Mexico City plans to draw drinking water from a mile-deep aquifer, according to a report in the Los Angeles Times. The Mexican effort challenges a key tenet of U.S. clean water policy: that water far underground can be intentionally polluted because it will never be used.

U.S. environmental regulators have long assumed that reservoirs located thousands of feet underground will be too expensive to tap. So even as population increases, temperatures rise, and traditional water supplies dry up, American scientists and policy-makers often exempt these deep aquifers from clean water protections and allow energy and mining companies to inject pollutants directly into them.

As ProPublica has reported in an ongoing investigation about America’s management of its underground water, the U.S. Environmental Protection Agency has issued more than 1,500 permits for companies to pollute such aquifers in some of the driest regions. Frequently, the reason was that the water lies too deep to be worth protecting.

But Mexico City’s plans to tap its newly discovered aquifer suggest that America is poisoning wells it might need in the future.

Indeed, by the standard often applied in the U.S., American regulators could have allowed companies to pump pollutants into the aquifer beneath Mexico City.

For example, in eastern […]