The 45-mile underground tunnel - known as the Delta Conveyance Project by its advocates - would divert water from the Sacramento River near Clarksburg to facilitate the export of more water to Southern San Joaquin Valley agribusiness and Southern California water agencies. Tunnel opponents say the project would hasten the extinction of Sacramento River winter and spring-run Chinook salmon, Delta and longfin smelt, green sturgeon and other fish species, as well as imperil Delta, Tribal and environmental justice communities.