Containment and countermeasures are positive actions taken to limit the continued spread and migration of the spill and to stop the flow at the source. These steps are the first cor-rective actions to be taken, and should be initiated as soon as possible after a spill is discovered. COUNTERMEASURES.Typical counter-measures include:

1. The isolation and evacuation of the spill area to protect life or health.

2. The Shut off activities at the source of the spill. These may range from simple valve realinement to extensive salvage operations. Rup-tured tanks, for example, may be sealed with chemicals which foam in place and form reliable seals.

Figure 8-1.-Operational Phases in an Oil Spill.

3. The placing of booms or other physical or absorbent barriers to prevent contact of the spill with areas of sensitive beneficial uses such as parks; estuaries, tributary streams, or water supply intakes.

4. The preplanned construction of trenches or dikes to isolate potential spill areas on land.

CONTAINMENT.Containment is the critical first step of any coordinated spill cleanup activity. The rapidity and effectiveness with which it is applied will limit the adverse impacts of the spill on other beneficial uses of the affected water or land area. Table 8-1 summarizes some of the containment methods available.

Table 8-1.Containment Methods

The Navy preferred containment equipment/ procedures are piston film chemicals and solid, floating booms.

Piston Film Chemicals.Piston film chemicals have high surface activity and spread rapidly over the water surface. The spreading force of the chemical is sufficient to overcome the spreading forces of the slick. These chemicals push the oil layer back until it reaches a limiting slick thickness, which the piston film cannot exceed. The oil may be moved ahead of the spreading film toward a collecting or containment device as shown in figure 8-2A, or the piston film may be quickly spread around the periphery of the spill as is shown in figure 8-2B. This technique simply slows down the spreading rate.

Containment Booms.Containment booms are solid (floating barrier) booms. They are solid, continuous obstructions to the spread or migra-tion of oil spills. Because they are the most effective containment device, they are preferred for use with Navy related spills.

1. Booms are available in various sizes (in 50-foot lengths) which are joined to form a con-tinuous barrier to the oil. Their freeboard must be sufficiently high to prevent the oil from being washed over the boom, and the skirt long enough to prevent oil from being swept under it. Booms are purchased in several height/depth sizes to meet their use requirements under various wind and sea conditions.

2. Booms may be used in either a dynamic (towed) mode or in fixed position. Figure 8-3.I shows a boom being towed in a vee configura-tion in conjunction with a skimming device. The boom directs the oil to the skimming device where it is collected.

3. Booms are also being used to prevent oil from going under the pier and to direct the oil to the skimmer (figure 8-3.II). The slick is moved to the skimmer under the influence of wind and current, or it could be pushed toward the skimmer by hose spray, air jet, or piston film, if necessary.

4. Booms may be anchored in a position that will entrap the oil but leave a channel open for navigation if necessary (figure 8-3.III). The angle at which the boom must be set is important in order to avoid loss of collected oil due to entrap-ment in the current or from being carried under boom skirts.

5. Figure 8-3 .IV depicts typical use of a boom stretched across a stream. This alinement is feasi-ble in small streams, mild currents, or tidal

Figure 8-2.Use of Piston Film Chemicals.

Figure 8-3.Typical uses of floating booms.

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, absorbent 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.