SWELTERING CONDITIONS on London's Underground could be eased by using water from underground aquifers, it was revealed at a British Tunnelling Society meeting last month.
Speaking at 1 Great George Street, Parsons Brinckerhoff tunnel cooling programme integration manager Mark Gilbey said underground aquifers and soil in tunnel walls could help relieve what has become a 'tremendous problem' on the tube.
If a planned trial at Stockwell station in south London goes well, it could be adopted on a wider scale. The aim is to use a large subterranean reservoir of water with a temperature of about 13°C in the upper chalk.
A borehole will be drilled near to the station from which cool groundwater will be pumped through pipes leading to a cooling unit. Fans inside it will draw warm station air across it, lowering its temperature.
Thames Water stipulates that this water must be returned to its original source, so a separate borehole will be needed at least 100m away from the extraction point to inject the water, now up to 0.5°C warmer back into the ground.
A similar system is already in use at Victoria station where water is seeping into subsurface tunnels on the District and Circle Lines. A drain draws this into the cooling units, making use of it before it's pumped into the sewer system.
The water temperature here is 16°C and although its source is unclear, Gilbey said it is 'very close to drinking water quality'.
The team hopes this system can be adopted elsewhere and has so far identified two other stations where it might work.
Soil surrounding tunnel walls might hold another answer to the cooling problem. Gilbey said it's possible to use fans to cool down the underground network during winter and store this cold in the rst few metres of soil in tunnel walls.
Gilbey told NCE's sister title Ground Engineering: 'It's like building up a cooling battery which can be used during the summer.' However, this technique does have its limitations because the temperature of surrounding strata can never be totally controlled.
For the full story see the June issue of Ground Engineering