Prittle Tunnel


Project: Prittle Tunnel

Scope: To carry out a combined Lidar and CCTV survey of a 4.5km tunnel

Location: Southend On Sea, Essex

We were approached by Atkins consulting Engineers through our JV partner Reach Engineering & Diving Services (REDS) to provide a benchmark survey of a 2.5 metre diameter segmented concrete tunnel, which acts as a flood relief channel for the Prittle Brook.

Our remit was to survey the tunnel with millimetre accuracy to enable The Environment Agency to assess and fully understand the condition of their asset using a technology that would enable subsequent surveys to flag-up millimetre accurate changes.

With difficult and restricted access, a distance in excess of 1km between access hatch shafts and a 15 minute flash-flood warning a confined space manned-entry was not an option.

Our amphibious long-range, multi-task crawler was the only option for a survey with a 4.5km excursion range and an ideal platform for the market-leading Lidar system operated by our JV mapping company Infotec. Their system has a repeatable accuracy of –1mm.

In addition to Lidar, the crawler was fitted with low-light, high resolution colour cameras and high intensity variable lighting pods, mounted on a pan & tilt head to provide additional useful visual data.

Testimonial: The previous inspection was carried out by a confined space entry team. For this inspection, with remote operated technology, available today, we were keen to avoid the risks associated with undertaking a walkthrough of the tunnel. The crawler and CCTV provided very good quality results. The addition of Lidar provided a substantial further benefit for our Client, enabling future inspection results to be compared and checked for any signs of movement / changes. The work was carried out carefully and safely by a professional team, who were a pleasure to work with.

Colin Lee, Technical Lead and Project Manager