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The works of the underground tunnel against floods in Xanxerê (SC) began this week with controlled explosives and R$ 20 million in investment, a structure of 943 meters drilled in the rock mass that will capture rainwater in the center and conduct it to the Xanxerê River, with a deadline of 14 months for the excavation.
Xanxerê, in the West of Santa Catarina, began this week to excavate the underground tunnel that promises to end the floods that have plagued the central area of the city for years. The project, described by the city hall as the most ambitious infrastructure undertaking in the municipality’s history, will require over R$ 20 million and will have 943 meters drilled in the rock mass with explosives and scheduled detonations. The underground tunnel will connect Matinho to the city center, where a vertical well will be built to capture rainwater that currently floods streets and homes, and an open channel of approximately 125 meters will conduct this water to the bed of the Xanxerê River at the exit point.
The initial work is focused on preparing the ground at the mouth of the underground tunnel, located in the Matinho neighborhood, approximately 200 meters below the level of BR-282, near the decommissioned Westerich quarry. The team has started clearing the area, removing the organic layer of soil, and the initial drilling of the rock at the surface, a phase that precedes the actual drilling of the mass. According to the Secretary of Urban Planning and Environment, Leandro Marzari Silva, the first 50 meters will concentrate the most intense rhythm of detonations, carried out on the surface before advancing into the rock. Access to the site remains restricted for safety reasons during this stage.
Why Xanxerê needs an underground tunnel to solve the floods
The central area of Xanxerê suffers from recurring flooding that the conventional drainage infrastructure has never been able to solve. The city’s topography, with a steep gradient between the higher neighborhoods and the center, causes large volumes of water to flow down towards the commercial and residential streets with each heavy rain, overwhelming galleries and drains that were not designed for the urban growth of recent decades. The result is frequent material losses, traffic interruptions, and risks to the safety of residents who live with water invading homes and businesses.
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The solution found by the municipal administration was to create an alternative route for this water, and the underground tunnel fulfills exactly this function. Instead of trying to expand the surface drainage, which would require invasive works in the already consolidated center, the project drills nearly 1 km of rock beneath the city, a R$ 20 million project that directs the runoff directly to the Xanxerê River, diverting the flow before it reaches the most vulnerable areas. The strategy is similar to that adopted by capitals that use large retention basins and deep galleries, but adapted to the geological reality of Xanxerê, where the presence of rock mass makes excavation with scheduled explosives feasible.
How the construction of the underground tunnel with explosives in Xanxerê will be
The excavation of the underground tunnel requires engineering techniques that combine scheduled detonations and mechanical excavation. The first 50 meters will be opened to the open air with controlled explosions that fragment the rock into removable blocks, a phase in which the work pace is more intense and the noise from the detonations will be noticeable to nearby residents. After reaching the necessary depth to enter the mass, the explosions will occur inside the rock, with significantly lower sound and vibrational impact on the surface.
The rocky material extracted during the construction of the underground tunnel will not be discarded. The city hall of Xanxerê reported that all the stones removed will undergo a crushing process and will be reused in the maintenance of rural roads and as base material for asphalt on urban perimeter roads. This reuse reduces the environmental cost of the work and generates savings for the municipal administration, which takes advantage of a byproduct of excavation to address another infrastructure demand without spending additional resources on material acquisition.
How much does the underground tunnel cost and where does the money come from
The amount of R$ 20 million will be divided between resources from the government of the state of Santa Catarina and the city hall of Xanxerê. For a municipality in the interior of Santa Catarina, this amount represents a significant budget commitment, but the administration believes that the cost is justified given the accumulated damages over years of floods that affect commerce, residential property, and public services in the central region. Each flooding event generates material losses and cleaning costs that, when added together, exceed the value of the explosives and engineering needed to drill the 943 meters of rock.
The city hall’s forecast is to complete the excavation phase of the underground tunnel in approximately 14 months, a schedule that depends on the pace of the explosives and the geological conditions encountered as drilling progresses through the mass. After excavation, it will still be necessary to execute the vertical capture well in the city center and the open channel of 125 meters that will connect the outlet to the Xanxerê River, complementary stages whose deadline has not been detailed by the administration. The complete conclusion of the macro-drainage system is expected to take longer than the 14 months planned just for drilling.
What changes for Xanxerê when the underground tunnel is ready
If it works as designed, the underground tunnel will eliminate the main factor that makes the central area of Xanxerê vulnerable to flooding. The water that currently flows down from the higher neighborhoods and accumulates in the streets of the center will be captured by the vertical well and directed through almost 1 km of rock to the Xanxerê River, an underground route that keeps it away from urban roads before it causes damage. The impact goes beyond flood prevention: it reduces public health risks from stagnant water contamination, preserves the asphalt that is currently damaged by the force of the current, and increases property values in a region that has lost attractiveness precisely due to the recurrence of floods.
The project is described by the administration as long-awaited by the community, and its execution represents a concrete change in the quality of life for residents in the central area. The R$ 20 million underground tunnel in Xanxerê proves that large-scale engineering solutions are not exclusive to capitals: interior cities with chronic flooding problems can resort to heavy infrastructure when conventional alternatives are exhausted. The challenge now is to meet the schedule and deliver the system functioning before the next intense rainy season arrives in western Santa Catarina.
And you, do you live in Xanxerê or in a city with a similar flooding problem? Do you think the underground tunnel will truly solve the issue or is it just another project that will take time? Leave your opinion in the comments.
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