Guest: John Metzger (LinkedIn), Founder of Asset Assurance Monitoring (Website). "I don't know how, but I recognized it was one of my children. My friend rescued Nicolas, and I thought: Oh my God, at least I managed to catch one." These were the words of a father fleeing the 2015 Bento Rodrigues (Mariana) dam disaster in Brazil (O Globo, 08/11/2015). Five days later, his daughter Emanuele was found dead. The collapse killed 19 people and sent a torrent of toxic mine waste 670km down the Doce River to the Atlantic Ocean. It was Brazil’s worst environmental disaster. Four years later, just 70km west, it happened again. The 2019 Brumadinho dam collapse killed 272 people—including an entire family of five and an unborn child—becoming Brazil’s worst industrial disaster. Both mines were owned by corporate giant Vale. When raw ore is extracted, the toxic, liquid byproduct is stored behind massive earthen structures called tailings dams. Globally, there are an estimated 29,000 to 35,000 active, inactive, or abandoned tailings storage facilities (TSFs) holding 223 billion tonnes of waste (World Mine Tailings Failures). Active sites account for 85% of all failures. The risk is ongoing: as of late 2025, Brazil alone has 916 dams, with 74 at high risk of collapse and 91 on alert, concentrated heavily in the mining hub of Minas Gerais. When these structures are poorly designed or neglected, they fail. When they fail, the wall of mud obliterates everything in its path. Our guest today, John Metzger, is an expert on the advanced monitoring systems designed to prevent these catastrophes. Having led an incredible, multi-country career, John joins us to explain how real-time data, geotechnical instrumentation, and rigorous telemetry save lives. There were fatal systemic flaws of recent disasters—including why Brumadinho’s emergency warning alarms failed to sound, echoing previous conversations on the show with Floodmapp’s Juliette Murphy on the desperate need for strict flood-alarm regulations (YouTube Link). Also corporate failures: reports that Vale knew of automated sensor malfunctions two days before the Brumadinho collapse (Mining.com Report) and allegations that safety inspectors felt corporate pressure to sign off on unstable structures. Despite these failures, there are rays of hope. First, the recent establishment of the UN-backed Global Tailings Management Institute (GTMI), a new international watchdog tasked with ending corporate negligence in tailings management. Second, I want to honor the legacy of Lindsay Newland Bowker, the actuary behind the vital World Mine Tailings Failures database, who passed away in May 2026. To ensure her work is not lost to time, I have an upcoming conversation with Ankur Shah of PlanetSapling to discuss the future of open-source risk mapping.
