Remediation Study to use Dolomite to Neutralize Sulfuric Acid in the Abandoned Copper Mine Pits in Marinduque

Abstract

Marcopper started producing copper, gold and silver from the Tapian pit from 1969 to 1991. The tailings were sent to the San Antonio impoundment pit until 1975. It shifted its tailing disposal to the Calancan Bay in 1976. One hundred twenty (120) million tons of copper mine tailings has been discharged in the Calancan Bay (USGS, 2000). It is estimated that the tailing discharge of Marcopper was 200 to 300 million tons between 1975 to 1990 (USGS, 2000). In 1991 after finding that the San Antonio impoundment pit contains copper and other minerals the mining activity shifted to the San Antonio impoundment pit and with the approval of the Philippine government agency , the “Kagawaran ng Kapaligiran at Likas Yaman” (KKLY), discharged mine tailings from Calanacan Bay to the abandoned Tapian pit. The dewatering tunnel, that is used to drain water at the Tapian pit located 195 meter above the Makalunpit river, was plugged to prevent the mine tailings from contaminating Boac and Mogpog rivers. This means Boac river and Mogpog river thru Makalumpit river has been exposed to acid mine drainage (AMD) since 1969. On March 24, 1996 Marcopper cease mining operation when “the plug in the 195-m level drainage adit failed catastrophically. The plug failure resulted in the release of an estimated 1.5-3 million cubic meters (UNEP, 1996) of sulfuric tailings (AMD) slurry from the Tapian Pit storage area into the Makalunpit river, Mogpog, Boac river, and eventually the ocean west of the island” (USGS, 2000). After the disaster, Placer Dome, dispossed its financial ownership in Marcopper and created the Placer Dome Technical Services (PDTS) to determine options to remediate the major environment mining disaster. One of the immediate measures was to create a one-kilometer berm on both sides of the Boac riverbanks to protect the farmlands from over flooding. PDTS also dredge the Boac river 20 meters deep. PDST re-plugged the 195-meter adit to prevent the discharge of AMD into the Makalumpit, Mogpog and Boac rivers. One proposal of PDTS was to provide a submarine pipeline towards the sea where the mine AMD tailings will be dropped into the depths of the ocean in Tablas Straight. This proposal was denied by the “Kagawaran ng Kapaligiran at Likas Yaman” (KKLY).

A study made by the “Joint U.S. Geological Survey – Armed Forces Institute of Pathology Reconnaissance Field Evaluation, on May 12-19, 2000 by Geoffrey S. Plumlee, Robert A. Morton, Terence P. Boyle, Jack H. Medlin, and Jose A. Centeno” on the “An Overview of Mining-Related Environmental and Human Health Issues, Marinduque Island, Philippines” in collaboration with the Office of the Governor of Marinduque concluded that “the potential magnitude and impacts of all these problems are so great that we strongly recommend the implementation of a general mining-environmental assessment and monitoring program on the island. The primary goals of such a monitoring and assessment program should be to (1) understand and define the magnitude of the different miningenvironmental problems, (2) prioritize the problems for remediation, and (3) look for creative, cost-effective ways to help mitigate or remediate the problems”. This study has its purpose inspired by item (3) recommendation.