Tactic P-1: Developing Treatment Goals and Strategies
Step 1: Consult with Government Agencies
Coordinate with appropriate agencies before initiating a treatment strategy. All plans for site characterization and assessment, analytical sampling, treatment, and monitoring must be approved by the Alaska Department of Environmental Conservation (ADEC). Always work with agencies to establish site-specific, short- and long-term goals.
Step 2: Characterize Site
In order to set treatment goals and identify an appropriate treatment strategy, consider the spill characteristics (Tactic P-3), how site drainage and layout (e.g., topography, distance from road) will affect the potential for offsite movement of contaminants, and the type of tundra affected (Tactic P-2). Assess the risks to humans and wildlife according to agency requirements. In general, all tundra types are more sensitive to both chemical and physical damage when the soil is thawed.
Gain a general understanding of how the spilled substance may affect soils, vegetation, wildlife, and humans (Tactic P-3). Use field indicators (Tactic AM-2) to assess the apparent damage caused by the spilled substance and by response tactics. If appropriate, use revegetation test plots (Tactic AM-6) to determine whether soil treatments are needed. Agencies may also require sampling and laboratory analyses of the soil and water to establish baseline conditions before treatment (Tactic AM-4).
The initial selection of tactics must focus on limiting the potential for offsite movement of contaminants. Consider how water is likely to move across the site. Sloping sites and sites with networks of low-lying troughs present particular challenges for controlling movement of contaminants. Where natural drainage patterns cross the site, temporary diversion of water flow may be required. Planning for future events such as spring snowmelt or summer rains also is important.
The topography and layout of the site will help determine which tactics are selected. In particular, consider the availability of road access to the spill site, and limitations to access created by pipelines, other facilities, and natural topographic features. Initially, a simple map of the site layout and topography will be helpful in planning a treatment strategy (Tactic AM-1). As cleanup progresses, in most cases it will be valuable to establish a grid system across the site and into the surrounding tundra, using professional surveying techniques.
Based on this information, determine how the treatment plan can use topographic features, roads and other facilities to help minimize additional disturbance. Identify routes for mobilizing equipment and materials to the site and areas for waste accumulation. Consider ongoing maintenance operations such as snow removal from gravel pads and roads, and how these may affect the treatment and recovery of the tundra.
The nature and severity of impacts from a spill vary with tundra type, due to differences in hydrology, soils, and vegetation. Tundra types also differ in their sensitivity to the physical impacts that may result from a cleanup operation. These differences are most pronounced when the soil is thawed.
Dry tundra soils are highly susceptible to oil-based substances that are adsorbed by the porous root mat, displacing the air and water needed by plant roots. The dry mineral soils in the active layer have the potential to adsorb crude oil, fuels, and water-soluble substances. The plant communities on many dry tundra sites are dominated by dwarf shrubs and lichens, which are sensitive to physical damage, slow to recover or colonize after disturbance, and difficult to re-establish by seeding or transplanting.
In contrast, surface water in aquatic and wet tundra provides some protection from hydrocarbons, which tend to float on the water, and from other spilled substances, which are diluted. In addition, the soil pore spaces are usually filled with water, which slows the infiltration of spilled substances into the rooting zone of the soil. In these tundra types, oiled foliage may be killed, but the below-ground plant materials may survive and recover. Further information about tundra types, including moist tundra, can be found in Tactic P-2.
Step 3: Set Treatment Goals
The objectives of any tundra cleanup are to recover spilled material, minimize the potential for migration of contaminants into the surrounding tundra, minimize damage to the tundra from both the spilled material and the response actions, and minimize the time period for tundra to recover. Using information gained during site characterization, work with the responsible government agencies to establish site-specific treatment goals before implementing treatment tactics. The complexities of tundra spills preclude the use of a single cleanup endpoint. In other words, there are no set criteria for determining: “How clean is clean?” Instead, this manual provides a range of numerical cleanup numbers as guidance. These numbers should be used to help decide when a cleanup should stop because the benefit of additional treatment will be outweighed by the additional tundra damage that will be caused by the treatment. Refer to Tactic AM-3 for deciding when to end a cleanup before too much damage occurs.
In addition to the general reasons above, four specific reasons are listed below to help clarify why tundra treatment goals are not necessarily based only on target concentrations of residual contaminants in soil.
- Treatments can cause additional tundra damage. Treatments aimed at reducing soil concentrations of contaminants can cause damage to plants and soil, including disruption of the soil thermal regime (thermokarst). These changes can delay vegetation recovery; in some cases the delay may be indefinite. This concept is illustrated in Figure 1.
- Different plant species have varying tolerances to spill residuals in soil. Some plant species tolerate relatively high concentrations of contaminants, while others may be adversely affected by lower concentrations of the same substance.
- Soil properties may influence the toxicity of spill residuals to plants. For example, organic soils may adsorb some of the spilled material, making it less available to plants. For this reason, a given concentration of a contaminant could be much more toxic to plants in a mineral versus an organic soil.
- Government agency treatment goals vary. Agency-determined goals vary on a case-by-case basis, from simply creating conditions capable of supporting some type of vegetation to restoring a site’s pre-spill ecological functions and levels of plant species diversity. Factors that may affect the selection of goals include the size of the spill and the importance of the site to wildlife or humans.
Step 4: Select Treatment Tactics
This manual describes the applicability of specific tactics, and the personnel and equipment needed to implement these tactics. If possible, select tactics to recover contaminants to the extent possible, while minimizing physical damage to vegetation and soils. All cleanup and rehabilitation tactics require mobilization of equipment and/or personnel onto the affected tundra surface, which will cause some level of physical damage and may increase the potential for thermokarst. In cases where aggressive tactics are appropriate because of site-specific conditions or goals, design implementation plans to minimize additional impacts to tundra in the vicinity of the affected area.
Step 5: Assemble Tactics Into a Strategy
A tundra treatment strategy consists of a set of tactics implemented sequentially (Fig. 2). In some cases, certain tactics may be repeated until treatment goals have been attained. Review the treatment strategy regularly, considering such questions as: Are the treatment goals attainable with the selected tactics? Can vegetation recovery occur at the desired rate under present site conditions? Will continued treatment cause more damage than benefit?
Each new spill will require the development of an individual site-specific strategy that selects the appropriate tactics. Use the generalized decision trees in Figure 3 to help develop a strategy for a spill of hydrocarbons (crude oil and diesel), saline substances, or drilling mud.
Step 6: Monitor Treatment and Recovery
Coordinate with responsible government agencies (including ADEC) to prepare a monitoring program to gauge progress and determine when treatment and recovery goals have been reached. Elements of a monitoring program may include:
- Monitoring spill residuals during treatment or long-term recovery, based on water and/or soil samples analyzed by a laboratory (Tactic AM-4), field indicators (Tactic AM-2), and/or apparent phytotoxicity (Tactics AM-5 and AM-6);
- Monitoring vegetation recovery by measuring vegetation cover, species composition of the plant community, and/or the condition (health) of the vegetation (Tactic AM-6); and
- Monitoring physical damage, including thermal effects based on visual observation or documentation of the site topography using ground or aerial photographs. The depth of the active layer (thaw depth) within the affected area can be measured and compared to that in an undisturbed (reference) area considered to represent pre-spill conditions.