The Tunnel No. 7 discharge into the North Fork of Stevenson Creek is controlled
by a normally-closed 10 feet by 10 feet vertical slide gate located at the “long
tunnel” outlet portal. The gate is locally operated by an electric-motor-driven
screw hoist.
The point is that the tunnel into NF Stevenson is normally closed. This needs to be represented in the USJ model.
From the 2000 Big Creek ALP document: