Building with urgency: the triple challenge of returning the bridge to the residents of Aldea del Fresno

At the beginning of the 20th century, the engineer Eugenio Ribera built one of the first reinforced concrete bridges in Spain. The bridge was built in Aldea del Fresno, a small town located between the Alberche and Perales rivers, in the southwest of the Community of Madrid. The bridge remained standing for an entire century until severe storms brought it down in September 2023.

From that moment on, a project marked by urgency, necessity and the will to give the inhabitants of Aldea del Fresno its infrastructure back began. The objective is threefold: to build a new bridge, to build another temporary crossing that will allow activity to resume in the area, and to musealize the remains of the old bridge.

The Aldea del Fresno project is not one of those projects that makes big headlines or attracts all the attention, although the press did report on the personal and material effects caused by the heavy rains. But it is a project that directly benefits society and which will have a huge impact on the daily lives of thousands of people. The project also presents important challenges insofar as it forces us to work quickly, without the support of previous planning and design.

An engineering challenge

On September 3 and 4, 2023, a cold drop (also known as a DANA, an acronym for isolated trough at high levels) led to huge rainfall in the center of the Iberian Peninsula. This caused numerous rivers to break their banks, including the Perales and Alberche. In Aldea del Fresno, major flooding caused the collapse of three of the four accesses to the town. Only one remained.

One of the bridges to collapse was that which spanned the Perales River on the M-510 highway. The situation was very difficult: much of the bridge had collapsed and large fragments had been dislodged downstream. This disrupted the activities of local residents from one day to the next and severely limited their mobility. The bridge needed to be restored urgently.

The General Directorate of Roads of the Community of Madrid chose us to act, and to do so quickly. We did not have a planned design or anything to rely on, but we did know that we had to return this infrastructure to the residents of Aldea del Fresno as soon as possible. On September 12 we were awarded the contract for the works and on September 20 we started.

The first tasks were focused on clean up. We then began to execute the works as the project was being defined. The bridge that had collapsed was 84 meters long, had a one-way six-meter roadway and a small sidewalk. The new one will be more than 100 meters longer, with two-way traffic, a bike lane, and two sidewalks.

We knew from the outset that it would take 10 to 12 months to build this new bridge, so another of our tasks was to build a temporary crossing in the shortest possible time. On November 14, little more than a month and a half after work began, we were able to open a temporary overpass to traffic based on a series of prefabricated frames.

This process is not free of challenges. From one day to the next, we organized a construction site, conducted geotechnical and other studies, defined roles and responsibilities, set up temporary work facilities, and began a myriad of activities. All actions were carried out with safety and efficiency in mind, but one premise was always present: speed. This was a major effort for the team and would not have been possible without the effort and collaboration of all, both the personnel assigned directly to the work and the support services provided by this company.

A new stage of a historic bridge

The bridge that allowed passage over the Perales River until last September was typical of the constructions of its time. It also had its own singularities and historical value, which is why it was protected as a heritage site. The most special feature of its structure was its piles, which were joined together by horizontal crossbeams forming a reticular lattice. Ribera himself considered this bridge to be exemplary, since it is the structure he chooses to represent the typology of straight span bridges in Spain in his work "Puentes de fábrica y hormigón armado" [Masonry and reinforced concrete bridges].

After its collapse, we contacted heritage authorities of the Community of Madrid to define how to musealize those parts that could be preserved. The force of the water left only one of the five initial spans standing in the first section of the bridge, which we will consolidate so that it remains in perfect condition. Another part of the bridge, corresponding to the abutment, was practically in ruins. And that's how it will stay.

The preservation of these fragments, whether consolidated or in ruins, is very important to leave a record of the past of our infrastructure. Our new bridge will pass a meter and a half above the old one, thus leaving room to remember and keep history alive.

Value for the community

A few days after the bridge over the Perales River collapsed, we began to experience and understand the problems generated by the lack of infrastructure. As it passes through Aldea del Fresno, the M-510 road normally hosts more than 2,000 vehicles per day. It serves to connect different localities in the area and to access other main roads.

During the six weeks it took to erect the temporary crossing, the absence of a bridge limited the movements of everyone, young and old alike. Students had to make a significant detour to get to school, which made it a much longer trip and meant that some students were unable to start classes in person. To get to the municipal sports center, they were forced to cross the river, which, before the work began, was full of tons of debris, mud and vegetation that had been washed away by the flood.

This project has helped us to understand the value of infrastructure for people. When we finished the temporary bridge, the neighbors were very grateful. We found drawings by children with messages such as "Thank you for letting us pass." We enjoyed the experience of working in a small town where interpersonal relationships are much closer. We got to know the mayor, the police, the residents.

The improvements can also be seen in figures. We forecast that, once the new bridge is built, with more capacity and more lanes, the number of people using the bridgewill increase, allowing the passage to vehicles of greater tonnage. These are small improvements that will leave a significant footprint in Aldea del Fresno.

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