Water tunnel

Geothermal use of tunnel waters a beneficial way to avoid disposal... 

Table 2. Maximum disposable tunnel water flow rules far the Gotthard Rase Tunnel (Switzerland),...

Usually the outflow temperature shows no seasonal variations. Thus such waters represent an interesting potential for direct use, provided that potential heat consumers are situated at or near the portals. Contrary to the use of mine waters for space heating, as for example in Canada (Sanner 1993) or Germany (Bussmann 1994), where electrical energy is needed to lift the warm waters from the drowned mines to the surface, there is no need for pumps in the case of tunnel waters. 

In the following, the tunnel water situation in Switzerland will be outlined, utilization examples will be described, and the potential of deep and long tunnels in construction will be discussed. In the concluding remarks the prerequisites of a geothermal use of tunnel waters will be addressed. 

The use of energy from warm tunnel waters is most advantageous in the immediate vicinity of the tunnel portals, because long transport/distri-bution piping is a major cost factor. Therefore, the installed heating systems are all situated at the tunnel portals. In addition to five systems where warm tunnel waters are exploited, there exists also one installation (Grand St Bernhard), where the heat content of warm tunnel air has been utilized since 1999 (for locations, see Fig. 7). 

Furka railway tunnel. The outflow at the west portal amounts to 5400 L/min at 16 °C. The water is filtered and then piped to the nearby village Oberwald (canton Valais). There, an innovative system has been in use since 1991 (Rybach Wilhelm 1995) the tunnel water is piped to individual heat pumps, tailored to supply various types of buildings ( cold district heating ). A total of 177 apartments and a sports centre are heated, with an installed capacity of 960 kWt (some of the buildings seen on Fig. 8). 

The operating experience with all these installations is satisfactory to good only some minor technical improvements, for example, exchange of sand filters, became necessary. The flow rates and temperatures of the outflowing tunnel waters show little to no seasonal variation. Therefore, this zero-cost heat source can be considered as totally reliable and sustainable. 

Further investigations are needed to better specify the geothermal potential of the deep Alp-Transit tunnels. There are several factors that can influence the outflow rate and temperature of tunnel waters, and these need to be addressed and quantified (1) possible construction measures such as cement injections to seal fissures and cavities in order to prevent or reduce the water inflow at critical points along the tunnel ... 

Besides the technical prerequisites for a geothermal use of tunnel waters, there are also other tasks to be completed for a successful utilization. For example, the economic viability needs to be demonstrated for attracting and motivating potential consumers. Moreover, several administrative steps have to be followed to obtain all necessary permits. Nevertheless, the various operating examples in Switzerland demonstrate that all these tasks can be done, even with a relatively low speed of development. At a given location, the... 

Furthermore, there is still ample space for innovative solutions, especially to utilize the warm tunnel waters in summer time. The planned tropical greenhouse in Frutigen is such an example. Further options are spa-type establishments for wellbeing, fun and pleasure, aquacultures and the like. All of these applications are already being considered. 

The heating of the rock resulted in a significant increase in rock stresses in the vicinity of the FEBEX tunnel. Water pressures remained however essentially unchanged. The relatively... 

Air particulate samples were collected on glass microfiber filters in the Eisenhower tunnel on Interstate 70 under conditions designed to minimize partieulates other than those formed by the vehicular traffic passing through the tunnel. Water and volatile organics were removed from the samples by drying the filters at 45°C nnder vacuum for 18 h. The soluble organics were ranoved from the particulates by successive 18-h Soxhlet extractions with methanol, acetone, methylene chloride, and cyclohexane. 

Tunnels (water supply, rail, roads, metros) Chunnel (UK and France), Gotthard (Switzerland), Seikan (Japan), Moscow Metro, London Underground... 

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