An Overview of Mining-Related Environmental and Human Health Issues, Marinduque Island, Philippines: Observations from a Joint U.S. Geological Survey – Armed Forces Institute of Pathology Reconnaissance Field Evaluation, May 12-19, 2000 U. S. Geological Survey Open-File Report 00-397 Geoffrey S. Plumlee1 Robert A. Morton2 Terence P. Boyle3 Jack H. Medlin4 José A. Centeno5 1U.S. Geological Survey, MS935 Federal Center, Denver, CO 80225; [email protected] 2U.S. Geological Survey, 600 4th Street South, St. Petersburg, FL 33701; [email protected] 3U.S. Geological Survey, Aylesworth Hall NW, Colorado State University, Ft Collins, CO 80523; [email protected] 4U.S. Geological Survey, National Center, Reston, VA 22091; [email protected] 5U.S. Armed Forces Institute of Pathology, Washington, DC 20306-6000;[email protected] This report is available online at: http://geology.cr.usgs.gov/pub/open-file-reports/ofr-00-0397/ Boac River,, tailings from 1996 spill Tapian pit lake An Overview of Mining-Related Environmental and Human Health Issues, Marinduque Island, Philippines: Observations from a Joint U.S. Geological Survey – Armed Forces Institute of Pathology Reconnaissance Field Evaluation, May 12-19, 2000 By Geoffrey S. Plumlee, Robert A. Morton, Terence P. Boyle, Jack H. Medlin, and José A. Centeno Executive Summary received or are still receiving acid rock This report summarizes results of a visit by the drainage, high sediment loads, and tailings report authors to Marinduque Island, Philippines, transported from the mine site; in May 2000. The purpose of the visit was to con- " The beaches and ocean at and near the mouth duct a preliminary examination of environmental of the Mogpog and Boac River systems; problems created by a 1996 tailings spill from the " Calancan Bay, into which very large volumes Marcopper open-pit copper mine. The mine was of tailings were disposed for 16 years; and operated from 1969-1996 by Marcopper Mining " The area within and adjacent to the mine site, Corporation, under 39.9% ownership, and design which is affected by multiple sources of acid- and management control, of Placer Dome, Inc. rock drainage into ground and surface waters, Our trip expenses to and from the Philippines and by sediments eroded from mine waste were funded by the USGS. In-country expenses piles. were paid by the offices of Congressman Reyes Less well-known but potentially significant and the Governor of Marinduque, Carmencita O. environmental problems may also exist as a result Reyes. of open pit mining at the CMI mine near This report includes observations we made Mogpog. Potential problems at CMI include: based on our relatively short visit to the island, " Effects of acid-rock drainage from mine and observations based upon a preliminary review dumps, tailings impoundments, and the mine’s of the literature available on the island’s mining- open pit on local surface and ground waters; environmental issues. In addition, we have and included preliminary interpretations and analyti- " Effects of mine wastes and tailings on the cal results of some water, sediment, and mine marine ecosystem. waste samples collected during our trip. We also Our team has identified a number of concerns highlight the environmental and human health associated with each of these areas, and has sum- issues we feel are in need of further study and marized for many of the areas actions that can be consideration for mitigation or remediation. This taken to better understand and (or) help mitigate report is preliminary and is not intended to be a the problems. comprehensive or final review of the island’s min- ing-environmental issues; many areas of further Boac River tailings study are clearly needed. The main priority of our visit was to get an Mining-related environmental problems have overview of the 1996 Boac River tailings spill, greatly affected several areas on Marinduque. and the proposed options to remediate the spill. Most of the observed problems stem from large- From information gathered on our trip, a limited scale open pit copper mining at Marcopper, and review we have made of reports on the tailings, primarily affect: and the results of simple leach experiments we " The Mogpog and Boac River systems, which performed to examine metal mobility from the 1 tailings, several conclusions are clear. The tailings unbiased scientific review of all information and deposits in the Boac River, as concluded in earlier reports gathered to date, to determine if enough studies by the mining company, will be a long- information is available to adequately judge the term source of acid and metals into the environ- scientific strengths and weaknesses of each of the ment, and are therefore in need of remediation. options. If not, then new data or information must Due to oxidation of sulfides in the tailings, the be gathered. Similarly, for options not covered in generation of acid waters during rainstorms, and the published reports, scientific and engineering the evaporation of these acid waters during dry data must be gathered to assess the strengths and periods, substantial deposits of soluble salts have weaknesses of each option. The monetary and built up within the tailings. These salts store acid time costs of gathering new data and information and metals in a readily soluble solid form until the to assess a particular option should be carefully next rainstorm, when they are likely to dissolve weighed. If new data acquisition for a particular and produce an ecologically damaging flush of option is too costly, then that option may not be acid and metals into the Boac River. The cycle of viable. salt formation and dissolution can be repeated We have provided in the report examples of each dry and wet period. the types of scientific questions needing to be Remedial options: A number of remedial addressed for any proposed remedial option in options are available for the Boac River tailings, order to assess its strengths and weaknesses. including many options identified by the mining These include such issues as the long-term viabil- company and other options proposed by residents, ity of the proposed option, potential ways that the companies, or groups. Many reports have been option could fail, and potential environmental generated by the mining company that evaluate impacts should the option fail to work properly. their proposed options. Using a risk analysis An example of one type of scientific informa- process, the company has determined submarine tion that can be used to help assess the remedial tailings disposal to be its preferred remedial options is a simple leach experiment we per- option. However, based on the reports we have formed to understand reactions of Boac River reviewed, it is not clear whether key scientific tailings with sea water. This leach test raises sig- data and interpretations have been made that in nificant concerns that submarine disposal of the our minds are crucial to adequately understand salt-rich tailings from the Boac River banks and the strengths and weaknesses of each of the reme- tailings flats into the ocean may have substantial dial options. adverse environmental impacts. Due to the sub- Assessing the remedial options: We have out- stantial amounts of soluble salts in the tailings lined a process by which remedial options avail- and the strong ability of chloride in sea water to able for the Boac River tailings can be assessed. complex metals from the tailings, there is consid- The purpose of an independent assessment should erable potential that a highly acidic, metal- be to review each option and present information enriched, and environmentally detrimental plume on the scientific and engineering strengths and would develop in the ocean around the tailings weaknesses of each option. This then would allow discharge point during tailings disposal; it is the people of Marinduque to make the best, most unclear whether acid and metals would continue scientifically informed choice possible regarding to leach from the tailings once disposal is fin- remediation. Ultimately, no single option may ished. Unless proven otherwise by further studies, prove ideal, but rather a combination of options the potential development and environmental may be best. effects of such a plume should be considered as a The first step is a thorough, independent, and major shortcoming of this remedial option. 2 Assessing, monitoring, and remediating other Mogpog and Boac Rivers and their inhabitants mining-environmental problems on should be assessed by evaluating the entire sys- Marinduque tem that includes the mine site, Mogpog and Boac We are not aware of plans for mitigating or river watersheds, and marine environment affect- remediating mining-environmental problems on ed by the two rivers, such as: Marinduque other than the 1996 tailings spill. " Contributions of acid, metals, and sediments However, the potential magnitude and impacts of from Marcopper; these other problems are so great that we strongly " Contributions of acid, metals, and sediments recommend the implementation of a general min- from other mine sites and disturbed areas; ing-environmental and health assessment and " Contributions of acid, metals, and sediments monitoring program on the island. The primary from natural sources; goals of such a monitoring and assessment pro- " The ground- and surface-water hydrology of gram should be to (1) understand and define the the mine site, and Boac and Mogpog river magnitude of the different environmental prob- watersheds; lems, (2) prioritize the problems for remediation, " Contributions of ground and surface waters and (3) look for creative, cost-effective ways to from other tributaries in the Mogpog and Boac help mitigate or remediate the problems. Rivers; In fact, the review of the Boac River tailings " Processes that affect contaminant transport in remedial options should be carried out as only ground, surface, and ocean waters; one part of such an overall assessment.