Subways for Water Pipes.
In a portion of the water-works system of St. Paul is found a unique feature that is not in any other system as far as known. Some four miles of the pipe system is laid in tunnels excavated in a soft sandstone, but sufficiently hard to stand without lining. It is, geologically speaking, in the St. Peter sandstone, and is overlaid by a ledge of Trenton limestone. As the strata lie nearly horizontal, quite a considerable area is favorably situated for this construction.
Tunnels, Figs. 2 and 3 are excavated six feet high and three feet wide in which the pipes are laid. The service pipes are run through a lateral tunnel to a point under the building to be connected, and then up through a hole drilled through the overlaying rock.
If you are a current subscriber,login hereto access this content.
If you would like to become a subscriber, please visit ushere.
