SOCIAL, ENVIRONMENTAL AND HEALTH IMPACTS OF A LARGE-SCALE TAILINGS SPILL ON MARINDUQUE ISLAND, THE PHILIPPINES

In March, 1996, catastrophic failure of a tailings impoundment at the Marcopper mine released ~ 1.5-3.0 Mm³ of Cu-rich sulfidic tailings into the island's largest watershed. The tailings deposited along the Boac River and western coastal waters had extensive environmental impacts. Lengthy stakeholder debate about the spill led the island's governor to commission our interdisciplinary team to conduct an independent assessment of mining-related engineering, environmental, and health issues. We reviewed the available data and advised stakeholders on possible remediation strategies. As of 2003, the Boac River tailings were being commingled with and buried by unmineralized sediments, with some recovery of downstream water quality and aquatic life; however, due to acid-mine drainage (AMD) from Marcopper, river water in Boac tributaries near the mine remains unsuitable for aquatic life or domestic use. In contrast, the Mogpog River, a much smaller watershed that experienced a mine spoils containment dam failure in 1993, is severely affected by AMD and mine wastes from Marcopper along its full course to the ocean. As of 2003, ground water along both rivers was unaffected by mine contamination, but is in need of continued monitoring. Although alleged cases of human lead and arsenic poisoning had previously been attributed to the mining, we could not, based on the available data, document such links; we recommended further monitoring and assessment studies to better understand potential health impacts. We concluded that impending failures of unstable mine structures and ongoing release of AMD and acid-generating mine wastes from Marcopper pose the greatest threats to public safety and the environment, and therefore are of highest priority for remediation. This project underscores the need for interdisciplinary mining-related environmental health assessments, and highlights many scientific, logistical, political, and cultural challenges such assessments must overcome.