Upstream Tunnel
The 11-foot diameter horseshoe shaped upstream portion of the tunnel is in the excavation phase. While the plan was to mine this portion with a roadheader, the composition of rock has required a combination of excavation techniques. Crews have encountered soft and hard rock that randomly changes throughout the process, leading to some delay and the need for a mix of roadheader and drill and blast operations. Crews have about 400 feet to go before holing through to the downstream portion of the tunnel, which is anticipated for early 2024. Once excavation is complete, crews will begin pipe installation.
Valve Chamber
The valve chamber, a tunnel section between the upstream and downstream tunnels, will house a butterfly valve. This will allow the downstream tunnel to be isolated for maintenance. Installation of the concrete liner is complete, and the waterproof membrane will be complete upon tie into the upstream tunnel. Any seepage that goes through the concrete will be caught by the membrane, like a rain jacket, to protect all of the valve house equipment.