Construction of Deep Flood Relief Tunnel Under Way in MexicoThroughout the years, the regional landslides that affected the banks of the Río de la Compañía in Mexico Valley reached annually up to 60 centimetres in certain areas, causing ground movements that damaged the river banks and problems to handle the volume of water.As a consequence of this situation, at the end of May 2000, despite the maintenance programme that Conagua was carrying out, the south bank of the river burst, downstream its crossing with the Mexico-Puebla highway, which caused severe floods in almost 1,000 dwellings that affected more than 50,000 residents in Chalco, Valle de Chalco and Ixtapaluca. The event was critical to the health and safety of the citizens. This also caused economic losses, the cut of traffic for three days on the Mexico-Puebla highway, the main communication link from the country's centre to its south and southeast, as well as damages to the agricultural production zone in the region, at the expense of the inhabitants in the eastern area of Mexico Valley.To avoid the repeat of a similar situation, Conagua carried out studies and prepared technical plans to give a final solution to the problem of the Río de la Compañía. It was decided that the best remedial work consisted in boring a deep water tunnel in the area where the landslides of the river banks made the circulation of water difficult and represented a risk for the population. BenefitsThe construction of the Río de la Compañía tunnel managed by the National Commission for Water (Conagua), in coordination with the State of Mexico government, will end with the risk of floods in Chalco, Valle de Chalco and Ixtapaluca, for the benefit of more than one million inhabitants in the east of Mexico Valley. This project will allow the population of this part of Mexico Valley to live peacefully, without the threat of rains causing flood damage to their families, houses and private belongings. Visit www.cna.gob.mxThe ecological, social and economic impacts of this project are significant, since besides avoiding economic losses, damages to possessions and health problems, it will improve the environmental conditions and the life quality of the population, by channelling the untreated waters poured into the Río de la Compañía which crosses a densely populated area. The tunnel will substitute the river, as rainwater and wastewater east of Mexico Valley, in the municipalities of Ixtapaluca, Chalco, Valle de Chalco, Nezahualcóyotl, La Paz and Chicoloapan, will drain through the tunnel from pumping station PB-12 to La Caldera pump station, that will be located at the confluence of the Mexico-Puebla federal highway and the river. Mexico's President Felipe Calderon on his visit to the Río de la Compañía tunnel Once the tunnel is completed, its drainage capacity will be 40 cubic metres per second. The project will generate 1,285 direct jobs and 800 indirect jobs. Tunnel characteristics The project is mainly comprised of a 6,777 m-long tunnel, with an inside diameter of five metres and outside diameter of 6.3 metres, and a pumping station with capacity for 40 cubic metres. Work on the project commenced on 20th June, 2006 and will be concluded in July 2008. The investment amounts to MXP1,423 million. The State of Mexico government will contribute MXP300 million while the remainder will be financed by the federal government, through Conagua. Construction will take place at three different places: the shafts, the segment plant and the tunnel, both for excavation and installation of the final lining. The tunnel is built at a depth of 23 metres and there are also four 12 m-diameter shafts for entrance, exit and handling of the machinery, a 16 m-diameter shaft and a 5 m-diameter shaft, at variable depths of 22 to 26 metres. The tunnel starts at El Cerro del Elefante and will end at La Caldera treatment plant at the crossing between the river and the federal highway. The water will enter in the tunnel through the first shaft and at the end of it, it will be pumped to be discharged to the natural waterway and continue to be channelled to Lake Texcoco. The tunnel is built by ICA by means of a 6.3 m-diameter Herrenknecht EPB tunnel boring machine (machine S-364). It is comprised of three sections of 1 x 2,688 metres, 1 x 2,119 metres and 1 x 1,970 metres. To date, approx. 1,150 metres has been dug. The cutterhead power is 450 kW (six engines of 75 kW). The total thrust is 29,000 kN. The cutterhead torque is 2,325 kNm. The laser guidance system is supplied by VMT. Click mx/19. Visit www.ica.com.mx, www.herrenknecht.com and www.vmt-gmbh.de The segmental lining rings are made up of six 25 cm-thick universal segments and a final concrete lining, 30 cm thick, will be cast in place. The moulds and segment plant are supplied by CBE Group of France. The plant was built locally from the designs of CBE Group. Sofrasar and local providers supply the rubber gaskets for the segments and rings. Visit www.cbe-tunnels.com and www.sofrasar.frThe geology is alluvium and clays, which consistency is soft to very soft, with high humid contents and variable thickness. As the TBM progresses, the dirt it excavates is fed through pipes in the back-up by pumps integrated into the shield. State of Mexico governor Enrique Peña Nieto and Mexican president Felipe Calderon visited the Río de la Compañía tunnel project on 17th July, 2007. Second stageSubsequently, a second stage will be implemented, in which the tunnel will stretch for an approximate length of 18 kilometres, crossing the municipalities of La Paz, Nezahualcóyotl and Chimalhuacán, to arrive at the confluence with the Remedios river and discharge at the Casa Colorada pumping station. The Río de la Compañía tunnel project forms part of Mexico Valley's sanitation programme. It is an integral plan for water and sewage that will require an investment of MXP36 billion in the next years, jointly financed by the federal government, the State of Mexico government, the federal district government and the municipalities.This scheme is divided into three parts: - the clean-up of waters through the construction of seven large wastewater treatment works that will treat 100% of sewage in Mexico Valley. - the reinforcement of the drainage system to prevent the risk of flooding, already imminent, and the construction of the east outfall tunnel and of four pumping stations that will allow in the future to drain 100% of rainwater in the city of Mexico and its conurbation for the benefit of its inhabitants.The eastern outfall will have a length of 60 kilometres and a diameter of 6.5 metres. Its capacity will be 120 cubic metres per second. Its cost will be around MXP10 billion. Read E-News Weekly 29/2007 & 26/2007.- the completion of the drinking water supply, through the development of new sources of supply that will help reduce the overexploitation of aquifers in Mexico Valley and improve the supply by reducing the water leaks, today of a little more than 50 cubic metres per second, which cause the exhaustion of the aquifers, cracks, landslides and disastrous risks for the city. 37/07.