Repurposing an abandoned sewer to prevent flooding

The historic market town of Louth in rural Lincolnshire has suffered with flooding for many years. A scheme to mitigate the flooding issues was designed by Anglian Water in conjunction with Danaher & Walsh and successfully delivered by Danaher & Walsh APS.

An abandoned combined sewer was identified as suitable for repurposing. This 1.3km sewer consisted of 600mm diameter concrete pipe. Its condition was poor, so extensive rehabilitation works were required.

Following cleansing, the sewer was fully inspected and graded. Several areas of near total collapse were repaired, some remotely using robotic cutting and others using small, localised, open-cut excavations. 

Following the repairs, the pipe was fully lined using a water-inverted liner and a hot water curing system. 

The newly repurposed sewer was then connected into the existing sewer system in both upstream and downstream positions. This sewer now provides extra storage capacity in storm and high-flow conditions

A scarcity of water supplies in the area meant that, ordinarily, tankers would be required to import water for use in the curing process. However, for this scheme, infiltrating groundwater was diverted to the boilers and used for the hot water cure. This method resulted in the saving of water resources and the elimination of many tanker movements.

The works areas were in a mixture of fields and areas of mature trees, with many ecological issues requiring assessment.