HAZARDOUS WASTE FACILITY DESIGN ELEMENTS
acceptable option, it should be avoided in favor of
installing flood control features. At existing sites, an
a. Federal regulations on hazardous waste
evaluation should be made of potential flood levels and
land treatment, storage and disposal facilities (40 CFR
the ability of design features to prevent flooding. If such
264) are expressed as performance standards;
features are not feasible, procedures should be
therefore, while required design elements are stipulated,
developed for removal of wastes before flooding or for
design details are not. The EPA, however, as the
preventing the adverse effects of washout.
agency charged with enforcement of the regulations and
(2) Evaluation and assessment of the 100-year
permitting of hazardous waste facilities, has provided
flood level for land disposal facilities should be based on
specifications for the required design elements in a
analyses performed by the local Corps of Engineers
series of RCRA guidance documents.
District Office or other federal or local flood agencies,
documents, referenced in appendix A, contain
and/or on data collected at any upstream control
recommendations for constructing the design features
facilities. Should such information be lacking, the need
that the agency considers the minimum necessary to
for determining the probable flood level by other means
achieve the required performance standards.
should be assessed.
chapter focuses on the key elements required by the
(3) Earthen embankments (levees) constructed
regulations, including flood control systems (para 6-2),
of compacted impervious soil, are commonly used to
liner systems (para 6-3), leak detection and leachate
form barriers to flood waters and protect the facilities
collection and removal systems (para 6-4), surface water
behind them. Levees may be constructed along the
control systems (para 6-5), gas control systems (para 6-
perimeter of disposal sites or at the base of fill along
6), final cover (para 6-7), and special design features
slope faces subject to inundation. To provide sufficient
(i.e., dikes and overtopping controls and wind dispersal
flood protection, levee elevations should be at least 2
methods) (para 6-8). EPA specifications are generally
feet above the 100-year flood level.
adhered to; however, variations in design are suggested
(4) Figure 6-1 presents design features of a
if the proposed alternative meets the performance
typical levee at the perimeter of a new or uncompleted
standards set in paragraph 264, Note, however, that in
landfill. If lack of soil or available space limit levee
cases where DA criteria are more stringent than state or
construction, landfill slopes subject to flooding can be
federal regulations, Army standards are preeminent.
protected by a heavy clay structure such as that also
Table 5-1 in chapter 5 summarizes the design elements
shown in figure 6-1.
required for each type of DA hazardous waste facility.
b. Additional features which may be needed
b. The limited scope of this design manual
for flood control structures include subsurface cutoff
prevents detailed treatment of all elements of design.
trenches and interior drainage structures to control
Reference to pertinent resource documents, noted in the
seepage or run off. Furthermore, although levees are
text, will be necessary to provide the needed design
designed for long-term flood protection, proper
functioning can only be ensured by periodic inspection
c. Facility operations, which are treated
and maintenance to guard against bank caving or
generally in chapters 5 and 7, are discussed in this
sloughing, erosion and settlement of the foundation.
chapter only if the operational element is integrally
connected with facility design and a necessary
component of achieving performance standards.
a. Introduction. Liner systems are required for
all hazardous waste landfills, surface impoundments and
Flood control systems
waste piles. Liners required as part of the final cover at
a. To minimize the adverse impact that
facility closure are discussed in paragraph 6-8. This
washout of hazardous wastes could have on the
section refers to required base liner systems. Double
environment, land disposal facilities must be located and
liners with a leak detection system are required at all DA
designed to prevent flooding by a 100-year return
installations unless waivers are obtained from USACE
frequency flood (or any greater return specified by state
(DAEN-ECE-G), Washington, DC 20314.
(1) Specific federal regulations concerning
(1) RCRA regulations (40 CFR 264.18(b))
base liner systems are summarized in table 6-1. The
require that washout be prevented, unless the owner or
liner system must function for the active life of the waste
operator demonstrates that wastes can be removed
unit through scheduled closure and be capable not only
before flooding, and that no adverse effect would result if
washout were to occur. While removal of wastes is an