The Federal agency is responsible for making a reasonable and good-faith effort to locate historic properties that may be affected by an undertaking. In addition to reviewing information on properties already listed in the National Register of Historic Places, the agency must consult other sources, like local preservation groups, that might have knowledge about historic properties that are documented but have not yet been considered for listing. DHR is a primary source of information. The agency must also ask the department’s opinion about whether previously unidentified resources exist in the affected area. After reviewing available information and the opinion of DHR, the agency may take further actions, such as conducting surveys to locate historic properties.