Little Gaddesden


Project: Little Gaddesden

Scope: Survey and remove structure by combined confined space and diving

Location: Gaddesden Borehole

In August 2017 we were commissioned by G-Stow for Affinity water to survey and remove a 5-tonne pump and rising main from 60m down a 2m diameter, 90m deep bore hole.

Following the initial CCTV/Sonar survey, we found that over half of the rising mains total 14m length was submerged and part of the pipe work had fallen to the bottom of the borehole.

The rising main was seated on two 800mm by 600mm cast iron ‘I’ beams and from the survey information it become clear that the only safe option for removing it from the borehole would be to remove the 10 x 80mm securing-bolts and remove the whole structure in a single lift.

It was clear that the project would require both confined space operatives and divers working under extreme conditions to achieve a safe and successful outcome. With no-proprietary equipment available we set about designing and building a unique safety cage for both the confined space and diving operation that combined surface supplied air & communications, back-up air supply, gas detection equipment, safety camera and lighting and built a bespoke 8-tonne portable ‘A’ frame lifting gantry.

The confined space operative wearing full surface supplied Breathing Apparatus and flame-retardant PPE, utilised hydraulic tooling and a Thermic Lance cutting rig to remove the bolts and ‘I’ beams and subsequently installed the chain strops in preparation for the lift.
When the rising main was successfully removed, we carried out the diving operation at the bottom of the 90m deep borehole to recover the fallen sections of pipework.

The project was completed on time, on budget and in the words of our Client, ‘carried out like a military operation’.

Testimonial: We have been working with Water Services Group for a number of years on some of our more complicated projects and we have found them to provide a service that is second to none.

On a recent project at Little Gaddesdon borehole they really excelled when they had to provide a confined space team, a dive team, 8-tonne lifting gantry and plant to remove a 10m long, 6.3-tonne manifold and risers from a 90m deep shaft, using a combination of confined space operative and divers deploying pneumatic & hydraulic tools and a thermic lance rig.

Our Client, Affinity Water were initially concerned about the safety element of such works, but following early project meetings their concerns were allayed by the professional approach to managing the risks and once the project was underway, the Client commented that they had never seen a project carried out in a more professional and military-like manner. We couldn’t recommend Water Services Group highly enough.

STOW PLCMark Farina(Contracts Manager)