Sewer Surveys UK Ltd and NHTB Consultancy worked in partnership on a Flood Risk Study for Optimise (AMP5 framework provider for Thames Water). The mission was to ascertain the reason for the many flooding incidents in the district of Maida Vale. During heavy rainfall the sewers were surcharging and in turn flooding the basements of properties in the area. It was the job of Sewer Surveys UK Ltd to find out why the basements were flooding.

To capture the data and determine the reasons for the flooding we had to get in deep to the main trunk sewers that all the properties discharged directly into. This was a challenge in itself with the bustling environment Maida Vale is, side entry manhole chambers, deep and fast flowing sewers and also large diameter trunk sewers.

We surveyed almost 4,000m of London trunk sewers with remote CCTV survey equipment and floating CCTV equipment with pan and tilt facility, the sewers ranged from 300mm concrete pipes and brick egg sewers to 3000mm circular bricksewers. To accomplish most of the surveying we had to set the CCTV equipment up within the sewers due to tight access and side entry chambers, this meant carrying out confined space entry into the sewers.

Having completed the surveys we discovered that the majority of non return valves on all the lateral connections were seized open due to wear and rust on the valves, it was this that was causing the sewers to back up through each open lateral leading to the flooding of basements.

A full CCTV survey report was produced using Wincan V8 with an AutoCAD plan showing the route of the sewers and the flow directions. The job was completed over 2 days and 2 night shifts with minimal disruption to residents and businesses in the area.