TM 5-814-7
(a) A test method accepted by the EPA for
does not dry out. Controlled moisture application or
evaluating waste/liner compatibility involves exposing a
coating the liner with an asphaltic emulsion may be
liner sample to the waste or leachate encountered at the
required in some instances to prevent drying and
facility. After exposure, the liner sample is tested for
cracking. Protection from freezing is also an important
strength (tensile, tear, and puncture) and weight loss.
consideration in colder climates.
Any significant deterioration in the measured properties
(2) Considerations in installation of a synthetic
is considered evidence of incompatibility, unless it can be
membrane liner include providing protective soil layers
demonstrated that the deterioration exhibited will not
above and below the liner and proper seaming of the
impair the integrity of the liner over the life of the facility.
liner. Failure to consider these important factors could
(b) Standard
specifications
for
flexible
result in liner failure and undermine the goal of complete
membrane liners are currently being developed by the
waste containment. To ensure proper membrane liner
National Sanitation Foundation (NSF). Upon their final
placement, seaming, and placement of protective soil
adoption, these standards will be used by the EPA to
cover, the best installation procedures and practices
provide minimum recommendations on physical
should be developed for the type of membrane
properties, construction practices and seaming. In the
proposed. Guidance in installing synthetic liners should
interim, the design engineer may review suggested
be obtained from experienced manufacturers of the
standards in appendix IX of EPA SW-870.
membrane, fabricators who have assisted in preparing
g. Liner installation. Whether the liner to be
panel installation plans and have fabricated large panels
installed is soil or synthetic material, a thorough analysis
of the materials, and experienced contractors. Project
of the proposed liner foundation is necessary to ensure
specifications for the installation of the liner should state
adequate support of the liner and resistance to pressure
the experience required for the manufacturer, the
gradients above or below the liner. An unsuitable
fabricator and the installing contractor for the project.
foundation could result in settlement, compression, or
(a) Protection of the liner involves proper
uplift of the liner which could lead to liner damage. An
preparation of the subgrade and placement of protective
analysis of foundation suitability may include evaluation
soil layers. Procedures to be used in preparation of the
of geologic, hydrologic, geotechnical and other pertinent
surface include compaction, scraping and rolling to
data. Such data are particularly important in the design
provide a smooth surface for the liner. A minimum 6inch
of surface impoundments. Specific requirements for
layer of material not coarser than sand (classified by
installation of soil liners and flexible membranes are
USCS as SP or SW, with less than 5 percent passing the
discussed below.
No. 100 sieve) is recommended by the EPA as a
(1) Proper installation of a soil liner is needed
protection against puncture, equipment damage, and
to maintain the specified permeability of 1 x 10-7 cm/sec
exposure to the elements; sands which act as filters
or less. Prior to placement of the clay liner, the subbase
must meet filter graduation requirements, such as those
must be properly prepared to ensure structural integrity
shown in chapter 5 of TM 5-820-2. Note, however, that
and proper bonding with the clay liner. To ensure
the EPA draft guidance document for liners permits
adequate compaction, soil materials should be spread in
substitution of drainage layers, on-site soils or soil liners
loose lifts no more than 6 inches thick, be wetted or dried
for the 6-inch sand layer.
to the specified moisture content of optimum or above,
(b) In surface impoundments, the liquid
and be compacted with a sheepsfoot-type roller to the
material overlying the liner is considered sufficient
specified relative compaction. Specified values must be
protection unless dredging or operation of other
based upon the tested relationships between moisture
equipment could damage the liner. If so, an 18-inch
content, relative compaction and permeability. See
layer of soil is recommended. Sterilization of any
figure 6-4.
underlying organic materials may be necessary,
(a) Successive lifts should be placed and
particularly in the case of surface impoundments, to
compacted until a liner thickness of 3 feet is achieved.
prevent formation of gases and subsequent uplift of the
The finished surface of the soil liner should then be rolled
liner. In cold climates, the use of a protective soil cover
or bladed smooth. Installation of a clay liner should not
may be necessary to minimize the possibility of cracking
be attempted under adverse weather conditions, such as
caused by freezing.
heavy precipitation or freezing temperatures.
(c) Heavy geotextile fabrics (>a 400 g/m2) are
(b) Following installation, the liner should be
increasingly being used in combination with flexible
inspected for imperfections, such as lenses, cracks, or
membrane liners in hazardous waste units to protect the
other structural defects which could cause an increase in
membranes from puncture and abrasion. In surface
liner permeability. Until placement of waste or, in the
impoundments, geotextiles are also used for gas relief
case of a double-lined facility, the overlying synthetic
beneath membranes (Collins and Newkirk, 1982). In
liner, care must be taken to ensure that the liner
addition, geotextiles may also serve as a clean base for
seaming membrane panels. If geotex-
6-9
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