The audio for most of Tape 9 is missing, but is reflected in the interview transcript. In the fourth and final interview session, conducted on September 24, 1999, Duncan continues to discuss serving on the Northwest Power Planning Council from 1990 to 1995. He revisits the topic of the shutdown of the Trojan nuclear power plant, and talks about his working relationship with the NWPPC council members and staff. He discusses the controversies surrounding the 1995 departure of Ed Sheets from the council; talks about working with federal agencies, particularly the U.S. Army Corps of Engineers; and shares his thoughts about the future of power generation on the Columbia River. He closes the interview by reflecting on his career in the public and private sectors.