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LIQUID ASSETS

WATERWAY REPAIRS

This year British Waterways embarks on an extensive engineering programme to repair and maintain inland waterways.

Britain's canals and rivers support 54,000 jobs and generate more than £1.5bn in visitor income each year according to British Waterways (BW), which is responsible for a 3200km network of canals and rivers in the UK.

'A 200-year-old canal requires constant maintenance and this year will see an increased number of engineering works to improve the fabric of the historic working waterways, ' says BW chief executive Robin Evans.

More than £23M will be spent replacing 133 lock gates and repairing 64 canal bridges as well as undertaking structural works to a number of canal embankments, aqueducts and reservoirs.

Works taking place this winter include a £650,000 restoration of Dowley Gap Aqueduct on the Leeds & Liverpool Canal near Bradford.

This will strengthen the seven-span grade II listed structure and prevent the leaks in the canal bed that have been damaging its masonry.

Following installation of temporary dams, contractor Galliford Try will drain the aqueduct and install a new reinforced concrete canal invert on the canal bed to prevent further leakage.

The project will also address the movement and bulging of the aqueduct's spandrel walls as well as circumferential cracks and deep open joints in the masonry that have opened up on each span.

Site access is difficult because of the aqueduct's isolated location.

Where possible materials will be delivered by water.

To prevent future deterioration, vegetation around the structure will be cleared. This is necessary to prevent seeds dropping onto the aqueduct and the risks of root growth undermining its foundations.

The works, which have meant canal closure since November, will ensure that when it reopens in March the aqueduct will be removed from Bradford council's buildings at risk register.

March will also see BW beginning 10 weeks of leakage repairs and remedial works to Startop's End Reservoir which feeds the Grand Union Canal in Hertfordshire.

Repairs will ensure the reservoir, which has had to operate at reduced levels because of the undermining effects of the leakage, will be operating at full capacity in time for the start of this year's boating season.

A thermal survey in March 2005 concluded there was leakage across the 230m north west embankment when water in the reservoir was at capacity. If allowed to continue, this could lead to the earth embankment destabilising.

To reduce the risk of a canal breach, the reservoir has been kept 600mm below its capacity. However this has reduced the amount of water kept in the reservoir by 71,300m3.The project will include sheet piling along the embankment, underpinning of the concrete wall at the junction of the south west and north west banks and the refurbishment of a weir.

Startop's End Reservoir is within a site of special scienti'c interest (SSSI), so the project has been the subject of an environmental appraisal and requires consent from English Nature.

Contractor Morrison won the £630,000 contract, which is expected to finish in late April.

Elsewhere, Galliford Try is working on the Trent and Mersey Canal in Cheshire after BW engineers found sections of the canal had been sinking. This is the result of years of third party salt mining and brine extraction from the ground beneath the canal.

An assessment of the risks of the ground loss leading to a canal breach was undertaken. The £700,000 engineering works should mitigate the effects of a rupture with the installation of two sets of flood gates.

Should a breach occur, the timber flood gates would automatically shut, stopping water leaving the canal and flowing on to adjacent land. Most of the 338bn. l of water in the canal pound near Northwich would be retained.

Engineering works will begin with construction of clay dams at each gate site. Two concrete flood gate chambers will then be built and each set of flood gates craned into position.

Once the site is drained, pumps will maintain the water feed to the canal downstream which is vital not only for the continued leisure use of the waterways but for their fauna and flora.

The project is expected to run until the middle of March.

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