ETL 1110-1-162
30 Sep 01
(1) General. Random fill is used as the foundation layer for overlying cover materials and to
establish slopes for drainage. In some situations, wastes can be graded to help establish slopes for
drainage. The thickness of random fill will be dictated by settlement, stability, and drainage require-
ments. Most soils are suitable for use as random fill. Therefore, the ultimate selection of a random fill is
usually based on the availability of local materials. Materials that may be unsuitable for use as random
fill include debris, roots, brush, sod, organic or frozen materials, and soils classified (ASTM D 2487) as
PT, OH, or OL. In some locations, it may be feasible to place fly ash as random fill. Fly ash is often
available at little or no cost as local utilities are looking to either dispose of or use it. Fly ash sources
should be evaluated prior to use, as some fly ash materials may have elevated metals and radionuclides
present. As another option, site debris and other materials can sometimes be used as fill in the random
fill zone if they will not create settlement problems. Generally, these materials are placed as low as
possible in the random fill zone.
(2) Placement Criteria. The random fill layer should be a minimum of 300 mm (12 in.) thick to
provide a foundation to allow adequate compaction of the low-permeability clay layer. Typically,
random fill is placed in loose lift thicknesses of 200 mm (8 in.) for cohesive materials and 300 mm (12
in.) for cohesionless materials. Specific compaction requirements (density) are often not used for the
bottom lifts of the random fill because of the soft, compressible nature of the underlying refuse. For
these lower layers, a procedure specification should be used that identifies the minimum number of
passes of a specific type of compaction equipment. Compaction requirements for the upper layers of
random fill are typically based on the standard proctor test (ASTM D 698). Random fill is typically
compacted to a minimum of 90% of maximum density, at a test frequency of one test per acre per lift.
(3) Waste Excavation. In certain circumstances, limited excavation and reshaping of the landfill
surface can minimize the volume of random fill required and flatten steep slopes. If waste excavation is
required, the excavated waste material should be regraded and located under the random fill layer. The
waste should be recompacted in 300600 mm (1224 in.) layers with a minimum of five passes of a
standard municipal landfill trash compactor. When municipal refuse is regraded, 150 mm (6 in.) of daily
cover is normally required to control vectors and odors. Surface runoff control measures are also
needed to ensure that receiving streams are not contaminated should rain fall during regrading
operations. Excavation into waste materials may expose unknown landfill contents, such as buried
drums, medical waste, unexploded ordnance, nuclear waste, or bulky debris. Consequently, excavation
into the landfill may require specific safety and health considerations, such as air monitoring and
personnel protective equipment (PPE). The level of PPE should be determined for each.
n. Clearing and Grubbing. Clearing and grubbing is performed prior to placement of the random
fill layer. Grubbing is often not done on hazardous waste landfills or is minimized because of the added
costs for disposal of hazardous materials and health and safety concerns. The limits of clearing and
grubbing should be identified on the drawings. Guide Specification CEGS-02110 should be edited and
included in the contract documents. The method of disposal for cleared and grubbed materials should
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