The use of satellite-based remote sensing methods to assess the changes in the environmental impacts from the Marcopper disaster on Marinduque Island, Philippines

摘要

The Marcopper Mining Disaster occurred between 1975 and 1996 on the Philippine island of Marinduque, a province of the Philippines. It remains one of the largest mining disasters in history and is almost completely un-rehabilitated. The Marcopper Mining Corporation mined the Mt. Tapian ore body followed afterwards by the San Antonio copper ore body, using open pit methods. Three separate environmental incidents occurred during this time which finally culminated in between 2 to 3 million tonnes of tailings which flowed from the Tapian in-pit tailings facility along a drainage tunnel into the 26 km long Boac River. Flooding isolated and buried some villages under 2 m offlood water and tailings. Environmental impacts were considerable and the government declared the Boac River dead. Since 2002, despite two major studies which were completed in 2004 and 2005, no remediation efforts have been undertaken on any of the waste landforms or rivers to-date.In order to understand the ongoing environmental changes taking place on the mine waste landforms, the Australian Centre of Geomechanics partnered with MacDonaid, Dettwiler and Associates to undertake a preliminary review of the Marcopper waste landforms using products derived from historical radar and optical images collected over the island from the 1996 to 2014. This paper summarises the results of this study and makes recommendations for further remote sensing studies and ground-truthing activities.Remote sensing challenges using historical data were significant and included persistent cloud cover or haze in regions, heavy vegetation in some areas, and localised steep terrain. Historical images were used to map the changes taking place on the waste landforms using a variety of remote sensing approaches including automated multi-date change detection algorithms, Normalised Difference Vegetation Index, terrain analysis and land cover mapping.This study found that the Calancan Bay tailings outfall has retreated over 550 m since 1996 and that barren and steep-sloped regions are present near the mine pits and tailings dams. In addition, the size of both pit lakes has continued to increase. Nevertheless, the findings showed that within the vicinity of the open pits and mine waste landforms there has been gradual reestablishment of vegetation during the 18-year study period.