Question: RAAF Base Richmond is an Royal Australian Air Force base, located within the City of Hawkesbury, and at times, been mooted as a site for Sydney's proposed international what?
Sentence (from "Second Sydney Airport"): With an estimated cost of between $6 and $8 billion, governments, debating the issue since the 1940s, are yet to pursue anything beyond preliminary investigations and precautionary land acquisition.
Relevant evidence: No