George Leslie Ltd

Key Facts

  • Client: Scottish Water Solutions 2
  • Engineer: AECOM
  • Conditions of contract: NEC 3
  • Contract value: £2,200,000
  • Duration of works: Nov 2012 - July 2014

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Wastewater Treatment Works

Drongan Sewage Treatment Works

Drongan STW is an existing operational Works in the south east of Ayrshire which despite the implementation of extensive temporary improvement measures, had continued to experience SEPA discharge consent failures into the Waters of Coyle which bounds two sides of the works and is popular fishing waters.

This project comprises an extension to the existing works to provide a permanent solution.

The main construction elements included:

  •  Twin-cell x 3 lane 7m deep aeration tank, anoxic zone to overflow weir.
  •  Two 9m deep, 10.3m diam final settling tanks
  •  Distribution and discharge chambers with ancillary connecting pipework
  •  Returned & Surplus Active Sludge and Scum Chambers
  •  MCC kiosk, base and MEICA control systems

The construction activities were undertaken within the constrained confines of the existing works which remained fully operational throughout and key features included:

  •  Extensive use of pre-cast columns and panels for the aeration lanes and FST walls
  •  Self-cleaning GRP, internal, launder channel
  •  Extended PC wall units providing track for the scraper bridges
  •  Retention on-site and re-use of 12,000m3 of excavated material
  •  Top PC segment for each FST acts as 1.0m high barrier around tanks

During construction, careful management of the retained earthworks arisings was undertaken and a filtered site drainage system installed to ensure silt-free site run-off into the river was maintained. Essential to the progress of the work was maintaining a good working relationship and ensuring close cooperation with SW’s operation of the existing facility and the subsequent integration of extended works.

The project was also registered with the Considerate Constructors scheme, recognising the close liaison and working relationships which were developed within the community.


News updates


The overall project involves the off-site fabrication and installation of a new linkspan structure at Oban Ferry Terminal for client Caledonian Maritime Assets Ltd (CMal).

12th February 2019

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GL return to the Sound of Kerrera

GL making a return visit to the Sound of Kerrera off Oban, to undertake substantial repairs to the breakwater which suffered collision damage following an altercation with a workboat earlier this year.

14th December 2018

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Polmadie Bridge official opening……..

Michael Matheson MSP and Cabinet Secretary for Transport, Infrastructure and Connectivity covered all his portfolios at the official opening of the new Polmadie Footbridge giving pedestrian and cycle transport access,

18th September 2018

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George Leslie Ltd, Blackbyres Road, Barrhead, Glasgow, G78 1DU  |  |  +44 (0)141 881 9131