\ I /
                   United States
                   Environmental Protection
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
                   Research and Development
EPA-600/S2-84-173 Jan. 1985
&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

  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

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
  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.

  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
  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-

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
Placed in SI Size
Service (Acres}
Waste Type
Acidic process liquor and
sludge waste (pH <2) high in
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
Pesticide formulation
and distribution plant
 Pesticide washdown
 evaporation disposal
 Pesticide rinsewater
 evaporation disposal
1979    <0.1

1982    <0.1
Pesticide rinsewater
                                                                    Pesticide rinsewater
Batch operation
(400 gal/day
Batch operation
(400 gal/day
Commercial hazardous   Site A: 8 impoundments
waste disposal          used for settling.
facility                 storage, and sludge
                            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
                       One cooling pond
1965    14       Production water for ammonium      20,000 gal/day
                  phosphate/phosphoric acid plant
                  with pH <2 and high radionuclides
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
High-head evaporation
pond (treatment and
Evaporation pond
(treatment and storage)
high arsenic and boron
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
                                   A total of 50 million
                                   gal/month to Ponds
                                   A-E, 4, and 5
                                                                                                        12 million gal/
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

      fertilizer manu-
      facturing plant
Cooling pond (treatment)
                           Initial gypsum pond
                           Expansion gypsum pond
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
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/
 Tailings pond
 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
  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

                             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

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-

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
  • 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

  • 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.

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
  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 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

   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

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

    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

 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

 9. FML  installation problems can be
    minimized   by experienced
    installers, good field supervision
    and technical assistance to  the
    installer, and minimal  field

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

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.

  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
  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

      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
Center for Environmental Research
Cincinnati OH 45268
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