priate coatings would be a suitable liner in such cases.
disadvantages. While soil liners are suitable for use as
(b) Waste piles storing only dry wastes which
secondary liners and, in certain applications, as the only
will not generate leachate through decomposition or
liner, synthetic membrane liners are considered by the
reaction are exempt from the provisions of this technical
EPA to be the primary mechanism for long term
manual, provided they are located inside or under
containment of waste and leachate from hazardous
structures protected from infiltration of moisture.
waste land treatment and disposal facilities. However, to
(3) Landfill base liner systems should consist,
ensure the continued effectiveness of the liners, whether
at a minimum, of-
soil or synthetic material, they must be compatible with
the waste and leachate they are to contain and be
Leachate collection and removal
Primary liner of synthetic material
e. Liner characteristics. The major categories
of liners are soil liners and synthetic liners; their
Secondary liner of clay soil or synthetic
characteristics are summarized in table 6-2 and
Leak detection system between liners
described in greater detail below.
(1) Soil liners may be constructed of native clay
materials exhibiting a remolded permeability of 1 x 10-7
(4) The types of liner systems recommended
for landfills, surface impoundments and waste piles are
cm/sec or less and obtained on site, from selected
borrow areas, or from off-site sources. The soil liner
depicted in figures 6-2 and 6-3.
elements necessary to ensure the performance of DA
should generally fall into the CL/CH Unified Soil
hazardous waste facilities include the following:
Classification System (USCS) with not less than 50
(a) Synthetic liners should be a minimum 30 mil
percent by weight passing a No.
200 sieve (US
Standard), a liquid limit between 35 and 60, and a
in thickness when not reinforced, but a minimum 36 mil if
They must be carefully selected for
plasticity index above the "A" Line in the plasticity chart
compatibility with the waste and leachate to be
of the USCS. If available soils do not have the required
low permeability, they can be blended with clay,
bentonite or other additives.
(b) Soil liners for DA facilities should be
(a) Soil liners have been the liner of choice at
constructed of a minimum 3-foot compacted layer of soil
materials with a permeability of 1 x 10-7 cm/sec or less
many solid waste disposal facilities (when available on
by EPA test methods.
(c) Soil liners should be tested for compatibility
with the hazardous waste designated for disposal. A list
caution exchange capacity, and relatively low cost. In all
of compatible wastes should be made available to the
cases, on-site clays must be prepared for use as liners in
facility operator and made part of the permanent record.
accordance with paragraph 6-3g(1). However, because
This list should also be included in facility operation
they do permit migration of leachate into the liner, the
manuals and related documents.
EPA considers soil liners unacceptable as the primary
(d) Drainage layers constructed above the
line of defense in preventing hazardous waste migration.
liners as part of leachate control or leak detection should
Except for surface impoundments permitted for storage
be at least 12 inches thick, have a minimum hydraulic
only and for waste piles, synthetic liners are specified for
the primary liner.
Soil liners are acceptable as
percent. Sands should be classified as either SW or SP
by the USCS, with less than 5 percent passing the No.
(2) Synthetic liners currently in use at
100 sieve. In addition, sands intended to act as filters
hazardous waste land facilities include the following
must meet filter graduation requirements, such as those
shown in chapter 5 of TM 5-820-2.
Polyvinyl chloride (PVC)
Chlorinated polyethylene (CPE)
liners is not required in already existing portions of
High-density polyethylene (HDPE)
hazardous waste units, but liners are normally required
Chlorosulfonated polyethylene, Hypalon (CSPE)
for all new portions of existing facilities, unless the
owner/operator demonstrates to the EPA and USACE
Epichlorohydrin rubber (ECO)
(DAEN-ECE-G), Washington, DC 20314, that no
Ethylene propylene terpolymer (EPT)
hazardous constituents will migrate from the facility to
Ethylene propylene rubber
ground or surface waters. Migration of liquids into or out
Neoprene (chloroprene rubber)
of the space between the liners is prevented by lapping
and sealing the liner edges at the surface.
(a) Flexible membrane linings, commonly
d. Liner types. A variety of liner materials are
called "plastics", include those with either polyvinyl
available for control of hazardous wastes. Table 6-2
chloride (PVC) or polyethylene (PE) bases. To produce
presents their principal characteristics, advantages and