United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-86/012 Aug. 1986
v°/EPA Project Summary
Guidance Manual on
Overtopping Control
Techniques for Hazardous
Waste Impoundments
Virginia Hodge, Nick DeSalvo, Shahid Mahmud,
Joshua Margolis, Mark Evans, and John Meade
The overall objective of this project
was to provide guidance for selecting
cost-effective interim management
methods to control overtopping of im-
poundments, pits, ponds, or lagoons at
uncontrolled hazardous waste sites until
final remedial actions could be initiated.
Hazardous waste impoundments are
subject to overtopping through the col-
lection of rainwater, run-on, or other
uncontrolled inflow. Lagoon overflows
are generally the result of insufficient
capacity due to either insufficient free-
board (high level of lagoon contents) or
structural problems that reduce the ef-
fective capacity. No matter what the
cause, lagoon overflows can pose sig-
nificant environmental and public health
risks through the contamination of soils,
ground water, and surface water, as
well as the potential to spread the con-
tamination into areas not currently im-
pacted by the lagoon. Thus, interim
measures may be necessary to control
lagoon overflows prior to identification
and selection of a final remedial
measure.
A manual has been prepared that
addresses both immediate control mea-
sures for emergencies and longer term
measures lasting several months to
several years. The technology and cost
guidance presented is general in nature
because of the variability of waste
lagoons and impoundments and the
unique conditions and considerations
that exist at each site. Where possible,
factors affecting application, technology
selection, and costs are identified, as
well as their likely impact on imple-
mentation and cost-effectiveness.
Design issues are briefly presented as
background to each option; however,
the manual is not intended to replace
the services of a qualified engineer in
designing site-specific systems.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
Research Laboratory, Cincinnati, OH, to
announce key findings of the research
project mat Is fully documented In a
separate report of the same title (see
Project Report ordering Information at
back).
Introduction
The Comprehensive Environmental
Response, Compensation, and Liability
Act of 1980 (CERCLA) established a
nationwide program for the cleanup of
uncontrolled hazardous waste sites.
Under this program, uncontrolled waste
sites are identified and ranked, and re-
moval or remedial actions are identified,
studied, and implemented to eliminate or
reduce contamination problems. Interim
measures must often be applied to pre-
vent or reduce further environmental
contamination or threats to public health
until final actions can be taken. The ob-
jective of this manual is to provide guid-
ance on selecting cost-effective interim
management methods to control over-
topping of impoundments, pits, ponds, or
lagoons at uncontrolled hazardous waste
sites.
Impoundments are subject to overtop-
ping through the collection of rainwater,
run-on, or other uncontrolled inflow.
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Lagoon overflows are generally the result
of insufficient capacity due to either in-
sufficient freeboard (high level of lagoon
contents) or structural problems that
reduce the effective capacity. No matter
what the cause, lagoon overflows can
pose significant environmental and public
health risks through the contamination
of soils, ground water, and surface water,
as well as the potential to spread the
contamination into areas not currently
impacted by the lagoon. Thus, interim
measures may be necessary to control
lagoon overflows prior to identification
and selection of a final response measure.
Typical response actions to temporarily
control an overflow problem have included
reconstruction of the impoundment berm
to increase the freeboard, removal of
liquid to lower the lagoon level, or both.
However, other response methods such
as run-on diversions and covers are avail-
able, and may often be more cost-
effective.
Surface impoundments are highly vari-
able in size, structure, design, and pur-
pose. Lagoons have been used for
treatment, storage, or disposal of liquid,
solid, and semi-solid wastes from in-
dustrial, mining, oil and gas, and agri-
cultural operations. They may be square,
rectangular, circular, or irregular in shape
and may be unlined causing seepage to
underlying soils or lined to prevent
seepage. Furthermore, lagoons may be
built aboveground or belowground via
natural or manmade depressions. Com-
monly, more than one surface impound-
ment may be found at a particular site
and these multiple impoundments may
be interconnected. These features, in
conjunction with site-specific character-
istics, can significantly affect the choice
of overtopping control measures.
Manual Content
The manual has been prepared to pro-
vide technical guidance to On-Scene
Coordinators (OSCs); Federal, state, and
local officials; private firms; and field
personnel. It presents guidance for se-
lecting impoundment overtopping controls
as a temporary solution pending final
response action. As such, it addresses
both immediate control measures for
emergencies and longer term measures
lasting several months to several years.
The technology and cost guidance pre-
sented are general in nature because of
the variability of waste lagoons and
impoundments and the unique conditions
and considerations that exist at each site.
Where possible, factors affecting applica-
tion, technology selection, and costs are
identified, as well as their likely impact
on implementation and cost-effective-
ness. Furthermore, while design issues
are briefly presented as background to
each option, this manual is not intended
to replace the services of a qualified
design engineer in designing site-specific
systems.
The manual presents the selection
process for overtopping control decision-
making and key factors affecting selection
decisions. Details are provided on
pumping and wastewater management
options; structural, floating, and air-
supported cover systems; and surface
water diversion and berm reconstruction
technologies.
Selection of Overtopping Control
Measures
The selection of overtopping control
measures proceeds in four steps:
1. Identification of the site problem; i.e.,
specifically why the lagoon overflows
and what site characteristics contri-
bute to the overflow. At the same
time, the site situation is assessed
regarding the need for immediate
emergency measures to be applied
prior to identifying further interim
control measures.
2. Preliminary selection of response op-
tions that may be applicable based on
the site problem. Thus, the first and
second steps of the selection process
are closely linked.
3. Evaluation of the site characteristics
affecting the applicability of a par-
ticular response. These characteristics
are defined by the response tech-
nologies identified in Step 2 and are
critical to the final evaluation and
selection of a response in Step 4.
4. Selection of a single response option
or combination of options that best
controls the overflow problem until
the final remedial action is undertaken.
This selection process is highly site-
specific and requires consideration of
site-related decision factors relative to
the applicable technologies and their
costs.
Characterization of Overtopping
Problem
Waste lagoon overtopping may be
caused by insufficient lagoon capacity to
accommodate liquid inflows to the lagoon
or reduced lagoon capacity due to struc-
tural damage to the upper portion of the
lagoon berm. Insufficient capacity may
be the result of insufficient freeboard in
the lagoon; precipitation; or run-on or
overflows/liquid feeds from a connecting
lagoon or other system. Structural damage
reducing the effective lagoon capacity
would include erosion, cracks, subsi-
dence, breach, or other penetration of
the lagoon berm in the area of the lagoon
level.
In general, the nature of the overtopping
problem is highly site-specific and must
be evaluated in terms of the causal and
contributing factors. For example, a crack
in the top of an impoundment berm
reduces the capacity of the lagoon if it
penetrates from the interior berm wall to
the exterior. Where the crack or break is
sufficiently deep, there may be a single
event of lagoon spillage. However, pre-
cipitation may quickly cause an overflow
to recur.
Thus, the first step in selecting appro-
priate overtopping control measures is to
identify the problem, including both the
cause and the contributing factors. Once
the reasons for the lagoon overflow have
been defined, they can be used to identify
potential actions to control the general
problem until a final site action is
developed.
If the lagoon is overflowing or overflow
is imminent, immediate control measures
are required. These control measures
consist of constructing a temporary hold-
ing pond to contain the overflow or using
a temporary pumping system to lower
the lagoon level. Once the urgency of the
problem has been reduced, appropriate
control measures for the interim period
prior to response should be identified and
implemented. These measures will
supplement or replace the stop-gap mea-
sures employed to control the immediate
problem by identifying and addressing
the contributing factors.
Identification of Applicable
Response Options
Each problem has a choice of several
technologies that may be applied. The
selection of a single response will depend
on site-specific factors. Where more than
one problem is involved, the response
options are expanded. Possible responses
for overflow caused by precipitation in-
clude pumping, covering the lagoon, or
raising the berm height. If both precipita-
tion and run-on are causing lagoon over-
flow, the response options expand to
include run-on diversions. Furthermore,
the selected response may involve a single
response option (e.g., pumping) or a
combination of response options (e.g.,
construct diversion, pump, and cover).
It should be noted that certain response
options require specific associated
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responses. Pumping lagoons to remove
liquid and increase freeboard requires
management of the waste liquid. Similar-
ly, raised covers such as air-supported
and arch-supported structures may re-
quire vapor or condensate control to pre-
vent the buildup of hazardous gases inside
the structures or release of liquids outside
the lagoon berm. The impact of these
requirements must be considered in the
selection process.
Evaluation and Selection of
Overtopping Controls
A specific control measure is selected
based on technology and site-related
decision factors. This process involves a
simple cost-effectiveness evaluation to
decide among competing control re-
sponses. The manual presents summary
tables for the potentially applicable tech-
nologies (e.g., pumping, wastewater
management, lagoon cover systems, berm
reconstruction, and surface water diver-
sion systems) which include specific,
decision-related criteria regarding tech-
nology applicability, limitations, and costs.
The technology evaluation shouM
screen the options based on applicability
to the site problem (defined through the
site criteria) as well as the potential to
reuse any permanent systems or materials
or the need to demolish structures such
as covers or diversion structures for final
site action. The reuse of a system will
impact its cost-effectiveness since the
capital investment is spread over several
applications. Alternatively, the removal
of a cover and its anchoring system or
the demolition of diversion structures may
impact the costs of the final remedial
action.
Other criteria included in the technology
evaluation are:
• Anticipated length of time before
remedial measures are implemented
- Short time intervals (less that 3
months) would support a pumping
system or diversion structures.
- Long time intervals (3 to 5 years)
would support cover systems.
• Urgency of problem
- Where lagoon overflow is immi-
nent, pumping or construction of a
temporary holding pond would be
indicated.
- Where the situation is less urgent,
pumping may be used as an initial
measure prior to another control
response or pumping alone may
be implemented as a cont-—'
measure.
• Time to implement control measures
- Cover systems will require more
time to implement than the use of
pumps or site reconstruction.
• Size of lagoon
- Structural covers cannot be used
where the smallest dimension ex-
ceeds the greatest width available.
- Multiple pumping stations or berm
reconstruction may be more cost-
effective than a floating cover for
large lagoons.
- Covers may be more applicable to
small and moderate sized lagoons
where frequent pumping may be
necessary.
• Volume of liquid to be removed
- Areas with heavy or frequent rain-
fall would favor a permanent
pumping station, berm reconstruc-
tion, diversion structures, a cover,
or a combination of these options.
- Areas with isolated precipitation
events would favor temporary
pumping stations.
As part of the cost-effective selection
effort, general estimates can be made for
rapid comparisons of responses and deci-
sionmaking. One method would be to
average the costs over the length of time
that the control measure is in effect. In
such cases, the costs should include gross
estimates of maintenance, inspection, and
repair activities that would be likely within
the time period. Detailed cost guidance is
available through EPA procedural
manuals.
Both the technology and cost compari-
sons should consider single-response
options and multiple-response options. In
some instances, a technologically complex
solution may be more cost-effective than
a technologically simpler solution. For
example, under certain conditions it may
be more cost-effective to install a floating
cover on a lagoon (including an initial
pumpdown and some berm strengthen-
ing) to control overflow resulting from
precipitation than to pump down the
lagoon level several times a year while
the final response action is under study.
Of course, this decision depends on the
expected length of time before final mea-
sures are implemented, the technology
costs, and on-site features such as
precipitation patterns.
Of special importance is the evaluation
of pumping options. Either a temporary
pumping system can be brought in when
needed or a permanent pumping system
can be constructed. The decision would
depend on the number of times pumping
would be necessary and the relationship
of pumping to other options. However,
where frequent pumpdowns are neces-
sary (e.g., due to heavy annual rainfall), a
permanent pumping station should be
selected unless a more cost-effective
control option is available. Lagoon size,
volume of liquid to be pumped, frequency
of pumping, and wastewater manage-
ment requirements would all affect the
selection of this option.
Wastewater management options also
involve a complex evaluation. Wastewater
management is always necessary in con-
junction with pumping. Management
options involve a number of on-site and
off-site methods to store, transport, treat,
or dispose of pumped liquids. Liquids
could be pumped to a storage tank on-
site or a tank truck may be used to
transport wastewater to an off-site
Publicly Owned Treatment Works (POTW)
or commercially operated treatment fa-
cility. Mobile treatment units may be
brought on-site to pretreat wastewater in
order to make it acceptable for a POTW.
Wastewater can also be discharged
directly from the site to a surface water
body if it meets water quality standards.
Finally, the liquid may be discharged
directly to a POTW provided that sewer
connections are available and the com-
position of the liquid is acceptable for the
POTW. Key decision factors will involve
the type of pumping system selected
(temporary or permanent), wastewater
quantities, wastewater characteristics,
available facilities, etc.
The manual discusses factors affecting
selection, installation, and costs of pump-
ing systems as well as various waste-
water management options.
Lagoon Cover Systems
Waste lagoons may be covered to pre-
vent precipitation accumulation that may
cause the impoundment to overflow. A
variety of commercially available cover
systems have been used in similar
applications.
Frame-Supported Tension
Membrane Structures
Frame-supported tension membrane
structures provide an efficient and stable
building with a free span coverage of a
site. These structures consist of fabric
panels tensioned between specially de-
signed arches. Such structures are avail-
able commercially from a number of
manufacturers and have been used in
exhibitions and fairs, and in aviation,
manufacturing, recreation, military, and
mining applications.
Frame-supported tension membrane
structures are available at total costs
ranging from $8/ft2 to $19/ft2. There are
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limited operational costs unless special
control systems are required. They cannot
be used if the smallest lagoon dimension
is greater than 140 feet or if the soil
conditions are inadequate to support the
load of the structure and/or the con-
struction equipment. The site must also
be easily accessible in order to erect the
structure. The frame is susceptible to
attack by strong acids and may require
treatment with special coatings in an
acidic environment.
In general, this option is not feasible
for short-term usage at a single site. This
type of structure is reusable and can be
decontaminated; accordingly, its applica-
tion may be cost-effective if reuse at
other sites is practicable.
Prefabricated Steel Frame
Buildings
Prefabricated steel frame buildings
such as those used for warehousing may
also be used to cover lagoons. There are
many manufacturers of steel frame build-
ings and various types of structures. The
rigid frame system is one of the more
common and most practical to use over
moderately sized lagoons.
The total costs of a prefabricated steel
frame structure to cover a lagoon varies
from $14/ft2 to $23/ft2 depending on the
site, design of the structure, coating re-
quired, and manufacturer. (In most cases,
a special coating may be required to
increase the longevity of the structure).
The structure can be decontaminated,
dismantled, and reused. This structure
cannot be used if the smallest lagoon
dimension is greater than 200 feet. As
with other structures, it is necessary to
determine the stability of the soil to with-
stand the loading of the building and
construction equipment.
In general, the high costs of a pre-
fabricated steel frame structure make
this control measure infeasible unless it
can be reused at other sites.
Air-Supported Structures
Air-supported structures have been
used for warehouses and construction
shelters, and for covering recreational
and sewage treatment facilities. This type
of structure is a totally free-span structure
that maintains stability in space and
resistance to loads through a pressure
differential between the interior and ex-
terior of the structure. This method of
support leaves the interior free of poles,
pillars, or other support devices that would
be impractical to erect over a lagoon.
Air-supported structures can cover
lagoons of many configurations and sizes.
Their total costs range from $3.25/ft2 to
$10/ft2 and are thus highly competitive
with other technologies used for over-
topping control. The coated fabric used in
the structure can be selected to be
compatible with the contents of the
lagoon. Heating, ventilation, condensate,
and air pollution controls can also be
designed to meet specific lagoon and site
requirements. These auxiliary systems
impose additional costs to the cover sys-
tem; however, the cover can be decon-
taminated and is reusable.
There are several limiting factors for
the application of air-supported struc-
tures. If the smallest lagoon dimension is
greater than 550 feet, this system cannot
be used. The soil conditions may preclude
certain anchoring systems or require the
construction of concrete anchoring bases,
which will increase the system cost.
Floating Cover Systems
A floating cover consists of a lining
placed in one piece over an impoundment
with proper anchoring at the edges and
floats to prevent the lining from sub-
merging. According to industry officials,
approximately 80 to 85 percent of all
floating covers have been constructed
over potable water reservoirs. The re-
maining 15 to 20 percent have been used
at biodegradation facilities, slaughter-
houses, chemical treatment ponds, and
toxic waste lagoor
Floating covers
any other type of ci
in total cost be
$6.50/ft2. The Mr
vary according t<
lagoon; Hypalon
type of liner used.
is limited if there i
of debris on the s
submerged in the
ture the cover. Ar
floating cover is t
be reusable due to
to lagoon content!
Surface Water
Bern Improvei
Lagoons may 0'
water run-on or 1
manual discusse
maintain or increa
of the lagoon by:
• Diversion of
face run-on
ditches, diver:
• Prevention of
through the
struction of b
These control opti
5.
re less expensive than
vering system, ranging
ween $2.50/ft2 and
ng material used can
the contents of the
s the most common
Use of a floating cover
s a substantial amount
rface of the lagoon or
agoon that may punc-
other limitation of the
lat the fabric may not
swelling from exposure
Diversion and
nents
erflow due to surface
erm degradation. The
options that either
se the holding capacity
quid inflow from sur-
through the use of
ions, dikes, and berms.
waste material outflow
instruction or recon-
srms.
ns are unique relative
to other overtopping controls discussed
because they are directed at preventing
overtopping through measures applied,
external to the impoundment (i.e., on the
walls or surrounding areas).
Surface Water Controls
Surface water controls are improve-
ments external to the impoundment and
its immediate area that prevent liquids
from entering the impoundment or erod-
ing impoundment walls. When designed,
constructed, and maintained correctly,
surface water controls can extend the
useful life of the impoundment by either
preventing run-on, which fills available
lagoon capacity, or reducing wall de-
gradation, which lessens available lagoon
capacity. Surface water control tech-
niques include:
• Ditches, diversions, and waterways:
small drainage ways that intercept
and divert run-on away from an
impoundment.
• Diversion and interceptor berms and
dikes: structures that intercept and
divert run-on away from an
impoundment.
• Terraces and benches: wide drainage
ways that slow down run-on and
divert it to ditches and diversions.
• Levees and floodwalls: embank-
ments used to prevent contact of
floodwaters and tides with the
impoundment.
These options are discussed in detail in
the manual. Also included are unit costs
for construction of ditches, diversions,
and waterways, as well as costs for other
diversion structures. In general, costs of
surface water controls are very dependent
on such items as:
• Extensiveness and terrain of area
requiring control.
• Number and size of structures
required.
• Amount and type of non-local
materials required (e.g., cement,
asphalt, synthetic liners, etc.).
• Accessibility of the site (especially
for heavy machinery).
• Severity of weather patterns.
• Design life of control.
Impoundment Wall Construction
and Repair
When designed, constructed, and main-
tained correctly, improvements to surface
impoundment walls can extend the useful
life of the impoundment by either main-
taining or increasing its capacity until
final response actions are implemented.
This can be accomplished by either re-
pairing existing defective walls and/or
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increasing the height of berms to increase
capacity. These options, along with as-
sociated costs, are discussed in detail in
the manual. Factors influencing the costs
are similar to those identified for surface
water controls.
Conclusion
Presently, the most common method of
preventing overtopping of abandoned
waste lagoons is pumpdown/treatment
of the upper two feet of the waste liquid.
Since this costs between $0.10/gal and
$.40/gal, this method can be expensive,
especially if it must be performed several
times prior to final cleanup of a site.
Alternative methodologies are available;
however, the final costs will depend on
many site-specific factors. These factors,
along with details on alternative tech-
nologies such as: pumping and waste-
water management, various lagoon cover
systems, surface water controls, and im-
poundment wall construction and repair,
are presented in the manual. The manual
will enable Federal, state, and local of-
ficials to select a technology or series of
technologies for short-term control of
impoundments that are subject to over-
topping through collection of rainwater,
run-on, or other uncontrolled inflow.
Virginia Hodge. Nick DeSalvo. Shahid Mahmud. Joshua Margolis, Mark Evans.
and John Meade are with JRB Associates, McLean. VA 22102.
Anthony N. Tafuri is the EPA Project Officer (see below).
The complete report, entitled "Guidance Manual on Overtopping Control
Techniques for Hazardous Waste Impoundments," (Order No. PB 86-154
168/AS; Cost: $16.95. subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, v'A 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Releases Control Branch
Hazardous Waste Engineering Research Laboratory—Cincinnati
U.S. Environmental Protection Agency
Edison, NJ 08837
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Environmental Protection
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