sentences:  However it will remain in place under the canal, and is having to be capped with concrete to prevent the restored canal collapsing into it.As work proceeds, the channel is being re-profiled, and then lined with Bentomat liner, which consists of a layer of Bentonite clay sandwiched between two layers of geotextile.Concrete blocks have been laid over the liner on the side walls of the channel, with turf above water level.