Broxbourne white-water course

Olympics Watch - Eton Dorney Lake

In the build-up to London 2012 Olympic Games, E&T looks at the Olympic course for rowing, canoeing and kayaking

The 2012 Olympics flat-water events will be held at Eton Dorney Lake. Fourteen rowing, canoeing and kayaking competitions with 550 athletes and four Paralympics events for 108 athletes will take place.

It was perhaps appropriate that Eton, with its long rowing tradition, should be the venue. A group of Eton College teachers had a vision of creating a world-class rowing course away from the impediments and distractions of the Thames. They had 400 acres at hand and in 1996 began to excavate a 90-acre lake suitable for rowing.

In the next ten years 4.5 million tonnes of sand and gravel were dug out, and – along with about two million cubic metres of top and sub soil and almost 600,000 cubic metres of clay – were transported to a collection point two miles away by a long conveyor belt.

Initially, Eton College spent £17m to develop the site, but about £8m was reclaimed for the extraction of aggregates. Even from the earliest days, the site was conceived to be environmentally friendly. The lake holds 1.6 million cubic metres of water, and Ivor Lloyd, the managing director of Eton Rowing Centre, is determined to ensure that the quality of the water is kept at a high level. Lloyd stresses that the water for the lake does not come from the Thames, but from a natural underground aquifer, which also acts as a filter.

Weeds, though, are a problem. Lloyd explains that climate change has caused a growth of weeds in waterways of Northern Europe. The main method of getting rid of them is a 1.2 tonne plough dragged along the bottom; but other, perhaps less conventional, methods are employed, including an indigenous carp, which feeds on the vegetation it finds on the bottom and barley bales. The theory is that, as the barley decomposes, it slowly releases hydrogen peroxide which inhibits the growth of algae – a problem at the Beijing Olympics.

Flat-water races at Eton

The Olympic course is a straight 2,000m, but the Lake extends to 2,200m because space is needed at both ends. Up to six boats race at one time but two extra lanes are included so that crews in the outer lanes are not disadvantaged by wash from the bank. A minimum depth of 3.5m is stipulated for best performance; here it has been dug to 4.5m. The lanes are buoyed and 13.4 m apart to give necessary clearance.

There has to be a return channel for boat movements to the start and this must be separated from the main course by an island. This 'return channel' is five lanes wide in places and has a minimum depth of 2.5m. A new cut-through between the course and return lane has been constructed and a new 50m bridge, linking the two sides added.

The facilities were successfully tested when the World Rowing Championships were held there in 2006. Then, 1,270 competitors took part – far more than the number competing in the Olympics. However, the International Rowing and Canoe Federations asked for additional improvements.

Ann-Louise Morgan, London Olympic Organising Committee rowing manager, explains: 'The widening of the entrance to the return lane will ensure safe access for warming up and cooling down crews during Olympics and Paralympics, and the new 50m span bridge will aid vehicular access to and from the return island and create a segregated pedestrian walkway to separate 'Olympic Family' [the combined organisations, broadcasters and athletes that make the Games happen] from vehicle movements. The access road, running along the south side of the venue, will provide a dedicated Olympic Family route into the venue segregated from spectators.'

White-water races at Broxbourne

The venue for slalom white-water events is Broxbourne, Hertfordshire, where a new course has been constructed. It is a slalom course for canoes and kayaks – Kayak 1 for men and women and the Canoe 1 and 2 for men.

White-water events are more dramatic than the classic flat-water boating. One-person kayak and one- and two-crew canoes launch themselves downhill into frothing, bubbling, seething white water.

Andy Mattock, of the Canoe England Management Team, who helped design the course, said that at first a 1:10 scale model was made for the final design and preliminary work. Foundation works were completed on schedule, with more than 500 concrete piles driven up to 16m into the ground to form the foundations of the venue, facilities building and slalom courses. Over 150,000m3 of material were needed to form the canoe course embankments and the landscaped features of the venue. Some 10,000m3 of soil were excavated to create a lake covering an area of 10,000m2, with 25,000m3 of water extracted from a borehole north of the site. Olympic events are held over 300m with a drop or 'head' of 5.5m from the top to bottom of the course. There is also a 160m intermediate course for training and for novices and other competitors; this has a drop of 1.6m. Mattock says originally courses were horseshoe-shaped but they are now more of a triangle, so that spectators can view the events from conveniently placed grandstands.

White-water turbulence

Turbulence is the essence of the sport and it is generated by two pumping stations: one for the Olympic course and the other - the intermediate. They run independently of each other, so one course can run at a time, or both courses can be run together.

For the Olympic course, there are a total of five pumps, located in a pumping house. It will use four of the pumps to circulate water, with one pump on standby as a reserve and could be run on three of the five pumps in legacy, reducing the energy required.

The main Olympic slalom course will be served by Flygt PL 7121 350kW axial flow pumps, with a maximum pumping capacity of 15m3 per second. Each pump is made of cast iron with a dynamically balanced bronze propeller. The intermediate course houses Flygt PL 7121 150kW axial flow pumps, which create a slower flow rate suitable for beginners, family days out or school children to enjoy.

After a run, boats are recycled by a conveyor belt and lifted back to the start.

Obstacles

The introduction of obstacles ensures the course is challenging enough for top competitors. Constructed of concrete sprayed on to reinforced earth, some sides of the course are vertical and others sloped or curved to create interesting and challenging features.

These features are intensified by gates and obstacles. The gates, 62 of them, are in fact metal poles suspended from overhead wires. Touching gates is penalised, unlike the Alpine skiing slalom, and rowers have to stop and paddle themselves back upstream, against a hefty flow, to negotiate gates. They also have to avoid obstacles which create eddies and hazards.

The 1,200 obstacles are made from metallocene-based super-linear polyethylene. They are fixed in a track embedded in the concrete bottom and can be moved up and down the course. These obstacles can be configured into a variety of shapes needed to create eddies above or below a feature and make standing waves larger and glassier.

The course is pulled together with a pumping house and a building, housing a reception area, a café, changing rooms, admin offices and spectator viewing facilities, storage, and water pump/filtration plant. During the Games, temporary seating will be installed around the venue for approximately 12,000 spectators

Colin Naish, the Olympic Development Authority Project Sponsor, is conscious of the need to reduce the amount of energy for the operation. He says they have reduced the height drop of the courses to save energy, are using pumps for both courses, capturing and reusing heat from the pumps to heat the venue buildings; providing two flexible courses where only one needs to run at any time. Water from both channels is being recycled and fed back into the lake. The ecology of the area will be helped, he says, by extensive new landscaping, plants and wildlife habitats.

Legacy

The Broxbourne Rowing Centre is owned and managed by Lee Valley Regional Park Authority (LVRPA) as a sporting and leisure facility for canoeing and white-water rafting, as well as a major competition and training venue for elite events. Derrick Ashley, chairman of the LVRPA, is thrilled with the progress made: 'Tickets are now on sale for white-water rafting, and from April this year members of the public can experience white water on the same course that will be used by the world's best athletes.' *

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