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United States
Environmental Protection
Agency
S/TE Technology Capsule
MatCon™ Modified Asphalt for
Waste Containment
Abstract
As part of the Superfund Innovative Technology
Evaluation (SITE) Program, the U.S. Environmental
Protection Agency (EPA) evaluated the use of a
proprietary asphalt mixture as a cover for hazardous
waste landfills or other land disposal sites. Wilder
Construction Company (WCC), the firm that
developed the asphalt mixture called MatCon™,
claims that its asphalt has a permeability of about
1x10* centimeters per second (cm/sec) and is
flexible enough that it does not crack under the
small amounts of differential settlement typically
encountered in hazardous waste landfills. Potential
sites for application of this technology include
hazardous waste sites that are relatively level and
have a firm base. The use of MatCon™ asphalt as a
site cover allows reuse of the site for public
recreation or light industrial purposes.
Two MatCon™1 asphalt covers have recently been
installed for evaluation at two sites. The primary
evaluation site is the Lindane Source Area (ISA) in
the west management unit of Dover Air Force Base
(DAFB) in Dover, Delaware. The second evaluation
site is the Tri-County Landfill (TCL), located in Elgin,
Illinois.
A pilot-scale MatCon™ cover (0.35 acre) was
installed at the DAFB site in April 1999 together with
an adjacent conventional asphalt cover for
comparative testing. Samples of both the MatCon™
and conventional asphalt covers were obtained in
August 1999 for extensive laboratory testing. A 3.6-
acre MatCon™ cover was installed at the TCL site in
November 1999, and samples were obtained
immediately following installation for laboratory
permeability testing.
Preliminary laboratory testing results indicate that
the permeability of the MatCon™ cover at the DAFB
site is less than 1.0x10* cm/sec, whereas the
permeability of the adjacent conventional asphalt
cover is between 2.7X10-4 cm/sec and 1.0x1Q-5 cm/
sec. Flexural tests of samples of the MatCon™ and
the conventional asphalt covers indicate that the
MatCon™ cover tolerates three times more
deflection without cracking compared to the
conventional asphalt cover. Field hydrologic data
obtained to date at the DAFB and TCL sites indicate
average field permeabilities of about 2.3x108 cm/
sec and 5.0x10 •" cm/sec, respectively. Complete
data from the field permeability testing are
available in the Technology Evaluation Report.
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12tft Floor
Chicago, IL 60604-3590
Recycled/Recyclable
Printed with vegetable-based ink on
paper that contains a minimum of
50% post-consumer fiber content
processed chlorine free
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Introduction
The SITE Program was established in 1986 to
accelerate the development, evaluation, and use of
innovative technologies that offer permanent
cleanup alternatives for hazardous waste sites. One
component of the SITE Program is the Demonstration
Program, under which engineering, performance,
and cost data are developed for innovative
technologies. Data developed under the SITE
Demonstration Program enable potential users to
evaluate each technology's applicability to specific
waste sites.
MatCon™ is an asphalt mixture produced by using a
proprietary binder and a specified aggregate
gradation in a conventional hot-mix asphalt plant.
WCC claims that MatCon™ asphalt is much less
permeable and possesses superior flexural strength
compared to conventional asphalt. WCC specifically
claims that MatCon™ asphalt has a permeability of
1.0x10^ cm/sec or less, which exceeds the
requirement of less than 1.0x1Q-7 cm/sec
established for Resource Conservation and Recovery
Act (RCRA) Subtitle C hazardous waste landfill
covers (Title 40 of the Code of Federal Regulations,
Section 264.301).
The two primary objectives of the SITE Program
evaluation of the MatCon™ technology were to
compare (1) the in-field permeability of the
MatCon™ cover to the RCRA requirement of less than
1.0x1fr7 cm/sec, and (2) the permeability and
flexural properties of MatCon™ asphalt to those of
conventional hot-mix asphalt. Secondary objectives
of the evaluation were to (1) compare various
laboratory-measured physical characteristics
(including load capaa'ty/deformation, shear strength,
joint permeability, and aging and degradation
characteristics) of MatCon™ asphalt to those of
conventional asphalt covers; (2) assess the field
performance of the MatCon™ cover under extreme
weather conditions and vehicle loads; (3) estimate a
cumulative hydrologic balance for the MatCon™
cover at the DAFB site; and (4) estimate the costs of
MatCon™ cover installation.
Dover Air Force Base Site
WCC installed a pilot-scale cover system at the DAFB
site in April 1999 for purposes of evaluating the
MatCon™ technology. The evaluation cover
measures approximately 124 by 220 feet and
consists of three sections: (1) 12-inch-thick
MatCon™ asphalt with a drainage layer (Section I),
(2) 4-inch-thick MatCon™ asphalt (Section II), and
(3) 4-inch-thick conventional asphalt (Section III).
The drainage layer in Section I was constructed as a
4-inch-thick channel of open-graded asphalt
between two 4-inch-thick MatCon™ layers, as shown
in Figures 1 and 2. The purpose of this drainage layer
was to collect and allow measurement of the water
that infiltrated through the top 4 inches of the
cover. The purpose of constructing both
conventional asphalt and MatCon™ sections was to
allow a direct comparison of the physical properties
of each type of asphalt based on laboratory testing
of cover samples.
To monitor infiltration, the four 3-inch-diameter
polyvinyl chloride pipes leading from the drainage
layer in Section I were connected to a 10-inch-
diameter sump, as shown in Figure 1. During the
field evaluation, the volume of infiltration water
collected in the sump was monitored during rainfall
events, and Darcy's Law was used to estimate the in-
field permeability of the MatCon™ cover.
To monitor surface runoff, a lined ditch was
constructed downgradient from the cover, and
berms were constructed to direct the runoff from
Section I of the cover into the drainage ditch.
Surface runoff was measured continuously with a
flow meter, which recorded both instantaneous and
cumulative flow.
Tri-County Landfill Site
WCC installed a 3.6-acre MatCon™ cover at the TCL
site in Elgin, Illinois during November 1999. A plan
view of the test section of the cover is shown in
Figure 3. The drainage system underneath the test
section incorporates an intermediate gravel layer
underlain by an impermeable geomembrane, as
shown in Figure 4. This configuration was requested
by the U.S. Army Corps of Engineers, the agency
providing oversight of the TCL closure.
A sump was installed at the edge of the MatCon™
cover at this site to collect the drainage from the
gravel layer. The surnp is similar in construction to
that installed at the Dover site and was used to
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Figure 1. Plan view of Section 1 of the evaluation cover system at Dover Air Force Base.
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LEGEND
Open Graded Asphalt
Dense MatCon™ Asphalt
Figure 2. Section A - A' (from Figure 1) showing infiltration collection system at Dover Air Force Base.
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3-Inch Diameter
Perforated PE Pipe
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MatCon™ Asphalt with
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Non-P
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MatCon™ Asphalt
Figure 3. Plan view of the test section of the cover system at Tri-County Landfill.
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MatConn Asphalt
NOT TO SCALE
3-inch Diameter Perforated PE Pipe
T ronsttiofiirtQ to
Non-Perforated PE Pipe
Coarse Aggregate Backfill
(IxKHcmfe)
16 oz. Geotextile
40 Mil LLDPE Geomembrane
MatCon« Asphalt
Prepared Coarse Aggregate
Base Course
Figure 4. Section B - B' (from Figure 3) showing infiltration collection system at Tri-County Landfill.
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assess the volume of infiltration water. However, a
system for collection and measurement of surface
runoff was not installed at this site.
Evaluation Results
Both MatCon™ and conventional asphalt cover core
samples were obtained from the DAFB site in August
1999; these samples were subjected to extensive
laboratory testing of physical properties. On
November 8, 1999, eight core samples were
obtained from the MatCon™ cover at the TCL site in
areas adjacent to the test section; these samples
were subjected to permeability testing for purposes
of comparison to the testing results for the DAFB site
samples.
This section summarizes the results of the
laboratory testing of the cover samples and of in-
field observations as they relate to the primary and
secondary objectives. Field permeability data and
the hydrologic balance for the MatCon™ cover at the
Dover site will be available in July 2000.
Comparison With RCRA Requirements
Field permeability tests on the 12-inch-thick
MatCon™ cover at DAFB site and the MatCon™cover
at the TCL site show that the permeability is
between 1.28x107 and 5.15x1010 cm/sec. This
permeability is up to three orders of magnitude
better than the RCRA requirement for Subtitle C
landfill covers of 1.0x10'7 cm/sec.
Comparison with Conventional Asphalt -
Permeability and Flexure
Laboratory test results for the MatCon™ and
conventional asphalt covers are presented in Table
1. The permeability of the conventional asphalt
cover samples ranged from 2.7x10"* cm/sec to
1 .Oxlfr5 cm/sec, whereas all the MatCon™ samples
showed permeabilities of less than 1.0x1 fr8 cm/sec.
The flexural properties of the conventional asphalt
and the MatCon™ covers were measured using a
special test developed for this evaluation. The test
measures the flexural properties under simulated
differential settlement using a 40-inch-long by 4-
inch-square slab sample. The sample sags under its
own weight when it is subjected to differential
settlement by removing the sand supporting the slab
through an aperture about mid-point along the
sample length. The sand is removed over a 30-day
period in incremental, predetermined quantities.
The flexural tests of the MatCon™ cover samples
indicate that a 36-inch beam showed 20.41 mm of
deflection without cracking, whereas conventional
asphalt cracked with 7.2 mm of deflection. Further,
the MatCon™ cover sample did not show any cracks
after 30 days, whereas the conventional asphalt
sample had cracks up to 3 mm wide and 2.5 cm long
at 31.25 mm of deflection.
Comparison with Conventional Asphalt
Performance
Other physical properties that were measured to
compare conventional and MatCon™ asphalt covers
included the following:
• Joint integrity
• Load capacity and deformation
• Tensile strength
• Thermal crack resistance
• Aging and degradation
• Void space
Table 1 summarizes the properties obtained for
MatCon™ and conventional asphalt.
Field Performance of MatCon™
Extreme Weather Conditions
Under
The field performance of MatCon™ under freeze-
thaw and vehicle loads was evaluated at the TCL
site. Since installation in November 1999, several
snow storms occurred at the TCL site. In early
March, a thawing period of about 1 week was
followed by cold weather and a snow storm.
Because the cover could not be completed in 1 day,
it was necessary to complete "cold joints" after the
edges of the daily applications cooled overnight. It
is often difficult to bond and compact the asphalt
properly at a cold joint. Poor workmanship at these
cold joints caused raveling, or separation of
aggregate particles, from the edge and surface of
the compacted asphalt during cold weather. A
surficial crack was found at one location on the
MatCon™ cover. WCC repaired the crack by routing
the joint, cleaning the joint using a hot air lance,
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Table 1. Comparison of Average Physical Properties of MatCon™ and Conventional Asphalt Covers
Property
Test Method
MatCon™
Conventional Asphalt
Hydraulic Permeability ASTM D-5084
(cm/sec)
Flexural Properties at New Method1
Center of Beam
Joint Integrity
Load Capacity and
Deformation at-20°C
(MegaPascals)
Tensile Strength at
-20°C
(MegaPascals)
Thermal Crack
Resistance at-30°C
(MegaPascals)
Accelerated
Weathering (60 days)
(cm/sec)
Fuel Resistance
(Depth of Penetration,
cm)
Void Space (%)
Hydraulic
Transmissivity
(drainage layer only)
(cm/sec)
ASTM D-5084
ASTM D-4123
AASHTO TP-9
AASHTO TP-10
ASTM D-5084
ASTM 1856
ASTM D-3203
ASTM D-5084
< 1.0x 10-8
20.41
No cracking
5.47x10-5
2048
3.55
3.60
2.2x10-6
1.5
1.53
8. 94x1 0-3
2.7x10-* to 1.0x10-5
31.252
(3-mm-wide, 2.5-cm-
long cracks)
1.04x10-4
3200
2.58
2.70
3.15x10-*
5.5
10.53
Notes:
AASHTO
ASTM
Method developed by Ronald Terrel of WCC
Cracking was initiated at 7.2 mm of deflection
American Association of State Highway and Transportation Officials
American Society for Testing and Materials
and extruding it full of hot modified asphalt mastic
joint sealer. Permeability measured from the
sample obtained from the location containing the
crack was 3.56x105 cm/sec, demonstrating the
critical importance of quality assurance and quality
control (QA/QC) in installing the MatCon™ cover.
The QA/QC requirements for MatCon™ cover
installation will be detailed in the Innovative
Technology Evaluation Report (ITER).
The other areas of the 3.6-acre MatCon™ cover
appear to be performing well under the heavy
vehicle loads. Heavy trucks from Waste
Management's recycling fleet have been operating
on the MatCon™ cover since it was installed. The
trucks are parked on the MatCon™ cover, and the
cover is performing well under oil leaks from the
trucks.
Cost Estimate for MatCon™ Covers
The MatCon™ cover installation involves the mixing
of the proprietary binder along with aggregates in an
asphalt plant, placing the asphalt mixture on the
prepared surface, and compacting it. The costs
provided by WCC per acre of MatCon™ cover are
summarized below.
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Aggregates
MatCon™ Binder
Mix Preparation
Transport to Site
Lay and
Compact Mixture
Permitting
Site Preparation
Total
$10,000
$77,000
$9,000
$8,000
$16,000
$2,000
$10.000
$120,000
This cost compares favorably with the cost per acre
for RCRA Subtitle C covers, which range from
$150,000 to $300,000 per acre, depending on local
availability of appropriate soil cover materials.
Comparison to Superfund Feasibility Study
Evaluation Criteria
Table 2 summarizes the MatCon™ cover performance
compared to the Superfund feasibility study
evaluation criteria. This table is provided to assist
Superfund decision-makers in considering the
MatCon™ cover for remediation at hazardous waste
sites.
Technology Status
The MatCon™ technology is commercially available,
and WCC has been discussing with several site
owners the potential application of the technology.
The MatCon™ technology is being specifically
considered for several other landfill closures. In
2003, MatCon™ covers over landfills in Beaumont,
Texas and Albuquerque, New Mexico may be
evaluated under the SITE program.
Technology Applicability
The MatCon™ technology is applicable as a final
cover at many hazardous waste sites. A MatCon™
cover can be constructed within a few days using
conventional asphalt paving equipment. Maintenance
of the cover is relatively easy, using conventional
asphalt paving repair equipment and materials. The
potential for hazardous waste site reuse is a major
advantage of this technology. Uses being planned
for the MatCon™ cover include the following:
staging area for heavy equipment and vehicles; light
industrial manufacturing; and sports facilities, such
as tennis courts and tracks.
Limitations
The technology is difficult to implement at waste
sites that are steep and have an unstable surface
because the MatCon™ cover requires a firm
subgrade for placement of the cover. Waste sites
must have slopes less then 3:1 for the safe use of
compacting and paving equipment.
Sources of Further Information
Future field data from the hydrologic monitoring at
the DAFB and TCL sites will be used to continue the
evaluation of in-field permeability of the cover.
Observations at the TCL site will continue to provide
data on field performance of the MatCon™ cover
under extreme weather conditions and heavy
vehicle loads.
Further details regarding the technology are
available from the following sources:
David Carson
U.S. Environmental Protection Agency
ORD/NRMRL
5995 Center Hill Avenue
Cincinnati, OH 45224
Phone: 513-569-7527
Fax: 513-569-7879
carson. david@epamaH. epa.gov
Karl Yost
Wilder Construction Company
1525 E. Marine View Drive
Everett, WA 98201
Phone: 425-551-3100
Fax:425-551-3116
karlyost@wilderconstruction.com
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Table 2. Superf und Feasibility Evaluation Criteria for the MatCon™ Technology
Criterion
Discussion
Overall protection of
human health and the
environment
Compliance with 2
applicable or relevant and
appropriate requirements
(ARAR)
Long4erm effectiveness 3.
and permanence
Reduction of toxicity,
mobility, or volume
through treatment
Short-term effectiveness
Implementability
4.
Cost
State acceptance
7.
8.
Community acceptance 9.
The MatCon™ technology is expected to protect human
health by containing the hazardous waste. It affords
environmental protection by preventing the formation of
leachate at hazardous waste landfills.
The MatCon™ technology complies with the EPA
permeability requirement of 10* cm/sec for landfill
covers that do not have bottom geomembrane layers. It
also complies with the state and local ARARs.
According to WCC, the MatCon™ cover can be a
permanent containment system requiring limited routine
maintenance.
The technology reduces the mobility of contaminants by
minimizing the entry of water into the waste.
The technology can be implemented expeditiously and
is effective in reducing water infiltration into the waste.
The technology is readily implementable since hot-mix
plants are available in all parts of the country. Standard,
readily available paving equipment can be used to
construct the MatCon™ cover.
The technology uses natural materials (aggregates and
petroleum products) that are used extensively in the
construction industry.
The cost is comparable to RCRA Subtitle C day and
geosynthetic covers.
State acceptance of the technology is likely because of
the redevelopment possibilities with a MatCon™ cover.
Illinois, Texas, California, and Florida have accepted this
cover.
Community acceptance of the technology is likely
because of the redevelopment possibilities with a
MatCon™ cover.
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