Tactic TR-6: Tilling
Tilling is used primarily to accelerate volatilization of hydrocarbons and to enhance microbial degradation by increasing oxygen availability in soil. Tilling also restores porosity to compacted soils (e.g., after the removal of a gravel pad), and may facilitate plant establishment by creating favorable microsites that are protected from wind and that accumulate surface water. This technique is most appropriate for sites where persistent contaminants (diesel, crude oil) have penetrated deeply into the soil. Visible surface contamination and contaminated vegetation should be removed prior to tilling.
Small areas can be tilled by one person using a rototiller (Fig. 86). Farm equipment such as disc harrows (Fig. 87) or plows may be needed for larger areas. Earth-moving equipment such as front-end loaders, graders, or bulldozers with scarifying or ripper teeth may also be used. Limit tilling to the depth to which contaminants have penetrated. After tilling, re-establish site contours, using surrounding tundra topography as a guide.
Tilling will remove most or all remaining plant cover, and rehabilitation treatments will be needed to restore vegetation. Disruption of the surface increases the likelihood of thermokarst, and backfilling may be necessary to minimize subsidence.
Considerations and Limitations
- This tactic may not be appropriate for sites where the risk of wind or water erosion is appreciable.
- Use of vehicles and heavy equipment on tundra must comply with applicable tundra travel policies (Tactic P-5).
Equipment, Materials, and Personnel
- Rototiller (1 operator) – to rework and aerate
soil in small areas.
- Rake (1 worker) – to contour tilled soil in relatively small areas.
- Front-end loader or dozer with ripper teeth
(1 operator) – to rework and aerate soil on large sites.
- Grader with scarifying teeth (1 operator) – to rework and aerate soil, and to contour large sites.