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OTHER NEWS 14 May 2013

Wastewater tunnel will reduce flood risk for Mexico City's 20 million inhabitants

The Emisor Oriente tunnel will be a part of the new drainage system in Mexico City. Global consulting and engineering company Pöyry is working in the project, which will significantly reduce the risk of flooding in the city and in the surrounding areas.  When completed, the 62 km long Emisor Oriente will be the longest wastewater tunnel in the world.

Mexico City constantly battles against flooding

The sinking of Mexico City is a problem that goes way back in history for many years.  The valley of Mexico City used to have a lake system that started to be drained during the Spanish colony to stop the constant flooding, reducing humidity in the soil with its consequent compression.  Various methods to drain water from the valley have been applied since then, including canals and tunnels.

The rapid population growth in Mexico City has increased the need for water supply and resulted in more groundwater extraction. The water has been pumped from below the city, which has actually caused the city to sink. In the last 100 years, parts of Mexico City have sunk as much as forty-two feet.

Mexico City is puts a lot of effort to stop the sinking, which has already caused considerable damage to buildings, roads, and critical infrastructure. In some locations it has caused the sewage lines to become slanted - resulting in the lines running backward. Consequently, the city struggles with flooding during the rainy season. Emergency pumping stations have been built to maintain extraction capacity, but a major solution is still needed.

New 62 km long wastewater tunnel to add150 m3/sec extra drainage discharge capacity

Consequently, the construction of the Emisor Oriente wastewater tunnel (TEO) started in 2009, with the lead of the Federal Government.  TEO will provide an additional discharge capacity of 150 m3/sec to the existing drainage system, working together with the Emisor Central tunnel (main component of the Deep Drainage System). This will eliminate the risk of flooding. 

The Emisor Oriente wastewater tunnel is planned to work together with the Atotonilco water treatment plant which will reduce the need of extraction of deep water in the Mexico City Valley.  The local government of the City has also an extensive program to build aquifer recharging wells.

The Emisor Oriente tunnel is the most expensive single current project, with an investment of around 1150 million Euros. It will provide around 12,000 jobs during its construction, followed by the Atotonilco plant which investment is calculated in around 600 MEUR, providing around 17,000 jobs.

These kind of projects are significant for the future of Mexico. In addition to the flood prevention, they guarantee access to potable water, and support agriculture with proper irrigation, thus improving the quality of life for citizens in Mexico City region - Ricardo Murillo, Pöyry’s Country Head in Mexico.

The project is being carried out by Mexico's National Water Commission Conagua, which is also responsible for management of the tunnel. “Pöyry’s local expertise here in Mexico as well as experience in tunneling projects worldwide have been beneficial for the project”, says Francisco Leal Flores from CONAQUA.

The new storm-water drainage main tunnel will be approximately 62 km long and has a diameter of 7 meters. Along its length the tunnel will be connected to ground level by a total of 24 vertical shafts. The lengths of these shafts will range between 40 m and 150 m. The main tunnel will be excavated using Tunnel Boring Machines (TBM) machines, specially designed to work in the presence of high water pressures.

Pöyry’s role  

Pöyry has worked in the Emisor Oriente project since 2010, providing technical consultancy services during tunnel excavation and construction. Pöyry’s services include scheduling, risk management and monitoring the performance of the tunnel boring machines. Data from excavation progress and geological conditions is collected and analysed using 2DOC software application, also developed by Pöyry.

Underground projects always have risks and Pöyry’s main challenge is to identify and prevent them as well as set the best course of action if a risk is realised. 

Tunnelling and other infrastructure projects are becoming more complex, and Emisor Oriente is a good example of that. It requires a comprehensive and interdisciplinary evaluation for geological and geotechnical situations and risks. This is where we can utilise the know-how of our tunnelling experts as well as 2DOC software, which gives us reliable data during excavation. This saves time during the project and provides good basis for risk management and decision making - says Ricardo Murillo.