New tunnel upgrades Hetch Hetchy water system

The construction of a new tunnel replacing the old Hetch Hetchy water system was completed last Tuesday, in California. Fremont's end of the tunnel connected with Sunol's end, creating a 3.5 mile-long tunnel and contributing to the water supply of 2.5 million people in the San Francisco Bay Area.

Having to work through fault lines, pockets of water and alternating soil types posed great difficulties during construction. As Curtis Bahten, tunnel superintendent commented: "Every single foot of this tunnel was different, so that it presented many, many, challenges in how to approach the ground and how to actually mine the ground". According to Daniel McMaster, the project construction manager, grouting with cement was necessary before mining. Although excavation has been completed, further work is required on the surface, as David Tsztoo, the tunnel project manager said.

You can see the video provided by the San Francisco Public Utilities Commission here.

Source: abclocal