Team GB delivered during the Olympic Games on their medal target, but what about water use? Does the claim of “the greenest games ever” hold up under scrutiny? The goal was a 40% water saving “compared to 2006 industry standards”, a target that, if achieved, would be impressive. When the Olympic Park Water Strategy report1 stated that: “…the Park in legacy mode is expected to exceed this target with a total 57% saving in water consumption”, you could almost feel the nation’s chests swell with pride. However, just as the mantra “delivered on time and on budget” falls apart when you realise that the budget for the Games was increased to £9 billion from the original £2.4 billion, predictions of reduced water consumption also need to be analysed more closely.
The 40% target
In 2006, WC flush was 6 litres maximum, urinal controls were mandatory, and taps in public washrooms were already time controlled, so a 40% reduction would require alternative sources of water as well as efficient appliances. The preferred specification for appliances was 4.5 litres single flush WC, fan assisted waterless urinals, PIR operated taps at 5 litres/minute and showers at 9 litres/minute. All venues installed low flush toilets, and low flow showers and taps as recommended in the design brief, but the Velodrome and Aquatics Centre opted for flushing urinals. The Velodrome and Handball Arena installed rainwater harvesting and the Aquatics Centre installed backwash recycling. Rainwater harvesting is estimated to reduce the Velodrome’s potable water demand by 20% and predicted to generate a potable water saving of 530m3 a year2. (However, with just 25m3 of storage and the fact that the stadium will be used so intermittently after the Games, this figure seems optimistic to me.) Recycling the filter backwash water for WC and urinal flushing is estimated to reduce water consumption in the Aquatics Centre by three per cent3.
Where was the water used?
It was estimated that water consumption up to and during the Games would be 361 Mega litres (Ml)4. Post Games the figure is 5,735 Ml over the remaining 24 years design life5. This meant that 6% of total lifetime water use would be during the Games. How that requirement for water was broken down is very interesting. I had assumed the greatest demand would be WC and urinal flushing from the estimated 3.7 million visitors, closely followed by the Aquatics Centre. But in fact, the Olympic Park Water Strategy estimated water consumption to be as follows: the Combined Cooling, Heating and Power Plant at 26.9%, Eton Manor at 15.6%, 7.7% for the Aquatics Centre and 7.5% for establishment irrigation leaving just 14.5% of water requirement for the remaining venues on the site which included the 80,000 capacity Olympic Stadium and the Press Centre.
I hadn’t even considered the process water requirement for the CCHP plant, but it made sense once highlighted. But Eton Manor, what was happening there? And why was so much water required for irrigation when most of the park was planted with wildflower meadows?
Water based hockey pitch
Hockey is played at Eton Manor on a water based pitch. Water-based synthetic turfs enable the ball to be transferred more quickly than sand-based surfaces and are less abrasive so reduce friction burns, but require a lot of water as the pitch is flooded with water before the start of every match to a depth of 3mm. With a playing surface of approximately 6,000 m3, and top up required at half time, water use averages 26 m3 per match. Also, the pitch has to be kept wet constantly and, to prevent the growth of algae, hydrogen peroxide is added to the water. As the Intentional Hockey Federation themselves (back in 2006) suggested that hybrid pitches (sand and water based) would be preferable because of the very high water consumption of water based pitches, it is a pity that a hybrid pitch was not specified for the 2012 Games.
I was surprised at such a high requirement for irrigation. The wildlife meadows on the Park require establishment irrigation for two seasons, (which is not the case in other projects I have been involved with) whilst the trees require irrigation for the first three to four years. All irrigation uses water from the Old Ford Water Recycling Treatment Works. There are a lot of green walls around the park which require permanent irrigation, and although drip irrigation is the preferred delivery method throughout the Park for all the planting, using an industry standard approach is a missed opportunity. If the irrigation system was combined with soil moisture sensors then at least the unprecedented rains would have reduced the requirement for watering.
And the result is…
There are no figures to back up the 57% claim, so we will disqualify it. For the 40% target, 18% is estimated to be met by water efficient appliances and the remaining 22% by Old Ford using treated sewage from the northern outflow sewer6. Old Ford will provide a minimum 46 Ml (46,000m3) of treated water a year, and as the first direct reuse of waste water in the UK, it will be interesting to see how it performs, particularly in regard to the amount of energy it uses per m3 of water supplied. Water consumption on site during the construction phase seems to have been ignored which (if that is the case) is a cop out. So certainly not a gold medal, but as the feel good factor is still in the air I shall go for bronze.
- Learning Legacy: The Olympic Park water strategyLearning Legacy: The Olympic Park water strategy
- London 2012 Learning Legacy Rainwater harvesting at the velodrome
- London 2012 Learning Legacy – reducing the aquatics centre water consumption
- One Mega litre is 1,000,000 litres or 1,000m3
- 5,735Ml over 24 years is an average of 239 Ml a year. I assume that the bulk of it will be for the CCHP plant and the 2,818 new homes that will be built on the site, although no details were given in the report.
- Though if the CCHP plant and Eaton Manor hockey park are taken out of the equation, the reduction from water efficient appliances increases to 33%.