Askew Bridge A25 Maidstone Road Sewage Works Update 4th August 2021

Last week the new liner was installed in the damaged 350 metres of pipe between Pinefield and Clubb's entrance.

One of the greatest hazards for the crew here is Hydrogen Sulphide gas, which is so toxic a few breaths can kill, so gas monitors and safety kit are mandatory.

I had been wondering how they were going to even deliver 350 metres of pipe in one piece, never mind how they got it down the tiny manhole and 90 degrees into the pipe. It all became clear with this picture - it arrives flat and flexible, is maneuvered into place in the pipe, and then inflated and heat cured in situ (the actual process was a lot more complicated, but the detailed explanation went largely over my head).

After the pipe has cured, holes are cut at the manholes, and a special device cuts the holes where domestic pipes are connected.

The worst section of pipe was from the manhole on the bank at the Glebe land, where the bypass pipes are currently removing the live sewage feed, and the manhole where the road collapsed and the new liner starts. This section is too weak and damaged to be relined, and so it will be excavated and replaced. It cannot be done in a single hit because of the trench depth in very unstable and sandy soil, so the job will be carried out in sections.

This picture shows the manhole that was within the main void. Looking back up the hill you can see the cones around the manhole where the bypass pipes and pumps start, and you can see where the tarmac has been removed to dig the trench.

The pedestrian walkway and bypass pipes are in the left of the picture The trench is being sheet-piled here ready for installation of the first length of new pipe. The "trouble" manhole is at the bottom edge of the picture. If this part of the works goes as well as hoped, it should not introduce any great extra delays, and the road should re-open towards the end of August.

Three more smaller voids have been found under the Glebe Cottage side of the road, but they will be repaired as part of the reinstatement.

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