Drainage Services Across Blaenau Gwent

Blaenau Gwent's housing was built for the iron and coal industry — long terraces stepped up steep valley sides at Ebbw Vale, Tredegar, Abertillery and Brynmawr, with drainage laid to suit nineteenth-century industry rather than modern rainfall.

Steep gradients cause two opposite problems. Where falls are excessive, water races away and leaves solids behind, so blockages form in the flatter sections at the bottom of the run. Where the valley floor flattens abruptly, everything that has been carried down the hill drops out at once. On top of that, much of the county is built on made ground, colliery spoil and reclaimed industrial land, which continues to settle and shear pipework at the joints. Combined sewers in the older terraces take roof and road water too, so intense hillside runoff surcharges the system within minutes of a downpour. Ochre and mineral deposits from old mine water can also scale the inside of pipes and gradually reduce their bore.

Jetting clears the deposit; CCTV shows whether the pipe behind it has been pulled apart by ground movement. Where it has, relining restores a continuous pipe without excavating a terraced street.