EPA-600/2-76-117
August 1976
Environmental Protection Technology Series
EFFECTIVENESS OF SURFACE MINE
SEDIMENTATION PONDS
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to develop and
demonstrate instrumentation, equipment, and methodology to repair or prevent
environmental degradation from point and non-point sources of pollution. This
work provides the new or improved technology required for the control and
treatment of pollution sources to meet environmental quality standards,
This document is available to the public.through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-76-117
August 1976
EFFECTIVENESS OF SURFACE
MINE SEDIMENTATION PONDS
by
D. Vir Kathuria
Michael A. Nawrocki
Burton C. Becker
Hittman Associates, Inc.
Columbia, Maryland 21045
Contract No. 68-03-2139
Project Officer
Ronald D. Hill
Industrial Environmental Research Laboratory
Cincinnati, Ohio 45268
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Industrial
Environmental Research Laboratory, U.S. Environmental
Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental
Protection Agency, nor does mention of trade names or
commercial products constitute endorsement or recommen-
dation for use.
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FOREWORD
When energy and material resources are extracted, processed,
converted, and used, the pollutional impact on our environment and
even on our health often requires that new and increasingly more
efficient pollution control methods be used. The Industrial Environ-
mental Research Laboratory - Cincinnati (IERL-CI) assists in develop-
ing and demonstrating new and improved methodologies that will meet
these needs both efficiently and economically.
This study was conducted to determine the effectiveness of
sedimentation ponds in the removal of suspended solids discharged
in the runoff from land disturbed by surface mines. As discussed in
this report, pond performance approached that predicated by theoret-
ically "trap" formulas under low flow conditions, but performed poorly
under high flow conditions. Part of the inadequate performance was
due to poor construction and maintenance. The information in this
report should be of interest to any program concerned with suspended
solids control in runoff. The Extraction Technology Branch of IERL-CI
proposes to follow this study with further developmental work on
sediment ponds.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
m
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ABSTRACT
An in-field evaluation of the effectiveness of sediment
ponds in reducing suspended solids in the runoff from
surface mining activities was performed. Nine selected
sedimentation ponds in the three eastern coal-mining States
of Pennsylvania, West Virginia, and Kentucky were sampled
under two different operating conditionsa baseline and a
rainfall event. Their theoretical and actual efficiency of
removal of suspended solids were computed and compared.
In general, poor construction and inadequate maintenance of
these ponds were found to be the major problem areas. The
ponds had generally higher removal efficiencies during the
baseline sampling period and much lower efficiencies during
the storm event. The theoretically predicted efficiency of
the ponds was essentially the same as the actual efficiency
under baseline conditions. During the rainfall event, there
was generally little or no correlation between the theoretical
and actual efficiencies. The predicted efficiencies were
found to be much higher than the actual efficiencies during
the rainfall event in most cases.
This report was submitted in fulfillment of Contract Number
68-03-2139 by Hittman Associates, Inc., under the sponsorship
of the U.S. Environmental Protection Agency. Work was com-
pleted as of September 1975.
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CONTENTS
Page
Foreword iii
Abstract iv
List of Figures vi
List of Tables viii
I Introduction 1
II Conclusions 3
III Recommendations 7
IV State Regulations and Design Practices 10
V Pond Selection and Evaluation 14
VI Description of Selected Ponds 19
VII Observations and Analyses of Field Data 46
VIII Discussion 53
IX References 64
Appendix A 65
Appendix B 80
Appendix C 88
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FIGURES
Number Paqe
1 Distribution of Initially Recommended 15
Ponds
2 As-BuiltDrawingofPondNumber! 21
3 Overall View of Pond Number 1 (Two-Pond 23
System). Inflow from the Pit is at the
Lower Right.
4 Pond Number 2 - Primary Pond of Two-Pond 23
System. Inflow from the Pit is through
the Pipe at the Right.
5 As-Built Drawing of Pond Number 2 24
6 Construction Drawing of Pond Number 3 26
7 Deeply Eroded Channels as a Result of 27
Water Flowing Frequently over the
Emergency Spillway
8 Undermining of the Log Across the 27
Emergency Spillway
9 Overall View of Pond Number 3 and 29
Observed Whirlpool Action Within the
Pond
10 Overall View of Pond Number 4 29
11 As-Built Drawing of Pond Number 4 30
12 As-Built Drawing of Pond Number 5 32
13 Overall View of Pond Number 5. Inflow 33
is at the Top, Center.
14 Water Escaping from the Eroded Portion 33
of the Sediment Pond
15 Construction Drawing of Pond Number 6 35
16 Overall View of Pond Number 6 36
vi
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Number
FIGURES (Continued)
Page
17 Inlet Channel to the Pond with Debris 36
Across It
18 Erosion of Road Caused by Overflow 37
Through the Emergency Spillway (Pond No. 6)
19 Overall View of Pond Number 7 37
20 Construction Drawing of Pond Number 7 38
21 Construction Drawing of Pond Number 8 40
22 Overall View of Pond Number 8 Showing 41
the Pumping Arrangements for the Deep
Mine and Eroding Side Slopes
23 Close View of Pond Outflow Riser Pipe, 42
Access Deck, and Pumping Unit for Deep
Mine
24 Outflow from the Pipe (Left) onto the 42
Dirt Road which Eventually Flows into
the Natural Waterway (Right-Hand Side)
25 Construction Drawing of Pond Number 9 43
26 Overall View of Pond Number 9, Looking 44
Toward the Dam
27 Sediment Deposits at Upper End of Pond 44
28 Removal Efficiency versus Detention Time 56
29 Removal Efficiency versus Overflow Velocity 57
30 Plan View of Conceptual Log Structure Up- 59
stream of a Sediment Pond, Acting as an
Energy Dlssipator
31 Plan View of Off-Stream Sediment Pond 59
32 Profile View of Stream Excavation for 60
Sediment Storage
33 Siphon Arrangement 1n Riser Pipe 60
34 Required Pond Area versus Effluent Quality- 62
Pond 3, Baseline Conditions
VII
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TABLES
Number Page
1 State Laws and Regulations Related To 12
Utilization of Sedimentation Basins In
Surface Mining Operations
2 Effluent Standards for The Surface Mining 13
Industry
3 Characteristics of Sampled Ponds 20
4 Results Of Pond Sampling During The 47
Baseline Condition
5 Results Of Pond Sampling During Rainfall 48
Conditions
6 Estimated Solids Accumulation 50
7 Comparison of Observed Effluent Quality 52
With Various Effluent Standards
viii
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SECTION I
INTRODUCTION
Surface mining of coal involves the removal of vegetation,
earth, and rock in order to uncover the underlying coal
deposits. As a consequence of this massive earthmoving
operation, large areas are subject to accelerated erosion of
unstabilized soil. Without controls, this soil would
eventually be carried by surface runoff into the natural
waterways. To prevent the environmental deterioration of
natural streams and waterways, many states have enacted laws
and regulations requiring that the discharge from mining
operations meet certain effluent standards and/or criteria.
Several States, including Pennsylvania, West Virginia, and
Kentucky, have regulations that require the construction of
sediment ponds to control the runoff from surface mines.
These ponds are primarily intended to trap the suspended
solids generated from the mining activity.
Even though there are over 200 sediment ponds in operation
at the present time, the documentation of the effectiveness
of these ponds for removing suspended solids is limited.
There are conflicting opinions on the actual effectiveness
of these sediment ponds, but the general consensus is that
overall the sediment basins are highly effective. The U.S.
Soil Conservation Service (SCS) indicates that if their
design criteria are followed, a trap efficiency (i.e., the
percentage of incoming sediment which remains in the pond)
of at least 75 percent should be attained.' Other studies
have indicated that trap efficiencies of 85 percent and
higher have been obtained.2 However, the data for the above
trap efficiency estimates are rather sketchy. A rigorous
analysis of the various aspects that govern sedimentation
basin performance based on actual field data, especially in
the field of surface mine sedimentation control, was not
previously available.
Consequently, a study was conducted to quantitatively deter-
mine the effectiveness of a number of surface mine sedimenta-
tion ponds in reducing suspended solids in the runoff from
surface mining activities. In all, nine surface mine sedi-
mentation ponds in three eastern coal mining States
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Pennsylvania, West Virginia, and Kentucky, were selected for
field evaluation. Two ponds were selected in Pennsylvania,
one pond in northern West Virginia, two ponds in the steep
slopes of southern West Virginia, two ponds in eastern
Kentucky, and two ponds in western Kentucky. Under these
overall geographic constraints, the ponds were selected so
that a variety of different physical characteristics could
be studied. The selected ponds represented a broad spectrum
of the type, location, topography, soil type, and usage by
the coal mining industry of the ponds within the eastern
United States. Ponds representing the best in the state-of-
the-art were to be selected for study.
As-built measurements of each pond and its appurtenances
were taken. Water samples during a baseline (nonstorm)
period and during a rainfall event were collected, and flow
measurements were taken at both the inflow to and outflow
from the ponds. Based on the field observations, the actual
removal efficiency of the ponds was determined and compared
to its theoretical efficiency as computed by Stokes' Law.
The overall objectives of the project were to obtain and
document the effectiveness of various types of sedimentation
ponds normally used in surface mining operations, determine
their shortcomings, and develop recommendations for design
and maintenance procedures which will maximize suspended
sol ids removal.
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SECTION II
CONCLUSIONS
An in-field evaluation of the effectiveness of sediment
ponds in reducing suspended solids in the runoff from
surface mining activities was performed. Nine selected
sedimentation ponds in the three eastern coal-mining
States of Pennsylvania, West Virginia, and Kentucky were
sampled under two different operating conditions, a base-
line and rainfall event. Their theoretical and actual
efficiencies of removal of suspended solids were computed
and compared.
The sedimentation ponds which were properly utilized and
maintained were measured to have high efficiencies of
removal of suspended solids during the baseline sampling
period. Ponds which were not properly utilized or main-
tained had deficiencies which contributed to their poor
removal efficiencies. These deficiencies included such
things as a water supply pump intake located near the out-
flow riser or an eroded emergency spillway.
Generally, the efficiency of removal of suspended solids
was measured to be much lower during the storm event as
compared to during the baseline condition.
In general, the ponds were found not to be constructed in
accordance with the approved plans and specifications.
This contributed to poor pond performance. For instance,
in one pond the top of the normal overflow riser was con-
structed higher than the crest of the dam, resulting in
frequent use of the emergency spillway. This caused
severe erosion and downstream damages. In addition, once
the ponds are constructed, they were found to be poorly
maintained. Timely removal and disposal of the accumu-
lated sediments, cleaning of clogged outflow pipes, repair
of emergency spillways and embankment repair are extremely
important for the proper functioning of the whole sedimenta^
tion pond system, but were usually overlooked.
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Off-channel, dugout-type ponds, similar to the ones commonly
used in Pennsylvania where water is pumped from the mining
pit to the pond, are more effective and have less need for
maintenance than the ponds which are built in the main stream
channel. This is primarily due to the fact that no direct
surface runoff enters the off-channel ponds and the inflow
rate can be controlled by the rate of inflow pumping. Also,
the pit area from where the water is pumped acts as a prim-
ary settling basin. However, because of physical, topo-
graphical, or geographical constraints, the construction of
the off-channel, dugout-type of pond may not be feasible in
all cases, especially in steep mountainous terrain, but
should be encouraged wherever possible. The main disadvant-
age of the use of the dugout-type ponds in Pennsylvania is
that they do not intercept the runoff from all of the dis-
turbed land. The runoff from the slopes of the spoil piles
which face away from the pit never enters the ponds. Thus,
an additional pond or other sediment control device would
have to be placed so that the sediment generated from these
slopes would also be controlled.
It appears that if sediment ponds are built to have approxi-
mately a 10-hour detention time or an overflow velocity of
less than 2x 10'^ m/sec, high efficiencies of removal of
suspended solids will result. This is assuming, of course,
that the ponds are adequately maintained throughout their
11 f e .
The problem of resuspension of settled sediment was not
observed in most of the ponds where their depth was greater
than 1.0 m (3.3 ft). Therefore, maximizing the surface
area and maintaining a minimum depth of about 1.0 m (3.3 ft)
at all times will result in better performance of the pond.
Approximately one-half of the ponds surveyed did not meet
the State or proposed Federal effluent standards during the
measured baseline and storm conditions. It is recognized
that additional factors such as high intensity storms oc-
curring at the time of sampling and non-typical inflows at
the time of sampling could have influenced the results ob-
tained during this program. However, field observations
indicate that construction of the ponds not in accordance
with approved plans and specifications and poor subsequent
maintenance of the ponds were the two major factors con-
tributing to their poor performance.
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Ponds built in the stream channel are frequently left in
place after the mining activities are completed. Trapped
sediments along wfth the added volume of the embankment,
may eventually be carried Into the natural waterways when
failure of the dam occurs during high flood flows. The
problem of excessive sedimentation of downstream areas is
therefore, only postponed - not reduced. Thus, provisions
for stabilization of the pond area should be a part of the
overall pond plan.
The computed theoretical efficiency of the ponds that were
properly utilized and maintained was essentially the same
as the measured suspended solids removal efficiency for the
baseline conditions. During the rainfall event, however,
there was generally little or no correlation between the
theoretically predicted efficiencies during the rainfall
event. During this study, the low measured efficiencies
during the rainfall event were, in most cases, directly
attributable to improper construction and maintenance of
the ponds.
Many deficiencies are inherent in the use of Ideal Settling
Theory for predicting pond settling efficiency. The theory
does not adequately consider such things as the location of
the inlet and outlet, shape of pond, and depth of water in
the pond, However, much information is available on para-
meters such as the design of inlets and outlets, pond
shaping, etc., as presented in Section VIII of this report,
which should be utilized in constructing sediment ponds.
Good mine reclamation practices are essential to reduce the
suspended solids content delivered to the pond.
In order to increase the suspended solids removal efficien-
cies of sediment ponds, additional measures such as trash
barriers or velocity checks at the inlets and non-perfor-
ated risers should be utilized wherever possible. In order
to meet effluent standards, flocculants may also have to
be used in some cases. Also, a procedure for the documenta-
tion of the maintenance requirements of the sediment ponds
needs to be established.
The State design standards currently used in Kentucky and
West Virginia are the most thorough and are good for use
as general design and construction guidelines, but they
are deficient in the following areas:
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(1) Maintenance and repair of the pond during and
after the mining operation
(2) Disposal of sediment during and after the
mining operation
(3) Dismantling of the pond after mining opera-
tions have ceased
(4) Design of a sediment pond to achieve a specific
water quality criterion.
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SECTION III
RECOMMENDATIONS
POND DESIGN AND MAINTENANCE
The criteria for the design of sediment basins are derived
from the Soil Conservation Service design practices, which
are based on the retention of a percentage of the total
suspended solids. Since a large number of States have al-
ready adopted water quality criteria, the design of sedi-
mentation basins should be based on the removal of solids to
meet a specific water quality standard. It is recognized
that these designs will have to be referenced to a storm of
a specific return Interval.
In view of the problem of deficient State design standards
in the areas of maintenance and repair of the ponds, dis-
posal of sediment, dismantling of the pond after mining has
ceased, and reclamation of the area where the pond was
built, 1t 1s recommended that these additional points be
addressed 1n the State standards.
All State regulations reviewed require cleaning of the pond
after a certain portion of the capacity is used-up. How-
ever, no records of sediment accumulation are kept. It 1s
essential, therefore, that records of all sedimentation
ponds be kept with Information such as when they were built,
when cleaned, when repaired, etc. included in the records.
In addition, simple, visual methods such as a mark or metal
plate on the outflow riser should be used to notify the
inspector when pond cleaning is required.
Alternative overflow devices, such as the siphon draw pipe
or a riser with perforations on only a portion of its
length down from the top should be considered for use in-
stead of the standard, perforated riser. These alternative
overflow devices have the capability of reducing the amount
of suspended sediment 1n the pond outflow.
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Recognizing topographical constraints, it is recommended
that the construction of off-drainage sedimentation ponds
be considered first in the design of a surface mine sedi-
mentation pond. It is recognized, however, that the spoil
pile slopes on the opposite side of the pit in area mining
operations will need an additional sediment control device
installed downslope of them.
Unless specific site conditions warran't a more conservative
design, it is recommended, based on the results of this
study, that sediment ponds for surface mines be designed
and constructed to have at least a 10-hour detention time or
an overflow velocity of less than 2x 10~5 m/sec for the
design storm.
It is also recommended th-at the ponds be designed and con-
structed based on field-run topographic maps. Most of the
ponds investigated were designed and constructed based on
simple enlargements of U.S.6.S. topographic maps. These
proved to be inadequate and accounted for many inadequate
and/or inefficient designs and many construction versus
design discrepancies. It is further recommended that these
field-run topographic maps be at two-foot contour intervals
on flat or gentle slopes and at five-foot contour intervals
on steep slopes.
RESEARCH REQUIREMENTS
All nine selected ponds were sampled during only two differ-
ent operating conditions, a baseline and a rainfall event.
Since only these two discrete sampling periods were used to
evaluate the performance of the ponds, the results may not
be representative of the long term performance of the ponds.
Thus, evaluation of the ponds based on an extended sampling
period needs to be done to provide statistically sound data.
Timely and adequate maintenance of sediment control struc-
tures is vital to insure their proper functioning. The
quality of the effluent in all causes could have been im-
proved with proper maintenance of the ponds. A comparison
study of the normally maintained ponds versus the ponds
maintained under optimum maintenance is necessary to correct-
ly evaluate the effectiveness of these ponds.
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Outflow from the pond through a perforated riser allows fine
sediment to be carried away through the perforations. Fur-
ther study is necessary to investigate the alternative out-
flow devices such as the siphon draw pipe which is currently
being used in the State of Maryland or outflow risers with
perforations only part of the way down from the top.
The States of West Virginia, Kentucky, and Maryland currently
have sediment pond design standards which specify a minimum
storage volume per unit area of disturbed land. Further
research needs to be performed to verify that these specifi-
cations are safe design criteria and to evaluate which
storage factors are the most realistic.
It is recognized that many factors enter into how much sus-
pended sediment is removed by a pond. Some of these factors
include the return interval of the storm, the pond detention
time, the storage available, and the antecedent soil moisture
Additional research should be performed to further evaluate
the effects these factors have on pond performance.
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SECTION IV
STATE REGULATIONS AND DESIGN PRACTICES
The initial phase of this study involved the review of
State regulations and design practices with respect to the
control of sediment from surface mining operations. Since
the nine study sites under this program were located in
three eastern coal mining States of Pennsylvania, West
Virginia, and Kentucky, the main emphasis of this phase of
the study was placed on these three States. However, the
rules, regulations, and design practices for sediment basins
utilized by other eastern States and agencies were also
reviewed. These included those of Maryland, Ohio, Indiana,
Illinois, Virginia, Tennessee, and the Tennessee Valley
Authority (TVA).
LEGISLATION
Existing State laws do not directly address the utilization,
design, and operation of sedimentation ponds. In general,
the laws serve the following functions:
(1) Assign responsibility for the supervision of
surface mining and reclamation activities to a
specific agency.
(2) Define the terminology associated with surface
mining and reclamation activities.
(3) Define the responsibility and duties of the
responsible agency and its personnel.
(4) Define the necessary requirements for conducting
surface mining and reclamation activites within
the State.
(5) Outline the penalties for violating the promul-
gated laws.
10
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The responsible agencies and applicable laws related to the
use of sedimentation basins in surface mining activities in
the States of Kentucky, Pennsylvania, and West Virginia are
listed in Table 1.
REGULATIONS AND DESIGN CRITERIA
Design criteria and specifications for sedimentation ponds
utilized in conjunction with surface mining activities have
been developed for all three States where study sites are
located. Such items as the construction details, size,
number, and location of these structures are specified by
regulations. The extent and depth to which these design
considerations and regulations are addressed in the various
States varies considerably. In general, the criteria follow
the design procedures developed by the U.S. Soil Conser-
vation Service {SCS) for sediment basins.1 This fact is not
surprising since in both Kentucky and West Virginia the
criteria were developed with the assistance of the SCS. A
comparison of the various elements related to the design,
construction, and maintenance of sediment ponds in the
states of Kentucky, Pennsylvania, and West Virginia is pre-
sented in Appendix A. Also presented in Appendix A are
brief summaries of the status of regulations that pertain to
the use of sedimentation ponds in conjunction with surface
mining activities in other eastern States and agencies.
FEDERAL AND STATE EFFLUENT STANDARDS
Most States have adopted water quality standards for dis-
charges from surface mining activities. The various stand-
ards consider all or some of the following parameters as
being important with respect to surface mining activities:
(1) Suspended solids
(2) pH
(3) Total iron
(4) Alkalinity
(5) Toxic material
(6) Oils and grease
Table 2 compares the State effluent standards for the
surface mining industry for the States in which the study
ponds were located, with the current preliminary Federal
effluent guidelines.3
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Table 1. STATE LAWS AND REGULATIONS RELATED TO UTILIZATION OF
SEDIMENTATION BASINS IN SURFACE MINING OPERATIONS
State
Applicable laws
Promulgated rules
and regulations
Responsible
agency
Kentucky
Chapter 350,
Title XXVIII
Kentucky Revised
Statutes
Effective: Jan. 1, 1973
Kentucky Department for Natural
Resources and Environmental
Protection, Strip Mining
Regulations
Department for Natural
Resources
Division of Reclamation
Pennsylvania
Surface Mining
Conservation and
Reclamation Act
Effective: Jan. 1, 1972
Pennsylvania Department of
Environmental Resources,
Standard Conditions
Accompanying Permits
Authorizing the Operation
of Coal Mines, March 31, 1967
Department of Environ-
mental Resources,
Bureau of Land Protec-
tion & Reclamation,
Division of Mine
Reclamation-
West Virginia
Article 6 and 6A,
Chapter 20, Code of
West Virginia
Effective: Mar. 13, 1971
West Virginia Surface Mining/
Reclamation Regulations,
Department of Natural Resources
Chapter 20-6, Series VII, (1971)
Department of Natural
Resources, Division
of Reclamation
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Table 2. EFFLUENT STANDARDS FOR THE SURFACE MINING INDUSTRY
State
Federal
Kentucky
Pennsylvania
West Virginia
Turbidity or
suspended solids
30-100 mg/1
150 JTU'-s*
4
1000 JTU's
or less#
PH
6.0-9.0
6.0-9.0
6.0-9.0
5.5-9.0
Total
iron
4.0-7.0 mg/1
7.0 mg/1 or
less
7,0 mg/1 or
less
10 mg/1 or
less
Toxic
Alkalinity materials
Greater than *
acidity
Greater than
acidity
Oils &
grease
+
* No toxic or hazardous material as designated under the provisions of Section 12 of the Federal
Water Pollution Control Act or known to be hazardous or toxic by the permittee except with the
approval trf the Regional Administrator (EPA) or his authorized representative.
+ Final resolution of this parameter must await discussion with the oil industry. After resolu-
tion, it will be applied to all industry on a relatively uniform basis. Present thinking is
that it may be a single number no more stringent than 5 mg/1 and no less stringent than 10 mg/1
as a final effluent limit. The use of dilution to achieve this number will not be allowed.
4> The discharge shall contain no settleable matter, nor shall it contain suspended matter in
excess of 150 Jackson Turbidity Units, except during a precipitation event, which the operator
must show to have occurred, in which case 1000 Jackson Turbidity Units may not be exceeded.
£ No silt, coal mine solids, rock debris, dirt, and clay shall be washed, conveyed, or otherwise
deposited into the waters of the Commonwealth.
# Turbiditynot more than 1000 Jackson Units (JU) of turbidity 4 hours following a major preci-
pitation event and not more than 200 JU after 24 hours (major precipitation event = 1/2 inch
of rainfall in 30 minutes).
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SECTION V
POND SELECTION AND EVALUATION
SELECTION OF STUDY PONDS
Most of the surface mining activity in the eastern United
States is concentrated in the three States of Pennsylvania,
West Virginia, and Kentucky. The selection of sedimentation
ponds for in-field evaluation was, therefore, confined to
these three States. The intention was to select a total of
nine surface mine sedimentation ponds according to the
following geographical distribution: two ponds in Pennsyl-
vania, one pond in northern West Virginia, two ponds in the
steep slopes of southern West Virginia, two ponds in eastern
Kentucky, and two ponds in western Kentucky. Selection was
accomplished as follows.
First, the cognizant agencies in the three States, including
the Kentucky Division of Reclamation; the West Virginia
Department of Natural Resources, Division of Reclamation;
and the Pennsylvania Department of Environmental Protection
were contacted for their recommendations on potential candi-
date sites in their respective jurisdictions. Figure 1 is a
map of these three States with the distribution and number
of sedimentation ponds recommended, by county, within the
three States.
Designs, construction drawings, and other pertinent in-
formation which is conventionally submitted by the mine
operators to the State agencies were obtained and reviewed.
The list of initially recommended sites was narrowed down to
a small number which could be thoroughly investigated in the
field. Based on the results of the initial field recon-
naissance of these and some additional ponds which were
suggested by the field inspectors 1n those areas, final
selection of nine ponds was made. The ponds were selected
to satisfy the following criteria:
(1) The selected ponds represent a range of:
(a) Size
(b) Topography In which they are built
(c) Soil types in which they are built
14
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--
FIGURE 1. Distribution of Initially Recommended Ponds
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(d) Mining procedure used in the tributary
watershed
(2) All sediment control structures be approved
by the cognizant State agency
(3) Selected ponds be representative of the typical
construction used in the area"
(4) Mining activity exist during the course of
the study
(5) The site be accessible for sampling
FIELD INVESTIGATION OF SELECTED PONDS
The main objective of this study was to evaluate and deter-
mine the actual efficiencies of the selected ponds in removing
suspended solids from the influent. The actual efficiencies
were then compared to the design criteria and the theoreti-
cally predicted efficiencies. To achieve this objective the
field investigations were subdivided into two parts: As-
built measurements and water sampling.
As-Built Measurements
The designs and drawings prepared for the sediment ponds
normally use U.S.G.S. quadrangle maps as a base. Actual
topographic surveys and establishment of horizontal and
vertical controls for construction are seldom performed.
Therefore, the actual construction of the structures and
their location Is sometimes different from the exact loca-
tion shown on the drawings. Therefore, measurements were
taken to determine any differences between the design
drawings and actual construction of the selected ponds.
The following main parameters which influence the perfor-
mance efficiency of the sedimentation ponds were measured
for each of the nine ponds:
(1) Size and geometry of the pond to determine Its
surface area
(2) Size, location, and material of the Inflow and
ogtflqw structures
(3) Sediment accumulation
(a) Depth of water
(b) Depth of sediment
16
-------
Water Sampling
Water quality samples were collected and flow measurements
taken at both the inflow to and outflow from each pond. The
samples were taken during a baseline (nonstorm) period as
well as during a rainfall event in order to determine
the pond behavior under two different operating conditions.
The duration of sampling varied according to the size,
shape, and operating conditions present at each pond. The
collected influent and effluent samples were analyzed for
the following parameters:
(1 ) Suspended sol ids
(2) Settleable solids
(3) Turbidity
(4) PH
(5) Specific gravity of the suspended particles
(6) Grain size distribution of the incoming
suspended particles
(7) Water temperature
THEORETICAL AND ACTUAL TRAP EFFICIENCIES
Theoretical Analysis
The efficiency of a sedimentation pond is defined as the
percentage of incoming suspended matter which is settled in
the pond. Theoretical efficiency of the selected ponds was
determined by using the Ideal Settling Theory (Stokes1 Law)
A brief discussion of Ideal Settling Theory and the factors
which influence ideal settling is given in Appendix B. In
ideal settling the removal efficiency of the suspended
solids is dependent upon the following:
(1) The surface area of the basin
(2) The rate of inflow
(3) The horizontal velocity of flow through
the basin
(4) Settling velocity of the particles
17
-------
Also, the depth of the basin will have
depending on whether or not horizontal
tained below the scour velocity.
some influence,
velocity is main-
The critical settling velocity of the smallest size particle
settled in each sediment pond was computed based on the
measured flow rate and the surface area of the basin. The
smallest size particle which would settle with the calcu-
lated velocity was determined by using Stokes1 Law (see
Appendix B). The percentage of this size particle in the
incoming sediments to the basin will give an indication of
the expected removal efficiency of the basin.
Actual Efficiency
The percentage of solids actually removed by a particular
sediment basin was determined by using the formula:
R (% solids removed) =
10'
1 -
10'
100
(1)
where C, = solids concentration of influent, mg/1
C2 = solids concentration of effluent, mg/1
The formula was originally derived from a simple mass balance
for a conventional dredged material containment basin^.
The suspended solids concentration in the influent and
effluent for use in the formula were obtained from the
inflow and outflow water quality samples taken during the
course of the field surveys of each pond.
18
-------
SECTION VI
DESCRIPTION OF SELECTED PONDS
The physical characteristics of all selected ponds at the
time the sampling program was conducted are presented in
Table 3. A brief description of each pond, including the
observed conditions at the time of sampling and an identi-
fication of the problems associated with each pond follows.
POND NUMBER 1
This is a combination of two rectangular dugout ponds in
series. The mining procedure being used at the site is what
is conventionally known as area mining. This procedure is
generally used in relatively flat areas where coal seams are
roughly parallel to the land surface. The operation is
usually started with a box-cut or trench extending to the
limits of the property, with a concomitant parallel spoil
bank. Spoil material from each successive parallel cut or
trench is placed in the preceding trench. The maximum
length of the open cut is, however, limited to 457.2 m (1500
ft) according to the current Pennsylvania regulations.
The surface runoff from the active mined areas is collected
in the pit and then pumped into the primary settling basin.
Water from the 34.5 m x 16.2 m (113 ft x 53 ft) primary pond
overflows into a 30.5 m x 16.5 m (100 ft x 54 ft) secondary
pond through a 20.3 cm (8 in.) diameter cast iron pipe and
finally discharges through a ditch into the natural waterway.
Figure 2 is a drawing of the as-built sediment control
ponds. In this type of arrangement, since no surface runoff
enters the pond directly, the inflow into the overall system
is somewhat independent of the runoff from a rainfall event.
Inflow to the ponds is more dependent on the rate of pumping
from the pit area. Therefore, in reality, the pit acts as a
primary settling area for the sediments from the mining
activity.
The construction of these ponds was performed by digging two
rectangular pits in the ground at random. The pits were
observed to have unstable, unvegetated, and almost vertical
19
-------
Table 3. CHARACTERISTICS OF SAMPLED PONDS
Pond No. Location
1
2
3
4
5
6
7
8
9
Pennsylvania
Pennsylvania
Eastern
Kentucky
Eastern
Kentucky
Western
Kentucky
Western
Kentucky
Northern
West Virginia
Southern
West Virginia
Southern
West Virginia
Pond Drainage Average
type area (ha) slope*
2-rectangular dugout
ponds in series
2-circular dugout
ponds in series
Earth embankment with 40
perforated riser
Earth embankment with 23
perforated riser
Dugout
Earth embankment with 40
trickle tube princi-
pal spillway
Earth embankment with 45
perforated riser
Earth embankment with 78
square drop inlet
Earth embankment with 81
trickle tube princi-
pal spillway
Flat
Flat
Steep
Steep
Moderate
Gentle
Steep
Steep
Steep
Type of Nominal
mining surface area (m2)
Area mining
Area mining
Head-of -hollow
fill
Mountain top
removal
Area mining
Area mining
Mountain top
removal
Contour
Contour
1,058
1,135
1,781
1,023
1,255
19,045
1,101
3,670
4,238
* Gentle, 10%; moderate, 10-25%; steep, > 25%.
-------
Aluminum Pipe
L_ ₯T_I
40. 6>
Overflow
ani
Iron
^ Side slopes of
both ponds are
verfical
V
U..O cm. (&.&")
A-A
FIGURE 2. As-Built Drawing of Pond Number 1
21
-------
side slopes. The depth of the ponds was greater than the
designed depth in an effort, according to the inspector, to
make them both more effective and longer lasting. Figure 3
is an overall view of Pond Number 1. The as-built ponds
were built in contrast to the design drawings which showed
2:1 side slopes, a splash board on the inflow pipe for
dissipation of energy, a baffled spillway trough, and a
small treatment plant.
The side slopes of the ponds were observed to be unstable.
This condition was further aggravated by the soil which had
become saturated because of heavy rain for the 12-hour
period before collection of the samples. The suspended
solids content in the overflow was, in some instances,
greater than that in the inflow. This was possibly due to
erosion of the pond banks themselves and erosion at the
overflow due to high velocity and eddies. In spite of these
influences, however, the pond effluent was fairly clean.
POND NUMBER 2
This sedimentation pond is similar to Pond No. 1 except that
the two dugout ponds in this case are circular in shape.
Area mining is again used in this case. At this surface
mine, the surface runoff from spoil areas as well as some
undisturbed areas is diverted through diversion channels
into the pit area. Thus, this sediment pond system also has
the benefit of initial settling of suspended solids in the
pit sump area. The water from the pit is pumped into the
primary pond through a flexible hose which entered the first
pond below water level. Figure 4 shows the sediment ponds.
Figure 5 is an as-built drawing of the ponds.
No information on the proposed design and construction of
this pond was available from the State agency. This is a
fairly old pond and at the time the permit application for
this operation was processed, designs and drawings for sedi-
mentation structures were not required. However, the oper-
ator was required to comply with the laws and regulations of
the Pennsylvania Surface Mining Conservation and Reclamation
Act.
The construction was done by digging two circular holes in
the ground using a backhoe. The excavated material from the
pond was dumped on the edge of the ponds to form the banks.
Although the side slopes of the ponds were not stabilized by
vegetation, the ponds functioned very well under both
sampling conditions.
22
-------
FIGURE 3. Overall View of Pond Number 1 (Two-Pond
System). Inflow from the Pit is at the
Lower Right.
FIGURE 4. Pond Number 2 - Primary Pond of Two-Pond
System. Inflow from the Pit is through
the Pipe at the Right.
23
-------
ro
Cast Iron Pipe
/lunolnum Pipe
'5
inflow
fefa
plaaflc (ubfng
FIGURE 5. As-Buflt Drawing of Pond Number 2
-------
POND NUMBER 3
The sediments generated from this mining operation are con-
trolled by two primary impoundments built across two small
tributaries. The discharges from these two sediment control
dams flow into the secondary impoundment built across the
main stream approximately 200 m (700 ft) downstream. Under
this study only the primary pond on one of the two tribu-
taries was evaluated.
Figure 6 is a construction drawing of the pond. A 7.6 m (25
ft) high earth embankment was built with a 61.0 cm (24 in.)
diameter perforated riser pipe and 45.7 cm (18 in.) diameter
principal spillway. However, contrary to what is shown in
the drawing, the top of the normal overflow riser was measur-
ed to be 1.0 m (3.3 ft) higher than the crest of the dam.
The emergency spillway was constructed by cutting into the
downstream side slopes, thereby making the slopes steeper
and unstable. The capacity of the pond was observed to be
greatly reduced due to sediment accumulation, and consequently
the water had been regularly discharging through the emergency
spillway. It was observed that gullies approximately 3 m
(10 ft) deep (Figure 7) had been eroded into the emergency
spillway channel, indicating that water had been frequently
overflowing through the emergency spillway. An attempt was
made by the mine operator to control the water overflowing
through the emergency spillway by dumping a large log across
the spillway (Figure 8). As seen from Figure 8, this log
was undermined by approximately 0.6 m (2 ft). Heavy rains
were prevalent in the area during the sampling period. The
amount of rain in a nearby gaging station on the day of
sampling was measured to be 3.53 cm (1.39 in.) and there was
a flash flood warning for the area.
The capacity of the pond was reduced due to sediment accumu-
lation, which at certain locations, was measured to be as
much as 3.3 m (10.8 ft). The average depth of water in the
pond was only 0.7 m (2.4 ft) and sediment had accumulated to
above the water level at the upper end of the pond. However,
lack of overall maintenance of the pond was the primary
cause of the poor effluent quality. The vegetative cover on
the embankment and side slopes was sparse and the perfora-
tions in the riser pipe or main barrel of the principal
spillway were clogged.
In addition, the flow and velocity of flow into the pond was
high. A whirlpool action was observed around the normal
overflow riser pipe during the storm, which created a
stirring action within the pond. This action resuspended
25
-------
FIGURE 6. Construction Drawing of Pond Number 3
-------
FIGURE 7. Deeply Eroded Channels as a Result of Water Flowing
Frequently over the Emergency Spillway
FIGURES. Undermining of the Log Across the Emergency Spillway
.
-------
the deposited sediments and carried them into the outflow.
Figure 9 shows an overall view of the pond and the observed
whirlpool action.
POND NUMBER 4
This sediment control structure is also built across a
stream channel and consists of an approximately 7.6 m (25
ft) high earth embankment with a 35.6 cm (14 in.) cast iron,
perforated riser pipe and a 61.0 cm (24 in.) cast iron
principal spillway pipe. Figure 10 is an overall view of
the pond.
A large amount of overburden had been generated from the
mountain top removal mining activity. This overburden was
placed in the adjacent natural depressions and is generally
referred to as hollow fill. Erosion from the slopes of the
hollow fills was heavy and was the main source of sediment
to the pond.
Conventionally, in the design of the riser type of outflow
from sediment control structures, the size of the riser pipe
is larger than the spillway pipe. The approved design
drawings reflected this relationship, but the overflow was
constructed differently as shown in Figure 11. The princi-
pal spillway pipe was observed to be a 61.0 cm (24 in.)
diameter cast iron pipe as opposed to the designed 35.6 cm
(14 in.) diameter steel pipe. Also, the vertical riser pipe
was a 35.6 cm (14 in.) diameter cast iron pipe as opposed to
the designed 50.8 cm (20 in.) diameter steel pipe. The
emergency spillway was constructed by cutting into the down-
stream side slope thereby making the slope steeper and
unstable. The pond embankment slopes were wel1-vegetated
and stabilized.
The amount of rain for the day of sampling was measured to
be 6.73 cm (2.65 in.) at a nearby gaging station. This pond
was also relatively ineffective in removing suspended
solids during the measured storm event. This was probably
due to the high inflow rate and relatively small pond
surface area. This pond had the highest flow to surface
area ratio of any pond sampled during the rainfall event.
Another factor which contributed to the low quality effluent
was that a large amount of sediment had accumulated in the
pond. The water depth averaged less than 0.7 m (2.5 ft)
near the riser pipe.
28
-------
FIGURE 9. Overall View of Pond Number 3 and Observed
Whirlpool Action Within the Pond
FIGURE 10. Overall View of Pond Number 4
i
-------
-Wafer iur(oc« (i(or..: frveoj
r(oc« (i(or..: frveoj)
.-Wafer Surfoce (base lir>e,
OJ
o
30 io co to ico 100
IO3 BO CO iO TO
FIGURE 11. As-Built Drawing of Pond Number 4
-------
POND NUMBER 5
The provision of any sediment control structure in western
Kentucky is voluntary on the part of mine operators, as long
as the State discharge requirements are met. Designs and
drawings for this pond, therefore, were not prepared. It
was built by piling overburden from the mine onto a cleared
ground surface to form a containment area. There was no
provision for an emergency spillway. The outflow from the
pond was through a 30.5 cm (12 in.) diameter corrugated
metal pipe which discharged into the natural waterway. The
pond can be classified as a dugout type pond.
In this area mining operation, surface runoff from most of
the disturbed areas is collected in the pit, from where it
is pumped into the inflow channel to the sediment pond.
This inflow channel flows through a metal culvert pipe under
a haul road at the upstream end of the pond. The culvert
pipe had silted-up and was buried under the sediments. Con-
sequently, water was flowing over the unstabilized haul road
and then into the pond. Maintenance and construction vehicles
continued to traverse the haul road, thus stirring up sedi-
ment which was subsequently washed into the pond.
The sediment pond was also comparatively small and very
shallow. Figure 12 shows the outline of the shape and size
of the pond and Figure 13 is an overall view of the pond.
Very little freeboard was provided to accommodate the amount
of water being pumped from the pit. The water level during
the storm event was only 20.3 cm (8 in.) below the top of
the containment berm. In fact, the containment berm was
breached toward the end of the rainfall event sampling
period as shown 1n Figure 14. Compaction of the berms was
inadequate, and they were not vegetated. Consequently,
erosion of the berm caused its failure. This erosion was
partly responsible for the low measured removal efficiency
during the storm event.
In general, the design, construction, operation, and main-
tenance of this pond was inadequate, resulting in the
measured low efficiency and subsequent failure of the
containment berm.
POND NUMBER 6
Ponds of this size and magnitude are seldom built for the
purpose of sediment control only, In addition to sediment
control, this pond was also built to serve as a recreational
31
-------
FIGURE 12. As-Built Drawing of Pond Number 5
-------
FIGURE 13 .
Overall View of Pond Number 5.
Inflow is at the Top, Center.
FIGURE 14.
Water Escaping from the Eroded
Portion of the Sediment Pond
33
-------
lake for the nearby homeowners after the mining activity is
terminated. The reason for selecting this site for evalua-
tion was that this was a well-built and well-engineered
structure as compared to many other sediment control struc-
tures in western Kentucky.
The earth embankment which impounds the water is approximate-
ly 183 m (600 ft) long and 6.1 m (20 ft) high with a 30.5 cm
(12 in.) diameter trickle tube outflow. The construction
drawing of the structure is shown in Figure 15 and an over-
all view of the pond, is shown in Figure 16. The emergency
spillway consists of a bare earth chute with no vegetation.
Both surface runoff and water pumped from the mining pit
area contribute to the inflow to this pond. The velocity at
the inflow was greatly reduced because of debris and trees
which had been felled across the inflow channel (Figure 17),
resulting in the deposition of sediment before it reached
the pond.
Even though the pond was built oversize, the overflow pipe
through the embankment was undersized. This resulted in
clogging of the overflow pipe. Consequently, water contin-
ually flowed through the emergency spillway. Since there
was inadequate protection against erosion downstream from
the emergency spillway, severe downstream off-site damage
resulted as seen in Figure 18.
POND NUMBER 7
Figure 19 shows an overall view of the pond looking toward
the dam. Figure 20 is the detailed design drawing of this
sediment control structure. Contrary to the dimensions
shown in the drawing, an earth dam having a top width of
9.73 m (31.9 ft) and a height of approximately 6.1 m (20 ft)
was built. The outflow structure consisted of a 91.4 cm (36
in.) perforated steel riser pipe and a 61.0 cm (24 in.)
steel principal spillway pipe. The emergency spillway was
built of a grassed channel instead of a riprap channel as
shown in the drawings. However, the surface area of the
pond was essentially the same as shown on the drawings.
There was mining activity on both sides of the valley across
which this embankment was built. A portion of the flow into
this pond was from another small sediment pond just upstream
from this one. The upstream pond trapped sediments genera-
ted on one side of the valley. There was evidence of severe
erosion of the slopes near the mining activity due to the
high velocity of the surface runoff from the steep slopes.
34
-------
'-
SECTION BS (SWLI-WAY PROF.LJJ
EMERCfNCV S
To» Or D»M tttv «4 *
PLAN VlCW OF DAM 15P1LLWAY
tlliTINC C«*0t
ELEVATION FROM DOWNSTREAM
FIGURE 15. Construction Drawing of Pond Number 6
-------
FIGURE 16. Overall View of Pond Number 6
1
FIGURE 17. Inlet Channel to the Pond with
Debris Across It
-------
FIGURE 18. Erosion of Road Caused by Overflow
Through the Emergency Spillway (Pond No. 6)
FIGURE 19. Overall View of Pond Number 7
37
-------
CO
02
mWd.0 d.o*,flUr
.,.»-.... r.»^f.»w..-.
EMBANKMENT PROFILE ALONG poiNriPfll SPILLWAY 4
* (act* ft)
STAGE-AREA STORA
SB*
IMIRGJNC\ SPILLWAY PROFILE
LMLRCENCY SPILLWAY StCTIOIN
C£NTERLINE CPOSS SLCTIQN
;-.,.,.-,,'.. line 5
PLAN VIEW ON 4'CONTCKJR INTERVAL
FIGURE 20. Construction Drawing of Pond Number 7
-------
The pond had a negative removal efficiency, i.e., a higher
suspended solids concentration in the effluent than in the
influent toward the end of the baseline sampling period.
This was due to the presence of algae in the outflow samples.
The algae were present on the pond surface and attached to
the riser pipe. Toward the end of the sampling period, some
Of these algae broke loose and entered the pond outflow.
On the other hand, the algae deposits around the perforated
riser pipe acted as a filter, retaining most of the suspended
solids in the pond and thus resulting in a cleaner discharge
through the outflow during the measured rainfall event. The
rain during this period of sampling was intermittent with
periods of high intensity rain. The total amount of rain
recorded was 2.21 cm (0.87 in.). During the rainfall event
the relatively high inflow to the pond was observed to cause
short circuiting of the flow through the pond. The overall
performance of the pond was good.
POND NUMBER 8
The purpose of this pond is twofold: to control sediments
generated by surface mining activity upstream, and to supply
water for an adjacent deep mine. This is a relatively well-
built pond consisting of an earth embankment approximately
6.1 m {20 ft) high, with a 0.92 m (3 ft) square steel drop
inlet and a 76.2 cm (30 in.) diameter steel spi1Iway_pipe.
The emergency spillway consists of an expensively built
concrete channel. The embankment and its side slopes were
well-vegetated but the side slopes of the pond itself showed
signs of degradation. Sloughing of the slopes into the
impoundment was observed. The construction drawing of the
pond is presented in Figure 21. Figure 22 is an overall
view of the pond.
The pond was observed to be ineffective in removing suspended
solids during the baseline sampling period. An average ef-
ficiency of -128 percent during the six and one-half hour
measured baseline reflects some unusual operating conditions
during that specific time. The location of the pump intake
for the deep mine was very close to the riser pipe which
is the outflow for the pond (Figure 23). The action of the
pump resulted in a local disturbance within the pond, re-
suspending the deposited sediments which were subsequently
carried out the outflow.
Although the suspended solids content of the influent during
the storm event was relatively high, the effluent was cleaner
than during the baseline conditions and met all State_and
Federal discharge criteria. The design and construction of
39
-------
Emergency Sp/7/Hfg
Profile
Emergency Spil/ivay
Section
3o"dia principal
spillway
fc base
230 o
FIGURE 21. Construction Drawing of Pond Number 8
-------
FIGURE 22.
Overall View of Pond Number 8
Showing the Pumping Arrange-
ments for the Deep Mine and
Eroding Side Slopes
the pond was adequate as far as removal of suspended solids
was concerned, but little consideration was given to the
downstream effects of the outflow from the principal and
emergency spillways. The discharge water flows directly onto
unstabilized dirt road (Figure 24). The water then flows
along the dirt road for some distance until it finally flows
across the road and discharges into the natural watercourse
(right-hand side of Figure 24). In the process, the road is
eroded and the sediments are carried into the natural
waterway.
POND NUMBER 9
This is a combination of dugout and embankment type sediment
pond. The capacity of this pond was increased by hollowing
out the natural stream channel across which the embankment
was built. An embankment approximately 2.1 m (7 ft) high
was constructed with three 50.8 cm (20 in.) diameter steel
outflow pipes under a grouted riprap emergency spillway.
Figure 25 shows the construction drawing of this pond.
Figure 26 is an overall view of the pond, looking toward the
dam.
an
41
-------
FIGURE 23. Close View of Pond Outflow Riser
Pipe, Access Deck, and Pumping Unit for
Deep Mine
FIGURE 24. Outflow from the Pipe (Left) onto
the Dirt Road which Eventually Flows into
the Natural Waterway (Right-Hand Side)
42
-------
DETAIL A
SPILLWAY
SCALE I »
EARTH FILL VWTER
BOTTOM LEVEL OF POND
/
/ SPILLWAY
SECTION AA
. ORIGINAL GROUND
PLAN VIEW
43.560
AS Bu.^T MEASU
500 150 * 4
EARTH FILL WATER,
BOTTOM LEVEL OF POMP
PROFILE OF POND
FIGURE 25. Construction Drawing of Pond Number 9
-------
FIGURE 26. Overall View of Pond Number 9,
Looking Toward the Dam
FIGURE 27.
Sediment Deposits at Upper
End of Pond
44
-------
The side slopes of the pond and the embankment itself were
well-vegetated. Normal overflow occurs through the three
steel pipes below the emergency spillway. These pipes dis-
charge their water on the downstream face of the emergency
spillway. Thus, streambed erosion downstream of the dam due
to normal discharge was kept to a minimum. Inflow to the
pond is from the main channel and a small seep which enters
the pond from its northern side. However, the main stream
contributes over 97 percent of the inflow to the pond.
The pond was quite effective in removing suspended solids
during the measured baseline conditions, but was less ef-
fective during the rainfall event. In the time period
between the initial baseline sampling and the sampling
during the rainfall event, the pond continued to rapidly
fill with sediment. By the time the pond was sampled during
the rainfall event a few months later, the upper one-half of
the pond was essentially completely filled with sediment,
i.e., the sediment has accumulated to within a few centi-
meters of the water surface as seen in Figure 27. This
rapid accumulation of sediment was found to be due to
logging in the watershed which preceded the mining operation,
The haul road for the logging trucks paralleled the stream
and, for at least one mile of its length, ran right in the
streambed itself. Lumber trucks were observed to be tra-
versing this road/streambed at the rate of approximately one
per hour while field personnel were at the site in the
spring of 1975. During this period of lumbering activity,
the strip mining operation was observed to contribute very
little sediment directly to the pond. Thus, the rapid
filling of the pond was due mainly to the use of the stream-
bed and floodplain as a haul road by the lumber trucks.
45
-------
SECTION VII
OBSERVATIONS AND ANALYSES OF FIELD DATA
As described earlier, each of the nine ponds was sampled
under two different conditions, generally referred to as a
baseline (nonstorm) condition and during a rainfall event.
Tables 4 and 5 present the results of the sampling program
for these two conditions. The objective was to obtain an
indication of how each pond responded under two different
operating conditions.
During most of the sampling periods the variation in the
rate of inflow to the pond over the period of sampling was
minor. The pond removal efficiencies and detention times in
such cases were calculated using the average flow rate.
When a wider flow range occurred, detention times and ef-
ficiencies were calculated for the minimum and maximum flow
rates.
The percentage of solids actually removed by each pond was
determined by using the equation derived for a simple mass
balance for a conventional containment basin given as
Equation 1 in Section V. The solids concentrations of the
influent and effluent used in Equation 1 were obtained from
the inflow and outflow water quality samples taken during
the course of the field surveys. The average influent and
effluent suspended solids concentration during the period of
sampling was used in this equation to solve for the actual
removal efficiency.
The theoretical efficiency was determined using Stokes1 Law
(see Appendix B), Using the measured surface area and in-
flow to the pond, the critical settling velocity was com-
puted as:
vc =
where: Vc = critical settling velocity
Q = pond inflow
A = pond area
46
-------
Table 4. RESULTS OF POND SAMPLING DURING THE
BASELINE CONDITION
Pond
no;
1
2
3
4
5
6
7
8
9
Flow Computed
average/range detention time
(m3/sec) (hr)
0.014
0.015-0.006
0.028
0.020
0.017
0.064
0.011
0.034
0.122
49.4
31.9-75.3
12.9
10.5
15.2
213.0
17.3
72.2
8.0
Sampl Ing
Period
(hr)
2
2
2
2
2
2
2
6h
2
No. of
Samples
8
8
8
8
8
8
8
7
8
Average suspended
solids con. (mg/1)
Inf 1 uent
<5
1412
1876
5181
1616
954
13
43
324
Effluent
<5
12
200
128
100
23
15
97
31
Actual removal
efficiency
(%)
*
99.2
89.3
97.5
93.8
97.6
-16.0
-128.1
90.4
Theoreti cal
removal
efficiency
(*)
99.0
98-99
90.0
95.0
95.0
98.0
98.0
93.0
94.0
-------
CO
Table 5 . RESULTS OF POND SAMPLING DURING
RAINFALL CONDITIONS
Pond
no*.
1
2
3
4
5
6
7
8
9
Flow
average/ range
(m3/sec)
0.021
0.028
0.149
0.133
0.060
0.042
0.012-0.093
0.013
0.056-0.110
Computed Sampling
detention time Period No. of
(hr) (hr) samples
31
7
4
5
325
.9
-
.8
.4
.2
.0
20.8-2.7
184
5
.4
.7
2
2
4
4
5
26
16
5%
7
8
8
8
16
9
8
9
8
10
Average suspended
solids con. (mq/1 )
Influent
474
239
21970
9643
668
868
765
363
412
Effluent
196
17
11539
6198
275
35
66
28
193
Actual removal
efficiency
(*)
58.
92.
48.
36.
58.
95.
91.
92.
53.
8
8
0
4
8
9
3
3
1
Theoretical
removal
efficiency
(X)
95.0
88.0
83.0
84.0
91 .0
99.0
83.0-67
97.0
99.0
.0
-------
This computed critical settling velocity, along with the
measured specific gravity of the incoming suspended sediment
was then used in Stokes1 Law to determine the diameter of
the smallest particle which would theoretically settle at
that critical settling velocity. The formula used was:
where: Vr = critical settling velocity, cm/sec
2
g = acceleration due to gravity = 981 cm/sec
D = diameter of a spherical particle, cm
S = specific gravity of the particle
v = kinematic viscosity of water, cm2/sec
The kinematic viscosity of water was determined based on the
measured temperature of the inflow to the pond.
This calculated particle diameter was compared to the
measured grain size distribution of the incoming suspended
sediment (Appendix C) and the percent of particles finer
than this size was found. This percent finer was the
theoretical removal efficiency of the pond.
The theoretical effect of short circuiting on the efficiency
was also computed for some of the ponds where this effect
was thought to be a problem. However, theoretically, short
circuiting was never found to cause a significant difference
in the ideal settling for any of the ponds studied.
Computations of sediment loading and accumulation for the
two sampling periods and during the life of pond were also
made. These computations were performed in order to get an
estimate of the amount of sediment generated in the water-
shed over the life of the pond and the amount entering the
pond during the sampling periods. The results of these
calculations are presented in Table 6. The sediment accumu-
lation over the life of the pond was computed by assuming
that the settled sediment had an in-place water content o.f
50 percent. Using this value and knowing the approximate
life of the pond, the total weight of sediment accumulated
over the life of the pond was calculated by utilizing the
data on volume and specific gravity of the settled sediment
collected during the field surveys. The life of the pond
was determined from State approval and inspection records
and through discussions with the mine foreman. Sediment
loading during the sampling periods was calculated through a
simple mass balance between the suspended solids concentra-
tion in the inflow versus the suspended solids concentration
in the outflow, again using the flow data measured during
the course of the field surveys.
49
-------
Table 6. ESTIMATED SOLIDS ACCUMULATION
en
o
Pond
no.
1
2
3
4
5
6
7
8
9
During
Period
(hrs)
2
2
2
2
2
2
-
-
2
baseline
Metric
ton/hr
neg.
0.05
0.17
0.36
0.09
0.21
-
-
0.13
m3
neg.
0.04
0.13
0.28
0.11
0.17
-
-
0.10
During
Period
(hrs)
2.0
-
4.0
4.0
5.0
4.0
4.0
5.5
7.0
storm event
Metric
ton/hr
0.02
-
5.62
1.63
0.08
0.07
0.11
0.02
0.06
n,3
0.02
-
8.29
2.54
0.26
0.12
0.16
0.03
0.16
During
Period
(mo)
20
-
12
9
-
-
24
10
6
life of pond
Metric
ton/day
1.00
-
8'. 44
5.99
-
-
0.57
4.81
14.88
m3
2.29
-
1125
624
-
-
161
534
1035
-------
Table 7 gives range of the observed suspended solids con-
centrations, turbidity, and pH of the measured pond ef-
fluents during the two sampling periods and comparisons of
these parameters with the Federal and various State stan-
dards for effluents from surface mining operations. A
discussion of the Federal and State standards has been
presented in Section IV of this report.
51
-------
Table 7. COMPARISON OF OBSERVED EFFLUENT QUALITY
WITH VARIOUS EFFLUENT STANDARDS
ro
Suspended solids
(mg/1)
Baseline
Federal*
State:*
Pennsylvania
West Virginia
Kentucky
Pond:
#1
#2
#3
#4
#5
$6
#7
#8
#9
Low
30
-
-
-
1
7
121
24
54
3
4
80
14
Mean
-
-
-
-
3
12
200
128
100
23
15
97
31
High
100
60
-
-
4
18
429
412
158
44
39
113
52
Storm event
Low
30
-
-
-
152
13
5160
3408
110
20
11
16
107
Mean
_
_
-
-
196
17
11539
6198
308
35
66
28
193
High
100
60
-
-
235
20
41840
8437
521
43
340
50
341
Turbidity
(JTU)
Baseline
Low
_
_
-
-
3
5
100
19
50
25
2
90
10
Mean
_
_
-
-
5
9
148
75
91
37
3
115
15
High
_
_
200
150
7
15
300
270
160
45
4
130
26
Storm event
Low
_
_
-
-
120
12
1000+
1000+
130
24
10
25
170
Mean
_
_
-
-
138
16
-
-
273
42
34
32
207
High
_
_
1000
1000
160
21
-
-
380
50
85
50
260
PH
Baseline Storm
Low
6.0
6.0
5.5
6.0
7.3
7.1
6.8
7.2
6.6
6.2
7.1
6.1
6.6
High
9.0
9.0
9.0
9.0
7.5
7.4
7.0
7.6
6.7
6.5
7.3
7.0
6.7
Low
6.0
6.0
5.5
6.0
7.4
7.3
5.7
6.6
6.1
6.4
5.9
6.4
6.5
event
High
9.0
9.0
9.0
9.0
7.5
7.4
5.9
6.8
6.5
6.6
8.1
6.8
6.8
For detailed Federal and State effluent standards, see Table 2.
Pennsylvania has no minimal numerical limit on suspended solids or turbidity. However, for the evaluation
and certification of NPDES applications, the State follows guidelines for suspended solids which Indicate
that discharges should average no more than 30 mg/1 monthly with maximum discharges not to exceed 60 mg/1.
-------
SECTION VIII
DISCUSSION
REMOVAL EFFICIENCY
It 1s evident from Table 4 that most of the sampled ponds
have high suspended solids removal efficiencies during the
measured baseline or non-storm conditions. Ponds 7 and 8,
which showed negative efficiencies because of some abnormal
and unusual conditions prevailing at the time of sampling,
are the exceptions. In Pond 7, algae were present on the
pond surface. The algae broke loose during the sampling
period and entered the outflow. In Pond 8, disturbances due
to the action of an intake pump for a deep mine located
close to the riser pipe1 caused resuspenslon of settled
sediments, which were carried into the outflow. The removal
efficiencies of the remaining ponds, operating under normal
conditions, were measured to be approximately 90 percent or
greater during the baseline conditions.
As seen from Table 5, the efficiencies during the storm
event were generally much lower than during the baseline
conditions. In particular, Ponds 3 and 4, the two ponds in
eastern Kentucky, gave a poor performance during high flows.
The poor performance of Pond 4 was due to the high inflow
velocity to the pond and short circuiting within the pond,
resulting in resuspenslon of settled sediments. This could
have been controlled by the construction of simple velocity
checks at the inflow to the pond. In Pond 3, the poor con-
struction and maintenance of the pond caused severe erosion
of the emergency spillway channel, resulting in the poor
pond performance.
The effectiveness of all ponds could have been greatly im-
proved if better operation and maintenance procedures were
instituted. Some of the parameters which led to overall
poorer performance than expected included:
(1) Ponds which had been in existence for a long
period of time had almost exhausted their capacity
53
-------
to store sediment. In many cases the deposited
sediments were resuspended due to high inflow
velocities or other disturbances and were sub-
sequently carried out the outflow. This high-
lights the need for timely cleaning of the ponds.
(2) Many principal spillway pipes were clogged and
needed cleaning. As a consequence, water was
escaping through the emergency spillway or eroding
other portions of the containment berms. Thus,
inspection of the pond should be performed by mine
personnel on a daily basis so that any required
maintenance can be performed immediately.
(3) Erosion of poorly vegetated and steep pond side
slopes contributed to poor effluent water quality.
(4) During high flows in the pond, sediments were
carried through the perforations in the outflow
riser pipe due to less detention time being avail-
able for the particles to settle in the pond.
Only Pond 2 (an off-channel, dugout pond) and Pond 6 (the
pond with the greatest surface area) showed high suspended
solids removal efficiencies under both sampling conditions.
It may not be physically possible to construct ponds with a
large surface area such as Pond 6 at most surface mining
operations. However, where slopes are steep, multiple ponds
may provide an effective alternative to large ponds.
Off-channel, dugout type ponds appear to be highly effective
because the surface runoff from the mining area does not
flow directly into the pond. Instead, it first flows into
the pit area where some settling of the suspended load
occurs. From there it is pumped into the sediment pond.
Thus, the inflow to the sediment pond can be more precisely
controlled and results in a higher final effluent quality.
These ponds are most commonly constructed to control sedi-
ments from area surface mining operations. In actual
practice, the pit area in area surface mining operations
functions as a primary settling basin and thus helps to
increase the final effluent quality. Because of its high
efficiency and low maintenance requirements, the off-channel,
dugout type sedimentation pond appears to be the most reliable
solution to the problem of sediment control from surface
mining activity. However, construction of an off-channel,
dugout type of pond may not always be feasible because of
geographical and physical constraints.
54
-------
One problem which may be encountered with off-channel type
ponds is that it may not be able to site a single pond so as
to collect all the runoff from the entire disturbed area.
This would necessitate the building of more than one sedi-
ment control structure so that sediment from the entire
disturoed area can be controlled.
Theoretical efficiency as predicted by Stokes1 Law was
essentially the same as the actual efficiency under baseline
conditions for the ponds which operated under normal condi-
tions. During the rainfall event, however, there was
generally little or no correlation between the theoretical
and actual efficiencies as seen in Table 5. The predicted
efficiencies were found to be much higher than the actual
efficiencies in most cases. Many deficiencies are inherent
in thi use of Ideal Settling Theory, i.e., Stokes1 Law in
predicting the efficiency of irregularly shaped sediment
ponds. The theory does not adequately account for the local
disturbances within the pond. The pond removal efficiency
is extremely sensitive to these local disturbances. The
theory is applicable for the settling of discrete particles
of uniform size, shape, density, and specific gravity, which
usually is not the case in practice. Also, the theory does
not adequately take into account other parameters such as
the location of the inlet and outlet, and the depth and
shape of the pond.
DESIGN CONSIDERATIONS FOR IMPROVED PERFORMANCE
Actual efficiencies of all ponds with positive efficiencies
during the baseline and rainfall event were plotted against
their computed detention time (Figure 28) and overflow
velocity (Figure 29). The overflow velocity was calculated
as the ratio of pond discharge to pond surface area, and the
detention time was calculated as the ratio of the total
water storage to the discharge from the pond. These two
plots indicate that for the ponds sampled under this study,
a suspended solids removal efficiency of approximately 90
percent can be obtained if the pond has:
(1) A detention time of at least 10 hours
_ 5
(2) An overflow velocity of less than about 2x10
m / s e c.
One of the reasons for the good performance of Pond 6 was
the accumulation of debris and trees at the inflow to the
pond, resulting in a reduction of the inflow velocity and
consequent deposition of sediment before it reached the pond
55
-------
100
I
OJ
i
<)
i..;
-
O
V
10 100
Detention Time, hr
1000
FIGURE 28. Removal Efficiency versus Detention Time.
56
-------
100
30
10
Overflow Velocity, m/sec
FIGURE 29. Removal Efficiency versus Overflow Velocity
57
-------
or in the upper reaches of the pond. By using this princi-
pal and constructing some type of energy dissipater(s) in
the stream just upstream of the pond, the amount of sus-
pended solids removed by the pond can be increased. One
such device could be a log structure as shown in Figure 30 .
Sediment basins constructed across the natural stream may
solve the sedimentation problem only temporarily. Locating
the basin off stream by temporarily diverting the main
stream, as shown in Figure 31, will help solve some of the
problems inherent in in-stream sediment basins. After the
completion of mining, the stream can be rerouted to its original
alignment with a minimum disturbance of the environment.
Some of the problems of disposing of accumulated sediment
can be solved by building an embankment across the main
stream and providing the required storage capacity of the
basin by excavating the stream bed, as shown in Figure 32 .
The object of this approach is to leave the stream at its
original profile after the mining activity has ceased and
the embankment has been removed.
Perforations in the outflow riser pipe allow sediment to
flow through the openings. The concept of using a perfor-
ated riser pipe in a sediment control structure for surface
mining is questionable. This type of riser is generally
used in sediment ponds in urbanizing areas. The ponds are
designed to be dry ponds for safety purposes, i.e., to pre-
vent drownings.
Instead of using a perforated riser pipe, the siphon arrange-
ment as shown in Figure 33 could be tried to achieve two-
fold benefits:
(1) There are no perforations for sediment to
escape through as the pond fills.
(2) The siphon pipe can be located at the approximate
elevation of the desired cleanout level of the
pond. This would help in implementing cleanout
procedures when the required pond storage capacity
is used up.
WATER QUALITY CRITERIA
Designing a pond to meet a specific water quality criterion
is difficult, because of the many variables which are not
normally known but which must be taken into account. The
factors which must be known or assumed before an analysis
can be made are:
58
-------
Debris
Logs
FIGURE 30 Plan View of Conceptual Log Structure Upstream
of a Sediment Pond, Acting as an Energy Dissipator
Main Stream
Divert Stream To
Provide For Storage Of
Sedi ment
Embankment
(Restore Stream After
Completion of Mining
Activi ty)
FIGURE 31. Plan View of Off-Stream Sediment Pond
59
-------
Embankment
Original
Profile of Stream
FIGURE 32,
Excavation To
Provide Required
Storage
Profile View of Stream Excavation for
Sediment Storage
Riser
Flow
4" pipe
1/4" hole at
sediment
cleanout
level
Sediment
cleanout level
Elev. of top of conduit
FIGURE 33 . Siphon Arrangement in Riser Pipe.
60
-------
(1 ) Design flow rate
(2) Expected grain size distribution of the
incoming suspended sediment
(3) Anticipated suspended solids concentration
in the inflow
(4) Specific gravity of the incoming solids
(5) Anticipated pond water temperature
Nevertheless, for comparative purposes an analysis was made
on one of the measured ponds to determine the pond area
requirements for various assumed effluent standards. To
illustrate this relationship, the analysis was performed on
Popd 3 for the inflow conditions existing during the base-
line sampling period. Under these conditions, the pond had
a measured outflow water quality of 200 mg/1. The theoretical
suspended solids removal efficiency agreed closely with the
measured removal efficiency (see Table 3).
Figure 34 shows the computed, required pond areas versus
effluent quality. As can be seen from this figure, in this
case the area requirements rapidly become very large as the
required effluent quality approaches 100 mg/1 or less.
This example illustrates the type of analyses which should
be performed before any effluent quality criteria are chosen.
As illustrated, the pond area required to meet a specific
effluent water quality criterion may become quite large if
high flow rates, many fine-grained particles, or high
suspended solids concentrations are present in the inflow.
Pond areas can be reduced, of course, by reducing any of
these three variables. For example, the suspended solids
concentration and amount of fine-grained particles in the
inflow can be reduced by good and timely site erosion con-
trol and reclamation practices. Flow rates can be reduced
by building off-channel ponds,
STATE REGULATIONS
The design criteria currently used are thorough, especially
in Kentucky and West Virginia, for such things as dam con-
struction, etc, However, no State has regulations which
provide for maximum suspended solids removal. There are
also definite gaps in defining the requirements for the
removal and disposal of the accumulated sediments, requiring
the maintenance and repair of sedimentation ponds, and pro-
viding for the dismantling of the structure after the mining
61
-------
120
160
200
Effluent Quality, rng/1
FIGURE 34.
Required Pond Area versus Effluent Quality
Pond 3, Baseline Conditions
62
-------
activity is terminated. The structures which are built
across a natural stream may fail during high intensity
storms, discharging both the accumulated sediment and the
earth embankment itself into the stream. The problem of
sediment control from surface mining activity is thus only
temporarily solved in such cases since the sediment pollu-
tion was only postponed until some time after the mining has
ceased. At that time the solution becomes more difficult
because the mine operator is not available to rectify the
problem.
Ideally, the entire surface mine sediment control scheme
should be planned and executed in four phases:
(1) Preparation of adequate designs and drawings
(2) Construction in accordance with approved design
and drawings
(3) Maintenance and provisions for mitigation of off-
site and downstream damages
(4) Disposal of trapped sediments after completion
of mining activity
The first phase is adequately covered in the State of
Kentucky and West Virginia regulations, but all the other
phases need more consideration. Timely and proper consider-
ation of all of the four phases will yield better results.
Construction of a highly effective pond without considering
the possible downstream, off-site effects of the pond dis-
charge can often cause more erosion and sedimentation prob-
lems than it solves. As can be seen in Pond 8, the pond was
well designed and well built, but the discharge from the
pond flowed directly across an unimproved dirt road, result-
ing in erosion of the road and the transport of the eroded
sediments into the natural waterway. Also, the efficiency
of Pond 6 during both baseline and rainfall event conditions
was measured to be over 95 percent, but the overflow from
the emergency spillway was causing serious erosion problems
to a dirt road downstream.
63
-------
SECTION IX
REFERENCES
1. "Standards and Specifications for Soil Erosion and
Sediment Control in Urbam'zing Areas," SoilConser-
vation Service, U.S. Dept. of Agriculture, 1969.
2. Becker, Burton C., D.B. Emerson, and M.A. Nawrocki,
"Joint Construction Sediment Control Project," U.S.
Erwrionmental Protection Agency, Report No. EPA-
660/2-73-035, April 1974.
3. Effluent Limitation Guidance for the Refuse Act
Fermit Program, Coal Mining Industry, U.S. Environ-
mental Protection Agency, September 5, 1972.
4. Mallory, C.W., and M.A. Nawrocki, Containment Area
Facility Concepts for Dredged Material Separation,
HFying, and Rehandling, U.S. Army Engineer Waterways
Experiment Station, Contract Report D-74-6, October
1974.
5. Clark, B.J., and M.A. Ungersma, eds., Wastewater
Engineering: Collection, Treatment. Disposal,
Metcalf & Eddy, Inc., McGraw-Hill, New York, 1972.
6. Fair, G.M., J.C. Geyer, and D.A. Okun, Water and
Wastewater Engineering, Wiley, New York, 1971,
p. 368.
7. Camp. T.R., "Sedimentation and the Design of Settling
Tanks," Transactions of the American Society of
Civil Engineers. Vol. 111. 1946. pp. 895-958.
8. Schwab, G.O., R.K. Frevert, T.W. Edminster, and
K.K. Barnes, Soil and Water Conservation Engineering,
2nd Edition, John Wiley and Sons, Inc., 1966.
9. Musgrave, G.W., "A Quantitative Evaluation of Factors
in Water Eros1on--A First Approximation," Journal of
Soil and Water Conservation. Vol. 2, No. 3, July 1947.
64
-------
APPENDIX A
Contained herein are comparative summaries of the various
design, construction, and maintenance aspects of the regula-
tions pertaining to surface mine sedimentation ponds in the
three States of primary interest, i.e., Kentucky, Pennsyl-
vania, and West Virginia, For the sake of comparison, the
SCS standards and specifications for sediment basins adopted
by the State of Maryland have been included since the design
standards for sediment control structures in the State of
Maryland are considered to be among the most advanced in the
country.
Also included in Table A-ll are brief summaries of the
status of regulations that pertain to the use of sediment
ponds in conjunction with surface mining activities in other
eastern States and by TVA.
65
-------
Table A-T. CONSTRAINTS ON SIZE AND TYPE OF BASIN
State
scs
(Maryland)
Kentucky
Pennsylvania
West Virginia
General
Specification applies only
to sediment basins that are
temporary in nature and
will be removed upon com-
pletion of the development
period. The practice ap-
plies primarily to areas
where land grading opera-
tions are planned or under-
way. It 1s used as a tem-
porary measure until areas
above the Installation are
permanently protected
against erosion by vegata-
tlve or mechanical means.
Standards establish mini-
mum acceptable quality for
design and construction of
debris basins located In
predominately rural
or agricultural areas 1n
Eastern Kentucky. The
debris basin must conform
to ill state and local
laws and/or regulations
pertaining to storage of
water.
Failure of the structure
Mould not result in loss
of 1Ife; in damage to
homes, commercial or
Industrial buildings;
main highways, or rail-
roads; in Interruption
of the use or service of
public utilities; or
damage existing water
Impoundments.
Standard establishes rninf-
num acceptable quality for
the design and construc-
tion of sediment dans lo-
cated 1n predominantly rural
or agricultural are* In
West Virginia.
Sane as Kentucky (See
above)
Structure Height
Class "X" - 10 feet
Class "B" - water
surface area at
crest elevation of
pipe spillway shall
not exceed nine (9)
feet measured up-
ward from the
original stream
bed.
The vertical dis-
tance between the
lowest point along
the center line of
the dam, excluding
the channel section,
and the crest of the
emergency spillway
does not exceed
20 feet.
Storage Volume
Class "X" - less
than 1 million
gallons storage
capacity below
the pipe spill-
way crest
The vertical dis-
tance between the
lowest point along
the center line of
the dam and the
crest of the emer-
gency spillway does
not exceed 15 feet.
Contributing
Drainage Area
Class "B" - the
drainage area
shal1 not ex-
ceed one hun-
dred fifty (ISO)
acres.
The product of
the storage
times the effec-
tive height of
the dam does not
exceed 3000, where
the storage is
defined as the
original volume
(acre-feet) In,
the reservoir at
the elevation of
the crest of the
emergency spill-
way and the ef-
fective height
of the dam is
defined as the
difference in
elevation (feet)
between the emer-
gency spillway
crest and the
lowest point In
the cross-section
taken along the
centerl ine of
the dam.
Not to exceed a
surface area at
emergency spill-
way crest greater
than 10 acres.
Not to exceed
300 acres
Not to exceed
200 acres.
-------
Table A-2. REQUIRED STORAGE CAPACITY
State
Requirement
SCS (Maryland)
Kentucky
Pennsylvania
West Virginia
Site should be selected to provide adequate storage
for not less than 0.5 in. per acre of drainage area.
Volume for trap efficiency calculations shall be
the volume below the emergency spillway crest or
pipe spillway crest if there is no emergency spillway.
Sediment pool shall have a minimum capacity (from
the lowest elevation in the reservoir of the crest
of the principal spillway) of 0. 2 acre-ft per acre
of disturbed area in the watershed.
The disturbed area includes all land affected by
previous operations that are not presently stabilized
and all land that will be affected throughout the
life of the structure.
V = (AIC) + (AIC/3)
V = volume in cu ft
A = maximum area draining to the pit in sq ft
I = rainfall (in.) per 24 hr detention time (hr)
C = constant = % of rainfall not absorbed by
soils (runoff)
The sediment pool shall have a minimum capacity
(from the lowest elevation in the reservoir to the
crest of the principal spillway) to store 0.125
acre-ft per acre of disturbed area in the watershed.
The disturbed area includes all land affected by
previous operations that is not presently stabilized
and all land that will be affected during surface
mining and reclamation work.
67
-------
Table A-3. BASIN CLEAN-OUT
State Requirement
SCS (Maryland) Sediment basin shall be cleaned out when
the effective storage capacity drops below
0.2 inches per acre of drainage area,
The elevation corresponding to this level
shall be determined and given in the design
data as a distance below the top of the
riser.
Kentucky No provisions
West Virginia The basin shall be cleaned out when the
sediment accumulation approaches 60 per-
cent of the design capacity.
The design and construction drawings shall
indicate the corresponding elevation.
Pennsylvania No provisions.
68
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Table A-4. SPILLWAY DESIGR CAPACITY CRITERIA
State
Principal spillway
Emergency spillway
Remarks
SCS (Maryland)
Kentucky
10
Pennsylvania
West Virginia
Hust be designed to handle
not less than 5" runoff
fro» the drainage area for
24 hrs. (1 .e.. 5" runoff
or 0.21 cfs per acre of
drainage area)
Minimum spillway size is
based on total drainage
area above the structure
and can be obtained from
prepared tables.
Based on 4" rainfall over
a 24 hr. period times (x)
the detention time in days
or parts of a day (6 hr.
minimum detention time)
Minimum size is based on
total drainage area above
structure and can be ob-
tained from prepared
tables.
Hininun capacity will be
that required to pass the
peak flow from design
storm (10 yr. frequency)
less any reduction credit-
able to the pipe spillway.
Designed to safely carry the
expected peak rate of dis-
charge from a 10-year fre-
quency storm. The 10-year
frequency peak discharge
can be obtained from charts
prepared for that purpose.
Designed to safely carry the
expected peak rate of dis-
charge from a 10-year fre-
quency storm. The 10-year
frequency peak discharge
can be obtained from pre-
pared figures. Emergency
Spillway may be waived when
the height of the embank-
ment is less than 5 feet
and when the drainage area
is 20 acres or less.
Coabined capacity of pipe
emergency spillway will,
where applicable, be designed
to handle a ten year
frequency storm.
Must have one foot freeboard
between the maximum design
flow elevation.
Must have one foot of free-
board between max. design,
flow elevation in emergency
spillway and the top of the
dam.
-------
Table A-5. INLET STRUCTURE DESIGN CRITERIA
State
Criteria
SCS (Maryland)
Kentucky
Pennsylvania
West Virginia
A. Crest Elevation
When used in conjunction with emergency spillways, the crest elevation of the
riser shall be at least 1 ft. below the elevation of the control section of
the emergency spillway. If no emergency spillway is provided, the crest
elevation of the riser shall be at least 3 ft. below the crest elevation of
the embankment.
The minimum difference in elevation between the crest of the principal
spillway and the emergency spillway on any structure shall be 1.5 feet.
No provision.
The crest of the principal spillway shall be located at the maximum elevation
of the sediment pond. When the emergency spillway is not required, the crest
elevation of the riser shall be at least 2 ft below the crest elevation of the
embankment.
B. Riser Perforations
SCS (Maryland)
Kentucky
Pennsylvania
West Virginia
The upper portion of the riser shall be perforated with 1-1/2 in. diameter holes
spaced 8 in. vertically and 10-12 in. horizontally all around. The perforated
portion shall be the top 1/2 to 2/3 of the riser.
Slots located in a horizontal plan in the top one-half (1/2) of the riser shall
be made as shown in Exhibit F of Kentucky Standards. In areas where water treat-
ment may be required, a deviation from this requirement will be considered.
No provisions.
Metal drop inlets when perforated shall be done so throughout the top 2/3 of
their length with 3/4 in. diameter holes spaced 8 in. vertically and 12 in.
horizontally center to center. Non-metal drop inlets shall be ported to permit
draining the pond in approximately 5 days. (Such ports shall be similar to
those described for the metal drop inlets).
-------
State
Table A-5. INLET STRUCTURE DESIGN CRITERlMcont.)
Criteria
SCS (Maryland)
Kentucky
Pennsylvania
West Virginia
C. Anti-Vortex Device
An anti-vortex device shall be used on the top of the riser if the
discharge values in the appendexed charts are used. If no anti-vortex
device is used, discharge values given In the charts must be reduced
by 50 %. An approved anti-vortex device is a thin, vertical plate
normal to the centerline of the dam and firmly attached to the top of
the riser. The plate dimensions are: length = diameter of the riser
plus 12 in.; height = diameter of the horizontal pipe.
An approved anti-vortex device is required on the principal spillway
inlet. (See Kentucky Standards Exhibit F.)
No provision.
An anti-vortex device shall be installed on the principal inlet.
1. It shall consist of a thin, vertical plate normal to the centerline
of the dam and firmly attached to the top of the riser. The plate
dimensions shall be: length = diameter of the riser plus 12 in.;
height = diameter of the horizonal conduit; or
2. It shall consist of a horizontal circular plate having a diameter
2 ft greater than the drop inlet and firmly mounted 1.5 ft above
the crest of the inlet.
SCS (Maryland)
Kentucky
Pennsylvania
West Virginia
D. Trash Rack
An approved trash rack shall be securely attached to the top of the riser.
A suitable trash rack will be provided where the drainage area will
contribute trash to the reservoir area.
No provision.
A suitable trash rack will be provided where the drainage area will
contribute trash to the reservoir area.
-------
Table A-5. INLET STRUCTURE DfSIGN CRITERIA(cont-)
State Criteria
E. Base
ro
SCS (Maryland) The riser shall have a base attached with a watertight connection .and shall
have sufficient weight to prevent floatation of the riser. Two approved bases
are: (1) A concrete base 18 in. thick with the riser imbedded 6 in. in the
base. The base should be square with each dimension 1 ft greater than the
riser diameter. (2) A 1/4 in. minimum thickness steel plate welded all around
the base of the riser to form a watertight connection. The plate shall be
square with each side equal to 2 times the riser diameter. The plate shall
have two ft of stone gravel or tamped earth placed on it to prevent floatations,
Kentucky The inlet shall have a base, usually concrete, attached with a watertight
connection.
Pennsylvania No provision.
West Virginia Same as SCS (Maryland) criteria.
-------
Table A-6. ANTI-SEEP COLLAR CRITERIA
State
Criteria
SCS (Maryland)
Kentucky
Pennsylvania
West Virginia
Conduits through embankments consisting of
materials with low silt-clay fractions shall
be provided with anti-seep collars where the
pipe diameter is 10 in. or
length should be increased
All Class "B" basins shall
one anti-seep collar.
greater. Seep
approximately 10%
have a minimum of
All conduits through the embankments are to
be provided with anti-seep collars. They
shall be placed along the conduit within the
saturated zone of the embankment at distances
of not more than 25 ft. Collars shall be of
the number and size required to increase the
seepage path along the conduit, a distance
equal to 15£ of the length of the conduit
within the embankment. The anti-seep collars
shall extend a minimum of 2.0 ft from the
conduit in all directions.
No provision.
All conuits through the embankment are to
be provided with a minimum of three anti-seep
collars, except when the embankment is 5 ft
or less. When the embankment is 5 ft or less,
2 collars will be required. The collars will
be at 15 ft intervals with the middle collar
at the centerline of the dam. The anti-seep
collars shall extend a mimimum of 2 ft from
the conduit in all directions. The collars and
their connections to the pipe shall be water-
tight.
73
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Table A-7. EMERGENCY SPILLWAY CONTROL STRUCTURE CRITERIA
1.
2.
3.
Parameter SCS (Maryland)
INLET CHANNEL
a. Length of level 10 ft
Section
b. Side slopes Not steeper than 2:1
c. Bottom width Same as control
section
CONTROL SECTION
a. Minimum bottom 8 ft
Width
EXIT CHANNEL
a. Bottom width
b. Side slopes Not steeper than 2:1
-c. Configuration
d. Bottom slope
Kentucky Pennsylvania
Minimum of No provision
30 ft
2:1 2:1
Minimum of
10 ft
10 ft
Minimum of No provision
8 ft
Rock 1/4:1 No provision
Earth 2:1
Trapezoidal No provision
Determined No provision
from Chart
#5 Kentucky
Standards
West Virginia
Minimum distance of
20 ft if Hpa2.5 ft,
30 ft if Hp>2.5 ft
2:1
Same as exit channel
10 ft
Minimum 10 ft
Rock 1/4:1
Earth 2:1
Trapezoidal
Determined from chart
#1, WV Standards
HP = Height of pool above emergency spillway control section.
-------
Table A-8. EMERGENCY SPILLWAY MAXIMUM
PERMISSIBLE VELOCITY
Type of spillway
State Earth Rock*
SCS (Maryland) 6 ft/sec
Kentucky 1. 5 ft/sec 14 ft/sec
2. 12 ft/sec if adequate
protection provided*
Pennsylvania No provision
West Virginia 1. 5 ft/sec 14 ft/sec
2. up to 12 ft/sec if adequate
protection is provided"*"1"
* A spillway is classed as a rock emergency spillway when durable bed-
rock occurs throughout the level section and in the exit channel to a
point opposite the downstream toe of the dam. Durable bedrock is de-
fined as a layer of continuous bedrock equal or greater in thickness
than the depth of flow through the spillway at the control section.
+ Spillways excavated in earth shall be protected through the level
section when the exit channel velocity exceeds 5 feet per second.
A maximum velocity of 12 ft per second will be allowed where ade-
quate protection is provided. The exit channel shall be protected
by using well graded riprap having a maximum size of 18 in. and an
average size of from 9-12 in. This riprap shall be placed at a
minimum thickness of 1.5 ft through the bottom and sides of the
control section and exit channel to a point beyond the toe of the
embankment.
When the exit channel velocity is from 10.0 to 12.0 ft per second,
the riprap shall be placed at a minimum thickness of 2.0 ft and
have a maximum size of 25 in. and average size of 15-18 in.
++ Spillways excavated in earth shall be protected throughout the
level section and the exit channel with durable rock riprap when
the exit channel velocity falls between 5 ft per second and 12 ft
per second. The rock riprap will be placed in a 1.5 ft thick
blanket through the bottom and sides of the level section and exit
channel. Twenty-five percent of the rock will be 18 in. or slightly
larger. The remaining 75% shall be well graded material consisting
of sufficient rock small enough to fill the voids between the
larger rocks. Shale shall not be used for riprap.
75
-------
Table A-9. FREEBOARD REQUIREMENTS
State
Freeboard requi rement
SCS (Maryland)
Minimum freeboard shall be 1.0 ft for
sediment basins with emergency spillways,
and 2.0 ft for those with no emergency
spi1Iway.
Kentucky
The settled elevation of the structure
shall be less than 2 ft above the
emergency spillway.
Pennsylvania
No provision
West Virginia
There shall be one ft of freeboard
between the maximum design flow eleva-
tion in the emergency spillway and the
top of the dam. When the emergency
spillway is not required, the crest
elevation of the riser shall be at least
2 ft below the crest elevation of the
embankment.
76
-------
Table A-10. EMBANKMENT CRITERIA
Design
parameter
Height
SCS {Maryland}
10 ft for Class »
Kentucky
(tBt -be high enough to
Pennsylvania
No provision
West Virginia
Must be high enough to
Top width
Side slopes
15 ft for £3
-------
Notes to Table A-10
* Paragraph A.3-4
The vertical distance between the lowest point along the center
line of the structure, including the channel section, and the
crest of the emergency spillway does not exceed 20 feet.
+ The minimum top width of the structure shall be as follows:
Maximum Structure height-feet Minimum top width-feet
15 or less 10
15-25 12
25-40 14
++ A cutoff to relatively impervious material shall be provided
under the structure along the center line and up the abutment
to the elevation of the crest of'the principal spillway. The
cutoff trench should have a bottom width adequate to accommo-
date the construction equipment but shall not be less than 8
feet. The trench shall have minimum side sloped of 1:1.
** The elevation of the top of a compacted cutoff will not be
lower than the crest of the principal spillway. The cutoff
trench should have a bottom width adequate to accommodate
the construction equipment but shall not be less than 8 feet.
The trench shall have a minimum side slope of 1:1. The cutoff
trench shall be located on the embankment center line and be
of sufficient depth to extend into a relatively impervious
layer of soil or to bedrock.
# The embankment, pool area and vegetated spillway shall be
fenced as needed to exclude livestock.
78
-------
Table A-ll. SEDIMENT BASIN REGULATIONS
OF OTHER STATES INVESTIGATED
State Regul ation
Illinois While the amended 1971 Surface-Mined Land Conser-
vation and Reclamation Act does not specifically
address sediment pond use and design criteria,
they do recognize that sediment ponds are sometimes
needed as an erosion control measure and are built
according to defined engineering standards.
Indiana Legislation governing the reclamation of surface
mined lands does not include criteria for the
design of sedimentation ponds. Where there is a
requirement for a sediment pond then Soil Conserva-
tion Service Criteria is utilized .
Virginia The Commonwealth of Virginia's coal surface mining
law does not prescribe precise design criteria and
specifications for sediment pond construction.
The law, however, does specify that a plan for
drainage control be attached to the operations
plan which shall provide for the proposed scheme
of drainage control.
Tennessee Since the State of Tennessee is a relatively small
producer of coal it lacks the personnel and research
facilities necessary for establishing sediment basin
design criteria. When sediment ponds and control
structures are required, operators and engineers
utilize the State of West Virginia's "Drainage
Handbook" which has proven effective in Tennessee
operations.
TVA The Tennessee Valley Authority has no specific
guidelines for sediment pond design. Depending on
where TVA purchases coal, individual states speci-
fications are followed in sediment pond design
criteria. In states where standards don't exist
TVA encourages the operator to construct numerous
small log or rock dams in drainage areas below the
operation. Guidelines for the use and design of
silt traps are adapted from a detailed erosion
control manual prepared in the late 1930's by TVA
engl neers .'
79
-------
APPENDIX B
BACKGROUND INFORMATION ON SEDIMENT PONDS
THEORY OF SETTLING
Sedimentation is the separation of suspended particles that
are heavier than water from water by gravitational settling.
On the basis of the concentration and the tendency of the
particles to interact, four general classifications of the
manner in which particles settle-can be made.5 It is not
only common to have more than one type of settling taking
place at a given time during a sedimentation operation, but
it is possible as well to have all four occurring simultan-
eously. The four classifications as described by Clark and
Ungersma are:
(1) Type-1 settling refers to the sedimentation of
discrete particles in a suspension of low solids
concentration. Particles settle as individual
entities, and there is no significant interaction
with neighboring particles. This type of settling
is called free or ideal settling.
(2) Type-2 settling is the process whereby a rather
dilute suspension of particles coalesce, or
flocculate, during the sedimentation operation.
By coalescing, the particles increase in mass and
settle at a faster rate.
(3) Type-3 settling occurs in suspensions of inter-
mediate concentrations, 1n which interpartlcle
forces are sufficient to hinder the settling of
neighboring particles. The particles tend to
remain in fixed positions with respect to each
other and the mass of particles settles as a unit.
This type of settling is generally called zone
settling,
(4) Type^4 settling or compression settling develops
when the particles are of such concentration that
a structure 1s formed. Further settling can only
take place by compressing the structure. This
80
-------
type of settling generally takes place in the
lower layers of a thick mixture. Compression is
due to the weight of particles which are con-
stantly added to the structure by sedimentation
from the upper layers.
jjeal Settling
Current practice in the design of sedimentation basins for
sediment control assumes the conditions of ideal settling.
Performance and design curves for the case of ideal settling are
illustrated in Figure B-l. As indicated in Figure B-l, the
settling velocity for a spherical particle of a given size
and specific gravity is governed by one of three flow
regimes: Stokes1 Law, Newton's Law, and the Transitional
Region. The governing equation for the settling velocity
within each flow regime is:6
(a) Stokes1 Law:
-1D2 Re<1
(b) Transitional Region:
r
r i K n K-i-
V = 2.32(S -l)Dlabv~U
-------
IO"9 )Q~
par|icl« Dianocfer, Cm.
\o
0/..-1
FIGURE B-l. .Ideal Settling Velocity for a Sphere (10uC'Water)
82
-------
These equations for Vs are implicit functions of the drag
coefficient for spheres. For each flow regime, the drag co-
efficient for a sphere becomes an approximate unique func-
tion of the Reynolds number.
However, suspended particles in water and wastewater are
hardly ever spherical. Drag coefficients for spheres, cyl-
inders, and disks differ significantly at high Reynolds
numbers (>1000). At low Reynolds Numbers (<10), the set-
teling velocities of rod-like and disk-like particles are,
respectively, 78 and 73 percent of the velocity of an equal-
volume spherical particle.6
Factors Affecting Ideal Settling
In the design of sedimentation basins under the assumptions
of ideal settling conditions, certain allowances must be
made for certain factors which affect ideal settling. These
factors include scour velocity, turbulence, and short cir-
cuiting effects.
Scour Velocity -
The actual dimensions of a clarifier tank or settling basin
of any given area are governed by the constraints imposed by
the scour velocity present. Scour velocity is defined as
the horizontal channel velocity required to start in motion
particles of size D, and is given by the equation:7
vc =
where: v = scour velocity, cm/sec
c
B = .04 for unigranular sand
>.06 for sticky, interlocking material
F = .02 to .03, friction factor
In settling tanks, the horizontal velocity through the tank
should be kept less than vc so that settled small particles
are not scoured from the bottom of the tank. The scour ve-
locity is seen to be independent of the dimensions of the
tank.
Turbulence -
The net result of turbulent diffusion is to decrease the re-
moval by settling of some desired particle sizes. Instead
of settling, the particles are carried out through the
83
-------
overflow. Camp? developed an expression whereby the removal
ratio is the fraction of particles of the given size that
would be settled with turbulence present in the clarlfier.
Thus, a removal ratio of 1.0 would mean that all particles
of that size or larger would be settled even with turbulence
present. This removal ratio is a function of the velocity
per unit of surface area of the settling zone. It should be
calculated for each settling tank configuration in order to
determine if turbulence effects are significant.
Short Circuiting -
The short circuiting phenomenon is defined as the condition
which occurs when some of the fluid travels through the set-
tling zone of a tank in less than the detention period.7 It
is emphasized by mixing the tank contents, high inlet
velocities, and density currents. A density current is
defined as the flow of one fluid into another relatively
quiet fluid whose density is different. Density differences
between the fluids may be due to differences in temperature,
salt content, or suspended solids content. If the detention
tank velocity is large enough, density currents will mix in
the tank with negligible effects on the overall flow pattern.
Such a tank is said to have a stable flow pattern. If
density currents remain intact through a tank, then the flow
pattern is unstable.
The shape of the concentration dispersion curve versus time
is a measure of the flow pattern through a tank. When these
curves are plotted in dimensionless terms, they can be used
to compare the hydraulic characteristics of different shapes
of detention tanks. Table B-l shows several types of tanks
and their measured relative times to the center of area of
the corresponding dispersion curve, ta/T, where ta is the
"probable flowing through time" of the fluid and T is the
detention time. The parameter ta/T is usually less than
unity. Smaller values for ta/T yield correspondingly
greater short circuiting problems.
As one proceeds down Table B-l, short circuiting is pro-
gressively less of a problem. The surface area required by
a given type of clarifier can be increased to approximately
account for short circuiting as follows:
A = F x 5.
a i-sc x v^
The short circuiting factor, F , in Table B-l is the reci-
procal of ta/T and can be determined separately for each
type of detention tank or basin.
84
-------
Table B-l. SHORT CIRCUITING FOR SETTLING TANKS
Short Circuiting
Type of Tank ta/T Factor
Ideal dispersion tank
Radial flow circular
Wide rectangular
(length 2.4xw1dth)
Narrow rectangular
(length I7xw1dth)
Baffled mixing chamber
(length - 528xw1dth)
Ideal basin
0.693
0.831
0.925
0.903
0.988
1.0
1.2
1.08
1.11
1.01
1.0
DESIGN BASIS
gn Parameters
In general, conventional sedimentation basins can be de-
signed to meet one or both of the following criteria:
(a) Retain a percentage of the total suspended solids.
(b) Removal of solids to meet a discharge water
quality selected for the receiving body of water.
In ideal settling (discrete particles of uniform size, uni-
form density, reasonably uniform specific gravity, and
fairly uniform shape), the removal efficiency of the sus-
pended solids will be dependent on the surface area of the
basin and detention time; the depth of the basin will have
little Influence, providing horizontal velocities are main-
tained below the scouring velocity. 5
Solids Removal -
The ability of the basin to retain the suspended sediment is
the primary consideration. The percentage of solids to be
removed will be set by one of the two criteria listed above.
85
-------
If the return water quality is the criteria, the percentage
of solids to be removed can be determined by the formula:
R(% solids removed) =
1 -
106
cl "
106
C2 "
1
1
I
1
100
where C, = solids concentration of influent, mg/1
C = solids concentration of effluent, mg/1
Design Particle Size -
The particle size to
centage of solids to
question is obtained
be removed is a function of the per-
be removed. The particle size in
by constructing a grain size distri-
bution curve of representative samples of incoming sediment.
Critical Settling Velocity -
The general procedure for sizing a sedimentation basin is to
select a critical settling velocity, Vc. corresponding to
the minimum particle size to be removed and its specific
gravity.5 The basin is then designed so that all particles
that have a terminal velocity equal to or greater than V
will be removed. The rate at which clarified water is pro-
duced is then:
Q = AVC
where A is the surface area of the sedimentation basin. The
equation can be rearranged to yield:
V = Q/A = overflow rate
This relationship shows that the overflow rate or surface
loading rate, a common basis of design, is equivalent to the
settling velocity and that for ideal settling the flow
capacity is independent of the depth.
For continuous flow sedimentation, the length of the basin
and the time a unit volume of water is in the basin {deten-
tion time) should be such that all particles with the design
velocity Vs will settle to the bottom of the basin. The
design velocity, detention time, and basin depth are related
as follows:
86
-------
Vs = depth/detention time
In actual practice, design factors have to be included to
allow for the effects of inlet and outlet turbulence, short
circuiting, etc., as previously discussed.
Overflow Rate -
The overflow or surface loading rate used for design purposes
should correspond to the peak discharge of the design storm.
The return frequency of the design storm is selected to
equate the cost of a given design to the probable protection
and service it will afford. Return intervals of two to ten
years are currently being used.l
Storage Considerations, -
In the design of conventional sedimentation basins, the
quantity of material to be stored is equally as important as
the ability of the basin to retain solids. The quantity of
material to be stored is estimated by approximate methods
such as the Universal Soil Loss Equation** or the Musgrave
approximation.9 Rules of thumb are also available. For
example, the SCS suggests that the site should be selected
to provide adequate storage for not less than 3.14 cm/ha
(0.5 inch per acre) of drainage area.l The storage require-
ments and the solids retention capabilities of the sediment
basin will be interrelated to the following extent:
(1) The storage volume of the sediment basin will be
the product of the surface area of the basin times
the total depth minus any freeboard required to
prevent bottom scour.
(2) The surface area must be adequate to provide both
the required storage capacity and the solids
removal capability required to meet return water
quality goals.
(3) Nonuniform deposition of materials will reduce the
solids retention capability of the containment
basin.
87
-------
APPENDIX C
Contained herein are the measured grain size dis-
tributions of the suspended sediment in the inflow
to the sampled ponds.
-------
U.S. STANDARD SIEVE OPENING IN INCHES U.S. STANDARD SIEVE NUMBERS
6 43 2 l'/J 1 % '/J % 3 4 6 8 1O 1416 20 30 40 50 70 1OO UO 200
HYDROMETER
IUU
-:
BC
70
t
0
| 60
£
£ 50
c
oo "J 40
l£> U
Of
HI
E
30
20
10
o
500
1
100
COBBLES
'
1
1 1 1
50 10
,
1
1
1 1
\
\
\
5 1
GRAIN SIZE
GRAVEL
COAKSE
HNE
'
^
s
\
.
\
,
\
\
:
\
i i
v
\
Xk
.
\
s
1
^
X
V .
1
^
*s^
*
.
»- ,
->w
"*
I
*
0.5 0.1 0.05 0.01 0.005
MILLIMETERS
SAND
COARSE
MEDIUM
FINE
l~*
-»»
0.0(
SILT OR CLAY
FIGURE C-l. Grain Size Distribution of Incoming Suspended Solids
to Primary Pond (Baseline, Pond No. 1)
-------
U.S. STANDARD SIEVE OPENING IN INCHES U.S. STANDARD SIEVE NUMBERS
6 43 2 'ft 1 3/i '/2 % 3 4 6 8 1O U 16 20 30 40 50 70100140 200
HYDROMETER
K'U
-
'
60
50
:
20
' :
:
:
1 1
1
i
1
1
\
--
4-
T
V
\
\
3
\
\
\
N
s
s
S
\
1 1
\
\
! I
' "
\
\
V
s
V
V
>
^
V
^
».
^
^5
-^i
».
-
-
-H
^
1
,0 100 50- 10 5 1 0.5 0.1 0.05 0.01 0.005 0.001
GRAIN SIZE MILLIMETERS
CO38LES
GRAVEl
COA»SE FINE
SANP
COARSE
MEDIUM
FINE
SIIT O« CtAY
"
_
'.
FIGURE C-2. Grain Size Distribution of Incoming Suspended Solids
to Primary Pond (Rainfall Event. Pond No. 1)
-------
U.S. STANDARD SIEVE OPENING IN
6 43 2 1ft 1 3/i ft H
INCHES U.S. STANDARD SIEVE NUMBERS
3 4 6 8 10 14 16 20 30 40 50 70 100 140 200
HYDROMETER
z
4.
igg
W
-
:
-:
5(
3O
20
10
0
5C
:
1
100
COBBLES
1
:
1
1 1
1
'
\
\
s,
50 10 5
GRAIN SIZE
GRAVEL
COARSE
FINE
1
\
\
\
>
^
\
.
\
\
\
\
\
\
\
\
\
\
0.5 0.1
MILLIMETERS
SAND
COARSE
MEDIUM
FINE
X,
^
^
~^^
^*^^>.
h
---,
---
** -.
1
0,05 0.01 0.005 0.001
SILT OR CLAY
FIGURE C-3.Measured Grain Size Distribution of Inflow Solids.
Pond No. 2 , Baseli ne
-------
100
U.S. STANDARD SIEVE OPENING IN INCHES U.S. STANDARD SIEVE NUMBERS
6 43 2 I'/J 1 5-i '/z % 3 4_ 6 8VO 1416 20 30 40 50 70 100 UO 200
TT
HYDROMETER
500
100 50
1 0.5
GRAIN SIZE MILUA/ETERS
0.1 0.05
001 0.005
0.001
COEStES
GRAVEL
COARSE
FINE
SAND
COAJtS1: MEDIUM
FINS
SIIT OR CLAY
FIGURE C-4. Grain Size Distribution Of Incoming
Suspended Solids To Primary Pond,
Pond No. 2, Storm Event
-------
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Figure C-5. Grain Size Distribution of Incoming Suspended Solids to the Sediment Basiny
Pond No. 3, Baseline and Storm Events
-------
U.S STANDARD SIEVE OPENING IN INCHES U.S. STANDARD SIEVE NUMBERS
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FIGURE C-6. Grain Size Distribution of Incoming Suspended
Solids to the Sediment Basin,
Pond No. 4, Baseline and Storm Events
-------
U.S. STANDARD SIEVE OPENING IN INCHES
6 43 2 1ft 1 % Mi tt 3 4
U.S. STANDARD SIEVE NUMBERS
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FIGUREC-7.
Grain Size Distribution of Incoming Suspended Solids to the Sediment
Basin, Pond No. 4, Baseline and Storm Events
-------
U.S. STANDARD SIEVE OPENING IN INCHES U.S. STANDARD SIEVE NUMBERS
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FIGURE c-8- Grain Size Distribution of Incoming
Suspended Solids to the Sediment Basin,
Pond No. 6, Baseline and Storm Events
-------
U.S. STANDARD SIEVE OPENING IN INCHES U.S. STANDARD SIEVE NUMBERS
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FIGURE C-9. Grain Size Distribution of Incoming Suspended Solids
During Baseline Conditions, Pond No. 7
-------
U.S. STANDARD SIEVE OPENING IN INCHES U.S. STANDARD SIEVE NUMBERS
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FIGURE C-10.Grain Size Distribution of Incoming Suspended Solids
During the Measured Storm Event, Pond No. 7
-------
U.S. STANDARD SIEVE OPENING IN INCHES U.S. STANDARD SIEVE NUMBERS
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FIGURE C-ll.Grain Size Distribution of Incoming Suspended Solids to the Sediment Basin,
Pond No. 8, Baseline and Storm Events
-------
U.S. STANDARD SIEVE OPENING IN INCHES
6 4 3 2 l'/2 1 3/4 '/2 % 3 4 6
U.S. STANDARD SIEVE NUMBERS
8 10 1416 20 30 40 50 70 100 140 200
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FIGURE C-1.2. Grain Size Distributions of the Incoming Suspended Solids During
the Baseline Conditions and the Rainfall Event, Pond No. 9
-------
TECHNICAL REPORT DATA
(Please read Initructiont on the reverse before completing}
1, FIEPORf NO,
EPA-600/2-76-117
3. RECIPIENT'S ACCESSION-NO.
4, TITLE AND SUBTITLE
EFFECTIVENESS OF SURFACE MINE SEDIMENTATION PONDS
S. REPORT DATE
August 1976 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
D. V1r Kathuna, Michael A. Nawrocki, and
Burton C. Becker
8. PERFORMING ORGANIZATION REPORT NO.
0, PEMPORMINfl ORGANIZATION NAME AND ADDRESS
Hittfflan Associates, Inc.
9190 Red Branch Road
Columbia, Maryland 21045
10. PROGRAM ELEMENT NO.
1BB040
11. CONTRACT/GRANT NO.
68-03-2139
12. SPONSORING AGENCY NAME AND ADOflMS
Industrial Environmental Research Laboratory
Office of Research and Development
U,S, Environmental Protection Agency
Cincinnati, Ohio 45268 __
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA-ORD
18. SUPPLEMENTARY NOT6A
16. ABSTRACT
An In-field evaluation of the effectiveness of sediment ponds in reducing suspended
solids 1n the runoff from surface mining activities was performed. Nine selected
sedimentation ponds 1n the three eastern coal-mining States of Pennsylvania,
West Virginia, and Kentucky were sampled under two different operating conditions
a baseline and a rainfall event. Their theoretical and actual efficiency of removal
of suspended solIds were computed and compared.
In general, poor construction and Inadequate maintenance of these ponds were found
to be the major problem areas. The ponds had generally higher removal efficiencies
during the baseline sampling period and much lower efficiencies during the storm
event. The theoretically predicted efficiency of the ponds was essentially the
same as the actual efficiency under baseline conditions. During the rainfall event,
there was generally little or no correlation between the theoretical and actual
efficiencies. The predicted efficiencies were found to be much higher than the
actual efficiencies during the rainfall event in most cases.
7.
KEY WORDS AND DOCUMENT ANALYSIS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Runoff
Sediments
Coal mines
Surface water runoff
Sediment control
Sediment ponds
West Virginia
Pennsylvania
Kentucky
13B
2C
81
8. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (TMsRcport)
UNCLASSIFIED
21. NO. OF PAGES
109
20. SECURITY CLASS (Thlipagt)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
101
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