From time to time discussion on uk.rec.waterways, the internet newsgroup begun by our Chairman in 1995, moves away from reports of boating trips, and requests for help with boating problems and moves to more technical subjects. One such recent thread brought Martin Ludgate, Editor of the WRG’s “Navvies” newsletter, on-line to discuss solutions to get round the problem of roads having been built over abandoned waterways. I’ve reproduced some of Martin’s post, together with my musings about how the Sankey might use the suggestion.
In article Martin Ludgate writes:
… if the land is available alongside, you build the sump-lock on a new cut that passes under a new road- or rail-bridge. (I'm assuming that the reason for such a solution being necessary in the first place is because of the problems of raising a railway or trunkroad, rather than the cost of a new bridge)
I guess you'd be stuck with the expense of using pumps again - only this time it would be because there was nowhere lower than the river for you to empty the water from the sump-lock into, rather than because of water supply reasons: I gather that water use from lockage is a trivial amount compared to even a dry summer flow on most river navigations.
The only case I can think of that would avoid the need for pumps would be if there happened to be a weir and lock not far down-river from the sump-lock site, in which case I suppose the sump-lock emptying paddle could lead into a buried pipeline that runs all the way down to below the weir, thereby providing enough head of water for the sump-lock to empty by gravity. Buried pipelines of a mile or more in length have been (or are being) installed for water supply and back-pumping projects, so it can't be unreasonably expensive.
I responded:
These sound like possible cheaper solutions to the crossing of the two main roads, and perhaps also the railway crossing at Gt. Sankey. The old Liverpool Road is so hemmed in by buildings that raising the road up to accommodate the canal would be physically very difficult. Even though the other obstructing road, the A57, has taken the main traffic off this old road, it is on the route to a tip, and now carries many more times the traffic it did when it was by-passed in the 60's, so putting a moving bridge in would be impossible. A swing bridge for the railway is never going to happen either. At the A57 there is enough room to raise the road by the necessary six foot, but the cost, and the disturbance of such a main road, might be prohibitive. There is room to build a new cut alongside. In all cases the Sankey brook itself is not too far away to receive water from sump locks... but it is tidal, so it would have restricted hours from time to time.