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Spotlight: Water Margin

Keeping Manchester supplied with drinking water was topmost in the minds of Bachy Solentache engineers during project involving Britain’s longest gravity-fed aqueduct.

The aqueduct provides the city with 20% of its potable supplies and is situated under a steep slope, 440m above the valley floor in the heart of the Lake District National Park.

The extensive slope remedial works needed a broad range of monitoring techniques to ensure that failure of both the slope and structure did not occur, and ultimately to determine the success of the remedial works after the project was completed.

A four-week outage period was programmed, which allowed work inside the conduit. To provide surface monitoring characteristics along the slope, robotic total stations CYCLOPS driven by SolData software and working in groups provided real-time 3D movements over a grid of monitoring prisms positioned over the surface.

The CYCLOPS units were fixed within the zone of influence and monitored their own position using reference prisms located on stable rock outcrops.

Vertical profiles of the slope were obtained using IPI strings installed within boreholes drilled directly into the hillside. To determine vertical conduit deformations, a 30m chain of horizontal in-place inclinometers were installed within the conduit.

To ensure that the c­onduit integrity was not compromised during the strengthening works a combination of strain gauges and crackmeters were placed at strategic points within the conduit. Induced vibration was considered to be a potential problem during the remedial works on this sensitive slope so portable geophones were also used around the conduit.

The data was acquired, stored and managed by a data-logging solution on site, which imported the information into SolData’s Geocope software.

These solutions provided United Utilities and Bachy Soletanche with real-time access to the monitoring data as well as the ability to run fully customisable reports. All data was then remotely archived at SolData’s head office in Maidstone.

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