United States
                     Environmental Protection
Municipal Environmental Research
Laboratory                        .  _  .
Cincinnati OH 45268               ' "i *
                     Research and Development
EPA-600/S2-83-109  Feb.  1984
4>ERA          Project  Summary
                     Potential  Clogging  of  Landfill
                     Drainage  Systems

                     Jeffrey M. Bass, John R. Ehrenfeld, and James N. Valentine
                       The  potential  clogging of landfill
                     drainage systems was investigated with
                     particular emphasis on hazardous sites.
                     The study accomplished five  basic
                     tasks: (1) to provide general background
                     on the subject of drain clogging; (2) to
                     investigate some cemented  materials
                     found in a drain at a landfill in Boone
                     County, Kentucky, and to determine
                     possible causes; (3) to examine  the
                     potential  for clogging  in hazardous
                     waste leachate collection systems; (4)
                     to  identify  preventive or  remedial
                     techniques for drain clogging; and (5) to
                     identify avenues or research and devel-
                     opment that might minimize the like-
                     lihood or impact of clogging.
                       Study results indicate that clogging is
                     likely to occur in a probabilistic manner
                     during the active and  post-closure
                     operational  lifetime of a hazardous
                     waste landfill,  but preventive and
                     remedial techniques can be used to
                     avoid or mitigate clogging. Preventive
                     methods (including  increased safety
                     factors or redundancy in design, moni-
                     toring, periodic inspection.and mainte-
                     nance) are far  superior to  remedial
                     techniques. Repair or replacement is
                     expensive and potentially dangerous in
                     the hazardous environment at secure
                     landfills. Present regulations for hazard-
                     ous waste landfills provide no guidance
                     on engineering, design, or operational
                     practices to prevent clogging or remedy
                     a malfunctioning system.
                       This Project Summary was developed
                     by EPA's Municipal Environmental
                     Research Laboratory, Cincinnati, OH,
                     to announce key findings of the research
                     project  that is fully documented in a
                     separate report of the same  title (see
                     Project Report ordering information at
  Clogging caused by a variety of mechani-
sms is common to drainage systems of all
kinds  agricultural irrigation, sanitary
landfills, septic system leach fields, etc.
Concern is  particularly great over the
potential clogging of leachate collection
systems in hazardous waste landfills. Not
only are  the consequences of failure
much higher at a hazardous waste site,
but excavation and replacement are no
longer simple last resorts.
  In response to this concern, this report
investigates the potential  clogging of
landfill drainage systems with particular
emphasis on hazardous waste sites. The
study was designed to accomplish the
following tasks:
  1. To provide general background on
    the subject of drain clogging;
  2. To investigate cementitious materi-
    als found in gravel around a drain at
    a  U.S. Environmental Protection
    Agency demonstration sanitary
    landfill in Boone County, Kentucky,
    and to determine possible causes;
  3. To examine the potential for clog-
    ging in hazardous waste leachate
    collection systems;
  4. To identify and describe potentially
    useful preventive or remedial techni-
    ques to avoid, minimize, or eliminate
    drain clogging; and

  5. To identify fruitful avenues for
    research and development to mini-
    mize the likelihood or impact of
      The study was  initiated  with a
    literature review of field experience
    and a limited laboratory study of the
    materials recovered from the Boone
    County Landfill.

Information Base
  To assess the potential for clogging of
leachate collection systems, information
was obtained from the following areas:
  1. Regulations to  the Resource Con-
     servation and Recovery Act (RCRA),
  2. Design of leachate collection sys-
  3. Leachate characteristics,
  4. Mechanisms of drain clogging, and
  5. Relevant experience.
  Literature from related fields such as
agricultural  drainage  and irrigation
systems provided most of the background
because information and direct experi-
ence with leachate collection systems in
general is sparse. Although many differ-
ences exist between conditions  of
leachate drains and other kinds of drains,
basic mechanisms leading to clogging are
similar  in all systems.  In particular, a
paper prepared for EPA by GCA Corpora-
tion (C.W. Young,  T.J. Nunno, M.R.
Jasinski, D.R. Cogley, and S.V. Capone,
"Clogging of Leachate  Collection Sys-
tems  Used in Hazardous Waste Land
Disposal Facilities," Draft  White Paper,
U.S. Environmental  Protection Agency,
Washington, D.C. In press) was used as a
starting point for the  research in this

Clogging Mechanisms
  Clogging mechanisms are occurrences
or natural processes that inhibit the flow
of leachate to or through the  leachate
collection  system. Such as system at a
landfill is  considered to be clogged if it
cannot maintain  the leachate depth over
the liner at less that 30-cm limit required
in the RCRA standards. The majortypesof
clogging mechanisms in leachate collec-
tion systems are physical, chemical,
biochemical, and biological mechanisms.
  Physical mechanisms are  the most
common, most well understood causes of
drain failure.  Physical factors  tend  to
predominate  in  many  drainage system
cloggings, though any combination of
factors might occur. Physical failure can
be due to inadequate capacity, structural
failure, or sedimentation or filtration.
  Chemical mechanisms for  clogging
involve the formation of insoluble precipi-
tates that are deposited on the surfaces
inside of drain pipes, in openings (slots),
and in the drain-pipe envelopes (gravel
and geotextile filters). The most common
form of chemical  buildup  is calcium
carbonate. Manganese carbonate (rhodo-
chrosite) and  other insoluble forms
(sulfides and silicates) have been found in
clogged or partially encrusted drainage
  Biochemical mechanisms occur when
inorganic precipitates are  formed  in
conjunction  with  biological systems  in
addition to the other simpler mechanisms.
The principal  products resulting from
biochemical  mechanisms  are iron com-
pounds    Fe(OH)3  or  FeS (though
manganese  compounds  may also be
involved). These compounds are deposit-
ed on pipe surfaces and in the envelope
material.  The deposits generally contain
organic material as well  in the form  of
adherent, sometimes filamentous slimes
and organic  complexes.
  Biological  mechanisms  are formed
when organisms grow to fill the intersti-
ces in the drain envelope and interfere
with normal flow of leachate. For such
growth to occur, bacteria must be present
in a  supportive  environment. Many
bacteria  are known to use  hazardous
organic chemicals for food and can grow
at the temperature,  pH, and oxygen
content found in landfills. Heavy metals
often present in hazardous waste landfills
may be toxic or inhibitory to the clog-form-
ing species.

Analysis of Deposits Found at
the Boone County, Kentucky,
  When Test Cell 1 of the Boone County,
Kentucky, field site was  dismantled  in
September 1980 after 9 years of testing,
a section of partially cemented gravel was
discovered in the drain envelope extend-
ing 2.2 to 4.2 m (6.5 to 13.5 ft) from the
collection sump (bulkhead). The discovery
of the cemented section was significant
because the test cell had been constructed
to provide a better understanding of such
  Analyses included a physical examination
of the cement material (scanning electron
microscopy, optical microscopy, and X-ray
diffraction and fluorescence analysis) and a
chemical  analysis of the mass to determine
primary chemical constituents. Results of
these  studies lead to the preliminary
conclusion that the cement is principally a
calcium-iron-magnesium product containing
significant proportions of  carbonate (gas
evolution) and phosphate. In addition, a
relatively large proportion of fine silica
appears to be dispersed in the cement. The
lack of significant X-ray diffraction patterns
suggests that the cement is an amorphous
material rather than composed of discrete
crystalline phases. Little can be said about
the clogging  mechanisms at work here, but
carbonate incrustation is  likely to  have
contributed. The role of iron is not yet clear.
   In addition to determining the cement
composition, it is important to know why
the cementation occurred only in a limited
portion 2.2 to 4.2 m (6.5 to 13.5 ft) above
the collection sump of the upper drain. One
explanation is that conditions in the wastes
above that section were different from
those elsewhere, but data are not sufficient
to follow  that approach.  Differences in
operating  procedures during  the first  7
months of test cell operation caused leach-
ate to back up in the pipe and could have
caused  at  least the beginnings of  the
cementation. Further investigation is
needed  for a more definitive conclusion,

Potential  for Clogging at
Hazardous Waste  Landfills
  The potential for clogging of leachate
collection  systems at hazardous waste
landfills is of particular concern since ex-
cavation and replacement are not simple
last resorts (as they are in sanitary land-
fills) and  since the consequences of
failure  are  very high. Unfortunately,
direct assessment of clogging potential at
hazardous waste or sanitary landfills is
difficult because little experience has
been had with modern leachate collec-
tion systems. Thus it is useful to compare
the clogging  potential of these systems
with agricultural drainage  systems,
where clogging is clearly a serious prob-
lem. Table 1  indicates that relative poten-
tial for clogging of agricultural drains and
leachate collection systems at sanitary
and hazardous waste landfills  based on
the major  potential  clogging  mechan-
isms.  Crushing problems  appear  to be
more likely to occur at both hazardous
waste and  sanitary  landfills,  whereas
chemical, biochemical, and  biological
clogging appear less  likely to occur in
hazardous waste systems. This differ-
ence is  primarily due  to the  lower pH
range and the potential toxicity of chemi-
cal constituents to indigenous bacteria.
Sedimentation and pipe deterioration are
also potential problems in  hazardous
waste systems.

Prevention and Remedies
   Preventive and remedial measures can
be used to address problems with drain
clogging. Preventive measures are inten-
ded to interrupt the sequence of causal
steps necessary for a clogging mechanism
to occur. Prevention of drain clogging can
be accomplished in the following areas:
    design and construction,
    operation and maintenance,
    waste disposal, and
   Remedial  measures are intended to
eliminate the clogging problem once  it

 Table 1.   Relative Potential for Clogging of Leachate Collection Systems
  fof+, -)


  Chemical (CaCOa)

  Biochemical (Ochre, Fe)

                        Compact/on, greater
                        equipment loading

                        Less careful design and
                        construction possible

                        Chemicals, solvents,
                        low pH not expected

                        Lower pH

                        Toxicity to indigenous
                        bacteria, lower pH

                        Toxicity to indigenous
                        bacteria, lower pH
* = possible,  * less likely, and * = more likely.

has occurred. Remedial measures for
clogged drain systems include:
   excavation and replacement,
   physical methods, and
   chemical methods.
Examples of preventive and  remedial
measures are presented in Tables 2 and

  The following conclusions are based on
information and analyses summarized in
the full report.

  1. Based on the analysis presented in
    the full  report and on past experi-
    ence with agricultural drainage sys-
    tems, sanitary landfills, and (to a
    limited  extent) hazardous waste
    landfill leachate collection systems,
    it is reasonable to expect clogging to
    occur in a probabilistic manner dur-
    ing  the active and post-closure
    operational  lifetime of a hazardous
    waste landfill.
  2. Mechanisms that affect other types
    of  systems are expected to  con-
    tribute  to  clogging in hazardous
    waste landfills. This  study was
    limited to an examination of clog-
    ging in the drainage system per se 
    that is, the pipes, envelope, and out-
    let system.  {The regulatory defini-
    tion of "clogging" as used here could
    also  involve  localized blockages
    within the waste mass that rest on
    the liner and create leachate head
    greater  than the permissible limit,
    but this  potential problem was not
    examined in depth.)
  3. Landfill  operators exhibited a vary-
    ing degree of concern over the clog-
    ging potential of drainage systems.
          Most appeared to view the potential
          problem as unimportant in both de-
          sign and operational considerations
          and felt that conventional practices
          should be  adequate to prevent or
          remedy clogging. Only one source
          noted  that the  prevention  and
          mitigation of clogging received care-
          ful and special attention in their de-
          sign and operational considerations.
       4. Established preventive and remedial
          techniques to avoid or mitigate clog-
          ging can  generally be  used  at
          hazardous waste sites. Acid flush-
          ing should be used with great care,
          particularly if cyanides are known to
          be present.
       5. Preventive  methods (including in-
          creased safety factors or redun-
          dancy in design, monitoring, perio-
          dic inspection, and maintenance)
          are far superior to remedial tech-
          niques. Repair and replacement are
          often considered quite practical in
          other settings, but they are expen-
          sive and potentially dangerous in
          the hazardous environment at se-
          cure landfills.
       6. The present regulations regarding
          hazardous waste landfills do not ap-
          pear to treat clogging system design
          and  head buildup with the same
          thoroughness and  level of detail as
          liner design or loss of integrity. The
          regulations give substantial discre-
          tion to regional administrators with
          regard to the drainage system.  Nei-
          ther the regulations nor other sup-
          porting  documents provide guid-
          ance on engineering, design or op-
          erational practices  to  prevent clog-
          ging or remedy a  malfunctioning

  A number of recommendations for fur-
ther research on leachate collection sys-
tems can be made based on the results of
this study. The recommendations listed
below are given with the understanding
that it is important to integrate technical
solutions with practical experience and
expectations. Technical solutions arising
from laboratory-based research and de-
velopment alone are not likely to be im-
plemented if they are considered too ex-
pensive or too complicated to apply under
existing or future conditions. Conducting
technical  research  in conjunction with
experience on operating leachate collec-
tion systems can help avoid this problem.
  1.  Specific design and construction
     guides should be developed for
     leachate collection systems  simi-
     lar, perhaps, to the EPA Technical
     Resource Documents, which provide
     guidance for  the  design  and con-
     struction of liner  systems. Such a
     guide could be used by the Regional
     Administrators in  approving facili-
     ties,  or by the Administrator in
     preparing  regulations for leachate
     collection systems. Aspects of any
     of  the following recommendations
     could also  be  included in this task.
  2.  Specific operational procedures should
     be developed to prevent clogging.
     An effective program of treatment
     and maintenance  can control the
     factors needed for cloging mecha-
     nisms to occur and and thereby avoid
     the clogging  problems.  This task
     should include a  cost analysis of
     alternative preventive approaches.
  3.  Monitoring methods to detect clog-
     ging  or conditions that promote it
     should be  developed to  anticipate
     problems before they become too
     serious. Conventional techniques
     can be applied from  related fields
     such as groundwater hydrology, and
     new techniques can be developed to
     indicate when significant clogging
     processes are occurring.
  4.  A quantitative analysis  should be
     made  of the probability of  the
     various clogging mechanisms. Spe-
     cific  preventive and  remedial ap-
     proaches can then be evaluated in the
     context of hazardous waste landfills
    to  determine their  quantitative
     effects on  clogging potential. This
     recommendation  would involve
    both  a  paper study and a  field
     investigation under typical hazard-
    ous waste  landfill conditions.
  5.  Methods for preventing and correct-
    ing clogs in drain envelopes or filter

Table 2.    Preventative Measures for Drain Clogging
Design and Construction
Operation and Maintenance
Waste Disposal
pipe diameter 6"

pipe in protective
  cradle, soil cover
sealed Joint construction
corps grain size
  distribution  criteria
submerged outlet
slope 2 percent
pipe size, estimated

displacement, slotsize
filter material

anaerobic conditions
flow rate
                            exercise special care in     all design
                             in design and construction
                            design for prevention       all


structural,  sedimentation

chemical, biochemical
capacity, sedimentation
  biochemical, biological
capacity, sedimentation.
care during placement      crushing, displacement  structural
  compaction, operation in
  vicinity of drain
regular monitoring and      all                    all
  inspection of system
cleaning                  all                    all
minimize nutrients

dispose biocides, toxics
maintain low pH

avoid solvents, oxidizing



chemical attact
biochemical, biological

biochemical, biological
chemical, biochemical,
                       biochemical, biological
facilitate remedial measures, maintenance

use high strength pipe

use slotted or perforated pipe
options include graded. 2 or more layers
  geotextile, 4" minimum depth

depends also on quantity of flow
                                                manholes, c/eanouts, large pipe, etc.

                                                most important for first lift of waste
identify factors, early stages of
  clogging for preventative cleaning
removes potential clogging in early
  stages, use flushing, low pressure jet

organics, N and P compounds, other
acids, bases, heavy metal wastes
contributes to deterioration
                          add directly to collection system
                          kills bacteria, removes early stages
TableS.    Remedial Measures of Clogged Drains

 Category	Measure	
Excavation and

Physical Methods
 Chemical Methods


    low pressure jets

    high pressure jets
    flushing (sub-

    SOz gas
                                SuHamic Acid
           complete remedy
           limited for inactive deposits, not
             effective for slots, but good in
             combination with other methods

           effective for ochre. FeS. sediments
             limited for mature deposits

           same as low pressure but can cause
             damage to drain envelope and better
             for mature deposits

           less than jets
           effective for ochre. Mn in 2 cases,
             ineffective in one case for ochre
                                     effective for ochre
                                      most expensive option; difficult
                                        at hazardous waste sites

                                      Koto-rooter, pigs, sewer balls,
                                        snakes, buckets
                                                                                                                  70-140 psi at nozzle
                                                                                                                 440 - 1300 psi at nozzle
                                      rate of use = / lb/7.Sg water,
                                        dangerous to personnel and
                                        environment, cost is 7 percent
                                        of replacement

                                      strength required depends on
                                        organic matter and age of ochre
                                        NaCOa used to neutralize
                                        treated live	

   layers should be developed. Currently,
   no satisfactory remedial methods exist
   short of excavation and replacement.
6.  Experimental data on the perform-
   ance of leachate collection systems
   (including detailed  leachate flow
   and composition data) should be
   gathered at both  sanitary  and
   hazardous waste  landfills on a
   continuing basis. Such a data base
   is vital in evaluating leachate
   collection system performance and
   in developing design and operational
   guides to ensure  proper system
   functioning throughout its required
     The full report was submitted in
   fulfillment of Contract No. 68-01 -5949
   by Arthur  D. Little, Inc.,  under  the
   sponsorship of the U.S. Environmental
   Protection Agency.
Jeffrey M. Bass, John R. Ehrenfeld, and James N. Valentine are with Arthur D.
  Little. Inc., Cambridge. MA 02140.
Michael Slimak is the EPA Project Officer (see below).
The complete report, entitled "Potential Clogging of Landfill Drainage Systems,"
  (Order No. PB 84-110 550; Cost: $10.00. subject to 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:
        Municipal Environmental Research Laboratory
        U.S. Environmental Protection Agency
        Cincinnati, OH 45268

United States
Environmental Protection
Official Business
Penalty for Private Use $300
Center for Environmental Research
Cincinnati OH 45268
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                                                                              U.S. GOVERNMENT PRINTING OFFICE: 1984-759-102/853