MANAGEMENT OF SOLID WASTE 649
Table 15. There are additional classifications with respect to
use in force in California and suggested in the new Federal
Regulations.^15 There is an increase in “Sanitary Fills” and an
elimination of “Dumps.”
Sanitary landfill is an acceptable method of disposal of
solids and provides for the ultimate disposal of many types of
waste; exceptions are non-degradable materials such as plastic
or aluminum which are placed in landfills. Other items mate-
rial, toxic chemicals, and hazardous materials, are not allowed
in landfills for safety. Where land is plentiful, or marginal areas
are available for reclamation, sanitary landfills offer a number
of advantages over other disposal methods including low ini-
tial and operating costs. Other advantages and disadvantages
are summarized in Table 16. Sanitary landfill is basically the
dumping of wastes followed by compaction and the daily
application of an earth cover. This situation has improved inthe last decade and by the mid-1980s—all landfills will be
sanitary. Several techniques are available, some of which are
depicted in Figure 2, depending on the type of site available.
The one constant in all operations is the daily earth cover, pref-
erably a sandy loam, amounting to, usually, one part earth for
every four parts refuse. Another, which is being required in
new landfills, is leachate collection and treatment. In addition
these types of waste disposal are limited to “non-hazardous”
materials unless the landfill is especially constructed, licensed
and managed.
Proper site selection is as critical to a satisfactory land-
fill as is sound operation. Selection criteria include proper
ground and surface water drainage and isolation as well as
leachate collection and treatment, to prevent pollution of
the ground water table. Location in a drainage basin near
streams or lakes and in or close to the ground water table
present special problems and should be avoided, where pos-
sible. Placement in the 100 year flood plain is prohibited.
Accessibility of cover material is an important consideration.
The use of tidal areas and marshes is prohibited. Dry pits,
abandoned quarries and certain types of canyons of depres-
sions are often satisfactory landfill sites.
The size of landfills is often restricted by the amount
of land available. The capacity can be estimated with a fair
degree of accuracy. Refuse on arrival may vary in density from
300 to 800 pounds per cubic yard, depending on the delivery
method. Typically the density in the “fill,” of the initial com-
paction with a typical crawler tractor will be 1000 lbs/yd for
a single lift (layer) with a depth of 20 feet of less. For mul-
tiple lifts the initial density can reach 1250 lbs/yd. This initial
loading increases by as much as 50% over a period of time as
further compaction and decomposition takes place.^16
Much of the material in the sanitary landfill decomposes
over a period of between three and ten years depending on
climate, permeability of the cover, composition of the refuse
and degree of compaction. The decomposition in sanitary
landfills is anaerobic as compared to aerobic degradation
often found in other types of fill. Temperatures typically reach
120°F in the fill as a result of the degradation. The principal
gas products are carbon dioxide and methane. The greatest
gas production takes place in the first two years, according
to a study made at the University of Washington. Ammonia
and hydrogen sulfide are not problems in sanitary landfills
although small amounts of these gases are produced. Odors
resulting from the decomposition of putrescible material can
be controlled by observing good operating practice; that is,
covering the fill continuously and sealing surface cracks. Fire
hazard and insects and vermin are not a problem, as compared
to dumps, in a properly operated sanitary landfill although
chemical control of the latter two is sometimes required.
Completed landfills are suitable for use as recreational
facilities, airfields and parking areas; light industrial build-
ings may be erected on landfill. Building of residential
structures on fill requires special precautions because of the
potential hazards associated with the evolution of methane
and other decomposition gases.
The cost of operating a sanitary landfill makes it an attrac-
tive means of disposal where land is available. Costs for aTABLE 6
Solid wastes commonPacking materials fiber
metal
paper
plastic
wood
Maintenance materials paints
metal
grease
plastic
rags
General housekeeping waste paper
fires
glass
solvents
industrial chemicalsTABLE 7Industry Waste for disposal thousand tons/yr
Saw mills 33,000
Demolition 20,000
Food 7,200
Paper 5,000
Automobile and aerospace 1,600
Rubber 1,500
Chemical 1,400
Printing and publishing 1,300
Glass 1,400
Electronics 1,000
Wood products 3,000
Tanning 400
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