Scanning a lift pit before a hydraulic ram went in

The brief

A waterfront bar in St Neots was installing a new hydraulic lift. Hydraulic lifts don’t hang from ropes at the top of the shaft, the car sits on a ram that seats into the pit, which means the entire lift load goes straight down into the pit base. Before installation, the installer’s engineer wanted to know what was in that base.

That is a structural question, not a fixing one. The installer needed the reinforcement in the pit slab and walls located before committing the ram, without drilling exploratory holes into the floor of a working venue.

On site

We surveyed the pit with ground-penetrating radar, scanning both the base slab and the surrounding walls. The pit was a confined, low-level working space in a live building, so access and setout were planned around the constraints, working down in the pit, scanning each face and the floor methodically rather than sampling and hoping.

What the scan showed

The survey located the reinforcement in the pit slab and walls, including the area of the base where the ram sits. That gave the installer’s engineer information on the base to work from, rather than an assumption.

As always, we were clear about the limits of the data. GPR locates reinforcement and gives depth-indicative positions. It does not measure strength or confirm load capacity, which stays with the engineer. Where the scan could not show something with confidence, we said so in the report.

The deliverable

The installer received a report documenting method, conditions and findings, with the reinforcement located against the pit, for the engineer to use in their assessment of the ram base.

The outcome

The engineer had scan data on the pit base before the ram went in, and no exploratory holes were drilled into the slab in a working venue.