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Fleetwood Primary Settlement Tanks

Fleetwood WWTW – Part of this major sewage treatment works project required the construction of 4no 38m diameter circular primary settlement tanks. Owing to site constraints, it was not possible to access all parts of the site with conventional craneage, therefore, Special Formwork was asked to design a formwork system to construct each tank in 10 pours that could be moved using a straddle gantry traveller. Due to limited space between adjacent tanks, the access platforms had to be incorporated within the gantry and hinged upwards to permit the forms to be struck far enough away from the concrete face to permit cleaning after each use. After the initial setup, the forms were able to be struck and re-set in a single work shift. An issue with the piling on one of the tanks resulted in a delay of approximately one month in starting the work, so the second set of forms and gantries was procured. As a result, all four tanks were constructed almost 2 weeks ahead of schedule.  The main contractors were KMI Plus – a joint venture between Kier, Murphy and Interserve.