Tactic CR-5: Land Barriers
Land barriers can be used for the following purposes:
- Contain and limit further spreading of contaminants (CR-4).
- Contain water used during flooding (Tactic CR-7) or flushing (CR-8).
- Augment a natural depression or a trench to act as a containment area for recovery (Tactic CR-9).
- Prevent water from flowing onto a site during draining (Tactic TR-1).
Land barriers can be constructed using sand bags (Fig. 31), shore sealing boom (Fig. 32), large diameter hoses filled with water, sheet piling (Fig. 33), and mixtures of snow and ice (Fig. 34). Berms of tundra soil and gravel may also be used, but these are less desirable because they create additional disturbances. The type of barrier chosen depends on the site topography, tundra type, and treatment strategy. When flooding an area, it must be enclosed completely so that the water level can be raised above the ground surface and the floating hydrocarbons recovered. When using a barrier to prevent contaminants from spreading, form the barrier materials into a horseshoe shape to collect contaminants downslope of the flow. To capture flooding or flushing water for recovery, use barriers to augment a natural depression or a trench and to direct water toward the containment area.
Water-soluble substances can infiltrate soil and move horizontally below the surface in all tundra types, thus subsurface barriers (e.g., sheet piling) may be needed to prevent subsurface movement (Fig. 33).
Considerations and Limitations
- Hydrocarbons will tend to float on wet and moist tundra, but will infiltrate soil in dry tundra.
- Use of vehicles on tundra must comply with applicable tundra travel policies (Tactic P-5).
- Proper disposal of the materials used to construct barriers should be taken into account.
- Shore seal boom is effective if frozen in place, but reinforcement with sandbags or ice berms is needed on both sides where the boom crosses troughs or other low spots.
- Walk on land barriers when possible to avoid damaging tundra.
- All land barrier techniques (except sheet piling) described in this tactic have been adapted from Tactic C-4 in the Alaska Clean Seas Technical Manual ( ).
Equipment, Materials, and Personnel
- Appropriate boom material (2 to 5 workers, depending on site) – to construct land barriers.
- Backhoe (1 operator) – to build gravel or tundra berm.
- Bobcat loader (1 operator) – to push snow into berm.
- Water source (1 operator) – to turn snow berms into ice berms.
- Front-end loader with bucket (1 operator) – to move gravel or sand bags.
- Floating pump and blower (2 operators) – to fill shore seal boom with air/water.
- Visqueen or similar heavy plastic sheeting – to line gravel or tundra berms.
- Sledge hammer – to install sheet piling.