The project: Flood control for Mexico City
Why is Mexico City so threatened by stormwater? The ground on which the 20-million strong metropolis stands has sunk considerably over the course of many years. This is mainly due to the unique location of the city which was built in a basin surrounded by high mountains. This basin was once covered by a series of lakes that subsequently disappeared, hastened by efforts to drain the area. Another reason why the ground is sinking by up to 40 centimetres per year is overuse of the groundwater resources.
As a result, the most important natural drainage arm, the Gran Canal de Desagüe, is now lacking the necessary gradients at certain points in order to reliably divert the masses of water during the rainy season between August and October.
A completely new drainage tunnel was necessary. “When it rains here, it really rains,” emphasises Jens Mielke. At KSB, Mielke works as the company’s business developer in the field of waste water applications for Latin America and has been supervising the El Caracol project for the last three years. “Originally, the Gran Canal had a capacity of 80 cubic metres per second. By 2007 this figure had dropped to just 15 cubic metres per second. Since then, huge efforts have been made to raise the drainage capacity back up to 45 cubic metres per second.”
However, this capacity was not enough to prevent flooding in the city during periods of heavy rainfall, particularly in the east. Something completely new was required that would also accommodate the rapid growth of this megacity. The national water authority CONAGUA thus decided to build an underground drainage tunnel with a capacity of 150 cubic metres per second, the TEO. The first ten kilometres of the TEO are now in operation.
The particular challenge for KSB: At the end of this first section, the submersible motor pumps must raise up to 40 cubic metres of water per second to a height from which it can simply flow away under the force of gravity.
The customer: The national water authority CONAGUA is responsible for flood control in Mexico.
El Caracol is part of an ambitious project through which the national water authority CONAGUA is seeking to protect the metropolis against flood damage in cooperation with the administration of the Mexican capital and the State of Mexico.
Currently under construction, the Túnel Emisor Oriente (TEO) in the Valley of Mexico is one of the biggest tunnel structures of its kind. Measuring 62 kilometres in length and with a diameter of up to seven metres, the TEO drainage tunnel will increase the drainage capacity of Mexico City by 150 cubic metres per second.
The challenge: New canals and drainage pumping stations for protection
El Caracol is already the second drainage pumping station in the Valley of Mexico to be equipped with submersible motor pumps from KSB. Since March 2011, 24 KSB pump sets have been in operation at the La Caldera pumping station. “We were involved in designing the pumping station back then as well,” explains Jens Mielke. For El Caracol, KSB used the same design and further optimised it. Among other steps, the experts recreated the flow conditions of the pumping station using CFD simulation. This enabled them to rule out potential risks from the outset.
With the aid of test runs on a reduced-scale model of the pumping station, KSB’s engineers were also able to improve the final details. “The flow rates, for example, shouldn’t be too high or too low,” says Mielke. “The hydraulic development team had to come up with a concept that would slow down the force of 20 cubic metres of incoming water per second to ensure approach flow conditions that are manageable for the pumps. At the same time, certain minimum velocities had to be maintained in the waste water to avoid deposits of solid matter.”
The solution: El Caracol waste water and stormwater pumping station
El Caracol – the snail – is the name of the combined waste water and stormwater pumping station in which the 20 giant submersible motor pumps from KSB are in operation. The name El Caracol is reminiscent of the old canal system close to Lake Texcoco. Arranged in a spiral formation, the canals were once used for solar salt production. In June 2013, the president of Mexico, Enrique Peña Nieto, opened El Caracol in Ecatepec, Estado de México. Since then, pumps from KSB have been protecting Mexico City against flooding.
KSB pump sets handle up to 40,000 litres of water per second
The 20 submersible motor pumps are some of the biggest KSB has ever produced. Each unit has a drive rating of 1,150 kilowatts and weighs around 14 tonnes. KSB developed and produced the pumps and their motors in Germany. The pump sets were then transported by sea to Mexico, where they were received and installed by a German installation coordinator and a team from KSB Mexico.
In future, the water will be transported via the completed 62-kilometre Túnel Emisor Oriente to the Atotonilco water treatment plant, one of the biggest sewage treatment plants in the world. KSB was the obvious choice to supply the pumps for this new plant.
“The station has had its first rainy season without any problems to complain about. If we take the La Caldera pumping station into account as well, KSB can be proud of equipping two of the largest drainage pumping stations in Mexico.”
KSB’s business developer in the field of waste water applications for Latin America
Mielke is satisfied with the El Caracol pumping station which is now situated at an elevation of 2,200 metres. “I am personally very pleased that we have been able to justify the confidence placed in us. We’re not talking about standard submersible motor pumps here, but specially produced units that are seriously huge.”
Data I Facts I Figures
Customer: CONAGUA (La Comisión Nacional del Agua)
Employees: Around 17,000
Industry: Public authority