The construction and maintenance of dams require on-site work, which entails additional time and costs. For this reason, Sacyr Maintenance, in collaboration with Sacyr Holding, is working on 3D dam modeling using Pix4D software, which generates digital twins from drone imagery.

"We designate the area for the drone to fly over, and it captures overhead images along the entire path, scanning the dam's entire surface. This enables the creation of digital models with precise distance measurements," explains Gabriel Palacios, Prevention officer and Director of Drone Operations at Sacyr.

"For example, deteriorated walls with cracks can be dangerous to inspect up close. The drone follows the wall and captures a composite photograph, similar to an orthophoto but aligned with the wall, providing high-definition imagery to identify structural deficiencies. The drone can fly very close to the dam, and the closer it gets, the more detail it captures," Gabriel adds.

The digital model allows for the mapping of terrain topography and structural features, volume calculations, measurements of all visible elements, and comparative studies of different digital models taken at various times.

"Having a digital model provides a 3D-scale representation of the dam, similar to a physical model, where we can visualize, measure, and plan necessary work. This approach offers a wide range of possibilities while reducing time and costs compared to traditional methods," explain José Luis Barragán and Sergio Maestre, Head of dams O&M at Sacyr Maintenance.

Multiple Advantages

The key benefits include time savings, cost reduction, and improved safety. Often, small measurements are needed to determine an element's dimensions. Without an accurate digital model, this would require an on-site visit to the dam, which is often located in remote or difficult-to-access areas.

This technique is currently being used for dam modeling, although similar methods have long been employed in topography for land measurement and stockpile assessment.

3D modeling has already been implemented at the Linares del Arroyo (Segovia), Cazalegas (Toledo), and Estremera (Community of Madrid) dams. The goal is to extend this initiative to all dams under our maintenance program.

ISABEL RUBIO ARROYO | Tungsteno

The Salt Cathedral is undoubtedly one of the most remarkable places in Colombia. True to its name, it is constructed entirely from salt, but that’s only part of its allure. Situated 180 metres below the surface, it features a labyrinth of tunnels and massive salt-carved crosses.

In this piece, we explore the process behind its construction and uncover the secrets hidden within one of Colombia's greatest works of engineering, celebrated as the country's first wonder.

The spiritual refuge of miners

The Salt Cathedral is located in Zipaquirá, a picturesque mining town near the capital, Bogotá. To access the site, visitors pass through a long tunnel lined with eucalyptus logs and illuminated by green lights, adding to the mysterious atmosphere of the place. As you proceed, you enter a series of caverns and chambers adorned with majestic crosses carved in salt and illuminated by coloured lights that lend the space a mystical touch. The cathedral features three central naves symbolising the birth, life, and death and resurrection of Christ, along with an enormous basilica dome.

The indigenous Muisca people were the first to discover these salt deposits more than six centuries ago. Later, Spanish conquistadors arrived in search of El Dorado. "Instead of a city of gold, they discovered a city of salt," Luis Alfonso Rodríguez Valbuena, former mayor of Zipaquirá, told The Washington Post. In its early days, this cathedral was much more modest. Miners initially prayed in a small sanctuary built in the 1930s.

In this humble sanctuary, they prayed to the Virgin of the Rosary of Guasá, the patron saint of miners, seeking protection from toxic fumes, explosions, and the many dangers they faced daily while extracting tonnes of salt. “The work was very dangerous,” Juan Pablo García, the cathedral's administrator, told US broadcaster NPR, referring to the hazardous conditions in Zipaquirá’s salt mines, where commercial mining began in 1815. “Every day that they came out of the mine alive was a reason for giving thanks,” he added.

Access to the Zipaquirá Salt Cathedral is through a long tunnel lined with eucalyptus logs. Credit: Zipaquirá Salt Park

The underground reconstruction of a Colombian symbol

The first sanctuary was eventually closed due to instability, and the cathedral itself was shut down in 1992 after years of blasting, hammering and drilling caused structural problems. A public competition was held to replace it, and several proposals were received. The winning design came from Colombian architect Roswell Garabito Pearl, who designed a new church.

A team of more than 100 miners and sculptors was assembled to construct the new cathedral, which is located 200 feet (about 60 metres) below the original. One of the greatest challenges was moving the imposing rock salt altar from the old sanctuary to the new site, according to retired mining engineer Jorge Castelblanco, who was involved in the reconstruction. The altar weighed 16 tonnes and workers had to cut it into three pieces to transport it.

The Salt Cathedral is one of Colombia's most popular tourist destinations. Credit: Travel Life Experiences

Zipaquirá's underground jewel

The Salt Cathedral opened its doors in 1995. Guides often emphasise that everything inside is hand-carved, making it a true masterpiece of engineering and craftsmanship. Since 2024, it has also housed the Monumental Underground Museum 180. Nestled in the depths of this Colombian architectural marvel, the museum showcases 22 marble and stone sculptures crafted by national and international artists.

The crosses of the Salt Cathedral are hand-carved. Credit: Zipaquirá Salt Park

Over the years, the Salt Cathedral has become one of Colombia's most popular destinations for tourists and pilgrims alike, drawing more than 600,000 visitors annually. Although it is not part of the Seven Wonders of the World, it earned a place as one of the Seven Wonders of Colombia in 2007, receiving the highest number of votes in a national competition. Furthermore, in 2024, the Andean Parliament recognised it as a landmark of cultural, natural, and historical heritage within the Andean region.

Tungsten is a journalistic laboratory that explores the essence of innovation.

Our colleagues from Sacyr Engineering and Infrastructures are building an intermodal logistics terminal in La Llagosta (Barcelona) that will transform the region into a strategic node for international freight transport. The project is an example of commitment to the circular economy and sustainability.

One of the most outstanding initiatives is the reuse of materials from the work. In total, 16,000 m³ of asphalt pavement have been collected, of which more than 90% has been reused for the crowning of embankments. In addition, 100% of the ballast (15,000 m³) has been used as a base in the road pavement layer.

"These measures, in addition to promoting circularity and having a positive environmental impact, allow cost savings, reducing the purchase of materials and avoiding their management as waste," explains Arnau Jaumandreu Sellares, Head of Quality, Environment and Energy Project.

Sacyr Circular Transformation

Sacyr Circular Transformation is our monthly series that aims to showcase the circular economy actions we carry out in our projects around the world. All of them are framed in our Zero Waste Plan.
 
Take a look at the first installments of Sacyr Circular Transformation
 
We built a brine collector that extends the lifespan of materials

We wrap up the water cycle in Langosteira

Sacyr Circular Transformation is a new monthly series aimed at showcasing the circular economy initiatives we implement in our projects around the world, all within the framework of our Zero Waste Plan.  

Our Sacyr Engineering and Infrastructure team, in partnership with Obras Taboada Ramos, is carrying out the expansion works of the Outer Port of A Coruña in Punta Langosteira (Spain). These works will provide the infrastructure with railway connectivity, ensuring its full operational capacity. The project is being executed under high environmental standards, safeguarding water quality and respecting its circularity.  

In this first edition, we delve into the treatment of water used in the excavation of the tunnels at the Port of A Coruña, its monitoring, and its subsequent discharge or reuse for industrial purposes. The goal is to minimize environmental impact and maximize water reuse.  

Purification and Reuse Process 

The excavation of tunnels and galleries requires water for machinery to drill through the rock. Once used, this water contains a high concentration of suspended solids, which we remove through decantation. Finally, we adjust the water’s pH by adding CO₂.  

To ensure the quality of the resulting water, we conduct **thorough, continuous, and transparent monitoring** of the project's water quality.  

Once treated, the water is discharged into *atural watercourses such as streams or the sea. It is also reused for industrial purposes by transferring it to the Meicende reservoir.  

At Sacyr, we are committed to promoting circular practices in our projects, in line with the principles of the Zero Waste Plan which fosters synergies across the different projects we execute.  

You can now view the 2024 Annual Report on the Sacyr Foundation's website, available in both Spanish and English. In it, you will find the most relevant data regarding its activities.

In 2024, 78 activities were carried out, 46 of which were volunteer projects involving more than 1,000 people who dedicated a total of 15,000 hours. The Volunteer Club is at the heart of the Foundation and is key to maximizing the reach of its initiatives and projects.

The Foundation has collaboration agreements with 72 organizations that benefited nearly 730,000 people in 2024, 60,000 directly and another 670,000 indirectly.

The Foundation has a solid presence in six countries: the USA, Colombia, Peru, Chile, Spain, and Kenya. Its activities have focused on seven areas of action: childhood, the environment, inclusion, emergency response, disability, healthcare, and volunteering.

The SDGs most impacted by our projects have been Goal 1, No Poverty; Goal 4, Quality Education; Goal 3, Good Health and Well-being; and Goal 10, Reduced Inequalities.