Sometime before this week, someone placed an improvised explosive device underwater at the Converse Reservoir dam in Mobile, Alabama. It was found Tuesday — not by investigators acting on a tip, but by divers conducting what the Mobile Area Water and Sewer System described as routine repair and maintenance work on the dam. The reservoir, at Big Creek Lake, supplies drinking water to much of the Mobile area, and the dam that holds it is federally designated critical infrastructure.

The device was a grenade-type IED. Once the divers located it, MAWSS alerted the Mobile County Sheriff's Office, which coordinated a multi-agency response for analysis, retrieval, and safe demolition. That response drew in the FBI Bomb Squad, the Mobile Police Department Explosive Ordnance Detail, the ALEA Bomb Squad, and the Daphne Search and Rescue Team. The Gulf Coast Regional Maritime Response and Render-Safe Team carried out the retrieval and detonated the device. The U.S. Department of Homeland Security was made aware of the incident.

MAWSS Director Bud McCrory framed the discovery in stark terms. "Our top priority is keeping your drinking water safe," he said. "This is an unprecedented threat, and we are fortunate that this device was discovered before it could cause serious damage to our water supply or harm to individuals. We are grateful for the professionalism and competency of our law enforcement partners – as well as the quick thinking of our contractors and divers – in identifying this device and safely destroying it."