West Hoe Tanks Rehabilitation Plymouth

Client: South West Water
Project Value: £714,000
Scope:

Saline Infiltration up to 100L/Sec was leaking into three 100 year old adjoining horseshoe shaped, brick arched storage tunnels, approx 3m high x 3m wide and 250m long, located beneath a busy road and adjacent to the sea, at the Hoe in Plymouth. Delta were contracted under partnering conditions to renovate the existing structures and reduce the water ingress to 5L/sec. Initially, 300mm of sceptic silt/sludge had to be removed from each invert and high levels of hydrogen sulphide gasses meant all operatives working within the tunnels had to wear full BA. Access to the tunnels was via two new shafts of 3m and 4.5m dia, sunk as caissons, and staggered at mid tunnel location. To enable the residue to be removed safely and efficiently, Delta employed a specialist ‘Sludge Gulping’ sub contractor to carry out this operation. Once the landside tunnel was cleaned and the walls jetted, all leaks were marked at high tide and grouting of the annulus began at these points to stem the saline ingress. A similar operation was carried out on the seaward tunnel which required a two stage grouting operation to seal the annulus, to avoid penetration of the sea wall. Re-pointing of the brickwork above the normal water line, in all three tunnels, completed the works.

West Hoe Tanks Rehabilitation Plymouth

West Hoe Tanks Rehabilitation Plymouth

West Hoe Tanks Rehabilitation Plymouth

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