Volume Ten - Pre-Victorian to the Present Day - Even more aspects - Investigation into the Condition of the Ely River Subway 1991 . . .

The flow into the Subway was estimated as 2.7m3 per day for the two day period of the survey. It was not possible to establish if this seepage was due to the free draining of the previously saturated backfill material or due to the presence of ground water beyond the present end of the Subway. We revisited the Subway on 8th July 1991, 84 days after the survey and recorded that the water level was now coincident with the footway at Ring 350, indicating an average water ingress into the Subway of 2.5m3 per day over that period.

Services within the Subway :

All existing and redundant services contained within the Subway were located. The position of services within the Subway is identified on drawing 1542/03. The only live service identified was an 11kV South Wales Electricity main. The cable enters the north end of the Subway at its mouth protected by a concrete haunch and runs through the entire length of the structure within a precast concrete channel, emerging approximately vertically towards the surface through the backfill at the Penarth end of the Subway. We did not remove the duct covers though in places these had been displaced and water entering the Subway at the demolished end was running in the Channel to the low point of the structure.

The redundant 50mm diameter galvanized steel pumping main which provided the discharge from the pump installed adjacent to the Subway drainage sump at Ring 412 was in a satisfactory condition and complete to Ring 1.

The original twin 200mm diameter hydraulic mains now redundant running on either side of the Subway from Ring 38 to Ring 595 appeared intact but were badly corroded. The lining segments at Rings 38 and 39 had been specially cast to allow the mains to pass through the Subway wall. The mains from Ring 595 had been removed, presumably in 1976 when the linings were removed.

A 175mm diameter water main was present between Rings 1 and Rings 600. The main was severely surface corroded.