Joint UNEP/DHA Environment Unit
The Marinduque Island Mine Disaster, Philippines
The Marcopper Mining Corporation (hereafter Marcopper) started its mining operations on Marinduque Island, Philippines, in 1969 at what was known as the Mt. Tapian ore deposit. Copper concentrate, also containing gold and silver, was produced from the deposit. When the Mt. Tapian reserve was depleted in 1990, Marcopper continued its operations utilizing the San Antonio copper orebody which lies some three kilometers north of the Mt. Tapian mining complex. The milling or processing method follows the conventional crushing, grinding, flotation mill, filtering and thickening to produce copper concentrate and tailing residues. The process does not utilize any cyanide or mercury.
Mine tailings from the Mt. Tapian ore deposit were discharged into Calancan Bay. It is estimated that a total of no less than 84 million metric tons of mine tailings were discharged into this shallow bay between 1975 and 1988. As a consequence of what is understood to have been a non-negotiable stance by local residents against the continued dumping of mine tailings into Calancan Bay, it was agreed that the old Mt. Tapian open-cut mine site (Tapian Pit) would be used to receive mine tailings from the San Antonio operations on a temporary basis. This disposal method was not discussed in the Environmental Impact Assessment. In spite of the unconventional use of the Tapian Pit as a containment system, no environmental risk assessment and management were carried out.
Since 1993 it is estimated that about 20 million cubic meters of tailings have been impounded in the Tapian Pit which is 300 meters deep. The estimated capacity of the pit is approximately 69 million cubic meters.
On 24 March 1996, mine tailings began escaping from the Tapian Pit through the plugged drainage tunnel into the Makulapnit and Boac Rivers. The cause of the failure is unknown. While reports vary, between two and three million cubic meters of mine tailings are estimated to have been released into the Makulapnit and Boac River system over the following 4-5 days at a discharge rate of between five and ten cubic meters per second. Subsequently, the flow of mine tailings from the drainage tunnel was reduced without intervention and as a result of undetermined cause. In late April 1996, the flow rate was estimated to be not less than 0.2 cubic meters per second and possibly higher.
The Makulapnit and Boac Rivers below the failed drainage tunnel were reported to have been severely affected, with the channels and valley floor of the two rivers being buried under mine tailings. The tailings had reached as far as the coastal area adjacent to the mouth of the Boac River, 26 kilometers from the outfall, by the 28 March 1996. The deposition of between 1 and 2 meters of tailings were reported in the upper sections of the Makulapnit and Boac Rivers where the river valley is somewhat confined.However, extensive areas of deposition were observed to exist along the entire length of the Makulapnit and Boac Rivers to the coast. In April 1996, tailings were still flowing unimpeded to the ocean and being deposited in the near shore marine environment.
Approximately 700 families from 5 barangays were reported to be seriously affected by the discharge. Initial affects of the spill were reported as the loss of most river crossings, loss of road connections, and the inundation of between 6 and 10 hectares of cropland which was used for banana and other agricultural purposes. While the mine tailings were reported to be non-toxic by Marcopper, the high visibility of the tailings, much speculation regarding their toxicity, and conflicting accounts with regard to the nature and adverse effects of the tailings on the environment and human health resulted in suspicion, conflict and concern throughout Marinduque Island.
Following the spill of tailings into the Makulapnit and Boac Rivers from the Marcopper mine, the Department of Environment and Natural Resources of the Government of the Philippines requested, through the UNDP Resident Representative in Manila, that the United Nations provide an independent assessment mission to the site of the mine tailings spill on Marinduque Island. The Mission was subsequently organized by the Joint United Nations Environment Programme/Department of Humanitarian Affairs (UNEP/DHA) Environment Unit. The Mission was organized in close cooperation with UNDP and the Government of the Philippines.
The U.N. Mission team was composed of six specialists in various fields relevant to the impact assessment and rehabilitation of areas affected by mine tailings. The members were as follows:
The objectives of the U.N. Mission included the following:
(a) the environmental significance of the mine tailings spill;
(b) the spill's effects on human health;
(c) any other damage caused by the spill;
(d) recommendations on appropriate short and long-term measures to be taken with regard to the consequences of the spill.
The U.N. Mission team arrived in the Philippines on 26-27 April 1996. During five days, the team remained in the area to carry out the assessment. The team inspected the affected areas, interviewed local residents and government officials and collected samples for chemical and physical analysis.It met subsequently with the various involved actors to discuss the results of their findings. The U.N. Mission final report was sent to the Government of Philippines and the involved UN organisations. In line with the objectives of the mission, the report which is 73 pages long, contains an extensive ecotoxicological assessment, an evaluation of the impacts on human health and well-being, general discussion on the causes, as well as recommendations to avoid future disasters.
Based on the assessment, the U.N. Mission team concluded, inter alia, that: