EPA-430/9-73-016
COMPARATIVE COSTS OF
EROSION AND SEDIMENT CONTROL,
CONSTRUCTION ACTIVITIES
Curb placed at top of fill
En_ergy dissi gator
"~""T
Stream
3erm left at t
of slopefat end of'
each days operation
0 riginal ground surface
(Scarify before fill placement)
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Water Program Operations
Washington, D.C. 20460
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c\ COMPARATIVE COSTS OF EROSION
*K AND SEDIMENT CONTROL,
.. j CONSTRUCTION ACTIVITIES
Project Officer
Robert E. Thronson
Prepared for
U. S. ENVIRONMENTAL PROTECTION AGENCY
Office of Water Program Operations
Water Quality and Non-Point Source Control Division
Washington, D. C. 20460
JULY 1973
U.S. Environ— *-i Protection Agency
Region 5, LiL :. 12J)
77 West Jacksur; :,,.jlevard, 12th FJonr
Chicago, IL 60604-3590
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $2.20
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ABSTRACT
Cost information on erosion and sediment control measures was assembled,
evaluated and documented for more than 25 methods in current wide-spread
use in both the humid Eastern and arid Western United States. Elemental
data for cost parameters were obtained for each method through extensive
investigation of erosion and sediment control contracts, estimates pro-
vided by contractor estimators, furnished job costs, equipment and supply
catalogues, and other sources. A wide range of costs was found between
one location and another; and conditions affecting these variations were
also determined. Most of the data presented were obtained from two
specific watersheds: Walnut Creek Watershed in Central California and
the Occoquan Watershed in Virginia. Relevant data from areas outside
these watersheds were utilized, where applicable.
Sediment removal cost estimates were made for typical situations where
unwanted sediment, which had been transported from construction sites
into adjacent areas and deposited, requires removal. The basis for making
these cost estimates generally was similar to those used in preparing
estimates for costs of control.
Theoretical soil losses were determined by using the improved universal
soil loss equation and the graphic methods for evaluation of factors used
therein. The hydrologic parameter for the soil loss equation was inten-
sively studied and simplified procedures for its computation were developed
and presented. Cost data were applied to theoretically predicted soil
losses for both of the selected climatologically different basins in order
to obtain costs per cubic yard (cy) of soil retained for conservation
measures and costs per cy of sediment removal with various methods.
Control effectiveness parameters and the duration of effectiveness of
each method were used to determine comparable annual cost figures. A
central conclusion of the study is that each particular location offers
a unique soil loss potential, erosion control costs and corresponding
sediment removal penalties. Costs of preventing the erosion and trans-
portation of sediments are, in many instances, lower than the cost of re-
moving the same quantities of sediments from downstream areas.
This report was submitted in fulfillment of the requirements of Contract
Number 68-01-0755 under the sponsorship of the Office of Water Program
Operations, U.S. Environmental Protection Agency.
iii
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TABLE OF CONTENTS
c. tJ Page No.
Section —°
I INTRODUCTION 1
1. The Problem 1
2. Purpose of This Study 1
3.. Scope of Study 2
II SUMMARY AND CONCLUSIONS 5
III BRIEF REVIEW OF STATE-OF-THE-ART, EROSION AND
SEDIMENT CONTROL 7
1. Introduction 7
2. Erosion 7
3. Sediment Yield and Delivery 8
4. Methods of Erosion Control 8
A. Vegetative 8
B. Structural 9
5. Effectiveness of Control 9
6. Cost of Erosion Control and Sediment Removal 9
7. Research in Progress 10
IV COST ESTIMATING PROCEDURES 11
1. Introduction 11
2. Basic Elements of Construction Costs 11
3. Assumptions and Conditions Governing Cost
Estimates 13
4. Cost Estimate for Wood Fiber Mulch Erosion
Protection Practices 14
5. Relating California Costs to Costs in Other
Areas 17
V EROSION AND SEDIMENT CONTROL COSTS 23
1. Introduction 23
2. Control Structures 23
A. Check Dams 23
B. Chutes/Flumes 28
C. Diversion Dikes 30
D. Erosion Checks 31
E. Filter Berms 33
F. Filter Inlets 34
G. Flexible Downdrains 36
H. Flexible Erosion Control Mats 38
I. Gabions 40
J. Interceptor Dikes 41
K. Level Spreaders 42
L. Sandbag Sediment Barriers 44
M. Sectional Downdrains 44
N. Sediment Retention Basins 45
0. Straw Bale Sediment Barriers 48
3. Fiber Mulches, Mulch Blankets, Nettings, and
Sodding 52
A. Excelsior Blankets 53
B. Jute Netting 53
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TABLE OF CONTENTS (Continued)
Section
VI
VII
VIII
IX
C. Straw or Hay
D. Woodchips
E. Wood Fiber Mulch
F. PETROSET Registered Trademark SB
SEDIMENT REMOVAL METHODS AND COSTS
1. Excavation or Similar Methods of Removal
A. Street Removal
B. Basement Removal
C. Storm Sewer Removal
D. Reservoir and Sediment Basin Removal
2. Removal by Dredging
3. Water Treatment Costs
A. Required Treatment Level
B. Chemical Costs
C. Sludge Disposal Costs
•D • Summary
ESTIMATING POTENTIAL SOIL LOSS
1. Introduction
2. The ARS Universal Soil Loss Equation
A. R, Rainfall Factor
Summary Procedures for Estimation of
Rainfall Erosion Index
K, Soil Erodibility Factor
L, Slope Length, and S, Slope Factors
C, Cropping - Management Factor
P, Erosion Control Practice Factor
3. Predicting Watershed Sediment Yields
4. Reservoir Trap Efficiency
B.
C.
D.
E.
F.
EFFECTIVENESS OF EROSION AND SEDIMENT CONTROL
MEASURES
1. Calculating Percent Effectiveness
A. Factor C Values for Urbanizing Areas
B. Factor P Values for Structures
C. Computing System Effectiveness
EVALUATION OF COSTS FOR SELECTED BASINS
1. Introduction
2. Selection Criteria
3. River Basins Selected
A. Occoquan Creek Basin, Virginia
1) Topography and Soils
2) Rainfall and Runoff
3) Development Projects
4) Type and Extent of Control Practiced
B. Walnut Creek Basin, California
1) Topography and Soils
2) Rainfall and Runoff
3) Development Projects
4) Type and Extent of Control Practiced
Page No.
54
55
56
58
61
61
61
61
63
63
67
68
68
69
69
70
73
73
75
75
76
85
88
88
88
91
91
95
95
96
97
100
103
103
103
104
104
104
110
113
113
113
113
117
117
117
VI
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Section
APPENDIX A
APPENDIX B
APPENDIX C
TABLE OF CONTENTS (Continued)
4. Cost of Typical Erosion and Sediment
Control Plan
5. Economic Costs
6. Comparative Costs of Controlling Sediment
A. Occoquan Creek Basin
B. Walnut Creek Basin
C. Projects with Life Less than 10 Years
D. Highway Construction (Steep Slopes)
E. Other Costs and Benefits
DETAILED COST ESTIMATES
DERIVATION OF EQUATION FOR EROSION INDEX
El
TOU
FROM TYPE I AND TYPE II STORM DISTRIBU-
TION CURVES
LIST OF SELECTED REFERENCES
Page No.
119
122
122
122
125
126
128
129
131
181
195
vn
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LIST OF FIGURES
»
Figure Page
1 Approximate Relationship Between Cost Per Acre, and 16
Size of Area for Wood Fiber Mulch, Fertilizer, and
Seeding, Typical for San Francisco Bay Area, California
January 1973
2 Small Rock Riprap Check Dams, with Gabion Sidewalls 24
3 Typical Grouted Rock Riprap Check Dam (Courtesy Food and
Agriculture Organization of the United Nations) 25
4 Concrete Check Dam with Energy Dissipator (Reference 120) 26
5 Chute/Flume (Reference 120) 29
6 Diversion Dike (Reference 120) 30
7 Fiber Glass Erosion Check (Reference 120) 31
8 Erosion Check (Reference 120) 32
9 Filter Berm - Installed (Reference 120) 33
10 Filter Berm - Cross Section (Reference 120) 34
11 Filter Inlet - Installed (Reference 120) 35
12 Filter Inlets - Installed (Reference 120) 35
13 Flexible Downdrain - Isometric (Reference 120) 37
14 Flexible Downdrain - Installed (Reference 120) 37
15 Schematic of Flexible Mat Subsequent to Grouting
(Courtesy VSL Corporation) 38
16 Installation of Flexible Erosion Control Mats in a
Drainage Canal with High Ground Water Table (Courtesy
of VSL Corporation) 39
17 Detail of Installed Flexible Erosion Control Mats
(Courtesy of VSL Corporation) 39
18 Gabions - Channel Bank Protection (Reference 120) 40
19 Gabions - Channel Lining, Check Dam, and Bank Protection 41
(Reference 120)
20 Interceptor Dike (Reference 120) 41
21 Interceptor Dike - Installed and Outleting to Storm
Sewer Inlets (Reference 120) 42
22 Level Spreader (Reference 120) 43
23 Small Diversions Very Similar to Level Spreaders. If
Both Lip and Bed are Constructed at Zero Grade These Would
Be Level Spreaders. (Reference 120) 43
24 Sectional Downdrain 44
viix
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LIST OF FIGURES (Continued)
Figure Page
25 Small Sediment Basin With Outlet Pipe Discharging
On Energy Dissipator to Prevent Erosion at Discharge
End (Revised from California Division of Soil
Conservation, Reference 92) 46
26 Large, Well-engineered Sediment Basin Dam. Note Outlet
Pipe with Riser, Gravel Core Filter, and Seepage-path
Cut-off On Outlet. (Revised from Fairfax County,
Reference 92, Figure No. 35) 47
27 Sediment Retention Basin - Small, Less than 1/4- acre
in Size (Reference 120) 48
28 Temporary Barrier of Hay Bales to Prevent Sediment-
laden Water from Entering Incomplete Storm Sewer System
(Revised from Fairfax County, Reference 92, Figure No. 17) 49
29 Semi-pervious barrier of Hay Bales with more Pervious
Embankment of Sand and Gravel for Spillway (Revised
from Fairfax County, Reference 92, Figure No. 31) 50
30 Straw Bales at Storm Drain Inlet (Reference 120) 51
31 Straw/Bale Structure on Property Line (Reference 120) 51
32 Excelsior Blanket and Staple (Reference 120) 53
33 Jute Netting Being Installed (Reference 120) 54
34 Large Straw Mulching Operation (Reference 120) 55
35 Spreading Wood Chips on Homesite (Reference 120) 56
36 Hydroseeder applying Seed, Fertilizer, and Mulch on Cut-
slope Adjacent to Newly-constructed Road. (Spalding County
Georgia, Courtesy SCS, Reference 92) 57
37 Wood Fiber Mulch in Place (Close-Up) (Reference 120) 58
38 Chemical Soil Stabilizer Being Applied to an Area That
Will be Seeded at a Later Date. (Reference 120) 59
39 Erosion and Deposition of Sediment in Streets. Bowie,
Maryland (Courtesy SCS, Reference 92) 62
40 Deposition of Dediments from Erosion of Newly-Constructed
Athletic Field Farther Upslope. Washington, D.C.
(Courtesy SCS, Reference 92) 62
41 Small Sediment Basin Ready for Removal of Trapped
Materials. Gaithersburg, Maryland (Courtesy SCS,
Reference 92) 65
42 Accumulated Sediment Being Removed from Small Basin in
Maryland (Courtesy SCS, Reference 92) - 65
43 Large, Well-designed Sediment Basins in Construction Site
Area for the Malibu Campus of Pepperdine University,
California (Courtesy Los Angeles County Flood Control
District, Reference 92) 66
ix
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LIST OF FIGURES (Continued)
Figure Page
44 Treatment Costs by Filtration and Coagulation-
Filtrations Includes Capital and Operational
Costs (ENR Construction Cost Index 1800) 71
45 Annual Iso-erodent Map of Areas East of the Rockies
(Reference 136, ARS) 78
46 Time Distribution of the Dimension Less Rainfall Depth
for Two Storm Types (Reference 104, SCS) 79
47 Relation Between Annual Average Erosion Index and the
2-yr 6-hr Rainfall Depth for Two Rainfall Types 80
48 Depths of the 2-yr 6-hr Rainfall, Inches, in Various
Parts of the United States (Reference 123, 124, USWB) 81
49 Iso-erodent Map Derived from 2-yr 6-hr Rainfall Map.
Superimposed for Area East of the' Rockies 82
50 Relation Between Depths and Duration of Type I Rainfall
and Single-Storm Erosion Index. 2-yr Frequency of
Occurrence 83
51 Relation Between Depths and Duration of Type II Rainfall
and Single Storm Erosion Index. 2-yr Frequency of
Occurrence 84
52 Nomograph for Estimating K-Values of Soils (Reference 137) 87
53 Slope-Effect Chart (Topographic Factors, LS)
(Modified from Reference 105) 89
54 Extensions of the Slope-Effect Chart (Topographic Factors
LS) (Modified from Reference 105) 90
55 Relationship Between Capacity/Inflow Ratio and Sediment
Trap Efficiency of Reservoirs 93
56 The Occoquan Creek Drainage Basin Northeastern Virginia
(Numbers identify development projects listed in text) 105
57 USDA Guide for Textural Classification 106
58 The Walnut Creek Drainage Basin, Central California
(Numbers identify development projects listed in text) 114
59 Example of a Sediment and Erosion Control Plan 120
60 Economic Cost of Conserving a Ton of Soil Per Year 123
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ACKNOWLEDGEMENTS
The valuable assistance and information provided during the preparation
of this report by the following organizations and individuals is gratefully
acknowledged.
Engineering-Science, Inc., Consulting Engineers - Principal
Consultants on this Report
Corps of Engineers, U. S. Army
Naval Facilities Engineering Command
U. S. Geological Survey
U. S. Soil Conservation Service
International Erosion Control- Association
Planning Public Works and Soil Conservation Department of following
Virginia Counties:
Prince William, Fairfax, Fauquier, and Loudoun
Virginia State Water Control Board
Northern Virginia Regional Planning Commission
Fairfax Water Authority, Virginia
Prince William County School Board, Construction Division
Occoquan Monitoring Committee, Virginia
Allis Chalmers Equipment Corporation, Washington, D. C.
Beatty-Elmore Construction Co., Virginia
Dewberry, Nealon & Davis Engineers, Gaithersburg, Maryland
Fairfax Quarries , Centerville, Virginia
Grant Construction Company, Manassas, Virginia
Ridge Development Corporation, Occoquan, Virginia
Sherman Construction Company, Fairfax, Virginia
Southern States Cooperative, Manassas, Virginia
Springdale Construction Company, Fairfax, Virginia
XI
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ACKNOWLEDGEMENTS (Continued)
Vulcan Materials Company, Manassas, Virginia
Weaver Bros. Development Corp., Springfield, Virginia
Yeonas Company, Vienna, Virginia
California Division of Highways
Contra Costa County Planning Commission
East Bay Municipal Utility District
Los Angeles County Flood Control District
University of California, Davis
Cities of Concord, Lafayette, Pleasant Hill, and Walnut Creek,
California
Ellicott Machine Corporation, Dredge Division, Baltimore, Maryland
Jacobs Associates, Engineers and Consultants, San Francisco,
California
Materials Research and Development, Oakland, California
Cagwin & Dorward, Landscape Contractors & Engineers, San Rafael,
California
Economy Garden Supply Company, Oakland, California
George's Contractor's Supply, Inc., Sacramento, California
VSL Corporation, Los Gatos, California
Western Process Fibers, Inc., Placerville, California
Zurn Engineers, Contractors, Upland, California
And all others who contributed towards the compilation and completion of
the study, and without whose efforts this report could not have been
presented.
xii
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LIST OF ABBREVIATIONS
The abbreviations, signs, and symbols used in this report are standard and
conform to those appearing in the Government Printing Style Manual. In each
instance, the first time an abbreviation, sign, or symbol is used it appears
parenthetically after the word or term for which it stands or describes.
ARS
AWWA
CA
ENR
EPA
ES
LACFCD
SCS
TP
TR
USDA
USWB
VA
ac
bbl
bf
bm
cf
cfs
cwt
cy
ea
ft
sq.
hr
Ibs
If
1
m-days
mg
mgd
m-hr
OH
P
S4S
sf
ft
sy
yr
@
Agricultural Research Service, USDA
American Water Works Association
California
Engineering News-Record Magazine
Environmental Protection Agency
Engineering-Science, Inc.
Los Angeles County Flood Control District
Soil Conservation Service, USDA
Technical Paper
Technical Release
United States Department of Agriculture
United States Weather Bureau
Virginia
Units and Symbols
acre
barrel
board feet
board measure
cubic feet
cubic feet per second
hundredweight
cubic yard
each
feet
square feet
hour
pounds
lineal feet
liter
man days
milligram
million gallons per day
man hour
Overhead
Profit
Square four Sides
square feet (Tabulations Only)
square yard
year
at
percent
cents (U. S.)
dollars (U. S.)
foot (Tabulations Only)
inch (Tabluations Only)
per
degree, minute
change
xiii
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SECTION I
INTRODUCTION
1. THE PROBLEM
Natural erosion processes inevitably are accelerated when existing pro-
tective cover is removed before or during construction of land development,
highway, or airfield facilities. Increased exposure of the soil mantle to
the full kinetic energy of falling rain, hail, and overland and channelized
flow, plus the dynamic mechanical action of men and machines as they move
over the site, cause increased movement and loss of soil particles. While
this erosion of soil frequently causes on-site construction problems, it
is even more common for the sediment removed to create many undesirable
conditions in downstream areas. Furthermore, loss of the soil from the
site is, in many instances, a loss of a valuable natural resource.
Erosion of still-unpaved streets, embankments, and building foundations
are not uncommon sights in the expanding urban areas of America today.
Deposition of the eroded sediments in storm sewers, culverts, drains,
and waterways decreases their capacities or completely clogs them, which
in turn results in flooding of adjacent and downstream lands. Valuable
reservoir storage is lost and domestic water supplies become turbid, or
water filters clogged, following storms. Beautiful lakes become dirty
and unattractive bodies of water for long periods of time, with adverse
effects on water-related recreation. Numerous new-home owners sometimes
awake to find their yards or streets or even their homes filled with mud.
Most of these adverse results from man's construction activities can be
reduced, and, in many instances, eliminated by use of both structural and
non-structural measures of various types, properly utilized, at the ap-
propriate time.
Selection of the proper measures to use in any specific situation, however,
requires the availability of both technical and comparative cost infor-
mation on the various methods.
2. PURPOSE OF THIS STUDY
"Guidelines for Erosion and Sediment Control Planning and Implementation"
was published by EPA in August 1972 (Reference 120), and "An Economic
Analysis of Erosion and Sediment Control Methods for Watersheds Under-
going Urbanization" was published by the Department of the Interior in
1972 (Reference 26). The first publication summarizes most of the avail-
able structural and vegetative control methods which can be used. It can
be used both by the layman and the conservation specialist. The second
provides extensive analyses of erosion control costs in selected urbanizing
watersheds in Maryland, near Washington, D. Co, and estimates of the
economic values of damages resulting from erosion in those areas.
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The purpose of the present study is to extend the work and data of the
previous reports and, more specifically, to provide reliable information
on: (1) The cost of retaining sediments on construction sites per cubic
yard (cy) of material retained. (2) The cost of correcting damages re-
sulting from erosion and sediment deposition on the site and in downstream
areas per cy of material removed.
3. SCOPE OF STUDY
In this study data have been obtained for two different climatic areas in
the United States; one being in the relatively semi-arid area of California,
primarily Northern California, and the other being located in Virginia,
which is in the more humid eastern part of the nation. Rainfall distribu-
tion over the year is quite different in the two areas, the soils are not
the same, labor costs differ, and the extent of erosion control practiced
on construction sites generally is much more limited in the Walnut Creek Basin
as compared to the Occoquan Basin. The types of control measures available
or used, however, are essentially the same.
Areas with significant differences in clima-tic parameters were selected
deliberately, not only to provide a broader data base, but also to help
focus on the important parameters influencing amounts, times, and rates
of soil erosion on and near construction sites, so that these parameters
could then be used in other climatic areas of the United States in plan-
ning, designing, and evaluating erosion control measures and practices.
Several such parameters were identified, and illustrative examples are
given of their application in the study areas, together with discussions
of how the same approaches can be used in other regions. Limitations of
the methods are also stated.
It was realized at the beginning that a simple presentation of unit costs
per cy of sediment retained or removed could be misleading if the
conditions to which it applies are not fully specified. Labor, material,
and equipment costs vary from place to place. Furthermore, present costs
can change, and the historic trend is that these costs increase, at dif-
ferent rates. In addition, "costs" depend upon accounting methods and the
type of organization performing the work. The same work can have a dif-
ferent "cost" if reported by a home owner who has largely performed the
work himself, by a city or county public works department, or by a con-
tractor for a client, even though the equipment, material and manpower
used were substantially identical. This report therefore presents most
costs of erosion control practices and sediment removal work in terms of
the three elements: labor, equipment, and materials. To further aid in
understanding the mark-up of construction costs for these measures, allow-
ances for overhead and profit are identified, so that contractors and
government agencies can more readily use the data in developing or comparing
their own estimates, based on local conditions.
Where appropriate, the effectiveness of the various methods are presented,
although only qualitative information is available in some instances.
Quantitative evaluations of erosion control practices are based on estimates
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of soil loss with and without the practice, as measured by the universal
soil loss equation (Reference 136). Its applicability to the western
United States has not yet been verified, because of differences in rain-
fall intensity patterns in the West compared to the eastern United States
where all the experimental data was obtained. Nevertheless, analyses
made during this study and summarized herein give additional evidence that
the equation is applicable to the western as well as to the eastern United
States, and to many other areas of the world. Examples of and instructions
for its use are presented.
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SECTION II
SUMMARY AND CONCLUSIONS
Costs of controlling sediments on site or removing them from downstream
areas vary widely, even in a single region, due to differences in objec-
tives, in the materials and practices used, and the relative effectiveness
and durability of the practice applied or feature installed.
Unit costs of erosion prevention measures or sediment removal methods
obtained in one area cannot be transferred to other areas for the purpose
of estimating total costs without proper adjustments for climate, soils,
terrain, materials, labor, equipment, and degree of performance desired.
The detailed cost estimates presented in this report for over 25 measures,
practices, and methods provide a reasonable basis for estimating local
costs for similar control methods.
The hydromulching method of applying protective covering to disturbed soil
surfaces has emerged as a most economical, effective and practical erosion
control method. The unit cost of hydromulching ranges from less than
$400 per acre for areas of 15 acres and over with a minimum of constraints,
to as high as $900 per acre for areas of less than one acre.
The more costly methods of preventing sheet and rill erosion on sloping
land surfaces, such as those using excelsior matting and jute netting,
generally are more durable on the steeper slopes than the less expensive
methods such as hydromulching. As these higher-cost methods usually are
most applicable to places where the erosion potential is the greatest,
they often are economically justified.
The annual erosion potential in the Occoquan Creek Basin in Eastern
Virginia is estimated to be approximately five times as great as that in
the Walnut Creek Basin in California. Furthermore, the erosion potential
during the summer construction season in Virginia is at its peak, while
the erosion potential in California is practically non-existent during
the same period of time.
The universal soil loss equation is the best index presently available
to predict relative soil loss due to sheet and rill erosion. It is most
reliable for slopes under 20 percent* It should be recognized, however,
that the equation is semi-empirical, does not necessarily yield precise
absolute values of erosion, and is subject to further modification, or
replacement, as the results of current and future research work and anal-
yses become available. It is most valuable when interpreted by qualified
users.
More field experiments and research data are needed regarding erosion on
steep slopes to permit the application thereto of the universal soil loss
equation, or the development of a better, more applicable equation.
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More research work is needed to develop quantitative data and comparisons
of the actual "effectiveness" of most conservation measures. Effectiveness
figures now available are based on the considered judgments and experience
of experts in soil conservation work, and, while suitable for use until
better data are obtained, need field confirmation to increase confidence
in their validity.
Costs of preventing soil erosion and sediment runoff per unit of sediment
retained, are less, in a great many instances, than the cost of later re-
moving the silt from homes, streets, stream channels, estuaries, bays, or
domestic water supplies.
Although more and more erosion-conscious construction specifications,
together with increased labor and materials costs, have forced unit costs
upward, new and continuing improvements in techniques have kept the rate
of increase within reasonable limits.
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SECTION III
BRIEF REVIEW OF STATE-OF-THE-ART,
EROSION AND SEDIMENT CONTROL
1. INTRODUCTION
While the basic processes of sediment erosion, transport, and deposition
are essentially the same from one place to another, the environment in
which they take place is subject to continuously changing and increasingly
complex stresses, most of which are induced by man. The need for know-
ledge in erosion and sediment control techniques is increasing. (Refer-
ence 2) .
It is essential that erosion and sediment control problems be approached
from the standpoints of judicial use of existing information and technical
data, and continued search for and assessment of new and definitive tech-
niques related to the problems. However, since the objective of this re-
port is to collect facts on cost of erosion and sediment control and sedi-
ment removal, only a brief review of the state-of-the-art is presented
herein. For detailed and exhaustive review of literature and state-of-
the-art, the reader is referred to References 26 and 48. The draft copy
of the state-of-the-art synthesis which was recently made available on
"Erosion Control on Highway Construction Projects" produced by the National
Cooperative Highway Research Program, Project 20-5 (dated January 1973),
contains summary information on current erosion-control practices and
refers to numerous articles on the subject. The selected list of refer-
ences at the end of this report contains 140 additional sources of valu-
able information pertinent to this study.
2. EROSION
Much of the soil erosion research to date has been conducted for resolving
agricultural problems, and directed towards unravelling the complexities
of erosion phenomena from disturbed topsoils and subsoils. Most urban
development projects, construction work sites, and major highway projects
also involve exposed and disturbed soils which are readily amenable to
natural erosive forces. Erosion of subsoils is becoming increasingly
important becuase of changing design criteria and ever-increasing size of
sub-divisions and other construction and highway projects. The time re-
quired for the construction of large projects has been increasing and
consequently erosion problems during construction have become very real
and extensive. (Reference 2),
Soil erosion is essentially the detachment and relocation of soil particles
through the dynamic action of water or wind. This fact led early in-
vestigators of erosion phenomena to examine the inherent properties of
various soils in an effort to develop an index to describe or quantify the
erodibility of soils. Middleton's (Reference 63) dispersion ratio and
erosion ratio, and Anderson's (Reference 3) surface aggregation ratio,
while important technical contributions, are of little use today, as
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erosion indices because they reflect only the intrinsic properties of
soil and do not consider physiographic and hydrometeorological factors.
In 1947 Musgrave (Reference 68) attempted a quantitative evaluation of
loss of soil by water erosion by also taking into consideration the slope
and length of agricultural lands.
Refinements to the Musgr-ave equation and extensive field and laboratory
investigations produced by 1958 an equation known as the universal soil
loss equation, which currently is used by the U.S. Soil Conservation
Service to estimate gross erosion from rainfall on farmlands east of the
RockieSo This equation developed by Wischmeier, Smith, Uhland, and others,
(References 131 through 137), includes parameters representing both the
properties of soil and the external influences of rainfall, overland slope,
land management practices, and surface cover conditions. Improvements
have been and are being introduced to make the equation truly universal,
so that it is applicable to both agricultural and non-agricultural land,
and for short-term as well as for long-term conditions (References 61,
95, 105, 107).
More detailed information on the applicability and use of the universal
soil loss equation is presented in Section VII.
3. SEDIMENT YIELD AND DELIVERY
Investigators of the erosion phenomenon recognized the close link between
erosion and other sedimentation processes. Various empirical equations
were developed for predicting sediment yield based on known or measure-
able watershed parameters (References 25, 27, 34, 64, 68, 74, 129 and 130).
Musgrave's (Reference 68) early attempts at predicting sediment yield was
further refined when the sediment delivery ratio was introduced to take
into consideration that not all the gross amount of eroded material leaves
the watershed. As the area of the watershed increases the amount leaving
the watershed decreases (Reference 74). However, the sediment delivery
ratio has proven to be a special characteristic of the watersheds studied
and of the conditions during the period of study, and therefore, a mul-
titude of equations have been developed (References 64, 74, 130).
4. METHODS OF EROSION AND SEDIMENT CONTROL
Erosion control methods fall basically into one of two broad categories.
These are designated as vegetative and structural measures„ In actual
field practice a combination of methods, suitable to the particular site,
are employed. Chemical mulches may be placed in a class by themselves.
However, because they are usually applied to support and insure emergence
of vegetation seeds, they are included in this report under vegetative
measures.
A. Vegetative
Vegetative measures include perennial grasses and legumes; annual cover;
trees, shrubs, and vines; and mulches (organic and inorganic) to support
-------
vegetation and protect soil. The recent development of hydromulching has
gained a degree of success in applying grass seed mixed with wood fiber
and water under pressure. Well-anchored vegetative mulch has proven to
be an effective and least costly of all mulching materials in controlling
erosion from denuded areas.
Commercial materials available for controlling erosion used in conjunction
with or without vegetative treatment are many and varied. Chemical mulch-
ing products, which are designed to prevent erosion during rainstorms until
vegetation takes hold, include: polyvinyl alcohol, a resin product, an
elastromeric polymer emulsion, Curasol (Reference 41) and Landlock (Re-
ference 60).
A large number of new chemical products are on the market and tests are
being carried out by several agencies to determine their relative effective-
ness (Reference 60).
B. Structural
Structural measures include: small flood control dams, dikes and levees;
stream channel improvements and bank stabilization works; sediment basins
and outfall structures; terraces, diversion structures and channels;
grassed waterways and outlets; grade stabilizing structures such as chutes,
checkdams and drop spillways (Reference 100). A recent development in
highway cut sections is the serrated side slope.
5. EFFECTIVENESS OF CONTROL
Wischmeier and Smith (Reference 136) included two factors in the universal
soil loss equation which indirectly take into consideration the effective-
ness of various vegetative and conservation practices in reducing or con-
trolling erosion. These two factors are the cropping-management factor
(C) and the erosion control practice factor (P). No set procedure or
method to calculate percent effectiveness of a given set of erosion con-
trol methods has been prescribed, as yet. Many attempts at quantifying
the percent effectiveness have been attempted (Reference 26, 36, 60, 62,
107)o However, the results are sparse and non-conclusive at this point
in time. One method which has much merit and which is presently in general
use is that described in Reference 26, where the percent effectiveness is
derived by subtracting the product of C and P factors from unity and mul-
tiplying the result by 100. More detailed information on the procedure
is presented in Section VIII.
6. COSTS OF EROSION CONTROL AND SEDIMENT REMOVAL
Review of published and other available literature indicates that infor-
mation on the cost of erosion control is very limited (References 12, 24,
26, 54, 55, 58, 60, 70, 92). In most cases the information presented does
not adequately identify the physical conditions under which the actual
work is performed. Inflationary trends, both in labor and material costs,
cannot be readily divorced from the cost data, nor can improvements in
-------
erosion control techniques be simply taken into account. Furthermore,
in comparing one erosion project cost to another, the method of costing
used by any two different contractors is not usually described in detail
in the majority of cases, to enable one to arrive at valid conclusions.
Available data on cost of sediment removal methods (References 52, 53, 54,
55, 58 and 70) are very limited in scope.
7. RESEARCH IN PROGRESS
Research and development work related to soil erosion and sedimentation
currently is being conducted at private, state and federal levels in the
United States and in foreign countries such as Germany, Japan, and the
United Kingdom. Some of the major areas of emphasis can be categorized
as follows:
(1) Studies of soil cementation and/or aggregation using cement,
lime, aluminum and iron oxides, carbide sludge, slag from iron
mills and pulverized fuel ash.
(2) Studies of soil stabilization with vegetation, chemicals and
biochemical or other soil reinforcements.
(3) Further development of the principles and practices of erosion
control and soil conservation.
(4) Analysis and correlation of erosion and sedimentation with
topographic and hydrologic parameters, and the development of
improved soil loss prediction equations.
(5) Categorization of types of pollutants resulting from soil
erosion, and definition of extent and relative importance of
their occurrence„
10
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SECTION IV
COST ESTIMATING PROCEDURES
1. INTRODUCTION
A primary objective of this study is to provide reliable data on the costs
of controlling erosion and retianing sediments on construction sites, and
on the costs of correcting damages resulting from soil erosion and deposition
on the site and in downstream areas. When these costs are converted to
comparable costs per cubic yard (cy) or per ton of sediment retained, these
units can be used to judge relative economic effectiveness of various mea-
sures. Similar unit costs for the removal of sediments eroded and then de-
posited elsewhere also can be used for comparing methods of correcting these
types of damages. Costs per unit area, such as per acre (ac) or per square
yard (sq. yd) are also often used as a quick basis for comparison or for
estimating overall costs of erosion control.
While such unit costs are of value they should be used with caution, as
much further definition of the variables involved is needed for a true
comparison to be made. Unless the soils, climatic, and site conditions
are similar, the identical protective measure, for example, built at the
same cost, may yield a considerably different cost per ton of material re-
tained when constructed at another site. The economic value of a ton of
clay loam retained on-site is hard to compare to a ton of sandy loam at the
same, or at another site. A rigorous economic analysis of these variables
is not within the scope of this study. For the purposes of this report,
it is assumed that the important parameters to consider are: (1) the costs
of preventing soil from eroding, or leaving a construction site and enter-
ing a stream or lake, and (2) the costs of removing soil once it has been
eroded and deposited temporarily in another location. Emphasis is therefore
placed on the costs of the practices or measures used. These values can be
of considerable help to those involved in planning or budgeting for erosion
control or sediment removal related to construction activities.
2. BASIC ELEMENTS OF CONSTRUCTION COSTS
For maximum usefulness the cost of any specific structure or measure should
be defined in terms of:
(1) Makeup of Cost Figure
(a) Equipment Costs (depreciation, interest, taxes, insurance,
fuel, maintenance, and repairs)
(b) Labor (operators, others)
(c) Materials
(d) Supervision
(e) Design (if required)
(2) The procedure, measure, operations, or practice, to which it
applies
11
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(3) The time period for performing the work
(4) The physical and climatic conditions under which the work is
performed
Added to the preceding may be other allowances as appropriate, such as:
Private Contractor - Overhead and Profit
Force Account - Overhead
Contingencies
The foregoing items normally are considered by an organization actually
performing the work and can be termed a fundamental, or contractor,
approach to cost estimating, as contrasted to the often more familiar unit
price approach used by most non-contractors. A unit price, say per lineal
foot (lineal ft) of diversion berm, is convenient and easy to apply, but
it is difficult and possibly misleading to transfer such a unit cost de-
rived from one particular job to another job without modification. On the
other hand, if the principal elements are known, a more meaningful trans-
fer, with proper adjustments for differences in materials, labor, and
equipment costs, and site and climatic conditions, can be accomplished.
While a statistical average of unit costs from many jobs has more validity,
especially if derived from similar operations in a limited geographical
area, this approach unfortunately is difficult to use in the cases under
study in this report, because of the scarcity of available data. Even in
the case of the Occoquan River Basin in an area where a considerable amount
of work of this type has been performed, cost figures for separate struc-
tures or facilities were rarely found. The reason for this data scarcity
is that it is normal for the contractor to have his men and equipment work-
ing on several such features during the same week, or even day, and the
job accounting records do not pinpoint the manhours (m-hr) or machine-
hours by each structure or practice. Indeed, in many instances the records
may not even identify erosion control practices as separate work items,
but may include them as part of Site Grading and Preparation. However,
during interviews with contractors they were able to outline the proce-
dures used and many important cost items.
The Contractor cost-estimating approach has been used, therefore, as the
principal basis for the costs presented in this report. This procedure
has not been followed in all cases, particularly for items such as dredg-
ing, where the site and performance conditions yield an almost limitless
range of possible costs and are of a very specialized nature. It should
be mentioned also that while the estimates presented in this report follow
a contractor-approach format, every contractor has a particular format
which he uses, and even more details and cost breakdowns can be used in
estimating a job than are given in the examples herein presented.
Even though this fundamental approach has been used, there are still many
local site conditions which can change costs from those presented herein.
The more important of these influences will be discussed subsequently.
12
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3. ASSUMPTIONS AND CONDITIONS GOVERNING COST ESTIMATES
Wherever possible, uniform application procedures were used for the several
elements of the cost estimates. Unless an exception is noted thereto in
the detailed estimate in Appendix A, the following conditions apply to
all estimates.
(1) Climatic conditions are considered to be average.
(2) Access conditions are considered to be average.
(3) Materials, Labor and Equipment Costs are as of the end of the
calendar year 1972.
(4) Labor rates include fringe benefits such as vacations, medical
and pension plans, training, welfare, and promotion funds. They
are intended to approximate union scale wages in the San Francisco
Bay Area of California and the Washington, D. C. - nearby
Virginia Area.
(5) To all labor costs, 18 percent was added to account for employer
payments toward Social Security (6%) Workmen's Compensation
Insurance (10%) and Unemployment Insurance (2%).
(6) 25 percent was added to the total of basic materials, labor and
equipment costs to cover contractor overhead and profit.
(7) Exceptions were made to the overhead procedures set forth in
Items 5 and 6 immediately preceding. For very small jobs a
total overhead 45 percent was added to basic costs, rather than
treating labor and general overhead charges separately.
(8) Equipment costs are based on hourly equivalent rental rates,
generally assuming that the equipment can be rented at the equiv-
alent of hourly rates based on a 40-hour per week weekly rental
rate. (Monthly rental rates are usually lower, and daily rates
higher than weekly rates). These costs exclude the operator, but
include fuel, maintenance, repairs, interest, insurance, taxes,
and depreciation.
(9) Labor and equipment charges during "move-in and move-out" are
included for most non-structural practices. For structural
measures it has been assumed that the erosion control work is
part of an on-going construction project, and that men and
equipment may be delivered from other parts of the work.
(10) Most jobs are considered to be performed on a relatively small
scale. Where the work can be performed by contractor forces
on a larger scale, unit costs can be reduced.
13
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(11) Non-emergency conditions are assumed. Hence labor at overtime
rates is minimal, being applicable only in a few instances.
(12) No contingency allowances are provided.
(13) Maintenance costs are not included.
4. COST ESTIMATES FOR WOOD FIBER MULCH EROSION PROTECTION PRACTICES
As an example of basic cost estimating, a breakdown of the cost of Wood
Fiber Mulch erosion protection is summarized in Table 1.
The following specifications apply:
(1) Fumigate with Methyl Bromide - 24 hours prior to operation, if
specified. Cost with, and without, shown.
(2) Application rates:
(a) 1500 Ibs per ac - Wood Fiber Mulch @ $150 per ton
(b) 15 Ibs per 1000 sq. ft - Fertilizer 11:8:4 @ $72 per ton
(c) 200 Ibs per ac - Seed 75% Rye & 25% Barley @ $26 per cwt
(d) 1 Ib per 100 sq. ft - Methyl Bromide (if required @ 4
-------
Rental rate: $20 per hr
Transport cost: $100 per job
(5) Labor conditions:
(a) Employment on one day minimum basis
(b) Overtime @ 150% of dayshift hourly rate
(c) Above operator wages include fringe benefits
(6) Move-in and move-out allowances
Above 5 ac - 2 days of Equipment and Labor
A brief study of several items of the estimate will aid in understanding
its applications. These will be numbered consecutively for ease of
reference, but the order of listing does not indicate relative degree of
importance.
(A) Fumigation to kill noxious weeds is not usually required, but
when it is, costs can increase six-fold.
(B) Costs per ac for a small plot, i.e. one ac, would be considerably
more because of the resulting relative importance of
move-in and move-out. Assuming that one day of time
would still be required for moving in and out and performing the
work, the cost per ac for a one-acre plot would increase to
about $858 for California from $427 per ac, without fumigation.
For jobs larger than 10 ac in size the cost per ac would decrease,
but not in the same proportion. Figure 1 is a graph showing
approximate variation in the per ac cost with increasing total
area per job.
(C) Material costs will vary primarily with seed and fertilizer re-
quirements, which depend greatly upon the site location and
client specifications as to the grass, or grass-flower, seed
mixtures desired. Seed costs can increase substantially if
exotic seeds, or seeds in short supply are specified. Fertilizer
requirements should not be arbitrarily specified, but should be
specified by a competent technician, taking into account the
vegetation to be grown and the available plant nutrients in the
soil. In many instances in Virginia, and in other places in the
United States where acid soils exist, lime must be added prior
to the fertilizing and seeding, or nutrients, especially
nitrogen, do not become readily available for plant growth. The
lime requirement should be specified by a technician. VJhen re-
quired, additional costs of from $50 to $140 per ac can be
expected, depending upon the amount of lime required and the
manner of application.
(D) Wage rates used are typical for prevailing union wages in the two
areas in late 1972. They include fringe benefits. Lower labor
rates are not uncommon.
15
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1000
900
800
700
iLl
cc
< 600
"*" 500
z
f- 400
to
o
0 300
200
»00
n
\
' \
_h
Hydromulching
(Also Known as Hydroseeding)
Area
Size Per Acre Costs in Dollars
(acre) Materials Labor Equipment Total
1 235 260 363
5 235 156 192
10 235 88 104
15 235 69 84
20 235 65 78
25 235 54 64
30 235 47 62
858
583
427
388
378
353
344
See Table 1 for Basic Specifications , wage and
overhead rates, etc.
^
'"H^Ji i i^
I 1 1 1 1 1 1 1 I 1 1 —
-
-
r^M
H-
10 15
SIZE OF AREA IN ACRES
25
30
Figure 1. Approximate Relationship Between Cost Per Acre, and Size
of Area for Wood Fiber Mulch, Fertilizer, and Seeding,
Typical for San Francisco Bay Area, California 1973
16
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(E) Employer extra labor payroll costs of 18 percent have been
added to all labor costs. (10% Workmen's Compensation, 6%
Social Security and 2% Unemployment Insurance.)
(F) An additional amount of approximately 11 percent of the labor
charges was added to total labor charges to cover general super-
vision by the contractors' superintendent or foreman.
(G) Contractor Overhead and Profit is a variable with every con-
tractor. The 25 percent figure used in these estimates repre-
sent what is considered to be a generally reasonable value for
the total of both items. 15 percent could represent general
overhead, and 10 percent could be considered profit but both
items depend upon the skill and experience of the contractor,
and the profit margin allowed in a contractor's estimate depends
also upon the amount and degree of competition, and his
anticipated work load.
(H) Per-acre costs as low as $200 for this practice may be mentioned
occasionally. Inspection of the cost elements in Table 1 leads
to the conclusion that such a unit cost would require an unusual
combination of factors, such as large job, short travel time, low
seeding and fertilizer requirements or costs, low wages, and tough
competition. Lower costs are desirable, but when they are
unusually low it is prudent to review specifications and procedures
to be certain that important data has not been omitted or changed.
(I) For quick approximate estimates, the total per-acre costs for
each major category, material, labor, and equipment, can be in-
creased or decreased by proportion as appropriate to the location,
specifications, and organization performing the work. More
accurate estimates may be prepared by reconstructing each element
of cost in the table.
5. RELATING CALIFORNIA COSTS TO COSTS IN OTHER AREAS
Prime reasons for summarizing costs in the three categories of labor,
materials and equipment are to facilitate updating of costs with time, and
to enable comparable costs for the same work in another geographic area
to be made more easily and more accurately.
Prevailing wage rates in almost any area of the nation can be obtained
from local contractor and labor organizations, the United States Department
of Labor (USDL), and state and local government public works agencies.
Equipment rental rates can be obtained from local rental agencies, from
the Annual Rental Compilation published by the Associated Equipment Dis-
tributors (Reference 4 ), or the Rental Rate Blue Book (Reference 77).
Agencies contemplating erosion control and correction work with their own
labor forces and equipment will have knowledge of most of the costs of
labor and equipment required. Materials prices for widely used construction
17
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TABLE 1
WOOD FIBER MULCH APPLICATION BY HYDROSEEDER
COST BREAKDOWN WITHOUT FUMIGATION
Fertilizer
15 Ibs 43560
1000 sq.ft X 2000 Ibs
Seed
California Data - 10 ac in California 10 ac in Virginia
See Specifications for Material Labor Equip ' Material Labor Equip
Virginia Modifications $ $ $ $ $ $
Fiber Mulch
III - »*> * 10 1-125 1-125
A-,,, -,n ooc -,£0
x $72 x 10 235 162
200 Ibs/ac x - ,. x 10 520 298
100 Ibs
Hydroseeder
2 men x 8 hr x $10 plus
overtime: 2 men x 2 hr x $15 220 176
Rental during transport time:
Hydroseeder 2 hr x $25 50 50
Rentals:
Hydroseeder 10 hr x $30 300 300
Move-in and Move-out
2 days x 2 men x 8 hr x $10/hr 320 256
2 days x 8 hr x $30/hr 480 480
Labor Supervision: 0.11 (220 + 320): 60 48
Subtotal 1,880 600 830 1,585 480 830
18% for Labor Overhead 108 86
25% for Overhead and Profit 470 177 207 396 142 207
Grand Total 2,350 885 1,037 1,981 708 1,037
Cost per ac 235 88 104 198 71 104
Overall Cost Per Ac 427 373
18
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TABLE la
WOOD FIBER MULCH APPLICATION BY HYDROSEEDER
ADDITIONAL COST FOR FUMIGATION
California Data 10 ac in California 10 ac in Virginia
See Specifications for Material Labor Equip Material Labor Equip
Virginia Modifications $ $ $ $ $ $
Fumigant: Methyl Bromide
4c/sq. ft x 43560 x 10 17,424 17,424
Labor
2 men x 8 hr x $10 plus
overtime: 2 x 2 hr x $15 220 176
Rental during transport time
Lump Sum 100 100
Rentals: 10 hr x $20 200 200
Move-In & Move-out
2 days x 8 hr x $20/hr 320 320
2 days x 2 men x 8 hr x $10/hr 320 256
Labor Supervision: 0.11 (220 + 320) 60 48
Subtotals 17,424 600 620 17,424 480 620
18% for Labor Overhead 108 86
25% for Overhead and Profit ^,356 177 155 4,356 142 155
Grand Total 21,780 885 775 21,780 708 775
Cost per ac 2,178 88 78 2,178 71 78
Additional Overall
Cost Per Ac 2,344 2,327
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materials, such as cement, steel, lumber and ready-mixed concrete, are
published frequently by local construction trade publications. However,
it should be noted that prices and rates for some of the materials and
equipment used in erosion control work are not published in most of the
references mentioned in this section. This is because of the relatively
limited amount of such work as compared to other types of construction
work. Local suppliers can furnish current costs of materials but costs
of special equipment, such as a Hydromulcher (Hydroseeder), must be
obtained from a dealer or rental agency.
Conversion of equipment purchase costs to daily rental rates involves
estimation of depreciation, interest, taxes and insurance (if any), fuel,
maintenance, and repairs. This is a time consuming process, but is neces-
sary to develop rental rates when none are available otherwise. Once
obtained or developed, direct use of rental rates is much more convenient.
Many contractors, and even government public works bodies, have calculated
job rental rates for equipment owned by them, for ease in accounting and
job estimating. In this report, equipment costs do not include operators
as operators are considered under labor costs, and must be identified
separately
As has been mentioned in Item I, costs for any particular area can be
estimated quickly by increasing or decreasing costs shown in this report by
the applicable rates for the local area and specifications. An example of
how this can be done is using the Wood Fiber Mulching data from Table 1,
for the Standard Practice, no fumigation.
For example, assume that the basic labor costs are $6.50 per hr rather than
the rate of $10 per hr as shown for California. The new total cost for
labor would be
x $885 = $575
instead of the $885. The decrease in per acre cost for labor would be
6-50 x $88 = $31
Similar proportionate calculations can be made for differences in materials
and equipment costs. Assuming no changes in the latter costs, the new cost
per ac would be
$427 - $31 = $396 per ac
There are several indices published periodically by private companies or
governmental agencies which are used by the construction industry and others
to follow construction cost trends. Engineering News-Record magazine, as
an example, publishes weekly selected lists of the costs of construction
materials and labor in approximately 30 major cities around the United
States, and both a Construction and a Building Cost Index. The Construc-
tion Cost Index represents a fixed mix of materials and labor:
20
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200 hr of common labor; 25 cwt structural steel shapes, millprice;
22.56 cwt (6 bbl) of Portland cement and 1,088 board-ft of 2x4 square-
four-side (S4S) lumber. It does not include equipment costs. The
materials-labor-equipment mixes for representative erosion control
practices are summarized in the following section of this report. These
mixes differ from the Construction Cost Index mix. Hence, while the
ENR Construction Cost Index may give an indication of trends in the cost
of erosion control work, use of local material, labor, and equipment
costs to update costs given in this report will give more accurate
results.
21
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SECTION V
EROSION AND SEDIMENT CONTROL COSTS
1. INTRODUCTION
Cost estimates for a number of different types of erosion control
measures have been prepared, basically using procedures and formats
similar to those previously outlined in Section IV. Most of these
measures are described, including numerous photographs and sketches,
in the publication "Guidelines for Erosion and Sediment Control Planning
and Implementation" (Reference 120).
Cost estimates are presented in this portion of the report for the
California and Virginia areas, together with brief description of the
control measures and their purposes. Details of each estimate, based
on data from the San Francisco B.ay Area of California, are presented in
Appendix A, with costs divided into materials, labor, and equipment
categories. Complete information on the practices is given in the
previously mentioned Guidelines and the reader should refer to them for
a full discussion of site evaluation, planning, and selection of
effective erosion control measures, and procedures for implementation
of the designs and plans.
Whereas the Guidelines present technical information on 42 sediment and
erosion control products, practices, and techniques, this report presents
cost estimates for 25 such items, covering a range of types and sizes.
The objective herein is to provide sufficient cost data, including some
variation in size of jobs, to enable reasonable cost estimates to be
made of the cost of retaining sediment on construction sites. Attempts
were made to limit the estimates to reasonably economic practices which
could serve as a useful basis of comparison
The use of a particular brand-name or proprietary product in the cost
estimate does not constitute any endorsement of the product, nor does
it signify that it is the best product to use for that particular
practice. In most instances, there is more than one alternative which
could be substituted. The economic comparison of competitive products
for a particular practice must be performed for specific installations,
conditions, and requirements, and is much too detailed a process for
inclusion in this report.
2. CONTROL STRUCTURES
A. Check Dams
Check dams are small structures constructed in gullies or other small
watercourses. Made of concrete, masonry, rock, rock and earth, metal,
wood, or other erosion-resistant materials, check dams reduce or prevent
erosion by reducing velocities, promoting deposition of sediment, and
stabilizing channel grades. Figures 2, 3, and 4 illustrate several
types of check dams.
23
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Figure 2. Small Rock Riprap Check Dams, with Gabion
Sidewalls (Reference 120)
24
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Existing
Ground line
TYPICAL SECTION CHECK DAM
Ctntral overflow
••ction
VERTICAL SECTION THROUGH CENTER
Figure 3. Typical Grouted Rock Riprap Check Dam (Courtesy of
Food & Agriculture Organization of the United Nations)
25
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Figure 4. Concrete Check Dam with Energy Dissipator (Reference 120)
26
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Cost Estimates- Check Dams
Cost estimates have been made for three types of check dams. The results
are summarized below:
GRAVEL AND EARTH CHECK DAM
Very small, low dams, with 1 ft crest width, 2:1 downstream slope, and
4:1 upstream slope. Hand labor.
Unit costs given in $ per cubic foot (cf) of total (gravel and earth) fill.
Size California Virginia
1 ft high, 5 ft avg width, total volume = 19cf
Total cost $ 35
Unit cost/cf 1.84
1.5 ft high, 10 ft avg width, total volume = 85cf
Total cost 146
Unit cost/cf 1.72
2 ft high, 15 ft avg width, total volume = 225cf
Total cost 187
Unit cost/cf .83
GROUTED ROCK RIPRAP CHECK DAM
Small low dam, with hand-placed grouted riprap masonry downstream face.
See accompanying sketch (Figure 3) for typical installation.
Unit costs given per cubic foot (cf) of masonry, which is the principal
cost item.
Size
2 ft high, 5 ft avg width, cf of masonry = 56
Total cost $ 392 $ 335
Unit cost/cf 7.00 5.99
3 ft high, 10 ft avg width, cf of masonry = 131
Total cost 879 756
Unit cost/cf 6.71 5.74
4 ft high, 15 ft avg width, cf masonry = 210
Total cost 1,428 1,237
Unit cost/cf 6.80 5.87
5 ft high, 20 ft avg width, cf masonry = 300
Total cost 2,451 2,088
Unit cost/cf 8.17 6.96
27
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CONCRETE CHECK DAM
Small structure constructed of reinforced concrete (Figure 4).
Unit costs are per cubic yard (cy) of reinforced concrete on drawings.
Size California Virginia
2 ft 4 in. high x 5 ft wide x 4 ft long
Volume reinforced concrete = 1.9cy
Total cost $ 1,136 $ 1,027
Unit cost/cy 598 541
5 ft 6 in. high x 9 ft 8 in. wide x 8 ft long
Volume reinforced concrete = 10.8cy
Total cost 3,108 2,802
Unit cost/cy 288 259
5 ft high x 17 ft 6 in. wide x 14 ft long
Volume reinforced concrete = 17.8cy
Total cost 4,647 4,150
Unit cost/cy 261 233
7 ft high x 20 ft wide x 20 ft long
Volume reinforced concrete = 33.0cy
Total cost 7,154 6,430
Unit cost/cy 217 195
B. Chutes/Flumes
Chutes and flumes are channels constructed of concrete or comparable mate-
rial that are designed to conduct runoff downslope from one elevation to
another without erosion of the slope. They may be installed as temporary, in
interim, or permanent structures downslopes where concentrated runoff would
cause slope erosion. Figure 5 illustrates a typical chute/flume.
28
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Sect. AA
Figure 5. Chute/Flume (Reference 120)
29
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Cost Estimate - Concrete Flume
A cost estimate was made for a concrete chute constructed of pneumatic
concrete reinforced with wire mesh, and without energy dissipating blocks,
as follows:
Dimensions of Flume:
Bottom width = 3 ft
Depth = 1 ft
Side Slopes =1:1
Concrete
thickness = 3 in.
Length = 40 ft
Total Cost:
Unit Cost:
Per lineal ft length
Per sq ft of concrete
California
$1,298
$ 32.45
5.40
Virginia
$ 1,134
28.35
4.72
C. Diversion Dikes
Diversion dikes are small temporary ridges of soil (Figure 6) con-
structed at the top of cut or fill slopes to divert overland flow from
small areas away from newly-constructed, unstabilized, or unprotected
slopes. They normally are used as temporary or interim measures, but are
sometimes appropriate as permanent installations.
' 1.5'
• 2:1 Slope or Flatter
CROSS SECTION
Outlet Onto
Stabilized Area
Upslope Toev
Positive Grade,
V
Min.-
AA A A A
Y Y V
t
Cut or Fill Slope
General Notes:
PLAN VIEW '
a. Drawings not to scale.
b. Outlet to discharge into stabilized area.
Figure 6. Diversion Dike (Reference 120)
30
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Cost Estimate - Diversion Dike
A cost estimate was prepared for a well-compacted embankment with final
dimensions as shown on Figure 6. It should be noted that many diversion
dikes are not compacted as much as really needed (some are constructed
more like level spreaders) and costs per lineal ft are less than the
estimates shown here. The following estimate was prepared for a dike
43 ft long, with 15 cy of earth as final compacted embankment:
Cost per lineal ft of dike =
Cost per cy of embankment =
California Virginia
$4.51
12.93
$ 3.70
10.65
D. Erosion Checks
Erosion checks (Figures 7 and 8) are porous, mat-like materials installed
in slit trenches oriented perpendicular to-the direction of flow in
ditches or swales. They prevent the formation of rills and gullies by
permitting subsurface water migration without the removal of soil
particles.
Figure 7. Fiber Glass Erosion Check (Reference 120)
31'
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SECT.-AA
TsiO SCAU-E
1. Cutaway of fiber glass installation in bottom of trench.
2. Cutaway of fiber glass installation in trench with spoil pile.
3. Trench with fiber glass erosion check installed.
4. Cap strip of blanketing material over completed erosion check.
Figure 8. Erosion Check (Reference 120)
32
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Cost Estimate - Erosion Check
Cost estimates were made using jute mesh rather than fiber glass
mesh. The procedure for either type of material is the same and
the primary variable would be the material, which, in the case of
jute mesh, is a very small part of the cost, the greater portion
being the cost of labor.
The following estimate was prepared for 152 lineal ft of jute mesh,
which is approximately the quantity two laborers can excavate and
place in one day under average conditions, as follows:
Total Cost
Cost per lineal ft
California
$ 522
3.43
Virginia
$ 403
2.65
E. Filter Berms
Filter berms (Figure 9 and 10) are temporary ridges of gravel or crushed
rock constructed across a graded right-of-way to retain runoff while at
the same time allowing construction traffic to proceed along the right-
of-way. They are used primarily across graded rights-of-way that are
subject to vehicular traffic, but also are applicable for use in drainage
ditches prior to roadway paving and establishment of permanent ground
cover.
Figure 9. Filter Berm - Installed (Reference 120)
33
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3'-5'
Flow
Direction
Graded
PLAN
Graded R. O. W. i
F.
Figure 10. Filter Berm - Cross Section (Reference 120)
Cost Estimate - Filter Berm
An estimate for a berm having about 30 cy of gravel, and being about
58 ft long is as follows:
Total cost
Unit cost, per lineal ft
Unit cost, per cy
California
$319
5.50
10.63
Virginia
$296
5.11
9.87
Filter Inlets
Filter inlets (Figures 11 and 12) are temporary filters of gravel or
crushed rock constructed at storm sewer curb inlet structures. Their
purpose is to retain sediment on-site by slightly retarding and filtering
storm runoff before it enters the storm sewer system.
34
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Figure 11. Filter inlet - Installed (Reference 120)
Figure 12. Filter Inlets - Installed (Reference 120)
35
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Cost Estimate - Filter Inlet
If access by gravel trucks is possible, costs for filter inlets will
be approximately the same per cubic yard as for filter berms. If
material must be retransported by a front-end loader, costs will be
considerably higher. The following costs include gravel, labor, and
equipment:
Access by truck, unit cost per cy
If rehandled by front-end loader,
unit cost per cy
California
$ 10.63
$ 16.00
Virginia
$ 9.87
$ 15.30
G. Flexible Downdrains
Flexible downdrains are flexible conduits (Figures 13 and 14) of heavy
duty fabric or other materials, to conduct storm runoff from one elevation
to another without erosion of the slope. Th'ey are used as temporary or
interim structures down slopes where concentrated runoff would cause ex-
cessive slope erosion.
Cost Estimate - Flexible Downdrain
Estimates were made for 300 lineal feet of flexible downdrain, with
the connection assumed to be to a culvert at the upper end. Costs
for riprap or other energy dissipation at outlet were not included,
in the following estimates:
California
Virginia
Total costs, 300 lineal ft of
downdrain, in place
Unit cost per lineal ft
$ 2,203 $ 2,180
7.34 7.26
36
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Figure 13. Flexible Downdrain - Isometric (Reference 120)
Figure 14. Flexible Downdrain - Installed (Reference 120)
37
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H. Flexible Erosion Control Mats
Flexible erosion control mats (Figures 15, 16, and 17) are special flexible
fabric forms into which fluid mortar is injected under pressure, using
special techniques, after the forms are in place. In erosion control work
they are used for channel lining, revetments, levee facings, shoreline
stabilization, and check dams. They can be placed above or below water
surfaces, and are adaptable to almost any type of soil conditions.
Cost Estimate - Flexible Erosion Control Mat
The following estimate was made for a channel 25 ft wide and 0.25 mi.
long (i.e. 33,000 sq. ft of flexible mat required):
Total cost
Unit cost, per sq. ft
California
$38,824
1.18
Virginia
$36,600
1.11
Figure 15. Schematic of Flexible Mat Subsequent to Grouting
(Courtesy of VSL Corporation)
38
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Figure 16. Installation of Flexible Erosion Control Mats in a
Drainage Canal with High Ground Water Table (Courtesy
of VSL Corporation)
Figure 17. Detail of Installed Flexible Erosion Control Mats
(Courtesy of VSL Corporation)
39
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I.
Gabions
Gabions are large, multi—celled, rectangular wire mesh boxes (Figures 18
and 19), filled with rock. Individual gabions serve as building blocks
which when properly wired together, form monolithic, yet flexible,
structures and mats. They are used in channels, revetments, abutments,
check dams, retaining walls, levee facings, and other erosion control
structures.
Cost Estimates - Gabions
Estimates were made for 3 sizes of small jobs, using gabions 1 ft
deep, as follows:
California
Virginia
Unit costs are per sq. yd of
surface area
10 sq. yd
100 sq. yd
1000 sq. yd
$ 30.10
15.49
12.67
$ 24.82
13.85
11.35
Figure 18. Gabions - Channel Bank Protection (Reference 120)
40
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J. Interceptor Dikes
Interceptor dikes are temporary ridges of compacted soil (Figures 20 and
21), constructed across a graded right-of-way. They reduce erosion by
intercepting storm runoff and diverting it to temporary outlets where
it can be disposed of with minimal erosion. Interceptor dikes are
normally used across graded rights—of-way that are not subject to vehicular
traffic.
Figure 19. Gabions - Channel Lining, Check Dam, and Bank
Protection (Reference 120)
•2 = 1 or flatter Slopes-
CROSS SECTION
1.5'
Kight-o£-Way
^•R.O. W.
:\ or Flatter
Slopes
^-Outlet onto Stabilized Area
PLAN VIEW
a. Drawings not to scale.
b. Top width may be widened, slopes may be flattened.
c. Outlet should function with minimal erosion.
Figure 20„ Interceptor Dike (Reference 120)
41
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Cost Estimate - Interceptor Dikes
The cost estimates for well-constructed diversion dikes, as presented
on page 31 are representative of the cost for interceptor dikes. In
many instances, for example along forest roads, a log with earth back-
fill can be placed at a much lower cost per lineal foot. Hence,
diversion dike costs are probably at a higher range of values.
Figure 21. Interceptor Dike - Installed (Reference 120)
K. Level Spreaders
Level spreaders are outlets constructed at zero grade across a slope where
concentrated runoff may be spread at nonerosive velocities, in the form of
sheet flow, over undisturbed areas stabilized by existing vegetation.
Figures 22 and 23 illustrate typical level spreaders.
Cost Estimates - Level Spreaders
The following estimates were made for small jobs for three lengths of
spreaders, constructed by bulldozer.
California Virginia
Length of level spreader:
15 ft Unit cost per lineal ft
44 ft Unit cost per lineal ft
78 ft Unit cost per lineal ft
$ 3.80
1.91
1.63
$ 3.16
1.57
1.36
42
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Undisturbed Soil
Stabilized by
Existing Vegetation
Drawing not to scale.
Figure 22. Level Spreader (Reference 120)
Figure 23. Small Diversions, Very Similar to Level Spreaders. If
Both lip and bed are constructed at zero grade these
would be level spreaders. (Reference 120)
43
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L. Sandbag Sediment Barriers
Sandbag sediment barriers are temporary barriers or diversions constructed
of sandbags. The barriers are built to retain sediment on-site by slowing
storm runoff and causing the deposition of sediment at the structure, and
are used at storm drain inlets, across minor swales and ditches, and for
other applications where the structure is of a temporary nature.
Cost Estimate - S-andbag Sediment Barrier
The following estimate was prepared for one day of sandbagging by
four laborers and a foreman, assuming that 180 bags would be filled
and placed in one day.
M.
180 bags, cost per sandbag
Sectional Downdrains
California
$3.10
Virginia
$ 2.44
Sectional downdrains (Figure 24) are prefabricated, sectional conduits of
half-round or third-round, pipe, corrugated metal, concrete, bitumized
fiber, asbestos cement, or other material. They conduct storm runoff
from one elevation to another without slope erosion, and are used as a
temporary, interim, or premanent structure on slopes where concentrated
runoff would cause excessive slope erosion.
Figure 24. Sectional Downdrain
44
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Cost Estimate - Sectional Downdrains
Two different lengths of 24 in.-diameter sectional downdrains were
considered. The cost estimates are as follows:
California Virginia
40 ft length Total Cost $582 $ 474
Unit cost per
lineal ft 14.55 11.85
234 ft Total Cost 2,555 2,136
Unit cost per
lineal ft 10.91 9.13
N. Sediment Retention Basins
Sediment retention basins are storage areas behind dams or barriers and
are constructed for the primary purpose of trapping and storing sediment
and debris produced by storm runoff from tributary watersheds. They
sometimes are referred to as Debris Basins, especially in the southwestern
United States. While in a strict technical sense the term "basin" applies
only to the storage area, in common usage the term is understood to in-
clude also the dam or barrier. As temporary measures they are used across
channels and drainageways that are on, or adjacent to, construction sites,
to trap and retain sediment generated during on-site construction activities.
In many instances they are also used on a longer-term basis to protect
downstream channels and properties from annual threats of unwanted sediment
and debris carried by storm runoff. Illustrative examples of sediment
retention basins are shown on Figures 25, 26, and 27.
Cost Estimates - Sediment Retention Basins
Three cases of sediment retention basins were estimated. Well-designed
and engineered structures 6 ft to 8 ft in height were assumed. Land
costs are not included in the following tabulation of Unit costs.
California Virginia
6 ft high, 30 ft avg length To
Total Cost $ 1,833 $ 1,516
Unit cost per cy 13.78 11.40
7 ft high, 30 ft avg length
Total cost 2,189 1,850
Unit cost per cy 12.88 10.90
8 ft high, 40 ft avg length
Total cost 2,996 2,560
Unit cost per cy 10.51 8.99
45
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-p-
o\
Figure 25. Small Sediment Basin with Outlet Pipe Discharging on Energy
Dissipator to Prevent Erosion at Discharge End. (Revised
from California Division of Soil Conservation, Reference 92.)
-------
Gravel Cone
Collar
Free outlet
Figure 26.
92, Figure No. 35.)
-------
Figure
27.
Sediment Retention Basin
- SM11, ^ss Than 1/4-Aore in Size
(Reference
120)
Barriers
barriers that ^^^Ttorm runoff. They are used^at
"swales and ditch
Q-r inlet 7 bales/inlet,
Storm sewer in-Let, / letsyday
Straw Bale Barrier
Total cost/inlet
Cost/bale
$ 55.00
7.86
7.86/bale
plus 10.44/weir
46.34
6.62
6.62/bale
8.99/weir
-------
Gutter
Storm sewer structure
Anchor with two stakes
driven into the ground
Figure 28. Temporary Barrier of Hay Bales to Prevent Sediment-laden
Water from Entering Incomplete Storm Sewer System. (Re-
vised from Fairfax County, Reference 92, Figure 17.)
49
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Flow
Bales of straw staked down
Provide sand and gravel filter outlet
at lower area along with straw bales
Front view
Figure 29. Semi-pervious Barrier of Hay Bales with More Pervious
Embankment of Sand and Gravel for Spillway. (Revised
from Fairfax County, Reference 92, Figure 31.)
50
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"'* s^.t>; » **,•?'
j ^ f s _ ^ ^ir' JT i. ^^P*" , 1 «.
Figure 30. Straw Bales at Storm Drain Inlet (Reference 120)
Figure 31. Straw Bale Structure on Property Line (Reference 120)
51
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3. FIBER MULCHES, MULCH BLANKETS, NETTINGS, AND SODDING
A detailed cost estimate for seeding, fertilizing, and providing a wood
fiber mulch by a hydroseeder has been presented previously (Section IV,
Table 1). Estimates for several other representative similar practices
were prepared and are summarized in Table 2. Explanations of all but two
methods are given on the following pages. These explanations were taken
from Reference 120. Technical instructions for the sodding practices are
not included, although the detailed cost sheets in Appendix A provide
information on the requirements.
Although costs are given on a per ac basis for all practices in this
protion of the report, they are not always directly comparable. For
example, on very steep slopes wood fiber mulch would not provide good
protection, while excelsior would do so, even though it is more expensive.
Generally, more expensive practices are required on the steeper slopes.
In making a selection for a particular site and situation, the economic
life of the practice and its maintenance costs must be considered, as
well as the initial installation costs, the application requirements for
a particular soil, slope, or climate, and the desired end result. There
are so many variables to be considered that only broad general conclusions
should be drawn from the unit costs presented herein.
Detailed cost estimates showing costs of material, labor, and equipment
are provided in Tables A-l through A-27, Appendix A.
TABLE 2
SUMMARY OF REPRESENTATIVE COSTS FOR FIBER MULCHES, BLANKETS, ETC.
Practice or Method
Cost per Ac of Area
California Virginia
Excelsior Mats
Jute Netting
Straw or Hay applied by blower
Woodchips, 3 in. cover unseeded
Woodchips, 3/4 in. cover
Wood Fiber Mulch by Hydroseeder
Sod, 4 in. sq plugs
Sod Blankets
Chemical Soil Stabilizer
$12,200
7,700
1,200
8,000
3,100
430
11,300
14,800
1,300
$10,200
6,700
1,100
7,200
2,800
370
10,300
14,300
1,250
Notes: (1) All of the above estimates include fertilizer and seed neces-
sary to provide a vegetative cover, except the 3 in. deep
woodchip cover estimate. Seed, of course, is not required for
sodding. See detailed estimates in Appendix A for application
rates.
(2) Costs are not directly comparable. See text. Terrain, use of
land, climate, time of year, degree of protection desired, and
other factors must be considered to make an economic comparative
evaluation for each specific situation
52
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A. Excelsior Blankets
Excelsior blankets (Figure 32) consist of machine-produced mats of curled
wood excelsior of 80 percent eight-inch or longer fiber length. The top
side of each blanket is covered with a 3 in. x 1 in. weave of twisted
Kraft paper, biodegradable plastic mesh, or similar material, that has a
high wet strength. These blankets protect the soil from the energy of
falling raindrops and overland flow, conserve soil moisture, and serve
as insulators against intense solar radiation. In general, the blankets
are rolled out on the seeded area to be protected and are stapled into
place. Suggested staple application rate, under normal conditions, is
five staples per six linear feet of blanket. The fact that the blankets
are secured to the soil by metal staples make this product resistant to
erosion by concentrated storm runoff. The blankets can, therefore, be
used in critical areas such as swales, ditches, steep slopes, highly
erodible soil, etc.
Figure 32. Excelsior Blanket and Staple (Reference 120)
B. Jute Netting
Jute netting (Figure 33) consists of a heavy woven mesh, Of undyed and
unbleached twisted jute fibers of rugged construction. The netting can
be treated to be smolder resistant. It is commonly available in individual
rolls, about 4 ft wide and is used in the establishment of vegetation in
critical areas. As a mulching product, it dissipates the energy of falling
rain drops, and overland flow, conserves soil moisture, and serves as an
53
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insulator against intense solar radiation. The thick strands and heavy
weave enable this product to withstand the higher flow velocities associ-
ated with critical swales, ditches, median strips, etc. Seeding may be
done before and after installation. The netting is unrolled over the soils
to be protected with the edges overlapped, and stapled to the soil beneath.
The upstream end of each strip is buried at least four inches deep and
reinforced by a row of staples about four inches downhill from the trench.
Figure 33. Jute Netting Being Installed (Reference 120)
C. Straw or Hay
Straw or hay often are used as a mulch product (Figure 24). In this capa-
city they dissipate the energy of falling raindrops and overland flow, con-
serve soil moisture, and serve as an insulator against intense solar
radiation. They are used on newly-seeded areas, and car. be used also as
a temporary mulching measure to protect bare soil areas that have not been
seeded. The latter practice is applicable only for relatively short
periods of time or until the next seeding season has bee'n reached.
Straw or hay mulch can be applied by hand spreading (shg.king) on small
plots and by mulch blowing equipment on larger areas. It is applied at
rates of from one to two tons per acre. (In California four tons total
in two applications is a common procedure for highway erosion protection).
Straw and hay mulch should be tacked to insure against excessive losses
by wind and water. Liquid and emulsified asphalt are the most commonly
used mulch tacks. However, other chemicals and netting products are
available for use as mulch tacks. Mulch anchoring tools can also be
utilized to anchor straw and hay. This equipment consists of a series of
54
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notched discs which punch and anchor the mulch material into the soil.
Soil must be moist, free of stones, and loose enough to permit disc
penetration to a depth of two to three inches if this mulch anchoring
technique is to perform in a satisfactory manner.
One advantage of this type of mulch is that it is well-adapted to later
overseeding, even up to six months later. Thus mulching can be done
immediately after fine grading is completed, with seeding delayed until
the most appropriate time. Important present disadvantages are the high
cost for labor and/or equipment and the greater length of time required
for placement, as compared to hydromulching.
Figure 34. Large Straw Mulching Operation (Reference 120)
D. Woodchips
Chips of wood are produced by processing tree trunks, limbs, branches,
etc., in woodchipping machines. The chips are placed back on the site
from which they originate, or are placed in trucks for transport to other
sites where they are spread for use. Chips are used as a temporary or
interim erosion control technique to protect bare soil areas that have
not been seeded. They are also used as a mulch product on newly-seeded
areas. In this capacity, they conserve soil moisture during dry periods,
dissipate energy from falling raindrops, serve as insulators against
intense solar insolation, and reduce erosion caused by overland sheet
flow. Woodchips may also be used on pathways and to reinforce leaf mold,
duff, etc., in wooded areas that are to be preserved.
55
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As a temporary technique on unseeded areas, the chips are placed by
machine or spread by hand tools. Application rates range from 4 to 6 cf
of woodchips per 100 sq. ft of area. This application rate is ample to
protect bare soil under normal conditions. If intensive foot or vehicle
traffic is anticipated, this rate may be increased to the point where
woodchip depths of several inches are attained. This very heavy applica-
tion rate is particularly applicable to yard areas adjacent to homes under
construction if autos and light trucks drive and park in the yard area.
As a mulching product on newly-seeded areas, woodchips may be placed by
machine blower or by hand from stockpiles (Figure 35). Application rates
of 60 to 100 cy per ac are commonly recommended. Mulching with woodchips
has proven successful when used with late fall seeding operations that
require protection over winter. Experimental work is needed to perfect
seed mixtures for this type of operation. However, the wood chip mulch
has proven to be satisfactory under these conditions.
Figure 35, Spreading Wood Chips on Homesites (Reference 120)
E. Wood Fiber Mulch
Wood fiber mulch is a natural, short fiber product, produced from clean,
whole wood chips. A nontoxic dye is used to color the irulch green in order
to aid visual metering in its application. It is evenly dispersed and
suspended when agitated in water, and when applied uniformly on the surface
of the soil, the fibers form an absorbent cover, allowing percolation of
water to the underlying soil.
56
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Wood fiber mulch contains no growth or germination-inhibiting factors.
In hydroseeder slurries, it is compatible with seed, lime, fertilizer,
etc.
Wood fiber mulch is specifically designed for use as a hydraulically
applied mulch that aids in the establishment of turf or other seeded
or sprigged ground covers. As a mulching product, it conserves soil mois-
ture, serves as an insulator against intense solar radiation, and dis-
sipates energy from falling raindrops.
Wood fiber should be applied by a hydromulching machine (also called
"hydroseeder") at rates of 1,000 to 1,500 Ibs per ac. It is introduced
into the slurry tank after the proportionate quantities of seed, ferti-
lizer, etc., have been introduced. The components are agitated into a
well-mixed slurry and are sprayed onto the sites or plots to be seeded.
Figures 36 and 37 are photographs of wood fiber mulch in place and during
application, respectively.
•V'/tdt.^lJ
Figure 36. Hydroseeder Applying Seed, Fertilizer, and Mulch on Cut-
Slope Adjacent to Newly-constructed Road (Spalding County,
Georgia, Courtesy SCS, Reference 92).
57
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Figure 37. Wood Fiber Mulch in Place (Close-up) (Reference 120)
F.
PETROSET'
'SB
PETROSET^SB is a chemical mulch or soil stabilizer. There are other types
manufactured by other companies which also have useful applications in
erosion control. Each site, situation, and chemical should be evaluated
in terms of the end results desired and the relative economics of the
alternatives. Figure 38 depicts the application of this iraterial.
PETROSET^ SB is a light tan colored oil in xrater emulsicn of high strength
rubber. It is free flowing and is water dispersible. The material is not
flammable and is not toxic to humans or animals. In erosion control work
it has the following uses:
(1) j^emporary Soil Stabilization - On denuded areas it penetrates the
soil and binds soil particles into a coherent mass that reduces
erosion by water.
(2) Chemical Mulch - On seeded areas it penetrates the soil and binds
soil particles into a coherent mass. Water and air movement into
the soil is maintained.
58
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(3) Mulch Tack - Binds natural and synthetic fiber mulches together
and thereby reduces loss of mulch due to removal by wind and
rain.
Numerous dilution ratios (i.e., parts of PETROSET^SB to parts of water)
and application rates (also, spreading rates) have been developed by the
manufacturer for different soil textures, desired penetrations, and
intended usages. Practically any spraying equipment capable of delivering
the desired quantity of dilute PETROSET® SB can be used. Distributor
trucks with calibrated spreader bars, as well as hydroseeding equipment
are suitable for applying the chemical. Thirty minutes after application
this product has cured enough to perform satisfactorily and will not adhere
to shoes.
Figure 38. Chemical Soil Stabilizer Being Applied to an Area that will
be Seeded at a Later Date (Reference 120)
59
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SECTION VI
SEDIMENT REMOVAL METHODS AND COSTS
Cost estimates were made for several typical situations where sediment,
which has been transported and deposited, must be removed. The basis of
making these estimates generally was similar to that used for preparing
the cost estimates for erosion control measures. These will be discussed
and presented in subsequent paragraphs,
1. EXCAVATION OR SIMILAR METHODS OF REMOVAL
A. Street Removal
These costs apply wherever machinery, trucks, and men have ready access
to the unwanted sediment deposits which could have been deposited in
streets, playgrounds, parks, or similar open areas as shown by Figures
39 and 40. They represent the lower end of the range of sediment re-
moval costs. Should access be difficult, higher costs would result.
An operation of one day is assumed; and unit costs for additional days
of work should not be significantly less. Work under emergency condi-
tions, with overtime labor rates and premium equipment rental rates,
will be more expensive. Appendix A presents details of the estimate.
Overall costs of about $8.00 per cy in California, and $6.60 per cy in
Virginia, are indicated.
B. Basement Removal
In this situation the sediment must be removed from the basement first
by hand - loading into wheelbarrows. The wheelbarrows dump onto a small
conveyor, which carries the load to the street or yard where a front-end
loader places it in a dump truck. Unit costs are very high0
This kind of work often is performed by owners with volunteers or low
cash-cost labor, and equipment furnished in total or in part by govern-
mental agencies. In such cases, the out-of-pocket expenditures would be
less, but the true cost to the community would more nearly be represented
by the figures developed by using normal labor and equipment rental rates,
Details of the estimate are in Appendix A.
Overall costs of $77.00 per cy in California, and $65.00 per cy in
Virginia, have been derived.
61
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Figure ,39. Erosion and Deposition of Sediment in Streets.
Bowie, Maryland (Courtesy SCS, Reference 92)
Figure 40. Deposition of Sediments from Erosion of Newly-construe ted
Athletic Field, Washington D.C. (Courtetsy SCS,
Reference 92)
62
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C» Storm Sewer Removal
When water with a heavy sediment load flows through storm sewers, in-
evitably silt deposits occur as the flow decreases. Because of the
possible range of degree-of-access difficulty there can be a wide range
of costs. Estimates were made for two methods; ->ne being conventional
use of small dragline buckets, and the other being a newer method utiliz-
ing hydro-flushing and vacuuming.
In the latter method, special equipment first rods a clogged storm sewer
using truck-supplied water under high pressure. As the debris is flushed
into a nearby manhole, a large truck-mounted vacuum line and reservoir
removes and stores the debris and water from the storm sewer line for
later disposal.
Cost details are presented in Appendix A» It will be seen that sewer
clean-out costs are very high, being around $144 per cy for the bucket-
line method in California, to an estimated $68 per cy for the hydro-
flush method. Virginia costs are estimated respectively at $122 per cy
and $62 per cy.
D. Reservoir and Sediment Basin Removal
Figures 41, 42, 43 illustrate the varieties of sediment basins.
Possibly the greatest amount of data available on costs of sediment
removal from reservoirs and debris basins has been compiled for the
numerous reservoirs and basins along the foot of the San Gabriel
Mountains in Southern California by the Los Angeles County Flood Control
District (LACFCD). While the deposits in these facilities may be gen-
erally coarser than in many other reservoirs in the United States, the
problems of excavation, hauling, and disposal are not dissimilar. The
costs therefore, should be representative.
Excavation normally is by front-end loaders or power shovels. The
material is carried away, by dump trucks or by belt conveyor systems,
to disposal areas located varying distances from the site of excavation.
Some of the disposal areas are adjacent, with very short haul distances,
while others are six miles or more away. The work has been performed
by Force Account and by contractors. At times the material excavated
has been used for fill on another construction job, rather than being
temporarily, at least, an item of waste. Because of the many variables
affecting the cost in any particular instance and the great differences
in amounts of material which might be required to be moved, ranging from
a few hundred cubic yards to millions of cubic yards, detailed cost
estimates are not being presented.
The experience in handling sediment and debris from more that 79 debris
basins and 14 reservoirs, however, does provide some useful cost figures.
They are summarized in the following series of numbered statements.
63
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(1) A good average unit: weight for the sediment and debris deposits
in the LACFCD area is about 1.5 tons per cy. (Note: This is a
higher average density than found in most reservoirs. The nor-
mal range of dry weight in situ densities is from 30 to 100 Ibs
per cf, equivalent to about 0.4 to 1.35 tons per cy).
(2) The average rate of sediment deposits in 14 reservoirs having a
total uncontrolled drainage area of around 400 sq mi, over a
number of seasons varying from 33 to 51 yrs, was about 4,900 cy
per sq. mi, or about 11.5 tons per ac, per season. The low
seasonal average was 2,000 cy per sq. mi and the high average
was 7,000 cy per sq. mi. (4.7 tons per ac and 16.4 tons per ac,
respectively). Storage capacities ranged from 150 ac ft to
53,000 ac ft.
(3) During the period 1967-70, removal costs from reservoirs ranged
from $0.90 per cy to $2.40 per cy. The lower unit costs gen-
erally were for quantities of 1 to 9 million cy of material,
although one job of 350,000 cy had a low cost. The higher cost
jobs involved about 750,000 cy each. Both conveyor and trucks
were used for hauling, and unit costs at both extremes were
noted for each method.
(4) Debris basins are much smaller than most reservoirs. Their
uncontrolled drainage areas varied from 0.03 sq. mi to almost
10 sq. mi. Maximum seasonal debris production generally ranged
from 3,000 cy per sq. mi to 223,000 cy per sq. mi with many
maximum values being in the 30,000 to 60,000 cy sq. mi range.
(5) Debris basin cleanout costs range from about $0.90 per cy to
$6.60 per cy, with an average of around $2.25 per cy in Fiscal
1968-69. Costs in 1972 could be expected to be higher, due to
increases in labor and equipment costs.
(6). Detailed cost breakdowns for 1968-69 debris basin cleanout jobs
performed by Force Account, revealed the following for one series
of jobs involving about 31 basins.
Total cy removed = 1,435,365
Cost Breakdown-Labor = 19.5%
Equipment = 78.5%
Material = 1.5%
Misc. = 0.5%
Total 100% = $2,632,700
Plus overhead
and contingencies = 20% = 562,500
$3,159,200 Total
Cost
Cost per cy removed = $2.20
64
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Figure 41. Small Sediment Basin with Trapped Materials (Courtesy
SCS, Reference 92)
Figure 42. Accumulated Sediment Being Removed from Small Basin
(Courtesy SCS, Reference 92)
65
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Figure 43. Large Well-designed Sediment Basin in Construction Site Area
for the Malibu Campus of Pepperdine University, California
(Courtesy Los Angeles County Flood Control District, Re-
ference 92)
66
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2. REMOVAL BY DREDGING
Much of the sediment carried by streams settles in lakes, bays, estuaries,
and other waterways, where it produces undesired effects. The most ef-
ficient means of removing this unwanted sediment is by dredging.
Unit dredging costs range in quoted values from $0.10 per cy to $8.00 per
cy. The cost depends greatly upon the amount of material to be dredged,
but even more upon the transport costs for moving the dredged material
to a suitable disposal area.
Cutter-Suction dredges can range in size from small dredges having a
capital cost of around $150,000, to large dredges, costing $1,000,000
or more. Large Hopper Dredges, almost exclusively owned and operated by
the U.S. Army Corps of Engineers in this country, have cost as much as
$17,000,000. The small dredges yield the highest unit cost per cy of
material moved. The general rule is: the larger the dredge, the lower
the unit cost, for the same delivery distance.
However, the larger the dredge the greater the quantity of material which
must be moved to keep the costs low. Greatest efficiencies occur when
the dredges can be operated around-the-clock.
Material dredged by a Cutter-Suction dredge normally is piped through a
semi-flexible pipeline to a nearby disposal area. Fine sands can be
pumped as far as 15,000 ft but 3,000 to 4,000 ft is a long pumping dis-
tance for gravels. Assuming fine sands are pumped about 4,000 ft, the
following approximate dredging costs would result, in the San Francisco
Bay Area:
Small Dredge $0.35 - $0.45 per cy
Capacity = 200 cy per hr = 4,600 cy per day
Medium Dredge $0.30 - $0.35 per cy
Capacity = 400 cy per hr = 9,200 cy per day
Large Dredge $0.15 - $0.20 per cy
Capacity = 1500 cy per hr = 34,500 cy per day
The above costs assume 23 production hours in a 24-hour day.
Labor costs represent from 75 to 95 percent of the total costs. Because
of differences in labor costs, similar dredging costs in the Virginia area
could be about 15 to 20 percent lower. Small dredges require one man on
the dredge and a pipeline crew of four men. The larger of the dredges
noted above requires a dredge and boat crew of seven, plus 6 to 8 addi-
tional men on the pipeline and 2 men at the disposal area. These require-
ments are for an 8-hour shift.
67
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Transport costs for greater distances increase rapidly. When the dis-
tances are too great for pumping, the material is carried by barges or
in Hopper Dredges. For example, transportation of dredged material from
San Francisco Bay to points 30 miles at sea adds from $6.00 to $7.00 per
cy to the dredging costs.
With increased limitations on, or elimination of, disposal sites near
dredging locations, overall dredging costs can be expected to increase.
It is important to note that conversion of the foregoing dredging costs
per cy of material to costs per ton of dredged material required careful
calculations. The weight of the solids in a cy of sediment in situ varies
greatly, depending upon many variables. The usual density range of bottom
sediments in reservoirs, bays and estuaries is from 30 to 90 Ibs per cu
ft. dry weight. Where deposits include considerable amounts of sand and
gravel, densities of 100 to 120 Ibs per cu ft. are comrnDn, and even higher
densities are sometimes encountered.
To further complicate the situation, in situ densities often are expressed
as weight including water in the voids and also expressed on a dry weight
basis. Unfortunately, many articles in the technical literature do not
indicate clearly which method of expressing in situ densities is presented,
and the reader somehow must make certain of the basis used, or risk errors
of as much as 300 percent in volume and weight calculations, in some
instances.
Dredge manufacturers usually express production rates in cy per hr. where
this volume represents the in situ volume of the material prior to ex-
cavation. Dredged material usually bulks (increases in volume) after
excavation and occupies more space than originally occupied in situ.
3. WATER TREATMENT COSTS
The following water treatment parameters are identified as the probable
major treatment costs versus suspended solids removal from raw water
supplies.
(1) Degree of treatment required.
(2) Amount of chemical additions required.
(3) Sludge disposal.
A. Required Treatment Level
Generally, surface waters used for domestic water supplies will be treated
by coagulation, sedimentation, and filtration. Treatment plants with
coagulation-sedimentation processes are capable of treating water with
a wide range of suspended solids content. If a reliable surface water
supply of low suspended solids is available, however, the treatment
system may consist of very simple rapid mix of an appropriate filter aid,
68
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filtration, and chlorination. Peak values of suspended solids in excess
of 10 to 15 mg/1 could be tolerated at infrequent intervals with a sacri-
fice of effluent turbidity quality.
Suspended solids in the raw water supply in amounts sufficient to require
the addition of coagulation and sedimentation facilities to reduce the
suspended solids to an acceptable level for filtration, will cause a
jump in treatment costs due to the additional treatment step. Figure 44
illustrates the approximate capitalized and operational costs for filtra-
tion plants and for coagulation, sedimentation, and filtration facilities.
The difference in these costs for a plant of a specific size would be the
additional cost for up-grading a filtration plant on an annual capital
and operational basis. The filtration costs are from Smith (Reference
86) and coagulation filtration costs from Koening (Reference 49),
B. Chemical Costs
Young (Reference 139) evaluated the chemical costs for water treatment
against several pollution indicators. A correlation of chemical cost
for certain specific pollution indicators was found; however, no chemical
cost correlation was found for suspended solids removal. This seems
consistent with what is known about coagulation, as the optimum coagulant
dose for a water depends primarily on the chemistry of the water and, in
some cases, on the nature of the suspended material, but is, more or less,
independent of the amount of suspended solids present.
In a study conducted by Engineering-Science, Inc. for the United States
Public Health Service, USPHS (Reference 31), coagulation experiments
were made with two different clay suspensions, kaolinite and bentonite.
The results of coagulation experiments at different initial suspension
concentrations confirm the lack of correlation of chemical dosage on
turbidity removal. A 200 mg/1 kaolinite suspension demonstrated improved
coagulation at a lower alum dosage than a 50 mg/1 concentration. However,
the 200 mg/1 of bentonite suspension required a larger dosage of alum
than the 50 mg/1 suspension of bentonite. Thus, there seems to be no
general relationships for chemical coagulation costs versus suspended
solids level. However, such a relationship may exist for a specific
water and specific type of suspension.
C. Sludge Disposal Costs
There is a direct relationship between the cost of dewatering and dis-
posing of water treatment plant sludge, and the level of suspended solids
in the raw water supply. The amount of sludge accumulated is propor-
tional to the solids removed. For the purpose of estimating sludge
production, it should be assumed that 100 percent of the raw water sus-
pended solids will be removed by the treatment facility and will appear
as sludge. Sludge is composed of the removed solids plus coagulation
chemicals. For high concentrations of suspended solids the amount of
chemicals is but a small part of the total sludge, but for low concentra-
tion levels the proportion of chemicals can be significant. In the latter
69
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cases however, the total amounts of sludge are small as compared to the
amount of water treated. In view of the wide variability of available
cost data, it is considered reasonable to assume that the weight of the
sludge will be equivalent to the weight of the suspended solids in the
raw water, for the purposes of this report only.
An AWWA Research report on "Disposal of Wastes from Water Treatment Plants
Part 3" by Adrian and Nebicker (Reference 1) evaluated costs for sludge
disposal from several plants and for different sludges. The disposal
costs for alum sludge, for publicly-owned and operated plants, varied
from a low of $2.00 per ton dry solids for lagooning to $56.00 per ton
dry solids for drying on sand beds. As a general rule, the higher unit
costs were for smaller installations. A model study for thickening and
vacuum filtration of alum sludge projected a $122.00 per ton dry solids
for disposal. Lagooning was observed to be the most widely-used process
for dewatering and disposing of sludges. For the purposes of this report,
the costs for the three publicly-owned alum lagoon disposal systems report-
ed in Reference 1 will be used for the unit disposal costs. The weighted-
average cost for removal of a total of about 1800 tons per year was $10.00
per ton dry solids. The low value was $2.00 per ton d::y solids for a 1400
tons per year plant, and the high-value was $39.00 per ton dry solids for
a 275 tons per year plant. The low cost was obtained .it a plant with an
annual average flow of 90 mgd and a capacity of 170 mgd, while the higher
cost was experienced at a plant with an average annual flow of 9 mgd and
a capacity of 20 mgd.
There are many other less definable treatment costs which may also be
associated with costs due to increasing suspended solids removal; however,
the costs of sludge disposal represents the major cost..
Variability of the density of sludge and the water content at the time
of removal are so great as to preclude the specification of a meaningful
general figure for converting tons of sludge solids to cy. Solid contents
can be as low as 1.5 percent, and values of 30 percent for thickened
sludge are normal. Thus each situation must be independently analyzed.
D. Summary
Three areas of possible increased water treatment costs; due to increasing
suspended solids in the raw water were evaluated. Two of the three
general areas examined would result in increased costs. In some cases,
surface water of low suspended solids content may be filtered without
coagulation and sedimentation. Figure 44 illustrates the annual capital
and operation cost comparison for the two treatment methods. The cost
for adding coagulation and sedimentation to solve a temporary problem
of excessive suspended solids will be very high when based on the tons
of suspended solids removed. Expansion of a treatment facility for this
purpose alone must be evaluated for the specific situation.
Increasing suspended solids in raw water already being treated by coagu-
lation, sedimentation, and filtration will increase sludge handling costs
70
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in proportion to the suspended solids loading. No general correlation
of increasing chemical costs due to suspended solids content was es-
tablished; although such a correlation may be found for a specific water
supply.
The principal cost increase in water treatment plants because of increased
turbidity ranges from $2.00 to $56.00 per ton of dry weight of sludge,
with a value of $10.00 per ton being a representative weighted-average
figure for lagooning as a means of sludge disposal. These costs would
pertain to publicly-owned plants containing complete treatment processes.
co
o
1,000
500
£C
UJ
Q.
CO
o
Q
CO
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1
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tr
100
50
20
10
-\ \ 1 1—i—i—r
-\ 1 1 1—I—I—TT
KOENING ADJUSTED FROM 1967
-SMITH ADJUSTED FROM 1967
i i i i
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5 10 20
CAPACITY IN MGD
50
100
Figure 44. Treatment Costs by Filtration and Coagulation-Filtrations
Includes Capital and Operational
Costs (ENR Construction Cost Index 1800)
71
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SECTION VII
ESTIMATING POTENTIAL SOIL LOSS
1. INTRODUCTION
In addition to the cost of erosion control measures, it is necessary
to know how" much sediment erosion is prevented by the use of control
measures. Also, the amount of sediment retained on-site by the use of
one or a combination of several applicable control measures should be
estimable. The amount retained may be estimated as the difference be-
tween estimated soil loss without the protective measure(s) and the
estimated loss with the measure(s).
Estimation of potential soil loss under a specified set of circumstances
and over a particular period of time requires the use of some reasonable
approach. Such an approach should incorporate, to the maximum practicable
extent, present knowledge of the scientific factors involved, as well as
the valuable information contained in that body of knowledge commonly re-
ferred to as the "State-of-the Art." A number of formulas have been
developed for estimation of potential soil loss. None of these are com-
pletely satisfactory to experts in the soil conservation field, and
efforts continue to develop better expressions for the relationships
among the many complex factors which must be taken into account. For the
purposes of this report it is believed that the universal soil loss equa-
tion (References 131 through 137) is the most appropriate to use.
The principal reasons for selection of the universal soil loss equation
are as follows:
(1) The basic format is simple;
(2) The Equation incorporates all major factors known to influence
rainfall erosion;
(3) The Equation is based on the analysis of more data than any other
equation noted during the literature review aspects of the inves-
tigations which resulted in this report. More than 25 years of
research and analysis work have brought the equation to its pre-
sent form. During its initial development, 10,000 plot-years of
runoff and soil loss data were analyzed;
(4) The principal erosion-causing factor of rainfall energy and the
erosion-resistance factors inherent in the physical-chemical
properties of various soils are emphasized;
(5) The Equation is basically universally applicable, whether in
urban or rural areas of the world;
(6) The Equation has the flexibility to produce answers with a reason-
able minimum amount of basic data and to give better answers with
increased amounts of basic data;
73
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(7) It has been used by and is currently in active use by the U.S.
Soil Conservation Service in many areas of the United States;
and
(8) Current research work is an progress to improve the Equation.
Principal limitations of the Equation are as follows:
(1) It is semi-empirical. While all factors included have important
influences on soil loss due to erosion, the Equation does not
necessarily express them in their correct mathematical rela-
tionships, and this limitation must be overcome by the selection
of proper empirical coefficients.
(2) It applies only to erosion caused by rainfall of "normal" types
encountered in the United States. It does not apply to erosion
caused by snow-melt runoff or by very light, misty precipita-
tion with little or no erosive energy. The Equation can be used
in other areas of the world with proper modifications to fit
the rainfall energy patterns prevailing, if necessary;
(3) The physical data upon which the present coefficients are based
were limited to maximum uniform slopes of 20 percent and lengths
of 300 feet.
(4) The Equation predicts only the soil loss from relatively small
areas, and does not treat the matter of sediment deposition
after leaving these areas. Thus, watershed sediment yields
must be handled by other procedures. However, this limitation
is not highly important for the purposes of this study, because
the areas of construction sites are not large as compared to
total watershed areas.
(5) Absolute soil loss values obtained from the Equation can vary
from actual occurrences because of deficiencies in data and in
the presently available coefficients„ Hence., the Equation is
more accurate as an index to compare relative erosion under
specific circumstances.
(6) Because of the complexity of the phenomena involved, it is most
valuable when interpreted by qualified experts.
Application of the universal soil loss equation is outlined in the re-
mainder of this section. The best summary of the method is presented in
Reference 136. That reference, however, limits applications to crop-
lands east of the Rocky Mountains. Subsequent developments, including
some of the hydrologic analyses summarized in Appendix B of this report,
extend the applications to the entire country.
74
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2. THE ARS "UNIVERSAL SOIL LOSS EQUATION."
The universal soil loss equation developed by the Agricultural Research
Service is a semi-empirical predictive relationship between the mass of
soil-loss per unit area and all major factors known to influence rain-
fall erosion. It has the form:
A = RKLSCP (1)
where: A = the computed soil loss in tons (dry-weight) per acre from a
given storm period;
R = the rainfall erosion index for the given storm period in
units of ft-ton in: per acre-hr (described further below);
K = the soil erodibility value, defined as the erosion rate in
tons per acre per unit of R for a specific soil in continuous
fallow condition on a 9 percent slope having a length of 72.6
ft;
L = the slope length factor, defined as the ratio of soil loss
from a specific field to that from a unit field having the
same soil type and slope but with a length of 72.6 ft;
S = the slope factor defined as the ratio of soil loss from a
specific field to that from a similar field but having a
9 percent gradient;
C = the cropping management factor defined as the ratio of soil
loss from a field with specified cropping and management to
that from the same field but under fallow condition, and;
P = the erosion control practice factor defined as the ratio of
soil loss with a given practice (contouring, strip-cropping,
or terracing) to that with straight-row, up-and-down slope
farming.
Applications of the full Equation are given in Section VIII, Basin Selec-
tion and Evaluation, Each of the factors defined above are discussed in
the following pages of this Section.
A. R, Rainfall Factor
The rainfall factor, R, also known as the rainfall erosion index, is
defined for a single storm as:
R = §0 <2)
where: E = the total kinetic energy of a given storm in ft-tons per ac
and I is the maximum 30-minute rainfall intensity for the
area in inches per hr.
75
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The rainfall factor is thus a composite term, representing the effects of
raindrop impact for the entire storm duration and maximum rainfall inten-
sity. It can be expressed as a function of rainfall intensity alone.
The records of individual storms are summed over a given time interval
to obtain cumulative R-values for other periods of time, such as for a
month or a year. .The annual R factors for approximately 2,000 locations
in the United States have been summarized in the form Df "iso-erodent"
maps (Reference 136). Figure 45 shows an example of these maps. The
same publication also provides data for estimating monthly soil loss in
the eastern United States, and expected magnitudes of single-storm ero-
sion index values for various return periods.
For comparing the effects of different conservation measures on con-
struction sites it is necessary to be able to estimate potential soil-
loss values for an entire range of periods of time, ranging from indi-
vidual storms to annually. A recent SCS publication (Reference 105)
provided clues which led to the development of generalized equations for
determination of the rainfall erosion index. This development is sum-
marized in Appendix B of this report; however, the essential results are
set forth in this Section for use with the soil loss equation.
SCS studies have shown that the time distribution of rainfall in the
United States can be represented adequately for many purposes by the two
curves shown in Figure 46. Reference 105 by the SCS also presented a
graphical relationship between Type II 2-yr frequency, 6-hr duration rain-
fall and the Annual rainfall erosion index. This is shown in Figure 47
together with a similar curve for Type I rainfall developed by this study
from basic ARS, SCS, and USWB data cited in Appendix B. Thus, the Annual
rainfall erosion index can be obtained from the graph by entering with
the 2-yr, 6-hr rainfall for the location under study. The latter values
are presented on maps such as Figure 48, or may be developed independently
from basic local data.
Using Figure 48 as a base, and the curves of Figure 47, the iso-erodents
of Figure 49 were prepared. The extremely close correlation to the ori-
ginal iso-erodents presented in Figure 45 can be observed.
The rainfall erosion index for individual storms can be obtained from
either Figure 50 or 51.
B. Summary Procedures for Estimation of Rainfall Erosion Index
(1) Example I - Rainfall Erosion Index for a 2-yc 6-hr Storm
This storm can be considered to be a typical "average" storm,
because it can be expected to occur 50 percent of the time, and
the 6-hr duration has been found by SCS to be the most frequent-
ly occurring storm length.
(a) Locate the area under study on a chart in USWB TP No. 40
(or similar publication) similar to Figure 48.
76
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(b) Determine the value of the 2-yr 6-hr rainfall from the
preceding chart.
(c) Check as to the zone (Zone I or Zone II) in which the area
under study is located.
(d) Use the graph in Figure 50, or Figure 51 to arrive at the
erosion index, using the 6-hr duration line.
Examples:
Walnut Creek Drainage Basin, California. (Zone I) From
USWB TP 40, the 2-yr 6-hr rainfall is given as 1.5 inches.
Therefore, the erosion index for this storm duration is
found from Figure 50 to be 12.
Occoquan Drainage Basin, Virginia (Zone II) From USWB TP
40, the 2-yr 6-hr rainfall is given as 2.55 inches. The
erosion index for this storm is found to be 66.
(2) Example II - Rainfall Erosion Index for Storm of Any Duration
Up to and Including 24-hr for 2-yr Frequency.
The same procedure as for Example I may be used except that the
chart used from USWB TP 40 will be the one for the storm fre-
quency and duration desired.
(a) The graph in Figure 50 or Figure 51 is used to arrive at
the erosion index using the appropriate depth of rainstorm
and duration hour line.
Example:
Determine the erosion index for a 24-hr storm with a 2-yr
frequency in the vicinity of Occoquan. United States
Weather Bureau (USWB) TP 40 shows depth of precipitation
for such a storm to be 3.40 inches. Area is in Zone II.
The estimated erosion index from Figure 51 is 65.
(3) Example III - Average Annual Rainfall Erosion Index
(a) Locate the area under study in a chart in USWB TP 40 (or
similar publication).
(b) Determine the value of 6-hr rainfall for a 2-yr frequency.
(c) Check as to the Zone in which the area is located.
(d) Obtain the Average Annual Erosion Index from Figure 47.
Example:
Determine the 2-yr frequency annual erosion indices for the
Walnut Creek, California and Occoquan River, Virginia, areas,
Walnut Creek: 2-yr 6-hr rainfall, Type I = 1.5 in. Average
Annual Erosion Index = 40
Occoquan River: 2-yr 6-hr rainfall, Type II = 2.55 in.
Average Annual Erosion Index = 210
77
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Figure 45. Annual Iso-erodent Map of Areas East of the Rockies
(Reference 136, ARS)
78
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6L
RATIO ACCUMULATED RAINFALL TO TOTAL ( PX/P24)
rt
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Figure 47. Relation Between Annual Average Erosion Lndex and the 2-yr
6-hr Rainfall Depth for Two Rainfall Types
80
-------
00
2-YEAR 6-HOUR RAINFALL (INCHES)
Figure 48. Depths of the 2-yr 6-hr Rainfall, Inches, in Various Parts of
The United States (Reference 123, 124 USWB)
-------
2-YEAR 6-HOUR RAINFALL (INCHES)
ESTIMATED AVE. ANNUAL EROSION INDEX
Figure 49. Iso-erodent Map Derived from 2-yr, 6-hr Rainfall Map.
Superimposed for Area East of the Rockies.
82
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100
' I I ' " I '—' 1 • ' "I r
TYPE I RAINFALL EROSION INDEX = 15
T 1 | i i I I.
p2.2
H 0.6065
10
o
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O.I
10 100
INDIVIDUAL RAINFALL (TYPE I) EROSION INDEX
1000
Figure 50. Relation Between Depths and Duration of Type I Rainfall and
Single Storm Erosion Index. 2-yr Frequency of Occurrence
83
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TYPE I RAINFALL EROSION INDEX = 19.25T
10 100
INDIVIDUAL RAINFALL (TYPE H) EROSION INDEX
1000
Figure 51. Relation Between Depths and Duration of Type II Rainfall and
Single Storm Erosion Index. 2-yr Frequency of Occurrence
84
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C. K. Soil Erodibility Factor
The soil erodibility factor, K, represents the intrinsic credibility of
the soil and is determined experimentally as the ratio of erosion per
unit of R from a unit plot on a particular soil. (A unit plot is 72.6
ft long, has a uniform slope of 9 percent, is kept in continuous fallow
condition and is tilled for a period of at least 2 years or until prior
crop residues have decomposed). When all the conditions of a unit plot
are met, each of the factors, L, S, C, and P equal unity and K equals A/R.
K-values for 23 bench-mark soils, from which erosion has been experi-
mentally measured since 1930, have been identified (Reference 136) and
are listed in Table 3.
Wischmeier et al. (Reference 137) recently reported a new soil particle-
size parameter which can be used to derive a convenient erodibility
equation that is valid for exposed subsoils as well as farmland. A sim-
ple nomograph (Figure 52) provides quick solutions to the equation. Only
five soil parameters need to be known: percent silt, percent sand, or-
ganic matter content, structure, and permeability.
Entry values for all the nomograph curves, except the permeability class,
are for the upper 6 or 7 in. of soil. For scalped soils, this layer
would constitute newly exposed horizons.
85
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TABLE 3
K-VALUES OF 23 BENCH-MARK SOILS*
(1)
Soil
Source of Data
Computed K
Dunkirk silt loam
Keene silt loam
Shelby loam
Lodi loam
Fayette silt loam
Cecil sandy clay loam
Marshall silt loam
Ida silt loam
Mansic clay loam
Hagerstown silty clay loam
Austin clay
Mexico silt loam
Honeoye silt loam
Cecil sandy loam
Ontario loam
Cecil clay loam
Boswell fine sandy loam
Cecil sandy loam
Zaneis fine sandy loam
Tifton loamy sand
Freehold loamy sand
Bath flaggy silt loam with surface
stones » 2 inches removed
Albia gravelly loam
Geneva, N.Y.
Zanesville, Ohio
Bethany, Mo.
Blacksburg, Va.
LaCross, Wis.
Watkinsville, Ga.
Clarinda, Iowa1
Gastana, Iowa
Hays, Kans.
State College, Pa.
Temple, Tex.
McCredie, Mo.
Marcellus, N.Y.
Clemson, S.C.
Geneva, N.Y.
Watkinsville, Ga.
Tyler, Tex.
Watkinsville, Ga.
Guthrie, Okla.
Tifton, Ga.
Marlboro, N.Y.
Arnot, N.Y.
Beemerville, N.J.
0.69
.48
.41
.39
.38
.36
.33
.33
.32
.31
.29
.28
.28
.28
.27
.26
.25
.23
.22
.10
.08
.05
.03
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(1) *Referenee 186
(2) Evaluated from continuous fallow. All others were computed from row-
crop data.
86
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ro
OJ
PERCENT SILT + VERY FINE SAND
00 ->4 O> Ol
O O O O O
SOIL-ERODIBILITY FACTOR, K
-------
D. L, Slope Length, and S, Slope Factors
Although the effects of slope length and steepness on soil loss were
investigated separately, they are usually combined in a single factor,
LS. This factor is the ratio of soil loss per unit area from a given
field to that from the unit plot having a 9 percent slope and 72.6 ft
length. The combined LS factor can be computed from an empirical equa-
tion, which is shown graphically in Figure 53 (Reference; 105) .
The length times slope product (otherwise knows as topog;raphic factor,
LS) has been extended (Reference 105) to cover lengths up to 1,600 ft
and for slopes up to 50 percent (equivalent to 2H:IV). Figure 54 shows
extensions of the slope effect chart beyond the 800-ft slope length.
Slopes commonly used by highway engineers have been added onto the ori-
ginal curves. These extensions are indicated as being extrapolations
beyond the range of confirmed data. Therefore, they should be recognized
as speculative estimates. Extrapolated values for slopes of 4:1, 3:1,
2:1, and 1:1 have been added to the SCS graph.
E. C, Cropping - Management Factor
The cropping-management factor, C, is the ratio of soil loss from land
cropped under specified conditions to the corresponding loss from tilled,
continuous fallow conditions. The C-factor thus reflects the combined
influence of crop type and crop rotation pattern. The value of C is tab-
ulated in Reference 136 according to crop type and sequence, residue manage-
ment practice, and crop productivity level. Factors such as seasonal
distribution of rainfall, dates of plowing, seeding, and harvesting, and
methods of seeding and tilling must also be considered in computing C.
The method of establishing base values for the cropping-management factor
by controlling selected variables in the soil loss equation is described
in Reference 132 (Equation 1).
F. Pt Erosion Control Practice Factor
The erosion control practice factor, P, is a parameter representing the
reduction in soil loss resulting from soil conservation measures such as
contour tillage, contour stripcropping, terracing, and stabilized water-
ways. Values of P range from 0.90 for contouring on steep slopes (18
to 24 percent) to 0«25 for contour stripcropping on gentle slopes (Re-
ference 136). The effect of terracing is the reduction of the length of
slope from that of the entire field to the horizontal distance between
terraces. The methods of determining P for a given conservation practice
and, alternatively, the selection of a conservation practice, using the
soil loss equation, have been described in Reference 136>.
Revised values of erosion-control practice factor are listed in Reference
105 for given range groupings of land slope between 2 pe.rcent and 24 per-
cent for contouring, contour stripcropping, and terracing.
88
-------
00
CO
o:
CO
CO
o
o
GO
IOO
2OO
Figure 53.
300 400 5OO 6OO
Slope Length (Feet)
Slope-Effect Chart (Topographic Factor, LS
Modified from Reference 105)
700
800
-------
Soil-Loss Ratio (LS)
H-
OP
hj
fD
Ui
-P-
g x
O rt
O- 0)
H- 3
MI cn
H- H-
fl> O
P- P
cn
HI
i-i rt
O O
ft) rt>
Ml
(B cn
i-t M
n> o
0 -d
o ro
ro I
w
M Hi
O Hi
Ln ft)
N— ' O
o
D*
H
O
O
TO
H-
n
n
rt
o
CO
IH •• Iv
'/„
-------
3. PREDICTING WATERSHED SEDIMENT YIELDS
Though related to erosion, sediment yield from a watershed is seldom
equal, quantitatively, to the rate of erosion on the watershed, the
difference being because of deposition of material between the points
of erosion and measurement downstream. The parameter commonly used to
describe this process is the sediment delivery ratio, which is the per-
centage relationship between the average annual sediment yield at a
specified measuring point and the average annual gross, or total, erosion
occurring in the watershed upstream from that point.
A knowledge of the sediment delivery ratio is very useful in planning a
wide variety of water utilization and control structure such as dams,
diversion channels, and debris basins. Several investigators have tried
to correlate delivery ratio with various watershed physiographic factors
(References 26, 27, 64, 74 and 130). The investigators generally agree
that the sediment delivery ratio decreases with increasing drainage area
in a basin that is relatively homogeneous. However, many authors also
agree that annual delivery ratios are also greatly affected by climate
and rainfall patterns. The validity.of using a particular delivery-
ratio relationship beyond the physiographic province for which is was
developed is dubious. Until higher levels of competency are achieved
for estimating sediment delivery ratios the curves or equations available
at present should be used with the knowledge that they are, at best,
approximations. In Reference 130 it is pointed out that soil loss does
not have a strictly linear relationship with the rainfall erosion factor
R, as predicted by the universal soil loss equation. In some cases
examined, the equation over-estimated sediment production for years with
high R values.
Considering the present state of knowledge of sediment delivery ratios,
and the fact that construction sites are relatively small compared to
agricultural and total watershed areas (ranging to size from less than
5 ac to about 500 ac) the sediment delivery ratio, for the purposes of
this study, has been assumed to be 100 percent. This is believed to be
a reasonable, generally conservative, assumption. The assumption is,
thus, that all sediment eroded will leave land surfaces in the construc-
tion sites and will arrive at runoff channels, streets, ponds, or at
other places either within or below the site. Stated another way, the
total soil loss predicted by the universal soil loss equation is assumed
to be the amount of sediment which will eventually be deposited in a
place in which it is unwanted, either on or off the site.
4. RESERVOIR TRAP EFFICIENCY
When a sediment retention basin is to be built on a site, its trap ef-
ficiency must be taken into consideration in evaluating sediment yields.
A very small reservoir will not be as efficient as a very large one in
trapping sediment, however, at the same time, a large reservoir would
entail considerably greater costs.
91
-------
A valuable guide for predicting the trap efficiency of medium and larger
reservoirs has been established (Reference 9). Some work has been done
(Reference 67) on evaluating the trap efficiency of small reservoirs,
debris basins, and debris dams. However, prediction guides are still
inadequate and a complete study of the rate of sediment deposition in
a particular reservoir is usually required for accurate results. Such
studies would indirectly yield data on loss of storage capacity in re-
servoirs under question.
Figure 55 presents a curve showing the capacity/annual inflow ratio of a
reservoir versus sediment trap efficiency in percent. When the ratio is
0.01 such a small reservoir will trap about 45 percent cf the sediment
in the inflowing waters. Increasing the size of the reservoir ten times
i.e., to a ratio of 0.1, will increase its efficiency to about 85 percent,
Further increase in size of reservoir to a ratio of 1 will improve sedi-
ment removal efficiency up to 92 percent. Thus the law of diminishing
returns applies, whereby increased extraction of the sediments becomes
economically unjustifiable beyond a certain limit.
92
-------
o
ui
o
a.
<
a:
100
90
80
70
60
50
40
30
20
10
1—I—| I I I i [ 1 1—I | I I I I I 1 1—I—| I I I
I I I I I I
ODOI
0.01
O.I
CAPACITY: INFLOW RATIO
10
Figure 55. Relationship Between Capacity/Inflow Ratio and Sediment
Trap Efficiency of Reservoirs
93
-------
SECTION VIII
EFFECTIVENESS OF EROSION AND SEDIMENT CONTROL MEASURES
The effectiveness of some individual components of erosion and sediment
control methods can be found in published data (Reference 24, 107) but
little information is available on the various treatment combinations.
(Reference 26) . Furthermore, effectiveness factors have been derived
for agricultural practices and cannot always be assumed equivalent to
urban construction effectiveness. A method has been developed for es-
timating effectiveness of individual and systems erosion and sediment
control methods (Reference 26), and is described herein.
1. CALCULATING PERCENT EFFECTIVENESS
The various individual treatments may be viewed as cropping-management
(C) and conservation practice (P) factors for reducing soil losses. Thus,
the soil loss (A.) from a given construction site having erosion and
sediment control treatments is computed by the universal soil loss equa-
tion:
AI = RLSKCP (1)
If the same construction site was denuded and employed no erosion and
sediment control treatments, the soil loss (A_) would be:
A2 = RLSK (2)
since the factor C and P values equal 1.0. Values for RLSK are equivalent
in Equations (1) and (2) since the same construction site is used for
both equations. The soil retained on the construction site, because
erosion and sediment control treatments were employed, is computed by:
soil retained = A - A (3)
Therefore, the effectiveness percent of the treatments in retaining soil
on the construction site is:
A - A
% Effectiveness = — : - - x 100
RLSK - RLSKCP
x
= (1 - CP) x 100 (4)
Equation (4) can now be used to compute effectiveness for the various
erosion and sediment control alternatives providing Factor C and P values
are assigned for the individual treatment comprising a particular system.
95
-------
A. Factor C Values for Urbanizing Areas
Published Factor C values need to be adjusted for urbanizing areas because
stabilized surfaces are disturbed by construction traffic. Two assumed
construction conditions have been considered:
(1) Construction is completed within 18 months following initial
groundbreaking.
(2) When building is started six months after seeding, then con-
struction is completed within 24 months.
It is further assumed that three months of the 18- or the 24-month con-
struction periods are consumed by grading operations, a.nd that construc-
tion sites are without surface protection during this time.
Factor C values change with time following surface treatment. For example,
Factor C values for grass decrease from 1.0 to about 0.01 between seeding
and when the grass is reasonably well established. For construction sites,
Factor C values are assumed altered additionally by urban development
activities„
A typical example of estimating average Factor C value for seed, fertilizer
and straw mulch is as follows, after Reference 26:
Fraction of
Representative Construction
Months Factor C Value Period Product
0-3* 1.00 3/18 0.167
3-6 0.35 3/18 0.058
6-18 0.19 12/18 0.127
Average Factor C value for 18-month period = 0.352
*During 0-3 months, Factor C value is 1.0 because the
construction area has no surface stabilizing treatment.
Table 4 lists the average values of Factor C for various surface stabilizing
treatments from Reference 26 and Table 5 lists additional values for more
specific ground cover.
96
-------
TABLE 4
AVERAGE FACTOR C VALUES FOR VARIOUS SURFACE
STABILIZING TREATMENTS
(After Reference 26 with some modifications)
Factor C Values for
Time Elapsed Between
Seeding and Building
Treatment
None*
6 Months**
Seed, fertilizer and straw mulch.
Straw disked or treated with asphalt or
chemical straw tack. 0.35 0.23
Seed and fertilizer 0.64 0.54
Chemicals (providing 3 months protection) 0.89
Seed and fertilizer with chemicals
(providing 3 months protection) 0.52 0.38
Chemical (providing 12 months protection) 0.56
Seed and fertilizer with chemical
(12 months protection) 0.38
*Assumes 18 month construction period.
**Assumes 24 month construction period.
Table 5 lists average effectiveness for several types of ground cover
presented in Reference 24.
Bo Factor P Values For Structures
Structures used in the various control systems are considered as requiring
Factor P values to describe their efficiency. These components include
small sediment basins, erosion reducing structures, and downstream sedi-
ment basins with or without chemical flocculants.
97
-------
TABLE 5
EFFECTIVENESS OF GROUND COVER ON EROSION LOSS AT CONSTRUCTION SITES
(After Erosion-Siltation Handbook, Reference 24)
Soil Loss Reduction Related to
Bare Surfaces
Kinds of Ground Cover (Percent Effectiveness)
^Seedlings
Permanent Grasses 99
Ryegrass (Perennial) 95
Ryegrass (Annual) 90
Small Grain 95
Millet & Sudangrass 95
Field Bromegrass 97
Grass Sod 99
Hay (2 Tons per Ac) 98
Small Grain Straw (2 Tons per Ac) 98
Corn Residues (4 Tons per Ac) 98
Wood Chips (6 Tons per Ac) 94
**Wood Cellulose Fiber (1-3/4 Tons per Ac) 90
**Fiberglass (1,000 Lbs per Ac) 95
**Asphalt Emulsion (125 Gal per Ac) 98
*Based on full established stand
**Experimental - not fully validated
98
-------
(1) Small Sediment Basins - The conventional method employs small
sediment basins having capacity to inflow ratios of 0.03 to
0.04, with an average trap efficiency of 70 percent. Thus, if
the sediment basin collects sediments coming from only 70 per-
cent of the construction area then its Factor P value is
(1.00 - 70% x 70%) = 0.50. On the other hand, if it collects
sediments from 100 percent of the construction area then its
Factor P value is (1.00 - 70% x 100%) = 0.30.
(2) Downstream Sediment Basins - The larger size basin constructed
downstream of the construction site and having capacity to in-
flow ratios of 0,06 to 0.07 will have a trap efficiency of
80 percent, thus, the corresponding Factor P value is 0.20.
Chemical flocculants may be added to this downstream basin to
cause more efficient settling of incoming sediment. Such
chemicals are assumed to increase the trap efficiency of this
basin 90 percent, giving a Factor P value of 0=10.
(3) Erosion-Reducing Structures - Diversion Berms, sodded ditches,
interceptor berms, grade stabilization structures and level
spreaders are collectively referred to as one system called
erosion reducing structures.
The overall effectiveness of erosion reducing structures is
estimated at 50 percent. The Factor P value for this normal
usage is then 0,50. For higher usage, the erosion reducing
structures are estimated to be 60 percent effective, giving a
Factor P value of 0.40 for this case.
Factor P values for these systems are summarized in Table 6 and are
discussed below.
In using these Factor P values to estimate effectiveness of the erosion
and sediment control alternatives, it is assumed that 100 percent of the
sediment not caught by the surface stabilization treatments and/or erosion
reducing structures is delivered to the sediment basins.
99
-------
TABLE 6
FACTOR P VALUES FOR COMPONENTS OF
EROSION AND SEDIMENT CONTROL SYSTEMS
(After Reference 24 with some modification)
Factor P
Component Value
Small sediment basin: (0,04 ratio)
Sediment from 70% construction area 0.50
Sediment from 100% construction area 0.30
Downstream sediment basin: (0.06 ratio)
With chemical flocculants 0.10
Without chemical flocculants 0.20
Erosion reducing structures:
Normal rate usage (165 ft per ac) 0.50
High rate usage (over 165 ft per ac) 0.40
C. Computing System Effectiveness
The effectiveness of various erosion and sediment control, alternatives is
computed and listed in Table 7, using the equation:
Percent Effectiveness = (1-CP) x 100
Factors C and P are taken from Tables 4 and 6, respectively.
Factor P values are multiplied if a particular erosion and sediment con-
trol alternative has two or more components represented by a Factor P.
An example of this calculation is shown using the conventional method of
erosion and sediment control.
Factor C or P
Conventional Method Value
Sediment basin (.04) 0.50
Erosion reducing structures (normal) 0.50
Seed, fertilizer and straw mulch 0.35
Percent Effectiveness = l-(0o35 x 0.50 x 0.50) x 100 = 91.25 percent.
100
-------
TABLE 7
PROMISING CONTROL SYSTEM AND EFFECTIVENESS
(After Reference 26 with modifications)
System Numbers Components Percent Effectiveness
1 Seed, fertilizer, straw mulch. 91
Erosion structures (normal). Sedi-
ment basins (0.04 ratio, and 70 per-
cent of area)
2 Same as (1) except chemical (12 90
months protection) replaces straw
3 Same as (1) except chemical straw 91
tack replaces asphalt
4 Seed, fertilizer, straw mulch. Diver- 90
sion berms. Sediment basins (0.04 ratio
and 100 percent area)
5 Seed, fertilizer, straw mulch. Down- 93
stream sediment basin (0.06 ratio)
6 Seed, fertilizer, chemical (12 months 92
protection). Downstream sediment basin
(0.06 ratio).
7 Seed, fertilizer, straw mulch. Down- 96
stream sediment basin using flocculants.
8 Same as (7) without straw mulch- 94
9 Chemical (12 months protection) sedi- 94
ment basin using flocculants.
10 Same as (9) with seed, fertilizer 96
101
-------
SECTION IX
EVALUATION OF COSTS FOR SELECTED BASINS
1. INTRODUCTION
An initial objective of the present study was to obtain data from at least
two climatologically different river basins where development and accom-
panying, or subsequent, erosion and sediment deposition were occurring.
At least one basin was to be selected in the arid west and the other in
the more humid eastern United States. The purpose of these different
locations was to give a representation of the range of erosion problems
and types of erosion control procedures and costs in urban areas as well
as costs of correcting erosion and sediment damages in such areas.
In the early stages of data collection it became evident that in order to
obtain sufficient data on erosion and sediment control measures, work in
several river basins would have to be investigated. This was particularly
true for cost data in California. Each of the basins studied contains
one or more important specific erosion or sedimentation problem. Conse-
quently, it is felt that the sum total of information collected and
analysed presents a representative view of the scope and perspective of
urban erosion and sediment problems in California and in the Virginia -
Washington, Do C«, area.
The two typical river basins selected for more intensive data collection
and presentation in this report are: (1) The Occoquan Creek Basin in
Virginia, representing the humid region. (2) The Walnut Creek Basin in
California, representing the arid region.
In both of these basins considerable residential and commercial develop-
ment activity is currently taking place.
2. SELECTION CRITERIA
In the basin-selection surveys the following criteria were used both in
qualitative and quantitative comparison of the several candidate basins
considered in the humid and arid climatic regions.
(1) Numbers of land development, highway, and/or airfield projects,
active or recently active, within the basin.
(2) Extent and quality of available data on erosion and sediment
damage, control measures and costs.
(3) Availability of processed data by U.S. Soil Conservation Service
on rainfall erosion indices, soil erodibility factors and soil
surveys.
(4) Availability of rainfall intensity-duration data near the project
sites.
(5) Potential extent of construction work in the near future where
erosion damage could possibly occur.
(6) Degree to which basin can be considered typical of other basins
in the United States.
(7) Distance from basin to project offices and extent of travel re-
quired within basin to obtain data.
103
-------
Date for the above selection criteria were obtained from the U.S. Depart-
ment of Commerce's Construction Reports, private banks' reports of building
permit activity in the cities and counties of California, and several
local, county, state and regional agencies. Other data were gathered
from the published literature and open-file records made available by
public agencies.
Based on the extent of erosion and sedement problems, several counties
were evaluated for the purposes of selecting study areas. Areas with
previous intensive records of erosion studies, such as the Seneca Water-
shed in Maryland, were excluded to avoid duplication. However, existing
reports from such areas were obtained and used as a check against data
developed herein.
3. RIVER BASINS SELECTED
A. Occoquan Creek Basin, Virginia
The drainage area of this basin is 546 square miles. The land area com-
prises portions of four counties in Virginia, namely, Prince William,
Fairfax, Loudoun and Fauquier. (Figure 56).
Manassas, Manassas Park and Warrenton are three cities that lie wholly
within the boundaries of the basin. Portions of the city of Fairfax and
the town of Woodbridge are located inside the basins, but near its pe-
riphery.
1. Topography & Soils
The northwestern borders of the Occoquan Basin have rugged terrain.
Most of it, however, is moderately undulating land, with the average
elevation of this portion being under 250 feet above sea level. Con-
siderable areas of the basin are covered with woods and brushwood.
The most recent and comprehensive soils report for the area was that for
Prince William County; data was also available for Fairfax County soils.
For the purposes of this study the soils of these two counties were con-
sidered sufficiently representative to identify the general nature of
soil erosion in the developing portion of the basin. Table 8 lists the
predominant soils in Prince William County within the confines of Occoquan
Basin, and the estimated K-factor values for both surface soils and sub-
soils. The method referred to in Section VII, using Figure 52, was used
to estimate the soil erodibility K-factors in Prince William County.
Percent silt and very fine sand, as well as percent sand were estimated
for each soil from the predominant soil type using the soil texture tri-
angle (Figure 57) and by assigning average numerical values representative
of each type. Percent organic matter was readily available for some
soils. For others, it was estimated from descriptive Information on the
color, fertility and productivity of soils under consideration. Soil
structure and permeability estimates were translated into numerical de-
signations as prescribed by Wischmeier e_t al. (Reference 137) . The
variation of soil types found in the areas being developed is usually of
importance as it directly affects erodibility variations within the area.
104
-------
OCCOQUAN ^
DRAINAGE V^W
BASIN ^S.
39° 00'
38°45
38° 30'
0 12345
SCALE - MILES
Figure 56. The Occoquan Creek Drainage Basin, Northeastern Virginia
(Numbers identify development projects listed in text)
105
-------
U. S. D. A.
GUIDE FOR TEXTURAL CLASSIFICATION
100.
90A
80>
xxxwyio I I Y. . .^v*/.. .IT. j ^^
JXXXXXXX clay loam SffiffiflBffiSrs ioam
tVWWuV........... .//M.WJLO7J.ZA, y?1"
percent sand
Soil Separate
Particle Diameter mm
Very Coarse Sand 2.00-1.00
Coarse Sand 1.00-0.50
Medium Sand 0.50-0.25
Fine Sand 0.25-0.10
Very Fine Sand 0.10-0.05
Silt 0.05-0.002
Clay Less Than 0.002
Figure 57. USDA Guide for Textural Classification
106
-------
TABLE 8
SOIL ERODIBILITY. K. VALUES ESTIMATED
FOR SOME SOILS IN PRINCE WILLIAM COUNTY IN
THE OCCOQUAN WATERSHED.
VIRGINIA
Tentative
Map Tentative
Symbol Soil Name
11
14
16
20
29
38
40
48
52
60
61
63
67
71
72
73
75
78
91
92
104
111
128
144
148
460
Bermudian
Manas s as
Beltsville
Meadowville
Ruxton, Cobbly
Beltsville
Mecklenburg
Iredell
Elbert
Appling
(Loamy and Gravelly Sediments)
Louis burg
Klinesville
Penn and Bucks
Bucks
Penn
Penn
Calverton
Birdsboro
Raritan
Catlett
Buncombe
Montalto
Ruston-Beltsville
Iredell-Mecklenburg
Appling-Glenlg
Surface
Texture
Silt loam
Silt loam
Loam
Silt loam
Silt loam
Fine sandy
Silt loam
Silt loam
Silt loam
Fine sandy
,
Sandy loam
Sandy loam
Silt loam
Loam
Silt loam
Loam
Silt loam
Silt loam
Silt loam
Silt loam
Loamy sand
Silt loam
Fine sandy
Silt loams
"•
Estimated
K-Factor of
Erodibility
Surface Subsoil
0.36
0.44
0.29
0.44
0.36
loam 0.37
0.38
0.43
0.37
loam Oo38
0.18
0.08
0.07
0.44
0.22
0.41
0.21
0.49
0.44
0.46
0.51
0.10
0.35
loam 0.47
0.44
0.29
- *
0.43
0.13
0.37
-
0.31
0.26
0.20
0.20
0.16
0.18
-
-
0.31
0.31
-
-
-
0.35
0.35
-
-
0.19
0.49
0.59
0.31
* The symbol " - " signifies that subsoil is either unweathered parent
material or otherwise unamenable to determination of K value.
107
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TABLE 9
VARIATION OF SOILS WITHIN CERTAIN AREAS OF
DEVELOPMENT IN THE OCCOQUAN WATER SHED
Name of Development
Predominant Soils Found in the Area
I - PRINCE WILLIAM COUNTY
Sudley
First Virginia Bank Site
Lewis Tract High School
Connor Tract High School
Lake Ridge Development and
Woodbridge High School
Occoquan Dam and Reservoir
II -
Occoquan Area
FAIRFAX COUNTY
K-Mart Shopping Center
Oakton Shopping Center
Dansbury Forest
III - FAUQUIER COUNTY
Baldwin Ridge
Bermudian, Manassas, Penn, Bucks,
Birdsboro, Raritan
Bermudian, Manassas, Penn,
Calverton, Catlett
Bermudian, Meaclowville, Ruxton,
Mecklenburg, Iredell, Elbert
Manassas, Klinesville, Penn,
Calverton
Beltsville, Appling, Louisburg,
Bunchcombe, Appling, Glenelg
Beltsville^ Louisburg, Ruxton-
Beltsville
Beltsville, Loamy and Gravelly
Sediments, Ruxt:on-BeItsville
Manor, Glenelg
Glenville, Rocky Lands, Elioak,
Breno, Louisburg
Mixed alluvial lands, Glenville,
Meadowville, Manor, Elioak,
Fairfax, Glenelg
Catoctin, Elioak, Lloyd, Manor,
Braddock
108
-------
TABLE 9 (Continued)
Name of Development
Predominant Soils Found in the Area
III - FAUQUIER COUNTY (Cent.)
Meadowvale
South Hill
Mill Run
Oak Ridge
Mars te Ha
White Gate
Kettle Run
Bethel
Manor, Stony hills, Starr,
Braddock, Elioak, Thurmont
Catoctin, Fauquier, Fauquier-
Elioak, Elioak
Manor, Elioak, Fauquier-Elioak,
Thurmont, Hazel
Fauquier, Catoctin
Calverton, Penn, Bucks, Montalto,
Wadesboro
Wadesboro, Penn, Starr, Calverton,
Bucks
Penn, Calverton, Bucks, Wadesboro
Catoctin, Penn, Croton, Stony
Hills
109
-------
Examples of such variation are shown in Table 9 wherein soils occurring
in each construction area in the Occoquan watershed are. listed by series
name. Variations within each series are also present, particularly in
surface texture and organic matter content. The values in Table 8 should
be considered very preliminary office-type estimates, z.s complete soil
analyses were not readily available.
Table 10 lists erodibility factor, K, and texture for Fairfax County Soils.
This table was taken from Fairfax County, Virginia, Erosion-Siltation
Control Handbook, August 1972, (Reference 24) and is presented herein
for reference purposes.
2. Rainfall and Runoff
The average annual rainfall in Occoquan Basin is approximately 44 in.
The distribution of rainfall during a normal year produces maximum erosion
index values during the months of May through October. The Occoquan
Basin falls within the boundaries of the geographic area listed by Wisch-
meier and Smith (Reference 136) as number 30. Here, the monthly distri-
bution of rainfall erosion index as a percent of the total annual erosion
index is as follows:
' Monthly
May
June
July
Augus t
September
October
9
15
20
20
10
°l
/o
7
/o
%
7
/o
7
/o
7-1/2%
Cumulative
9
24
44
64
74
81-
7o
7o
%
°L
%
•1/2%
The period of high erosion index values coincides with the heavy con-
struction period. Hence, it is very important that erosion and silta-
tion control measures are implemented before, during, and immediately
after construction.
The average runoff of Occoquan Creek near Occoquan, Virginia is 490 cfs.
From a drainage area of 546 sq mi, this represents 0.90 cfs per sq mi
of area.
Recorded extreme discharges are 1.0 cfs and 37,000 cfs for minimum and
maximum respectively, the former occurring during December 1941 and the
latter occurring during October 1942.
110
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FAIRFAX COUNTY SOILS
TABLE 10 ERODIBILITY FACTORS
(K) AND TEXTURES
(after Erosion-Siltation Handbook Reference
Soil Series
Belvoir
Braddock
Calve r ton
Chewacla
Elioak
Glenelg
Manor
Meadowville
Montalto
Wehadkee
Worsham
Horizon
B
C
B
C
B
C
A
C
B
C
B
C
A
C
B
C
B
C
A
C
B
C
Normal Texture
Silty clay loam
Silt loam
Silty clay loam
Silty clay loam
Silty clay loam
Silt loam
Silt loam w/mica
Silt loam w/mica
Silty clay loam
Micaceous silt loam
Silty clay loam
Micaceous silt loam
Weathered
Micaceous loam
Weath. Schist
Silt loam to clay
Silt loam to clay
Silty clay loam
Course sandy claylm
Silt loam
Silty clay to 1m
Silty clay loam
Silty loam w/rock
Erodibility
Class
Medium
Medium
Medium
Medium
Medium
Medium
Low
Low
Medium
High
Medium
High
High
High
Med ium
Medium
Med ium
Medium
Low
Low
High
Medium
24)
Class &
Range
.24-. 32
.24-. 32
.24-. 32
.24-. 32
.24-. 32
.240.32
.10-. 20
.10-. 20
.24-. 32
.37-. 49
.24-. 32
,37-.49
.37-. 49
.37-. 49
.24-. 32
.24-. 32
.24-. 32
.24-. 32
.10-. 20
.10-. 20
.37-. 49
.24-. 32
K Values
Norm
.28
.28
.28
.28
.28
.28
.17
.17
.28
.43
.28
.43
.43
.43
.28
.28
.28
.28
.17
.17
.43
.28
111
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TABLE 11
Developments In and Around Occoquan Drainage Basin. Virginia
1. Occoquan Reservoir Prince William Co.
2. Dale City »
3. Lewis Tract High School "
4. Conner Tract High School "
5. First Virginia National Bank "
6. New Gate Development Fairfax Co.
7. Lake Ridge Development and
Woodbridge High School Prince William Co.
8. Woodbridge - Occoquan Area Prince William Co.
9. Oakton Shopping Center Fairfax Co.
10. K-Mart Shopping Center "
11. Dansbury Forest "
12. Sudley - 450 acres - 1,611 townhouses
& apts Prince William Co.
13. Mill Run - 50 acres - 36 lots Fauquier Co.
14. Oak Ridge - 30 acres - 25 lots "
15. Meadowvale - 150 acres - 51 lots "
16. Baldwin Ridge - 100 acres - 42 lots "
17. Marstella - 200 acres - 144 lots "
18. Whitegate - 24 acres - 12 lots "
19. Kettle Run - 125 acres - 57 lots "
20. Bethel - 70 acres - 149 lots "
21. South Hill - 30 acres - 30 lots "
22. Casanova Hills - 145 acres - 19 lots "
23. Country Scene - 61 acres - 511 townhouses Prince William Co.
24. Coverstone Apartments - 67 acres - 1,000
garden apts "
25. Evergreen Farm "
26. Irongate - 65 acres - 650 townhouses "
27. Lakeridge - 2,974 acres - 8,980 townhouses
& apts "
28. Occoquan Forest - 978 acres - 2,166 townhouses
& apts "
29. Lakeview Estates - 94 houses "
30. Mountain Farm - 97 houses "
31. Point of Woods - 507 houses "
32. Hillcrest Estates - 96 houses "
33. Ashton Glenn - 45 acres - 528 townhouses
& apts "
34. Manassas Park Village "
35. Elysian Woods - 8 acres - 105 apts "
36. Pinewood Forest - 17 acres - 176 townhouses
(part of Lakeridge) "
37. Crestwood - 14 acres - 100 townhouses "
112
-------
3. Development Projects
There
progress and many others still in the planning stage. Table 11, lists
the various development in and around the Occoquan Drainage Basin, to-
gether with where information was available as to the overall size and
type of urban development. The numbers listed refer to the numbers on
the basin map.
4. Type and Extent of Control Practiced
In the Occoquan Basin the type and extent of erosion control practiced
is in line with standards of the U. S. Soil Conservation Service.
Generally speaking, before construction work is allowed to start,
the siltation and erosion control plans for the work must be reviewed
and approved by government officials in that area. Thereafter, all
erosion and siltation control measures are to be placed prior to or
as the first step in grading. Diversion dikes1, level spreaders, filter
berm and filter inlets, plus a sediment retention basin are the basic
components of such erosion control plans. In addition, erosion control
structures, temporary and permanent vegetative cover are stipulated or
implemented as and where required. Fairfax County has been so "erosion-
control" conscious that very recently they put out an Erosion-Siltation
Control Handbook (Reference 24).
B. Walnut Creek Basin, California
The drainage area of this basin is 138.4 square miles. It is also known
as Pacheco Creek Basin. The basin lies entirely within Contra Costa County
in California (Figure 58).
Walnut Creek, Lafayette, Concord, Pleasant Hill, Pacheco, Alamo, Danville
and San Ramon are the cities that lie totally or largely within the
drainage basin.
1. Topography & Soils
The Soil Conservation Service recently completed the field work of a new
soil survey for the Contra Costa County. The results of this survey will
be made available sometime in December 1973j however, soil survey maps
were made available together with the Contra Costa County General Soil
Survey and Report of August 1966 (Reference 19).
Table 12 lists the predominant soils and the estimated K-factor values of
these soils in Walnut Creek Basin, for both surface soils and subsoils,
and, in certain cases, for parent materials when the soil cover is less
than 36 inches in thickness. The method of estimating the K-factor values
was as explained for the Occoquan Basin.
113
-------
'WALNUT CREEK DRAINAGE BASIN,
I22°00'
38° 00'
\- 37° 45'
Figure 58. The Walnut Creek Drainage Basin, Central California
(Numbers identify development projects listed in text)
114
-------
TABLE 12
SOIL ERODIBILITY, K, VALUES ESTIMATED
FOR
SOILS IN CONTRA COSTA COUNTY
IN THE WALNUT CREEK WATERSHED
CALIFORNIA
Map
Symbol
BN-Zm
BN-Dg
sy
BN-Rn
CM-Bk
Cp-Rn
Cp-Rn/B-1
Pp
SX-Sm
Sb
Soil Name
Brentwood
Zamora
Sorrento
Los Robles
Brentwood
Rincon
Delhi
Sycamore
Brentwood
Rincon
Clear Lake
Botella
Salinas
Cropley
Rincon
Cropley
Rincon
Pescadero
Solano
San Ysidro
Sacramento
Surface
Texture
Clay loam
Clay loam
Clay loam
Clay loam
Clay loam
Clay loam
Sand
Silty clay loam
Clay loam
Clay loam
Clay
Clay loam
Clay
Clay
Clay loam
Clay
Clay loam
Clay
Loam
Loam
Clay
Surface
0.21
0.23
0.22
0.18
0.23
0.22
0.03
0.31
0.26
0.26
0.11
0.17
OolO
0.11
0.21
0.10
0.21
0.17
0.36
0.36
0.13
K Factor
Subsoil Parent
0.33
0.33
0.35
0.34
0.34
0.20
0.03
0.62
0.37 0.
0.18 0.
0.18
0.40
0.18
0.21
0.13
0.18
0.17
0.17 0.
0.21 0.
0.20 0.
0.18 0.
Material*
-
-
-
45
36
•*
-
-
19
33
31
20
* Parent material credibility is given for soils with less than
36-inch depth.
115
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TABLE 12 (Continued)
Map
Symbol
Sf-Ed
pw-Ed
Dg/Bc-2
TI-Ax/BD-2
Pn-Km
Dl-An/DE-2
Dl-An/F-2
An-SF/DE-2
An-SF/F-2
LE-Ge/FG-2
Soil Name
Staten
Egbert
Piper
Egbert
Delhi
Tierra
Antioch
Perkins
Kimball
Diablo
Altamont
Diablo
Altamont
Altamont
San Benito
Linne
Altamont
San Benito
Los Gatos
Surface
Texture
Peaty muck
Mucky clay loam
Sandy loam
Mucky clay loam
Sand
Loam
Loam
Clay loam
Clay loam
Clay
Clay
Clay
Clay
Clay
Silty clay loam
Clay loam
Clay
Silty clay loam
Loam
Surface
0.01
0.01
0.16
0.11
0.02
0.30
0.31
0.28
0.28
0.11
0.11
0.11
0.11
0.11
0.28
0.14
0.11
0.28
0.28-0.24
K Factor
Subsoil
O.OL
O.OL
0.24
0.15
0.02
0.2L
0.23
0.22
0.28
0.18
0.18
0.18
0.18
0.18
0.41
0.32
0.18
0.41
0.33
Parent Material*
_
—
-
-
-
0.31
0..31
0.15
0.29
-
—
-
—
-
-
—
-
—
-
LF-MI-FG-2
cv-LF/F-2
AE/DE-2
Gaviota Sandy loam
Sobrante Clay loam
Los Osos Clay loam
Millsholm Loam
Gazos Silt loam
Climara Clay
Los Osos Clay loam
0.23-0.17 0.22
0.18-0.13 0.32
0.25-0.21 0.18
0.27-0.22 0.33
0.27-0.22 0.29
Arnold
Loamy sand
0.14
0.25
0.12
0.18
0.22
0.12
* Parent material erodibility is given for soils with less than
36-inch depth.
116
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2. Rainfall and Runoff
The average annual rainfall in Walnut Creek Basin is 20 inches. During
a normal year 85 percent or more of the total rainfall occurs during the
months of November, December, and January. This period of relatively
heavy rainfall coincides with the period of minimum construction activity
in the area0 Therefore, provided that proper protective measures are
implemented, very minor erosion problems will be encountered in the basin.
There are no streamflow records available for Pacheco Creek near the
mouth, but there are data on discharges for Walnut Creek at Concord. The
mean discharge for the period 1965-1970 is 47 cfs from a drainage area
of 85.1 square miles or 0.552 cfs per square mile of area (Reference 76).
3. Development Projects
There are over 40 urban development and commercial building projects in
progress and many others still in the planning stage. Table 13 lists
some of the various developments together with information as to the
overall size and type of development.
The numbers listed refer to the numbers on the basin map.
4. Type and Extent of Control Practiced
In the Walnut Creek Basin the problem of erosion is perhaps not as critical
as in eastern states. Low values of both the rainfall erosion index and
the soil erodibility K-factor are mainly responsible for this. Further-
more, during the period May through September, when construction activities
are in full swing, no rainfall of consequence occurs. As a result, the
ordinances of Contra Costa County and the various cities within the Walnut
Creek basin stipulate only that proper and required erosion control work
be implemented by the contractor or builder developer. Nevertheless,
some developers expend considerable effort to control erosion, and grading
activities are watched by public inspectors to help minimize erosion pro-
blems which begin with the fall rains. Contractors are often "caught
short" by an early heavy rain, before erosion protection measures are in
place, or are effective, resulting in extensive sediment deposits in
streets and sewers.
117
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TABLE 13
DEVELOPMENTS IN
WALNUT CREEK DRAINAGE BASIN
CALIFORNIA
City of Concord
1. Northwood - 30 acres - townhouses & apts
2. Stanwell Industrial Park - 50 acres
3. Concord Industrial Park - 50 acres
4. Spanos - 15 acres - multi-family units
5. San Miguel Apartments - 5 acres
6. Shary Industrial Park - 100 acres
7. Presley Development - 300 acres - single family
detached & townhouses
8. Mackay Houses - 20 acres
9. Larwin Co. - 300 acres - single family detached
10. Ygnacio Hills - 50 acres - single family
detached houses
City of Pleasant Hill
11. Ridgeview Unit II - 30 acres - single family homes
12. Ridgeview Unit 1-31 acres
13. Golfridge - 12 acres - homes
14. Camel back - 50 acres - townhouses
15. Commercial Developments - 36 acres - stores
16. Briar wood Apartments - 2 acres
17. Valhalla Hills - 12 acres - homes
18. Rexford Homes - 41 acres - townhouses & apts
19. Shannon Hills Unit II - 8 acres - single family
20. Multi-Family - 3 acres
21. Rolling Green - 16 acres - cluster unit housing
22. Spring Meadows + Cleveland - 11 acres - multi-family units
23. Coggins Land - 8 acres - multi-family units
City of Walnut Creek
24. APR District - 17 acres - light industrial development
25. Interland Development - 30 acres - offices
26. Ginnochio - 70 acres - single family homes
27. Carriage Hills - 130 acres - residential
28. Skymont - 300 acres - residential
29. Rossmoor Leisure World - retirement community -
7,000 units yet to build
30. Indian Valley - 305 acres - single family homes
31. Walnut Avenue - Shell Ridge - 200 acres - single Eamily homes
32„ Viera-Franco Ranch - 400 acres - townhouses
118
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TABLE 13 (Continued)
City of Lafayette
33. Deutscher - 16 acres - housing, planned unit development
34. Eyring - 30 acres - housing, planned unit development
35. Hamlin - 40 acres - single family homes
36. Subdivision 4381 - 15 acres
Contra Costa County - Unincorporated Area
37. Secluded Valley - 67 acres - residential homes
38. Stone Valley - 50 to 75 acres of scattered single family homes
39o Ackerman Property - 94 acres - single family homes
40. Starview - 45 acres - single family homes
41. Several High Density Townhouse Clusters - 20 to 30 acres,
scattered
42. Sycamore Hills - 104 acres - single family homes
43. Danville Station - 169 acres - single family homes
44. Twin Creeks - 300 acres total; building in stages -
single and multiple family units
4. COST OF TYPICAL EROSION AND SEDIMENT CONTROL PLAN
While it had been hoped that costs for actual field examples of erosion
control measures could be obtained from developers and contractors in
the two selected basins, this was found to be impractical. These costs
were rarely identified separately, and the developer/contractor would
have had to spend a considerable amount of time and money to provide the
information desired. Several were able, however, to supply valuable in-
formation on procedures, and the cost of doing some specific part of an
erosion control practice, and this information was useful in developing
the costs for typical measures set forth elsewhere in this report.
In order to demonstrate the method of application of the unit costs
developed in this report, a typical example of a sediment and erosion
control plan is presented in Figure 59, from "Guidelines for Erosion and
Sediment Control Planning and Implementation," (Reference 120).
The scale was added onto the plan and the quantities were taken off the
plan and listed in Table 14. The area of the land is 2.95 ac and the
weighted average LS-factor is equal to 1.52.
To calculate the cost of sediment erosion control the appropriate unit
cost for each of the erosion and sediment control structures are taken
from Section V of this report. The average cost per acre for the pro-
ject is estimated at $1,340 for California and $1,110 for Virginia. See
Table 14 for a summary of the estimate.
119
-------
Figure 59. Example of Sediment and Erosion Control Plan
120
-------
TABLE 14
Item
Straw Bale Sewer
Inlet
Diversion Dike
Straw Bale Diversion
Gravel Weir
Sediment Ret. Basin
(cost extrapolated)
ESTIMATING COST OF SEDIMENT
AND EROSiON CONTROL PLAN
(SEE FIGURE 59)
Unit
Cost
Unit Quantity $
each 1 55,00
(46.34)
L. Ft. 575 4.51
( 3.70)
Bale 90 7.86
( 6.62)
6 Ft. 2 10.44
ea. ( 8.99)
cu. yd. 36 16.25
(13.75)
TOTAL COST
For 2.95 acre project
*
Cost per Acre
Cost
Calif. Virginia
$ $
55 46
2,593 2,127
707 596
21 18
585 495
$3,961 $3,282
$1,340 $1,110
If hydromulch & seed-
ing is used on
sloping banks, add
for:
California
Virginia
GRAND TOTAL COST PER
ACRE
$ 720
$2,060
$ 680
$1,790
Rounded off to nearest ten dollars.
121
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5. ECONOMIC COSTS
The costs that have heretofore been presented are capital or initial,
costs. To properly estimate the cost of retaining a unit of sediment on
a site, accounting must be made of the amortized cost of this capital
investment together with the annual costs of maintaining the protective
practice or structure.
Because of the many variables involved, Figure 60 has been prepared to
aid in calculating the economic cost of conserving a ton of soil per year.
The Figure shows that if $4,000 has been invested initially to conserve
200 tons of soil per year, and it is required to spend another $1,000 per
year, perhaps to irrigate as well as to maintain an area protected against
erosion, and the life of the practice, before having to be. completely re-
done to be fully effective, is 5 years, the cost of conserving each ton
in place is $10 per ton. If only 40 tons per year are saved, then the
cost is $50 per ton.
(Special Note applicable to Figure 60; The scale of the graph as shown
in this report is not convenient for capital costs under $2,000 and the
lower cost vegetative measures such as hydromulching fall in the latter
category. A new graph can be drawn, or alternatively, the; graph shown
can be used by dividing all values shown on the graph by 10, except the
value for "Soil Retained in Tons/Year." The dashed line example would
then be for an initial cost of $400, an annual maintenance: cost of $100/
year, and for 200 tons/year retained the annual cost in dollars per ton
per year would be $l/ton. Should a different interest rate be considered
applicable, only the lines in the lower left quadrant of the Figure need
be re-drawn,,)
Costs per ton can be converted to cost per cubic yard by application of
the proper unit density factor for the particular soil being considered.
Table 15 may be used to help in this regard. The values in this table
apply to soils in situ prior to erosion. Attention is invited to the
fact that care should be exercised in comparing volumes and weights of
deposited sediments with those of sediments in situ , to be certain that
differences in water content are properly handled.
6. COMPARATIVE COSTS OF CONTROLLING SEDIMENT
A comparative example of the costs of hydromulching to retain soil in
place, and the costs of removing eroded and deposited sediment from
streets, will be presented for both the Occoquan and Walnut Creek Basins.
An area ten acres in size with maximum uninterrupted length of 220 feet
in the direction of a uniform 10 percent slope will be used for the com-
parison.
A. Occoquan Creek Basin
The Occoquan Basin is situated in an area where the value of the annual
average erosion index, as given by USDA Handbook No. 282 iso-erodent map
122
-------
&>
7- •
§h
CO
/ N/ o/
j I
--3
...4.
--5
--K0
--7
--8
--9^
-ENTER HERE
I I
I I I I I I
I I
Figure 60. Economic Cost of Conserving a Ton of Soil Per Year
123
-------
TABLE 15
TYPICAL DRY* SOIL DENSITIES AND EQUIVALENT DEPTHS PER ACRE
(IN SITU SOILS UNDER NATURAL CONDITIONS)
Density
Soil Type
Clay
Silt
Clay-silt mixture**
Sand-silt mixture**
Clay-silt-sand mixture**
Sand
Gravel
Poorly sorted sand and
grave 1
Lbs/ft3
60-80
75-85
65-85
95-110
80-100
85-100
85-125
95-130
3
Tons /yd
0.81-1.08
1.00-1.15
0.88-1.15
1.2871.49
1.08-1.35
1.15-1.35
1.15-1.69
1.28-1.74
Tons /Acre /In
110-145
136-154
118-154
172-200
145-182
154-102
154-227
172-236
* For moist soils except for highly expandable moist clays use the
following formula:
D = d + 62.4 0
Where: D is density of wet soil, d is the density of dry soil, both
in pounds/cubic foot and 9 is volumetric moisture content in percent.
**Equal parts
124
-------
(Reference 136) is nearly 200. For a soil with a K-factor of 0.4, the
soil retained by hydromulching is estimated as follows:
A = RKLS(l-CP)
where R = 200
K = 0.40 (A typical soil in the basin)
LS = 2.0 (From Figure 53)
(1- CP)= 0..95 (Combined effectiveness)
A = 200 (0.4)(2.0)(0.95) = 152 tons per ac per yr
Initial Capital Cost = $370 per acre (From Table 1 )
Annual Maintenance Cost = $250 per acre (Assumed)
Using Figure 60 with an economic life of 10 years, the following two
results are obtained:
Total Annual Cost = $305 per ac
Cost per ton of Soil Retained = $2 per ton
B. Walnut Creek Basin
The Walnut Creek Basin is situated in an area where the 2-year 6-hour
rainfall is about 1.5 inches. Figure 47 indicates that the average
annual erosion index is about 40. Since the soils in the Walnut Creek
Basin are generally less-erodible than the soils in the Occoquan Creek
Basin, a soil with a K-factor of 0.25 is assumed. Identical plot size
and slope and practice effectiveness are assumed. The soil retained by
hydromulching is then estimated as follows:
A = 40 (0.25)(2.0)(0o95) = 19 tons per ac per yr
Initial Capital Cost = $430 per ac (From Table 1 )
Annual Maintenance Cost = $350 per ac (Assumed higher than in
Virginia due to summer
irrigation)
Using Figure 60 with an economic life of 10 years, the following two
results are obtained:
Total Annual Cost = $414 per ac
Cost per ton of Soil Retained = $21.80 per ton
For this particular example the cost per ton of soil retained is more than
ten times as much in the Walnut Creek Basin as in the Occoquan Creek Basin.
The two principal reasons for this difference are the much greater rainfall
erosion potential in Virginia, and the less-erodible soils in the Califor-
nia basin.
125
-------
Comparison of Costs of Retaining Soil by Hydromulching and Removing
Deposited Sediment
10-year Life Project
From the immediately preceding examples and the estimated costs of re-
moving deposited sediments set forth in Section VI, and assuming a soil
with an in situ dry weight density of 95 pounds per cubic foot and equi-
valent volumes for the deposited sediments, the following figures are
obtained.
Virginia California
Hydromulching Example, Cost of Retaining Soil $ 2 per ton $21.80 per ton
$ 2.56 per cy $27.90 per cy
Removing Sediment from Streets $ 6.60 per cy $ 8.00 per cy
Removing Sediment from Basements $65 per cy $77 per cy
Removing Sediment from Sewers $62 per cy $68 per cy
C. Projects With Life Less Than 10 Years
While the preceding example for a 10-year life project demonstrates the
general economic feasibility to the community of retaining soil in-place,
consideration needs to be given also to projects with an economic life
less than 10 years.
Using the same general conditions as in the immediately preceding example,
the costs of hydromulching projects with shorter economic lives have
been estimated, using an interest rate of 8 percent as in Figure 60.
Estimates also were made for one-acre areas (where the hydromulching cost
is about twice as much per acre as on a 10-acre tract job), and for a
one-year life job with no seed or fertilizer and only $100/year/acre
maintenance. The latter conditions are considered more realistic than
the other one-year estimate, since it would be illogical to spend large
sums of money on seed, fertilizer, or maintenance if such a short life
were known in advance. Such could be the case for some construction
projects. The following costs, and cost ratios, are the result:
126
-------
Unit Hydromulching Cost per Cubic Yard of Soil Retained - Example
to
•vl
Life of Project
Virginia Ratio
Cost of Retention
10-acre area
1-acre area *
California Ratio
Cost of Retention
10-acre area
1-acre area *
10 yrs
1.00
$ 2.56/cy
$ 5.14/oy
1.00
$27.90/cy
$56.,00/cy
5 yrs
1.12
$ 2.87/cy
$ 5.77/cy
1.10
$30.70/cy
$61.70/cy
3 yrs
1.29
$ 3.30/cy
$ 6.63/cy
1.25
$34.90/cy
$70.10/cy
1 yr
2.13
$ 5.45/cy
$10.95/cy
1.97
$55.00/cy
$110.50/cy
1 yr, no seed or fertilizer
$100 /acre /year maintenance
1.44
$ 3.69/cy
$ 7.41/cy
1.12
$31.25/cy
$62.80/cy
* Based on the assumption that both capital and annual maintenance costs vary proportionately
on a per acre basis as the capital costs shown in Figure 1, p. 16.
-------
It may be seen that in the Virginia example the investment in hydro-
mulching is economically justified in most cases on the basis that the
costs of retaining the soil in place are less than the direct costs of
removing deposited sediment.
On the California area studied, however, the cost of retention is greater
than the cost of removing sediments from streets with mechanical loaders
and trucks, and protection solely to avoid direct removal costs would not
be justified. However, even in California hand removal of sediment from
backyards and places where a front-end loader could not have access, is
more expensive than the cost of keeping the soil in place. Hence, even
in this area of relatively low erosion potential, there are distinct
community benefits to be derived from conserving soil-in-place, rather
than letting it erode and be deposited elsewhere in an undesired location.
D. Highway Construction (Steep Slopes)
In steeper slopes, the relatively low-cost hydromulchirig practice is not
as effective as the more expensive methods such as excelsior and netting.
The erosion potential on the steep slopes is in turn much greater. For
example, on a 2:1 highway slope (equivalent to a 50 percent slope) and
assuming an average highway fill slope length of 100 ft, then the topo-
graphic factor, LS, estimated from Figure 54, is 12.80. On the other hand,
for purposes of comparison the same length of 100 feet in an average
development area with a 10 percent slope will have a topographic factor
of 1.35 (estimated from Figure 53). In other words, increasing the
slope by 5 times means increasing the potential erosion soil-loss by
almost 10 times, assuming other factors remain constant. On a 1-1/2:1
highway slope (equivalent to a 66.7 percent slope), the LS for a fill
slope length of 100 ft is 19.6. Thus, the potential erosion on highway
slopes can be as much as 10 to 15 times those of average development
areas. In the Occaquan Creek Basin this means between 2,000 to 3,000
tons per ac per yr, while in the Walnut Creek Basin it means between
400 to 600 tons per ac per yr erosion potential on highway slopes.
Cost per acre for Excelsior Matting is estimated at $10,200 in Virginia
and $12,200 in California. Assuming a 95 percent effectiveness and
economic life of 5 years, with $250 per ac per yr maintenance required
through this period, the estimated costs per ton of soil retained on high-
way slopes are as follows:
Qccoquan
2:1 slope $1.40 per ton (2,000 tons per yr conserved)
1-1/2:1 slope $0.93 per ton (3,000 tons per yr conserved)
Walnut Creek
2:1 slope $8.25 per ton (400 tons per yr conserved)
1-1/2:1 slope $5.50 per ton (600 tons per yr conserved)
128
-------
These figures indicate that although excelsior matting requires a high
capital input per acre, it can be economically justified for use on steep
highway slopes even in the Walnut Creek. California area when steep slopes
of 1-1/2:1 or more are encountered.
E. Other Costs and Benefits
It is emphasized again that the costs of sediment removal summarized here
are only the direct costs of one aspect of sediment erosion damage. Where
erosion damage is so severe as to require repair work, this too is another
direct cost, and is not included herein. Furthermore, there are several
indirect costs which could be considered, such as interruption of business,
inconvenience, etc. However, the objective in this report was to provide
a reasonable basis for estimating the most direct costs involved. If
these in themselves justify conservation measures, then other costs
(benefits) only provide further justification.
It should be stated that the few examples of economic analyses set forth
in this report do not cover the entire range of possibilities which can
be explored. Each situation really should be studied and judged on its
own merits. Rainfall erosion potential, credibility of the soil, length
of time for which protection is needed and difficulty of access are per-
haps the more important of the many factors influencing economic costs.
If the procedures set forth in this report are followed, using data
applicable to the case under study, reliable results can be obtained
which can provide a rational basis for actual decisions.
129
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APPENDIX A
LIST OF SAMPLE COST ESTIMATE TABLES
Number Title Page
A-l Gravel and Earth Check Dam 134
A-2 Rock Riprap Check Dam 137
A-3 Concrete Check Dam 141
A-4 Concrete Chute 145
A-5 Diversion Dike 146
A-6 Erosion Check 147
A-7 Filter Berm 148
A-8 Flexible Downdrain 149
A-9 Flexible Erosion Control Mats 151
A-10 Gabions 153
A-ll Level Spreader 156
A-12 Sandbag Barriers 157
A-13 Sectional Downdrain 159
A-14 Sediment Retention Basin 161
A-15 Straw Bale Inlet Protection 164
A-16 Straw Bale Barriers 165
A-17 Excelsior Mat 166
A-18 Jute Mesh on One-Acre Plot 167
A-19 Straw or Hay 168
A-20 Woodchips 169
A-21 4" li. Square Plugs of Sod 171
131
-------
APPENDIX A
LIST OF SAMPLE COST ESTIMATE TABLES (Continued)
Number Table Page
A-22 Sodding 172
A-23 Chemical Soil Stabilizer 173
A-24 Sediment Removal From Streets 175
A-25 Sediment Removal from Basements 175
A-26 Sediment Removal From Storm Sewers
Bucket Line Cleaning 178
A-27 Sediment Removed From Storm Sewers
Rodding & Hydraulic Flushing of
Storm Sewer 179
132
-------
APPENDIX A
DETAILED COST ESTIMATES
Note: All Costs in these tables apply to San Francisco Bay Area,
Northern California in late 1972 - early 1973.
I - STRUCTURAL CONTROL MEASURES
Gravel & Earth Check Dam
CONDITIONS OF INSTALLATION:
This is one of the most simple temporary checks to construct. Earth is
first dumped in the channel, followed by a layer of gravel on the down-
stream side of the dumped earth.
PRODUCTION QUANTITIES AND RATES:
a. Costs have been estimated for different sizes of gravel and
earth checks:
(1) 5 ft-wide x 1 ft-high
(2) 10 ft-wide x 1.5 ft-high
(3) 15 ft-wide x 2 ft-high
b. Laborers can dig, haul, and compact at a rate of 9 cf/hr. Dozer
can spread and compact at a rate of 4 cy/hr.
133
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TABLE A-l
GRAVEL & EARTH CHECK DAM
SAMPLE COST ESTIMATE:
COST ESTIMATE
MATERIAL LABOR EQPT
1 ft high, 5 ft wide
Labor
Dig, haul & compact earth - 9 cf/hr m-hr
19/9 = 2 m-hr @ $8/hr
Q
Place gravel: - cf/ m-^hr @ $8.00
x .23 cy ^'
Material
Gravel @ $10/cy x 0.23 cy
1.5 ft high, 10 ft wide
Labor
85/9 = 9-1/2 mrhr @ $8.00/ m-hr
Placegravel: •
x .7 cy
Material
Gravel @ $10/cy x .7 cy
cf/
Unit Cost
Subtotal
45% OH & Profit
Total Cost
Cost/cf
7
3
$10
$.12
85cf
= $1
?1-
16
6
Unit Cost
Subtotal
45% OH & Profit
(small jobs)
Total
Cost/cf
2
1
$3
$.16
22
10
$32
$1.68
76
94
42
$136
$1.60
134
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TABLE A-l (Cont'd)
GRAVEL & EARTH CHECK DAM
COST ESTIMATES MATERIAL LABOR EQPT
2 ft High, 15 ft Wide
Labor
a. 1 Tractor OP 2 hr @ $11.00 22
bo 1 Laborer 2 hrs @ $8.00 16
c. Place grave1_9 cf/ m-hr @ $8.00
27
x 1.4 cy 37
Material
Deliver 8 cy earth @ $2.50/cy ^0
Gravel @ $10/cy x 1.4 cy 14
Equipment
D4 Dozer 2 hrs @ $10»00 20
Subtotal 34 75 20
45% OH & Profit 15 34 9
Total Cost $49 $109 $29
= $.83/cf
Unit Cost Cost/cf $.22- $.48 $.13
$187
225cf
135
-------
Riprap Check Dam
CONDITIONS OF INSTALLATION:
Excavate by hand, place masonry to grade, and build masonry wall and
backfill at same time by hand or with F/E loader.
PRODUCTION QUANTITIES AND RATES:
a. Cost estimates have been prepared for four different size
riprap checks:
(1) 5 ft wide x 2 ft high
(2) 10 ft wide x 3 ft high
(3) 15 ft wide x 4 ft high
(4) 20 ft wide x 5 ft high
b. The following production rates have been used:
Hand excavation -,0.4 cy/ m-hr
Masonry - 5.0 cf/ m^-hr
Compacted Fill - 2 cy/hr (machine)
- 0.3 cy/ m-hr (hand)
136
-------
TABLE A-2
ROCK RIPRAP CHECK DAM
SAMPLE COST ESTIMATES:
COST ESTIMATE
MATERIAL
LABOR EQPT
5 ft x 2 ft
Excav. 5 nHir @ $8.00
Masonry:
Deliver Cost = $0030/cf
Grout Mat'l = 0,20
$0.50/cf
56 x 0.50
Erect 11 m hr 0 $10.00
Fill
7 rn^hr @ $8.00
Foreman 4 hrs @ $9.00
28
Subtotal
18% Labor OH
25% OH & Profit
28
7
Total $35
Cost/cf Masonry $.62
Unit Cost
$392
56cf
= $7.00/cf Masonry
40
110
56
36
242
44
71
$357
$6.38
137
-------
TABLE A-2 (Cont'd)
RIPRAP CHECK DAM
COST ESTIMATE
MATERIAL
LABOR
EQPT
10 ft Wide x 3 ft High
Excav. 9 m4ir @ $8.00
Masonry:
Mat'l 131. x 0.50
131
66
Erect
= 26
@ $10.00
Fill
Fill
Mat'l 210 x 0.50
Place 42 tn^hr @ $10.00
F/E Loader: 7 hrs @$14.00
Loader OP - 8 hrs @$11.00
Laborer 8 hrs @ $8.00
105
Foreman - 16 hrs @ $9.00
Subtotal
18% Labor OH
25% OH & Profit
Total
105
26
Unit Cost
$1428
210cf
131
Cost/cf Masonry $.62
= $6.80/cf
72
260
17
Foreman
Unit Cost
15 ft Wide x
Excav.
Masonry:
m^hr @ $8.00
- 8 m-hr @ $9.00
Subtotal 66
18% Labor OH
25% OH & Profit 17
Total $83
Cost/cf Masonry $.63
;6.71/cf
4 ft High
10 m-hr @ $8.00
136
72
540
97
159
$796
$6.08
80
420
88
64
144
98
98
796
143
235
1,174
$5.59 $.59
138
-------
TABLE A-2 (Cont'd)
RIPRAP CHECK DAM
COST ESTIMATES MATERIAL LABOR EQPT
30 ft Wide x 5 ft High
Excav. 13 m*hr @ $8.00/ m-4ir 104
Masonry:
Mat'l - 300 cf x $0.50/cf 150
Place: 60 m^hr @ $10.00/ m^hr 600
Fill
F/E Loader: 14 hrs @ $14.00 196
Loader OP 16 hrs @ .$11.00 176
Laborer 16 hrs @ $ 8.00 128
Foreman - 40 hrs @ $9/hr 360
Unit Cost
= $8.17/cf Masonry
Subtotal 150 1,368 196
187» Labor OH 246
25% OH & Profit 38 404 49
Total 188 2,018 245
Cost/cf Masonry $.63 $6.73 $.82
139
-------
Concrete Check Dam
CONDITIONS OF INSTALLATION:
a. The construction procedure is as follows:
(1) Move-in
(2) Excavate for concrete slab
(3) Pour footings and place rebars
(4) Pour concrete
(5) Backfill where necessary
(6) Place timber, misc. steel, and riprap
(7) Clean-up
(8) Move-out
b. Dewatering of site has not been included in cost estimate
PRODUCTION QUANTITIES AND RATES:
a. Cost estimates have been prepared for four different size
concrete checks:
(1) 2 ft 4 in high x 5 ft 0 in wide* x 4 ft 0 in long
(2) 5 ft 6 in high x 9 ft 8 in wide x 8 ft 0 in long
(3) 5 ft 0 in high x 17 ft 6 in wide x 14 ft 0 in long
(4) 7 ft 0 in high x 20 ft 0 in wide x 20 ft 0 in long
*Width of stream
140
-------
TABLE A-3
CONCRETE CHECK DAM
SAMPLE COST ESTIMATE:
COST ESTIMATE MATERIAL
No. 1
Excav. (3.0 cy/hr)
B/hoe 4 hrs @ $10/hr
Operator 5 hrs @ $11.00/hr
Laborer 8 hrs @ $8.00/hr
Concrete
Forms: 10 Carp, hrs @ $10000/hr
50 sf @ $0.30/cf 15
Reinf. 3 m-hr @ $10. OO/ m-hr
285 Ibs @ $.10/lb 28
Pour: 6 @ $8.00/ m-hr
2.4 cy @ $20.00/cy 48
Metalwork
132 Ibs @ ($0.50/$0.30)/lb 66
Timber
58 bf @ ($0.20/$0.10)/bf* 12
Riprap
1.5 cy @ ($6.00/$5.00)/cy 9
Mobilization 50
Subtotals 228
18% Labor OH
25% OH & Profit 57
Total 285
Cost/cy $150
Unit Cost
$1136
7—^ — = $598/cy
L . ycy
LABOR
55
64
100
30
48
40
6
7
150
500
90
148
738
$388
EQPT
40
50
90
23
113
$59
*bf = board feet
141
-------
TABLE A-3 (Cont'd)
CONCRETE CHECK DAM
COST ESTIMATE
No. 2
Excav. (6 cy/hr)
Backhoe 5 hrs @ $10/hr
Operator 5 hrs @ $11.00/hr
Laborer 5 hrs @ $8.00/hr
Mobilization
Concrete
Forms: 27 Carp. hrs. @ $10.00/hr
132 sf @ $.30/sf
Reinf: 16 hrs. @ $10. 00 / nwhr"
1620 Ibs @ $.10/lb
Pour: 40 tn^-hr @ $8.00/ m-hr
13 cy @ $20.00/cy
Metalwork
266 Ibs @ ($0.50/$0o30)/lb
Timber
187 b£ (? ($0.20/$0.10)/bf
Riprap
8.6 cy @ ($6./$5.)/cy
Foreman
24 hrs (? $11.00/hr
Subtotals
18% Labor OH
25% OH & Profit
Total
Cost/cy
MATERIAL
50
40
162
260
133
37
52
$734
183
917
$85
LABOR
55
40
150
270
160
320
80
19
43
264
$1,401
252
413
2,066
$191
EQPT
50
50
$100
25
125
$12
Unit Cost
142
-------
TABLE A-3 (Cont'd)
CONCRETE CHECK DAM
COST ESTIMATE MATERIAL LABOR EQPT
No. 3
Excav. (8 cy/hr)
Backhoe 6 hrs @ $10.QO/hr 60
Operator 8 hrs @ $11.00/hr 88
Labor 8 hrs @ $8.00/hr 64
Concrete
Forms: 28 Carp, hrs @ $10.00/hr 280
140 sf @ $.30/sf 42
Reinf: 27 @ $10.OO/ m-hr 270
2700 Ibs @ $.10/lb 270
Pour: 72 @ $8.00/ m-hr 576
23 cy @ $20oOO/cy 460
Metalwork
330 Ibs @ ($0.50/$0.30)/lb 165 99
Timber
280 bf @ ($0.20/$0.10)/bf 56 28
Riprap
13.0 cy @ ($6./$5.)/cy 78 65
Foreman
32 hrs @ $11.00/hr 352
Mobilization 100 200 100
Unit Cost
4647 _ * 0,, ,
Y778 ~ $ 261 /cy
Subtotal 1,171 2,022 160
18% Labor OH 364
25% OH & Profit 293 597 40
Total 1,464 2,983 200
Cost/cy $82 $168 $11
143
-------
TABLE A-3 (Cont'd)
CONCRETE CHECK DAM
COST ESTIMATE MATERIAL
No. 4
Excav. (12 cy/hr)
Backhoe 7 hrs @ $10.00/hr
Operator 8 hrs @ $11.00/hr
6 cy Truck 7 hrs @ $12.00/hr
Truck Driver 8 hrs @ $9.00/hr
Laborer 8 hrs @ $8.00/hr
Concrete
Forms: 36 m-hr @ $10.00/hr
172 sf @ $0.30/sf 52
Reinf: 50 m~hr @ $10.00/ m-hr
4950 Ibs @ $0.10/lb 495
Pour: 125 m-hr @ $8.00/ m-hr
41 cy @ $20.00/cy 820
Metalwork
435 Ibs @ ($0.50/$0.30)/lb 218
Timber
360 bf @ ($0.20/$0.10)/bf 72
Riprap
20 cy @ ($6./$5.)/cy 120
Foreman
32 hrs @ $11.00/hr
Mobilization 150
Subtotal 1,927
18% Labor OH
25% OH & Profit 482
Total 2,409
Cost/cy $73
LABOR
88
72
64
360
500
1,000
130
36
100
352
300
3,002
540
886
4,428
$134
EQPT
70
84
100
254
63
317
$10
Unit Cost
= $ 217/cy
144
-------
Concrete Chute • 3 ft x 40 ft
CONDITIONS OF INSTALLATION:
a. Trench is excavated with' backhoe and trimmed by hand.
b. Before gunite is applied, reinforcing mesh is installed.
c. Edgeforms are not required.
PRODUCTION QUANITITIES AND RATES:
a. Backhoe excavates at a rate of 3 cy/hr or 20 linear ft/hr
b. Trimming ditch required 1 m-hr per 20 sf or 3 linear ft.
Mesh is placed at same rate.
c. 3 in. of gunite is applied at a rate of 1 cy/hr.
TABLE A-4
CONCRETE CHUTE
COST ESTIMATE MATERIAL LABOR EQPT
40 ft length
Excavation:
Backhoe 14 hrs @ $10/hr 140
Operator 16 hrs @ $ll/hr 176
Laborer 16 hrs @ $8/hr 128
Trim: Laborer 8 hrs @ $8/hr 64
Place Mesh: 2 Trimworkers
8 hrs @ $ll/hr 88
Gtmite: 240 sf @ $1.50/sf 360
Subtotal 360 456 140
18% Labor OH 82
25% OH & Profit 90 135 35
Total $450 $673 $175
Unit Costs
$ 1298 _ . . Cost If $ 11.25 $ 16.83 $ 4.38
40 If *•"•«/•" Cost 8f 1<88 2 8Q ?3
145
-------
Diversion Dike
CONDITIONS OF INSTALLATION:
a. No access for trucks - use small tracked front end loader.
b. Compaction by loader trucks and hand rammer.
c. Fill material available within 200 ft of dike.
d. Assume labor is available on job site and no travel time is
required for labor.
PRODUCTION QUANTITIES AND RATES:
a. Volume/linear ft. = 0,277 cy + 257o waste and compaction
= 0.35 cy/lf.
b. Job size = 15 cy or 15/0.35 = 43 If dike.
c. Loader can place and compact 15 cy of material in 3 hr
+ 1 hr travel.
d. 2 laborers shaping and compacting for 3 hr.
TABLE A-5
DIVERSION DIKE
SAMPLE COST ESTIMATES:
COST ESTIMATE
Equipment Rental
Loader 4 hrs @ $9.00/hr
Rammer 3 hrs @ $2.00/hr
LABOR EQPT
36
6
Labor
Loader Op - 4 hrs @ $11.00/hr 44
2 Laborers - 6 m-hr @ $8.00/hr/ m-hr 48
SUBTOTAL 92 42
45% OH & Profit
(small jobs) 41 19
TOTAL COST 133 61
Cost/If $3.09 $1.42
Unit Cost
Cost/If of Dike = 194 = $4.51/lf
43
Cost/cy - 194 = $12.93/cy
15
146
-------
Erosion Check
CONDITIONS OF INSTALLATION:
a. Manual labor is employed to excavate trench, place mat, and
backfill trench.
b. No travel is required for labor.
PRODUCTION QUANTITIES AND RATES:
a. 2 laborers can excavate 1 cy/hr or 6 cy/day (152 If/day).
b. 2 laborers can place jute mesh and backfill at same rate
(152 If/day).
c. One roll of jute mesh, 48 in. x 225 If will cover 225 If of
check. Estimate is for 152 If of jute.
TABLE A-6
EROSION CHECK
SAMPLE COST ESTIMATE:
COST ESTIMATE MATL LABOR EQPT
152 If
Furnish Jute
$45 r 225 If = $.20/lf
152 If x $.20/lf = 30
Labor
4 Laborers - 32 m-hr @ $8.00/hr 256
1 Foreman 8 hrs @ $9.00/hr 72
SUBTOTAL 30 328
18% Labor OH 59
25% OH & Profit 8 97
Unit Cost
<55OO
?->-^
152
TOTAL 38 484
COST/lf $.25 $3.18
147
-------
Filter Berm
CONDITIONS OF INSTALLATION:
Filter berms are to be placed across construction roads. Gravel
shall be delivered to site with one laborer tail-gating and
another laborer spreading.
PRODUCTION QUANTITIES AND RATES:
a. Volume = 0.417 cy + 25% wastage
= 0,520 cy/lf
b. Job size = 30 cy or 30/0.52 = 58 If
c. Two laborers can tail-gate and spread 30 cy of gravel in
4 hr.
TABLE A-7
FILTER BERM
SAMPLE COST ESTIMATE:
COST ESTIMATE MATL LABOR
Labor
2 Laborers 8 hrs @ $8.00 64
Material
Deliver 30 cy Gravel @ $5.20/cy 156
Subtotal 156 64
45% OH & Profit (small jobs) _ 70_ 29
Totals $226 $93
Cost/If $3.90 $1.60
Unit Costs
= *5-50/1£
148
-------
Flexible Downdrain
CONDITIONS OF INSTALLATION:
Flexible downdrain is attached to existing culvert and staked
at 20 ft. intervals on side of slope.
PRODUCTION QUANTITIES AND RATES:
Two laborers work 4 hrs to install 300 ft. of flexible downdrain.
TABLE A-8
FLEXIBLE DOWNDRAIN
SAMPLE COST ESTIMATE:
COST ESTIMATE MATL LABOR
Material
Flexible downdrain
300 ft of 24-in. dia @ $4.85/ft. $1455
Labor
2 laborers 8 hrs @ $8000/hr $64
Subtotal $1455 $64
45% OH & Profit 655 29
Total $2110 $93
Cost/If $7<03 $.31
Unit Cost
$2203 _ ,
300 If" $7-34/lf
149
-------
Flexible Erosion Control Mats
CONDITIONS OF INSTALLATION:
a. Grade stream bed, sew mats together and place on stream bed,
and finally inject mortar into mats.
b. Rate of installation can be controlled by the number of con-
crete pumps used simultaneously.
PRODUCTION QUANTITIES AND RATES:
a. Channel is 25 ft wide and 0.25 mi. long, or 1320 ft x 25 ft =
33,000 sq. ft. Mat is 4 in. thick.
b. Grade with bulldozer @ 250 sq. yd/hr.
Laborer installs mat @ 60 sq. ft/ m-hr
150
-------
TABLE A-9
FLEXIBLE EROSION CONTROL MATS
SAMPLE COST ESTIMATE:
COST ESTIMATE MATL LABOR EQPT
Material
1) Flexible fabric form
@ $0.38/ft2 x 33,000 ft2 = 12,540
2) Grout - assuming 3/8 in0
aggregate ready mix-
delivered @ $19/cy with
107o wastage.
$.26/ft2 x 33,000 8,580
3) Form stakes etc0
@ $0.03/ft2 x 33,000 990
Labor
D4 Dozer operator @ $ll/hr x
(15 hrs work and 1 hr travel) 176
Installing material
= 55° m-hr @ $8-°°/hr 4>4°°
Pumping mortar
33.QOOft2xQ.333ft/27ft3/yd3x$64/m/day
75 yd^/5 m/day i
Cleaning & Misc
33.000 ft2 „„,,
$8/hr 293
900 ftz/m-hr
Equipment
D4 Dozer @ 8 + 2 hr x $16/hr 160
Concrete pump $10/hr @ 70% eff.
$0.03/ft2 x 33,000 ft2 990
SUBTOTAL 22,110 6,606 1,150
18% labor OH 1,189
25% OH & Profit 5^530 1.949 290
TOTAL $27,640 $9,744 $1,440
Cost/sq. ft $0.84 $0.30 $0.04
Unit Cost .. $38,824 <- ,.
$33,000 * '
151
-------
Gabions
CONDITIONS OF INSTALLATION:
a. Access roadway is constructed to stream bed on large jobs.
bo Stream bed is first graded by a dozer.
c. Laborers assemble and wire together gabions.
d. Gabions are filled with 4 in. - 10 in. diameter stone by
clamshell or front end loader.
e» Gabions are finally wired shut by laborers
PRODUCTION QUANTITIES AND RATES:
a. Three estimates are prepared for 1-ft deep gabions:
(1) 10 sq. yd
(2) 100 sq. yd
(3) 1000 sq. yd
b. Bulldozer production rate is 250 sy/hr.
c. Gabions are filled by hand at a rate of 0.3 cy/m-hr and by a
front end loader at a rate of 10 cy/hr.
d. Gabions are assembled at a rate of 3 sy/m-hr.
152
-------
TABLE A-10
GABIONS
SAMPLE COST ESTIMATE:
COST ESTIMATE MATL
10 sy
Material
Gabions 5 @ $7.60 38
Gravel 4 cy (9 $5.75 23
Labor
Grade Area - 4 m-hr @ $8.00/hr
Assemble Gabions 3 m-hr @
$8.00/hr 10/3 = 3.33 m-hr
Fill Gabions:
f^~ = 11 m-'hr @ 8.00/hr
U • j
SUBTOTAL $ 61
45% OH & Profit 27
TOTALS $ 88
Cost/sy $8.80
Unit Cost
$301/10 = $30.10/sy
100 sy
Road to Site and Grading
1 Tractor OP 8 hrs @ 11.00/hr
1 Bulldozer D4 9 hr @ $10.00/hr
1 Laborer 8 hrs @ $8.00/hr
Material
Gabions 33 @ $10.60 349
Gravel 35 cy @ $5.75 201
Labor
Assemble Gabions
100 sy/3 sy/m-hr = 33 m-hr @ $8.00/hr
Fill Gabions
3+1=4 m-hr @ $11.00/hr
Eqpt
F/E Loader: 4 m-4ir @ $14.00/hr
SUBTOTAL $550
187o Labor OH
257o OH & Profit 138
TOTAL $688
Cost/sy $6.88
LABOR
32
27
88
$147
66
$213
$21.30
88
64
264
44
$460
83
136
$679
$6.79
EQPT
90
56
$146
36
$182
$1.82
153
-------
TABLE A-10 (Cont'd)
GABIONS
COST ESTIMATE
MATL
LABOR
EQFT
100 sy (cont'd)
Unit Cost
$1,549/100 = $15.49 sy
1000 sy
Road to Site (see above)
Material
Gabions 250 @ $12.80
Gravel 350 cy @ $5.75
Labor
Grading 1000/250 = 4 + 1 hr
travel = 5 hrs
Fill Gabions 333/10 = 33 +
3 hrs travel = 36 hrs
Assembly 1000/3 + 333 m/hr
Tractor OP - 5 hrs @ $11.00/hr
Loader OP - 36 hrs @ $11.00/hr
Laborers - 333 m^hr @ $8.00/hr
1 Foreman - 40 hrs @ $9.00/hr
Eqpt
D4 Dozer 5 hrs @ $10/hr
F/E Loader 36 hrs @ $14/hr
SUBTOTAL
187o OH
25% OH & Profit
TOTAL
152
90
3200
2013
55
396
2664
360
Cost/sy
$5213
1303
$6516
$6.51
$3627
653
1070
$5350
$5.35
50
504
$644
$0.81
Unit Cost
12, 671 AIT r-i I
-1^000= $12.67/sy
154
-------
Level Spreader
CONDITIONS OF INSTALLATION:
a. Work done where access by truck is impossible.
b. Excavate with bulldozer'and make compacted berms at edge of
ditch with excavated material.
c. Travel time required only for equipment.
PRODUCTION QUANTITIES AND RATES:
a. Lengths of level spreader under consideration:
(1) 15 ft
(2) 44 ft
(3) 78 ft
b. D4 Dozer can construct 40 ft of level spreader per hour plus
1 hr travel time-
155
-------
TABLE A-11
LEVEL SPREADER
SAMPLE COST ESTIMATE:
COST ESTIMATE MATL
15 ft Length
Tractor OP 1% hrs @ $11.00/hr
Laborer 1 hr @ $8.00/hr
D4 Dozer 1-1/2 hrs @ 8 + 2/hr
SUBTOTAL
45% OH & Profit
TOTALS
Cost/If
Unit Cost:
57/15 = $3.80/lf
44 ft Length
Tractor OP 2 hrs @ $11.00/hr
Laborer 2 hrs @ $8.00/hr
D4 Dozer 2 hrs @ 8 + 2/hr
SUBTOTAL
45% OH & Profit
TOTALS
Cost/If
Unit Cost:
84/44 = 1.91/lf
78 ft Length
3 hrs @ $11.00, $8.00, $10.00/hr
SUBTOTAL
45% OH & Profit
TOTALS
LABOR
16
8
$ 24
11
$ 35
$2.33
22
16
$ 38
17
$ 55
$1.25
33
24
$ 57
26
$ 83
EQPT
15
$ 15
7
$ 22
$1.47
20
$ 20
9
$ 29
$0.66
30
$ 30
14
$ 44
Unit Cost:
127
78
Cost/If $1.06 $0.56
= $1.63/lf
156
-------
Sandbag Barrier
CONDITIONS OF INSTALLATION:
Sand is dumped at site, and laborers fill sand bags and place them
into position.
PRODUCTION QUANTITIES AND RATES:
a. Four laborers fill and place 30 sacks per hr for 6 hr per
work day.
b. With 20 percent wastage, quantity of sand required for one
day's work is 5.4 tons.
TABLE A-12
SANDBAG BARRIERS
SAMPLE COST ESTIMATE:
COST ESTIMATE
Sand - 5.4
Sacks - 180
1 Foreman 8
4 Laborers
tons @ $4
@ $0.198
hrs
-------
Sectional Downdrain
CONDITIONS OF INSTALLATION:
a. Excavate with backhoe where accessible, and/or by hand.
b. Grade bed, place pipe, and backfill by hand.
c. A stone bed is placed at lower end of downdrairi for erosion
protection.
PRODUCTION QUANTITIES AND RATES:
a. Backhoe can excavate 3 cy or 27 If of ditch, per hr.
b. Hand Labor:
Hand Grading 8 If/m-hr
Pipe Bedding &
Placing Pipe 8 If/m-hr
Backfill & Tamp 8 If/m-hr
Overall 2.67 If/m-hr
c. Cost estimates have been prepared for 40 ft and 234 ft lengths
of sectional downdrain with a diameter of 24 in.
158
-------
TABLE A-13
SECTIONAL DOWNDRAIN
SAMPLE COST ESTIMATE:
COST ESTIMATE MATL
40 ft Length - 24 in. Diameter
Backhoe: 1 hr Travel
(Case 530) 2 hr Work
3 hrs @ $10/hr
B/hoe Operator: 3 hrs @ $ll/hr
24" Pipe 40 If @ $2.00/lf 80
Pipe Layer: 1 Foreman, 8 hrs
& $9/hr
2 Laborers, 16 hrs @ $8/hr
Apron:
Excavation: 4 m/hr @ $8/hr
Furnish Rock: 1 cy @ $6/cy 6
Place Rock: 4 m/h @ $8/hr
SUBTOTAL $ 86
18% Labor OH
257o OH & Profit 21
TOTAL $107
Unit Cost: C°St/lf $2'68
$$& = 14.55/lf
234 ft Length - 24 in. Diameter
Backhoe: 9 hrs
1 hr travel
LABOR
33
72
128
32
32
$297
53
87
$437
$10.93
EQPT
30
$ 30
8
$ 38
$0.95
10 hrs @ $10/hr 100
Operator: 10 hrs @ $ll/hr 110
Pipe 234 If: @ $2.04/lf 477
Pipe Layer:
1 Foreman 40 hrs @ $9.00/hr 360
4 Laborers, 88 m/hr @ $8.00/hr 704
Apron: 6 64
SUBTOTAL $483 $1,238 $100
187o Labor OH 223
257. OH & Profit 121 365 25
TOTAL $604 $1,826 $125
Cost/If $2.58 $7.80 $0.53
Unit Cost:
= $10.91/lf
159
-------
Sediment Retention Basin
CONDITIONS OF INSTALLATION:
a. Due to possible extreme differences in topography, basin area,
and dam configuration, examples of different dam sizes and not
basin areas are presented here.
b. The procedure for dam construction includes the following steps:
(1) Strip top 6 in. of soil at dam foundation and in retention
basin with dozer and dispose of in trucks. Strip second
6 in. of soil and use for dam construction.
(2) Place spillway pipe and hand backfill around pipe.
(3) Dozer excavates suitable dam material in area and stock-
piles it for loading into trucks and haul to dam.
(4) Trucks dump material on dam. ' Dozer spreads and compacts.
PRODUCTION QUANTITIES AND RATES:
a. Following is a table presenting dimensions and quantities of mate-
rial used for estimating costs of three different sized dams:
QUANTITIES
Case
A
B
C
Dam Ht
and Length
6'H x 30'L
7'H x 30'L
8'H x 40'L
Cubic Yard
Stripping
(cy)
266
340
570
Length and Size
Spillway Pipe
40' -6" , 5 '-12"
44'-12" , 6'-18"
48 '-12" , 7 '-18"
Dam Fill
(cy)
133
170
285
Cubic Yard
Riprap
(cy)
3
3
3
b. The following list shows the production rates involved in
constructing the dams:
D4 Dozer Stripping
1-1/4 CY F/E Loader:
D4 Dozer Spread & Compact:
Place Spillway Pipe:
Hand Backfill:
100 cy/hr
36 cy/hr
30 cy/hr
5 If/m-hr
6 If/m-hr
160
-------
TABLE A-14
SEDIMENT RETENTION BASIN
SAMPLE COST ESTIMATE:
COST ESTIMATE MATL LABOR EQPT
6 ft x 30 ft
Stripping & Stockpiling
1 D4 Tractor 4 hrs @ $10.00/hr 40
Tractor Operator 4 hrs @
$11.00/hr 44
922 Loader 4 hrs @ $14.00/hr 56
2, 6 cy Trucks 8 hrs @
$12.00/hr 96
Loader Operator 4 hrs @
$11.00/hr 44
2 Truck Drivers 8 hrs @
$9.00/hr 72
Place & Backfill Pipe
Labor: 9 m-hr place
8 m-hr Backfill
17 m_hr @ $8.00/hr 136
Pipe: 40 If @ $1.45 If +
5 If @ 3.85/lf 77
Seepage barriers lump sum 10
Fill & Riprap
D4 Tractor 6 hrs @ $10.00/hr 60
Tractor Operator 6 hrs @
$11.00/hr 66
Loader 5 hrs @ $14.00/hr 70
Loader Operator 5 hrs @
$11.00/hr 55
2, 6 cy Trucks 10 hrs @
$12.00/hr 120
2 Truck Drivers 10 hrs @
$9.00/hr 90
3 Laborers, 24 hrs @ $8.00/hr 192
1 Foreman, 8 hrs @ $10.00/hr 80
Riprap 3 cy @ $6.00/cy _ 18 _ _
SUBTOTAL $105 $779 $442
18% Labor OH
25% OH & Profit
TOTAL
Cost/cy $0.98 $8.64 $4.16
Unit Cost
= $13.78/cy
161
-------
TABLE A-14 (Cont'd)
SEDIMENT RETENTION BASIN
SAMPLE COST ESTIMATE:
COST ESTIMATE
MATL
LABOR
EQPT
B. 7 ft x 30 ft
Stripping & Stockpiling
Same as Above + 25%
Place & Backfill Pipe
Labor: 10 m-hr Place
8 m-hr Backfill
18 m-hr @ $8.00/hr
Pipe: 44 If @ $3.17/lf +
6 If @ 5.60 If
Seepage Barriers
Lump Sum
Fill and Riprap
D4 Dozer 6 hrs @ $10.00/hr
1 Dozer Operator 6 hrs @
$11.00/hr
F/E Loader 5 hrs @ $14/hr
1 Loader Operator 5 hrs @
$11.00/hr
2, 6 cy Trucks 10 hrs @
$12.00/hr
2 Truck Drivers 10 hrs @
$9.00/hr
3 Laborers 30 hrs @ $8.00/hr
1 Foreman 10 hrs @ $10.00/hr
Riprap 3 cy (§ $6.00/cy
SUBTOTAL
18% Labor OH
25% OH & Profit
TOTAL
200
240
144
177
10
Unit Cost
2.189
170
Cost/cy
= $12.88/cy
18
$205
$1.51
66
55
90
240
100
895
161
264
60
70
120
$1,320
$7.76
$490
$3.61
162
-------
TABLE A-14 (Cont'd)
SEDIMENT RETENTION BASIN
SAMPLE COST ESTIMATE:
COST ESTIMATE
MATL
LABOR
EQPT
C. 8 ft x 40 ft
Stripping & Stockpiling
(Same as A Above
+ 100%)
320
384
C. 8 ft x 40 ft (Cont'd)
Place & Backfill Pipe
Labor: 11 ra-hr Place
8 m-hr Backfill
19 m-hr
-------
Straw Bales
Storm Sewer Inlet Protection
CONDITIONS OF INSTALLATION:
Site surrounding inlet is graded and then straw bales are placed
around inlet and staked by laborers.
PRODUCTION QUANTITIES AND RATES:
a. Seven bales of straw are used per inlet; however, the number of
bales used will vary with the inlet configuration.
b. A 2-man crew can place and stake one bale in 10 min., or 3 bales
per m-hr per 7-hr work day.
TABLE A-15
STRAW BALE INLET PROTECTION
SAMPLE COST ESTIMATE:
COST ESTIMATE
MATL
LABOR
EQPT
Straw
Cost $30/ton
20 bales/ton 1.50/ea
Stakes 2 @ .25 .50
2.00
For 3 Inlets (21 Bales)
21 Bales (? $2.00/bale in place
Q = 7 + 2 (travel) = 9 m-hr
@ $8.00 =
SUBTOTAL
45% OH & Profit
TOTAL COST
Cost/Bale
Unit Cost
Per Bale:
Per Inlet:
—•
= $7.86
= $55
42
$ 42
19
$ 61
$2.90
None
72
$ 72
32
$104
$4..96
164
-------
Straw Bale Barriers
CONDITIONS OF INSTALLATION:
Similar to that for storm sewer inlet protection; however, a gravel
wier must also be installed.
PRODUCTION QUANTITIES AND RATES:
Production quantities and rates are the same as for storm sewer inlet
protection.
TABLE A-16
STRAW BALE BARRIERS
SAMPLE COST ESTIMATE:
COST ESTIMATE MATL LABOR EQPT
Unit Cost Per Bale
From Inlet Protection = $7.86
For each barrier there will be a
gravel weir, 6 ft x 4 ft x 8 in. =
16 cf
Per Barrier
16 cf 2700 A 0 fc
~27~~ x 2000 = °'8 tons
0.8 x $4.00/ton 3.20
Shaping Weir: 0.5 m-^hr 4.00
SUBTOTAL $3.20 $4.00
457» OH & Profit 1.44 1.80
TOTAL per weir $4.64 $5.80
Unit Cost
10.44/Weir + (No. of Bales) x $7.86
165
-------
II -
PROTECTION OF GROUND SURFACE
TABLE A-17
EXCELSIOR MAT
One-Acre Plot
California
MATL
LABOR
EQPT
1. Excelsior rolls (3 ft x 150 ft)
$16.00/roll
2. Fertilizer
3 . Seed
4. Light application of Fibermulch
5. Hydroseeder labor
6. Excelsior labor 96.8 rolls x
8 hr x $8.00
1,550
24
52
112
220
6,195
7.
8.
9.
Transportation
Equipment
Move -in & Move -out
Round off to
SUBTOTAL $1,738
18% labor OH
25% OH & Profit 435
Cost/ac $2,173
Overall Cost/ac
128
$6,543
1,178
1,930
$9,651
$12,186
$12,200/acre
50
120
120
$290
72
$362
166
-------
TABLE A-18
JUTE MESH. ONE-ACRE PLOT
(Steep Slope)
(Ludlow Soil Saver)
(41 x 225' roll)
California
MATL
LABOR
EQPT
1. Ludlow Soil Saver with 6-in.
overlap on all edges gives 787
sq ft/roll
*fgP x $30/roll
2. Staples 225/roll
x 225 x $15/1000 staples
15 Ib
1,660
187
3. Fertilizer
4. Seed 200 Ib/acre x:
1000 sq ft
$26
100 Ib
5. Fiber Mulch
24
52
113
6. Hydroseeder & mesh labor
2 men x 4 hrs x $8
($43,560-r 787) 6 hr/roll x $8
7. Transportation
8. Rental 4 hrs @ $30/hr
9. Move-in & Move-out
% x 2 x 8 x $8
2 x 8 x $8
% x 8 x $30
10. Labor Supervision
64
2,657
64
128
340
50
120
120
su
SUBTOTAL
187= Labor OH
25% OH & Profit
Cost/acre
Overall Cost/acre
$2,036
509
$2,545
$3,253
585
960
$4,798
$7,706
$290
73
$363
Round off to
$7,700/acre
167
-------
TABLE A-19
STRAW OR HAY
10-acre plot
California
MATL
LABOR
EQPT
1. Straw (§ 4 tons/acre applied in two
layers with each layer incorporated
into soil by a modified sheepfoot
roller (cultipacker).
4 tons/ac x 10 ac x $30/ton
2. Seed and fertilizer
3. Labor 4 tons/man day
8 (40 tons -»• 4) $10
4. Labor for punching straw with
cultipacker
8 (10 acres + 2% ac/man day) x $10
done twice
5. Rentals
Cultipacker - 8 days x 8 hr x
$25/hr
Blower - 10 days x 8 hr x $25/hr
6. Transport
7. Move-in & move-out
(2 x 4 x 8 x $10)
(2 x 8 x $25) 2
8. Labor Supervision
1,200
800
640
640
245
1,600
2,000
200
800
Round
SUBTOTAL
18% Labor OH
25% OH & Profit
Cost /Ac
Overall Cost/Ac
off to
$1,960
490
245
$2,325
418
686
343
$1,163
$l,200/acre
$4,600
1,150
575
168
-------
TABLE A-20
WOODCHIPS
3-in Cover Over One Acre
California
MAIL
LABOR
EQPT
1 . Wood chip
43,560 x
x $4.00/cyr
1,612
2» Labor for spreading
(43,560 x T x -^f)-*- 2 cy/m/hr x
$8.00 =
3. Rental
5 days 8x2 trucks @ (9.63 +
9.00) =
4. Move-in & Move-out
2 (5 men x 8) x $8
2x8x2x9.63
5. Labor supervision
1,612
640
265
1,490
380
Round
SUBTOTAL
18% Labor OH
25% OH & Profit
Cost/Ac
Overall Cost/ac
off to
$1,612
403
$2,015
$2,517
453
743
$3,713
$7,976
$8,000/acre
$1,798
450
$2,248
169
-------
TABLE A-20 (Cont'd)
WOODCHIPS
3/4 in. Cover with Seed and Fertilizer
One Acre in California
California
MAIL
LABOR
EQPT
1. Woodchips:
43,560 x
x
x $4/cy
402
2. Fertilizer:
15 Ib 43,560 ,,_/fc
- x $72/ton
looo
ft
24
3. Seed:
200 Ib/ac x
$26
100 Ib
52
4. Labor:
Hydroseeder 2 x 4 x $8
Chip spreading $8 (43,560 x
12 27
5. Rentals:
1% days x 8 x 2 trucks @ (9.63 +
$9.00)
4 hrs x $30 for hydroseeder
6. Transportation
7. Move- in and Move -out:
% day x 2 men x 8 hr x $8
1 x 5 x 8 x $8
2 x 1 x 8 x $9.63
% x 8 x $30
8. Labor Supervision
SUBTOTAL $478
18% Labor OH
25% OH and Profit 120
Cost Per Ac $598
Overall Cost Per Acre
64
402
64
320
100
950
171
280
$1,401
$3,113
447
120
50
154
120
$891
223
$1,114
Round off to
$3,10()/acre
170
-------
TABLE A-21
4-in. SQUARE PLUGS OF SOD
@ 12 in. c/c
One Acre Plot
California
MAIL
LABOR
EQPT
1. 4-in square plugs of sod set
@ 12 in. c/c both directions
43.560 sq ft ., / n
•=—*•= *• • x l%£/plug
1 plug sq ft v v 5
2. Fertilizer
3. Precultivation & Soil prepara-
tion complete @ 4c/sq ft
4. Labor for setting
(43,560-4- 120 sq ft/m/hr) $8
5. Establishment expenses
Water applied by portable
sprinkler system @ $750/ac/month
653
24
2,904
1,743
6.
7.
x 3 mos
Move -in & Move -out
Labor Supervision
SUBTOTAL
18% Labor OH
25% OH & Profit
Cost Per Acre
Overall Cost /Ac
Round off to
128
354
$677 $3,386
609
170 999
$847 $4,994
$11,332
$ll,300/acre
2,250
400
$4,393
1,098
$5,491
171
-------
TABLE A-22
SODDING
Hybrid Bermuda Grass Blanket Sodding
One-Acre Plot
California
MAIL
LABOR
EQPT
1. Hybrid Bermuda Grass 16 in. wide
strips
43,560 sq ft @ 12c/sq ft delivered 5,227
2. Fertilizer
3. Labor for laying sod
(43,560 sq ft •+• 250 sq ft/m/hr)
x $8
(allow 400 sq ft/m/hr)
(for level or flat slope land)
4. Precultivation & soil preparation
complete @ 4c/sq ft
43,560 x 4c
(range 3 to 5c/sq ft)
5. Establishment expenses
Water applied by watertruck
24
1,394
1,742
6.
7.
@ $800/ac/month x 3 months
Move -in and Move -out
Labor Supervision
SUBTOTAL $5,251
Labor
25% OH & Profit 1,313
Cost/Ac $6,564
Overall Cost/Ac
128
178
$1,700
306
502
$2,508
$14,750
2,400
400
$4,542
1,136
$5,678
Round off to
$14.,800/acre
172
-------
TABLE A-23
CHEMICAL SOIL STABILIZER - PETROSET SB
STANDARD OPERATION - NO FUMIGATION
10 Acres
California
Material Labor Equip't
1) Petroset SB. Rainwater Erosion
protection on Intermediate Grain
soils; 1:7 Dilution Ration of SB:
Water; 1/2" penetration depth:
Dilution
Application Rate of Diluted
Solution =0.5 gal/sq yd
3025 gals of SB @ $2.50/gal.
2) Fertilizer (same as for Wood Fiber
Mulch)
3) Seed (same as for Wood Fiber Mulch)
4) Hydroseeder labor, for sloping ground,
application rate = 0.5 ac/hr/2-man crew,
total time - 20 hrs. 2 x 16 hr x $10 +
2 x 4 hr x $15 (overtime rate)
5) Transport: Hydroseeder, 2 hr x $25
6) Rentals: Hydroseeder 20 hrs x $30
7) Move-in & Move-out
2 x 2 x 8 x $10
2 x 8 x $30
8) Labor supervision
Subtotals
18% for Labor Overhead
25% for Overhead & Profit
Grand Total
Cost Per Acre
Overall Cost per Acre
•7,563
235
520
440
50
600
320
90
480
$8,318
2,079
$850 $1,130
153
251 283
$10,397 $1,254 $1,413
$1,040 $ 125 $ 141
$1,306
Round off to
$l,300/acre
173
-------
Ill - REMOVAL OF SEDIMENT
From Streets and Basements
PRIMARY USAGE:
Removal of sediment from streets and basements is employed in
areas where surface runoff has left deposits of sediment in
these areas.
DESCRIPTION:
Sediment accumulation on streets and in basements can render both
of these areas unusable.
For sediment removal from streets, a front-end loader and a dump
truck can be employed to deposit the sediment in an acceptable
location. For sediment removal from basements, hand labor can
remove the sediment from the basement, at which point a dump truck
can transport it to the disposal area.
174
-------
From Streets
CONDITIONS OF REMOVAL:
A front-end loader scrapes sediment from street and loads the
material into 6 cy dump truck for ultimate disposal. A broom is
used for final cleaning of street.
PRODUCTION QUANTITIES AND RATES:
A front-end loader operates at a rate of 18 cy/hr or 3 truck loads
per hour. In 6 hours, 108 cy can be removed, or 648 sq. yd. with
a depth of 6 in.
TABLE A-24
SEDIMENT REMOVAL FROM STREETS
SAMPLE COST ESTIMATE:
COST ESTIMATE LABOR EQPT
Eqpt Rental
1, F.E Loader (Cat 922) - 8 hrs. @ $11.50/hr 92
2, 6 cy Trucks - 16 hrs. @ $10.25/hr 164
Labor
~1 Foreman - 8 hrs.@ $9.00 72
1 Loader Op - 8 hrs. @ $11.00 88
2 Truck Drivers - 16 hrs @ $9.00 144
1 Laborer - 8 hrs. @ $8.00 64
Subtotal 368 256
18% Labor OH 66
25% OH & Profit 109 64
Total $543 $320
Cost/cy $5.03 $2.96
Production
6 hrs @ 18 cy/hr = 108 cy
<§ 6" depth = 648 sq. yd
*fij|-17.99/c,
@ 6" Depth
$1.33/sq. yd
175
-------
From Basements
CONDITIONS OF REMOVAL:
Laborers first load basement sediment into wheel barrows, then
material is dumped onto a conveyor for removal from the basement.
Once outside the building, sediment is loaded by a front-end
loader into a dump truck for disposal.
PRODUCTION QUANTITIES AND RATES:
a. Production rate is limited by rate at which laborers work.
Two laborers can each load 6 wheel barrow loads per hour for
6 hrs per day or 36 wheel barrows @ 3cf = 4cy/day (with one
laborer operating wheel barrow)
b. The example is for one day's work with 3 laborers plus one fore-
man.
TABLE A-25
SEDIMENT REMOVAL FROM BASEMENTS
SAMPLE COST ESTIMATE:
COST ESTIMATE (PER DAY) LABOR EQPT
Labor
3 Laborers - 24 m/hr @ $8.00/hr
1 Truck Driver 3 hrs @ $9.00/hr
1 Loader Op 3 hrs @ $11.00/hr
1 Foreman 8 hrs @ $9.00/hr
192
27
33
72
Eqpt
1 Conveyor 8 hrs @ $4/hr = 32
1 F/E Loader 3 hrs @ $14/hr 42
1 6 cy Truck 3 hrs @ $12/hr 36
Subtotal 324 110
18% Labor OH 58
25% OH & Profit 96 28
Total 478 138
Cost/cy $59.75 $17.25
Unit Cost
$616 ..,-,,
*-j- = $77/cy
@ 6" Depth - ™ = $1.43/sq.ft
176
-------
From Storm Sewers
PRIMARY USAGE:
This practice is used in areas where storm sewers collect surface
runoff from construction sites and sediment carried by the runoff
can eventually clog the sewer. Two methods of storm sewer cleaning,
bucket line cleaning and rodding with vacuuming, are presented in
this study.
DESCRIPTION:
Using a bucket line is a method by which buckets are pulled by a line
between two manholes in the sewer, thus removing the debris from
one manhole. A bucket line normally requires four laborers.
The second method of cleaning entails xpdding and cleaning with a
unit such as the Vactor . The Vactor is a truck mounted unit which
combines both the features of rodding and vacuuming. These two
processes operate simultaneously using one manhole. Rodding is the
spraying of water at a high velocity through a special nozzle, in
the storm sewer. As the rodder moves through the sewer, the sedi-
ment is flushed back towards the manhole, at which point the vacuum
removes the water and sediment from the manhole and stores it in the
truck. This operation requires the Vactor , one operator, and one
laborer.
177
-------
Bucket Line Cleaning
CONDITIONS OF INSTALLATION:
Four laborers operate the 'bucket line, loading the material into a
dump truck.
PRODUCTION QUANTITIES AND RATES:
A storm sewer, 300 ft long with 24 in diameter, is approximately
one half full with from 2-1/2 to 3 in rocky shale and gravel. The
total quantity of material to be removed is 17.5 cy. The task re-
quires 4 laborers, 4 days.
TABLE A-26 '
BUCKET LINE CLEANING
SAMPLE COST ESTIMATE:
COST ESTIMATE MATL LABOR EQPT
Equipment
One .6 cy dump truck @ $7/hr x 32 hrs 224
One dray bucket @ $60/day x 4 days 240
Labor
4 laborers @ $8/hr x 32 hrs ea. 1024
1 truck driver @ $9/hr x 32 hrs 288
Subtotal $1312 $464
18% labor OH $ 236
25% OH & Profit $ 387 $116
Total $1935 $580
Unit Cost
$ m $ 33
178
-------
Rodding and Hydraulic Flushing of Storm Sewer
CONDITIONS FO INSTALLATION:
T>
One laborer and operator are required for using a Vactor to
rod and hydro-flush the storm sewer. Periodically the Vactor
must be refilled and its sediment load dumped.
PRODUCTION QUANTITIES AND RATES:
The task consists of cleaning a storm sewer, 24 in diameter by 250
ft long, which is 28 percent filled with debris. Material to
be removed consists of rocky shale and gravel, of approximately
2-1/2 to 3 in.size. Eight cubic yards of material must be removed,
the job requires a one-day use of the Vactor
TABLE A-27
RODDING & HYDRAULIC FLUSHING FROM STORM SEWER
SAMPLE COST ESTIMATE:
COST.ESTIMATE EQPT LABOR
Equipment
Vactor 800* @ $240/day $240
Fuel 14
Labor
Vactor operator @ $ll/hr x 8 88
Laborer @ $8/hr x 8 64
Subtotal $254 $152
16% Labor OH $ 27
25% Office OH & Profit $ 63 $ 45
Total $317 $224
Unit Cost
= $68/cy $ 40 $ 28
* Unit is leased and travel distance less than 100 miles
179
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APPENDIX B
PART 1 - HYDROLOGIC ASPECTS OF THE UNIVERSAL SOIL LOSS EQUATION
1. THE ARS "UNIVERSAL SOIL LOSS EQUATION"
The universal soil loss equation developed by the Agricultural Research
Service is a semi-empirical predictive relationship between the mass of
soil loss per unit area and all major factors known to influence rain-
fall erosion. It has the form:
A = RKLSCP (1)
where: A = the computed soil loss in tons per ac from a given storm
period,
R = the rainfall erosion index for the given storm period
in units of ft-ton in. per ac-hr (described further below),
and K, L, S, G, and P are other important factors which were
defined and discussed briefly in Section VII of this Report.
This appendix sets forth the reasoning and mathematics of the deter-
mination of R, the rainfall erosion index, from basic hydrologic data.
The rainfall factor, R, is the rainfall erosion index reported by
Wischmeier (Reference 135) and defined for a single storm as:
R = TOO <2>
where, E = the total kinetic energy of a given storm in ft-tons per ac
and I is the maximum 30-min rainfall intensity for the area
in in. per hr.
The rainfall factor is thus a composite term, representing the effects
of raindrop impact for the entire storm duration and maximum rainfall
intensity. The kinetic energy of rainfall has been given by Wischmeier
and Smith (Reference 135) as:
E = 916 + 331 Iog10 I (3)
where, I is rainfall intensity (in. per hr). It is thus evident that the
rainfall erosion index can be expressed as a function of rainfall intensity
alone. The rainfall erosion index, 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. The
annual R factors for approximately 2,000 locations in the United States
have been summarized in the form of "iso-erodent" maps by Wischmeier and
Smith (Reference 136). Figure 45 shows an example of such iso-erodent
maps. This reference handbood provides data and figures for estimating
average monthly soil loss in tons per ac per yr from cropland east of
the Rocky Mountains. It also lists 5, 20, and 50 percent probability
values of the erosion index and the expected magnitudes of the single-
storm erosion index values for return periods of 1, 2, 5, 10 and 20 years
181
-------
without specifying the storm duration periods. While the Handbook was
prepared for use in agricultural areas, the methodology and data can be
used for estimating erosion in urban areas and at construction sites
anywhere.
The problems of estimating erosion soil loss in the West, however,
was more difficult since there was no ready source similar to Reference
136 for areas west of the Rocky Mountains available when the studies
for this report were begun in July 1972. In late September 1972, the
SCS provided a copy of their Technical Release No.51 (Reference 105) which
included a tentative guide for application of the universal soil loss
equation to the western area. A curve was presented which enabled the
annual rainfall erosion index to be graphically estimated from the 2-yr
frequency 6-hr rainfall at any particular location. This curve proved to
be a valuable checkpoint, on the relationship between single-storm
erosion indices and annual erosion indices. It was desired, however, to
develop a methodology which would tie together both the eastern and the
western data. Because rainfall energy is the principal criterion for the
rainfall erosion index portion of the soil-loss equation, an analysis of
this aspect was undertaken.
A. Rainfall Erosion Index for Individual Storm Rainfall
Wischmeier and Smith (135) presented an equation describing rainfall kinetic
energy as a function of rainfall intensity. This relationship is given in
Equation (3). In order to compute the total kinetic energy of a given
storm they used the information available from recording raingage charts.
A tabular record of rainfall intensities, with the amount of rain falling
at each of the successive intensity increments was obtained from the re-
corder chart. The kinetic energy for each intensity increment was cal-
culated using Equation (3) and the result was multiplied by the depth
of rain falling at that rate. These partial products were accumulated to
obtain the total energy value for the storm.
Rainfall distribution with respect to time was analyzed using the storm
rainfall distribution curves presented by the Soil Conservation Service
Technical Paper No. 149 (Reference 104). Typical rainfall patterns from
two major regions were identified and time distributions: for each are
presented in Figure 46. Type I is representative of Hawaii, Alaska, and
the coastal side of the Sierra Nevada and Cascade Mountains in California,
Oregon, and Washington. Type II distribution is representative of the
rest of the United States, Puerto Rico and the Virgin Islands. The type
I and II distribution patterns are based on the generalized rainfall depth-
duration relationships given in U.S. Weather Bureau Technical Papers.
Based on the method used and prescribed by Wischmeier arid Smith (Reference
131) and the generalized rainfall distribution curves shown on Figure 46, a
solution for kinetic energy and the erosion index for an individual storm
of 24-hr duration was calculated with the aid of graphical approximations,
for various values of total rainfall, both for Type I and Type II regions.
See Appendix B, Part 2, for details. A plot of the calculated data pro-
duced the following equations for an individual 24-hr duration storm
erosion index.
182
-------
Type I: = 2.176 (P^ ^' (4)
Type II: = 4.365 (P 2'2 (5)
Assuming that the distribution of rainfall against time (as given for
the 24-hr duration and expressed in dimensionless form both for time and
accumulated rainfall) will hold true for any durations, then the erosion
index values can be calculated for various durations and rainfall depths.
Graphical analysis of the calculated data, yielded the following gen-
eralized relationships.
Individual Storm Erosion Index:
Type I: i (30 min max) = 15PQ.6065 (6)
H
r
Type Ils ^ (30 min max) - 19.25 ^46?2
H
r
where: P = storm rainfall in inches
R = duration of rainstorm in hours
r
Figures 50 and 51 present the above two equation in graphic form. This
method of presentation of individual storm erosion index is helpful in
the comparison and evaluation of the erosion index of rainfalls of various
depths and durations.
B. Estimation of Average Annual Erosion Index
With the relationships of intensity, depth, and duration of rainstorms
presented in USWB TP No. 24 (Reference 123) the erosion index values for
rainstorms of different duration but of equal frequency could be easily
plotted on a log-log graph such as in Figures 50 and 51. For a hypothet-
ical station in the west (i.e., in Zone I, which represents an area in
which Type I distribution of rainstorm takes place) the calculated values
of erosion index for 2-yr return periods (i.e., 50 percent probability)
were plotted for rainstorms of 30 min and up to 24-hr duration. These
plots indicated that for Type I rainstorms the individual erosion index
values for 24-hr duration was 9 percent more than that of the 6-hr storm
index while for the Type II rainstorms the 24-hr erosion index was only
6.5 percent more than that of the 6-hr index. Since the variation in
the erosion index values for different rainstorm durations of equal
frequency was not very large, it was argued that the equation for the
individual erosion index could be converted into one for annual erosion
index if one could determine first the most common or frequent rainfall
duration period. The SCS Field Engineering Manual (Reference 100)
presents a graph indicating the relationship between effective duration
(i.e., the most frequently occurring phenomena) and average annual
precipitation.
183
-------
The reasoning that a given rainstorm duration erosion index formula could
be adapted to yield an average annual erosion index is strengthened by
the fact that the sediment yield caused by large storms (with return period
greater than 2 yr) in 72 small watersheds in 17 States Is 20.4 percent of
the total average annual sediment yield, on the average.. . For moderate
storms (with return period between 1 and 2 years) the sediment yield, on
the average, is 10.6 percent of the total average annual yield. Also, for
most watersheds, more than one-half of the soil losses are attributable
to the smaller storms that occur more than once a year on the whole
(Piest, Reference 73). This conclusion is corraborated by Wischmeier
(Reference 131), who concluded that the bulk of the soil loss can be
attributed to the more frequent storms that have at least a 50 percent
chance of occurrence in any given year. Diseker and Sheridan (Reference
25) state that on roadbanks, the five largest storms produce, on the
average, 71.9 percent of the total annual sediment yield. The largest
storm in the group produces an average of 31.3 percent of the total
annual s ed iment.
Such conclusions strengthen the probability that a direct empirical re-
lationship can be developed between a given duration rainstorm of a 2-yr
frequency and annual erosion index. Wischmeier (Reference 131) asserted
that when the data from the original 181 locations were analyzed, a three-
factor product (average annual rainfall times the 2-yr, 1-hr intensity
times the 2-yr, 24-hr intensity) explained 95.4 percent of the total
variation in erosion index values. This correlation technique was used
by Wischmeier to estimate the erosion index for 1,700 additional loca-
tions evenly distributed in 37 States. The 2-yr, 1-hr and 24-hr rainfall
amounts were taken by Wischmeier from the USWB Technical Paper No. 29,
and from similar but unpublished maps. Average annual rainfall data for
each of these locations were secured from USWB Local Climatological Data.
The estimated erosion index values for these 1,700 locations were then
mapped, along with those derived directly from the 181 locations with
22-yr basic rainfall records. The resultant map is the iso-erodent map
presented in USDA Handbook No. 282 (Reference 136) and reproduced in
Figure 45.
Analysis of the USWB proposed rainfall depth-duration diagram Figure 2
in USWB Technical Paper No. 40 (Reference 124) yielded the very interest-
ing and significant result that the 6-hr rainfall depth is the average of
the 1-hr and 24-hr rainfall for any given location in the United States.
This finding proved very encouraging, since the product of 2-yr 1-hr and
2-yr 24-hr could be replaced with the 2-yr 6-hr duration raised to the
second power times a constant (the USWB Technical Paper No. 40 states
that in using their Figure 2 the depth of rainfall for various duration,
but all of the same frequency will plot as a straight line, and as a
corollary, that the PI for a small region can be considered constant.)
^4
The erosion index for a Type II individual storm rainfall of 6-hr duration
is equal to 0 oc._2.2 where P is the 6-hr rainfall depth.
o. Z_)r
184
-------
Close examination of the pattern of the 2-yr 6-hr rainfall map prepared
by the USWB Technical Paper No. 40 and comparison with the pattern of
average annual values of rainfall factor, R, (otherwise known as the
Iso-Erodent Map) which is presented as Figure 1 in USDA Handbook No.
282 reveals that there exists a very strong correlation between the two
maps. After estimating the corresponding individual storm rainfall
erosion indices, the mean ratio of average annual erosion index and
2-yr 6-hr individual storm rainfall erosion index, is calculated at
3.265. This means that the average annual rainfall erosion index is
equal to 3.265. times the 2-yr 6-hr individual storm rainfall erosion
index. Thus, for Type II Storms:
2 2
Average Annual Rainfall Erosion Index = 8.25 x 3.265 x P
= 27P2-2 (8)
Using the values of 2-yr 6-hr rainfall, shown on Figure 6 from the USWB
Technical Report #40, annual erosion index values were calculated and
smoothed iso-erodent lines were drawn onto the USWB 2-yr 6-hr rainfall
map. The results on Figure 49 as compared to the annual iso-erodent
map shown in Figure 45, are almost identical.
This is a strong evidence for the applicability of the SCS rainfall
distribution curve for rainfall erosion energy estimating purposes,
and shows that the estimation of average annual erosion index could be
condensed into a simple formula. This formula fits the data for areas
east of the Rocky Mountains, which are considered to receive Type II
rainstorms only. It is felt that similar reasoning or approach could
be applied to Type I rainstorm areas of the Pacific Coast west of the
Rocky Mountains.
The 6-hr individual rainstorm erosion index for Type I distribution is
found to be 5 _7p2.2. Multiplying this by the factor of 3.265, the
following equation is obtained for Type I storm rainfall distributions.
Type I Storms: Average Annual Rainfall Erosion Index = 16.55P2'2
(9)
As an independent check to confirm the validity of the above relationship
the average annual erosion index for Red Bluff and San Luis Obispo were
calculated from the 2-yr 6-hr rainfall (1.75 and 1.60 in. respectively
from USWB TP No. 40). This resulted in values of 57 and 46 respectively.
Whereas Table 11 of Handbook No. 282 lists the erosion index values of
50% probability for the same locations as 54 and 43 respectively.
In addition, Table 12 of the same handbook lists the expected magnitude
of single-storm erosion index normally exceeded once in 2 years as 21
and 15 respectively. The 2-yr 6-hr storm erosion indexes are estimated
from the formula
FT 9 9
~ 5.07P * at 17.5 and 14.3, respectively.
(Using the 2-yr 24-hr rainfall single-storm erosion index will be
estimated for 2.8- and 2.4- in. rainfall at 20.5 and 15, respectively.)
These two independent checks to corroborate the validity and the accuracy
185
-------
of the empirical formulas were developed in the course of this study.
2. SOIL CONSERVATION SERVICE TECHNICAL RELEASE
In September 1972, the U.S. Soil Conservation Service issued Technical
Release No. 51 (Reference 105), entitled "Procedure for Computing Sheet
and Rill Erosiofl on Project Areas". Use of the universal soil loss
equation was extended by provision of data for additional plant cover
factor (C) for permanent pasturland, rangeland, woodland, and idle land.
Technical Release No. 51 also states specifically that "El factors have
not been evaluated from actual rainfall data in the States comprising
the SCS West Region and to some degree in the Caribbean Area". It goes
on to state that the ARS Soil Loss and Runoff Laboratory has provided
iterim El and R data that may be used where rainstorms of significant
kinetic energies and intensities are common. The interim El or R factors
are presented in graphic form, whereby a direct reading may be obtained
from this graph after the 2-yr, 6-hr rainfall has been determined for the
area involved.
Examination of the values of El or R factors corresponding to given mag-
nitudes of 2-yr 6-hr rainfall indicate that the curve presented in their
Figure 1 of TR No. 51 represented Type II rainfall distribution. In
fact, the curve proved to give results identical to those obtained from
Equation 8, derived by Engineering-Science, Inc., (ES) , from the SCS
Type II Storm S-curve and the rainfall energy equation of Wischmeier, as
has been explained previously. Hence, the curve and the equation are
applicable to all areas in the United States where Type II storms prevail.
On the other hand, the curve gives results too high for Type I storm areas,
according to Equation 9, developed by ES on the same basis of kinetic
energy and storm rainfall intensities. The ES equation Type I values
are about 61 percent of the Tvpe II values. Curves for both storm types
are shown in Figure 47. The El or R values suggested by SCS TR No. 51
will result in El or R values on the conservative side . This in itself
is acceptable if only the relative magnitude of the erosion index were
desired. However, for design purposes, especially for cost considerations,
and for estimation of K-factors from the universal soil loss equation, a
60 percent discrepancy cannot be tolerated.
3. SUMMARY PROCEDURES FOR ESTIMATION OF RAINFALL EROSION INDEX
A. Example 1 Rainfall Erosion Index for a 2-yr 6-hr Storm
This can be considered a typical "average" storm, since it can be ex-
pected to occur 50 percent of the time, and the 6-hr duration has been
found by SCS to be the most frequently occurring storm length.
(1) Locate the area under study on a chart in USWB TP No. 40 (or
similar publication) similar to Figure 48.
(2) Determine the value of the 2-yr 6-hr rainfall from the preceding
chart .
186
-------
(3) Check as to the zone (Zone I or Zone II) in which the area
under study is located.
(4) The storm erosion index can be estimated by either of the
three methods listed below.
(a) Use of the following formulas :
Type I: - 5.07P2'2
Type II: = 8.25P2'2 or,
(b) Use the graph in Figure 50, or Figure 51 to arrive at the
erosion index, using the 6-hr duration line or,
(c) Use the applicable Type I or Type II curve in Figure 47.
Enter the graph at the appropriate value of the 2-yr 6-hr
rainfall and read the corresponding average annual rain-
fall erosion index. To obtain the 2-yr 6-hr erosion index,
divide the annual erosion index by 3.265.
Examples ;
Walnut Creek Drainage Basin, California. (Zone I)
From USWB TP 40, the 2-yr 6-hr rainfall is given at 1.5 in.
Therefore, using steps 4 (a) , (b) , or (c) the erosion index
is found to be :
= 5.07 (1.5)2'2 = 5.07 x 2.44 = 12.4
Estimated erosion index from Figure 50 = 12
Annual erosion index from Figure 47 = 40
40
Estimated erosion index = „ 0,c = 12.25
J .
Occoquan Drainage Basin, Virginia (Zone II)
From USWB TP 40, the 2-yr 6-hr rainfall is given as 2.55 in.
Using steps 4 (a), (b) , or (c) , the erosion index is found to be:
= 8.25 (2.55)2'2 = 8.25 x 7.85 = 65.0
Estimated erosion index from Figure 51 =66.0
187
-------
Annual erosion index from Figure 47 = 210*
210
Estimated erosion index = • , .. = 64.3
J.
*Note that the official value for annual erosion as
listed in USDA Handbook No. 282 is 200.
B. Example II Rainfall Erosion Index for Storm of Any Duration
Up to and Including 24-Hour for 2-Year Frequency
The procedure is the same as for^ Example I, €;xcept that the chart
used from USWB TP 40 will be the one for the storm frequency and
duration desired. Step 4 (c) cannot be used; only alternative 4
(a) and 4 (b) are applicable, but modified accordingly as follows:
(a) Use one of the following formulas:
2 2
El 15 P
Type I :
0.6065
n
r
2 2
Type II: JL. 19.25
H
r
(b) Use the graph in Figure 50 or Figure 51 to arrive at
the erosion index using the appropriate depth of rain-
storm and duration hour line.
Example:
Determine the erosion index for a 24-hr storm with a 2-yr
frequency in the vicinity of Occoquan. USWB TP 40 shows
depth of precipitation for such a storm to be 3.40 in. Area
is in Zone II.
(A) El _ (3.40)2'2 19.25 x 15 ,
U) 100 - 19'25 240.4672 - 4.42 ~ 66
(b) Estimated erosion index from Figure 51 = 65
C. Example III Average Annual Rainfall Erosion Index
(1) Locate the area under study in a chart in USWB TP 40 (or
similar publication) .
(2) Determine the value of 6-hr rainfall for the 2-yr frequency.
(3) Check as to the Zone in which the area is located.
188
-------
(4) Calculate the annual erosion index by one of the following
equations:
El 22
Type I : Average Annual -rrr = 16.55 P
FT 2
Type II: Average Annual -• nn = 27 P
Example:
Determine the 2-yr frequency annual erosion index for the Walnut
Creek, California and Occoquan River, Virginia, areas.
2 2
Walnut Creek: Average Annual Erosion Index = 16.55 (1.5) ' = 40
2.2
Occoquan River: Average Annual Erosibn Index - 27 (2.55) ' = 210
189
-------
APPENDIX B
FT
PART 2 - DERIVATION OF EQUATIONS FOR EROSION LNDEX
FROM TYPE I AND TYPE II STORM DISTRIBUTION CURVES
1. 24-HOUR DURATION STORM EROSION INDEX
The SCS Type I and Type II S-curves (Figure 46) were first divided into
ten parts so that an average slope for each increment could reasonably
represent the rainfall intensity during that increment; of time. Then
the kinetic energy was calculated, using Equation (3), for each incre-
ment. Each of these partial kinetic energies were multiplied by the
corresponding partial rainfall, and these products were summed to arrive
at the total Kinetic Energy (E) of the storm. This value was then mul-
tiplied by the maximum 30-min intensity and divided by 100 to arrive at
the storm erosion index. A sample calculation is attached for further
clarification.
2. STORM EROSION INDEX FOR RAINFALL OF LESS THAN 24-HOUR DURATION
In order to calculate the erosion index for storms of duration less than
24 hr, the following approach was adopted:
A. Take 1/2, 1/3, 1/4, 1/6, 1/8, and 1/12 of 24 hr tc give 12 hr, 8 hr,
6 hr , 4 hr , 3 hr, and 2 hr durations. By definition, intensity is
rainfall depth divided by time interval, i.e.,
AP
i = -r— , For three durations, intensities are computed?
12 hr 112 = f - 2 (f ) = 2 (i24)
8 hr 18 = = 3 ( ) = 3 (124)
16 - f - 4 (f) = 4 (124)
Thus, the average intensities to be used for a 1-in rainstorm in 12 hr
are those of an equivalent 2-in rainstorm of 24-hr.
The intensity increment values determine the partial kinetic energy,
but the total weighted kinetic energy of a rainstorm is equal to the
summation of the products of the oartial kinetic energy times partial
rainfall. Thus, the partial kinetic energy during an increment of a
190
-------
rainfall of 2-in in 24-hr times the corresponding partial rainfall
increments of 1-in gives the result that a 1-in rainfall in 12-hr has
a total kinetic energy of only half that of a 2-in rainfall in 24-hr.
Type I
Graphical solution for calculating kinetic energy of a 24-hour storm.
Divide the S-curve into 10 portions as follows:
Interval
1
2
3
4
5
6
7
8
9
10
19 *y /"P
rn j __ j_ t JV/ i rt i
lime t Z4
Intensity
24 t
0-6 hrs 6 00.00-0.1300 0.130 0.0217
6-8 2 00.13-0.195 0.065 0.0325
8-9 1 0.195-0.255 0.060 0.0600
9-9.55 0.55 0.255-0.315 0.060 0.1090
9.55-10.05 0.50 0.315-0.525 0.210 0.4200
10.05-10.60 0.55 0.525-0.595 0.070 0.1270
10.60-11.60 1 0.595-0.600 0.065 0.0650
11.60-14.00 2.4 0.660-0.768 0.108 0.0450
14.00-17.00 3 0.768-0.855 0.087 0.0290
17.00-24.00 7 0.855-1.000 0.145 0.0207
Interval
1
2
3
4
5 I max
6
7
8
9
10
Intensity
(i P=l)
0.0217
0.0325
0.0600
0.1090
0.4200
0.1270
0.0650
0.0450
0.0290
0.0207
Kinetic
Energy
(e)
364
422
512
677
791
619
523
469
383
358
Partial
Rainfall
(Px)
0.130
0.065
0.060.
0.060
0.210
0.070
0.065
0.108
0.087
0.145
ePx
47.32
27.43
30.72
40.62
166.11
43.33
34.00
50.65
33.32
51.91
EePx=E, E, xl *100
— 1 1 1—
47.32 100
74.75
105.47
146.09
312.20
355.53
389.53
430.18
463.50 515.41x0.420 „
515.41 100 '•'L(l
191
-------
Intensity
Interval
1
2
3
4
5 I max
6
7
8
9
10
Interval
1
2
3
4
5 I max
6
7
8
9
10
Interval
1
2
3
4
5 I max
6
7
8
9
10
(
0
0
0
0
= 0
0
0
0
0
0
i P=2 )
.0434
.0650
.1200
.2180
.8400
.2540
.1300
.0900
.0580
.0414
Intensity
(i P=5)
0
0
0
0
=_2
0
0
0
0
0
.0085
.1625
.3000
.5450
.1000
.6350
.3250
.2250
.1450
.1035
Intensity
(i P»10)
0
0
0
1
= 4
1
0
0
0
0
.2170
.3250
.6000
.0900
.2000
.2700
.6500
.4500
.2900
.2070
Kinetic
Energy
(0
464
523
611
697
891
719
623
570
507
457
Kinetic
Energy
(e)
609
655
743
829
1023
851
755
701
638
590
Kinetic
Energy
(e)
696
755
843
928
1122
950
854
801
738
690
Partial
Rainfall
(Px)
0.260
0.130
0.120
0.120
0.420
0.140
0.130
0.216
0.174
0.290
Partial
Rainfall
(Px)
0.650
0.325
0.300
0.300
1.050
0.350
0.325
0.540
0.435
0.725
Partial
Rainfall
(Px)
1.300
0.650
0.600
0.600
2.100
0.700
0.650
1.080
0.870
1.450
ePx
120
68
73
83
374
100
81
123
88
132
.40
.00
.50
.80
.00
.60
.20
.00
.50
.40
ePx
395
213
223
249
1073
298
245
378
277
428
.00
.00
.00
.00
.00
.00
.00
.00
.00
.00
ePx
905
491
506
556
2355
665
555
865
642
1000
.00
.00
.00
.00
.00
.00
.00
.00
.00
.00
EePx=E E.XI..-MOO
120
188
261
345
719
820
901
1024
1113
1245
ZePx
395
608
831
1080
2153
2451
2696
3074
3351
3779
— i 2.
.40
.40
.90
.70
.70
.30
.50
.50
.00 1.245.40x0.84 = 10.^
. 40 100
.00
.00
.00
.00
.00
.00
.00
.00
.00 3,779x2.1
.00 100 J
£ePx=E E,«xI,_-MOO
905
1396
1902
2458
4813
5478
6033
6898
7540
8540
j_y— — xu
.00
.00
.00
.00
.00
.00
.00
.00
.00 8,540x4.2
.00 100 ' 35°'7
192
-------
B. On the other hand, since the time stipulated for maximum intensity
is fixed at 30 min, it is logical to reason that as the time scale
is reduced from 24 to 12, 8, 6, 4, 3 and 2 hr, that the 30-min time
interval for these shorter storms will be the equivalent of 60, 90,
120, 180, 240 and 360 min. of the 24-hr duration curve. This of
course means that the corresponding intensities (30-min max) have
to be recalculated. The 'calculated maximum 30-min intensities are
as follows for a 1-in rainfall each for Type I distribution.
24 hr 0.420
12 hr 0.540
8 hr 0.660
6 hr 0.730
4 hr 0.866
3 hr 0.970
2 hr 1.244
1 hr 1.550
1/2 hr 2.000
C. The mathematical calculations that follow from the above deductions
are as follows.
(1) Erosion Index ... n ._ T __ . ^,
—f= —? (assuming same values for I max 30 mm as that
^ for the equivalent 24-hr duration)
FT 2 ?
= 2.176 (P24) 24-hr duration
1/2 [(2.176) (2 P12)2'2] 12-hr duration
KT 7 9
1/3 [(2.176) (3 P8) ' ] 8-hr duration
9 9
1/4 [(2.176) (4 P,) * ] 6-hr duration
D
The above relationship can be put in a more generalized form as
follows.
= ^ [(2.176) (n Px)2'2] = 2.176 (n)1'2 (Px)2'2
24
where: n = — and: x = duration of storm in hours
n
r
193
-------
Substituting for n we get:
El _ -_, ,24 1.2 ,., ,2.2
— -2.176^ (Px)
where: H = x, and Px = rainfall occurring during H hours
(2) Erosion Index / . . . , .,**_•. -,
— 7= - rr - (taking into consideration the fact that actual
v. YPe > 30-min maximum intensity will be as listed in B).
The reduction in the intensity was calculated for each duration
time and graphical analysis yielded the following equation for
the reduction coefficient for Type I distribution.
N = (
(3) Therfore, the actual erosion index is equal to the product of
the two equations derived in (1) and (2) preceding as follows:
. 17,,24,0.6065 ,_ ,2.2
= 2.176(—) (Px)
r
= 2.17 (24)0'6065 (PS)2'2
„ 0.6065
n
r
= 2.176 x 6.88 (Px)2'2
„ 0.6065
H
V
= 15 Px
r
2.2
0.6065
r (Type I Storm)
Similarly, the following equation can be derived:
El 10 „,. B 2.2
loo = 19'25 Px
0.4672
r (Type II Storm)
194
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APPENDIX C
LIST OF SELECTED REFERENCES
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195
-------
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196
-------
28. East Bay Municipal Utility District, The Land Use Master Plan
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197
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41. Hoechst, Curasol, A New Approach to the Prevention of Soil Erosion,
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55. Los Angeles County Flood Control District, Drainage District
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198
-------
56. Los Angeles County Flood Control District, Hydrology
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57. Los Angeles County Flood Control District, Report on the
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59. Maryland State Highway Administration, Guide for Designers,
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64. Miller, C.R., "Advances in Sedimentation Relevant to Watershed
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65. Miller, H.W., Hoglund, O.K., and Haffenricher, A.L., Grasses,
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66. Miller, H.W., Specifications for Stabilizing Coastal Dunes,
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199
-------
70, Norouzi, Hadi, Los Angeles County Flood Control District Debris
Production History of Debris Basins Including 1970/71. 1971/72
Seasons, Los Angeles County Flood Control District,
71o Olson, T.C. and Wischmeier, W.H., "Soil-Readibility Evaluations
for Soils on the Runoff and Erosion Stations," Soil Science
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72, Palmer, R.S0, "Waterdrop Impact Forces," Transactions of the ASAE,
pp 69-72 (1965)o
73o Piest, R.F., "The Role of the Large Storm as a Sediment Contrib-
utor", U.S. Department of Agriculture, Sedimentation Laboratory,
Soil and Water Conservation Research Division, Agriculture
Research Service, Proceedings, Federal Inter-Agency Sedimentation
Conference, 1963, U.S» Department of Agriculture Miscellaneous
Publication No. 970, pp 98-108 (1965).
74. Piest, R.F. and Miller, C.R., "Sediment Sources and Sediment Yields,"
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(June 1970).
75. Porterfield, G., An Inventory of Published and Unpublished Fluvial-
Sediment Data for California 1956-70. U.S. Geological Survey,
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76. Porterfield, G., Sediment Transport of Deposition Walnut and
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April 1970, U.S. Geological Survey, Water Resources Division,
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77. Richardson Engineering Services, Inc., Manual of Commercial -
Industrial Construction Estimating and Engineering Standards,
Downey, California 91971).
78. Ritter, J.R. and Brown, W.M. Ill, Sedimentation of Williams
Reservoir, Santa Clara County, California, U.S. Geological Survey,
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79. Rowlison, D.L<, and Martin, G.L., "Rational Model Describing Slope
Erosion," ASCE Journal of Irrigation and Drainage Division,
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80. Salsbury, M.E., Debris Dams and Basins Criteria for Design, Los
Angeles County Flood Control District, 15 pp + 25 graphs and
drawings (February 1965).
81. "San Francisco Building Trades Wages Table," Daily Pacific Builder,
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200
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82. Security Pacific National Bank, Research Department, Monthly
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of California (May 1972).
83. Slayback, R0De, Thirty Acres that Revolutionized Grazing, 2 pp.
84. Soil Survey Staff. Soil Survey Manual, United States Department
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85. Smith, D.Do and Wischmeier, W.H., "Factors Affecting Sheet
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89. Task Committee on Erosion of Cohesive Materials, Committee
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93. Townsend, L.E., Final Construction Report - Emergency Flood
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94. U.S. Bureau of Reclamation, Construction Cost Trends, (January
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Progress Report of the Soil and Water Conservation Research
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201
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97. U.S. Department of Agriculture, Agricultural Stabilization and
Conservation Service, 1971 Annual Report - California. 63 pp (1972)„
98. U.S. Department of Agriculture, Agricultural Stabilization and
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100. U.S. Department of Agriculture, Soil Conservation Service, Engi-
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101. U.S. Department of Agriculture, Soil Conservation Service,
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103. U.S. Department of Agriculture, Soil Conservation Service, Long
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-------
llOo UoS, Department of Agriculture, Soil Conservation Service
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203 ~
-------
123. U.So Weather Bureau, Hydrologic Services Division, Cooperative
Studies Section, Rainfall Intensities for Local Drainage Design
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204
-------
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138. Wittmuss, H., Lane, D. and Fisher, W., Conservation Tillage
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of Degree of Pollution with Chemical Costs," Journal AWWA,
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(1940)„
205
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SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
*- ~
w
COMPARATIVE COSTS OF EROSION AND SEDIMENT CONTROL,
CONSTRUCTION ACTIVITIES
Hotes, F. L., Ateshian, K. H., Sheikh, B.
Engineering-Science, Inc.
600 Bancroft Way
Berkeley, California 94710
,«
EPA 68-01-0755
fj^e afK«foit W •'•'•'
Period Coverfd
EPA Project Officer:
R. E. Thronson
Office of Air and Water Programs
Non-Point Source Control Branch
EPA, Washington. P. C. 20460
Cost information on erosion and sediment control measures was developed for
over 25 methods in current widespread use in both the humid Eastern and arid
Western United States. Most of the data presented were developed for the Walnut
Creek Basin in California and the Occoquan Creek Basin in Virginia, but the
detailed cost estimates presented provide a basis for estimating local costs
elsewhere for similar control methods using three principal cost elements:
labor, equipment and materials. Soil losses were estimated by using the im-
proved universal soil loss equation. The rainfall erosion index in the
soil loss equation was intensively studied, and simplified procedures for its
computation were developed and presented. Cost data were applied to theoretically-
predicted soil losses in both of the selected watersheds to obtain comparative
costs per cubic yard of soil retained for conservation measures, and similar
costs for various sediment removal methods. Control effectiveness parameters
and economic life of each method were used to determine comparable annual cost
figures. A central conclusion of the study was that costs of preventing erosion
are, in many instances, lower than the direct costs of removing sediments from
downstream areas or from water supplied. (Hotes - California)
17a. Descriptors
*Erosion Control, *Sediment Control, Comparative Costs, *Construction Costs,
*Soil Erosion, *Estimated Costs, Erosion Rates, Cost Analysis, Rainfall
Intensity, Water Pollution, Water Pollution Sources, Water Clarification, Soil
Conservation, Dredging, Desilting.
17b. Identifiers
*Universal Soil Loss Equation, *0ccoquan Creek Basin (Virginia), *Walnut
Creek Basin (California), *Rainfall Erodibility Index, Erosion Control
Methods, Sediment Removal Methods, Debris Basins.
17c. COWRRField & Group 02J, 04D , 05G, 06BC
'»..,
"
• P*ge*
J2, Ptive
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
US DEPARTMENT OF THE INTERIOR
WASHINGTON D C 2O24O
--'/ . f r F. L. Hotes
Engineering-Science. Inc.. Berkeley. CA
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