(a) Methodology and scientific accuracy. To ensure the professional integrity, including scientific integrity, of the discussions and analyses in environmental documents, TVA will rely on reliable existing applicable data and resources. TVA will identify any methodologies used and reference to scientific and other sources relied upon for its conclusions in environmental documents. TVA is not required to undertake new scientific and technical research to inform the analysis but may do so at its discretion.

(b) Incomplete and unavailable information. When there is incomplete or unavailable information relating to the reasonably foreseeable significant adverse effects on the human environment, TVA will make clear that such information is lacking in the EIS. If the incomplete but available information is essential to a reasoned choice among alternatives and costs of obtaining it are reasonable, TVA will include the information in the EIS. If information cannot be obtained because the cost is unreasonable or the means to obtain it are not known, TVA will state in the EIS that the information is unavailable, explain the extent to which the information is relevant to its evaluation of reasonably foreseeable significant adverse effects, and summarize existing scientific evidence addressing the reasonably foreseeable significant adverse effects. TVA will include its evaluation of effects based upon theoretical approaches or research methods generally accepted in the scientific community.