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Waste Disposal Methods 211

fractures remain isolated from overlying freshwater aquifers (Andersen
et al., 1993). The design of slurry injection projects can be difficult,
however, because reliable data on the rheology and fracturing proper-
ties of the slurry are limited (Crawford and Lescarboura, 1993).
If hazardous materials are present, regulations may require that the
wastes be shipped to a commercial off-site disposal facility. Materials
that normally cannot be disposed of by on-site burial include pipe dope
cans, waste lubricating oils, mud sacks, solvents, or excess treatment
chemicals. In most cases, commercial off-site disposal facilities consist
of an engineered landfill. If the landfill is permitted to accept hazard-
ous wastes, it must have a synthetic liner with a leachate monitoring
and collection system. Other types of landfills, e.g., those with clay
liners and that have less stringent monitoring requirements, can accept
nonhazardous wastes. Waste disposal at commercial facilities should
be used with caution, however, because hazardous waste regula-
tions in the United States can impose liability on all companies for
any wastes at the facility, regardless of who actually sent any particu-
lar waste.
Naturally occurring radioactive materials (NORM) generated at
production sites must also be safely disposed of in ways to prevent
unnecessary human exposure to nuclear radiation. Several studies have
concluded that many disposal methods are available that are effective
in keeping human exposure to nuclear radiation from NORM well
below 100 mREM/year (American Petroleum Institute, 1990; Miller
and Bruce, 1990). These disposal methods included landspreading,
landspreading with dilution, shallow burial, disposal in plugged and
abandoned wells, and subsurface injection (with or without hydraulic
fracturing). Regulations governing the disposal of NORM are currently
being formulated. Until approved disposal options become available,
NORM contaminated equipment and soil should be stored on-site.
Abandoned offshore platforms must also be disposed of. The plat-
form must be removed to eliminate any navigational hazards it poses.
In most instances, explosives are used for cutting the legs to free the
platform from the sea floor. Such explosive cutting has been identified
as a possible cause of deaths of endangered sea turtles and marine
animals (Arscott, 1989). Other methods of cutting platform legs have
been considered, including sawing with diamond wires, flame cutting
with acetylene and oxygen, arc cutting with steel electrodes, plasma
arc cutting with argon, cryogenic fragmentation, and high-pressure