performed in an effort to extend some of the predictive
techniques to the western United States. Following are
brief discussions of some of the more pertinent techniques
which are applicable in the West.
1 7
-------
Musgrave Formula--
G.W. Musgrave was the first to produce an empirical
equation for computing soil loss [6]. His equation is:
A = F (R/100) (S/10)1•35 (L/72.6)0,35 (P3Q/1.25)1 * 75
where:
A = probable soil loss, in tons per acre per year,
F = a soil factor, based upon the erodibility of the
soil and other physical factors,
R = a cover factor, which may be the product of several
factors related to the use of the land,
S = steepness of slope, in percent (with 10 percent as
the base) ,
L = slope length, in feet (with 72.6 ft as the base),
P = rainfall (the amount used is the maximum 30-min.
rainfall expected in the locality from a 2-yr
frequency event, in inches).
This equation, has been used for several, years by the Soil
Conservation Service to estimate sheet erosion. The values
for the various factors vary for different sections of the
United States.
Modified Musgrave Formula--
A modification of the Musgrave equation was used by
Beer, Farnham, and Heinemann in a study of sediment yields
in western Iowa [7]. Some use has been made of this
equation, which is:
A = 0.59 (KR/150) P(R/100) (S/10)1,35 (L/72.6)0,35
where:
A = the average annual soil loss, in inches per year,
18
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KR = the product of the soil erodibility factor and
the rainfall factor from the Universal Soil Loss
Equation,
P = the supporting conservation practice factor from
the Universal Soil Loss Equation,
R = cover factor (fallow or continuous row crop equal
100),
S = degree of land slope, in percent (with 10 percent
as the base),
L = length of land slope, in feet (with 72.6 ft as
the base),
SCS Modification to Musgrave Formula--
Another modification of the Musgrave equation, which
has been extensively used by the Soil Conservation Service
[7], substitutes the K and R factors from the Universal
Soil Loss Equation for the F and P factors of Musgrave.
This equation is:
A = KCR (S/10)1 * 35 (L/72.6)°* 35
where:
A = sheet erosion, tons per year,
K = soil erodibility factor,
C = cover factor,
R = rainfall factor,
S = land slope, in percent,
L = length of slope, in feet.
Universal Soil Loss Equation--
The Universal Soil Loss Equation [8] assumes that the
rates of sheet and rill erosion depend on the following
factors:
a Rainfall energy and intensity,
19
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• Soil erodibility,
e Length and steepness of slope,
e Condition of the soil surface and the land
management practices in use, and
• Surface cover.
The above five factors have been combined in the Universal
Soil Loss Equation as:
A = RKLSCP
where:
A = estimated average annual soil loss, tons/acre
R = rainfall factor
K = soil erodibility factor
L = slope length factor
S = slope gradient factor
C = soil cover and management factor
P = erosion control practice factor
Experience by the U.S. Soil Conservation Service has
shown that the rate of upland soil erosion depends on the
above parameters. These erosion-inf1uencing factors are
combined into the equation which is a comprehensive
technique for estimating soil loss from upland
slopes. Thousands of plot-years of data from runoff plots
and small watersheds in 37 states east of the Rocky Mountains
have been statistically analyzed in an effort to perfect
this method.
With this equation, land planners can estimate gross
erosion rates due to combinations of different rainfall,
soil, slope, and soil management practices and thus deter-
mine total erosion rates for various alternative management
practices. Thus, this equation can be used as a planning
tool by showing how much the potential erosion can be reduced
by each of many available management choices. The equation
20
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provides a systematic, tested procedure for translating
accumulated research results into sound erosion and sedi-
ment control practices on a specific construction site.
To show how the equation can provide specific answers
for each construction site, it is necessary to consider
briefly the meaning and significance of each of its six
factors and the form in which locational information on
each factor is available.
Rainfall factor--Detaching and transporting soil mate-
rial requires energy. This energy is supplied by falling
raindrops and runoff. Therefore, the capability of a given
rainstorm to erode soil depends on the total energy of its
billions of raindrops at impact, and on the amount and
velocity of runoff available to both transport the pre-
viously detached particles and detach additional particles.
The rainfall erosion index, EI, is a measure of the total
raindrop energy of a storm, and is related to the maximum
30 minute rainfall intensity [9]. Soil losses are linearly
proportional to the number of EI units. Therefore, storm
EI values are summed in the computational procedure to
obtain an annual rainfall erosivity index for a given loca-
tion. This parameter serves as the rain fa 11 factor, R, in
the erosion equation and is related to the rainfall erosion
index by:
where E is the storm energy in foot-tons/acre-inch and I is
the maximum 30-inch intensity in inches per hour.
The rainfall factor, R, is computed from rainfall
records of individual storms and summed over a given time
interval to obtain the cumulative R value to be used in the
soil loss equation. R is derived from probability statistics
and thus should not be considered a precise estimator of
soil loss. Its value lies in its use as a predictive tool
and risk evaluator.
Using research data that describe the relation of
raindrop size, terminal velocity, and kinetic energy to
rain intensity, values of the rainfall factor were computed
from 22-year precipitation records throughout the 37 states
east of the Rocky Mountains. These were published as an
iso-erodent map (Figure 6). The R factor maps prepared to
date cover most areas east of 104° west longitude but
nothing in the western United States.
21
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EI factors have yet to be evaluated from actual
rainfall data for areas west of the Rocky Mountains. The
Agriculture Research Service Soil Loss and Runoff Labora-
tory has, however, provided interim EI and R data that may
be used only in nonorographic rainfall areas within the
western United States [10]. Separate EI and R data for
orographic areas in the western United States are expected
to become available in the near future.
For the Rocky Mountain states, reasonably accurate
approximations of local EI values can also be obtained from
two-year, six-hour rainfall probabilities. A publication
of the U.S. Soil Conservation Service [10], shows a curve
for the western part of the United States for the relation-
ship between the two-year, six-hour rainfall depth and the
EI value, with a correlation (r^ = coefficient of deter-
mination) of approximately 90 percent. This regression, in
combination with the two-year, six-hour rainfall maps given
in Weather Bureau Technical Paper No. 40 [11] and NOAA
Atlas No. 2 [12] can be used to determine R factors for
the Region VIII area from the relationship R = EI/100.
22
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Soil erodibility factoi—Some soils are much more
easily eroded than others because of differences in their
natural properties. The most significant soil characteris-
tics affecting soil erodibility are its particle size dis-
tribution, organic matter content, soil structure, and
permeability. Nomographs are available which can be used
to compute the value of K for any soil type [10]. For the
soils on the major erosion research stations, the measured
values of K have ranged from 0.03 to 0.69, a 23-fold varia-
tion [ 9 ].
Finding a way to determine where within this broad
range of K values each of the thousands of topsoils and
subsoils in the United States belongs has posed a difficult
problem for researchers. However, a method for computing
a soil's erodibility without soil-loss measurements now has
been developed. A new statistical parameter was found that
reflects the interrelations of the sand, silt, and clay
fractions of a soil [13]. Building on this knowledge,
additional relationships were established that now make
dependable prediction of a soil's erodibility possible from
knowledge of its particle size distribution, organic matter
content, structure, and profile permeability. The relation-
ships were combined in a nomograph, shown as Figure 7, that
graphically computes the value of K for a topsoil or a sub-
soil horizon in just four moves [13].
Slope length and steepness factors, L and S--The
potential of runoff to transport soil particles increases
approximately as the fifth power of its velocity, and its
detachment capability increases as the square of its
velocity [9]. The velocity of runoff increases as the
amount of flow increases, as the flow concentrates or as
the slope steepens. Therefore, the erosive potential of
runoff increases substantially as either slope length or
steepness increases.
In field practice, slope length and degree of slope
are combined into a single topographical factor, LS. The
LS factor can be obtained from charts which are available
in the published literature. The slope-effect charts
reproduced in Figures 8 and 9 show the relationship between
erosion and percent and length of slope as compared to a
basic research plot slope of nine percent and 72.6 feet in
length.
23
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ro
-p*
Figure 7. Soil erodibility nomograph [13].
-------
To illustrate the effect of these factors, for example,
a 300-foot length of eight percent slope produces an LS
value of 1.72 from Figure 8. This means that because of
the increased concentration of runoff from the example
slope, the total erosive potential of a rainfall and its
associated runoff would be 1.72 times as great on this
slope as on the basic plot slope of nine percent and 72.6
feet in length. The combined product RLS in the erosion
equation is, then, a numerical index of the total erosive
potential of the rainfall and runoff [9].
When the slope under consideration is complex, the
erosion is obviously not the same as the average slope.
Rather, when the lower end of the slope is steeper than the
upper end, the gradient of the steeper segment is used in
the computations along with the overall slope length.
Soil cover and management factor, C--The management
factor accounts for the effects of plant mulch cover and
soil surface conditions. This is a complex factor to
evaluate because of the many different soil covers and
management combinations which are usually present in a
given area. The values of the C factor vary from 0 to 1.
For a bare, cultivated soil with a relatively smooth surface,
C = 1.0. Mulches such as straw, stone, and woodchips can
reduce C to only a small percentage of that for bare soil,
and the C factor of well-established sod is essentially
equal to zero.
Some soil cover and management factor values for con-
ditions such as those encountered in the sparse vegetation
rangeland areas of the western United States have been
developed [10].
Erosion control practice factor--This factor accounts
for the effect of conservation practices such as interceptor
terraces and contour strips of vegetation. The application
of contour practices reduces soil erosion in varying amounts,
depending upon the practice and the length and degree of
slope. When no such practices are used, P = 1.0. P values
for various types of control practices are shown in Table
1 .
25
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rv>
-------
SLOPE LENGTH (feet)
Figure 9. Equivalent slope lengths for use of
slope-effect chart when the value of the pertinent slope
exponent is not 0.5 (assume m = 0.6 when slopes are
steeper than 10 percent and m = 0.3 when slopes are
very long with less than 1/2 percent gradient)[9].
27
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TABLE 1. "P" VALUES FOR VARIOUS TYPES OF CONTROL PRACTICES
Land
Slope
P Values
I
Contouring
Contour
S tri pcroppi ng
Terracing
3 4
2.0
to
7
0. 50
0. 50
0. 50
0.10
8. 0
to
12
0.60
0. 30
0.60
0.12
13.0
to
18
0. 80
0. 40
0. 80
0.16
19.0
to
24
0. 90
0.45
0. 90
0.18
3
For erosion-control planning on farmland.
4
For prediction of contribution to off-field sediment load.
Example Computation--Fo11owing is an example of the use
of the Universal Soil Loss Equation to predict sediment yield
from a construction site located in the study area.
Step 1 With the use of standard U.S. Department of
Agriculture area soils data (See Appendix A
for list of available information):
A. List the soil layers in the a rea of
concern
B. Note soils to be removed or stockpiled
-soil horizons may be determined from
core borings if taken in the area prior
to construction
-determine silt and very fine sand
content
-determine percent organic material
-determine soil structure
-classify permeability
28
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For this example, assume a development being
planned in an area in Powder River County,
Montana, on a Nihill Series soil with 8 to
15 percent slopes. From soil classification
data obtained from U.S. Department of Agri-
culture literature, the detailed description
of this soil as given in Table 2 can be
obta i ned.
Step 2 Determination of K value
A. From standard USDA data on soil samples
of 6 to 7 inches of newly exposed soil
or stockpi1ed soil:
-add silt fraction to very fine sand
content (in this case sand 49%, silt
+ fine sand = 51%)
-start at left of Figure 7 with percent
silt and very fine sand
B. Proceed horizontally to intersect cor-
rect percent sand curve (49 percent)
C. Proceed vertically to correct organic
matter curve (between 0 and 1 percent)
D. Proceed horizontally right to get first
approximation of K value (approximately
0.45)
-If the soil structure of the exposed
soil horizon is other than fine granu-
lar, or the permeability is other than
moderate, continue through the nomograph
parallel to the dotted lines.
E. Proceed to the right intersecting the
appropriate soil structure curve (in
thi s case equal to 3).
F. From the soil structure curves proceed
down to the permeability curves (class
2) and proceed left to the second
approximation of K equal to 0.46. This
value of K would then be used in the
equation.
29
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TABLE 2. DETAILED SOIL DESCRIPTION [14]
Soi 1
Hori zon
A1
CI
C2
Depth
(in.)
0-8
8-35
35-60
Texture
Class
coarse, granular
structure
massive, coarse,
thin, granular
platy structure
massive, coarse
granular
Particle Size (rrcn)
Sand Very Fine Sand Silt
0.32 to 4.6 0.074 to 0.32
Percentage Passing
59
41
41
51
34
34
.074
27
15
15
OM
Structure*
Code
Permeability*
Class
*See Figure 7 for code and class.
-------
Step 3
Determination of LS
Assuming a slope length of 300 feet and a
eight percent slope, the LS value from
Figure 8 equa1s 1.7.
Step 4 Without soil conservation practices (C and
P = 1), the soil loss in tons per acre, with
a R = 38 foot tons/acre/hour, determined
through data developed by NOAA [11,12], would
be:
A = RLSKCP
A = ( 38)( 1.7)(0.46)(1 )(1 )
A = 29.7 tons per acre
With the Nihil! Soil Association, an average
soil loss of 30 tons per acre per year can
be expected on an eight percent slope. In-
corporation of various conservation practices
will lower both the C and P values in the
equation, and consequently reduce total
annual soil loss.
Discussion--Use of various factors in the Universal
Soil Loss Equation to compute soil loss requires some judge-
ments based on the experience of the planner. This equation
is a planning tool that can be helpful to both the farmer
and the urban-development planner. It not only quantita-
tively predicts the seriousness of the erosion problem, but
it can also show how much of the potential erosion can be
reduced by each of many available management choices. There
are, however, certain considerations which should be recog-
nized while using this equation. These include:
o This predictive technique was designed to only
predict soil loss from sheet and rill erosion
caused by rainfall. Erosion from gullies and
stream channels should also be calculated in order
to obtain the gross erosion occurring in a water-
shed above the location of interest.
• The soil loss predicted by the equation is that
soil moved off the particular slope segment repre-
sented by the selected topographic factor. To
31
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estimate sediment yield, deposition of soil at
the base of a slope and elsewhere within the
watershed should also be accounted for. The
equation does not account for this deposition.
• The equation computes the long term average
annual soil losses for specific combinations of
physical and management conditions.
e Soil losses computed by the equation must be
recognized to be the best available estimates
rather than absolute data. All empirically
derived prediction equations involve experimental
error and potential estimation error due to the
effects of unmeasured variables and the skill of
the user.
• Soil loss estimates from construction areas are
less accurate than cropland estimates because C
values for this condition have not been determined
as accurately as for cropland conditions.
In addition, the use of predictive techniques such as
the Universal Soil Loss Equation for determination of soil
loss in an arid or semiarid area due to construction activity
might be less accurate than when applied to humid areas due
to precipitation variability and unregulated runoff because
of the scarcity of vegetative cover. The development of K
values corresponding to soils in the study area is needed.
Data is required with regard to natural erosion rates, area
rainfall variations, and better defined soil characteristics.
With vegetative cover playing a very important role in the
erosion process, the need for reclamation procedures uti-
lizing durable, low maintenance vegetation must be stressed.
The erosion process is complex in the study area, and
may prove to be outside the realm of the present day
Universal Soil Loss Equation's predictive character. Con-
struction sites should be monitored and compared to natural
erosion processes and feasible sediment and erosion techni-
ques developed in the eastern U.S. should be utilized and
their effectiveness categorized.
32
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Gully Erosion
Gully erosion produces channels larger than rills.
These channels carry water during and immediately after
rains and, as distinguished from rills, gullies cannot be
obliterated by normal tillage practices. The rate of gully
erosion depends primarily on the runoff-producing character-
istics of the watershed such as the drainage area and soil
characteristics; the alignment, size, and shape of the
gully; and the slope of the land surface.
A gully develops by processes that may take place
either simultaneously or during different periods of its
growth. These processes are waterfall erosion at the gully
head, channel erosion caused by water flowing through the
gully or by raindrop splash on unprotected soil, alternate
freezing and thawing of the exposed soil banks, and slides
or mass movement of soil in the gully. Four stages of
gully development are generally recognized [15].
• Stage 1: Channel erosion by downward scour of
the topsoil. This stage normally proceeds slowly
where the topsoil is fairly resistant to erosion.
• Stage 2: Upstream movement of the gully head and
enlargement of the gully in width and depth. The
gully cuts to the C horizon, and the weak parent
material is rapidly removed. A waterfall often
develops where the flow plunges from the upstream
segment to the eroded channel below.
• Stage 3: Healing stage with vegetation beginning
to grow in the channel.
• Stage 4: Stabilization of the gully. The channel
reaches a stable gradient, gully walls reach a
stable slope, and vegetation begins to grow in
sufficient abundance to anchor the soil and
permit development of new topsoil. The healing
stage is a necessary prelude to stabilization and
one stage grades into the other.
During the latter two stages of development the gully
head has progressed toward the upper end of the watershed,
and the rate of runoff into the gully head decreases because
the drainage area is reduced. The remainder of the runoff
enters at many points along the length of the gully.
33
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Of the several systems of gully classification, the
one given in Table 3 is based on an arbitrary classifica-
tion of gully sizes and drainage areas.
TABLE 3. DESCRIPTION OF GULLIES AND DRAINAGE AREA
Description
Small
Gully Depth , Ft
3 or less
Drainage Area, Acres
5 or less
Medi urn
3 to 15
5 to 50
Large
15 or more
50 or more
Another system classifies gullies with respect to their
cross sections. Gully cross sections may be V- or U-shaped,
depending upon soil and climatic conditions, age of the
gully, and type of erosion. U-shaped gullies may be found
in loessia 1 regions and alluvial valleys where both the sur-
face soil and the subsoil are easily eroded. Under such
conditions gullies tend to develop vertical walls which
result from undermining and collapse of the banks. The
scouring of soil by concentrated runoff in unprotected
depressions results in V-shaped gullies having sloping heads.
Such gullies may develop where the subsoil is resistant to
erosion. Both V and U shapes are commonly found in the same
channel. [7]
As gullies work upstream, the most active portion is
near the upper end or at the gully head, whereas the most
stable section of the gully is generally at the lower end.
Active gullies are gullies that continue to enlarge. They
may be identified by the presence of bare soil exposed on
the side slopes.
Evaluation and prediction of gully development is dif-
ficult because the factors leading to gully formation are
not well defined and field records of gullying are inade-
quate. From aerial photographs and field topographic surveys,
Beer and Johnson [16] developed a prediction equation for
the deep loess region in western Iowa. This equation, based
on a 20-year period and developed by statistical analysis
with the aid of a digital computer, is:
34
-------
where:
A = change in gully surface area in acres,
Q = index of surface runoff in inches,
Aj. = level terraced area of the watershed in acres,
L = gully length at beginning of period in feet,
L , = gully length from upper end to watershed divide
in feet,
I = deviation from normal precipitation in inches.
According to this equation, gully development is reduced by
an increase in the terraced area or by higher than normal
precipitation, and also progresses less rapidly when L. is
large, for example, when the gully first starts to eroae.
In the western United States, terracing has more effect
than in most areas because the channels hold the major
portion of the runoff. This equation would indicate a much
greater gully development in light soils than in soils
which are not as susceptible to erosion. The equation
delineates some of the factors, but it should not be con-
sidered applicable to other areas.
Wind Erosion
In the arid and semiarid study area where the soil
surface is often dry and protective vegetation is sparse or
absent, wind erosion is active. A study performed by Utah
State University indicated southern areas of Emery County
in Utah being the critical area most susceptible to wind
erosion [17].
A wind erosion equation has been developed to indicate
the relationships between the amount of wind erosion and
the various field and climatic factors that influence ero-
sion. The equation is expressed as:
A = F (I, K, C , L , V )
where:
A = amount of erosion in tons/acre/year
I = soil erodibility index
K = soil ridge roughness factor
35
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C = climatic factor
L = field length along the prevailing wind
erosion direction
V = equivalent quantity of vegetative cover
Charts and tables used for assigning values to vari-
ables used in the equation can be found in Agriculture
Handbook 346, U.S. Department of Agriculture.
Sediment Yield and Delivery
To be complete, any attempt at predicting the effects
of construction on the soils at a site must also address
sediment yield and sediment-delivery ratios. Delivery
ratios have been computed and in some cases prediction
equations have been developed for some physiographic areas
in the United States. These were related to watershed
characteristics [18, 19, 20, 21, and 22]. However, the few
areas studied represent only a small portion of the overall
country.
Glymph [23] presented some of the major aspects of the
computation of sediment yield and delivery ratios, and sum-
marized some of the major computational methods. Brief
summaries of some of these methods are presented below. It
must be remembered that little work has been done in this
field in the western states. The majority of the methods
were developed in conjunction with agricultural investiga-
tions, although the principles are generally universally
applicable.
The sediment-rating , curve-flow duration method re-
quires concurrent field measurement of streamflow and
sediment to establish an average relationship between
parameters of streamflow and sediment quantity. The method
is often used for establishing the amount of sediment
expected to reach large reservoirs or other points on
principal tributaries and main rivers. The method, how-
ever, is generally not applicable in estimating sediment
yields at problem sites in upstream watersheds because of
the difficulty and expense of obtaining the required data
for the large number of sites potentially of concern.
Problems are also encountered in using the sediment-rating
curve-flow duration method for estimating the effects of
erosion control measures upon sediment yield because of
imponderables and uncertainties in arriving at a sediment-
rating curve for conditions with the control measures in
effect.
36
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The reservoir sediment-deposition survey method in-
volves measurements by field survey of the volume of sedi-
ment accumulated in a pond or reservoir. The measured
volumes are converted into weights, adjusted for reservoir
trap efficiency, and expressed as rates of accumulation
according to the age of the reservoir or the time interval
between surveys. Deposition surveys on a number of reser-
voirs in a land resource area, watershed, or river basin
are often compiled and summarized to show relationships
between sediment yields and size of drainage area. This
approach gives useful general information on the magnitude
and variation of sediment yield in the region of interest,
but has limited value for forecasting sediment yield from
an individual watershed where no measurements have been
obtained. The method also has limitations in estimating
the effects of control measures on sediment yield.
The sediment-delivery ratio method requires a factor
expressing the percentage relationship between sediment
yield from a watershed and gross erosion in the watershed
in the same time period. Sediment-delivery ratios are
developed from the sediment yields obtained by reservoir
surveys or measurements at suspended-1oad stations in com-
parison with erosion in the watershed. The erosion quanti-
ties for sloping uplands are computed by erosion prediction
equations and are estimated by various procedures for
gullies, stream channels, and other sources. In opera-
tional programs, derived erosion quantities for sloping
uplands sediment-delivery ratios give estimates of sediment
yield. Since the method deals with calculated and esti-
mated quantities of erosion on the watershed with and
without treatments, it has a rationale for estimating the
effects of control measures upon sediment yield, under the
assumption that the same sediment-delivery ratio applies
for both the "before" and "after" conditions. Sediment-
delivery ratios have been developed for much of the eastern
half of the United States, but scanty rainfall data and
other complicating factors have precluded use of the method
in the West.
Bedload function methods make use of mathematical
equations developed for calculating the rate and quantity
of movement of material constituting the bed of alluvial
channels. Application of these equations requires informa-
tion on sediment particles sizes, channel gradients and
cross sections, and a flow-duration curve. The equations
often give widely different results for the same condi-
tions.
37
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In each of the methods, the watershed is treated as a
lumped system. They deal with the watershed as a whole,
rather than with its constituent features, in deriving the
quantity of sediment expected at a point on the watershed.
Although, in the sediment-delivery ratio method erosion
rates are calculated separately for significant sites, they
are then aggregated and the total compared with a measured
sediment amount for the watershed as a whole. In effect,
therefore, this method also treats the watershed as a
lumped system.
38
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REFERENCES
1. State of Maryland Water Resources Administration, and
B.C. Becker, D.B. Emerson, M.A. Nawrocki, Joint
Construction Sediment Control Project, EPA Document
No. EPA-660/2-73-035, April 1974, 167 pp.
2. Shelley, Philip, E., and G.A. (Kirkpatrick, An Assess-
ment of Automatic Sewer Flow Samplers, EPA Document
No. EPA-R2-73-261, June 1973, 233 pp.
3. U.S. Department of the Interior, Geological Survey,
National Cartographic Information Center, Aerial
Photography Summary Record System Catalog, Catalogs
2, 3, 4, 5.
4. Ray, Richard G. , Aerial Photographs in Geologic
Interpretation and Mapping, U.S. Geological Survey
Professional Paper 373, 1960, 230 pp.
5. Strandberg, Carl H., Aerial Discovery Manual, John
Wiley & Sons, Inc., New York, 1967, 249 pp.
6. flusgrave, G.W., "The Quantitative Evaluation of Factors
in Water Erosion," a first approximation, J. Soil Water
Conserv., Vol. 2, No. 3, July 1947, pp. 133-138.
7. Ireland, H.A., and others (1939) Principles of Gully
Erosion in the Piedmont of South Carolina, U.S. Dept.
Agr. Tech. Bull. 633.
8. "A Universal Equation for Predicting Rainfall Erosion-
Losses", U.S. Agr. Res. Serv., Spec. Rept. 22-26, March
1 961.
9., Wischmeier, "The Erosion Equation - A Tool for Conser-
1 vation Planning."
10. U.S. Department of Agriculture, Soil Conservation Ser-
vice, Procedure for Computing Sheet and Rill Erosion
on Project Areas, Technical Release No. 51, Sept. 1972.
11. Hershfield, "Rainfall Frequency Atlas of the United
States", U.S. Weather Bureau Tech. Paper 40, 1961.
12. Precipitation-Frequency Atlas of the Western U.S.,
National Oceanic and Atmospheric Administration,
USDC, 11 volumes, 1973.
39
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REFERENCES (continued)
13. Wischmeier, W.H., C.B. Johnson, and B.V. Cross, "A
Soil Erodibility Nomograph for Farmland and Construc-
tion Sites."
14. Soil Survey-Powder River Area, Montana, U.S. Depart-
ment of Agriculture, Soil Conservation Service,
Issued June 1971.
15. Soil and Water Conservation Engineering, The Ferguson
Foundation, Schwab, G.O., John Wiley and Sons, Inc.,
New York, NY, 1966, pages 165-167.
16. Beer, C.E., and H.P. Johnson (1963) "Factors in Gully
Growth in Deep Loess Area of Western Iowa," Am. Soc.
Agr. Engr. Trans. 6, (No. 3), pp. 237-240.
17. Roadruff, N.P., R.H. Siddoway, "A Wind Erosion Equa-
tion," S.S.S.A.P. 29 (5), pp. 602-608, 1968.
18. Gottschalk, L.C., and Brune, G.M., "Sediment Design
Criteria for the Missouri Basin Loess Hills," SCS TP-97,
U.S. Department of Agriculture, Oct., 1950.
19. Maner, Sam B., "Factors Affecting Sediment Delivery
Rates in the Red Hills Physiographic Area," Trans-
act i o n s, American Geophysical Union, Vol. 39, Aug.,
1 958.
20. Maner, S.B., and Barnes, L.H., "Suggested Criteria for
Estimating Gross Sheet Erosion and Sediment Discovery
Rates for the Blackland Prairies Problem Area in Soil
Conservation," SCS Publication, U.S. Department of
Agriculture, Feb., 1953.
21. Roehl , J.W., "Sediment Source Areas, Delivery Ratios
and Influencing Morphological Factors," Publication 59,
International Association for Scientific Hydrology
Commission of Land Erosion, 1962, pp. 202-203.
22. Williams, Jimmy R., and Berndt, Harold D., "Sediment
Yield Computed with Universal Equation," Ameri can
Society of Civil Engineers, Journal of the Hydraulics
Division, No. HY 12, Proceedings Paper 9426, December
1972, pp. 2087-2098.
23. Glymph, Jr., L.M., "Evolving Emphases in Sediment-Yield
Prediction," Proceedings of the Sediment-Yield Workshop,
Oxford, MS, 1972.
40
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SECTION 3
SEDIMENT CONTROL TECHNOLOGY
INTRODUCTION
In controlling sediment at construction sites, the
objective is to prevent a major portion of that sediment
generated as a consequence of the construction from entering
waterways, contaminating water supplies, destroying wild-
life, impeding navigation, causing aesthetic damage, and
damaging off-site property. An added benefit of such control
is a reduction in physical damage to the construction site
and adjoining properties due to soil erosion and flooding.
Sediment control is an inexact and developing tech-
nology. Achieving best control requires flexibility, inno-
vation, and common sense, coupled with an understanding of
control principles, and a knowledge of previously applied
and proven practices. It is important to recognize that the
basic control principles outlined in this section are uni-
versally applicable. They apply to the semi arid regions of
the country just the same as they apply to the more humid
eastern states. The basic control practices are also much
the same throughout the country, the major differences being
types of vegetation used for soil stabilization, seed bed
preparation (soil amendment and moisture retention tech-
niques), and sizing of perimeter sediment retention struc-
tures (sediment basins).
It is also very important to keep in mind that, even in
those areas of the country where we have several years of
experience in applying construction related control prac-
tices, we still have not perfected the art and science of
sediment control. Use of the best available technology by
innovative individuals skilled in the fields of hydrology,
soil science, and agronomy will always be the best way of
achieving reasonable control. Good enforcement of good
regulations is, however, of equal importance to the proper
application of control technology in achieving adequate
sediment control at construction sites.
41
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A comprehensive manual of practices to control construc-
tion associated sediment in the semiarid areas of the West
cannot yet be written. Before it can be done, more exper-
ience in the application of basic practices, particularly
structural practices such as sediment basins, must be gained.
The cost-effectiveness of various practices should be deter-
mined from field measurements. Customized, best available
technology can only come after experience has been gained
and research conducted.
Sediment is a product of erosion by both water and
wind. Although wind erosion is a significant source of
sediment in the study area, erosion from the impact of
raindrops and surface runoff is, for the most part, the
major source of sediment. Surface runoff is also the pri-
mary means by which sediment is carried into waterways.
The amount of sediment generated at a construction site
and delivered to a receiving stream is dependent on five
factors:
1. The extent and duration of the construction
disturbance;
2. The amount, intensity and duration of
rai nfal1 and wi nd ;
3. The resistance of the soil to the erosive
forces of .water and wind;
4. The amount, velocity, concentration, and
turbulence of the surface runoff; and
5. The distance from the disturbance to the
receiving stream and the physical nature
of the intervening terrain.
Of these critical factors, only one, the climatic factor
(item 2), is beyond the control of man. It is the best
manipulation of the other four factors upon which effective
sediment control depends.
CONTROL PRINCIPLES
A wealth of information on sediment control has been
developed over the years. Numerous manuals and reports are
available on various control practices. However, achieving
effective control not only depends on one's knowledge of
individual control practices, but also a thorough under-
standing of the basic principles of sediment control.
42
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There are five sediment control principles. They have
been modified from principles defined by the U.S. Soil
Conservation Service and are as follows:
1. Plan the development to fit the particular
topography, soils, waterways, and natural
vegetation at the site (Site Planning).
2. Expose the smallest practical area of land
for the shortest possible time (Construction
Planning).
3. Apply practices to prevent soil particles from
being detached by rainfall, runoff and
wind (Erosion Prevention).
4. Apply practices to trap sediment resulting
from unavoidable erosion as near its point of
origin as possible (Sediment Retention).
5. Implement a thorough follow-up maintenance
program for all sediment control practices
(Maintenance) .
Site Planning
Many of the more serious sedimentation problems can be
avoided through careful site planning. This requires that
sediment control be considered both in the selection of a
construction site and in the location of facilities within
the selected site. In addition to other factors, alter-
native sites or corridors should be evaluated with respect
to four factors affecting soil erosion and sedimentation:
soil characteristics, surface drainage, vegetation, and
topography. Critical areas such as waterways, steep slopes,
or highly erodible soils should be identified in the plan-
ning process. Once a site or corridor has been selected,
considerable care should be taken in the development of the
site plan to avoid disturbing critical areas. The guiding
principle must be to fit the development to the particular
topography, soils, waterways, and natural vegetation at the
site. In other words, think ahead and plan with nature to
avoid serious sedimentation problems. Careful planning can
result in both reduced damage and savings in project costs.
A good illustration of this idea was recently reported [1].
In an Ann Arbor, Michigan, housing development, swampy areas
which covered half the site represented a serious hindrance
to an economically viable development. Ingenious planning
43
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converted the swampy areas into ponds. These ponds, com-
bined with the open spaces shown in Figure 10, are the
aesthetic and recreational focal point of the development.
The ponds are used for skating in winter and boating and
fishing in the summer. Additionally, the ponds serve as a
flood control device. They are able to handle a 50-year
storm through a two-foot (0.61-m) rise in water level.
Figure 10. Open Space Along a Stream
in a Residential Area
Construction Planning
The second control principle, illustrated in Figure 11
is to expose the smallest area of land for the shortest
possible time. The reasoning behind this very important
principle is rather simple -- one acre (.405 hectares) of
exposed land on a hillside will yield less sediment than two
acres (.810 hectares) of exposed land on the same hillside,
and an area exposed for six months will yield less sediment
than the same area exposed for one year. The intent of this
principle should be clearly reflected in the construction
specifications and in the scheduling of construction opera-
tions. On large sites and along transportation and trans-
mission corridors, stage the construction operations such
that clearing, grading, and stabilization are largely com-
pleted in one area before disturbing another area. Timing
of construction operations is also important. To the maxi-
44
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mum extent possible, minimize grading activities during
rainy seasons of the year and promptly stabilize (either
permanently or temporarily) areas at the completion of final
grading. If an area must remain exposed for a prolonged
period of time due to a work shutdown or other reasons,
provide temporary stabilization to secure the area until
grading can resume or more permanent stabilization can be
provided. Good construction planning also requires that a
sediment control plan be developed. The plan should gra-
phically show the location of control structures to be used
at the site, contain specifications for the implementation
and maintenance of required structural and vegetative mea-
sures, and clearly explain scheduling requirements.
Figure 11. Staging of Grading and Stabilization
Activities at a Roadway Construction Site
Erosion Prevention
The third control principle is to apply practices to
prevent soil particles from being detached by rainfall, run-
off, and wind. This principle relates to using practices
that control soil erosion on disturbed areas to prevent
excessive sediment from being produced. Once detached and
moved from their initial resting places, soil particles
become sediment. By reducing the amount of sediment pro-
duced, more effective control is achieved and the cost of
trapping and disposing of sediment is minimized. The de-
45
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tachment process, or erosion, is accomplished for the most
part by the impact of falling raindrops and the energy
exerted by moving water (runoff) and wind. A reduction in
the rate of erosion (soil loss) is achieved by controlling
the vulnerability of the soil to erosion from water and wind
(soil stabilization) and/or the ability of moving water
(surface runoff) to detach soil particles (runoff control).
Sediment Retention
The fourth control principle is to apply practices to
trap sediment from unavoidable erosion as near its point of
origin as possible. Even with the best effort at control-
ling soil erosion, some sediment will be generated. Sediment
retention should not be viewed as a perimeter defense, but a
defense that begins at the point of detachment and extends
down to the perimeter of the construction site, or to the
point of entry into a waterway. A retention practice can be
as simple as a scarified surface which impedes the movement
of sediment down a slope (surface roughening), or as sophis-
ticated as a pond constructed on a drainageway at the peri-
meter of a site to detain sediment-laden runoff and thus
allow sediment to settle out of suspension (sediment basin).
In all cases, the trapping or retention of sediment on the
construction site involves the use of "runoff control"
practices, or, in the case of wind transport, "wind control"
practices. In other words, control is achieved by reducing
the ability of the transport medium (water or wind) to carry
the detached soil particles. When heavy concentrations of
silt and clay sized particles are expected, control is also
achieved by altering the settling characteristics of the
suspended particles. This is usually accomplished by the
addition of chemicals (chemical treatment) which cause the
small particles to agglomerate into larger particles (floc-
culation) which more readily settle out of suspension.
Ma i ntenance
Sedimentation problems can generally be traced to a
poorly conceived plan or failure to properly implement a
wel1-conceived plan. Failure to provide adequate mainte-
nance of control practices is too often the implementation
culprit. Just as a good plan is useless if not implemented,
properly installed structural or vegetative practices
provide less than optimal protection if required follow-up
maintenance is not performed.
46
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A thorough check of all control practices should be
made periodically and after each major rainfall event. When
inspections reveal problems, the necessary modifications,
repair, cleaning, or other maintenance operations should be
performed expeditiously. Particular attention must be paid
to water handling structures (i.e., diversions, sediment
traps, grade control structures, and sediment basins) and
areas being revegetated. Breaches in the structures or
areas being revegetated should be quickly repaired, pre-
ferably before the next rainfall event. When sediment
containment structures fill to capacity, they must be
promptly cleaned, and the sediment disposed of in a manner
that will not allow it to be reintroduced into the drainage
system. Disposal may include burying the sediment in a
stabilized area, spreading it thinly on stable slopes just
prior to seeding and mulching, or placing it upslope behind
stabilized soil dikes.
CONTROL PRACTICES
From a functional standpoint, sediment control prac-
tices can be divided into two categories: soil stabiliza-
tion practices and runoff control practices. It is true
that proper site planning is also a control practice, but,
for simplicity, the remainder of this section of the manual
will address only "field" practices. Wind control could
also be another category of control; however, wind breaks
and other wind control measures are expected to have very
limited application for construction related sediment con-
trol. Instead, soil stabilization practices and runoff
control practices can be expected to provide protection
against the erosive forces of both wind and moving water.
Soil Stabilization Practices
Soil stabilization is one of two major categories of
sediment control. The many techniques and materials in-
cluded in this control grouping are all designed to protect
the soil from the erosive action of falling rain, the ensuing
runoff and wind. Protection of the soil surface from the
full force of impacting raindrops and the hydraulic and
abrasive action of moving surface water and wind is achieved
by either binding the soil particles together to form a mass
that is less easily displaced, anchoring the soil in place,
shielding the soil surface, or a combination of these prac-
tices.
47
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Stabilization measures may be either vegetative or non-
vegetative and short-term or long-term. Vegetative stabi-
lization refers to the use of different types and combina-
tions of vegetation to protect the soil from erosion. Non-
vegetative stabilization, on the other hand, refers to a
multitude of practices that use materials other than vege-
tation in preventing soil erosion. Quite frequently a
combination of both vegetative and nonvegetative measures
are required for successful soil stabilization.
Short-term stabilization, also termed temporary stabi-
lization, refers to the use of practices that provide pro-
tection for a short period of time, i.e., usually less than
one year. Included in this group are numerous, fast-grow-
ing, short-lived grasses and legumes, various organic
mulches, and a wide assortment of chemical binders. Long-
term or permanent stabilization involves the use of long-
lived vegetation, or a durable material such as rock, con-
crete, or asphalt to protect the soil against erosion for a
period of time in excess of one year.
The type of measure selected will be greatly influ-
enced by hydraulic factors. That is to say, different
practices are used for large, relatively flat surfaces
subject to sheet flow than for ditches or other drainage
features that carry concentrated flow. The discussion of
stabilization practices that follows is subdivided into
those measures used to stabilize areas subject to mostly
sheet flow and measures used to protect areas subject to
highly concentrated flows.
Areas Subject to Sheet Flow--
A factor to be kept in mind when determining the degree
and type of stabilization for a particular slope is that
susceptibility to erosion from surface runoff increases with
increased slope steepness and increased slope length. Bind-
ing, anchoring, and shielding of the soil is accomplished by
one or a combination of vegetative and nonvegetative mea-
sures .
Vegetative stabilization — Providing proper care is
taken in its establishment, vegetation is the most bene-
ficial and durable soil stabilizer. It forms a protective
cover which shields the ground surface from the direct
impact of falling rain, and its roots bind and secure the
soil particles. It also controls runoff by slowing the flow
of water along the soil surface and by enabling the soil to
absorb more water. By reducing the amount of runoff and its
speed of movement, the ability of the runoff to carry away
detached soil particles is also decreased.
48
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Both long-term and short-term vegetative stabilization
are used. Long-term measures involve the planting of var-
ious combinations of perennial grasses, legumes, shrubs, and
trees. The type and mixture of individual plant species to
be used will depend on soil and moisture conditions, cli-
matic conditions, erosional stresses, and post-construction
land use.
Short-term vegetative stabilization involves the use of
low cost, quick growing annual and perennial grasses and
legumes to provide protection for a short period of time,
usually less than one year. This form of stabilization is
often used to protect stockpiled topsoiling material. It is
also used to temporarily stabilize areas graded in late
spring or fall when more permanent stabilization cannot be
properly performed.
Subsoils having high sodium absorption ratios (S.A.R.)
and climatic conditions make establishment of a low main-
tenance, dense, and durable cover of vegetation a difficult
proposition at many construction sites in the study area.
The surface sealing or "puddling" of high S.A.R. soils due
to rainsplash and the subsequent loss of infiltration capa-
city can be handled by topdressing troublesome subsoils
with salvaged topsoil or other soils having suitable phys-
ical and chemical properties. Prompt seedbed establishment
and use of straw or hay mulch will also reduce infiltration
problems and, thus, promote the development of a satisfac-
tory cover of vegetation.
Soil roughening techniques to enhance infiltration
and retention of water are also very important in establish-
ing a stable cover of vegetation in arid and semi-arid
areas. Contour chiseling and roughening techniques devel-
oped and demonstrated by Richard Hodder and others at
Montana State University have application in establishing
vegetation on soils that are difficult to stabilize [2].
More standard tillage practices such as discing and har-
rowing using normal farm machinery will generally suffice
where site conditions are not severe. All of the practices
loosen the surface soil and, when performed along the ground
contour, impede surface water runoff (thus increasing
infiltration) and, in most instances, reduce soil and nu-
trient loss.
49
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The types of vegetation used will also have a major
bearing on the degree of protection provided against soil
erosion at construction sites. Low maintenance, drought
tolerant plant materials providing a fairly dense ground
cover should be used in the study area. Greater flexibility
exists in the use of plant materials at construction sites
in the study area than exists at surface mines where the
disturbed land must be returned to certain agricultural
and wildlife uses.
In the study area, considerable experience has been
gained over the past decade in the use of various native and
introduced plant species for stabilizing roadway areas and
surface mines. It is recommended that the following sources
of direct assistance or general information be contacted
when selecting plant materials for a particular use and in
defining proper seedbed preparation and maintenance pro-
cedures :
s State Soil Conservation Service (District
offices)
o State Department of Transportation
• Agricultural Research Service (USDA)
• State Reclamation or Sediment Control
Agenci es
• State Universities (Agricultural Extension
Servi ces)
Nonvegetative stabilization—Like vegetative measures,
nonvegetative practices are used to reduce the susceptibi-
lity of disturbed soils to erosion. It is difficult to
separate the two major types of stabilization in that they
are often used together (Figure 12). An important point to
remember is that nonvegetative stabilization is used to
reinforce vegetative measures. Where vegetation will pro-
vide adequate long-term soil protection, long-term, non-
vegetative stabilization is not required. Where vegetation
will provide parti a 1 protection, such as on steep slopes
subject to erosive runoff velocities, a combination of the
two types of stabilization is required.
50
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Figure 12. Wood Fiber Mulch and Seed
Being Applied With a Hydroseeder
Nonvegetative stabilization covers a wide assortment of
short-term and long-term soil stabilization practices,
varying considerably in their cost-effectiveness and ability
to withstand erosional stresses. As a general rule, it is
usually best to stay with the "tried and true" practices
unless experience indicates otherwise. New products or
practices appearing worthwhile and offering possible cost
advantages should be demonstrated on test plots before being
employed extensively.
Mu 1 ching and chemical stabilization are two major
types of short-term, or temporary, nonvegetative soil
stabilization. Both are employed to provide protection
against excessive soil erosion for periods of time less than
one year. The major characteristics of the mulches which
might be available for use in the study area are summarized
in Table 4, while those of chemical binders and tacks are
summarized in Table 5.
Mulches are used in the establishment of a vegetative
ground cover to protect the seedbed from excessive erosion
prior to germination of the seeds, and until the new vege-
tation is sufficiently established. The mulch provides a
favorable environment for seed germination and plant de-
51
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Table 4
CHARACTERISTICS OF COMMONLY USED MULCHES
TYPE
DESCRIPTION
APPLICATION
REMARKS
Manure
Manure is available both as a mulch
and as a source of plant nutrients.
Recommended application rates for manure
range from 18 to 22 metric tons per
hectare (8 to 10 tons per acre)
Tests have shown that on 10 to 12
percent slopes, soil loss measured
1.1 metric tons per acre (0.5 tons
per acre) on areas mulched with
manure, compared to 28 metric tons
per hectare (12.5 tons per acre) on
unmulched areas.
Paper
Macerated paper, produced by passing
newspaper through a hammer-mill and
applied as a slurry can be used as a
mulch.
The paper is applied as a slurry at
approximately 1.7 metric tons per
hectare (1500 pounds per acre).
In tests conducted in Utah, paper
slurry gave satisfactory results but
was not as long-lasting as straw
tacked with asphalt, or wood fiber.
Straw/Hay
Loose straw or hay is the most conmonly
used, and one of the best temporary
soil stabilizing and mulching material.
It conserves soil moisture, dissipates
energy from falling raindrops, insu-
lation against intense solar radiation
and reduces erosion caused by overland
sheet flow.
Straw or hay can be applied by hand but
is best applied using a mulch blower that
shreds, cuts, and evenly scatters the
straw. It is best anchored using a
specially designed crimper or a form disc
pulled along the ground contour. Where
wind is not a major problem, straw or
hay can also be satisfactorily anchored
using asphalt or chemical binders, or
in extreme cases, netting. The appli-
cation rate for straw or hay varies with
local conditions but is generally about
4.5 metric tons per hectare (two tons
per acre).
Straw alone, straw plus asphalt, and
netting over straw have rated better
in tests than manufactured mulches.
Although many manufactured mulches
provide initial protection against
erosion, they fail to retain as much
soil moisture for grass establishment.
Excelsior The Erosion Control Excelsior Blanket
consists of a machine produced mat
of curled wood excelsior of 80% 20
centimeter (eight inch) or longer
fiber length. In a blanket form,
excelsior is used in the establish-
ment of vegetation on critical
areas, such as drainageways, steep
slopes, highly erodible soils, etc.
It conserves soil moisture, insu-
lates against intense solar radia-
tion, dissipates energy from falling
raindrops, and reduces erosion
caused by runoff.
The Blankets are available in 3' to 150'
rolls and in 4' x 180' rolls. They
are secured to the soil by the use of
heavy duty wire staples. Loose excel-
sior, cut into about 20 centimeter
(eight inch) lengths can be applied
with or without asphalt tack.
Loose excelsior has been rated as good
as straw tacked with asphalt. It has
also been rated superior to short-
fibered wood cellulose pulps for soil
protection and plant establishment.
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Table 4 (Cont.)
CHARACTERISTICS OF COMMONLY USED MULCHES
TYPE
DESCRIPTION
APPLICATION
REMARKS
Wood Fiber Wood fiber mulch is a fine-textured,
short-fiber wood product produced
from wood chips. It is designed
specifically for use in a hydroseeder.
It is best utilized on steep slopes
where conventional seeding and
mulching (straw or hay) practices
cannot be used, or on relatively
flat areas where soil erosion will
not be a significant problem.
In hydroseeder slurries, wood fiber mulch can
be applied along with seed, lime, and ferti-
lizer. The rate of application is generally
between 1.1 and 1.7 metric tons per hectare
(1000 and 1500 lb/acre).
Fiberglass Flexible fiberglass is an inorganic
material that will not rot, corrode,
or burn. Used in a mat or blanket
form (thin insulation batting), it
provides long-term resistance to
erosive forces. Like all fiberglass
material, the fibers are retained
in the root mat of the developing
vegetative cover, providing lasting
reinforcement.
Fiberglass (GLASSROOT ) can be applied
by spraying (compressed air) long strands
over the critical area. This results in
a deuse, stable mat that provides long-
term protection and a more suitable environ-
ment for plant growth. It can also be
applied in a blanket form by stapling
tightly to the ground.
Gravel (Crushed Gravel, or other resistant paving
Stone, material can be used by themselves
Clinker) or, preferably, in combination with
vegetation to provide permanent
surface protection.
N/A
Gravel or crushed stone, one-half inch or
greater in size, is able to suitably pro-
tect against rain splash and sheet flow
and can withstand wind velocities up
to 137 kilometers per hour (85 miles
per hour).
Jute Netting Jute netting is made up of thick,
fibrous strands of jute, and is one
of the most propular materials for
temporarily stabilizing and mulching
seeded drainageways. When properly
secured it shields the soil from the
erosive action of rain splash and
runoff and provides a favorable environ-
ment for seed germination and plant
development.
The netting is commonly available in indi-
vidual rolls, 225 feet long and 4 feet
wide. The material is secured to the soil
surface with staples 6, 8, or 10 inches
long.
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Tab!e 5
SUMMARY OF CHEMICAL BINDERS AND TACKS
NAME
USES
TEMPORARY
SOIL MULCH
STABILIZER MULCH TACK
DESCRIPTION
APPLICATION
METHOD
®
AEROSPRAY
52 BINDER
AEROSPRAY"
70 BINDER
Water d1spersible , alkyd
emulsion. Nontoxic,
flonphytotoxi c. pH 8-9
Water dispersible,
liquid polyvinyl acetate
emu 1s i on .
Any nonair entraining
equipmen: (as for liquid
fertilizer, asphalt emul-
sions, and water).
Hydroseeder. Seed, ferti-
lizer, and wood fiber may
be applied with product.
AEROSPRAY
72 BINDER
Water dispersible,
liquid alkyd emulsion
res i n.
Hydroseeder. Seed, ferti-
lizer, and wood fiber may
be applied with product.
AQUATAIN
CUP.ASOL AE
CURASOL AH
DCA-70
Water dispers i ble .
Nontox i c .
Non f1anmable.
Water dispersible, poly-
vinyl acetate copolymer
emu 1sion. Nontoxic,
flonphytotoxi c . pH 4-5
Water dispersible, high
polymer synthetic resin.
Nontoxic, 'lonphy to tox i c .
pH 4-5.
Water dispersible, poly-
vinyl acetate emulsion.
Nontoxic, flonphytotoxic .
Nonflammable. pH 4-6.
Hydroseeder or any nonair
entraining equipment.
Seed and fertilizer may
be applied with product.
Hydroseeder or any nonair
entraining equipment.
Hydroseeder or any nonair
entraining equipment.
Seed and fertilizer may
be applied with product.
Hydroseeder or any nonair
entraining equipment.
MANUFACTURER OR
PRODUCT INFORMATION
American Cyanimid Company
Industrial Chemicals and
Plastics Division
Wayne, New Jersey 07970
American Cyanimid Company
Industrial Chemicals and
Plastics Division
Wayne, New Jersey 07970
American Cyanimid Company
Industrial Chemicals and
Plastics Division
Wayne, New Jersey 07970
The Larutan Corporation
1424 South Allec Avenue
Anaheim, California 9280 5
American Hoechst Corporation
1041 Route 202-206 North
Bridgevater, New Jersey 08876
American Hoechst Corporation
1041 Route 202-206 North
Bridgewater, New Jersey 08876
Union Carbide Corporation
Chemicals and Plastics
270 Park Avenue
New York, New York 10017
-------
Table 5
SUMMARY OF CHEMICAL BINDERS AND TACKS
USES
NAME
TEMPORARY
SOIL MULCH
STABILIZER MULCH TACK
DESCRIPTION
APPLICATION
MSTHOP
MANUFACTURER OR
PRODUCT INFORMATION
GENEQUA 169
LIQUID ASPHALT
M-l 45
PETROSET SB
TERRA TACK
UREA-FORMALDEHYDE
FOAM
XB-Z386
Water disperslble, modi-
fled liquid acrylic
res 1 n.
Asphalt cement that 1s
dlspressed or suspended
in water or various
sol vents.
Water dlspersible
liquid resin polymer.
Water dlspersible oil
emulsion. Nontoxic.
Non f 1ammab1e.
pH 6.0 ± 0.5
Water disperslble,
powdered vegetable gum
Urea-formaldehyde resin
plus a foaming agent,
mixed and foamed with
compressed air, then ap-
pl led to soi1. Wetti ng
agent then appli ed to
foam. Seed and ferti-
lizer sprayed on top.
Water dlspersible,
liquid reactive polymer.
Hydroseeder. Seed, ferti-
lizer, and wood fiber may
be applied with product.
Hand-spray nozzel or an
offset distributor bar
attached to an asphalt
distributor truck.
Hydroseeder. Seed and
fertilizer may be applied
wi th product.
Any spraying equipment.
Hydroseeder or, for dry
application, standard
hopper spreaders (as for
fertilizers or lime).
Nonalr entraining equip-
ment for resin and foam.
Hydroseeder for seed and
ferti1i zer.
Injected into slurry at
the nozzle of a hydro-
seeder
The Delta Company
Charleston, West Virginia
Asphalt Institute
Asphalt Institute Building
University of Maryland
College Park, Maryland 20740
The Dow Chemical Company
Midland, Michigan 48640
Phillips Petroleum Company
Chemical Department
Commercial Development Divison
Bartlesvi11e, Oklahoma 74003
Grass Growers, Inc.
P.O. Box 584
Plainfield, New Jersey
07061
U.F. Chemical Company
37-20 58th Street
Woodside, New York 11377
3M Company
Adheslves, Coatings and
Sealers Division
3M Center
Saint Paul, Minnesota 55101
-------
velopment. Mulches can also be used to temporarily protect
against excessive soil loss prior-to the preparation of a
seedbed, in place of short-term vegetative stabilization.
Some mulch material, in particular straw and hay, must be
anchored to prevent them from being uncovered by wind and
water. This is usually accomplished by binding the mulch
material together and to the soil surface with asphalt or
chemical tacks. Straw may also be anchored by crimping,
as shown in Figure 13. Because of the severe winds en-
countered in the study area, crimping should be the pre-
ferred method of securing straw and hay mulch. In addition
to securely anchoring mulch, crimping, when performed along
the ground contour, produces a surface texture that inhibits
surface runoff (thus increasing infiltration), promotes
plant growth, inhibits wind erosion, and traps wind and water
transported sediment.
Figure 13. Straw Mulch Being Anchored
With a Mulch Crimper
Chemical stabilizers generally work best on dry, highly
permeable soil subject to sheet flow rather than concen-
trated flow. It is recommended that chemical soil stabi-
lizers be tested on small, representative plots of ground
before selecting a mixture of chemicals and water, and an
application rate, or before deciding to use these chemicals
extensively as a soil stabilizer. As a general rule,
chemical stabilizers do not provide protection for as long
a period of time as straw, hay, and other organic mulches.
56
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Long-term, nonvegetative soil stabilization is required when
vegetation alone cannot withstand the erosional stresses
imposed by surface runoff, and in situations where vege-
tation is not adaptable to soil or traffic conditions oc-
curring at the site to be stabilized. Mulches of nonbio-
degradable material, such as fiberglass, and various plas-
tics have been used for that purpose. These mulches protect
seedbeds during the critical germination and early plant
development periods, and act as a reinforcement following
establishment of the vegetative cover. These materials
include nettings and loose, fibrous products that, when
applied to the seedbed, become securely enmeshed in the
vegetation at the ground surface and in the root mat. Light
applications of crushed stone or gravel will perform a
similar function.
Areas Subject to Concentrated Flow--
Areas subject to concentrated flow include streams,
waterways, ditches, and drainage inlets and outfalls. As
with areas subject to sheet flow, soil stabilization is
achieved with both vegetative and nonvegetative measures.
Vegetative Stabilization — Channels which carry water
for only short periods of time after a rainfall can often be
stabilized by planting a cover of grass over the entire
waterway. This method is not practiced when the proposed
planting area remains excessively wet for long periods of
time, or when the velocity of the flow will be great enough
to remove the vegetation. If these conditions occur, other
stabilization methods must be used.
Even when the bed of the channel cannot be vegetated,
the banks and floodplain area can often be stabilized by
seeding, sodding, or sprigging with various plant materials.
To determine what types of grasses are most suitable for a
given site condition, the local soil and water conservation
district, county agricultural agent, or university extension
service should be consulted.
Seeding with grasses is generally done in waterways
which carry water only during and immediately after runoff.
Jute netting (Figure 14), straw or hay mulch anchored with a
netting, or other materials are used to both protect the
soil until a good ground cover is established, and enhances
plant growth.
57
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Sodding is generally used in waterways when the design
flow velocity is between 4 and 7 feet per second (1.22 and
2.13 meters per second) or when seasonal considerations rule
out the use of seeding. The velocity requirements indicated
above are only for erosion resistant soils. If the soil is
erodible at these velocities, structural measures will be
required in conjunction with the seeding or sodding. Vege-
tated waterways should be constructed with gently graded
sides that slope smoothly into a wide bottom. With this
type of construction, the channel can be easily vegetated,
the waterway blends into the surrounding area, and, in resi-
dential areas, the grass can be mowed and maintained without
any unusual problems. In addition to their aesthetic
value, grassed waterways slow the flow of runoff and enhance
the infiltration ability of the soil.
Nonvegetative (structural) stabi1ization--When vegeta-
tion alone cannot withstand the erosive stresses in areas
subject to concentrated flows, various structural measures
are also required. Critical areas often requiring structural
reinforcement include stream beds (illustrated in Figure
15), channel restrictions, junctions of waterways, channels
with steep gradients, and storm drain outfalls. Protection
of such areas with structures is referred to as channel
stabilization. Channel stabilization structures are used to
maintain channel alignment (i.e., prevent erosion of the
sides of the channel) and/or maintain channel gradient
(i.e., prevent scour of the channel bottom).
Revetments and check dams are the structures most
commonly used to prevent channel erosion. Revetments are
designed to shield the channel from the hydraulic and abra-
sive action of concentrated flow. Generally, these struc-
tures are built of stone riprap and placed in the bottom of
the channel, at critical locations, to prevent down-cutting.
Where the sides of the channel cannot be stabilized with
vegetation alone, the stone is carried up the sides of the
channel to form a complete channel lining. The stone riprap
should be granite, limestone, or other durable rock, and of
a size that cannot be removed by the runoff. Large voids
between rock fragments should be clinked with smaller frag-
ments to provide a dense cover. When heavy or sustained
flows must be handled, a graded sand and stone filter, or
filter cloth, should be placed under the structure, securely
against the soil surface to prevent the upward movement of
soil particles due to hydraulic action. Wire baskets filled
with stone (gabions, Figure 16), various concrete blocks,
58
-------
Figure 14.
Jute Netting Being
in a Drainageway
Insta11ed
Figure 15. Stone Riprap Placed at Bend in Stream
59
-------
bags, filled with a mixture of sand and cement, and nylon
mattresses filled with a sand/cement grout (Fabriform ®)
are also used to construct revetments in waterways. These
products and material are generally only used to stabilize
highly critical areas, such as natural streams, or stream
reali gnments.
For environmental and aesthetic reasons, and in order
to minimize maintenance requirements, vegetation should be
used with structures whenever possible. Where sustained,
heavy flow is not present, revetments constructed of loose
st,one riprap, or a stone gabion blanket provide an environ-
ment for the growth of vegetation within the armored portion
of the channel. Revetments required to protect critical
areas in stream channels and occasionally subjected to heavy
flow should be designed by an engineer and installed in
accordance with construction specifications.
Unlike revetments which can be used to protect any
portion of a channel, grade control structures, or check
dams, are designed to only protect the base, or bottom, of
the channel from erosion. These structures are placed
across the channel at intervals along the alignment to
physically inhibit the moving water from eroding the bottom
of the channel. They generally consist of a relatively
narrow strip of stone riprap laid across the channel. Logs
and lumber can be used to construct temporary check dams.
In addition to inhibiting channel scour, check dams also
serve to control runoff by slowing the movement of water in
the channel.
Runoff Control Practices
Whereas soil stabilization practices are designed to
reduce soil erosion, runoff control practices have a dual
purpose: to reduce erosion and trap sediment. Water
moving across an exposed soil surface has the ability to
detach soil particles and to transport those particles and
other particles detached by rainsplash and wind. Reduction
of the amount of soil detached by runoff and the quantity of
detached soil (sediment) leaving the construction site is
accomplished in three fundamental ways:
1. Reduction of runoff volume and velocity,
2. Interception and diversion of runoff,
3. Detention of runoff.
60
-------
Figure 16. Grade Control/Energy Dissipation Structure
Made of Gabions (Stone-filled Wire Baskets)
Figure 17. Grade Control Structure Consisting of Grouted
Riprap and Placed at Storm Drain Outfall
61
-------
Reduction of Runoff Volume and Velocity--
A reduction in both the amount of runoff and its speed
of movement can be accomplished by staging the construction
operations to reduce the time and area of exposure; by
manipulation of the slope length and gradient to reduce the
velocity of flow and rate of runoff; and, by manipulation of
the surface soil to detain the water and to increase the
infiltration rate.
Staging of operations--Proper scheduling of the various
phases of construction operations (clearing, grubbing,
scalping, grading, etc.) can minimize both the exposed
surface area and the duration of exposure. The number and
severity of erosion problems can be reduced by using a
construction schedule which allows for clearing, grading,
and the reestablishment of vegetative cover on one area
before clearing and grading begins on another. The amount
of surface runoff that flows across an exposed critical area
can also be reduced by scheduling the construction so that a
vegetated area is used as a buffer above and below the
critical area (Figure 18). These buffer zones will slow and
filter the runoff coming from the disturbed areas and thus
reduce runoff as well as trap some sediment.
Figure 18. Vegetated Buffer Area Below Graded
Highway Slope Collecting Sediment
62
-------
Manipulation of soil surfaces—The soil surface can be
manipulated to reduce and detain runoff. Manipulation
includes roughening and loosening the soil, mulching,
revegetation, topsoiling, and using soil amendments.
A properly roughened and loosened soil surface will
enhance water infiltration, slow the movement of surface
runoff, and benefit plant growth. Common methods of loos-
ening and/or roughening a soil surface include scarifica-
tion, tracking, and contour benching or furrowing. Scari-
fication is usually accomplished by discing or harrowing
along the ground contour, but can also be performed by a
crawler tractor equipped with grosser bars, or by dragging
the teeth on the bucket of a front-end loader over the
ground.
Tracking, shown in Figure 19 is performed on steep
slopes where equipment cannot be safely moved along the
ground contour. It is accomplished by running a cleated
crawler tractor up and down the slope. The cleats leave
shallow grooves which run parallel to the contour.
Contour terracing (benching) and contour furrowing are
performed in conjunction with other roughening techniques on
long slopes to disrupt and slow surface runoff. Terracing
is done with a bulldozer and furrowing (Figure 20) is accomp-
lished by plowing. In both cases, the resulting bench or
furrow must run along the contour of the ground, otherwise
the intercepted runoff will become concentrated in lower
areas, resulting in damaging gully erosion.
The contour chiseling and gouging practices employed on
mine sites in the study area could also be utilized on some
construction areas where difficult stabilization conditions
exi st.
The prompt establishment of a cover of vegetation, or
the placement of a fibrous, organic mulch on a denuded soil
surface, will also reduce and detain surface flow. Addi-
tionally, it will stabilize the soil. Vegetation or mulch
roughens the surface, prevents the soil surface from being
compacted and sealed during a rainfall, and, in the case of
live vegetation, increases the moisture holding capacity of
the soil.
63
-------
Figure 19. Properly "Tracked" Slope
Figure 20. Vegetated Fill Slope With Contour Furrows
64
-------
The permeability of the surface soil itself will also
have a major bearing on the rate of surface runoff. If the
soil remaining after grading is highly impermeable, it may
be desirable to top-dress the graded area with a more
suitable soil. This is referred to as "topsoi1ing".
T o p s o11i n g is performed to enhance revegetation ef-
forts. Decreased surface runoff is a secondary benefit. An
alternative to topsoiling is to work material, such as lime
or organic matter, into an in-place soil to loosen particle
bonds and thus increase infiltration. This is a form of
soil conditioning. As noted earlier in this section, top-
soiling with suitable soil material is particularly bene-
ficial where fine textured soils having high sodium absorp-
tion ratios are found. This is often the case in the study
area.
Manipulation of slope length and gradient--The rate of
runoff and therefore the rate of soil erosion can also be
controlled by manipulating the gradient and length of
slope. Slope design should be based on the erodibility of
the surface soil materials, as well as stability against
landslides. A reduction in relief or an overall flattening
of the topography is usually desirable from a sediment
control standpoint since shorter or flatter slopes are less
erodi ble.
The shape of a slope also has a major bearing on soil
loss and the potential for off-site damage due to sedi-
mentation. Assuming the gradient remains constant, the base
of a slope is more susceptible to erosion than the top.
This is because the runoff becomes more concentrated at the
base. Constructing a convex shape slope magnifies the
problem, whereas, a concave slope reduces it. Leaving a
relatively flat area near the base of the slope not only
reduces erosion, but also traps some sediment coming from
upper portions of the slope.
Interception and Diversion--
Another key concept in controlling soil erosion is to
intercept runoff before it reaches a critical area and to
divert it to a safe disposal area. Interception and diver-
sion is accomplished through the use of various diversion
structures, including reverse benches or terraces, di tches
(Figure 21), earth dikes, and combination of these.
65
-------
Interception and diversion practices perform two
important functions at the construction site:
1. They isolate on-site critical areas (i.e.,
denuded areas, steep slopes, waterways)
from off-site runoff.
2. They control runoff velocities on steep
or long slopes and newly graded roads.
By placing a reverse bench or ditch above the con-
struction site, off-site runoff can be intercepted and
diverted around the disturbed area or to structures that
will safely carry the runoff through the site. The use of
perimeter diversion structures is an especially important
erosion deterrent at construction sites.
Diversion structures can also be used to control
runoff generated within the disturbed area. On excessively
long or steep slopes, reverse benches are often used to
protect lower portions of the slope from erosion due to
runoff. As with perimeter structures, the internal diver-
sion structure intercepts runoff coming from higher eleva-
tions, thus preventing it from reaching the critical lower
slope, and diverts it to an off-site disposal area or a
downdrain structure.
Proper design, construction, and maintenance of diver-
sion structures is essential. They must be designed and
constructed to carry the intercepted runoff at nonerosive
veloc i ti es.
Handling and disposal of concentrated flow--The con-
struction of diversion structures and other drainageways
results in a concentration of surface runoff in or behind
the structure. This concentrated flow has a high erosion
potential and must be handled carefully. In upland areas
where concentrated flow can result in severe soil erosion,
various downdrain structures are used to conduct the water
to disposal points. Downdrain structures are stabilized
channels or pipes used to conduct concentrated runoff
safely down a slope. They can be temporary or permanent
structures. Such structures are often used to help dispose
of water collected by diversion structures. Commonly used
downdrain structures include the paved chute or f1ume, the
pipe slope drain and the sectional downdrain.
66
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A paved chute or flume, shown in Figure 22,is a chan-
nel lined with bituminous concrete, portland cement con-
crete, graded riprap, or other nonerodible material. This
structure is commonly used where concentrated flow of
surface runoff must be conveyed down a slope in order to
prevent erosion. A formal design is required to properly
size a flume for the expected water flow. Piping can be a
problem unless a good bond is maintained between the diver-
sion structure and the flume inlet.
Various pipe slope drains are also used to safely
handle concentrated flows. These drains are either con-
structed with flexible tubing (Figure 23) (flexible down-
drain) or rigid pipe. They are usually temporary structures
and are often used on highway construction sites to carry
concentrated flow down critical cut and fill slopes.
Following stabilization of the slope and construction of
more permanent drainage structures, the slope drain is
removed.
A sectional downdrain, shown in Figure 24, is another
commonly used temporary downdrain structure. It is a half-
round or third round pipe made from bituminized fiber,
galvanized steel or other material. A formal design is
needed to determine the size of the sectional downdrain
needed to carry the flow without spilling water out of the
pipe.
All downdrain structures must be stabilized at the
outlet with an energy dissipator. Energy dissipators are
used to slow down the flow of water at the drain outlet to
lessen the chance of erosion. On temporary concrete
flumes, stones or concrete blocks are sometimes set into
the concrete so they protrude up into the flume and thus
slow the water. Placing a blanket of large crushed stone
or concrete at the outlet, as illustrated in Figure 25,
will accomplish the same function.
Another effective energy dissipator is the 1 eve!
spreader. A level spreader is an outlet constructed at
zero percent grade across the slope. In this way con-
centrated runoff may be discharged at nonerosive velocities
onto areas stabilized by existing vegetation. The purpose
of the structure is to convert a concentrated flow of
runoff into nonerosive sheet flow. Construction and main-
tenance considerations usually preclude the use of this
structure for temporary control at construction sites.
67
-------
Figure 21. Diversion Ditch Protecting Lower Lying Waterway
Figure 22. Bituminous Concrete Flume
68
-------
Figure 23. Flexible Downdrain
Figure 24. Sectional, or Half-round, Downdrain Structure
69
-------
Figure 25. Stone Rip-rap Energy Dissipation
at Storm Drain Outfall
Figure 26. Permanent Concrete Grade Control Structure
(Check Dam) in a Lined Ditch
70
-------
Detention of Runoff--
Pre-sediment pond techniques--Runoff control also
involves the detention of runoff. Detention accomplishes
two control objectives: (1) slow the flow velocity and thus
reduce the ability of the moving water to detach (erode)
soil particles, and (2) detain the runoff to decrease its
ability to transport bedload material and allow suspended
sediment to settle out of the water.
Detention is achieved by obstructing the flow. Ob-
struction is accomplished by decreasing the flow gradient,
by dissipating flow energy, and by impounding the flow.
On man-made drainageways, gradient reduction and
energy dissipation can be achieved by constructing the
drainageway as long as is practicable without causing the
water to spill out of, or erode, the channel. In natural
and in man-made drainageways, the grade can also be con-
trolled by the construction of flumes or other flow barriers
across the channel. These grade control structures, illus-
trated in Figure 26, also serve to dissipate the energy of
the flow, and, thus, slow its movement. Bends in the
channel, either man-made or natural, also impede the flow.
Flow obstruction is also achieved through the use of
various filters. They include temporary gravel or crushed
stone filters used to detain and filter concentrated flow
and vegetative filters used to remove sediment from over-
land (sheet) flow.
On urban construction sites and on major highway
projects where storm drains are used, the prevention of
sediment damage to the drainage system becomes a particul-
arly important task. To provide for drainage during con-
struction, storm drains must be installed well ahead of
final grading. As a result, sediment generated on the
graded areas is given unrestricted access to the drainage
system downstream from the construction site. To prevent
some of the sediment from entering storm drains, special
filters are often installed. As an example, coarse gravel
may be piled around an inlet to form a barrier that will
both temporarily impound runoff and act as a filter. This
structure, shown in Figure 27, is commonly referred to as a
gravel inlet filter. Crushed stone is also used to con-
struct this type of filter barrier. In addition to provid-
ing a certain amount of filtering action, gravel or crushed
71
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stone is highly resistant to erosion should overtopping
occur during heavy storms. Another practice is to use such
gravel barriers at outlet points along a perimeter diver-
sion dike. These structures are called filter berms
(Figure 28). If such barriers are to perform as a filter,
periodic cleaning and replacement of filter material is
requi red.
Vegetative filter practices include the preservation
of natural woodland or grassed buffer areas, or the instal-
lation of vegetative buffers below graded areas. A natural
vegetative buffer, shown in Figure 29, is a strip of nat-
ural vegetation preserved along the downhill perimeter of a
graded area. A dense stand of vegetation slows the over-
land runoff and filters out sediment. In addition to
filtering the flow, the vegetation allows more water to be
absorbed by the soil and thus decreases the ability of the
runoff to transport sediment. The need for preserving
natural buffer areas must be recognized at the planning and
design stage of development and these areas must be prom-
inently displayed on the construction plans as off-limits
to all construction activity.
If a vegetative buffer cannot be preserved, one can be
constructed. Two important design considerations for a
constructed vegetative buffer are the width and slope of
the buffer zone, and the type and vegetation. Timely
establishment of vegetation on the buffer is a must if it
is to be fully effective. Because of its low, dense
growth and other factors, grass is the best vegetative
filter material. Thick, low-growing legumes such as var-
ious clovers are also effective filters. Even during the
dormant winter months, the mat provided by the dead foliage
still slows the flow of runoff and traps sediment before it
reaches the drainage system.
Further flow detention is accomplished through the use
of flow impoundment structures. These structures are
designed to impound sediment Taden runoff and thus, trap
some of the suspended particles. The amount of sediment
that a structure will collect or its efficiency will depend
on how long it is able to detain the flow. Impoundments
vary in size from small sandbag or straw bale temporary
sediment traps to permanent sediment basins several acres
in size. Small traps which impound water long enough to
remove coarse sediment particles are often built by placing
a row of sandbags or straw bales at regular intervals along
ditches or other intermittent waterways (Figure 30).
72
-------
Figure 27. Gravel Filter at Storm Drain
Inlet Detaining and Filtering Runoff
Figure 28. Filter Berm Placed Across a Graded
Roadway Right-of-way
73
-------
Figure 29. Grassed Filter Strip Between
Drainaqeway and Roadway Construction
Figure 30. Temporary Straw Bale Sediment
Trap Along a Roadway
74
-------
Another means of trapping sediment before it enters
the storm drainage system is to excavate a pit on the
upstream side of the storm drain inlet (Figure 31). As in
the case of all of the other traps, its function is to
temporarily detain the runoff and thereby allow some of the
sediment to settle out. The capacity of these excavated
traps is sometimes increased by placing sandbags or straw
bales around the perimeter of the trap.
Because of the very high percentage of fine grained
materials (clay, silt and fine sand) found in most of the
soils occurring in the study area, use of small traps will
probably be of marginal value. Use of filter devices
(straw bales, gravel dikes, or filter cloth) in conjunction
with such structures would increase trapping efficiency,
however.
Sediment basins--At large construction sites, sediment
basins are the most effective structures for trapping
sediment. Sediment basins are formed by constructing an
earthen dam across a drainageway, thus causing the runoff
to pond during storms or by excavating a depression in the
channel. Sediment ponds are considered the "best line of
defense" against soil loss from a construction site. They
are usually positioned at drainage outlet points on the
perimeter of the construction site. Along with prompt
stabilization of exposed soils and proper control of runoff
within the construction area, the use of properly designed,
constructed, and maintained sediment basins is one of the
more important means of controlling sediment. This is
particularly true in the study area where climatic condi-
tions impede vegetation and where the soils contain high
concentrations of highly erodable clay, silt, and fine
sand.
There are two basic types of sediment basins-- the dry
basin and the wet basin. Dry sediment basins (Figure 32)
are designed to temporarily impound runoff during rain-
falls. They are constructed on drainageways that only flow
during storms, or are placed where diversion structures
will channel stormwater into them. Often, it also becomes
necessary to dam permanent streams in order to trap sedi-
ment. When this is necessary, a wet sediment basin, or
pond is constructed. Because of the longer detention time
provided, wet basins are usually more effective than dry
basins in trapping fine textured sediment particles. Be-
cause of the high concentrations of such materials expected
in runoff from construction sites in the study area, the
75
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Figure 31.
a t
Sediment Accumulated
a Highway Storm Drain
in a Dry Trap
Inlet
Figure 32. Dry
Large
Sediment Basin at Perimeter of a
Residential Development
76
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use of wet basins should be encouraged. A source of water
for dust control and limited irrigation is an added
benefi t.
Within a detention pond, the removal of sediment from
runoff water is accomplished through settling of the parti-
cles to the bottom of the pond. For the settling of dis-
crete particles in a suspension of low solids concentration,
termed free or ideal settling, three flow regimes have been
identified according to classical settling theory. The
governing equation for the settling velocity within each
flow regime is [1]:
Stokes1 Law:
V = r_2_ (S -1)D£
S 18V
T rans i ti ona1 Reg ion:
V. = 2.32(Ss -1)D]* 6v_0-6
Re
-------
Newton's Law
Transition Region
Stokes1 Law
-------
normally measured during the course of the preliminary
design or site investigations. The factors which must be
known or assumed before an analysis can be made are:
• Design outflow rate (design storm flow)
• Expected suspended solids concentration in
the inflow
t Specific gravity and anticipated grain size of
the incoming solids
• Anticipated pond water temperature.
In the design of sediment ponds to provide for the
deposition of sediments, the ratio of the pond outflow
to the surface area of the pond, Qo/A, is termed the over-
flow velocity, Vo. therefore:
Mo = Qo/A
Based on the above relationship, it can be shown that
if the critical settling velocity of any size sediment parti-
cle is greater than the overflow velocity, that particle
and all larger than it will settle out. Increasing the
area of the pond, therefore, would decrease the overflow
velocity. This means that the critical settling velocity
for the largest size particle to be settled would also
decrease. Thus, at a given overflow velocity, increasing
the pond surface area would effect the settling of smaller
particles within the pond.
There is a limit of practicality, however, on how large
a pond surface area can be provided in order to induce the
settlement of sediment particles. As can be seen from Table
6, the pond area required to settle sediment particles
increases rapidly as the particle size to be settled de-
creases .
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Table 6. MINIMUM SEDIMENT POND AREA REQUIREMENTS
FOR SELECTED PARTICLES FOR A .0283 m3/sec.
(1 cfs) OUTFLOW [4]
Particle Diameter
(mi crons)
60 (fine sand)
40 (fine sand)
10 (silt)
1 (coarse clay)
0.1 (fine c1 ay)
m
Minimum Area Required
.2
7.43
13. 5
189
18,900
1,890,000
ft'
80
145
2030 (0.046 acres)
203,000 (4.6 acres)
20,300,000 (466 acres)
In any sediment pond, it is unlikely that purely ideal
settling conditions will be met. Factors which disturb
these conditions and thus alter the pond area required (as
calculated using ideal settling theory) include:
• Shape of the suspended particles
§ Water turbulence
• Bottom scouring of deposited sediment
• Short circuiting, i.e., when the runoff water
travels through the pond in less time than the
calculated detention period
• Nonuniform deposition of materials
• Entrance and exit effects
• Specific gravity and velocity of the inflow
In most cases, the effects of the above factors would
be to increase the required pond surface area over that cal-
culated by ideal settling theory. Therefore, these signi-
ficant factors affecting particle settling should be con-
sidered in the design of the sediment pond.
The ideal settling equations presented previously were
derived assuming a spherical particle and, for each of the
three flow regions, the drag coefficient for a sphere be-
comes an approximate unique function of the Reynolds num-
ber. However, suspended sediment particles in water are
hardly ever spherical. Drag coefficients for spheres,
cylinders, and disks differ significantly at high Reynolds
80
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numbers ( 1000). At low Reynolds numbers ( 10), the settl-
ing velocities of rod-like and disk-like particles are, res-
pectively, 78 percent and 73 percent of the velocity of an
equal-volume spherical particle [5].
The horizontal velocity through a sediment pond also
affects the particles which have settling velocities roughly
equivalent to the overflow velocity. This is called the
turbulence effect, even though it occurs with flows at low
Reynolds numbers in the laminar flow range.
The net result of turbulence is to prohibit the settling
of certain particle sizes, which are carried out with the
overflow instead of settling. An expression which can be
used to compute the removal ratio of any size particle with
turbulence present has been developed [6]. This removal
ratio is defined as the fraction of particles of a given
size that would be settled in a detention pond with turbul-
ence present. Thus, a removal ratio of 1.0 would mean that
all particles larger than or equal to the given size would
be settled even with turbulence present. This removal ratio
is a function of the flow velocity per unit of surface area
in the settling zone.
Scour velocity is defined as the horizontal channel
velocity required to start in motion particles of size D,
and is given by the equation [6]:
*c = ^ 9 (Ss " 1) D
where:
vc = scour velocity, cm/sec
B = "stickiness" factor, 0.04 for unigranular sand
and 0.06 for cohesive, interlocking material
F = Darcy-Weisbach friction factor, usually 0.02
to 0.03, depending on the surface over which flow
is taking place
The other parameters are as previously defined in the
ideal settling equations. In sediment detent ion ponds, the
horizontal velocity through the pond should be kept less
than the scour velocity so that settled small particles are
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not scoured from the bottom of the pond. The theoretical
scour velocity is seen to be independent of the dimensions
of the pond.
The effects of short circuiting are emphasized by mix-
ing of the materials within the pond, high inlet velocities,
and density currents. Experiments have been performed on
settling tanks of various shapes to determine the influence
which the tank shape has on the settling of particles.
Table 7 presents the results of these experiments [6]. A
higher short circuiting factor in Table 7 indicates that
short circuiting is more of a problem.
Table 7. SHORT CIRCUITING FOR SETTLING TANKS
Short-C ircui ti ng
Type of Tank Factor (F^c)
Ideal dispersion tank
Radial-flow circular 1.2
Wide rectangular (1ength=2.4xwidth) 1.08
Narrow rectangular (1ength=l7xwidth) 1.11
Baffled mixing chamber (1ength=528xwidth) 1.01
Idea1 bas i n 1.0
o
The surface area (A, in m ) of a pond can be increased to
approximately account for short circuiting as follows:
A ¦ (F« 0
where:
Q = flow, m3/sec
Vg = critical settling velocity, m/sec
MAINTENANCE OF CONTROL PRACTICES
Just as heavy equipment requires regular maintenance
to avoid costly repairs, erosion and sediment control prac-
tices will not function properly throughout their designed
life if they are not maintained. Whether the practice is
vegetative or structural, maintenance must be performed if
the practice is to continue to provide protection against
sediment pollution.
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Vegetative Maintenance
There are two basic types of vegetative maintenance:
follow-up maintenance and periodic maintenance. Follow-up
maintenance is required when seeding, sodding, or other
vegetative practices do not initially achieve the desired
degree of stabilization. This maintenance should be per-
formed during the same growing season. Materials planted in
the spring should be inspected during the summer or early
fall, whereas areas stabilized in the fall should be in-
spected in early spring so that necessary corrective prac-
tices can be performed during the spring planting season.
Periodic maintenance is performed after vegetation
has been successfully established. This is the maintenance
that is required to achieve long-lasting protection against
soil erosion. It involves periodic inspection of the
vegetated area to assess its success in controlling ero-
sion. Activities involved in this type of maintenance
include:
• periodic applications of fertilizers and
soil conditioners
e insect control
• reseeding of areas damaged by traffic, etc.
• mowing
Structural Maintenance
To provide reliable control, all runoff control struc-
tures require adequate and timely maintenance. These
structures must be inspected after every major storm to be
sure that no breaches have occurred. Sediment build-
up in diversion structures, such as dikes and ditches,
should also be checked. Outlet areas also require frequent
inspection to insure that no erosion is occurring. Eros ion
damages require prompt repair to prevent further soil loss
and to protect other areas on the site. Corrective mea-
sures should also be taken to protect against similar
damage in the future.
Timely cleanout and proper disposal of trapped sediment
from sediment retention structures is also an important
maintenance requirement. As a ru1e-of-thumb,a sediment
basin should be cleaned out when it has lost 50 percent of
its storage capacity due to sediment deposition. Filling
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beyond this point reduces the capacity of the basin to
retain runoff long enough for sediment to be deposited.
Similar practices should be followed for sediment traps,
filters, check dams, and other structures.
Sediment removed from structures must be disposed of
properly. Indiscriminate piling or dumping is unacceptable
because the sediment is likely to be moved back into water-
ways or storm drainage systems by successive storm
events. Deposition behind a protective berm or filter
strip will often suffice if the quantities involved are
not large. In basins with large capacities, the services
of professionals experienced in the handling and disposi-
tion of sediment should be retained.
CONTROL STRATEGY
Formulation of a control strategy, or control plan, is
an essential first step in sediment control. A clear
understanding of the basic control principles presented
earlier in this chapter, as well as thorough familiarity
with the numerous control techniques, are basic requisites
for the planner. The procedure to be followed in the
preparation of the control strategy includes:
• gathering of information on topography, soils,
drainage, vegetation, and other predominant
site features
• identification of dominant characteristics of the
development type
• evaluation of the information in order to anti-
cipate erosion and sedimentation problems
• development of an earth change plan which
minimizes the amount of erosion created by
development
• development of an erosion control plan which
specifies effective sedimentation control
measures.
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Site Inventory and Interpretation
A site inventory investigation is usually performed to
determine the engineering feasiblity of the project. The
investigation should be tailored such that, as a minimum
the following information is obtained:
• Site's proximity to lakes, streams, and
other surface waters (obtained from site
location map).
• Identification of existing vegetation,
predominant land features, and a description
of existing site drainage patterns and facil-
ities (obtained by topographic map).
• Identification of soil conditions for
the site areas which will be exposed
during development (obtained by soil
survey reports or site visit by soil
scientist).
Many landscape features are especially vulnerable to
damage during developmental activities. Such features or
locations are often referred to as "critical areas."
During site planning it is usually prudent to protect
highly critical areas from any disturbance. Such areas
include floodplains, waterways, steep slopes, and highly
erosive soils.
Preparation of Control Plan
One of the objectives of the site planning process
should be to prepare a comprehensive sediment control plan.
As a minimum the plan should be designed to perform the
following functions:
• Identify and protect critical features.
• Stabilize disturbed soil materials.
t Reduce runoff and erosion on the site through
the use of operational, structural, and vege-
tative measures.
0 Trap sediment on and at the perimeter of
the construction site.
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• Require adequate inspection and maintenance
procedures.
The complexity of the plan will be influenced by the
size of the project, the intensity of the proposed develop-
ment, and the land use type. In addition to the functions
described above, the following factors should be given
consideration and included in the plan.
Clearing and Grading Schedule--
The exposed surface area and the duration of exposure
can both be kept to a minimum through proper scheduling of
the various phases of the construction operations. This
can be accomplished by developing the site in stages and by
requiring the performance of all clearing, grading, and
stabilization operations in a specified area before moving
on to another area. The area covered by each stage or
phase should be identified on a site plan. The sequence
and scheduling in which development should occur must be
clearly described on the plan.
It is usually desirable to stage the operation on a
watershed or subwatershed basis. The size of the area
involved should be determined on the basis of the construc-
tion capability of the contractor and the amount of criti-
cal area, such as steep slopes and areas of high soil
erodibility, found within the watershed.
A factor which must be considered when scheduling
areas to be developed is the relationship of vegetative
stabilization to climatic factors. In areas having severe
exposure problems or exhibiting severe erosional problems,
it is desirable to schedule the development so that it
begins in a period of low precipitation and is completed
near the beginning of a period favorable to the establish-
ment of vegetation.
Timing and Location of Control Measures--
The same site plans which delineate the sequence of
development must also show the location of all sediment
control structures. The plan must also indicate the se-
quence of the construction of these structures. Timing is
one of the most critical factors in the effective control
of sediment on construction sites.
86
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Perimeter defenses such as diversions and sediment
traps or basins, whether temporary or permanent, should be
installed before construction of the rest of the site
begins. Immediately after grading is completed, internal
defenses such as the establishment of permanent vegetative
cover or other stabilization measures, should be imple-
mented.
Traffic Control--
Areas, such as vegetative buffer strips along water-
ways, and all undisturbed open spaces, should be delineated
on a site map and designated as "off limit" areas for all
vehicular traffic. The specifications must state that all
vehicular traffic will stay within the roadway, access
corridor, or utility rights-of-way. These rights-of-way
must also be shown on the site plan. The specification
must also restrict all traffic from crossing streams or
drainageways except at approved stabilized crossing loca-
tions.
Stream Erosion--
A11 critical areas along streams must be marked on the
site plan and the recommended method of stabilization
i ndicated.
Stream stabilization work should be scheduled for
periods of low precipitation during the growing season and
should be performed prior to the initiation of clearing and
grading operations in the watershed.
Planting Schedule--
The sediment control plan must clearly define vegeta-
tive practices, both temporary and permanent. The plan
must state and show where and when sod, temporary seeding,
and permanent seeding are to be used. Specifications
should also be provided regarding ground preparation, sod
quality, seed type and quality, fertilization, and mulch-
i ng.
Grading Delays--
The construction specifications should also clearly
define the maximum length of time that a graded area can be
left uncovered after completion of grading or after grading
shut downs, such as commonly occur in some areas during the
winter months.
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Planning Assistance
The on-site evaluation of the potential construction
site should be performed by persons knowledgeable of such
disciplines as agriculture, civil engineering, and geology.
Effective sediment control plans are built upon nume-
rous sources of information relative to the construction
site. County soil and water conservation districts are
valuable sources of information on soil properties, drain-
age characteristics, climate, and plant materials. Some
soil survey reports furnished by the Soil Conservation
Service (SCS) provide information on the suitability of
various soils for various types of construction.
Information on the location of critical mineral depos-
its, aquifers, groundwater recharge areas, and rock out-
crops can be obtained from the U.S. Geological Survey
offi ces.
The principal source of water runoff data is the
"Water Supply Papers" of the U.S. Geological Survey. These
papers contain records of daily flow, mean flow, yearly
flow volume, and extremes of flow. This information is
needed to properly design hydraulic structures on construc-
tion sites.
Highway offices at the county and state levels can
furnish information on soil engineering properties, and
areas having stormwater drainage or flooding problems.
Control Strategies for Specific Developments
Each construction project will present some unique
control problems. However, the control principles and
practices discussed in this section of the manual apply to
all categories of construction - urban developments, trans-
portation and transmission systems, and commercial projects.
The major differences in control strategies is in the
degree to which various principles and practices are ap-
plied. For example, the use of perimeter sediment basins
are more important on large urban developments were large
fairly concentrated, and long-term disturbance is expected,
than on transmission line construction sites were the
disturbance is less concentrated and occurs for a shorter
period of time. In the latter case, the use of numerous
small traps on drainageways and various filters (used
mostly to intercept sheet flow) may constitute a major
portion of the control strategy.
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It is a common practice on urban developments, such as
housing or shopping center projects, to mass grade the
entire site; then construct the road and storm drain systems;
next, install the utility lines; and finally, build the
homes or other buildings. When this type of development
occurs, a considerable amount of surface area is left ex-
posed to erosive forces for a long period of time. Under
these conditions three areas of environmental protection
are most important. First, to temporarily stabilize all
exposed soil surface as soon as possible. Secondly, to
keep as much sediment as possible out of storm drains through
the use of structural vegetative stabilization practices,
storm drain inlet filters, and waterway check dams and
sediment traps. Finally, perimeter defenses, such as diver-
sion dikes and ditches should be present around the bound-
aries of the work area, and sediment basins should be con-
structed to receive all runoff water leaving the site.
Consideration must also be given to the long-term
stability of the receiving channel. The construction of
impervious surfaces will result in substantial increase in
surface runoff from the construction site both during and
after the project is completed. Unless some measures are
taken to increase the safe carrying capacity of the water-
way or the increases in surface runoff are mitigated by
on-site measures, degradation of the receiving channel is
sure to occur.
Power transmission line, roadway, railroad, gas and
oil pipeline, and other transport system construction opera-
tions are linear in nature and, as such, often do not
impact any one affected watershed to the extent that a large
urban construction operation does. Exception to this
general rule does occur, however, particularly when Interstate
or other major highways are constructed, when major streams
crossings are made, or when construction occurs along
drainageways. Where construction activities parallel a
stream or other body of water vegetative filters should be
preserved or established to protect the waterways. When
trenches are dug, the spoil material should be placed up-
slope of the trench to prevent its introduction into the
stream.
When underground utilities are installed, clearing
and trenching operations should be staged to minimize the
area exposed at any one time. A short section should be
graded or excavated, the transmission or transport systems
installed, and then another short section prepared. As soon
as all construction work is completed the disturbed area
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should be stabilized with vegetation arid/or other materials.
Above ground facilities should also be constructed in a
similarly staged fashion. Planning plays an important
role in achieving adequate sediment control at transmission
and transportation rights-of-way.
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REFERENCES
1. Weber, W.J., Jr., Physiochemical Processes for Water
Quality Control, Wiley-Interscience, New York, 1972.
2. Jensen, I.B. and Hodder, R.L., Custom Designed Surface
Manipulation and Seeding Equipment for Erosion Control
and Vegetation Establishment. Natl. Coal Assoc./
Bitum. Coal Res., Inc., Sixth Symp. Coal Mine Drainage
Res., Louisville, Ky., 1976.
3. U.S. Environmental Protection Agency, Methods to Control
Fine-Grained Sediments Resulting from Construction
Activi ty, EPA-440/9-7, December, 1 976, 74 pp.
4. Poertner, Herbert G., Practices in Detention of Urban
Stormwater Runoff, American Public Works Association,
Special Report No. 43, June 1974, 231 pp.
5. Fair, G.M., J.C. Geyer, and D.A. Okun, Water and
Wastewater Engineering, John Wiley & Sons, New York,
N.Y. , 1971.
6. Camp, T.R., "Sedimentation and the Design of Settling
Tanks," Transactions of the American Society of Civil
Eng i neers, Vol. Ill, 1 946, pp. 895-958.
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SECTION 4
INSTITUTIONAL APPROACHES TO PREVENTION AND CONTROL
THE INSTITUTIONAL SETTING
The control of urban nonpoint sources of pollution
is no longer an option but a requirement. The Federal
Water Pollution Control Act Amendments of 1972 require
control of nonpoint source pollution. Under Section 208
of the act, water quality management plans must be prepared
by 1978 and plan implementation must be carried out to meet
water quality goals by 1983. The following points summa-
rize the effects of Section 208 on institutional approaches
to be considered in this section:
« Nonpoint source control is a requirement
instead of an option.
o There is a time deadline for planning and
compii a nee.
o The task must be undertaken either by desig-
nated 208 planning agencies or by the state--
therefore even the most remote locations will
be included.
e Urban sources such as construction and storm-
water runoff cannot be viewed in a vacuum, but
must be considered in a comprehensive framework
along with other point source and nonpoint
source problems.
Nonpoint source management is properly a 3-step
process: (1) research, (2) public education, and (3)
regulation. The principal drawback of the 208 program
is that step 3 must be planned by 1978 and implemented
by 1983. In some cases, this simply does not leave enough
time for steps 1 and 2.
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The feasibility of the 1983 deadline is at issue
nationally. The planner in the western states is a
special exception to this 1983 dilemma. Energy develop-
ment in the west has the potential to generate many new
urban sources before 1983. In some places, the energy
boom may have subsided or levelled-off by 1983 and the
damage from uncontrolled urban runoff may already be done.
Thus, because the energy boom is about to happen, the
western planner has an immediate need to regulate urban
nonpoint sources and cannot wait for research, public
education, or 1983.
The following points summarize the effects of the
energy development boom on the circumstances of the western
pianner.
e In many places, energy development will intro-
duce urban development where no such land use
presently exists. This means that the problems
of urban runoff and the means to deal with them
will be unknown. What's more, the extent of
these problems cannot be measured until they
arrive.
• Energy development is happening now and will
continue to happen in the near future, limiting
the time available for planning and institu-
tional mobilization. Further, the rate of energy
development in an area may be very intensive --
requiring that a regulatory mechanism be in
readiness upon its arrival.
• Energy development promises to be a development
boom unrivaled in the history of the region.
In this respect, it will carry with it a number
of major social issues. Consequently, the
control of urban-source nonpoint pollution
will have to compete with other problems for
institutional resources that will be limited
if not over-taxed.
It is reasonably certain that energy-affected
planning areas will be faced with the need to regulate
urban nonpoint sources before they are fully equipped and
prepared. This is true to some extent everywhere across
the nation. To the extent that regulation is premature,
regulators will have to work backwards to correct opera-
tional flaws. Another way of saying the same thing is
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that a maximum of flexibility must be built into regula-
tory programs. Joseph N. Crowley, [2] arrives at the
same conclusion in a paper for the National Association
Regional Councils and goes on to define the concept.
"Flexibility s it is true, is a term that may
cover (without absolving) a multitude of sins.
However, the term may also properly countenance
a diversity of analytical perspectives} planning
alternatives, implementation strategies, and
even ultimate results."
Flexibility is the key. As Crowley points out, there
is no specific prescription for 208 planners embodied in
the term. Indeed, it is the generality implied by the
word that makes it an accurate descriptor of the desired
regulatory system.
The concept of this section of the manual is to pre-
sent a broad collection of regulatory building blocks,
thus providing planners with a large number of possible
combinations in the belief that this will best service
the need and the appetite for flexibility. Before looking
at the individual pieces, however, it is necessary to
have some understanding of how they go together to make
a total regulatory program. Figure 34 represents the
synthesis of the parts. The eight components from the
diagram will be defined here, before proceeding further.
(1) monitoring -- hydrologic and water quality
measurements taken as part of research or
enforcement efforts to document the extent
of the problem.
(2) control technology -- on-site control practices
which can be implemented to control runoff
from urban areas.
(3) regulatory devices -- the instruments of regu-
lation used to assure the use of on-site con-
trol techniques. Such instruments include
permits, licenses, building codes, land use
controls, performance standards, taxation, etc.
(4) institutional arrangements -- the designation
of government agency responsibilities in carrying
out a regulatory program results in an "institu-
tional arrangement" which assures the effective
administration of the "regulatory devices."
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IN5TITUTI08AL
ARRANGEMENTS!
RB&ULATORyf
DEVICES
CONTROL
TECHN0LD6Y|
&
SOtfOtf
IMPlEMENTfllON
STRATEGIES
o
Figure 34. Regulatory Building Blocks
(5) legal authority -- there must be a legal
foundation for the regulatory agency to imple-
ment programs utilizing the various "regulatory
devices." Each type of device requires a
different legal sanction. In addition, there
are other legal requirements pertaining to
intergovernmental cooperation and funding.
(6) funding -- funding is required for all the
phases of a regulatory program including:
research, planning, public education, enforce-
ment, etc.
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(7) public support -- the public understanding
of the problem is critical to the appropria-
tion of adequate legal authority and funding
to implement a regulatory program.
(8) implementation strategy -- a regulatory program
will not be successful simply because it is
wel1-conceived . It must be effectively exe-
cuted with attention to the use and training
of qualified personnel, periodic program review
and revision, and most of all flexibility.
This manual covers all of these eight components of
a regulatory program. Section II is concerned with the
measurement and estimation of the extent of urban non-
point source problems. Section III presents a broad
range of control techniques. This chapter covers the
other six "institutional" components of a regulatory
program.
REGULATORY DEVICES
As noted in the foregoing definitions, regulatory
devices are the instruments of a regulatory program that
are used to assure the effective application of control
techniques. Such regulatory devices include permits,
building codes, land use controls, etc. These will all
be explored in this section. However, there is another
item that comes between the control technology and
the regulatory device which should be discussed first.
This is the concept of "Best Management Practices" (BMP)
[3]. Best Management Practices are defined as follows:
"... a practice or combination of practices that is
determined by a State after examination of alternative
practices to be practicable and most effective in
preventing or reducing the amount of pollution gene-
rated by a non-point source to a level compatible
with water quality goals."
The BMP concept introduces an extra element of flexi-
bility into the design of regulatory programs. With the BMP
approach, it is possible to tailor control requirements to
site conditions and adapt strategies according to the mag-
nitude of the problem. The key words of guidance in
selecting BMP's are "practicability" and "effectiveness."
The interpretation of these terms essentially delimits the
range of flexibility available to the planner.
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Another dimension of Best Management Practices is a
dual emphasis on both "prevention" and "control." The
regulatory aspects of "control" entail the things we nor-
mally think of -- a specific control technique or group of
techniques selected for use on a site as the Best Management
Practices for that site and a permit or other regulatory
device that assures implementation. A preventive approach
to regulation tends to make these otherwise distinct com-
ponents (control techniques, BMP's, and regulatory devices)
blend into one another. For example, a land use restriction
for a critical area is at the same time a regulatory device
and a BMP. However, it is not a control technique, but a
preventive technique.
Aware of the role that Best Management Practices play,
it is suitable to proceed now with the discussion of regu-
latory devices.*
Permi ts
Permitting is probably the most common device uti-
lized to assure control of the short-term effects of con-
struction activity. The general procedures involved as are
fol1ows:
• Requirements for Submission of Control Plans -
Permit application procedures should include a
requirement for the submission by the applicant of
a detailed site control plan. This plan must
indicate the control techniques to be employed.
Provisions for the incorporation of longer-term
stormwater management features in the site plan
may also be included in permit requirements. The
control plan should be prepared by a competent
profess i onal.
• Provision for Plan Review by Appropriate
Regulatory Authorities - Reviewing agencies
should be authorized to request modification
of the plans as a condition for permit issuance.
The ensuing descriptions of regulatory devices are largely
abstracted from EPA 's Interim Guidance on Development of
208 Regulatory Programs, Water Planning Division3 1976}
Ref. 4.
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o Provisions for Monitoring and Inspection -
Monitoring by either the permit holder or
the regulatory agency and on-site inspection
by the regulatory agency should be provided
to ensure compliance with and the effectiveness
of the plans.
9 Requirements for Performance Bonds and Liability
Insurance - Bonds- and insurance are customarily
required when construction activities are exten-
sive or potential damage from runoff may be
considerable. The regulatory agency is authorized
to take immediate corrective action at the expense
of the permit holder in cases of non-compliance.
• Sanctions for Violations - Fines are commonly
provided for non-compliance with the terms of
a permit; injunctive relief and other forms of
judicial recourse may also be provided.
e Opportunities for Appeal and Review of Permit
Conditions - Construction regulation should
provide for periodic review of permits by agencies
with supervisory responsibility over the regu-
lated activities and for appeals to review boards
when permit applicants are dissatisfied with the
conditions of their regulation.
Building Codes and Subdivision Regulations
Construction runoff control and stormwater management
may be accomplished by the incorporation of appropriate
provisions in building codes and subdivision ordinances by
local governments. This approach may be followed in
tandem with a permitting procedure, in which case, the re-
quirements for site development are spelled out in the
ordinances -- simplifying the permit device. For certain
types of small-scale construction projects, detailed site
control plans may not be necessary with a wel1-prepared
ordinance. However, the building code and subdivision
regulation devices force a greater responsibility on the
staff of the regulatory agency to ensure careful monitoring
and enforcement. These procedures are a less direct and
dependable form of regulation than the rigorous permitting
approach outlined above. Particularly when ordinance re-
quirements are stated in general terms, or technical re-
quirements are vague or brief, adequate compliance may be
uncertain.
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Site-Oriented Devices
Permits, building codes, and subdivision regulations
are all regulatory devices that are oriented to achieving
control on individual sites. There are some technical
options and technical cautions which accompany their use.
First, of course, the flexibility of the Best Manage-
ment Practices concept can be applied to all of these
devices in determining what type of controls should be
required on a given site. In order to implement the BMP
flexibility, however, it is necessary to have qualified
technical staff at the regulatory agency and a provision for
case-by-case review. In fact, a case-by-case review
authority may be used as a singular regulatory device, but
this approach can be as arbitrary as it is flexible.
A key option which can be exercised with site-oriented
devices relates to the choice between regulating the appli-
cation of control techniques or the performance of them. In
most cases, control techniques are specified and there is
generally some monitoring and inspection function to assure
their effectiveness. A more flexible approach is to specify
only requirements for performance and leave the choice of
control techniques to the imagination of the developer. The
price for this extra flexibility is a qualified technical
staff to review cases and provide guidance, and an extra
emphasis on monitoring and enforcement. The most important
criteria for an effective performance standard is the ease
and accuracy with which performance can be measured.
Watershed planning is essential to the rational deter-
mination of site-specific requirements for control and
performance. Construction requirements can be differen-
tiated for areas which are more or less susceptible to
erosion. Site features related to stormwater management
must be coordinated on a watershed basis to avoid flood
damage. The constraints placed on site-specific flexi-
bility by a coordinated watershed approach are very neces-
sary. In effect, the site-oriented regulatory devices
become instruments for implementing regional plans when they
are so constrained. The watershed planning influence also
injects a "preventive" character into these otherwise
"control" oriented site-specific regulatory devices. The
next step in prevention, of course, is the regulation of
land use which is the subject of the immediately ensuing
sections. In the Western study area under consideration
here, many of these types of land use controls may not be
politically feasible.
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Planning and Zoning
As a first cut at prevention, land use planning and
zoning can be used to limit certain land uses and to protect
vulnerable areas. Clearly, the permitted use of land --
whether it be industrial, commercial, residential, or open
space -- will affect the extent of runoff. Also, population
densities assigned to land uses will determine, to some
extent, the nature of construction. The consideration of
present and future zoning in light of the physical character
of the land may lead to the adoption of some zoning proce-
dures as a component of a runoff management plan.
Zoning Amendments
Within the framework of existing land use plans it may
be possible to amend particular parts of zoning ordinances
so as to redirect the location of development within exist-
ing permissible use classifications. Planned unit develop-
ment and cluster zoning ordinances can be used to allow
flexibility to the developer and encourage better considera-
tion of environmental factors in land development.
Critical Areas
Until recently, land use control has been the primary
domain of local governments. In the last several decades,
however, state legislatures in many states have asserted
greater authority over the use of land, especially in mat-
ters of regional concern. The most common form of state
land use authority is over the regulation of critical areas.
Critical areas, such as floodplains or unique ecosystems,
are generally designated.
Public Lands
Western energy development is cause for special concern
at the borderline of federally owned land. There should be
uniformity in the nonpoint source regulatory programs on
both sides of the property-1ine. Failure to have uniform
control over development at boundaries to Federal lands will
create artificial development incentives or pressures which
may induce development of unsuitable lands in an undesirable
pattern.
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The construction of highways, roads, airports, and
other Federal and state projects on public lands or by right
of eminent domain may be brought under regulation most
effectively by state law. State laws such as those dis-
cussed later in this section provide for regulation of state
projects by a water resources or natural resources depart-
ment and establishes the state as negotiator to establish
policies with Federal agencies for use of Federal lands.
INSTITUTIONAL ARRANGEMENTS
Regulatory programs can be fashioned out of various
preventive and control techniques which are selected ac-
cording to a best management practices concept and imple-
mented by a number of different regulatory devices. At this
point, consideration must be given to the regulatory agen-
cies which shall administer the regulatory devices. For
nonpoint sources in general and for urban sources in
particular, the implementation of a regulatory program will
involve the coordinated efforts of many agencies at many
levels of government. In order to be effective, the in-
stitutional arrangements should be closely modeled after the
regulatory building blocks. That is to say the initial
criteria for selecting regulatory agencies should be their
ability to do the job. In this respect, the three most
basic criteria are as follows:
(1) Techni cal abi1i ty
(2) Legal authority
(3) Funding
There are a great number of other complicating factors
which must be considered in designing institutional ap-
proaches to nonpoint source pollution management. These
other factors are largely operational hang-ups which in one
way or another affect the integrity of the three key in-
gredients: technical ability, legal authority, and funding.
As in most of the institutional literature, such operational
problems will be the primary subject of discussion here.
The rudiments of legal authority and funding are defined in
later sections. Technical requirements are addressed in the
section on implementation strategy. The central theme of
the ensuing discourse on operations is that a candidate
regulatory agency may be perfectly suited to technical,
legal, and financial requirements and be rendered ineffec-
tive by operational constraints. An illustration will help
to identify the types of operational constraints to be dis-
cussed.
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Consider the case of two adjacent counties along whose
border a new mine is about to open on a Federal lease. The
best management practices that can be applied to control
secondary development are determined to be land use control
over critical areas and a building permit system to control
site developments. The candidate regulatory entities
include: the two county governments, a bi-county planning
commission, the state government, and the Federal Govern-
ment. The following types of operational issues arise:
• If the county departments of public works are
to implement the building permit system, and if
the political acceptability of permits differs
between the two counties, how can a consistent
level of enforcement be assured?
• Will the counties exercise land use controls
through zoning or delegate that task to the
planning commission? Is either approach poli-
tically feasible? If county politics make land
use control too weak, will the state step in
through a critical areas mandate or will the
Federal Government become involved by controlling
the rate and location of energy development?
• If one county is upstream of the other, how
are the costs and benefits of the regulatory
program to be allocated?
• Who will coordinate the total program and under
what authority? Who will do the advance planning?
How will the program be revised and adapted as
necessary?
There are no pat answers to these questions. The 208
institutional literature is full of generalized pieces of
advice and case histories of variable relevance. Some
samples are:
"Nevertheless208 does have a lot of bureau-
cratic sex appeal. The appeal lies not in the opera-
tion of a sewerage system or a stormwater utility which
might emerge as part of a 208 plan, but in the poten-
tial that many see for using 208 planning as a con-
venient vehicle for exercising real political leverage.
208 has come to represent the planner's last best hope
for controlling land use and, as such, it could be the
most powerful planning tool still remaining to local
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officials. That means it is a highly sensitive issue --
presenting lots of opportunities for forging good
interagency working relationships -- and, on the other
hand, laden with the potential for some very damaging
confrontations which could polarize relationships for
several years."
-- Richard S. Page, Executive Director [5]
Municipality of Metropolitan Seattle
"As a a point of beginning it is necessary to recognize
that management agencies... already exist. The question,
then, is what changes do we wish to make in the exist-
ing authority and not what institution do we wish to
create. As proposed control of development and change
in land use patterns pose threats to property owners
and cause people to rise up, so too do proposed changes
in organizational structure and authority pose threats
to individuals, to jobs, and to vested interests, in
government and in consulting engineer firms. Therefore
we must take care because it is people, not authority,
we are impacting. Secondly, we must take care because
those institutions are the product of a long history of
negotiation, bargaining and gradual evolution. It
requires great dexterity and tremendous support for
change if the resultant institution is to be more than
an evolution of what exists. "
"The question is asked whether minimisation of costs
and institutional change is a strategy that should be
considered and pursued. To my mind the answer is no.
Rather one should attempt to lay out the true costs and
to allocate those true costs to users. The net effect
of this will be to balance costs with an acceptable
degree of organizational change. Rather than attempting
to get by with minimization of either cost or change,
let the two be a consequence of allocating the costs to
do the job. If in the process early proposals get
scaled down, there will be less change rather than
indiscriminant bargaining."
-- Robert C. Einsweiller, AIP [tf]
Planning Consultant
Minneapolis, Minn.
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What it all comes down to is tha
tive institutional arrangements will i-
very complex negotiations. Mr. Page, c,
referred to it as "pragmatic horse trad',
enough to simply match the ability and ai
cies with the individual regulatory devict
a glue to hold all of the regulatory build,
gether. The adhesive under consideration is.
208 plan. Fitting regulatory building block,
a comprehensive plan for water quality manage,
technical challenge. But the compatibility of
la tory components, the internal consistency of
the structural integrity of the total program is
greater challenge that reaches beyond technical c
tions to the realm of political and administrative
b i 1 i ty.
It is clear that the 208 plan must be a negotiai
settlement. There is no way that so many pieces coulc
together without some give and take. Further, the efft
tiveness of the plan will be directly measurable by the
worthiness of this bargaining process. Obviously, no
complete prescription can be offered here for the executi\
of this task. Unique solutions must be hammered out for
each and every 208 planning area. But, with respect to
urban non-point sources, it is perhaps most important to be >
mindful of the types of trade-offs that might avail them-
selves within the total institutional context of 208
planning. In many cases, it may be possible to strike a
bargain between two problems where no suitable solution
could be found for them individually. In this respect,
several types of relationships between problems are perti-
nent to the western energy states, as follows:
# Relationships between one non-point problem
and another -- As speculated above, it may be
difficult to reach agreement on a problem such as
the interjurisdictional administration of a
building permit system for urban source control.
At the same time, it may be easy to get a con-
sensus on the administration of agricultural
controls by a Soil Conservation District.
Especially in the rural study area, the Soil
Conservation District may also be the most
politically acceptable agency for the opera-
tion of a building permit system for new urban
sources.
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0 Relationships between nonpoint source and
point source problems -- An upstream county may be
expected to be reluctant to bear the costs of non-
point source control. But the siting of a sewage
treatment facility in a downstream county may be
adequate enticement.
e Relationships to energy development -- It is
reasonable to speculate that, in the absence of a
recurring crisis situation, the number of state
and Federal regulatory devices affecting energy
development will continue to grow as the exploi-
tation of energy resources continues. In many
ways, western planners may have a golden oppor-
tunity to accomplish some 208 objectives by
capitalizing on this extraordinary regulatory
muscle that can be applied to the control of the
rate and location of development. For the most
part, however, these Federal and state devices are
operational only on a regional level. There is,
therefore, a "regulatory gap" at the local level.
It remains to be seen whether and to what extent
state and Federal government agencies will become
involved in "boom town" regulation on a case-by-
case basis. Another way to look at this situation
is that western planners may have a golden oppor-
tunity to control energy development at the local
level through the use of their 208 authority. In
sum, it is apparent that the 208/energy interface
is fertile ground for some creative environmental
management.
LEGAL AUTHORITY
For each type of pollution problem, a regulatory device
may be selected and an agency of government may be assigned
to the task of implementing the device. In building the
type of complex regulatory system required for urban non-
point sources or for 208 in general, two major types of
legal questions arise. These are:
o The authority of an individual agency to implement
a given regulatory device.
• Inter-governmenta1 agreements transferring regu-
latory authority from one agency to another in
support of the desired institutional arrangements.
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The bases of adequate legal authority for 208 regula-
tory programs have been identified in EPA's interim guidance
as described below.*
Home Rule Jurisdiction
Obtaining sufficient regulatory power for agencies is
usually simplified when "home rule" governments, or agencies
acting under authority delegated from them, are involved.
"Home rule," usually applying to local governments of
general jurisdiction, permits them to pass laws of local
concern without obtaining enabling legislation from the
state, since such governments obtain their powers directly
from the state constitution. In contrast, where home-rule
does not apply, local government customarily secures its
powers from the state legislature and may exercise only
those powers granted through the legislature. The scope of
powers available to local government are usually interpreted
more generously in the case of home-rule government. When
home rule is absent, the courts have generally held that
local governments have only such powers as are expressly
granted, necessarily implied, or indispensable to accom-
plishing the declared purposes of the government. If a
government without home rule has not clearly been granted
the needed regulatory authority in its charter, the courts
are likely to hold that such authority does not exist.
Thus, without home rule the authority of local government is
likely to be narrowly defined by the courts.
The home rule status of local government is important
to the 208 planning process because it is quite likely that
regulatory powers for agencies in areas without home rule
will have to be obtained through state legislative action.
In home rule jurisdictions, however, it may be possible to
create or apportion regulatory powers among local government
entities without recourse to the state legislature and with
less likelihood of court reversal.
Delegated Powers
Regulatory responsibilities may be exercised by govern-
ments of general jurisdiction, such as municipalities or
counties, or by agencies acting through powers delegated in
other state or local legislation or intergovernmental
agreements. Within a 208 area, for example, regulation over
disposal of residual waste might be achieved through a
*
The ensuing descriptions of legal authority are largely
abstracted from EPA's Interim Guidance on Development of
Regulatory Programs, Water Planning Division, 1976, Ref. 4.
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municipality using its zoning powers to regulate the loca-
tion of dump sites and a sanitary district utilizing user
fees to discourage certain types of solid waste. In cases
where regulatory functions are assigned to agencies exer-
cising delegated powers or acting through intergovernmental
agreements, it is important to assure that such agencies
have the power, within the scope of their delegated au-
thority, to regulate in the manner expected of them.
The Police Power
The police power possessed by almost all local govern-
ments of general jurisdiction is potentially a very pro-
ductive source of regulatory authority for implementing a
208 plan. Customarily, the police powers of local government
have been very broadly defined to embrace any actions neces-
sary for the preservation, comfort and general welfare of
the public. More particularly, the police power is commonly
exercised to protect or enhance public health; this objec-
tive can often be utilized as the basis for regulatory
actions included in 208 plans. There has been a general
judicial trend toward increasing the scope of the police
powers, even in the case of governments lacking home rule.
However, the state may limit the police powers in non-home
rule areas.
Using the police powers, local governments have adopted
measures to regulate the use of septic tanks, the location
and condition of dumps, and the quality of municipal water
supplies among many other measures. Many of the regulatory
programs to be included in a 208 plan involve such programs,
or measures akin to them in objective or procedure. This
is ample reason, therefore, to carefully investigate the
police powers as a very likely source of regulatory author-
i ty.
Some General Constraints Upon Regulatory Authority
Planners should be alert to several limitations on
regulatory powers which should be considered during the
assignment of regulatory functions to various agencies:
o The Limited Use of Implied Powers -- It may some-
times appear that regulatory power is "implied"
in the existing authority of an agency, or in its
delegated authority or powers derived from
intergovernmental agreements. As a rule, it is
better to obtain the necessary regulatory powers
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in some explicit form rather than depending upon
"implied" authority. Implied powers are subject
to widely divergent interpretations and limita-
tions by courts across the nation and, hence, may
be open to considerable challenge and protracted
litigation. Much of this may be prevented through
the creation of a clear, explicit grant of author-
ity to the agencies involved.
The Test of Reasonableness. Any regulatory
actions are subject to the common test of rea-
sonableness in the courts. In general, this means
that the regulatory actions must not appear to be
arbitrary or capricious, must be generally related
to some accepted power of government and must seem
relevant to the intent of the regulatory process.
While the "reasonableness" of any regulatory
action may be subject to differing judicial inter-'
pretations, planners should seek to prevent any
obvious violation of the reasonableness test, and
should attempt to anticipate any challenges of
this kind, in creating regulatory procedures in
the 208 plan.
Due Process. All regulatory programs must provide
due process in this application to regulated
interests. This generally entails adequate public
notice of actions to be taken, the opportunity for
a public hearing, and the opportunity for judicial
review.
The "Taking Issue." -- When pollution regulation
involves restriction upon land use, the "taking
issue" may arise. In recent years, courts have
been increasingly confronted by property owners
asserting that a governmental restriction upon
their land use, particularly when imposed in the
interest of environmental protection or environ-
mental amenities, constitutes a violation of the
Fifth Amendment provision that private property
shall not "be taken for public use without just
compensation." This issue is likely to arise
especially when regulations restrict the most
economically advantageous use of the land. The
courts have devised very diverse rules for de-
ciding when government may properly restrict land
use and when such restriction is confiscatory.
It may be possible to avoid the "taking issue" if
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regulatory measures used in 208 planning are
carefully drafted and applied with these consti-
tutional limitations in mind. In general, the
courts are more likely to hold that a regulatory
program is not confiscatory when: (a) the law is
drafted with the explicit legislative intent to
serve a major public purpose such as the protec-
tion of public health and safety, the preservation
of water quality or other major public goals; (b)
there are statutory standards defining the limits
and conditions of regulation; (c) there is a
careful enumeration of permitted uses under the
law; and (d) data exists to provide reasonable
justification for the regulation.
o The "Equal Protection" Issue -- Regulatory measures
applied to all pollution sources within a 208 area
must be formulated in such a manner that the dis-
tinction between those regulated and unregulated,
and between classes of regulated activities,
satisfy judicial standards for equal protection
under the law as required by the 14th Amendment of
the Constitution. This means, three things:
(a) classifications must be based upon reasonable
and distinct characteristics that distinguish
between classes of activities; (b) the law must
apply equally to all activities in similar cir-
cumstances; and (c) the classification must bear a
clear relation to the purpose of the law.
General Procedures for Obtaining Needed Regulatory Authority
Based upon the preceding considerations, it is possible
to suggest some basic steps which should prove helpful in
providing 208 planners with an approach to obtaining proper
regulatory authority. Useful procedural steps are as
fo11ows:
• Inventory pollution sources to be regulated - -
It is important that planners develop a clear
conception of the specific pollution sources
that they must deal with in their own area so that
the range of needed regulatory controls can be
appreciated. It will be helpful, therefore, to
create an inventory of pollution sources for each
area.
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• Inventory existing agencies and their regulatory
powers within the 208 area -- Such an inventory,
when compared to projected regulatory goals,
should provide a preliminary indication of what
additional regulatory powers and agencies may be
needed to achieve the objectives in the 208 plan.
§ Create a regulatory plan with projected agencies,
powers and regulatory forms assigned -- Such a
preliminary plan, when compared to existing
regulatory resources within a 208 area, can
suggest where priorities should exist in seeking
additional regulatory powers.
• Evaluate projected regulatory arrangements with
particular attention to
the need to obtain regulatory powers from the
state or other agencies;
the need to clarify any implied power;
the need to clarify the nature of any
delegated powers; and
the adequacy of regulatory procedures in
terms of reasonableness and due process.
• Obtain additional regulatory authority or
adjust the regulatory plan to existing
authorities -- This process is likely to occupy a
major portion of the planning process and should
be regarded as a continuing process to be carried
out as the plan is implemented and revised. As a
result of this step, it may be necessary to modify
the projected 208 regulatory procedure. It may
be valuable, therefore, to have prepared several
alternative regulatory designs in anticipation of
necessary alterations in the original plan.
FUNDING
The funding of regulatory programs would not be such a
complex problem if we could think of it in terms of just
"raising money" and not as an allocation of costs and bene-
fits. However, the equity of cost allocation in pollution
control programs can make an enormous impact on the effec-
tiveness and public acceptance of such programs. EPA has
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generally favored user charge systems or other methods that
tie the amount of payments directly to the amount of pollu-
tion. This approach works considerably better of course for
point source problems such as building sewage plants than
for nonpoint problems. With urban nonpoint sources, the
most popular piece of advice in the literature is to place
the cost of control on the developer and therefore ulti-
mately on the future property owner. In most places around
the country, it is too late to implement this highly equit-
able solution because most urban development already exists.
In this respect, the western planners in energy developing
regions may realize considerable advantage. The costs of
both construction control and stormwater management programs
are easier to allocate equitably in the early stages of
development. This section will review the costs entailed in
regulatory programs, the sources of funding, and methods of
cost al1ocati on.
Costs
The costs incurred in a regulatory program may include
the following major categories:
o The costs of administering regulatory devices --
With permits and subdivision ordinances and other
site-oriented devices, administrative expenses are
incurred in the processing of permit applications,
the review of site plans by competent professionals,
provision of guidance to the developer in site
design, on-site inspection, and enforcement.
Inadequate funding for any one of these functions
may render the entire program ineffective. Pre-
ventive regulatory devices related to land use
controls entail planning costs and frequently
legal fees.
® Public works projects -- The cost of local public
works projects will be increased by the inclusion
of sediment control and stormwater management
features in construction plans.
« Continued monitoring and planning -- The "con-
tinuing planning" concept is being applied to
all facets of 208 programs. It is of major im-
portance with regard to non-point elements so that
we may continue to refine our understanding of the
problem and learn of the effectiveness of different
controls. This is especially true of the western
states where the nature of the problem is not
fully understood.
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• Capital projects -- Watershed or areawide storm-
water management plans may call for the construc-
tion and maintenance of major detention facili-
ties. In some cases it may not be wholly equit-
able to pass costs through to developers and more
acceptable to make such facilities- public pro-
jects.
Sources of Funding and Cost Allocation
In most instances, the form of fund raising will deter-
mine the allocation of costs. The costs of site control
measures are borne either by developers or the public as
follows:
• When a building permit or other regulatory
device requires control measures for private
development, the costs of implementing these
controls is borne by the developer.
• On public works projects such as roads, schools,
and other public facilities, the cost of control
measures will appear as an increase in the con-
struction cost. This cost is likely to be borne
by the general revenues of the local government.
These revenues can be from several sources in-
cluding bonds, property taxes, and revenue shar-
ing.
The costs of administering regulatory programs may be
allocated in a number of ways. It is at first apparent that
the regulatory device may be used as an instrument of taxa-
tion by the imposition of a fee. In this way, some portion
of administrative cost can be passed through to the devel-
oper. It is not likely, however, that the full costs of
administration could be handled in this fashion without
resulting in economic hardship and an unstable level of
agency funding. Therefore, some increment of funding will
have to come from general revenue sources. The same is true
of costs entailed in continuing monitoring and planning
programs. The other major cost category -- capital projects
-- is also a matter of the general revenue sources of local
general-purpose governments. Several general revenue
sources will be evaluated here.
o Property taxes are a good source of revenue which
can produce l^rge sums of money. However, prop-
erty taxes da not allocate costs according to the
degree of pollution but more according to the
a bi1i ty to pay.
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Special assessments are more equitable than
across-the-board property taxes because costs can
be borne by the specific property owners involved.
They may be particularly useful for funding
capital projects on a watershed or subwatershed
basis.
Bonding is useful for capital projects when there
will be more users of a facility in the future
than there are at present, such as a detention
pond on a developing watershed. This is because
bonding tends to delay project costs. The big
problem with bonds is determining the most
equitable way to pay them off. This opens the
question of revenue bonds vs. general obligation
bonds. For revenue bonds some sort of user charge
generates revenue to pay off the bond. Special
assessments as noted above can be applied to
watershed projects as a user charge system. With
general obligation bonds, the general tax revenues
of the local government may be tapped to pay off
the bond. The general obligation route is ob-
viously less equitable. It is also less feasible
as general obligation bonds often require a
referendum and there is a statutory limit on
indebtedness for some local governments.
Grants and revenue sharing funds are seemingly
appropriate sources of funding for the largely
energy-induced types of problems under considera-
tion. The Federal Government is collecting
leasing fees and state governments are collecting
coal taxes. To the extent that these funds can be
rechanneled through grants and revenue sharing to
assist local governments in coping with energy-
induced urban growth, the costs will be allocat-
ed -- quite equitably -- to the users of the
energy. Of course, the energy boom brings with it
more than just urban non-point source problems and
competition for these funds will be great. On the
other hand, the great number of energy impact
needs which could be serviced by such funding may
provide the impetus required to start the flow of
dollars through such channels.
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PUBLIC SUPPORT
In the western study area under consideration here,
public awareness and involvement in urban nonpoint sources
will be masked by the more general public debates over
energy development and 208 planning.
Numerous EPA guidance documents spell out techniques
and procedures for public involvement in 208 planning and
these will not be reiterated here. In terms of the urban
nonpoint problem, the purpose of public support is to
acquire the legal authority and funding necessary for
implementation of a regulatory program. It is the political
acceptability of the proposed program which will most affect
the outcome. It appears that the key criteria for this
acceptability would be:
• The degree to which local legal authority can be
utilized without submitting to regulation by a
regional, state, or Federal entity.
• The equity in the allocation of costs to those
who are causing the problem.
9 The local benefits from solving the problem.
In devising an acceptable solution, there will be
trade-offs between urban nonpoint sources and other parts
of the 208 program, and there will be interrelationships to
the rate and intensity of energy development. In this
context, the planner's task in generating public support
will be complicated. Not only will it be necessary to
develop an acceptable program but it will also be important
to present it clearly to the public against a potentially
confusing background.
The planner's success in generating public support will
hinge on his creativity, flexibility, and responsiveness in
designing a regulatory program. Perhaps the best approach
is the most careful -- examining each regulatory device,
each institutional arrangement, every building block of the
total program in terms of potential impacts on the legal
rights of local governments and property owners, the equit-
able allocation of costs, and the measurement of local
benefits. Programs for public involvement should be aimed
at defining these criteria of acceptability as early as
possible in the process of formulating alternatives and be
continued during the course of decision-making.
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IMPLEMENTATION STRATEGY
A well-conceived regulatory program will not neces-
sarily turn into a wel1-executed one. There is no com-
prehensive strategy for program implementation that can be
applied to a total program. However, there are some imple-
mentation strategies that can be applied to certain key
program components. Some of these approaches are described
here.
Planning As Close to Implementation As You Dare
Richard S. Page, Executive Director of the Municipality
of Metropolitan Seattle has coined the phrase, "planning as
close to implementation as you dare." The concept embodied
in the phrase is to get a firm political commitment at each
step in the planning process. The intent is to avoid
problems of implementation which arise when the only polit-
ical vote taken is a consensus on the total program. Such a
gross consensus tends to divert attention from the indi-
vidual responsibilities of the participants for implementa-
tion of program components. It is best to get a firm commit-
ment on each regulatory building block as you go along. In
short, to plan as close to implementation as you dare.
Periodic Review and Revision
The need for flexibility in a regulatory program was
stressed earlier. It will be important, especially in areas
of technical uncertainty, to keep a close watch on the
effectiveness of individual program components and on the
total program. However, modification of the program cannot
be made to appear too easy or arbitrary or under the control
of a few people. It is therefore desirable to incorporate
provision for a formal review and revision process on a
regular basis. The formality of the review process will
make it difficult to ignore a problem once it has been
identified and will force a consensus or a formal commitment
to support proposed changes.
Enforcement
From other state and local regulatory experiences, it
appears that there are five common areas where regulatory
programs fall down on effective enforcement.
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Teeth -- The legal authority must be adequate to
make compliance the path of least resistance.
Fines may be imposed. Developers may be required
to post bonds during the construction phase.
Police power may be exercised as in Maryland where
developers have actually been jailed for non-
compli ance.
Funds -- Perhaps the second most common cause of
regulatory failure is inadequate funding. That
lack of teeth and lack of funds are so crippling
and so common is further testament to the impor-
tance of the foregoing sections on public support
and cost allocation.
On-site inspection -- There is no substitute for
the effectiveness of direct on-site inspection by
a trained professional
Trai ni ng -- Enforcement personnel require a broad
technical background, a lot of common sense, and
broad human relation skills. Training programs
have been instituted in several states with
considerable effectiveness. Particularly in the
west, the availability of experienced field per-
sonnel may be a problem. In the early going, it
may be cost-effective to employ the services of
local professionals to assist in training tech-
nicians.
Monitoring data -- It is perhaps excusable during
the early phase of 208 programs to lament some
critical data gaps and proceed on the basis of
best judgement. As the implementation phase
progresses, however, it will become critical to at
least begin to address some of the major uncer-
tainties. This will require the continuous
monitoring of the effectiveness of individual
control and preventive practices.
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IV. SELECTED REFERENCES
1. Powell, M.D., Winter, W.C., Bodwitch, W.P.;
Community Action Guidebook for Soil Erosion and
Sediment Control; National Association of Counties
Research Foundation, Washington, D.C., 1970.
2. Crowley, J.N., "Nonpoint Source Control: Issues
and Implications," paper prepared for National
Association of Regional Councils, Washington, D.C.,
1 976.
3. Athayde, D., "Best Management Practices," paper
presented at EPA Urban Stormwater Management
Seminars in Atlanta and Denver, EPA Water Planning
Division, 1975.
4. EPA, "Interim Guidance on Development of 208
Regulatory Programs," prepared for the 208 Areawide
Water Quality Managment Workshop sponsored by the
National Association of Regional Councils, EPA
Water Planning Division, 1976.
5. Page, R.S., "The 208 Agency and the Management
Agencies," prepared for the 208 Areawide Water
Quality Management Workshop sponsored by the
National Association of Regional Councils, 1976.
6. Eisweiller, R.C., "What Is Needed to Implement
the Management Plan?", prepared for the 208 Area-
wide Water Quality Management Workshop sponsored
by the National Association of Regional Councils,
1 976 .
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APPENDIX A
LIST OF PUBLISHED SOIL SURVEYS IN THE STUDY AREA
Colorado
1947 Akron Area
1971 Atrapahoe
192.6 Arkansas Valley Area
1971 Bent
1932 Brighton Area
1899 Cache La Poudre Valley Area
1968 Crowley
1967 Delta-Montrose Area
1966 Elbert (eastern part)
1 927 Fort Col 1ins Area
1962 Fraser-Alpine Area
1905 Grand Junction Area
1955 Grand Junction Area
1904 Greeley Area
1929 Greeley Area
1930 Longmont Area
1902 Lower Arkansas Valley Area
1968 Morgan
1972 Otero
1971 Phillips
1966 Prowers
1903 San Luis Valley Area
1970 Sedgwich
1961 Trout Creek Watershed
1910 Uncompahgre Valley Area
Montana
1944 Big Horn Valley Area
1902 Billings Area
1914 Bitterroot Valley Area
1959 Bitterroot Valley Area
1953 Central Montana (Reconnaissance)
1905 Gallatin Valley Area
1931 Gallatin Valley Area
1967 Judith Basin Area
1929 Lower Flathead Valley Area
1939 Lower Yellowstone Valley Area
1940 Middle Yellowstone Valley Area
1928 Milk River Area
1929 Northern Plains of Montana (Reconnaissance)
1971 Powder River Area
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Montana (Continued)
1967 Treasure
1960 Upper Flathead Valley Area
1943 Upper Musselshell Valley Area
1958 Wibaux
1972 Yellowstone
Utah
1920 Ashley Valley Area
1904 Bear River Area
1960 Beryl-Enterprise Area
1913 Cache Valley Area
1970 Carbon-Emergy Area
1968 Davis-Weber
1919 Delta Area
1 959 East Mi 11ard Area
1939 Price Area
1903 Provo Area
1899 Reconnaissance of Sanpete, Cache, and Utah
1958 Richfield Area
1959 Roosevelt-Duchesne Area
1899 Salt Lake Valley Area
1946 Salt Lake Area
1962 San Juan Area
1900 Sevier Valley Area
192,1 Uinta River Valley Area
1972 Utah (central part)
1942 Virgin River Valley Area
1900 Weber Area
Wyomi ng
1928 Basin Area
1955 Campbell
1917 Fort Laramie Area
1971 Goshen (southern part)
1939 Johnson
1903 Laramie Area
1939 Sheridan
1927 Shoshone Area
1969 Teton Area Idaho-Wyoming
1940 Uinta
1926 Wheatland
By U.S. Department of Agriculture, Soil Conservation Service
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GLOSSARY
Abras i on - The wearing away by friction, the chief agents
being currents of water or wind laden with sand and other
rock debris and glaciers.
Acid Soil - A soil with a pH value of less than 7.0. For
most practical purposes, a soil with a pH value less than
6.6.
Ac re-foot - The volume of liquid or solid required to cover
1 acre to a depth of 1 foot.
Annual Plant (annuals) - A plant that completes its life
cycle and dies in 1 year or less.
Arroyo - A vertical walled gully resulting from the cutting
action of an intermittent stream.
Backfill - Replacement of material to achieve a specified
grade or slope.
Bedload Sediment - Sediment material rolled along the bottom
or bed of a stream.
Bedrock - The more or less solid rock in place either on or
beneath the surface of the earth. It may be soft or hard
and have a smooth or irregular surface.
Berm - A shelf that breaks the continuity of a slope.
Buffer Zone - Strip of vegetation which serves to trap
sediment from runoff water.
Channel - A natural stream that conveys water; a ditch or
channel excavated for the flow of water.
Check Dam - A structure used to stabilize the grade or to
control bank and head erosion in natural or artificial
channels.
Chute - A channel of concrete or comparable material that is
designed to conduct runoff downslope
Clay - A fine-grained mineral soil consisting of particles
less than 0.002 millimeter in equivalent diameter.
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Clearing - The process of removing vegetative cover from
a construction site.
Compaction - Any process by which the soil grains are re-
arranged to decrease void space and bring them into
closer contact with one another.
Conduit - Any channel intended for the conveyance of water,
whether open or closed.
Conservation - The protection, improvement, and use of
natural resources according to principles that will
assure their highest economic and social benefits.
Contour - 1: Outline of topographic features. 2: A line
drawn on a map connecting points of the same elevation.
Contour Interval - The vertical distance between contour
1 i n e s .
Detention Practice - Practice or structure installed for
the purpose of temporary storage of streamflow or
runoff and for releasing the stored water at controlled
rates.
Pi scharge - Rate of flow, commonly expressed as cubic feet
per second, million gallons per day, gallons per
minute, or cubic meters per second.
Diversion - Channel constructed across the slope for the
purpose of intercepting surface runoff; changing the
accustomed course of all or part of a stream.
Diversion Dike - A temporary ridge of soil constructed at
the top of slopes to divert overland flow away from
them.
Drainage Basin - All land and water within the confines of
a drainage divide.
Drainage Pattern - The configuration or arrangement of
streams within a drainage basin or other areas.
Ecology - The study of the interrelationships of organisms
to one another and to the environment.
Envi ronment - The sum total of all the external conditions
that may act upon an organism or community to influence
its development or existence.
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Erodi ble -
Susceptible to erosion.
Erosion - 1: The wearing away of the land surface by running
water, wind,ice, and other geological agents. 2 : De-
tachment and movement of soil or rock fragments by
water, wind, ice, or gravity.
Filter Inlet - A temporary filter of gravel or crushed
rock constructed at storm sewer curb inlets to retain
sediment and reduce runoff water velocity.
Fi1terstri p - See buffer zone.
F1o o d p1 a i n - Nearly level land situated on either side of
the channel which is subject to overflow flooding.
FIume - A channel of concrete or comparable material that
is designed to conduct runoff downslope.
Gabions - Rock filled baskets used in channels, retaining
walls, check dams, etc. to prevent erosion.
Groin - A shore protection and improvement structure. It
is narrow in width compared to its length.
Groundwater - Phreactic water or subsurface water in the
zone of saturation.
Gully - A channel or miniature valley cut by concentrated
runoff but through which water commonly flows only
during and immediately after heavy rains or during
the melting of snow.
Impoundment - An enclosed body of water, usually man-made.
Infiltration - The flow of a liquid into porous soil.
Interceptor Dike - A temporary ridge of compacted soil
constructed across a graded right-of-way.
Intermittent Stream - A stream or portion of a stream that
flows only in direct response to precipitation. It
is dry for a large part of the year, ordinarily more
than 3 months.
Mulch - A natural or artificial layer of plant residue or
other materials, such as sand or paper, on the soil
surface.
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Mulch Anchoring - A mechanical method which anchors
straw and hay by punching them into the soil.
Netti ng - A net composed of a variety of biodegradable
and wire products used for erosion control.
Outfall - Point where water flows from a conduit, stream,
or drain.
Permanent Stream - A stream which carries water throughout
the year.
Permeabi 1 i t,y - The capacity of soil or rock to allow the
movement of water through them.
Pol 1utant - Something that pollutes.
Pol 1ute - Impair the purity of.
Revetment - Facing of stone or other material, either per-
manent or temporary, placed along the edge of a stream
to stabilize the bank and to protect it from the
erosive action of the stream.
Rill - A small intermittent water course with steep sides,
usually only a few inches deep and, hence, no obstacle
to tillage operations.
Riprap - Broken rock, cobbles, or boulders placed on earth
surfaces, such as the face of a dam or the bank of a
stream, for protection against the erosive action of
water.
Runoff - That portion of the precipitation on a drainage
area that is discharged from the area in stream
channels. Types include surface runoff, groundwater
runoff, or seepage.
Scarification - To loosen or stir the topsoil without
turning it over as with a plow or shovel.
Sediment - Solid material, both mineral and organic, that
is in suspension, is being transported, or has been
moved from its site origin by air, water, gravity, or
ice and has come to rest on the earth's surface either
above or below sea level.
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Sedimentati on - The depositing of sediment.
Sediment Basin - A water or dry basin which detains and
holds sediment originating from runoff.
Sheetflow - Water, usually storm runoff, flowing in a thin
layer over the ground surface.
Stage Implementation - To accomplish by period, level, or
degree.
Staged - By period, level, or degree.
Tacki ng (mulch) - The process of binding mulch fibers
together by the addition of a sprayed chemical
compound.
Terrace - An embankment or combination of an embankment
and channel constructed across a slope to control
erosion by diverting or storing surface runoff
instead of permitting it to flow uninterrupted
down the slope.
Water Table - The upper surface of groundwater or that
level below which the soil is saturated with water.
Watershed - All the land and water within the confines
of a drainage divide.
Waterway - A natural course or constructed channel for
the flow of water.
Well Drained - Allows water movement readily but not
rapidly.
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