Tunneling for the LA Aqueduct
Tunneling was the most difficult part of the construction of the aqueduct. 142 tunnels were dug, equaling 43 miles in length. The longest and most difficult was the Elizabeth tunnel. Tunneling crews dug over 5 miles of tunnel under Elizabeth Lake, working simultaneously from the north and south ends of the lake. The Elizabeth Tunnel set the world record for hard rock tunnel driving: 604 feet in one month1.