The tunnel could interfere with features that transport water to San Antonio Springs.

The Alamo Regional Mobility Authority, or RMA, entered into discussions with the Boring Co. in March to build a tunnel between the San Antonio International Airport and downtown, creating an underground pathway that can run Teslas between the two locations.

The RMA cited cost as the reason for its decision to pursue this project over a competing proposal, but it has ignored the potential impacts on the Edwards Aquifer.

The project ignores the local geology between the airport and downtown, which is well known to local geoscientists as an active part of our aquifer system with dozens of identified caves, or karst features, including San Antonio Springs (also known as the Blue Hole) and San Pedro Springs. One of the concerns is that the project will run extremely close to San Antonio Springs and potentially impact that historic and important geological feature.

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The proposed tunnel-boring machine would use a combination of fluids and cements to create the tunnel. Limestone in our area has a network of pathways that connect to groundwater. In times when aquifer levels are low, water from Olmos Creek will run into San Antonio Springs during a good rain, making it a significant recharge feature. With San Pedro Springs and other documented features in the area, it is likely that a tunnel on the proposed route, or anywhere between Harry Wurzbach Road and Blanco Road north of downtown, will intersect one or more features that also connect to the Edwards Aquifer. This project could potentially cement shut features that transport water to the spring, keeping this historic feature from flowing again. The plan also raises concerns about whether wells in the area might be impacted or how it might affect our 1.5 million downstream aquifer neighbors.

In the bidding process, a competing company with experience working locally provided a thorough geologic assessment of the area and concluded that tunneling through this geologic area was extremely risky in terms of aquifer impact. Their assessment specifically mentions that the proposed route has a significant risk of damaging San Antonio Springs with a tunnel-boring machine. The challenges encountered in the Loop 1604/Texas 151 project and the Vista Ridge project also give examples as to why tunneling in karst is a bad idea.

The Boring Co. has no experience with the local geology or our water source, which the U.S. Environmental Protection Agency has designated a sole source aquifer. A sole source aquifer supplies at least 50 percent of drinking water for its service area and is one for which there is no reasonably available alternative drinking water source should it become contaminated. If the Boring Co. had obtained a geological assessment utilizing the local knowledge base, it would see the inherent problems with the project.

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The RMA should also know better than to pursue a project that can impact the Edwards Aquifer and our historic springs. The cost to our community will be more than the difference in the price tag between projects.

Our voters have a history of supporting bonds that better our community and strengthen our natural resources. We should say “no” to this project. There are better ways to accomplish our transportation goals.

Evelynn J. Mitchell, Ph.D., is a professor of environmental science at St. Mary’s University with research experience on the Edwards Aquifer.