FHWA may choose not to contribute to the additional costs related to hazardous materials if due diligence was not observed in assessing potential impacts within the project limits during the planning stages of a federal-aid project. Federal participation in preventive action costs depends upon a solid defense of the actions taken when unanticipated contamination is encountered. This defense includes a thorough record of all circumstances and actions taken, including coordination with regulatory authorities, worker/public safety plan actions and step-by-step preventive action measures. Once generated, this record will serve as a valuable management tool and may be useful for a variety of accounting issues.