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Fact  Sheet  on Evapotranspiration
Cover Systems  for Waste Containment
                      TABLE OF CONTENTS

               INTRODUCTION	1

               BACKGROUND	2

               DESCRIPTION	3

               LIMITATIONS	6

               DESIGN CONSIDERATIONS	6

                  Climate	6

                  Soil Type	7

                  Soil Thickness	7

                  Vegetation Types	7

                  Soil Fertility	8

                  Control Layers	8

               PERFORMANCE MONITORING	8

                  Monitoring Systems	9

                  Numerical Models	9

               COST	10

               TECHNOLOGY STATUS	11

               REFERENCES 	11

               GLOSSARY	13

               APPENDIX A: Proposed, Approved, and
               Installed Sites Having Evapotranspiration
               Covers	15

               APPENDIX B: Data From Two
               Comparison Demonstration Projects	24
                                 INTRODUCTION

                                 This fact sheet updates the Evapotranspiration
                                 Landfill Cover Systems Fact Sheet that was pub-
                                 lished in 2003. At that time evapotranspiration
                                 (ET) covers were more in a demonstration phase.
                                 Now they are increasingly being  considered for
                                 use  at  waste  disposal  sites.  These include
                                 municipal solid waste (MSW) landfills, hazard-
                                 ous waste (HW) landfills, and isolated arid waste
                                 sites when equivalent performance to conven-
                                 tional final cover systems can be demonstrated.
                                 Conventional cover system designs use barrier
                                 layers consisting of materials with low hydraulic
                                 conductivity (e.g., clay, geosynthetic clay liners,
                                 or geomembranes) to minimize the percolation
                                 of water from the cover to the waste. ET cover
                                 systems use  water balance components to  mini-
                                 mize percolation.  These cover systems rely on
                                   The alternative covers  database contains
                                   222 project profiles. These project profiles
                                   include site background information, cover
                                   type and construction details, status (pro-
                                   posed, complete,  under construction), cost
                                   information, and  contacts. Sources  of in-
                                   formation include  EPA and state websites,
                                   conference proceedings, studies, and indi-
                                   vidual contributions. Individuals wishing to
                                   have a cover they are  familiar with listed
                                   can submit it online. The database is updat-
                                   ed  as new information becomes available.

                                   Appendix A of this document contains a list
                                   of ET sites by EPA region and state.

                                   http://cluin.org/products/altcovers
             This fact sheet is intended solely to provide general information about evapotranspiration covers. It is not intended, nor can it be
             relied upon, to create any rights enforceable by any party in litigation with the United States. Use or mention of trade names does
             not constitute endorsement or recommendation for use.
             United States
             Environmental Protection
             Agency
                    Office of Solid Waste and
                    Emergency Response
                    (5203P)
                                                     EPA 542-F-11-001
                                                     February 2011
                                                     www.epa.gov
                                                     www.cluin.org

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soil properties (e.g., soil texture and associated
soil water storage capacity) to store water until it
is either transpired through vegetation or evapo-
rated from the soil surface.

The fact  sheet provides a summary of ET tech-
nical  issues, including  design considerations,
performance monitoring, cost, technology status,
and potential limitations  on  use.  It is intended
to  provide basic information  to site owners  and
operators, regulators, consulting engineers,  and
other  interested parties  about these potential
design alternatives. Appendix A updates the 2003
list of ET cover sites by adding over 130 new full
scale examples. A separate on-line database  pro-
vides  more site specific information about these
sites as well as other projects using ET covers.

Additional sources of information are also provided
in the  project specific references in the database.

The information contained in this fact sheet  was
obtained  from currently available technical litera-
ture and  from discussions with site managers. It
is not intended  to  serve  as guidance for actual
design or construction,  nor is it intended  to sug-
gest that ET final cover systems should be used
at  any particular site.1 The fact sheet does not
address alternative materials for use in final cover
systems, or other alternative  cover  system
designs,  such as asphalt covers.

BACKGROUND

Final cover systems often are used at landfills;
abandoned dumps; some hazardous, low-level,
and mixed  low-level waste sites with conducive
environmental conditions; hazardous waste con-
tainment facilities; sites  with surface contami-
nation; and other types of waste disposal sites.
There are a number of reasons for using them,
including  to control moisture and  percolation,
manage  surface water  runoff, minimize erosion,
prevent direct exposure  to  waste,  control  gas
emissions  and odors, prevent  occurrence of
disease vectors and other nuisances, and meet
aesthetic and other end-use purposes. Final cov-
er  systems are  intended to remain in place  and
maintain their  functions for periods of many
1 For example, EPA's Superfund remedy selection
decisions  are made on a site-specific basis. Thus,
final cover systems are evaluated in a manner consis-
tent with the overall framework established for remedy
selection  under CERCLA, the National Oil and Haz-
ardous Substances Pollution Contingency Plan,  and
associated Superfund program guidance.
decades to hundreds of years. Cover systems
may be used alone or, if warranted, in conjunc-
tion with other technologies (for example, slurry
walls and groundwater pump and treat systems)
to contain waste or leachate.

The design of cover systems is site specific and
depends on the intended function of the final
cover-cover designs  can range from a  single
layer of soil to a complex multi-layer system that
includes synthetic  materials.  To minimize  per-
colation, conventional cover  systems typically
use low-conductivity barrier layers. These barrier
layers are often constructed of compacted clay,
geomembranes, geosynthetic clay liners, or com-
binations of these  materials. Depending on the
material type and construction method, the satu-
rated hydraulic conductivities forthese barrier layers
are typically between 1x10~5 and 1x10"9 centime-
ters per second (cm/s). In addition, conventional
cover systems  generally include shallow-rooted
plants  and additional layers, such as surface
layers to prevent erosion;  protection  layers to
minimize freeze/thaw damage; internal drainage
layers; and gas collection layers (Environmental
Protection Agency  [EPA] 1991; Hauser, Weand,
and Gill 2001 b).

The  design, construction, and  maintenance of
cover systems  may be subject to statutory and
regulatory  requirements  under  various  federal
and state programs; some of these requirements
also may come into  play in cleanup programs.
For example, with regard to municipal solid waste
facilities, regulations under the Resource Conser-
vation and  Recovery Act (RCRA) for the design
and construction of final cover systems are based
on using a low-conductivity barrier layer (conven-
tional cover system). Under RCRA Subtitle D (40
CFR 258.60), the minimum design requirements
for final cover systems at municipal solid waste
landfills (MSWLF)  depend  on the bottom liner
system or the natural subsoils, if no liner system
is present.  The final cover system  must  have a
permeability    than or equal to that of the bot-
tom liner system (or natural subsoils) or a  perme-
ability no greater than 1x10'5 cm/s, whichever is
less. This design requirement was established to
minimize the "bathtub effect," which occurs when
the landfill fills with liquid because  the cover
system  is more permeable than  the bottom liner
system. This bathtub effect greatly increases the
potential for generation of leachate.

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Until March 2004, the equivalent reduction lan-
guage provided the statutory underpinning for
proposing an  alternative cover  at an  MSWLF.
On March 22,  2004, 40 CFR 258 was amended
to allow  for research,  development, and  dem-
onstration permits (40  CFR 258.4). These per-
mits are  issued for three years with up to three
renewals (12 years total). The regulation states,
"The director of an approved state may issue a
research, development,  and demonstration per-
mit for a new  MSWLF unit,  existing  MSWLF
unit, or lateral expansion, for which the owner or
operator  proposes to utilize innovative and new
methods  which vary from the final  cover crite-
ria of §258.60(a)(1), (a)(2)  and (b)(1), provided
the MSWLF unit owner/operator demonstrates
that the infiltration of liquid through  the alterna-
tive cover system will not cause contamination of
groundwater or surface water, or cause leachate
depth on  the liner to exceed 30 cm."

Figure 1 shows  the minimum  recommended
requirements for  a typical conventional Subtitle
D landfill which consist  of a 6-inch  soil  erosion
layer, a geomembrane (when  the landfill has a
geomembrane liner), and an 18-inch  barrier layer
of soil that  is compacted to yield  a saturated
hydraulic conductivity equal to or  less than 1x10'5
cm/s (EPA 1992).
                                 Geomembrane
                               Composite barrier
  (a) MSW Landfills



      As required {?,£}£'   TopSOil layer  '$.-f$>
         -r
  > Frost penetration $jfjJ!& Cover soil layer
   0.6 m

As required
              t^a^a!»^: )
            i^.i' Compacted clay layer X-^( i
            :^;    fc £ 10 ' em/s   'f^ f
                Gas drainage (ayer
                                 .Geomembrane
Composite barrier
  (b) Hazardous Waste Landfills

 Source EPA 1992a and 1989
  Figure 1. Examples Subtitle D and C Cover
  Design.
As another example, for hazardous waste landfills,
RCRA Subtitle C (40 CFR 264 and 265) provides
certain  design  specifications  for  final  cover
systems. These include the same provision for
Subtitle D that the cover system have a permea-
bility less than or equal to the permeability of any
bottom liner system or natural subsoils present.
To help implement these regulatory requirements,
EPA has issued guidance forthe minimum design
of these final cover systems. Figure 1  shows an
example of a RCRA Subtitle C cover at a hazard-
ous waste landfill (EPA 1989).

The  design and construction  requirements, as
defined in the  RCRA regulations,  also  may be
applied under  RCRA corrective action  and other
cleanup  programs  (e.g., Superfund   or  state
cleanup programs). At Superfund  remedial sites
involving on-site disposal, the RCRA regulations
for conventional covers usually are identified as
applicable or relevant and  appropriate  require-
ments  (ARARs) for the  site.2 Under RCRA, an
alternative  design, such  as an ET cover, can
be proposed in lieu of a RCRA design  if it can
be demonstrated that the  alternative  provides
equivalent performance with respect to reduction
in percolation and other criteria, such as erosion
resistance and gas control.

Examples of sites that have proposed, approved,
or installed ET covers and the regulatory program
they are operating under are given  in AppendixA.
Details on these sites can be found in the alter-
native cover profiles database at http://cluin.org/
products/altcovers.

DESCRIPTION

ET cover systems are designed to rely on the
ability of a soil layer to store the precipitation until
it is naturally evaporated or is transpired by the
vegetative cover. In this  respect they differ from
more conventional cover designs in that they rely
on obtaining an appropriate water storage capac-
ity in the soil rather than an  as-built engineered
low hydraulic  conductivity. ET cover  system
designs are based on  using the  hydrological
processes (water balance components) at a site,
which include  the water storage capacity of the
soil,  precipitation, surface runoff,  evapotranspi-
ration,  and  infiltration. The greater the  storage
capacity and evapotranspirative properties are,
the lower the potential for percolation through the
cover system.
                                              2 In addition to compliance with ARARs, CERCLA Sec-
                                              tion 121 requires that remedial actions ensure protec-
                                              tiveness of human health and the environment.

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ET cover system designs tend to emphasize the
following (Dwyer 2003; Hakonson 1997; Mauser,
Weand and Gill 2001 b):

•   Fine-grained soils, such as silts and  clayey
   silts, that have a relatively high water storage
   capacity

•   Appropriate vegetation for long-term stability
   and evapotranspiration

•   Locally available soils to streamline construc-
   tion and provide for cost savings
Use of local soils allows the opportunity to utilize
natural analogue data for speculating future per-
formance.

In addition to being called  ET cover systems,
these types of covers have also been referred to
in the literature as water balance covers, alterna-
tive earthen final covers, vegetative landfill covers,
soil-plant covers, and store-and-release covers.

ET cover systems are constructed using a mono-
lithic soil barrier. Monolithic covers, also referred
  Exhibit 1. Monolithic Cover at Lopez Canyon Sanitary Landfill

  Site type: Municipal solid waste landfill

  Scale: Full scale

  Cover design: The ET cover was installed in 1999 and consists of a 3-foot silty sand/clayey sand layer,
  which overlies a 2-foot foundation layer. The cover soil was placed in 18-inch lifts and compacted to 95
  percent with a permeability of less than 3x10'5 cm/s. Native vegetation was planted, including arteme-
  sia, salvia, lupines, sugar bush, poppy,  and grasses. In 2001, fifty 30-KW microturbines that use landfill
  gas as fuel were installed at the site. They provide sufficient electricity to power 1,500 homes.

  Regulatory status: In 1998, Lopez Canyon Sanitary Landfill  received conditional approval for an ET
  cover, which required a minimum of two years of field performance data to validate the model used for
  the design. An analysis was conducted and provided the basis for final regulatory approval of the ET
  cover. The cover was fully approved in  October 2002 by the California Regional Water Quality Control
  Board - Los Angeles Region.

  Performance data: Two moisture monitoring systems were installed, one at Disposal Area A and one at
  Disposal Area AB+ in May and November 1999, respectively. Each monitoring system has two stacks of
  time domain reflectometry probes that measure soil moisture  at 24-inch intervals to a maximum depth
  of 78 inches, and a station for collecting weather data. Based  on nearly 3 years of data, there is gener-
  ally less than a 5 percent change in the relative volumetric moisture content at the bottom of the cover
  compared to nearly 90 percent change near the surface. This implies that most of the water infiltrating the
  cover is being removed via evapotranspiration and is not reaching the bottom of the cover.

  Modeling: The numerical model UNSAT-H was used to predict the annual and cumulative percolation
  through the cover. The model was calibrated with 12 months of soil moisture content and weather data.
  Following calibration, UNSAT-H predicted a cumulative percolation of 50 cm for the ET cover and 95
  cm for a conventional cover over a 10-year period. The  model predicted an annual  percolation of
  approximately 0 cm for both covers during the first year. During years 3 through  10 of the simulation,
  the model predicted less annual percolation for the ET cover than for the conventional cover.

  Maintenance activities: During the first 18 months, irrigation was conducted to help establish the veg-
  etation. Once or twice a year, brush is cleared to  comply with  Fire Department regulations. Prior to the
  rainy season, an inspection is conducted to check and clear debris basins and deck inlets. No mowing
  activities or fertilizer applications have  been conducted  or are planned.

  Cost: Initial costs were estimated at $4.5 million, which includes soil importation, revegetation, quality control
  and assurance, construction management, and installation  and operation of moisture monitoring systems.

  Sources: City of Los Angeles 2003, Hadj-Hamou and Kavazanjian 2003. More information available at
  http://cluin.org/products/altcovers

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                          Vegetation

                          Fine-grained Layer


                          Interim Cover


                          Waste
  Figure 2. Conceptual Design of a Monolithic
  ET Cover
                         Vegetation

                      •*— Fine-grained Layer


                         • Coarse-grained Layer

                         • Interim Cover

                         • Waste
   Figure 3. Conceptual Design of a Capillary
   Barrier ET Cover
to as monofill covers, use a single  fine-grained
soil layer to retain water and support the vegeta-
tive community (Albright et al. 2010  and Mauser
2009). Figure 2 shows an example of a  mono-
lithic ET cover. Exhibit 1 provides an example of a
full-scale monolithic cover at a MSW landfill.

A monolithic  cover design  can be  modified by
adding  a  capillary  break. This  entails placing
a  coarser grained  material, usually a sand  or
gravel, under the  monolithic fine-grained soil, as
shown conceptually in Figure 3. The differences
in the unsaturated hydraulic properties (i.e., soil
matric potential) between the two layers minimize
percolation into the coarser grained  (lower) layer
under unsaturated conditions  (Stormont  1997).
The finer-grained layer has the same function as
the monolithic soil layer; that is, it stores water
until  it  is removed from the  soil by evaporation
or transpiration mechanisms.  The discontinuity
in  pore  sizes between the coarser-grained and
finer-grained layers forms a capillary break at the
interface of the two layers. The break results in
the wicking of water into unsaturated pore space
in  the finer grained soil, which allows the finer-
grained layer to retain more water than a  mono-
lithic cover system of equal thickness.  Capillary
forces  hold the water in the finer-grained layer
until  the soil near the interface approaches sat-
uration. If saturation of the  finer-grained layer
  Exhibit 2. Capillary Barrier ET Cover at Rocky Mountain Arsenal Superfund Site

  Site type: Consolidation area covers

  Scale: Full scale

  Cover design: These RCRA Subtitle C equivalent ET covers have been constructed for former waste
  disposal basins and manufacturing process areas that were contaminated during pesticide production.
  The design consists of a minimum of 16 inches of crushed concrete placed as a biota barrier, followed
  by a capillary barrier layer of pea gravel that provides a capillary break.  The surface soil layer consists
  of at least 4 feet of soil seeded with a mix of cool and warm season native vegetation.

  Modeling: Construction parameters were developed using data from a four year RCRA equivalent dem-
  onstration study. The  modeling was done using UNSAT-H.

  Maintenance activities: Construction began in 2007 and finished in 2009. The covers are currently being
  monitored and maintained.

  Performance: The ET cover performance is monitored using a number of pan lysimeters  (30 feet x 50
  feet) which have shown that the cover is performing  as expected.

  Cosf: According to the responsible party, the total cost of constructing the ET covers was $69  million,
  and they cover approximately 450 acres.

  Sources:  Rocky Mountain Arsenal cleanup site: http://www.rma.armv.mil/: and EPA Region 8 Superfund
  site: http://www.epa.aov/reaion8/superfund/co/rkvmtnarsenal/index.html.

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occurs, the water will move relatively quickly into
and through the coarser-grained layer and to the
waste below (Albright et al. 2010, Hauser 2009,
and ITRC 2003). Exhibit 2 provides an example
of a capillary barrier at a Rocky Mountain Arsenal
hazardous waste site.

In addition to being potentially less costly to con-
struct, ET covers have the potential to provide equal
or superior performance compared to conventional
cover systems, especially in arid  and semi-arid
environments (generally accepted  as areas hav-
ing  less than 10 and  20  inches of precipitation,
respectively). In  these environments, they may
be less  prone to deterioration from desiccation,
cracking, and freezing/thawing cycles. ET covers
also may be able to minimize side slope instability,
because they do not contain geomembrane layers,
which can cause slippage (Albright and Benson
2005, Benson et al. 2002; Dwyeret al. 1999).



Although they have  been approved in  humid
climates  (e.g., Marine Corps Logistics  Station
Albany, GA  and  General Electric, Schenectady,
NY), ET cover systems are generally considered
more  applicable in areas that have arid or semi-
arid climates like those found in parts of the Great
Plains and West (e.g., North and South Dakota,
Montana,  Idaho, eastern Washington and Ore-
gon, Utah, Colorado, West Texas, New Mexico,
Arizona, Nevada,  and southern California).
Albright and Benson (2005)  in their examination
of data  generated  in  EPA's Alternative  Cover
Assessment Program (ACAP) found: "In  humid
locations  with the  abundant precipitation  and
typically lower potential evapotranspiration, the
store-and-release  mechanism used by ET cov-
ers  does not provide sufficient hydraulic control
to match the performance of conventional com-
posite covers." (emphasis added) However, the
ACAP field data did show that in humid locations
properly designed ET covers can provide perfor-
mance comparable to that of the compacted day
covers in those locations.

In addition, site specific conditions, such as site
location  (e.g., appropriate  soil) and landfill char-
acteristics, may  limit the  use or effectiveness
of ET cover systems.  Local climatic conditions
(amount, seasonal distribution, and form of pre-
cipitation) also can limit the  effectiveness of an
ET  cover at a given site. For  example, snow
often melts when vegetation is dormant, and with-
out sufficient water storage capacity unaccept-
able percolation might occur (EPA 2000; Hauser,
Weand, and Gill 2001 b).  However, if technically
and financially feasible, this might be mitigated by
thickening the ET layer.

Two federal  research programs, the Department
of Energy (DOE)  sponsored Alternative  Land-
fill Cover Demonstration (ALCD) and  the ACAP,
provide the  best collection  of  data to describe
the performance of ET cover systems  in terms of
minimizing percolation. Hauser  (2009) also has
some  additional performance information;  how-
ever, there are limited data on the ET covers' abil-
ity to  minimize  erosion, resist  biointrusion, and
retain  long-term effectiveness. On the other hand,
erosion, effectiveness of biobarriers, and mainte-
nance of vegetative cover over extended periods
of time are issues faced by  all conventional cov-
ers, and those design aspects  are  similar to ET
covers. While the principles of ET covers and their
corresponding soil  properties have been under-
stood  for many years, their application as final
cover systems for landfills has emerged only since
the mid-1990s.  Regulators in southern California
initially required any landfill operator who wanted
to deploy an ET cover to set up a demonstration
project to prove equivalency.  The success of these
demonstrations  has led to the regulators allowing
an ET  cover if the  landfill  owner shows that soil,
design, and climatic conditions are similar to those
of a landfill facility with a permitted ET cover.


The design  of  ET cover systems  is based  on
providing sufficient water storage  capacity and
evapotranspiration  to control moisture and water
percolation into  the underlying waste. The follow-
ing considerations  generally are involved  in the
design of ET covers.

Climate

The amount, form, and distribution of precipita-
tion over a year, combined with factors that influ-
ence potential evapotranspiration, determine the
total amount of water storage capacity needed for
the cover system. This information can usually be
found  at nearby weather stations. The cover may
need to accommodate a spring snowmelt event
that causes  the amount of water at the cover to
be relatively  high for a short period of time or con-

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   Summary of Key Design Considerations

   «   Climate—amount, form and timing of
      precipitation determines storage capac-
      ity need

      Soil Type—finer grained soils are  pre-
      ferred for fertility and storage capacity

   •   Soil Thickness—combined with soil
      type determines storage capacity  of
      cover

   •   Vegetation Types—must be appropriate
      for location with well developed root
      systems to promote transpiration and
      provide long-term  performance

   •   Soil Fertility—to sustain vegetation
      when plants are used

   «   Control Layers—biobarriers, gas collec-
      tion, and drainage  layers are used  as
      needed
ditions during cool winter weather with persistent,
light precipitation. Storage capacity is particularly
important if the event occurs when  local vegeta-
tion is dormant, resulting in little or  no transpira-
tion. Other factors related to climate that are im-
portant to cover design are temperature, wind,
and relative  humidity (Benson 2001;  EPA 2000;
Hauser, Weand, and Gill 2001 b).

Soil Type

Finer-grained materials, such as silts  and clayey
silts, are typically used for ET cover systems be-
cause they have a greater storage capacity than
sandy soils. Sandy soils are typically used for the
bottom layer of the ET capillary barrier cover sys-
tem to provide a contrast in unsaturated hydrau-
lic properties between the two layers. Many ET
covers are constructed of soils that include clay
loam,  silty loam, silty sand, and sandy loam. The
storage capacity of the soil varies among differ-
ent soil types and requires laboratory  analysis to
quantify. One key aspect of construction is avoid-
ing over-compaction (greater than 80-90%) dur-
ing placement. Higher bulk densities  from over-
compaction may reduce the storage capacity of
the soil and  inhibit growth  of roots (Chadwick et
al. 1999;  Hauser etal. 2001).
Soil Thickness

The thickness of the soil layer(s) depends on the
required storage capacity, which is determined by
the water balance at the site. The soil layers need
to accommodate the design climate conditions,
such as snowmelts and summer thunderstorms,
or periods of time during which ET rates are low
and plants are dormant. Monolithic ET covers
have been constructed with soil  layers  ranging
from 2 feet to 10 feet. Capillary barrier ET covers
have been  constructed with finer-grained lay-
ers ranging from 1.5 feet to 5 feet, and coarser-
grained layers ranging from 0.5 feet to 2 feet.

In some  arid to semiarid areas, when there  is
a lack of local  precipitation data, the potential
performance of an ET cover might be estimated
by natural analog. This is done by trenching and
examining the trench walls for a caliche layer.
Caliche  (CaCO3)  is  a precipitation  product and
when  shallow generally  indicates  the level  of
deepest recent percolation. Also, an accumula-
tion of soluble ions such as  chloride can indicate
the depth of recent percolation.

Vegetation Types

Vegetation for the cover system  is  used to pro-
mote transpiration and minimize erosion by stabi-
lizing the surface of the cover. It can also be used
for  aesthetics  or  to  promote habitat.  Grasses,
shrubs, and trees  have all been used on ET cov-
ers. A mixture of native plants generally is planted,
though not  always, because native vegetation
usually is more tolerant than imported vegetation
to regional conditions, such as extreme weather
and disease. A combination of warm-  and  cool-
season  species should  provide water uptake
throughout the entire growing season, which
enhances transpiration.  In  addition,  native veg-
etation species are less likely to disturb the natural
ecosystem (Dwyeretal. 1999;  EPA2000).

If deep rooting  vegetation is considered for the
cover, the designer should consider whether root
penetration into the waste area will  result in any
transport of constituents  into  the above ground
biomass. The presence of constituents such as
heavy metals or radionuclides in leaf  and  stem
tissue could  present a hazard.

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Finally, consideration needs to be given to how long
the selected vegetation will take to establish itself
and how this will affect the cover's performance.

Soil Fertility

When vegetation is a component of an ET cover
system, the evaluation of the soil that is proposed
for the cover (not the subgrade) should include a
determination of whetherthe pH, cation exchange
capacity, organic matter, and nitrogen, phospho-
rus, potassium, and micronutrient content are
appropriate for the vegetation proposed for use
on the cover (ITRC  2003b, Albright et al. 2010).
Amendments, such  as lime, biosolids, sawdust,
or synthetic conditioners, can be worked into the
soil to improve  its suitability for planting and/or
water storage capacity. These types  of amend-
ments, while  adding to the cover construction
cost, tend to be long-lived  and should not need to
be repeated. Fertilizers and amendments,  such
as manure, can be added at  initial planting to help
establish the cover;  however, they are not  long-
lived and must be reapplied  in nutrient-poor soils
on a regular basis. The need for reapplication of
fertilizers will present an ongoing cost to the proj-
ect and should be  carefully evaluated in selecting
an ET cover over a conventional cover. While it is
not necessary that borrow soils  be obtained on-
site or locally, the cost of transporting them any
distance should be considered (e.g.,  it could be
prohibitively expensive).  For  a  more complete
discussion, see Section 5.2 Preconstruction Cov-
er Material Specifications of ITRC 2003b.

Control Layers

Control layers, such as those used to minimize
animal intrusion, promote drainage, and control
and collect landfill gas, are often included for
conventional cover systems and may also be in-
corporated into ET cover system designs. For ex-
ample, a capillary barrier ET cover for the mixed
waste landfill at Sandia National  Laboratories in
New Mexico has  a  one-foot-thick crushed rock
biobarrier located  beneath the soil cover (about
four feet bgs) to prevent animals from burrowing
into the waste layer. Because of the difference
in  size between the soil and the  rock, the rock
layer also acts  as a capillary break. At another
site, Monticello Uranium Mill Tailings Site in Utah,
an ET capillary barrier design has a cobble  layer
as an animal intrusion barrier located within the
fine soil layer and above the 12-inch thick capil-
lary barrier layer.
                 MONITORING

Protection of groundwater quality often is a pri-
mary performance goal for all waste containment
systems,  including final  cover systems. The
potential adverse impact to groundwater quality
can result from the release of leachate generated
in landfills or other closed in-place waste disposal
units such as unlined surface impoundments.
The rate of leachate generation (and potential
impact on  groundwater) can be minimized  by
keeping liquids out of a  landfill or contaminated
source area of a remediation site.  As a result,
the function of minimizing percolation  typically
becomes a key performance criterion for a final
cover system (EPA 1991).

Monitoring the performance of ET cover systems
has generally focused on evaluating the  ability
of these designs to minimize water drainage into
the waste. Percolation performance typically is
reported  as a flux rate (inches or millimeters of
water that have migrated downward through the
base of the cover in  a period of time, generally
considered as 1  year). Percolation  monitoring
for ET cover systems is  measured directly using
pan lysimeters or estimated indirectly using soil
moisture measurements  and soil matric potential,
thereby allowing  the calculation of a flux rate. A
more detailed summary  on the advantages and
disadvantages of both approaches can be found
in Benson et al. (2001) and EPA (2004).

Percolation  monitoring  can also be evaluated
indirectly by using leachate collection and removal
systems. For landfills underlain with these sys-
tems,  the amount and composition of leachate
generated can be used as an indicator of the
performance  of a cover system (the  higher the
percolation, the more leachate that will be gener-
ated) (EPA 1991).

Although the ability to  minimize percolation is
a performance criterion  for final cover systems,
limited  data are available about percolation per-
formance for final cover systems for  both conven-
tional and alternative designs. Most  of the recent
readily available data on  flux rates have  been
generated by theACAPandALCD programs; see
Appendix B for discussion and data presentation.
From these programs, flux rate performance data
are available for 14 sites with demonstration-
scale  ET cover systems (Dwyer 2003, Albright
and Benson 2005).

-------
Additional demonstration  projects  of ET cov-
ers conducted in the 1980s and early 1990s are
discussed in the ACAP Phase I Report, which is
available at http://www.dri.edu/acap-research.

Monitoring Systems

Direct measurement of water flowing through the
bottom of a  cover can be done using a  pan ly-
simeter. The lysimeters are installed underneath
the cover system, typically as geomembrane lin-
ers backfilled with a drainage layer and shaped to
collect  water percolation.  Water collected in the
lysimeter is  directed toward a monitoring  point
and measured using a variety of devices  (for ex-
ample,   tipping  bucket,  pressure transducers).
Pan lysimeters were used  in the ALCD and ACAP
programs for collecting performance data for ET
cover systems and  are part of the design for the
Rocky Mountain Arsenal cover systems. They are
the monitoring system of  choice for equivalency
demonstrations.  Details of the ACAP lysimeters
are in Albright et al. (2004).

Soil moisture monitoring  can be used to deter-
mine moisture  content at discrete locations in
cover systems and to evaluate changes overtime
in horizontal or vertical  gradients. Soil water prop-
erties are measured using a variety of methods
and include  methods  for  determining soil mois-
ture (TDR, neutron attenuation, and  resistivity),
soil humidity (psychrometer), and soil matric po-
tential (heat dissipation units or HDUs). Table 1
presents examples of non-destructive techniques
that have been used  to assess soil moisture
content of ET cover systems. A  high soil mois-
ture value indicates that the water content of the
cover system is approaching its storage capacity,
thereby increasing  the potential for percolation.
Soil moisture is especially important for capillary
barrier  ET cover systems; when the finer grained
layer becomes saturated,  the capillary  barrier
can fail resulting in water percolating through the
highly permeable layer to the waste below (Ha-
konson  1997). Monitoring instruments have vari-
ous configurations, costs, and accuracies. The
choice  of which one to use would depend on the
site data quality objective.

Maintaining the effectiveness of the cover system
for an extended period of time is another impor-
tant performance criterion for ET covers  as well
as  conventional covers.  Some factors to con-
sider in  evaluating short-term and long-term per-
formance monitoring of a final cover system in-
clude settlement effects, gas emissions, erosion
or slope failure,  and maintenance of vegetative
cover. These factors can be monitored using a
variety of methods including settlement gauges,
erosion pins, TDR cables for subsidence, soil gas
wells and associated sampling ports, and remote
sensing (e.g., LIDAR).

Numerical Models

Models can  be  used  to support the design of
ET covers. Although models have strengths and
weaknesses and none  can accurately predict
cover behavior in all environments, in their sim-
plest application, a model can be used to test the
assumptions made  in the  designer's conceptual
model. Agood example of this is where model sim-
ulation shows a cover thickness that is clearly too
thin or shows diminishing returns in  adding more
soil  beyond  an  optimum thickness to achieve
water storage  capacity.  Simulations by several
models to test the conceptual model and design
can be very  useful in identifying critical assump-
tions where  a  small change can result in large
performance deviations.  Identifying  sensitive as-
sumptions allows for more conservative design
specifications or the application of greater quality
control checks. If such a procedure is desirable, a
model using Richards' equation (ITRC 2003b) is
necessary to properly simulate the  mechanisms
important to cover function. At sites where ET en-
gineered  barriers are expected to last hundreds
or thousands of years (e.g., DOE low-level radio-
active burial grounds), the  modeling should in-
clude extreme weather events and their resultant
affects on engineered barrier design.

A number of models have been used for estimat-
ing water balances. Research  reviewed for this
fact  sheet suggests that opinions differ among
practitioners about how successful a given model
will be in predicting  cover  performance. A mod-
el  should only  be selected  after examining its
strengths and weaknesses  in simulating site-spe-
cific conditions. For example, if early snowmelt is
a critical factor, how well does the  model  simu-
late it? For design purposes  it might be prudent,
though somewhat more expensive, to use two
models, such as a water balance and a numeri-
cal model, to estimate cover performance (Khire
et  al. 1997). Table 2  in Chapter 3 of Albright et al.
(2002) compares the processes and attributes of
10 models.

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Table 1. Examples of Non-Destructive Soil Moisture Monitoring Methods
Method
Capacitance sensor
Electrical resistance blocks
Gee lysimeter
Thermal dissipation unit
Neutron attenuation
Psychrometer
Suction lysimeter
Tensiometer
Time domain reflectrometry
Description
Uses frequency domain induced polariza-
tion to measure the dielectric properties of
the soil. The dielectric of dry soil is ap-
proximately 5, and the dielectric of water
is approximately 80. When soil becomes
moistened by water, its dielectric increases.
Measures resistance resulting from a gradi-
ent between the sensor and the soil; higher
resistance indicates lower soil moisture
Wicks water from soil around a collection
container and measures the resulting water
level in the container directly
Uses a heated ceramic block to determine
soil moisture near the block. The rate of
heat dissipation from the block is related to
soil moisture — the quicker the dissipation
the higher the soil moisture.
Emits high-energy neutrons into the soil that
collide with hydrogen atoms associated with
soil water and counts the number of pulses,
which is correlated to moisture content
Measures relative humidity (soil moisture)
within a soil
Collects pore (unsaturated) water directly
Measures the matric potential of a given
soil, which is converted to soil moisture
content
Sends pulses through a cable and observes
the reflected waveform, which is correlated
to soil moisture
Instrumentation
Consists of a probe connected to
a coaxial cable and buried at
appropriate depth
Consists of electrodes embedded
in a gypsum, nylon, or fiberglass
porous material
Consists of a small collector body
and a wick. The water level in the
collector body is measured by an
electronic water level gauge.
Consists of a small heater inside
a porous block with a temperature
sensor attached by cable to a
surface meter
Consists of a probe inserted into
access boreholes with aluminum
or polyvinyl chloride casing
Generally consists of a thermo-
couple, a reference electrode,
a heat sink, a porous ceramic
bulb or wire mesh screen, and a
recorder
Constructed of a porous ceramic
bulb with a cylindrical reservoir to
store water. A tube to the surface
allows water to be drawn and
measured.
Commonly consists of a porous
ceramic cup
Consists of a cable tester (or
specifically designed commercial
time domain reflectrometry unit),
coaxial cable, and a stainless
steel probe
The numerical model HELP is a widely used water
balance model that is most appropriate for non-
ET landfill cover design. UNSAT-H, VADOSE/W
and HYDRUS-1D/2D/3D are examples of numer-
ical models that have been used frequently for
the design of ET covers. Some models are in the
public domain, others require purchase.  Mauser
(2009) recommends using the  water  balance
Erosion Productivity Impact Calculator  (EPIC),
which is in the public domain, for ET cover mod-
eling. EPIC is a water balance model and does
not use Richards equation.
COST

Despite the large number of projects installed to
date, limited cost data are available for the con-
struction and operation  and maintenance of ET
cover systems. The available  construction cost
data indicate that these  cover systems have the
potential to be  less expensive  to construct than
conventional cover  systems,  especially  those
requiring geomembranes. Factors affecting the
cost of construction include soil layer thickness,
availability  of materials, placement methods, and
                                             10

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project scale. Locally available soils are typically
used for ET cover systems. In addition, the use
of local materials generally minimizes transporta-
tion costs  (Dwyer 2003, EPA 2000). Also, when
comparing  the  costs  for ET  and conventional
covers,  it  is important to consider the types of
components for each cover and their intended
function. For example, it would generally not  be
appropriate to compare the costs for a conven-
tional cover with a gas collection layer to an ET
cover with no such  layer. Additional information
about the costs for specific ET cover systems is
provided in some of the project profiles discussed
under Technology Status.

TECHNOLOGY STATUS

EPA has  developed  and recently  updated a
searchable  on-line  database with  information
about ET cover systems, available at http://cluin.
org/products/altcovers. As of February 2011, the
database contained 167 projects with full scale
monolithic ET cover systems and 5 projects with
capillary barrier ET cover systems; these sys-
tems  have been  proposed, tested, or installed
throughout the  United  States.  Full  scale  appli-
cations  have primarily been in the Great Plains
and western states.  Where data are available,
the database provides project  profiles that  in-
clude site  background information (such as site
type, climate, hydrogeology), project information
(such as purpose, scale, status), cover informa-
tion (such as design, vegetation, installation), per-
formance and cost information, points  of contact,
and references. Appendix A provides a summary
of key information from the database for projects
with monolithic ET or capillary barrier ET covers.

In addition to this on-line database, several fed-
eral and state programs have demonstrated and
assessed the performance of ET cover systems.
The  following  programs provide performance
data, reports, and other useful information to help
evaluate the applicability of ET designs for final
cover systems.

•   Alternative Landfill Cover Demonstration:
   See  Exhibit 3 in Appendix B for more infor-
   mation or http://www.sandia.gov/Subsurface/
   factshts/ert/alcd.pdf.

•   Alternative Cover Assessment Program: See
   Exhibit 4 in Appendix B for more information
   or http://www.dri.edu/acap-research.
•  Interstate Technology and Regulatory Council
   published two reports on ET covers: Technol-
   ogy Overview Using Case Studies of Alter-
   native Landfill Technologies and Associated
   Regulatory Topics and Technical and Regu-
   latory Guidance for Design, Installation, and
   Monitoring of Alternative Final Landfill Cov-
   ers. For further information, see http://www.
   itrcweb.org/guidancedocument.asp?TID=21.

In the initial stages of its program, California re-
quired any landfill that desired to employ an ET
cover to conduct a demonstration  project. The
success of these demonstrations has led to the
regulators  allowing  an ET cover if the  landfill
owner shows  soil, design, and climatic condi-
tions are similar to those of a landfill facility with
a permitted ET cover. Texas has a similar pro-
gram. Both of these states have seen a signifi-
cant increase in the number of landfills using or
proposing ET covers.

REFERENCES

Abichou, T, X. Liu, and K. Tawfiq. 2004. Design
of Cost Effective Lysimeters for Alternative Land-
fill Cover Demonstrations Projects, Report #04-
0232007. Florida State University, College of En-
gineering. 88 pp.

Albright, W, G. Gee, G. Wilson, and M. Fayer.
2002. Alternative  Cover  Assessment Project
Phase  I Report, Publication  No. 41183. Desert
Research  Institute, NV. 203 pp.

Albright,  W., C. Benson,  G.  Gee, A. Roesler,
T. Abichou, P. Apiwantragoon,  B.  Lyles, and S.
Rock, 2004, "Field Water Balance of Landfill Final
Covers."  J. of Environmental Quality,  33;2317-
2332.

Albright, W. and C.  Benson. 2005. Alternative
Cover Assessment Program:  Report to Office of
Research  and  Development National Risk Man-
agement Research Lab Land Remediation and
Pollution Control Division. Desert Research Insti-
tute and University of Wisconsin, 54 pp.

Albright, W, W. Waugh, and C. Benson. 2007.
Enhancements to Natural Attenuation: Selected
Case Studies, Washington Savannah River Com-
pany, WSRC-STI-2007-00250, p 9-30.
                                              11

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Albright, William  H., Craig H. Benson, and W.
Joseph  Waugh,  2010.  Water Balance Covers
for Waste  Containment  Principles and Practice,
ASCE Press, 158 pp.

Benson, C.H. 2001. "Alternative  Earthen  Final
Covers  (AEFCs)  or 'ET Caps." GEO Institute.
Proceedings, Liners and Covers for Waste  Con-
tainment Facilities.  Atlanta, Georgia.  November
14-16.

Benson, C.H. et  al. 2001. "Field Evaluation of
Alternative Earthen Final  Covers." International
Journal  of Phytoremediation. Volume  3, Number
1, p 105-127.

Benson, C.H. et  al. 2002. "Evaluation of  Final
Cover Performance: Field  Data from the Alterna-
tive Landfill CoverAssessment Program (ACAP)."
Proceedings, WM 2002 Conference. Tucson, Ari-
zona. February 24-28.

Benson, C.H,, A. Sawangsuriya, B.Trzebiatowski, and
W.H.Albright2007. "Postconstruction Changes in
the Hydraulic Properties of Water Balance Cover
Soils." Journal of Geotechnical and Geoenviron-
mental Engineering 133(4):349-359.

Bolen, M.M. et al. 2001. Alternative CoverAssess-
ment Program: Phase  II  Report. University of
Wisconsin-Madison. Madison, Wisconsin.  Sep-
tember.  Geo Engineering Report 01-10.

Chadwick, Jr., D. et al. 1999. "Field Test of Poten-
tial RCRA-Equivalent Covers at the Rocky Moun-
tain Arsenal, Colorado."  Solid Waste Association
Proceedings, North America's 4th Annual Land-
fill Symposium. Denver, Colorado. June 28-30.
GR-LM0004, p21-33.

City  of  Los Angeles. 2003.  Personal commu-
nication regarding  Lopez  Canyon Landfill  from
Doug Walters, Sanitary Engineer, Department of
Public Works, to Kelly Madalinski, EPA. Septem-
ber 25.

Dwyer, S.  2003.  Water  Balance Measurements
and  Computer Simulations of  Landfill Covers.
University  of New Mexico, Civil Engineering De-
partment. May.

Dwyer, S.F., J.C.  Stormont, and C.E. Anderson.
1999. Mixed Waste Landfill  Design Report. Sandia
National Laboratories. SAND99-2514. October.
Hadj-Hamou,  T. and  E. Kavazanjian,  Jr. 2003.
"Monitoring and Evaluation of Evapotranspirative
Cover  Performance." Proceedings of the 9th
International Waste Management and  Landfill
Symposium, Sardinia, Italy, 6-10 October.

Hakonson, T.E. 1997. "Capping as an Alternative
for Landfill Closures-Perspectives  and Ap-
proaches." Environmental Science and Research
Foundation. Proceedings, Landfill Capping in the
Semi-Arid West:  Problems, Perspectives, and
Solutions. Grand Teton National Park, Wyoming.
May 21 -22. ESRF-019. p 1 -18.

Hakonson, T, et al. 1994. Hydrologic Evaluation
of Four Landfill Cover Designs  at Hill Air Force
Base, Utah. Los Alamos National Laboratory, Los
Alamos, New Mexico. LAUR-93- 4469.

Hauser, V.L.,  and  B.L. Weand. 1998.  "Natural
Landfill Covers." Proceedings,  Third Tri-Service
Environmental Technology Workshop.  San
Diego,  California. August 18-20.

Hauser, V.L., B.L. Weand, and  M.D. Gill. 2001 a.
"Natural Covers for Landfills and Buried Waste."
Journal of Environmental  Engineering. Sept. p
768-775.

Hauser, V.,  B. Weand, and M. Gill. 2001 b. Alter-
native Landfill Covers. Air Force Center for Envi-
ronmental Excellence. 38 pp.

Hauser, Victor L. 2009. Evapotranspiration Cov-
ers for Landfills and  Waste Sites. CRC Press,
Boca Raton, FL. ISBN: 13: 978-1-4200-8651-5,
203 pp.

ITRC. 2003a.  Technology Overview Using Case
Studies of Alternative Landfill Technologies and
Associated Regulatory Topics. 107 pp.

ITRC.  2003b.  Technical and Regulatory Guid-
ance for  Design,  Installation, and Monitoring of
Alternative Final Landfill Covers. 198 pp.

Kelln, C.J.,  S.L. Barbour, A.  Elshorbagy, and  C.
Qualizza. 2006. "Long-Term Performance of a
Reclamation Cover: The Evolution of Hydraulic
Properties and Hydrologic  Response." Unsatu-
rated Soils  2006: Proceedings  of the 4th Inter-
national Conference on Unsaturated Soils, 2-6
April 2006, Carefree, Arizona. ASCE, Reston, VA.
Geotechnical Special Publication No. 147, ISBN:
0784408025.
                                             12

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Kelsey, J.A., J.T. Kay, M. Ankeny, and M. Plummer.
2006. "Darcian Flux Estimations in Evapotranspi-
ration Landfill Covers." Unsaturated Soils 2006:
Proceedings of the 4th International Conference
on Unsaturated Soils, 2-6 April 2006, Carefree,
Arizona. ASCE, Reston, VA. Geotechnical Spe-
cial Publication No. 147, ISBN: 0784408025.

Khire,  M.V.,  C.H. Benson, and  P.J. Bosscher.
1997. "Water Balance Modeling of Earthen Final
Covers." Journal  of Geotechnical and Geoenvi-
ronmental Engineering. August, p 744- 754.

McGuire, P.E., J.A. England, and B.J. Andraski.
2001. "An Evapotranspiration Cover for Contain-
ment  at a Semiarid  Landfill Site." Florida State
University.   Proceedings,  2001   International
Containment & Remediation Technology Confer-
ence. Orlando, Florida. June 10 -13.

Mitchell, M. 2009. Mixed Waste Landfill Quarterly
Progress Report Evapotranspirative Cover Con-
struction Project, August - October 2009. Sandia
National Laboratories, 38 pp.

Roesler, A.C.,  C.H. Benson, and WH. Albright.
2002. Field Hydrology and Model Predictions for
Final Covers in the Alternative Cover Assessment
Program-2002. University of Wisconsin-Madison.
Geo Engineering Report No.  02-08. September
20, 279 pp.

Scanlon, B.R., et al. 2002. "Intercede Compari-
sons  for Simulating  Water Balance of  Surficial
Sediments in Semiarid Regions." Water Resources
Research. Volume 38, Number 12

Scanlon, B.,  R. Reedy, K. Keese, and S. Dwyer.
2005.  "Evaluation  of  Evapotranspirative  Cov-
ers for Waste Containment in Arid and Semiarid
Regions in the Southwestern US." Vadose Zone
Journal, 4, p. 55-71.

Stormont, John C. 1997. "Incorporating Capillary
Barriers in Surface Cover Systems." Environmental
Science and  Research Foundation. Proceedings,
Landfill Capping  in the Semi-Arid West: Prob-
lems, Perspectives, and Solutions. Grand Teton
National Park, Wyoming.  May 21 through 22.
ESRF-019, p 39-51.
EPA. 1989. Technical Guidance Document: Final
Covers on Hazardous Waste Landfills and Sur-
face Impoundments. EPA/530-SW-89-047. July.

EPA.  1991.  Seminar Publication,  Design and
Construction of RCRA/CERCLA Final Covers.
EPA/625/4-91/025. May.

EPA 1992a.  Seminars:  Design, Operation, and
Closure of  Municipal  Solid  Waste  Landfills.
EPA/600/K-92/002

EPA. 1992b. Subtitle D Clarification. 40 CFR 257
& 258. Federal Register pages 28626 through
28632.June.

EPA.  2000.  Introduction to  Phytoremediation.
Office of Research and Development. Washington,
DC. EPA/600/R-99/107.  February.

EPA. 2004. Survey of Technologies for Monitor-
ing Containment Liners and Covers, EPA 542-R-
04-013, 64pp.

Weand, B.L. et al. 1999. "Landfill Covers for Use
at Air Force Installations." AFCEE. Brooks Air
Force Base, Texas.  February.
   NOTICE

   Preparation of this fact sheet has been
   funded wholly by the U.S. Environmental
   Protection Agency under Contract Num-
   ber EP-W-07-037. For more information
   regarding this fact sheet,  please  con-
   tact Steve Rock at (513) 569-7149 or
   rock.steven@.epa.gov or Linda Fiedler at
   (703) 603-7194 or fiedler.linda@.epa.aov.

   This fact sheet is available for viewing or
   downloading from EPAs Hazardous Waste
   Cleanup Information (CLU-IN) web site at
   http://cluin.org.
                                             13

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GLOSSARY

Arid and  semi arid climates.  In 1953, Peveril
Meigs divided desert regions on Earth into three
categories according to the amount  of precipita-
tion they received. In this now  widely accepted
system, extremely arid lands have at least 12 con-
secutive months without rainfall, arid lands have
less than 250  millimeters of annual  rainfall, and
semiarid lands have a mean annual  precipitation
of between 250 and  500 millimeters. Arid and
extremely  arid  land  are  deserts, and  semiarid
grasslands generally are  referred to  as steppes.
(USGS webpage http://pubs.usgs.gov/gip/deserts/
what/)

Caliche. A subsurface carbonate horizon formed
in a soil in  an arid to semiarid region under condi-
tions of low rainfall. The  leaching of carbonates
from the upper soil by precipitation combined with
its limited downward percolation results  in an
accumulation of carbonates that form  an  often
hard carbonate horizon and designate the deep-
est penetration of the precipitation.

Composite cover. A landfill cover that includes a
synthetic layer such as a geomembrane.

Dump. An area where illegal waste disposal has
occurred.

Evapotranspiration. The combination  of water
lost from the soil through direct  evaporation and
water lost  to the atmosphere through plant tran-
spiration.

Geosynthetic clay  liner. A woven fabric that
encases a clay material, generally a  smectite
clay, to provide a low permeability layer.
Hydraulic conductivity. In hydrology, a numeric
coefficient describing the rate that  water can
move through a porous media. Usually expressed
in cm/sec.

Infiltration. The movement of water from the soil
surface into the soil.

Natural analog. A subsurface feature that occurs
naturally  that can be used to evaluate a similar
engineered feature. In ET design the presence of
a near surface caliche layer or chloride ion accu-
mulation  gives an indication of how deep precipi-
tation is percolating in the subsurface.

Percolation. The movement of waterthrough soil.

Permeability. The  capacity of a porous media to
transmit a fluid.

Richards equation. A numerical representation of
unsaturated flow of a fluid through porous media.

Water balance. In  the context of a landfill cover,
the evaluation of the end fate of precipitation; that
is, percent run-off, infiltration, evaporation, tran-
spiration, and percolation.

Store and release. In the context of an ET cover,
the cover soil will store precipitation (i.e.,  prevent
its drainage  into the  underlying waste),  until the
water either evaporates or is transpired by the
vegetative cover.
                                               14

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APPENDIX A
  AND
    15

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This table is a list by region and state of sites that have proposed, approved, or installed ET covers.  It
also contains sites that had demonstration scale pilots, which may or may not have gone on to full scale.
Proposed covers include sites where an ET cover has been proposed by the facility and approved by the
governing agency (e.g., California)  or has  been proposed  by the facility but  approval  is pending (e.g.,
Texas). In Texas the proposal is generally to amend an existing permit to add ET covers as an option. The
state of Oklahoma provided a list of landfills that had approved and installed ET covers as did the states of
Colorado and Montana. The state of Arizona provided electronic copies of the permits of facilities that had
approved or installed ET covers. The California Regional Water Control Boards maintain  electronic copies
of their permits on their webpages as does the state of Utah. Sites were excluded from the list if the permit
specifically called  for a water infiltration barrier layer even though the permit referred to the cover as an ET
cover. A legend and list of definitions is found at the end  of the table.

Evapotranspiration Covers
Site
Program
Type of
Site
Scale
Status
Type of
Cover
Region 1
Region 2
New York
GE Main Plant, Schenectady, NY
State-Licensed Radioactive Waste Disposal Area,
West Valley, NY
RCRA
NRC
HWS
Rad
F
Demo
Installed
Complete
M
BE
Region 3
Maryland
Beltsville Agricultural Research Center (USDA),
Beltsville, MD
College Park Landfill, College Park, MD
College Park Landfill, College Park, MD
NRC
CERCLA
CERCLA
Rad
MSW
MSW
Demo
Demo
F
Complete
Complete
Proposed
BE
M
M
Pennsylvania
Welsh Road Landfill, Honeybrook, PA
CERCLA
MSW
F
Installed
M
Region 4
Georgia
Marine Logistics Base Albany Georgia
Marine Logistics Base Albany Georgia
ACAP
CERCLA
MSW
MSW
Demo
F
Complete
Installed
M
M
Region 5
Illinois
Sheffield City Landfill, Sheffield, IL
NRC
Rad
Demo
Complete
CB
Michigan
Casting Sand Landfill, Detroit, Ml
RCRA
IW
Demo
Complete
M
Wisconsin
Omega Hills, Milwaukee, Wl
RCRA
MSW
Demo
Complete
CB
Region 6
New Mexico
Cerro Colorado Landfill, Albuquerque, NM
Chemical Waste Landfill at Sandia National
Laboratories, Albuquerque, NM
Crouch Mesa Landfill, Farmington, NM
Kirtland Air Force Base, Albuquerque, NM
RCRA
RCRA
RCRA
RCRA
MSW
HWS
MSW
HW
F
F
F
F
Proposed
Installed
Proposed
Installed
M
M
M
M
                                               16

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Site
Los Alamos National Laboratory, Los Alamos, NM
Mixed Waste Landfill at Sandia National Laboratories,
Albuquerque, NM
Molycorp Tailings Facility, Questa, NM
Red Rocks Regional Landfill, Thoreau, NM
Rio Rancho Landfill, Rio Rancho, NM
Sandoval County Landfill, Bernalillo, NM
Sandia National Laboratories, Albuquerque, NM
San Juan County Landfill, Aztec, NM
Valencia Landfill, Los Lunas, NM
Program
DOE Research
RCRA
CERCLA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
Type of
Site
Rad
MW
HWS
MSW
MSW
MSW
NHWS
MSW
MSW
Scale
Demo
F
F
F
F
F
Demo
F
F
Status
Complete
Installed
Proposed
Proposed
Approved
Proposed
Complete
Approved
Approved
Type of
Cover
CB
M
M
M
M
M
M and
CB
M
M
Oklahoma
Alderson Landfill, McAlester, OK
American Environmental, Sand Springs, OK
Broken Arrow Landfill, Broken Arrow, OK
Canadian Valley Landfill, Shawnee, OK
Center Point Landfill, Prague, OK
City of Sallisaw, Sallisaw, OK
East Oak Landfill, Oklahoma City, OK
Muskogee Community Landfill, Muskogee, OK
Newcastle Landfill, Newcastle, OK
Oklahoma Landfill, Oklahoma City, OK
Osage Landfill, Bartlesville, OK
Porter Landfill, Porter, OK
Quarry Landfill, Tulsa, OK
Red Carpet, Meno, OK
Southeast OKC Landfill, Oklahoma City, OK
Southern Plains, Ninnekah, OK
Stillwater Landfill, Stillwater, OK
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
Installed
Installed
Installed
Installed
Approved
Approved
Approved
Approved
Installed
Installed
Design
Installed
Installed
Approved
Installed
Approved
Approved
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
Texas
Caliche Canyon Landfill, Lubbock, TX
City of Corsicana Landfill, Corsicana, TX
City of Fredericksburg Landfill, Fredericksburg, TX
City of Kerrville, Kerrville, TX
City of Lubbock Landfill, Lubbock, TX
City of Snyder Landfill, Snyder, TX
City of Victoria Landfill, Victoria, TX
DFW Recycling Disposal Facility, Lewisville, TX
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
F
F
F
F
F
F
F
F
Proposed
Proposed/
Pending
Proposed/
Pending
Proposed/
Pending
Installed
Proposed
Proposed/
Pending
Proposed/
Pending
M
M
M
M
M
M
M
M
17

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Site
El Centre Landfill, Robstown, TX
Golden Triangle Landfill, Beaumont, TX
Itasca Landfill, Itasca, TX
Mexia Landfill Mexia, TX
Pantex Plant (USDOE), Amarillo, TX
Pleasant Oaks Landfill, Mt. Pleasant, TX
Rio Grande Valley Landfill, Donna, TX
Sierra Blanca, Sierra Blanca, TX
Turkey Creek Landfill, Alvarado, TX
Westside Landfill, Sledo, TX
Program
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
Texas Low
Level Rad
RCRA
RCRA
Type of
Site
MSW
MSW
MSW
MSW
CD
MSW
MSW
Rad
MSW
MSW
Scale
F
F
F
F
F
F
F
Demo
F
F
Status
Proposed/
Pending
Proposed/
Pending
Proposed/
Pending
Proposed//
Pending
Installed
Proposed/
Pending
Proposed/
Pending
Complete
Proposed/
Pending
Installed
Type of
Cover
M
M
M
M
M
M
M
CB
M
M
Region 7
Iowa
Bluestem Landfill Site No. 1, Cedar Rapids, IA
Bluestem Landfill Site No. 2, Cedar Rapids, IA
Grundy County Landfill, Grundy Center, IA
ACAP
ACAP
RCRA
Cleanup
MSW
MSW
MSW
Demo
Demo
Demo
Complete
Complete
Complete
M
M
M
Kansas
Barton County Landfill, Great Bend, KS
Chanute Landfill, Chanute, KS
Coffey County Landfill, Burlington, KS
Holcomb Combustion Waste Landfill, Holcomb, KS
Johnson County Landfill, Shawnee, KS
McPherson County Landfill, McPherson, KS
Seward County Landfill, Liberal, KS
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
MSW
MSW
MSW
IWAsh
MSW
MSW
MSW
F
F
F
F
F
F
F
Installed
Installed
Installed
Proposed
Installed
Installed
Proposed
M
M
M
M
M
M
M
Missouri
Electrical Power Plant, St. Louis, MO
RCRA Solid Waste Unit at Former Wood Treating
Plant, Kansas City, MO
RCRA
RCRA
IWAsh
HWS
Demo
F
Complete
Installed
M
M
Nebraska
Douglas County Recycling and Disposal Facility,
Bennington, NE
Hastings Groundwater Contamination, Hastings, NE
ACAP
CERCLA
MSW
MSW
Demo
F
Complete
Installed
CB
M
Region 8
Colorado
Buffalo Ridge Landfill, Keenesburg, CO
Clear Springs Ranch Ash Monofill, Fountain, CO
Colorado Springs Landfill, Colorado Springs, CO
RCRA
RCRA
RCRA
MSW
IW
MSW
F
F
F
Approved
Approved
Installed
M
M
M
18

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Site
Conservation Services, Inc. Adams County, CO
Custer County Landfill, Westcliffe, CO
Denver Arapahoe Disposal Site, Arapahoe, CO
Fort Carson, Colorado Springs, CO
Kit Carson County Landfill, Burlington, CO
Mesa County Landfill, Grand Junction, CO
Midway Landfill, Fountain, CO
North Weld Landfill, Ault, CO
Rocky Mountain Arsenal (US Army), Denver, CO
Rocky Mountain Arsenal (US Army), Denver, CO
Southside Landfill, Pueblo, CO
West Garfield County Landfill, Rifle, CO
Program
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
DoD
CERCLA
RCRA
RCRA
Type of
Site
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
HWS
HWS
MSW
MSW
Scale
F
F
F
F
F
F
F
F
Demo
F
F
F
Status
Installed
Installed
Installed on
closed cells
Installed
Proposed
Installed
Installed
Installed
Complete
Installed
Approved
Installed
Type of
Cover
M
M
M
M
M
M
M
M
M
CB
M
M
Montana
Allied Waste of Montana, Missoula, MT
City of Billings, Billings, MT
City of Bozeman, Bozeman, MT
City of Butte Landfill, Butte, MT
City of Butte Landfill, Butte, MT
Harve Class II Landfill, Havre, MT
High Plains, Great Falls, MT
Lake County Landfill, Poison, MT
Lake County Landfill Full Scale, Poison, MT
Lewis & Clark County Landfill, Helena, MT
Mr. "M" Landfill, Lewiston, MT
Sanitation, Inc., Lewistown, MT
Unified Disposal District, Havre, MT
Valley County Landfill, Glasgow, MT
Valley View, East Helena, MT
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
ACAP
RCRA
ACAP
RCRA
RCRA
RCRA
RCRA
RCRA
MSW
MSW
MSW
MSW
(old fill)
MSW
(new fill)
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
F
F
F
F
F
F
F
Demo
F
Demo
F
F
F
F
F
Installed
Installed
Installed
Installed
Approved
Proposed
Installed
Complete
Approved
Complete
Installed
Installed
Proposed
Proposed
Installed
M
M
M
M
M
M
M
CB
CB
CB
M
M
M
M
M
North Dakota
Grand Forks Municipal Solid Waste Landfill, Grand
Forks, ND
Great River Energy - Coal Creek Station, Underwood,
ND
RCRA
RCRA
MSW
IWAsh
F
Demo
Approved
Installed
BE
M
South Dakota
Mitchell Landfill, Mitchell, SD
Municipal Sanitary Landfill (Sioux Falls Regional
Municipal Landfill), Hartford, SD
Pierre Landfill, Pierre, SD
RCRA
RCRA
RCRA
MSW
MSW
MSW
F
F
F
Approved
Approved
Installed
M
M
M
Utah
19

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Site
Bayview Landfill, 6 miles N. of Elberta, UT
Chester Class II Landfill, 5 miles north of Ephraim, UT
Emery County Class 1 Landfill, Castle Dale, UT
Hill Air Force Base, Ogden, UT
Monticello Mill Tailings (USDOE), Monticello, UT
Monticello Mill Tailings Repository, Monticello, UT
Mountain View Landfill, Salt Lake City, UT
Sanpete Sanitary Landfill Cooperative White Hills
Class 1 Landfill, Sanpete County, UT
Program
RCRA
RCRA
RCRA
DoD
CERCLA
CERCLA
RCRA
RCRA
Type of
Site
MSW
MSW
MSW
Research
Rad
Rad
CD
Asbestos
MSW
Scale
F
F
F
Demo
Demo
F
F
F
Status
Installed
Installed
Installation
ongoing
Complete
Complete
Installed
Approved
Approved
Type of
Cover
M
M
M
CB
CB
CB
M
M
Region 9
Arizona
Blue Hills Regional Landfill, St. Johns, AZ
Butterfield Station Facility, Mobile, AZ
Cactus Landfill, Florence, AZ
Calmat Avondale Reclamation Landfill, Avondale, AZ
City of Eloy, Eloy, AZ
City of Glendale Municipal Landfill, Glendale, AZ
Cochise County Western Regional Landfill Facility,
Huachuca, AZ
Copper Mountain Landfill, Wellton, AZ
Gray Wolf Regional Landfill, Dewey, AZ
Ironwood Non Municipal Landfill, Florence
Irvington Municipal Landfill, Tucson, AZ
La Paz County Regional Landfill, Parker, AZ
Lone Cactus Landfill, Phoenix, AZ
Los Reales Landfill, Tucson, AZ
Northwest Regional Landfill, Surprise, AZ
Painted Desert Landfill, Joseph City, AZ
Silver Bar Mine Regional Landfill, Florence, AZ
Southwest Regional Solid Waste Landfill, Buckeye, AZ
Speedway Construction Debris Landfill, Tucson, AZ
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
MSW
MSW
MSW
CD
MSW
MSW
MSW
MSW
MSW
CD
MSW/
CD
MSW
CD
MSW
MSW
MSW
MSW
MSW
CD
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
Proposed
Approved
Approved
Approved
Approved
Approved
Approved
Approved
Approved
Approved
Installed
Approved
Approved
Approved
Approved
Approved
Approved
Approved
Approved
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
California
Allied Imperial Landfill, Imperial, CA
Altamont Landfill & Resource Recovery Facility,
Livermore, CA
Altamont Landfill Closure, Livermore CA
Anza Sanitary Landfill, Anza, CA
Apple Valley Landfill, Apple Valley, CA
Apple Valley Landfill, Apple Valley, CA
Azusa Landfill, Azusa, CA
Bakersfield Sanitary Landfill, Bakersfield, CA
RCRA
ACAP
RCRA
RCRA
ACAP
RCRA
RCRA
RCRA
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
F
Demo
F
F
Demo
F
F
F
Installed
Complete
Conditional-
ly Approved
Installed
Complete
Installed
Proposed
Installed
M
M
M
M
Varies
M
M
M
20

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Site
Benton Class III Landfill, Benton, CA
Bishops Canyon Landfill, Los Angeles, CA
Bradley Landfill, Los Angeles, CA
Burbank Landfill No. 3, Burbank, CA
Buttonwillow Landfill, Kern County
California Valley Landfill, California Valley, CA
Camp Pendleton Marine Corps Base, San Diego
County, CA
Cedarville (East) Landfill, Cedarville, CA
Chalfant Class III Landfill, Mono County, CA
China Grade Sanitary Landfill, Bakersfield, CA
Coachella Sanitary Landfill, Coachella, CA
Eagleville Landfill, Modoc County, CA
Edom Hill Sanitary Landfill, Riverside County, CA
Edwards Air Force Base Operable Unit 7 Chemical
Warfare Materiel, Lancaster, CA
El Toro Marine Corps Air Station, El Toro, CA
Forward Landfill, Manteca, CA
Foxen Canyon Closed Class III Landfill, San Luis
Obispo, CA
Frank R. Bowerman Landfill, Irvine, CA
Gaffey Street Sanitary Landfill, Wilmington, CA
Hesperia Landfill, Hesperia, CA
Hirschdale Landfill, Hirschdale, CA
Holtville Sanitary Landfill, Holtville, CA
Jolon Road Closed Class III Landfill, King City, CA
Kettleman Hills Facility, Kettleman City, CA
Kiefer Landfill, Sloughhouse, CA
Kiefer Class III Municipal Landfill, Sloughhouse, CA
Lake City Landfill, Lake City, CA
Lamb Canyon Sanitary Landfill, Beaumont, CA
Lenwood-Hinkley Landfill, Lenwood, CA
Lopez Canyon Sanitary Landfill, Los Angeles, CA
Marine Corps Base Barstow, CA
Mead Valley Sanitary Landfill, Perris, CA
Midway Solid Waste Disposal Site, San Luis Obispo
County, CA
Milliken Landfill, Ontario, CA
Milliken Landfill, Ontario, CA
Monterey Peninsula Landfill, Marina, CA
Program
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
CERCLA
CERCLA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
RCRA
ACAP
RCRA
RCRA
RCRA
RCRA
RCRA
CERCLA
RCRA
RCRA
RCRA
RCRA
ACAP
Type of
Site
MSW
MSW/
CD
MSW
MSW
MSW
MSW
MSW/
CAMU
MSW
MSW
MSW
MSW
MSW
MSW
HW/
MSW
HW/
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
HW/
MSW
MSW
MSW
MSW
MSW
MSW
MSW
HW/
MSW
MSW
IW
MSW
MSW
MSW
Scale
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
Demo
F
F
F
F
F
F
F
F
Demo
F
Demo
Status
Installed
Installed
Installed
Design
Approved
Installed
Installed
Installed
Installed
Installed
Installed
Installed
Installed
Installed
Installed
Installed
Approved
Approved
Installed
Installed
Installed
Proposed
Installed
Proposed
Complete
Approved
Installed
Proposed
Installed
Installed
Installed
Installed
Installed
Complete
Installed
Complete
Type of
Cover
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
21

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Site
Needles Sanitary Landfill, Needles, CA
Newberry Springs Sanitary Landfill, Newberry Springs,
CA
Norton Air Force Base (Landfill #2), San Bernardino,
CA
Ocotillo Class III Municipal Solid Waste Management
Facility, Ocotillo, CA
Operating Industries Inc. Landfill, Monterey Park, CA
Phelan Landfill, Phelan, CA
Phelan Landfill Full Scale, Phelan, CA
San Marcos Landfill, San Marcos, CA
Spadra Landfill, Pomona, CA
Twentynine Palms Sanitary Landfill
U.S. Marine Corps Air and Ground Combat Center
(MCAGCC) at Twentynine Palms, Twentynine Palms, CA
Yucaipa Landfill, Yucaipa, CA
Program
RCRA
RCRA
CERCLA
RCRA
RCRA
ACAP
RCRA
RCRA
RCRA
RCRA
DoD
RCRA
Type of
Site
MSW
MSW
MSW
MSW
HW/
MSW
MSW
MSW
MSW
MSW
MSW
MSW
MSW
Scale
F
F
F
F
F
Demo
F
F
F
F
Demo
F
Status
Installed
Installed
Installed
Installed
Installed
Complete
Approved
Installed
Installed
Installed
Complete
Installed
Type of
Cover
M
M
M
M
M
M
M
M
M
M
M
M
Hawaii
Kaneohe Bay Marine Corps Base, Oahu, HI
DoD
MSW
Demo
Complete
BE
Nevada
Nevada Test Site, NV (landfill U-3 ax/bl)
New Austin Landfill, Austin, NV
U.S. Ecology Nevada Site, Beatty, NV
DOE
Research
RCRA
RCRA
Rad
MSW
HW
Demo
F
F
Complete
Proposed
Approved
M
M
M
Region 10
Alaska
Anchorage Pilot Study Site, Anchorage. AK
City of Elim Landfill, Elim, AK
Elmendorf Air Force Base, Anchorage, AK
Minchumina Landfill, Lake Minchumina, AK
RCRA
RCRA
RCRA
RCRA
MSW
MSW
MSW
MSW
Demo
F
F
F
Complete
Proposed
Installed
Proposed
M
M
M
M
Idaho
Idaho National Engineering Laboratory, Idaho Falls, ID
CERCLA
HWS
F
Installed
CB
Oregon
Finley Buttes Regional Landfill, Boardman, OR
ACAP
MSW
Demo
Complete
M
Washington
Duvall Custodial Landfill
Hanford 200-Area (USDOE), Richland, WA Prototype
Barrier (BP-1)
Nonradioactive Dangerous Waste Solid Waste Landfill
(DOE Hanford)
RCRA
CERCLA
CERCLA
MSW
Rad
HWS
F
Demo
F
Installed
Installed
Proposed
M
CB
M
22

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Definitions
Approved       A proposal to build an ET has been approved by the appropriate regulatory agency.
Complete       Associated with demonstrations and indicates the demonstration is complete.
Proposed       An ET design or proposal to construct an ET has been submitted to the appropriate regulatory agency
Installed        Construction complete.

Legend
ACAP          Alternative Cover Assessment Program
BE             Bioengineered
CAMU          Corrective Action Management Unit
CB             Capillary Break
CD             Construction Debris Landfill
CERCLA       Comprehensive Environmental Response, Compensation, and Liability Act
Demo          Demonstration Project
F              Full Scale
HW            RCRA Subtitle C Hazardous Waste Facility
HWS           Hazardous Waste Site—Generally concerned with cleanup activities
IW             Industrial Waste Such as Coal Ash
M              Monolithic
MSW          Municipal Solid Waste Site
MSW/CAMU    MSW being used in a RCRA cleanup to consolidate potentially hazardous wastes
NHWS         Non-Hazardous Waste Site
NRC           Nuclear Regulatory Commission
Rad            Radioactive Waste
RCRA          Resource Conservation and Recovery Act
                                                 23

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        B
24

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ALTERNATIVE LANDFILL COVER DEMONSTRATION (ALCD)

DOE sponsored the ALCD, a large-scale field test of two conventional designs (RCRA Subtitle C and Sub-
title D) and four alternative landfill covers (monolithic ET cover, capillary barrier ET cover, geosynthetic clay
liner cover, and anisotropic [layered capillary barrier] ET cover). The test was conducted at Sandia National
Laboratories, located on Kirtland Air Force Base in Albuquerque, New Mexico. Cover design information is
available at http://www.sandia.qov/Subsurface/factshts/ert/alcd.pdf.

The ALCD collected information on construction, cost, and performance that is needed to compare alter-
native cover designs with  conventional covers. The RCRA covers were constructed in  1995, and the  ET
covers were constructed in 1996. All of the covers were 43 feet wide by 328 feet long and were seeded with
native vegetation. The purpose of the project was to use the performance data to help demonstrate equiva-
lency and refine numerical models to more accurately predict cover system performance (Dwyer2003).

The ALCD collected data on percolation using a pan  lysimeter and soil moisture to monitor cover perfor-
mance. Total precipitation  (precip.) and percolation (perc.)  volumes based on 5 years of data are provided
below. The ET covers generally have less percolation than  the Subtitle D cover for each year shown  below.
More information on the ALCD cover performance can be found in Dwyer2003.

Monolithic
ET
Capillary
Barrier ET
Anisotropic
(layered
capillary
barrier) ET
Geosynthetic
Clay Liner
Subtitle C
Subtitle D
1997
( May 1 -Dec 31)
Precip.
(mm)
267.00
267.00
267.00
267.00
267.00
267.00
Perc.
(mm)
0.08
0.54
0.05
0.51
0.04
3.56
1998
Precip.
(mm)
291.98
291.98
291.98
291.98
291.98
291.98
Perc.
(mm)
0.22
0.41
0.07
0.19
0.15
2.48
1999
Precip.
(mm)
225.23
225.23
225.23
225.23
225.23
225.23
Perc.
(mm)
0.01
0.00
0.14
2.15
0.02
1.56
2000
Precip.
(mm)
299.92
299.92
299.92
299.92
299.92
299.92
Perc.
(mm)
0.00
0.00
0.00
0.00
0.00
0.00
2001
Precip.
(mm)
254.01
254.01
254.01
254.01
254.01
254.01
Perc.
(mm)
0.00
0.00
0.00
0.02
0.00
0.00
2002
(Jan 1-Jun 25)
Precip.
(mm)
144.32
144.32
144.32
144.32
144.32
144.32
Perc.
(mm)
0.00
0.00
0.00
0.00
0.00
0.74
                                             25

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ALTERNATIVE COVER ASSESSMENT PROGRAM (ACAP)

EPA conducted the ACAP to evaluate the performance of alternative landfill covers. The ACAP began in
1998, and cover performance was evaluated at 13 sites. The sites were located in eight states from Califor-
nia to Ohio and Georgia, and included a variety of landfill types, such as MSW, construction and demolition
waste, and hazardous waste landfills. At eight sites, conventional and ET covers were tested side by side.
At the remaining five sites, only ET covers were tested.

The  alternative covers typically were constructed with local soils and native  vegetation. At two facilities,
however, hybrid poplar trees were used as vegetation. Percolation performance was evaluated by  pan lysim-
eters. Soil moisture also was evaluated at all sites. Below are the field data for precipitation and percolation
volumes at 11 of the sites. A summary of field cover performance for all 13 sites through 2004 is provided
in Albright and Benson (2005). More information about ACAP is available  on the Desert Research Institute
website at http://www.dri.edu/acap-research.
ACAP Water Balance Results
Site Location
Altamont CA
Apple Valley CA
Cedar Rapids
IA
Cover Design
ET
Membrane
Composite
ET
Membrane
Composite
Compacted
Clay
ET
Compacted
Clay
Membrane
Composite
Data Year
(days)
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
Precipitation
(mm)
287
425
291
Annual Average
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
287
425
291
Annual Average
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
86
106
Annual Average
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
86
106
Annual Average
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
86
106
Annual Average
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
784
1742
Annual Average
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
784
1742
Annual Average
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
784
1742
Annual Average
Drainage
mm
1.5
2.5
64.5
22.8
0.0
4.0
0.2
1.4
0.4
0.0
0.2
0.0
0.0
0.0
0.0
0.2
0.1
157.1
365.7
261.4
94
171
132.5
22.0
62.2
42.1
As % of Precipitation
0.52%
0.59%
22.16%
7.76%
0.00%
0.94%
0.07%
0.34%
0.47%
0.00%
0.24%
0.00%
0.00%
0.00%
0.00%
0.19%
0.1%
20.0%
20.99%
20.5%
11.98%
9.82%
10.9%
2.81%
3.57%
3.19%
                                              26

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ACAP Water Balance Results
Site Location
Omaha NB
Boardman OR
Sacramento CA
Cover Design
Thin ET with
Capillary Break
Thick ET with
Capillary Break
Membrane
Composite
ETThin
ET Thick
Membrane
Composite
ETThin
ET Thick
Data Year
(days)
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
Precipitation
(mm)
560
475
511
Annual Average
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
560
475
511
Annual Average
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
560
475
511
Annual Average
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
164
185
177
Annual Average
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
164
185
177
Annual Average
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
164
185
177
Annual Average
7/1/00-6/30/01 (365)
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
379
456
426
159
Annual Average
7/1/00-6/30/01 (365)
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
379
456
426
159
Annual Average
Drainage
mm
3.45
50.9
68.5
40.95
4.16
28.7
16.3
16.4
1.03
9.15
10.9
7.03
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.4
96.2
3.9
108.4
52.48
0.0
8.5
0.0
0.6
2.28
As % of Precipitation
0.62%
10.72%
13.41%
8.25%
.74%
6.04%
3.19%
3.32%
0.18%
1.93%
2.13%
1.41%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.37%
21.10%
0.92%
68.18%
22.64%
0.00%
1.86%
0.00%
0.38%
0.56%
27

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ACAP Water Balance Results
Site Location
Poison MT
Helena MT
Albany GA
Marina CA
Monticello UT
Cover Design
ET with
Capillary Break
Membrane
Composite
ET with
Capillary Break
ET (Trees)
Compacted
Clay
ET with
Capillary Break
ET with
Capillary Break
Data Year
(days)
7/1/00-6/30/01 (365)
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
Precipitation
(mm)
358
308
326
254
Annual Average
7/1/00-6/30/01 (365)
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
358
308
326
254
Annual Average
7/1/00-6/30/01 (365)
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
252
314
288
103
Annual Average
7/1/00-6/30/01 (365)
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
1079*
1039*
1457*
Annual Average
7/1/00-6/30/01 (365)
7/1/01 -6/30/02(365)
909
996
Annual Average
7/1/00-6/30/01 (365)
7/1/01 -6/30/02(365)
7/1/02-6/24/03(359)
492
401
467
Annual Average
7/1/00-6/30/01 (365)
7/1/01 -6/30/02(365)
7/1/02-6/24/03(359)
492
401
467
Annual Average
8/12/00-6/30/01 (323)
7/1/01 -6/30/02(365)
7/1/02-6/30/03(365)
7/1/03 -6/30/04 (365)
393
213
342
315
Annual Average
Drainage
mm
0.18
0.39
0.19
0.20
0.24
1.16
0.0
0.0
0.5
0.42
0.0
0.0
0.0
0.0
0.0
134
3.1
218.2
118.4
291.9
237.6
264.8
44.7
64.2
51.1
53.3
9.0
25.0
36.0
23.3
0.0
0.0
0.0
0.1
0.03
As % of Precipitation
0.05%
0.13%
0.06%
0.08%
0.08%
0.32%
0.00%
0.00%
0.20%
0.13%
0.00%
0.00%
0.00%
0.00%
0.00%
12.42%
0.3%
14.98%
9.23%
32.11%
23.86%
27.98%
9.09%
16.01%
10.94%
12.01%
1.82%
6.23%
7.71%
5.25%
0.00%
0.00%
0.00%
0.03%
0.008%
*Precipitation values at Albany include irrigation of the ET cover test section.
Source: Albright and Benson 2005
28

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