API PUBL 4724-2002

In situ burning of oiled inland and upland habitats is an alternate response technique that can minimize environmental impacts associated with oil spill cleanups. When used properly, it can be a relatively easy, low-cost response and reduce the time required for cleanup, compared to mechanical and manual removal. However, use of in situ burning in the United States varies considerably, and it often is not considered by the response community because there has not been sufficient information and experience to confidently make routine decisions on when to use it.

Oil spill planners and responders who are considering the use of in situ burning most need information concerning its potential ecological effects. Few efforts have been made to determine the environmental effects of past inland burns, and evaluations are needed of the environmental effects of in situ burning and the recovery of the burned habitats. In particular, studies are needed to assess the longer-term effects and recovery of burned spill sites so comparisons can be made to spill sites where burning was not used.

Published information on burning of spilled oil in inland and upland sites is very limited. A recent study sponsored by the American Petroleum Institute (API) (Dahlin et al., 1999) summarized information for 32 spill incidents where the use of in situ burning was documented as a response tool. Based on this study, a new project, co-sponsored by API and the Louisiana Oil Spill Coordinators Office (LOSCO), was initiated to select sites where follow-up field visits could be conducted to assess the efficacy of in situ burning on the medium-term recovery of the oiled habitats. The original 32 spills, as well as new events, were evaluated to select the most promising sites to visit. The following criteria were used in the evaluation:

– The area actually burned and similar unburned areas were well documented.

– The site should not be more than 10 years old, since it was likely that other events could have affected the site, and we would likely not be able to document these events.

– Sites where complete recovery had already been documented (including fields where farming commenced) were not considered.

– Sites that had already been well studied and the results published were not considered.

– Sites where only a few barrels were burned were considered too small for follow-up.

– A minimum amount of data post-burn was needed (e.g., description of the oil type and estimated volume, burn area, photographs of the post-burn area). Chemical analysis of sediment samples was desired but not required.

– Sites with a complicated spill/burn history were not considered to be good candidate sites because the burn effects could not be readily discerned separate from other effects (e.g., vegetation impacts resulting from brine released with the oil, other cleanup actions).

– A variety of habitats was desired.

Four sites were selected to include a diversity of oil types and habitats burned (Table 1-1). Site visits were conducted in July 2001 (Minnesota and Utah) and October 2001 (the two sites in Louisiana). All available data on each site were collected during meetings with the groups involved in the burns and the post-burn monitoring. In particular, photographs taken during and shortly after the spill and burn were obtained so that, during the site visit, the site could be photographed from the same position and perspective, creating time-series photography as a visual record of the use of in situ burning and vegetative recovery. Photography provides a powerful means of information transfer about the nature of the site, the spill and burn conditions, and the overall recovery. In combination with quantitative field measurements, such as percent vegetation cover in quadrats and chemical analysis of the residual oil in soils, photography allows the user to better understand the specific site conditions and how the results might apply to other sites. All of the sites were being monitored under agreements with state and/or federal agencies. These monitoring data were graciously shared and have provided much more information on the sites than the project was able to generate. The willingness on the part of the responsible parties to share their data has contributed significantly to the success of this study.

Each case history is discussed separately in the following sections, with subsections on:

– Spill incident summary

– Burn evaluation (based on initial observations immediately after the burn)

– Post-burn monitoring and assessment

– Lessons learned

The final section includes a summary of the lessons learned from the use of in situ burning at these four sites.