The environmental impact of tezontle extraction

The ongoing exploitation of tezontle mines in Texcoco could have devastating effects on the environment

The environmental impact of tezontle extraction in New Mexico City Airport
For months, the region’s inhabitants have seen tenths of trucks carrying this material from nearby mines, which according to official figures, shouldn’t be more than 100 in a 50 kilometer radius - Photo: Emilio Fernández/EL UNIVERSAL
English 22/09/2018 17:02 Berenice González Durand Mexico City Actualizada 17:04

In order to build over the lacustrian soil of the Mexico basin, the Aztecs had to learn to use tezontle since ancient times until it eventually became one of the area’s favorite construction materials to date. The terrain is surrounded by three mountain ranges: the Sierra Nevada, the Sierra de las Cruces, and the Sierra del Chichinautzin, which provided builders with the perfect building material for these lands.

In Teotihuacán, for example, tezontle became one of the most common materials for fillings and upholstery in the ancient people’s buildings along with other materials such as adobe, tepetate, and other sedimentary rocks extracted in the proximity of the Mexico Valley.

In colonial architecture, tezontle was of equal importance to solve some of Mexico City’s most pressing architectural challenges.

Tezontle is an igneous rock. Its volcanic origin can be perceived in its solid yet light consistency. It has iron dioxide components and although it holds in heat, it is not permeable nor insulating. This material is still one of the most utilized rocks in our country’s construction industry, particularly in the basin area, since there are plenty of mines for this material’s extraction.

Tezontle plays a very important role in the construction of Mexico City’s New International Airport (NAICM). For months, the region’s inhabitants have seen tenths of trucks carrying this material from nearby mines, which according to official figures, shouldn’t be more than 100 in a 50 kilometer radius, but the rising demand for this material has brought upon the creation of many more mines offering construction materials.

This should come as no surprise since, in order to level all 12,355 acres for the construction of airport runways, 50 centimeters of tezontle need to be injected in the land. The airport group also indicated that a 1-meter deep layer was needed for this type of terrain. It is estimated that the project will require around 30 million cubic feet of tezontle during the first stage.

The production of stone aggregates is broadly distributed in the country, mainly in urban development centers; however, many of them lack proper mining and soil restoration methods. According to the Ministry of Economy, some of the main problems detected in the sector are the development of human resources, as well as a lack of adequate technologies that may optimize, quantify, and protect the resource extraction, as well as the environment at hand.

Before any material extraction is conducted, miners are legally bound to issue an Environmental Impact Assesment (MIA), which must include actions for the restoration, recovery, and maintenance of environmental measures that might cushion the impact of their mining activity. However, nothing could be further from the truth. Between momentary clauses, mining activities continue without restriction.

Environmental omissions

According to local reports, many of the mines that have been working in the valley for years without proper supervision have considerably increased their activities, while new unlicensed mines have been acting without permits of any kind, offering materials at the expense of mountains in the Tezoyuca, Texcoco, Acolman, and Teotihuacán municipalities near the NAICM project.

In the opinion of David Delgado, a specialist in soil biology who has conducted research about environmental impact in the lacustrian area where the New International Airport is being built, the deterioration of natural resources in the area has escalated since the construction began.

The also professor of the Agroecology Department at the Autonomous University of Chapingo (UACH) has pointed out that one of the main problems with the mineral extraction and depredation that the mountains surrounding the basin have suffered is that it also affects groundwater recharge: when removing large amounts of this material, water bodies are deeply affected.

Delgado explained that there are two ways in which water reaches land through rivers and basins: surface and groundwater flows. With the extraction of minerals from nearby mountains, water infiltration is reduced considerably. “They are also affecting the availability of the hydrological resource because the airport is absorbing everything, including the residual reserve. All nine rivers in the valley’s highlands are being affected,” he stated, adding that when water circulation is restricted, the overall humidity in the environment is also reduced. “The problem is that the MIA presented by the Airport Group does not address these issues that will probably also contribute to an increase in Mexico City’s pollution levels.”

Recently, the College of Civil Engineers of Mexico spoke in favor of the construction of the new airport, since they deemed that it had “the best technical aspects and positive effects in the national economy.” However, specialists have agreed that long-term solutions must be sought to regulate the water systems of the Nabor Carrillo lake, and the project developers must develop a deeper geologic and geothermic analysis that might help mitigate the environmental, ecological, and hydrological problems regarding the construction of NAICM.