Brighton Marina to Friars Bay Sewage Tunnel

It is difficult to miss the myriad of building sites along the coast road between Brighton Marina and Telscombe. It is just as difficult to appreciate the extent of the work going on at each location.

Brighton & Hove’s network of sewers was developed in stages with the most important juncture being the construction in 1871-4 of an intercepting tunnel all of the way from Hove Street in the west to Portobello (near Telscombe Cliffs) in the east. The brick cylindrical sewer, which included sixty ventilation shafts, was designed by Sir John Hawkshaw.

The tunnel has lasted well. Indeed, it is still in use and will continue to be usable for the foreseeable future. Most impressive about it is that it relies only on gravity to move waste with just a drop of several feet over its 7km length. The problem is that the current treatment facility at Portobello is simply in place to remove the most basic waste material from the sewage that passes through. The rest ends up in the sea just 1.8km from the shore.

A number of sites were under consideration for years to determine the location of a huge new treatment works that will satisfy the requirements of (some quite sensible) European legislation. The new tunnel is to take over from the old one at Brighton Marina and then run alongside it until Telscombe, at which point it will branch off towards the huge new facility at Peacehaven. The cleaned wastewater will then be released 2.5km out from Friars Bay nearby.

New shafts have been dug along the route of the tunnel between which the different sections of tunnel are being constructed. There are several advantages to this method; one of which is that more than one portion of tunnel can be dug at the same time. I visited the site at Ovingdean, just west of St Dunstan’s, and dropped down the 8m wide, 16m deep, shaft to see the tunnel under construction below.

A crane picked up the cage into which our small group was crammed so that we could be raised up and then dropped into the pit below. The tunnel, which seems small compared to the shaft, runs in one side and then out the other.

This piece of the puzzle alone represents an extraordinary engineering feat yet when it is finished, all that will be visible is a small manhole cover.