Sewer Surveys UK Ltd and Bridgeway Consulting worked in partnership to carry out a CCTV inspection survey of a heavily silted culvert that runs directly under the Network Rail and London Underground.

The culvert is a brick arch with a natural invert and is approx 75m in total length with a 45 degree bend half way through. The initial enquiry was to carry out a CCTV inspection survey of the culvert with has good access from a car parking area. The culvert was approx 3000mm wide and 2000mm high. On arrival at the site we discovered that the culvert was 50% full of silt and using the CCTV equipment we were able to zoom in almost 50m and found that the silt carried on all the way through. We achieved no survey with the CCTV equipment. On our second visit to the site we took a full man entry confined space entry team supported by a rescue team on standby, this was almost fruitless as the gas detectors alarmed just 6m into the culvert. Due to the thickness of the silt we were struggling to walk through the culvert even with full breathing apparatus. This culvert required surveying urgently and with cleaning the culvert not an option at this point we had to come up with a method to complete a survey of the culvert somehow?

Our answer…

We decided to strap the CCTV equipment to a Kayak, and to also strap a high pressure jetting nozzle fed from a jetting machine to the bottom. When we powered the jetting nozzle it created rear facing pressure which pushed the Kayak through the culvert and floated over the silt. We managed to survey the entire culvert at a moderate speed using this method.

A full structural report was issued to the client on completion.