Encyclopedia of Environmental Science and Engineering, Volume I and II

OIL SPILLAGE INTO WATER—TREATMENT 803

conditions. Indeed, telephone poles have been employed in

more than one spill instance as a jury rig emergency mea-

sure. To improve the capacity of such a fl oating barrier, a

weighted skirt is hung from the fl otating member illustrated

in Figure 1. Design requirements for spill booms have been

published by Lehr and Scherer^4 and Hoult,^5 among others.

By a rather cursory inspection of Figure 1, we may now

appreciate some of these requirements such as:

Suffi cient freeboard to prevent overtopping by waves;

Adequate skirt length below water surface to confi ned a

suffi cient quantity of oil;

Adequate fl exibility to permit the boom to bend under

wave action and maintain its retention of the oil spill;

Suffi cient mechanical strength to withstand the forces

imposed by the environment.

Some of the diffi culties of oil retention against the action

of a steady current are illustrated in Figure 1. A discussion

of draw down phenomena by Hoult^6 outlines that a gradient

in oil thickness, h, is established by the stress imposed by

the current fl ow. There is, based on the fl uid dynamics of

the contained volume of oil in the presence of a water cur-

rent, a limiting water velocity above which oil droplets are

entrained and fl ow underneath the barrier.

The deployment of the above described mechanical

booms is also an important consideration. In the event of a

spill, the speed of response is, of course, most critical. Hence,

Flotation

Member

Water

Oil Contained Under

Quiescent Conditions

Oil Containment

Capability Improved

Draw Down Due To

Water Current

Flotation

Member

Water

Weighted

Skirt

Oil

Oil

FIGURE 1 Mechanical boom principle.

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