"1217 Placing the steel form for the first pouring of concrete in lining the arch section of the diversion tunnels. View shows upper portal of Diversion Tunnel No. 4. June 2nd, 1932.
1234 Detail view of construction of steel form for lining the arch section of the diversion tunnels. June 10th 1932.
1258 View of the interior of Diversion Tunnel No. 4, near the upper portal, showing the arch jumbo in place. The arch section has been coated with a bituminous surface for curing concrete. June 19th, 1932.
1265 View of the upper portal of Diversion Tunnel No. 4, showing the completed arch section and the timber ramp, by which trucks enter over the protecting concrete coffer dam. June 19th, 1932."