Costos de cierre en depósitos de desmontes y presas de relaves generadores de acidez
Abstract
La extracción de mineral y el proceso de beneficio generan residuos mineros como Desmontes y Relaves que por lo general se almacenan en depósitos ubicados en superficie, esta ocupación de terrenos y el requerimiento de una adecuada gestión ambiental hacen que en el diseño de estos depósitos se consideren requerimientos técnicos, económicos, legales, ambientales y sociales. Durante la vida operativa de los depósitos de residuos mineros se implementan controles para reducir los impactos sobre el medio ambiente y en las comunidades del entorno, a través de los programas de monitoreos continuos considerados en las certificaciones ambientales de obligado cumplimiento, como son los estudios de impacto ambiental, pero, una vez culminada la operación minera se pone en marcha la etapa de cierre en donde se procede a rehabilitar el lugar de emplazamiento de estos depósitos que almacenan residuos mineros como desmontes de mina y relaves. Para elegir la alternativa de cierre de estos depósitos se tiene en cuenta una serie de factores como el lugar de emplazamiento, las propiedades físicas y químicas de los residuos mineros, el método de construcción del depósito y principalmente el comportamiento geoquímico de los residuos a largo plazo, para ello, es importante estimar la probabilidad de alteración de los residuos mineros en contacto con agua y oxígeno, así como, la capacidad de generación de acidez y lixiviación de metales, entre otros. El esquema de cierre de los depósitos debe asegurar la estabilidad física, química, hidrológica y biológica en el postcierre. Uno de los mayores problemas para lograr la estabilidad de los residuos mineros como desmontes y relaves con potencial de generación de acidez es el contacto con oxígeno y agua; por tanto, para alcanzar la estabilidad química, se recurre al empleo de barreras y coberturas impermeables o semipermeables. Cada alternativa comprende una serie de actividades de cierre, que inducen a determinados costos de ejecución, lo que genera diferentes costos directos e indirectos en el presupuesto de cierre. En este trabajo se presenta las variaciones de los costos de cierre para diferentes depósitos de residuos mineros, identificando las variables con mayor sensibilidad e influencia sobre los presupuestos de cierre de minas, como el fin de optimizar su gestión desde su concepción hasta la rehabilitación, empleando las mejores técnicas disponibles en sus diseños, construcción, operación y cierre.
Mineral extraction and the beneficiation process genérate mining waste such as waste rock and tailings that are generally stored in surface deposits. This occupation of land and the requirement for proper environmental management mean that technical, economic, legal, environmental and social requirements are considered in the design of these deposits. During the operating life of the mining waste deposits, controls are implemented to reduce the impact on the environment and surrounding communities through continuous monitoring programs included in the mandatory environmental certifications, such as environmental impact studies, but once the mining operation is completed, the closure stage begins, when the site of these deposits, which store mining waste such as mine waste and tailings, is rehabilitated. In order to choose the closure alternative for these deposits, a series of factors are taken into account, such as the location of the site, the physical and chemical properties of the mining waste, the construction method of the deposit and mainly the geochemical behavior of the waste in the long term, for which it is important to estímate the probability of alteration of the mining waste in contact with water and oxygen, as well as the capacity to genérate acidity and leaching of metáis, among others. The closure scheme of the deposits must ensure physical, chemical, hydrological and biological stability post-closure. One of the biggest problems in achieving stability of mining waste such as waste rock and tailings with the potential to genérate acidity is contact with oxygen and water; therefore, to achieve chemical stability, the use of impermeable or semi-permeable barriers and coverings is used. Each alternative includes a series of closure activities, which induce certain execution costs, generating different direct and indirect costs in the closure budget. This paper presents the variations of closure costs for different mine waste deposits, identifying the variables with greater sensitivity and influence on mine closure budgets, in order to optimize their management from conception to rehabilitation, using the best available techniques in their design, construction, operation and closure.
Mineral extraction and the beneficiation process genérate mining waste such as waste rock and tailings that are generally stored in surface deposits. This occupation of land and the requirement for proper environmental management mean that technical, economic, legal, environmental and social requirements are considered in the design of these deposits. During the operating life of the mining waste deposits, controls are implemented to reduce the impact on the environment and surrounding communities through continuous monitoring programs included in the mandatory environmental certifications, such as environmental impact studies, but once the mining operation is completed, the closure stage begins, when the site of these deposits, which store mining waste such as mine waste and tailings, is rehabilitated. In order to choose the closure alternative for these deposits, a series of factors are taken into account, such as the location of the site, the physical and chemical properties of the mining waste, the construction method of the deposit and mainly the geochemical behavior of the waste in the long term, for which it is important to estímate the probability of alteration of the mining waste in contact with water and oxygen, as well as the capacity to genérate acidity and leaching of metáis, among others. The closure scheme of the deposits must ensure physical, chemical, hydrological and biological stability post-closure. One of the biggest problems in achieving stability of mining waste such as waste rock and tailings with the potential to genérate acidity is contact with oxygen and water; therefore, to achieve chemical stability, the use of impermeable or semi-permeable barriers and coverings is used. Each alternative includes a series of closure activities, which induce certain execution costs, generating different direct and indirect costs in the closure budget. This paper presents the variations of closure costs for different mine waste deposits, identifying the variables with greater sensitivity and influence on mine closure budgets, in order to optimize their management from conception to rehabilitation, using the best available techniques in their design, construction, operation and closure.
Description
Vol. 7, No. 2