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Educational Information
Architectural and Building Specification
The construction brief for Ponds Forge required completion of the building for the summer of 1990. This would give the centre a period of acquaintance before the official opening. The £42 million centre was officially opened on 12 April 1991, just 31 months after construction began.
Erection of the steel roof was the key to meeting the construction deadline. The roof trusses were welded to cast steel-pinned nodes at the crown and eaves of the roof. Cast steel was selected because it made it possible to achieve an elegant joint from the complex geometry. The shape was designed to provide direct load paths, to give a castable shape and to minimise weight. A cup and cap arrangement at the sockets allowed the trusses to be lowered directly into position. The whole roof was covered in an insulated sandwich-type construction, clad with aluminium panels for acoustic absorbence. The system allows three complete air changes per hour and has been integrated into the roof, leaving the impressive structure to appear air duct free. The system is based on the wet and dry duct principle. Supply air is input through ducts along the pool hall roof, allowing warm, dry air to be distributed throughout the underside of the roof. The dry air is then distributed to the lower area of the hall, suppressing the humidity at pool level. The return air is removed through a dry air duct, leaving the air and pool water separate. This new method of separation ensures humidity levels are kept to a minimum. Energy use is minimised by modulating the re-circulation of the air and the use of a heat recovery coil for efficient heating.
Water Treatment
Ponds Forge's swimming pools contain over 6.5 million litres of water and are heated using Sheffield's pioneering heat and power scheme. Hot water is supplied directly from the city waste incineration plant. The temperature is further raised, on site, to the required temperature of 29°C for public swimming and 28°C for international events. The water treatment system can treat over 45 million litres of water per day. Separate water treatment systems are used for each pool, as each pool has a different volume of bathers and requires varying levels of water treatment.
Competition Pool - Water turnover rate is 3.6 hours. The primary disinfectant is ozone gas generated on site with a free residual chemical of chlorine gas set at 0.75ppm. This method of treatment was employed due to the high levels of users in the pool. Ozone has lower levels of irritants and reduced toxicity of water than traditional methods of water treatments. The system is also more efficient than traditional treatments, as ozone offers a more rapid cleaning system against organic contamination.
The water is circulated into the pool using a series of channels along the full length of the pool floor. Additional inlets are exposed when the bulkheads are moved forward. This all ensures that the water is introduced equally, ensuring excellent circulation and therefore equivalent conditions for competitive swimmers.
Diving Pool - Water turnover rate is 5.3 hours and a more traditional water treatment system is used - free chlorine set at 1pm. Ozone was not adopted because of the lower bather numbers. However, the diving pool water may be passed through the ozone system as and when required. The diving pool also has a water bubbling system to assist diving. This either breaks the diver's fall by releasing huge quantities of air, or acts as a sighting aid in releasing a fine stream of air to break the surface.
Leisure Pool - Due to the high volume of users in the pool, the average water turnover rate is a low 1.3 hours. The five zones within the leisure pool require the same level of water treatment, but at varying rates. Similar to the Competition Pool, ozone treatment is used but each separate zone has an individual supply and removal of water.
Chemical Treatment and Safety - The large quantities of chemicals on site are monitored using the latest safety guidelines and far exceed these in air monitoring for leakage. Each chemical has its own store and trained staff ensure the safe use of all treatments. A typical delivery of the necessary chemicals for treatment would consist of 1 thousand litres of Poly Aluminium Chloride, 1 thousand litres of calcium chloride, 3 tonnes of sodium carbonate, 1 tonne of sodium bicarbonate and a dozen cylinders of chlorine gas. The chemical system control at Ponds Forge is of a standard not previously seen in this country. A single programmable computer receives inputs from each of the three plants and through level analysis, controls the chemical and pH levels in the water. Each value for each plant is recorded automatically every five minutes and stored on disk monitoring analysis.
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