\ I /
United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-84-173 Jan. 1985
/T^
&ER& Project Summary
Assessment of Hazardous
Waste Surface Impoundment
Technology: Case Studies and
Perspectives of Experts
Masood Ghassemi, Michael Haro, and Linda Fargo
Nine hazardous waste surface impound-
ments (Si's) were assessed in a case
study to compare actual and projected
performances. The goal was to produce
data that can significantly improve the
design, construction, and operation of
these facilities. The nine facilities
represent a range of industries, waste
types and volumes, ages, environmental
settings, linear types and designs, and
systems for leak detection and ground-
water monitoring.
In addition to the case studies, nine
interviews were held with technical
experts in four consulting engineering
firms, one waste management company,
one liner fabricator and installer, and
regulatory agencies in three states.
Recommendations for research and
development are presented based on
the case studies and the professional
opinions collected.
The poor performances of several Si's
were attributed to factors such as lack
of good project planning during design
and construction, lack of quality assurance
and control, deviations from liner
specifications, inadequate waste-liner
compatibility studies, and lack of
proper site investigations before design
and construction. The successful per-
formances of Si's at two facilities are
attributable to the use of a very
impermeable clay liner after extensive
compatibility studies; use of competent
contractors; close scrutiny of all phases
of design, construction, and inspection
by the owner/operator; excellent
quality assurance and control recordkeep-
ing; and good communication among
all parties involved.
Technical experts consider the follow-
ing factors essential to good site
performance: Siting in good geologic
formation, continuous geotechnical
support throughout all project phases,
supervised construction to ensure
adherence to specifications, compaction
of clay liner wet of optimum to eliminate
air spaces, consideration of liner-waste
compatibility, rigorous quality assurance
and control in designing and installing
liners, and provision and maintenance
of protective covers for liners.
Research and development areas
should include documenting and dissem-
inating design and performance data
from operating sites, evaluating waste-
liner compatibility under actual condi-
tions, developing reliable techniques
for early detection of site failure,
establishing criteria for groundwater
monitoring systems, and studying the
causes and cures for plugged leachate
collection systems in landfills.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
Research Laboratory, Cincinnati. OH,
to announce key findings of the re-
search project that is fully documented
in a separate report of the same title (see
Project Report ordering information at
back).
Introduction
A research project was undertaken to
investigate the use of surface impound-
ments (Si's) for hazardous waste manage-
ment. The primary goals were to develop
criteria for improved SI design and
operation and to provide technical
support to the U.S. Environmental
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Protection Agency (EPA) in developing SI
regulations as required by the Resource
Conservation and Recovery Act (RCRA).
Currently, the principal source of EPA
information on hazardous waste Si's is
the surface impoundment assessment
(SIA) data base developed by the Office of
Drinking Water. Though the data base
contains some background survey infor-
mation on the numbers, types, and uses
of wastes handled by municipal, industrial,
and agricultural Si's in the United States,
it contains little or no information on their
engineering design and actual perfor-
mance. Comparing projected and actual
performances at operating Si's and
identifying reasons for observed differences
are essential for designing better Si's and
for formulating appropriate corrective
actions at existing sites.
The present study therefore develops a
data base on hazardous waste SI design
and operating practices and compares
actual and projected performances for a
selected number of facilities. The study
identifies gaps in the existing data base
and in areas that most warrant research
and development.
Two complementary approaches are
being used to define the state of the art for
hazardous waste SI technology: Case
studies for a selected number of Si's and
interviews with technical experts.
Case Studies
The Si's for the case studies were
selected largely from those operating in
the southwestern United States, primarily
California and Texas. Twenty-eight
facilities were selected as potential
candidates for case studies based on
examinations of state data files, state SIA
surveys, and background data from other
recent hazardous waste management
projects. These sites were further screened
by discussions with state regulatory
agencies and facility owners/operators,
and by considering the following factors:
Amount of data available
Representation of a range of SI
service types
Presence and type of liner used
Types of hazardous waste handled
Design and construction practices
Facility performance
Absence of litigation
Anticipated level of cooperation
from owner/operator
The preliminary screening eliminated
eight sites from further consideration
because of multiple potential sources of
pollution, ongoing litigation, and lack of
operating data at new sites. Further
screening eliminated 11 additional sites,
and detailed case study and assessment
summary reports were prepared for the
remaining nine sites.
The nine cases were evaluated in some
detail, and case study and assessment
summary reports were prepared. Table 1
contains general information on these
sites, including the types and qualities of
wastes handled. As noted in the table,
these Si's serve a variety of industries,
handle different waste types and volumes,
are used for disposal or treatment
purposes, and range in age from less than
2 to more than 30 years. The case studies
cover a range of liner types and designs
single liners, double liners, clay liners,
flexible membrane liners (FML's), and
clay liners used with FML's. A variety of
leak detection systems are also examined.
The extent of groundwater monitoring
also varies from the use of no observation
wells to the use of multiple wells at
strategic locations.
The case study report prepared for each
site essentially compiles all available
relevant data for that site and is the basis
for performance assessment. For each
facility, the draft case study report was
submitted to the site owners/operators
for review to assure accuracy and
completeness and to provide them with
an opportunity to expand or supply
additional information or clarifications. In
transmitting the draft reports, the owners/
operators were requested to provide any
quantitative engineering data (e.g., on the
original site design, actual construction,
liner inspection, and maintenance programs)
that might support some of the qualitative
statements and assertions. Comments
received from the reviewers were incor-
porated in the case study reports as
appropriate.
The identity of the case study sites was
of little consequence to the project
objective. Thus to promote the cooperation
of the owners/operators, all sites were
kept anonymous and designated only by
letter or number.
Interviews and Experts
This phase of the study sought the
perspective of experts on factors affecti ng
SI performance and deviation from
design predictions. Information was
gathered from those most intimately
involved in the design, construction,
operation, and regulation of hazardous
waste Si's. Though a large number of
individuals and organizations were
contacted, only nine granted interviews.
Except for one interview conducted with a
written questionnaire, discussions were
face to face in a very informal atmosphere.
In most cases, more than one individual
represented the participating organization.
Discussions generally covered some or
all of the following topics:
Surface impoundment versus landfill
Site selection
Geotechnical evaluation
Design criteria and considerations
Quality assurance and quality control
Liner material selection and liner-
waste compatibility problems
Site preparation and liner installation
Research and development needs
Regulatory considerations
A summary report was prepared after the
interview and forwarded to the participants
for review and comment. Suggested
changes, which were generally minor,
were aH incorporated in the final report.
Results
Detailed evaluation of the data compiled
for the nine cases studied has resulted in
the following assessments.
Case Study No. 1
The two FML-lined hazardous waste
Si's at this site were designed and
constructed by the owner in 1972 and
1979. Since no regulatory requirements
governed the design or construction of
such facilities at the time, nogeotechnical
or hydrogeological studies, environmental
impact analysis, or laboratory or field
investigations preceded the actual design
and construction. Onsite availability of
land was the primary consideration for SI
site selection. Apparently, no rigorous
quality assurance and control (QA/QC)
program was conducted, nor was there
any inspection of the completed Si's by
professionals trained in FML design and
installation.
The Si's at this site have failed to
provide satisfactory service. Limited
water quality data from monitoring and
production wells indicate contamination
of both the upper and the lower ground-
water aquifers, as evidenced by increases
in the total dissolved solids, sulfate, and
nitrate concentrations. Because cracks
appeared along the exposed sides of the
liner in one of the ponds, the liner was
replaced once. Possibly the liners in both
ponds are now leaking. Because of the
relatively high permeability of the geologi-
cal strata underlying the plant (0.44 x 10~2
to 1.4 x 10~2 cm/sec) and the strong
acidic nature of the heavy metal-bearing
waste in the Si's, any liner failure could
result in a substantial underground
waste release. Hence the site presents
major potential for groundwater contam-
ination.
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Table
Case
Study
No.
1
1. Case Study Facilities
Type of Facility
Electrolytic metal
refining plant
- General Features and
Type of SI
(No. and Function)
Small disposal pond
Waste Characteristics
Year
Placed in SI Size
Service (Acres}
1972
0.4
Waste Type
Acidic process liquor and
sludge waste (pH <2) high in
Waste
Quantity
A total of 843.750
gal in 1982
Disposal pond
heavy metal content
1979 1.1 Acidic process liquor and sludge
waste (pH <2) high in heavy metal
content
Pesticide formulation
and distribution plant
Pesticide washdown
evaporation disposal
pond
Pesticide rinsewater
evaporation disposal
pond
1979 <0.1
1982 <0.1
Pesticide rinsewater
Pesticide rinsewater
Batch operation
(400 gal/day
maximum)
Batch operation
(400 gal/day
maximum)
Commercial hazardous Site A: 8 impoundments
waste disposal used for settling.
facility storage, and sludge
disposal
1951 15 Oily water and brines, alkaline A total of
and acid wastes, heavy metals 53 million gal
paint sludge, tank bottom in 1982
sediments, cyanide, pesticides,
and other chemical wastes
Agricultural fertilizer
manufacturing plant
11 settling ponds used
to remove gypsum
One evaporation pond
(treatment)
One cooling pond
(treatment)
1965 14 Production water for ammonium 20,000 gal/day
phosphate/phosphoric acid plant
with pH <2 and high radionuclides
content
1976 8 Wastewaters from plant boilers, 130,000 gal/day
water treaters, and nitric and
sulfuric acid plants (pH<2. high
in radionuclides)
1976 38 Same as gypsum Sf's 10,000 gal/day
Mineral ore mining/
manufacturing plant
5 low-head solar ponds
(treatment and storage)
High-head evaporation
pond (treatment and
storage)
High-head evaporation
pond (treatment and
storage)
Evaporation pond
(treatment and storage)
high arsenic and boron
content
1972 90 Mineral liquor tailings with
high arsenic and boron content
1975 80 Mineral liquor tailings with
high arsenic and boron content
1976 100 Mineral liquor tailings with
high arsenic and boron content
1980 120 Acid plant wastewater with
high arsenic and boron
content
A total of 50 million
gal/month to Ponds
A-E, 4, and 5
12 million gal/
month
Commercial hazardous Evaporation pond 1980 5
waste disposal facility (disposal)
Disposal pond (currently 1980 5
used for land treatment)
Disposal pond (currently) 1981 5
Geothermal muds and brines,
wastewater treatment sludge,
tank bottom sediments, cooling
tower blowdown sludge and oil
drilling muds
Geothermal muds and brines,
wastewater treatment sludge.
tank bottom sediments, cooling
tower blowdown sludge, and oil
drilling muds
Geothermal muds and brines.
wastewater treatment sludge,
tank bottom sediments, cooling
tower blowdown sludge and oil
drilling muds
9.85 million gal
in 1982
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Agricultural
fertilizer manu-
facturing plant
Cooling pond (treatment)
Initial gypsum pond
(disposal)
Expansion gypsum pond
(disposal)
1974 100 Process water from phosphoric 40.000 gal/min
acid plant with pH <2 and high (maximum)
fluoride content
1974 150 Gypsum slurry with pH <2 and No data available
fluoride and phosphorus content
1980 200 Gypsum slurry with pH< 2 and No data available
fluoride and phosphorus content
Chemical production
plant
2 equalization/'retention
basins (treatment)
1976 3.5 Wastes high in organic nitrogen
content and varying pH. resulting
from synthetic fiber production
3,000 gal/min
Uranium mining/
milling
Tailings pond
(disposal)
1980 64 Acidic tailings slurry containing
kerosene and radium 226
No data available
Case Study No. 2
The very satisfactory operation at this
site indicates that with proper site and
wastewater characteristics, designing
and constructing small ponds to provide
satisfactory performance can be simple
tasks.
Two very small (48 x 28 x 5 ft and 30 x
20 x 3 ft), relatively new, onsite impound-
ments serve this pesticide formulation
and packaging plant, which generates
intermittent discharges of wash-down
and rinse water. The waste volume is very
small, seldom exceeding 400 gal per
discharge two to three times per month.
Groundwater in the area is at 215 ft. The
wash-down pond is lined with two layers
of polyvinyl chloride (PVC) sheeting as the
primary liner on both the bottom and the
side slopes. A 30-mil PVC liner is used as
the secondary liner on the bottom only.
The primary and secondary liners are
separated by 1 ft of gravel. The rinse-
water pond is lined with 20-mil chlorinated
polyethylene (CPE) underlain with 1 ft of
sand and a 10-mil PVC liner, with both
liners extending along the bottom and
side slopes. The leak detection system for
each pond is merely a single, perforated
PVC pipe (a 3-in. pipe for the wash-down
pond and 1-in. pipe for the rinse-water
ponds) extending halfway across the
pond bottom and connecting to an
observation well. A 1/4-in. fiber glass
cover was recently placed over the
primary liner in each pond for better
protection against liner deterioration and
damage during pond cleaning. A 20,000-
gal storage and equalization tank was
also recently installed to control liquid
level in the wash-down tank.
During the 4-year operation of the
wash-down pond, no liquid was observed
in the observation well. Since the rinse-
water pond was placed in operation only
in late 1982, similar results from the leak
detection have not yet been reported.
Case Study No. 3
The two impoundments located in
separate areas of this facility exemplify
the performance differences between
poorly planned and designed ponds and
those that are well planned. Problems
resulting from poor planning cannot
always be fully and permanently corrected
through piecemeal remedies. This fact is
illustrated at Site A, where nothing
indicates that detailed site selection
investigations or pond design took place.
When the facility was investigated in
1971, wastes were seeping through pond
levees that had been built on top of old
waste fill. Work was performed to correct
the problem at that time, but seepage was
reported again during investigations in
1978. Specific levee permeability and
thickness requirements were then imposed,
and the levees were rebuilt to conform to
these requirements (5 ft of clay with 108
cm/sec permeability or the equivalent).
But leachate was discovered again in
1980, indicating that even the improved
dikes were not able to prevent seepage.
By contrast, Site B was developed in
1971 with some effort to design ponds
that would prevent waste migration. The
site was investigated and soil compaction
and other design criteria were specified
before construction. When the site was
investigated in 1978, no seepage was
reported, even though the levees did not
all conform to the new permeability
requirements and had to be modified.
Site A may not have been explicitly
sited and designed to prevent waste
seepage as Site B was. This possibility
appears to have been a significant factor
in the performance of the facility with
respect to seepage. Building Site A pond
levees on a garbage foundation undoubted-
ly contributed to the seepage problem,
and the displacement fill method of
improving the dikes apparently was
unable to solve the problem. Trench key
work apparently did not provide a
complete solution either, unless the
leachate originated (as the facility owners
contended) from an adjacent commercial
landfill.
Case Study No. 4
The operating experience at this site
illustrates (1) how the materials in the
waste can provide an adequate barrier
against further waste seepage under
certain circumstances, and (2) how liner
failure and poor performance can result
from deviations in desired liner specifica-
tions, reliance on inadequate liner-waste
compatibility tests, insufficient attention
to geotechnical factors, and poor design
and operating practices.
The major surface impoundment systems
at this fertilizer manufacturing facility are
eleven 14-acre gypsum ponds, an 8-acre
evaporation pond, and a 38-acre cooling
pond. The gypsum ponds are unlined
sedimentation ponds that have been used
to recover gypsum for nearly 20 years.
The natural buildup and solidification of
gypsum in those ponds have rendered
them impervious. This fact has been
verified by actual examination and
permeability testing of the core specimens
from the bottom, which have indicated
the presence of a very hard material with
low permeability.
The FML-lined evaporation and cooling
ponds have failed in the past and are
currently leaking. The liner specifications,
which were written by the facility owner,
called for a material that would not
deteriorate when exposed to a waste with
the following characteristics: pH of 2,
maximum temperature of 110°F, 0.5%
sulfuric acid, 1.63% phosphoric acid,
0.05% chlorides, 0.5% fluorides, and
1.0% organics. Though the available data
indicate that the liner met the alkali and
acid (pH 3.0) resistance tests, the
material may not have been tested with a
4
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waste simulating the above characteristics.
The actual liner manufacturer's warranty
also provides for an acid resistance of 1 %
weight change versus an original specifica-
tion of 0.3% (both at pH 3.0) and limits the
definition of organics to only five specific
compounds, the total concentration of
which is not to exceed 1 %. Geotechnical
and soil investigations had indicated that
the native clay had a high content of
calcium carbonate. This soil characteristic
(which would lead to gas formation
underneath the liner in the event of acidic
waste leakage through the liner) was also
not addressed in the site and liner design.
Liner bubbles have been observed in
the FML-lined ponds. Inspections during
repairs suggested seaming failure as the
main initial cause of the liner leak.
Seepage of the acidic waste into the
underlying carbonate-bearing clay resulted
in the production of large volumes of gas.
Since no provisions had been made for
venting, gas accumulation helped spread
the seams and further aggravated the
leaking. An overload discharge pipe that
diverted wastewater from the gypsum
ponds to the evaporation pond was also
an apparent contributor to the seam
failure problem in the splash area. This
problem was eliminated by installing a
splash pad after the liner area was re-
paired.
Case Study No. 5
This facility contains eight clay-lined
impoundments and demonstrates what
can be achieved when the impoundments
are well designed, constructed, and
operated. The major reasons for the
highly successful performance of these
clay-lined ponds include: (1) the use of a
very impermeable clay (available onsite)
as the liner material, (2) the use of
competent design, construction, and
inspection contractors, (3) a conscientious
owner/operator that closely scrutinized
all phases of impoundment design,
construction, and operation (from site
selection to QA inspection), (4) extensive
waste-liner permeability studies, (5)
excellent QA/QC and recordkeeping
during all phases of the project, and (6)
good communication (input and feedback)
between two different state regulatory
agencies and all parties involved in the
establishment of the ponds.
The performance of the impoundments
is documented by many years of inspection
reports and observation of the leak
detection systems located beneath each
pond. These leak detection systems were
field-tested by state inspectors during
construction. The good performance of
the impoundment is not surprising, since
the clay used to line these ponds has held
the borate deposits mined at this facility
for centuries.
Case Study No. 6
The operating experience at this site
illustrates how poor impoundment design
and inadequate construction, inspection,
and recordkeeping can lead to leakage
and poor performance. Wastewaters
began seeping laterally out of one
impoundment because (1) sand lenses
within the natural clay were not identified
and removed as specified in the design,
and (2) at least one of the embankments
was not adequately keyed into unweathered
clay to prevent lateral waste migration.
This commercial hazardous waste
disposal facility contains three 5-acre Si's
lined with in-situ clay (on the bottom) and
recompacted clay embankments. Pond 8
received geothermal and petroleum
industry sludges and wastewaters, and
the other two ponds are currently used for
land treatment of organic sludges.
A soils investigation conducted before
impoundment design indicated the
presence of sand and silt lenses within
the natural clay beneath the site. The
design specifications called for (1) at least
2 ft of natural clay (with a permeability of
10"8 cm/sec) beneath the ponds i n which
no sand or silt lenses were discovered
during pond excavation and construction,
and (2) subsequent placement of recom-
pacted clay. The wastes began to migrate
laterally along a sand lens underneath
the embankment and surfaced outside
the impoundment because: (1) not all
sand silt lenses were detected by boring
tests or during excavation and construction,
and (2) at least one embankment of Pond
8 was not keyed into the natural unwea-
thered clay as specified (and this noncom-
pliance with specifications was apparently
not discovered and documented during
QC inspection).
Though no seepage has been detected
outside the other ponds, the other
embankments at the site may not have
been keyed into unweathered clay. The
inspection and engineering certification
reports for the site are very poor and
unclear on this point.
Case Study No. 7
This facility shows how a combination
of good site hydrogeology, proper design
and construction, and adequate contingen-
cy planning can ensure satisfactory
performance for surface impoundments
located on in situ clay and diked with
compacted clay. The site contains gypsum
slury and process wastewaters from a
large fertilizer manufacturing operation.
Two important site characteristics that
contribute to the success of the impound-
ments here are the very low permeability
of the 120-ft-deep, in situ clay layer (10
cm/sec) and the high groundwater table,
which provides a reverse gradient and
hence an added safety factor against
waste exfiltration. Monitoring of the deep
groundwater aquifer and more than 9
years of monitoring data from a network
of shallow wells have indicated no
impacts on groundwater quality and no
seepage through sand/silt lenses.
The good performance of the clay-lined
ponds can be attributed to the following
factors:
Detailed geotechnical investigation
of the site, including extensive
laboratory testing of boring samples
from subsurface soil.
Borrow pit excavation within the
pond areas that is limited to 5 ft
below ground surface and 50 ft from
dike bases. The first limitation
reduces the possibility of exposing
sand/silt lenses, and the second
restriction decreases the chance of
continuity for any undetected sand/
silt lenses.
Removal of all exposed sand/silt
lenses and subsequent compaction
of a 3-ft layer of clay over these
areas.
Clay compaction that is done in thin
lifts to eliminate voids and meet
permeability requirements.
Comprehensive inspection and
testing of pond and dike construction.
Installation of a network of shallow
wells to monitor possible lateral
seepage through sand/silt lenses.
During a recent failure of the 100-acre
gypsum stack (in the gypsum pond),
disaster was averted because of
adequate contingency planning and a
prepared work crew. When signs of a
possible failure were first noticed, ditches
that surround the pond were dammed off.
Thus when the failure actually occurred,
the nearly 6 million gal of acidic water
was totally contained. The failure was
attributed to long-term consolidation
settlement of the underlying soft clay,
which caused tension cracking in the
overburden gypsum stack and hence
failure. The magnitude of the time-
dependent settlement of clay and the
resistance of the gypsum stack to tension
cracking had not been correctly estimated
in the original design.
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Case Study No. 8
These two large ethylene-propylene
diene monomer (EPDM)-lined equalization
and retention surface impoundments
failed because of excessive swelling and
permeation of the liner material and
separation of the seams. The waste-liner
incompatibility was not predicted by the
limited tests preceding liner selection.
The selection of EPDM appears to have
been based on its low cost, ease of
installation, and ready availability. The
seam separation problem resulted from
deterioration of the glue used and seam
laps smaller than those required by the
design. Substitution of the clay tiles for
perforated PVC pipes in the seepage
drainage system caused extensive
plugging of the system and loss of
capacity. Other factors in the facility's
failure were inadequate communication
between owner and contractors,
inadequate inspection and acceptance
procedures, and a less-than-competent
project engineer.
The Si's at this facility serve a chemical
production plant in an industrial coastal
community. Industrial activity has been
continuous in the area since about 1900,
with changing plant ownership,
production, and waste disposal practices.
Because extensive onsite disposal has
raised the surface elevation 20 to 30 ft
above the original, it is nearly impossible
to assess SI performance. Monitoring
wells indicate the presence of a range of
chemicals, some known to be absent from
the currently impounded wastes.
Case Study No. 9
This case study underscores the need
for nonerosive shoreline protection at the
waterline for FML's in large surface
impoundments that may experience
strong winds and severe winter
conditions. Though construction,
compaction, and earthwork were
thoroughly documented and inspected at
this site, liner inspection was limited and
undocumented.
This 62-acre uranium tailings pond is
lined with 30-mil PVC on the bottom and
30-mil polyester-reinforced Hypalon* on
the sides. No form of protective cover was
provided for the liner, presumably
because of the supposed difficulty of
maintaining such cover in the face of
strong winds and surface waves. Four
documented failures of the liner have
occurred in less than 3 years. The first
failure occurred 4 months after
"Mention of trade names or commercial products
does not constitute endorsement or recommenda-
tion for use.
installation and involved a 300-ft
separation of the liner seam caused by
deviation from installation specifications.
Other failures include numerous
punctures and tears resulting from
carelessness during installation, a
ruptured discharge line, floating debris
that was not removed after a winter
storm, and wave action against the liner
ridge. The leak detection underdrain
system failed to detect substantial leaks
that occurred at points not directly over
the collection pipes.
The experience at this facility
illustrates the ineffectiveness of a
piecemeal approach to correcting
problems that recur because of faulty or
inadequate design and construction.
Conclusions
Conclusions Drawn from the
Case Studies
1. Successful facilities must have
adequate site investigation, good
project planning during design
and construction, and rigorous
execution of a comprehensive
QA/QC program. Problems
resulting from inadequate site
investigation and poor design and
construction cannot be completely
corrected through piecemeal
remedies applied as the problems
surface.
2. The cornerstones of an effective
QA/QC program are competent
and conscientious supervision
and inspection of construction
and rigorous documentation and
recordkeeping. The QA/QC
program should cover all steps of
the facility's development
planning, design, construction,
etc. The program should also
encompass all system elements,
support facilities, operations, and
corrective measures (monitoring
wells, leak detection subdrains,
dredging, repairs, etc.).
3. QA/QC programs for facilities
lined with FML's should emphasize
liner-waste compatibility in liner
selection, proper installation
procedures (especially seaming),
and the use of protective cover
(particularly for liners exposed to
severe elemental stresses).
4. Unless properly designed,
groundwater monitoring programs
are not reliable substitutes for
subdrain leak detection systems.
Groundwater monitoring is more
reliable for providing advance
warnings of site failures and
thereby allowing corrective
measures to be taken in time.
5. The successful performance of
surface impoundments at two of
the facilities was due to (1) a very
impermeable clay liner, (2)
extensive waste-liner permeability
studies, (3) competent design,
construction, and inspection
contractors, (4) close scrutiny of
all phases of design, construction,
and QA inspection by the
owner/operator, (5) excellent
QA/QC and recordkeeping
during all project phases, and (6)
good communication among all
parties involved in establishing
the sites.
6. Case studies documenting the
performance of hazardous waste
facilities can provide the
necessary feedback for evaluating
various designs and construction
techniques and can yield valuable
lessons for improving design,
construction, monitoring, and
operating procedures.
7. The facilities rejected for this
study more accurately represent
existing SI practices (no engineered
site, presence of other pollution
source, no data on hydrogeology or
site construction, and insufficient
monitoring data for performance
evaluation).
Conclusions Based on
Professional Opinions and the
Experience of Experts
1. Siting in suitable geological
formations is the best protection
and the first line of defense against
groundwater contamination,
regardless of liner type.
2. In the intragradient design, the
facility is intentionally located in
the saturated zone and the high
groundwater table provides a
positive pressure that can prevent
migration of leachate or waste in
the event of failure.
3. Geotechnical support should be a
continuous effort covering not only
site investigation and facility design
but construction as well.
4. The QA/QC program is essential
for guaranteeing the adequancy of
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a completed facility. The key
elements of the program should be
thorough construction inspection,
use of competent and conscientious
inspectors, and detailed documenta-
tion and recordkeeping.
5. The most critical factor in clay liner
construction is compaction under
proper moisture conditions.
Compaction should be aimed at
eliminating all air spaces and not
necessarily at achieving certain
arbitrary Proctor density levels.
Compaction wet of optimum is
generally sufficient to ensure
elimination of air spaces and
development of a very impermeable
liner.
6. Dessication cracking of clay is
highly site- and situation-specific.
Since liners are constructed in lifts
and there is little chance for
alignment of cracks in adjacent
lifts, a limited number of shallow
cracks not detected during
inspection should present no major
leakage problem.
7. The critical factors in installing a
successful FML are selection of a
suitable liner material, use of
proper installation procedures,
rigorous application of QA/QC, and
provision and maintenance of
protective cover for the liner.
8. Waste-liner compatibility should be
re-examined whenever the
character of the waste changes.
Compatibility problems can be
minimized with good site design
and operating practices, pretreat-
ment, and banning of certain
wastes.
9. FML installation problems can be
minimized by experienced
installers, good field supervision
and technical assistance to the
installer, and minimal field
seaming.
10. Protective cover for a liner is
essential to prevent damages from
the elements, vandalism, pinholes,
animals, and chemicals.
11. Use of an FML and a clay liner
together provide the advantages of
both systems and compensate for
the shortcomings of the individual
liners.
12. Sporadic plugging of underdrain
leachate collection systems
remains a problem. No practical
measure currently exists to restore
hydraulic capacity when a sand and
gravel drainage system is plugged.
13. Subdrain leak detectors are
superior to monitoring wells and
other indirect methods because
they permit direct observation,
allow more rapid detection of
failure, permit monitoring over a
relatively large area under the
liner, and yield more reliable
results. Groundwater monitoring
may not provide a true picture of the
background conditions and
changes in water quality.
Recommendations
A technical manual should be compiled
with the considerable accumulated
experience in the waste disposal field.
The manual should detail how site
selection, design, construction,
operation, monitoring, maintenance, and
repair relate to each other.
The present study should be extended
to include additional case studies and
experiences of technical experts. The
results should be distributed to practicing
engineers, owners/operators of
hazardous, waste management facilities,
regulatory agencies, and active
researchers.
Specific items that need further study
include the following:
The effectiveness of various FML's
Seaming methods for FML's
QA/QC procedures
Liner-waste compatibility
The intragradient and hydraulic
barrier concepts
Methods for minimizing and
correcting clogging in leachate
collection systems
Methods for obtaining clay
permeability data
Methods for detecting and
correcting site failures
Technical basis and criteria for
proper design of groundwater
monitoring systems
Techniques for monitoring the
unsaturated (vadose) zone
Methods for pinpointing liner leaks
and repairing them
The full report was submitted in
fulfillment of Contract No. 68-02-3174 by
MESSA under the sponsorship of the
U.S.Environmental Protection Agency.
&U. S. GOVERNMENT PRINTING OFFICE: 1985/559-111/10771
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Massood Ghassemi, Michael Haro. and Linda Fargo are with MESS A. Torrance,
CA 90504.
Carlton Wiles is the EPA Project Officer (see below).
The complete report, entitled "Assessment of Hazardous Waste Surface
Impoundment Technology: Case Studies and Perspectives of Experts," (Order
No. PB85-117059; Cost: $25.00, subjectto change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
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Penalty for Private Use S300
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