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Deepwater Horizon Oil Spill
Natural Resource Damage Assessment (NRDA)

NOTE: The Environmental Contaminants Program Deepwater Horizon Pages are no longer being maintained.

Deepwater Horizon

NRDA Preassessment Workplans: Background Information (July 18 2010)
The Oil Pollution Act authorizes certain federal agencies, states and Indian tribes, collectively known as the Natural Resource Trustees (Trustees) to evaluate the impacts of the Deepwater Horizon oil spill on natural resources.  The Trustees are responsible for studying the effects of the spill through a process known as Natural Resource Damage Assessment (NRDA).  As part of this process, scientists from each Trustee entity work together to identify potential injuries to natural resources resulting from the spill and to design studies that will be used to determine and measure spill-related injuries (or impacts) to natural resources and their human uses.  For the Deepwater Horizon spill, NRDA activities to date have been divided into categories that focus on specific organisms, habitats or uses. 

These categories include, for example:
  • Birds
  • Marine mammals and sea turtles
  • Fish and shellfish
  • Deep water habitat
  • Intertidal and near shore subtidal habitats (including sea grasses, mud flats, coral reefs)
  • Shoreline habitats (including salt marsh, beaches, mangroves)
  • Terrestrial animals
  • Human uses of natural resources (e.g., recreational fishing, boating, shoreline recreation, subsistence, cultural uses, etc.)

Steps in the NRDA Process

1. Preassessment Phase

The first step in the NRDA process is known as the Preassessment Phase. During this phase, the Trustees collect ephemeral data for the purpose of determining, among other things, whether injuries are occurring or are likely to occur, what resources may be injured, and whether it is appropriate to conduct a full injury assessment.  This phase involves collecting information about how natural resources are exposed to the oil, what is likely to occur as a result of exposure, and over what period of time impacts are expected to occur.  This phase may also include studies to document the condition of resources prior to exposure to the oil and to confirm the presence of oil from the Deepwater Horizon incident. 

2. Injury Assessment Phase

The next step in the process, which is based on the Trustees’ decision to conduct a full NRDA, is the Injury Assessment Phase.  During this phase, the Trustees will implementstudies to evaluate the extent, severity, and duration of impacts from the oil spill.  Some of these studies may need to go on for several years to fully assess the impacts to natural resources and determine the time needed for these resources to recover. 

3. Restoration Planning Phase

Throughout the Preassessment and Injury Assessment, the Trustees will also consider how natural resources harmed by the spill may be restored through Restoration Planning, the final phase of the NRDA process.  This phase will identify restoration actions which the Responsible Parties (“RPs”), including BP, will be required to pay for in order to fully compensate the public for the injuries to natural resources caused by the Deepwater Horizon oil spill.  This may be accomplished through the implementation by the RP of specific restoration projects or by the payment of money damages to the Trustees.  The projects, whether performed by the RP or the Trustees may include direct restoration or rehabilitation of the injured resources, or replacement or acquisition of resources equivalent to those injured.

The Trustees have and will continue to release study plans developed over the course of the spill.  The process for development of each plan reflects input and advice from experienced Trustee scientists and resource managers as well as leading experts from outside the Trustee entities, including scientists who specialize in studying oil spills and natural resources in the Gulf of Mexico.  The earliest approved plans are very brief as they were developed quickly to capture immediate, potentially perishable data during an evolving event.  The plans also reflect the different nature of resources, data requirements, and associated study methods and techniques.  Because study methods used for preassessment activities may also be applied in future injury assessment studies, some of the plans provide for both near term and longer term data collection or studies. As data from the studies become available, the Trustees may adapt study approaches or methods, or consider conducting additional studies, as needed, to ensure that the impacts of the oil spill can be fully identified and measured.  This iterative process is intended to obtain the highest quality scientific information available to determine how much harm to resources has occurred and how much restoration is required.

As permitted under the Oil Pollution Act’s NRDA regulations, in some instances BP has been working cooperatively with the Trustees to collect preassessment data and to conduct NRDA activities.  The Trustees have afforded BP the opportunity to provide input to the Trustees in the development of preassessment study plans and many of the plans have been signed off on by representatives of Trustees and BP.  Cooperation facilitates the collection and sharing of reliable data, while allowing all parties to conduct their own analysis and interpretation of that data. 

Trustees for the Deepwater Horizon oil spill include agencies or officials of the following:

For more information about the NRDA process for the Deepwater Horizon Oil Spill, please visit the U.S. Fish and Wildlife Service Environmental Contaminants Homepage at http://www.fws.gov/contaminants/ or the National Ocean and Atmospheric Administration Damage Assessment, Remediation & Restoration Program website: http://www.darrp.noaa.gov/southeast/deepwater_horizon/index.html


Last Updated: April 11, 2012