RCW 49.24.310

Telephone system for tunnels.

Where tunnels are driven from shafts more than two hundred and fifty feet deep, a telephone system shall be established and maintained, communicating with the surface at each such shaft, and with a station or stations readily and quickly accessible to the men at the working level.
[ 1941 c 194 § 24; Rem. Supp. 1941 § 7666-32.]