Culvert Surveys for AECOM — Siston & Warmley Flood Defence Scheme

Consultant engineers AECOM needed the internal condition of two culverted watercourses assessed for the Siston and Warmley Flood Defence Scheme. Exjet Services surveyed more than a kilometre of culvert using steerable CCTV equipment and a confined space entry team, and delivered the data in four days against a five-day programme.

The brief

Exjet were approached by AECOM consultant engineers to carry out an internal survey of two culverted watercourses as part of the Siston and Warmley Flood Defence Scheme. The surveys were to be carried out using a combination of CCTV drainage survey equipment and man entry, in order to assess current silt levels — with a view to establishing whether the structures needed cleansing — and to record the structural condition of the tunnels.

All customer liaison, highways notices and site notification to the Environment Agency and other interested parties was undertaken in house by Exjet.

Tunnel one: 1,100m of bolted concrete

The first tunnel is constructed of 2100mm bolted precast concrete sections over a distance of 1,100m, with one intermediary access point. Exjet were tasked with putting together a safe system of work that allowed a perspective view of the entire tunnel.

Achieving that required a mixture of man entry and CCTV drainage survey equipment with 500m capability, and lighting adequate for a 2100mm culvert.

Relying on extensive previous experience in this field, Exjet assessed and planned the works to remove as much of the man entry as possible. By using steerable CCTV survey systems with wheel arrangements chosen specifically for tracking through heavy silt, it was possible to survey in excess of 450m from both the inlet and the outfall. That left approximately 200m to be assessed by CCTV assisted by man entry, because of the configuration of the intermediary manhole and the depth of silt in the unsurveyed sections.

The intermediary manhole connects to the main line via a major branch roughly 20m from the culvert. To complete the survey, Exjet mobilised a five-man confined space entry team alongside a two-man rescue team, allowing the CCTV system to be guided through the heavy siltation so the survey could be completed in full.

Tunnel two: an Armco steel arch at Siston

The second tunnel, at Siston, is an Armco steel arched culvert running approximately 200m. As with the first, the basis of the works was a structural and conditional survey using CCTV equipment, with man entry to complete the works if the survey could not be finished by those means alone.

The outcome

Both elements of the survey were carried out and completed over a four-day period, against a programme planned at five days to allow for weather. The collated information was passed to AECOM’s engineers for use within hydraulic models for flood risk assessment.

What we added

A concise and realistic system of work was submitted to the client, considering all risks and differing scenarios, to make sure the works would be completed as fully as possible. Comprehensive risk assessments and site-specific method statements were compiled and submitted alongside it.

Completed information was provided in both hard copy and through Exjet’s online viewing platform, allowing multiple users access to the survey data at the click of a button.

Culvert and confined space work of this kind sits within our commercial drainage services. See also who we work with.

Talk to us about a similar problem

Exjet Services has been solving drainage and sewer problems across Devon, Cornwall, Somerset and Dorset since 1986, with commercial and planned work right across the South West. Our engineers are directly employed and we are certified to ISO 9001, ISO 14001 and ISO 45001.

If you have a drainage problem that nobody has been able to diagnose, get in touch or ring 0800 328 6655 — answered any hour.