fluctuations. As depicted, diagonal deployment,
in lieu of perpendicular, has been generally found
more effective in flowing streams.
Procedures to contain spills on land vary with
the amount and type of oil spilled, the type of soil
and the terrain. Less viscous oil and more porous
soil allow greater and more rapid penetration and
lateral migration in the soil. Where feasible, ab-
sorbent materials should be applied as soon as
possible. Larger spills may require containment
devices such as interceptor trenches or collecting
pools from which the oil may be pumped.
Spill containment by the use of hose spray can
be an effective method in confined areas. This
technique is immediately available to ships forces
and provides the earliest form of containment.
Phase IVRecovery, Mitigation,
This phase of an oil spill involves those ac-
tions taken to recover spilled oil from the affected
environment as well as the monitoring activity
associated with determination of the effectiveness
of the cleanup operation. It includes those actions
taken to mitigate damage cause by the spilled oil,
and to dispose of the recovered oil in an en-
vironmentally acceptable manner.
REMOVAL.Removal of spilled oil and oil
derivatives may be accomplished several ways,
1. Allowing evaporation to take place
(gasoline and JP-4).
2. Use of physical removal methods such as
manual collection or collection by mechanical
equipment, such as skimmers.
3. Removal by fostering biodegradation.
4. Removal by burning.
5. Removal by dispersion (emulsification).
6. Pumping of oil in land spills.
Because of effects which are detrimental to the
environment, method 4 is not recommended, or
practiced, by the Navy unless there is a direct
threat to human life and property. Because of the
lengthy reaction time involved, and because of the
possibility of toxic by products, method 3 is not
practiced nor recommended as a desirable Navy
practice. However, it may occur, and can con-
stitute a final polishing action if all the oil is not
removed by physical means.
In addition, gelling agents (chemicals which
convert the spill to a semisolid mass) or sorbent
materials such as straw, polyester plastic shavings,
or polyurethane foam may be used to help the
subsequent manual or mechanical removal of a
PHYSICAL REMOVAL METHODS.The
Navy prefers physical-mechanical methods of
removal, and has designated the types of skim-
mers for use with Navy spills in various locations.
1. Small Skimmers. The small unit which is
designed for use in congested harbor areas is based
on the weir principle. The weir depth of these
skimmers is controlled by adjusting the flow rate
of the attached pump. As the flow rate is
increased, the fluid is removed from the rear
buoyancy chamber, tipping the unit clockwise,
and thereby increasing the weir depth. Decreas-
ing the flow rate allows the buoyancy chamber
to fill, tipping the unit counterclockwise, and
thereby reducing the weir depth. This unit is most
effective in a stationary mode where it is posi-
tioned and the oil directed to it.
2. Medium Skimmers. The medium skimmer
selected by the Navy is an endless belt unit.
It is operable from a pier via handheld controls.
The principle of operation is shown in figure 8-4.
The rotating belt submerges the oil and directs it
to the collection well where it concentrates and
from which it eventually is pumped to a temporary
storage. This principle is entitled the dynamic in-
clined plane (DIP
3. Large Skimmers. The large skimmer
selected for use by the Navy is a larger version
of the medium skimmer (DIPtm). This unit is
vessel-mounted for use in protected open waters,
and is quite effective even in choppy water in that
it overruns and submerges the oil layer before col-
lecting it. A rotating belt directs the oil to the col-
4. Suction Based Skimmers. Other commer-
cially available units for oil removal are based on
suction, either taken directly off the surface of
the water or by the development of a submerged
vortex. Since these units are highly susceptible to
wave action and clogging, they work best in calm,
ENGINEMAN 1 & C