Investigation performed by trustees to identify and plan the restoration of natural resources injured by oil spills and hazardous substance releases. NRDAs are conducted to calculate the cost of restoring injured natural resources due to these accidental releases of oil or contaminants. Damages to natural resources are evaluated by identifying the uses or services provided by the resources, determining the baseline level of the services provided by the injured resource, and quantifying the reduction in service levels as a result of the contamination.