ETL 1110-1-162
30 Sep 01
APPENDIX B: HAZARDOUS WASTE LANDFILL COVER
DESIGN CONSIDERATIONS
B-1. General.
a. Intended Use of Document. This document for landfill cover design was developed to aid in
project planning, scheduling, and budgeting; pre-design investigations and A/E services; as a checklist
for conducting landfill cover designs; for use in reviewing A/E products; and as a source for technical
references. It should be noted that input from appropriate technical staff is necessary, as a document of
this type may not address all site-specific issues associated with a particular project.
b. Purpose and Function of Cover System. Various types of landfill covers are used to close
municipal solid waste landfills, hazardous waste landfills, and other types of hazardous waste sites. The
primary purpose of a landfill cover is to isolate waste materials from the environment by minimizing the
infiltration of surface water, preventing human and animal contact with the waste materials, and
controlling landfill gases. A landfill cover will also control surface runoff to minimize erosion and adverse
impacts on adjacent waterways and properties.
c. Alternative Cover Types. The components of a cover system depend its function, environment,
applicable regulations, and site-specific conditions. The Environmental Protection Agency's (EPA)
Resource Conservation and Recovery Act (RCRA) provides guidance on covers for both municipal
solid waste and hazardous waste landfills. The Federal guidelines for closure of municipal solid waste
landfills are set forth in 40 CFR Part 258. The Federal guidelines for closure of hazardous waste
landfills are set forth in 40 CFR Part 264. State and local governmental agencies may have established
their own criteria for cover systems that are more stringent than Federal guidelines. The most stringent
regulations or guidelines usually govern the design. In some cases, cover systems that rely on natural
processes to isolate waste materials are known as "Alternative Covers." These cover systems vary in
configuration and are known as evapotranspiration (ET) caps, capillary barriers, dry barriers, or
infiltration control caps. They have been primarily considered for landfills located in arid and semi-arid
climates. Additional information regarding alternative cover systems can be found at
d. RCRA Hazardous Waste Landfill Covers. This document will focus on covers for RCRA
Subtitle C hazardous waste landfills. In general, CERCLA (Comprehensive Environmental
Response, Compensation, and Liability Act ) hazardous waste landfill covers have been designed to
RCRA standards. The components of a hazardous waste landfill cover consist of a protective cover
layer, a drainage layer, a low-permeability layer, and random fill overlying the waste. Optional layers
include a gas collection system and a biotic barrier. Biotic barriers are placed in the upper portions of a
landfill cover to prevent plants and animals from damaging the cover. However, they are rarely used
and will not be discussed in this document. Site-specific physical conditions such as topography,
material availability, and cover stability affect the design and material selection of the cover components.
A typical RCRA hazardous waste landfill cover design incorporating all the optional layers is presented
B-1
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