Robbins TBM Excavates Talave-Cenajo Aqueduct Tunnel in SpainThe objective of the Talave-Cenajo water transfer tunnel in Castilla La Mancha, southeast Spain is to ensure that people living in the Murcia and Alicante provinces receive water of better quality than now. From time to time, the water quality almost exceeds the authorised tolerance limits due to the fact that the water gets loaded with salt and sulphates as it crosses a section of the Mundo river. Different studies have correlated the poor quality of the water that people consume with the prevalence of determined renal illnesses. The tunnel features a total length of 7,630 metres, an outer diameter of 4.4 metres and inner diameter of 3.5 m. It is located in the Lietor municipality, at some 20 km from Hellin and 65 km from Albacete. A Robbins TBM 1111-234 belonging and operated by SELI, brought from Italy and dubbed 'Fuensanta', cuts its way through limestone, marls and clay under the Sierra de Morron to connect the Talave and Cenajo reservoirs, implementing a thrust of 27 tonnes. It is a 220 m-long double shield TBM. The cutter head is equipped with Widia tools in tungsten carbide. Since December 2006, already 1,100 metres of tunnel has been completed, at a rate of 30 daily metres. A laser guide keeps the tunnel within the correct alignment. It is controlled since a cabin in the TBM back-up. The lining is comprised of four precast concrete segments. Drilling is carried out in the Cenajo-Talave direction, with a very slight gradient. The tunnel has been designed so that water circulates by gravity without the need to be pumped, which limits its transportation. There will be water valve chambers at the entrance and exit of the tunnel. Visit www.selitunnel.com The Talave-Cenajo water transfer tunnel is one of the most emblematic projects to optimize water supply to the local population, but the Ministry of environment had to sort out a hard conflict with the government of Castilla La Mancha, who stopped the works twice. In fact, the stringent restrictions imposed by the government of Castilla La Mancha have limited the tunnel's conveyance capacity, allowing just water in the tunnel for human consumption but not irrigation. The consequence was that the proposed initial diameter of the tunnel, to channel a maximum of 60 cubic metres by second, has been reduced to 3.5 metres and its transfer capacity is six times lower. Click es/78 to learn more.Therefore, the tunnel will not have sufficient capacity to channel the maximum volume of water possible each year from the Tagus, both for drinking and irrigation. The volumes transferred from the Tagus source for watering will continue to be transferred through the same system as now: from the Talave to the Mundo river, then through the Camarillas reservoir and finally to the Segura river in Calasparra. This will also avoid that an important section of the Mundo river loose any ecological volume, supplied precisely by water transfers from the Tagus. For AcuaSegura, the owner of the project, the tunnel is a real bypass between the two reservoirs to better control the water flows, reduce the impact of floods and remedy the insufficient storage capacity of the Talave reservoir. The volumes from the Talave reservoir will discharge in Rambla del Algarrobo, two kilometres from the Cenajo tail. Visit www.acuasegura.es/obras/a1.htmThe contractor is Dragados, who subcontracted the tunnelling works to a JV of SELI and Jäger. The work supervisors are Prointec and Ingeotec. Dragados rents the TBM and also contracted 16 SELI operators out the 100 workers employed at the site. The budget amounts to EUR36.8 million. The project is scheduled to end in February 2008. Visit www.dragados.com, www.prointec.es and www.ingeotec.com 11/07.