Executive Summary

Minesites can consist of many components including the mine itself (pits and underground workings), tailings impoundments, waste-rock dumps, ore stockpiles, plant sites, building foundations, and roads. Any component can affect the chemistry of water flowing over, or through, it by various geochemical processes. These processes include the leaching of metals and nonmetals at neutral, acidic, and alkaline pH and the oxidation of sulfide minerals.

Case studies of water chemistry and geochemical processes in tailings impoundments are generally available (e.g., Jambor and Blowes, 1994). Similar studies for mine-rock piles including roads and foundations are less common, but still available (e.g., Morin et al., 1991). However, geochemical investigations of pits and underground workings ("mines") are rarer.

In order to better understand and predict water chemistry in and around mines in Canada, the Canadian Mine Environment Neutral Drainage (MEND) Program and the British Columbia Acid Mine Drainage Task Force sponsored a project now known as MINEWALL 1.0 (Morin, 1990). That study involved (1) a literature review, (2) a one-time geochemical assessment of the Main Zone Pit at Equity Silver Mines (British Columbia), (3) the development of a rudimentary site-specific computer program for predicting pit-water chemistry (MINEWALL 1.0), and (4) recommendations for conducting pit-water assessments.

MEND and the Task Force decided to expand and refine MINEWALL, leading to MINEWALL Version 2.0. This is one of four reports describing MINEWALL 2.0, which is both a simple technique for predicting water chemistry in mines and a computer program to assist with predictions for complex scenarios. MINEWALL 2.0 is based on literature reviews of relevant theory, testwork, and past studies, some over 30 years old (summarized in Morth et al., 1972). As a result, the technique and program were designed to be flexible and widely adaptable to many site-specific conditions.

The following sections of this report present data and observations gathered from published and unpublished literature. As a result, many relevant physical, geochemical, and biological principles are discussed. All of this information can be combined into generalized conceptual models that define and summarize each important factor in the simulation of open-pit and underground mines. To make the information easier to follow, the conceptual models are presented first (Sections 2 and 3), followed by illustrative and supporting studies (Sections 4 and 5). In the conceptual models, it is important to distinguish between Operation and Closure of a mine, because the MINEWALL computer program uses specific definitions for them.

MINEWALL can estimate water chemistry continuously through the Operational and Closure Phases of a mine. The Operational Phase encompasses the time from when a pit or underground working approaches a relatively stagnant size or its fullest extent to the beginning of Closure. Earlier stages of mining can be simulated by the computer program on a step-by-step basis, rather than continuously. The Closure Phase extends from the end of Operation into the future. The program can simulate up to 500 years of Operation (a mining company's greatest dream!) and Closure at one time.

In addition to this Literature Review, there are three other related reports. The first is a User's Manual for the computer program. In effect, this Literature Review describes the "why" behind the technique and code, whereas the User's Manual is limited to the "how-to" of code operation. However, for proper use of the computer program, the conceptual models in this document should be well understood. This becomes even more critical for simulations of particularly unusual minesites, at which several factors in the conceptual models must be (and can be) manipulated to fit the sites.

The second related report is the Programmer's Notes and Source Code. That document discusses some of the more technical aspects of MINEWALL's programming and contains a listing of MINEWALL 2.0's roughly 24,000 lines of code. The third related report is the Application of MINEWALL 2.0 to Three Minesites, which illustrates ways with which to simulate various conditions at a minesite.

Last Modified: 2003-11-26		Important Notices

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