There has been much criticism of the draft Environmental, Health and Safety Guidelines for Mining recently published by the World Bank. They have been criticized for failing to specify performance levels or quantitative measures necessary to protect local communities and environments impacted by mines.

At about the same time as I read the Guidelines, I read the August 2007 issue of the venerable magazine, Civil Engineering. In this issue I notice a paper The Vision for Civil Engineering in 2025. I copy the following from that paper—keep in mind this is a sort of presentation from a conference assumed to take place in 2025.

The application of global, performance-based codes and standards has become widespread in enhancing the world’s infrastructure, and civil engineers have been at the forefront in developing such guidelines. To address heightened threats and threat variability from place to place, global codes and standards have become risk based, thereby more readily addressing local conditions. Threats from natural disasters and terrorism continue to change as world conditions evolve, and the developers of codes and standards have become more proficient and proactive in adapting standards accordingly. In addressing the variations in local risk, engineers are also educating society on the limitations of new technology so that expectations can be properly managed and informed decisions can be made on how infrastructure is constructed.

Notice that criticism of the World Bank Guidelines is that they are not performance oriented. And notice the enthusiasm for performance-based standards from future civil engineers. This got me thinking about the specifics of performance-based standards. Here are a few extracts I found on the web.

From the National Fire Protection Association:

Performance-based codes and standards specifically state their safety goals, and reference approved methods that can be used to demonstrate compliance with their requirements. The document may be phrased as a method for quantifying equivalencies to an existing prescriptive-based code or standard, or it may identify one or more prescriptive codes or standards as approved solutions. Either way, the document allows the use of any solution that demonstrates compliance.

The performance-based design process: One whose safety solutions are designed to achieve a specified goal for a specified use or application. This process allows performance-based documents to be implemented and insures that their goals are met. The following describes a performance-based design procedure:

a. Establish safety goals

b. Evaluate the condition of the occupants, building contents, process equipment or facility in question with regard to safety

c. Identify potential hazards

d. Define appropriate hazard scenarios

e. Establish performance objective and performance criteria

f. Select suitable calculation methods (e.g. computer models)

g. Develop a proposed solution

h. Assess the proposed solution

i. Obtain approval of the proposed solution.

From a document without a cover or title:

A performance based standard states goals and objectives to be achieved and describes methods that can be used to demonstrate whether or not products and services meet the specified goals and objectives. Contrast a prescriptive standard, which typically prescribes materials, design and construction methods frequently without stating goals and objectives. A performance based standard focuses on desired characteristics of the final product, service or activity rather than requirements for the processes to produce it. Note that performance based standards are also known as objective based standards. Many ASME standards include both prescriptive and performance elements, but most lean heavily towards being prescriptive standards.

What are the advantages of performance based standards? Performance based standards allow users flexibility in choosing materials, design and construction to meet the standards’ goals and objectives. Advantages include:

  • New Technology – Performance based standards allow earlier use of new technology. The users of these standards are free to implement new technology as soon as it is demonstrated, without waiting for standards development committees to modify standards to explicitly permit use of new technology.
  • Innovation – Performance based standards encourages people to find optimum ways to meet performance criteria, which results in building the knowledge base and developing the entrepreneurial spirit, which in turn leads to economic development
  • Barriers to Trade – Performance based standards permit the use of new or nontraditional parts and methods when their use meets the performance criteria. This widens the marketplace, no longer limiting the acceptable suppliers to those manufacturers or countries with specific resources.
  • Transparency – Performance based standards that have clearly stated goals and objectives answer the question of what is to be achieved. For most prescriptive standards, the goals and objectives are implied at best and unknown at worst. For many rules in prescriptive standards, we cannot answer with certainty the question of what end function is to be achieved.
  • Efficiency – The development and maintenance of performance based standards ultimately requires less effort. While initially more difficult to establish goals and objectives, the decision for inclusion or not of various requirements is much simpler. Maintenance can be simpler as well. For example, a standard that describes the properties of acceptable materials of construction is much easier to maintain than one that lists acceptable materials by reference to various material standards.

In scouring the web I notice that performance-based standards have been use in these situations:

Let us take but one small part of the International Finance Corporation’s (IFC) World Bank guidelines and examine it in the light of these ideals and pronouncements. I select what they say about heap leach pads, simply because I am reasonably familiar with such facilities. Here are the IFC guidelines for heap leach pads:

Leaching: Operators should design and operate surface heap leach processes with:

  • Adequate liners and sub-drainage systems to collect, recycle, or treat solution, and minimize ground infiltration;
  • Pipeline systems carrying pregnant solutions should be designed with secondary bunded protection;
  • Leak detection equipment should be installed for pipeline and plant systems
  • Evaporation ponds and other impoundments should be lined, and be equipped with leak detection systems;
  • Sufficient monitoring wells should be installed around leach pads to enable monitoring of water levels and quality.

Recommended practices for the management of leach-pad waste include the following:

  • Leachate collection and treatment should continue until the final effluent criteria are consistent with guideline values in Section 2.0;
  • Leach pad material should be properly covered once leachate quality reaches acceptable discharge water quality in order to avoid water resource contamination due to infiltration.

Let us compare the IFC requirements to guidelines in some of the states of the USA. The only useful code (to my knowledge) from any of the states where heap leach pads are common is from Utah, namely Design and Construction Guidance Document for Precious Metals Heap Leach Extraction Facilities. Published in 1998, this document provides comprehensive practical information. This guidance document summarizes heap leach requirements in other states. For example, compare these requirements for the liner in different states:

Colorado: Double lined; minimum one synthetic liner; soil liner k = 10-6 cm/sec.

Idaho: Continuous liner; natural or manmade; soil liner k = 10-7 cm/sec; thickness = 12 inches.

Nevada: Composite liner or equivalent; soil liner on soil k = 10-7 cm/sc; 12 inches thick.

Utah: cases leach pads should be designed to allow no discharge of process fluids, and should incorporate a leak detection system for compliance monitoring. Most mine sites in mountainous areas will have deep ground water and complex geologic structure, which could make ground water monitoring difficult and expensive. In these cases, the leak detection system for the leach pad should be sealed from the underlying ground in such a way as to assure that fluids will not escape even if there is a leak in the primary liner and fluids collect in the leak detection system. Leach pad projects must obtain a construction permit from DWQ before construction may begin, in addition to a ground water discharge permit. An example of an acceptable liner approach that could stand alone and not need ground water monitoring would include the following components, from top to bottom

  1. The stacked ore.
  2. A granular cushion layer to protect underlying liners.
  3. The process fluid collection system.
  4. The primary liner – an 80-mil thick geomembrane (compatible with leachate chemistry) in intimate contact with a 12-inch clay layer of hydraulic conductivity 1x10-7 cm/sec or less.
  5. A barrier geotextile to prevent mixing of the clay with the underlying leak detection medium.
  6. A leak detection medium of hydraulic conductivity of 1x10-2 cm/sec or greater, either granular material (sand/gravel) or a synthetic geonet.
  7. Leakage collection and conveyance piping.
  8. A leak detection system seal. In areas of high to moderate ground water vulnerability with good quality ground water, the seal should consist of a 60-mil thick geomembrane overlying 12 inches of clay with hydraulic conductivity of 1x10-7 cm/sec or less. In areas with less vulnerability or poorer quality ground water, either the membrane or clay layer may be used alone.

Hydraulic head on the primary liner should be minimized to no more than one foot, so a “head break” design is not needed as in process water ponds. Valley fill or other designs requiring construction on slopes of 7 percent or greater are discouraged because of the low strength of liner materials. Different design criteria will apply if construction under these conditions is necessary. Leach pads intended for repeated uses will require additional structural reinforcement to insure liner integrity. Alternative designs that achieve the same or better protection of ground water may be utilized with Division approval.

These Utah and other state guidelines are primarily prescriptive. But at least they are considerably more useful, informed, and protective of the environment than the IFC guidelines.

This is what I would expect from a relatively comprehensive feasibility study evaluation of a heap leach pad. At a minimum, describe the following:

  • The nature of the ore, including its response to placement on the pad (will it crush to a low permeability mass?)
  • The lixiviants proposed for application to the heap leach pad
  • Laboratory tests (preferably column tests) that prove that the proposed lixiviants will liberate the sought metals from the ore
  • Test data to demonstrate that the leachate from the heap leach pad can practically and cost-effectively be treated in the plant to finally yield the mined metals.
  • A description of a feasible layout of the proposed heap leach pad, how it will be built, operated, and closed, and a rationale about why it will be stable and not negatively impact the environment or human health & safety.

In the final analysis, the Feasibility Study has to persuade the regulator that the project is feasible and that you are not fooling the public and investors. You will have to prove that it is technically and economically possible to build, operate, and close the heap leach pad.

If you are required to prepare an Environmental Impact Statement (EIS) or equivalent, you will find that much of the information in the Feasibility Study (or equivalent) can be used in the EIS. But you will have to go further, for the EIS is concerned primarily with the interaction of the heap leach pad and the environment than the Feasibility Study. Thus you will have to document:

  • The size, layout, and geometry of the heap leach pad
  • The components that will ensure stability, integrity, and safety
  • The surface water management system to be constructed to limit runon and control runoff
  • The quantity of water that will be used and where that water will come from
  • The quality of the runoff and what will be done to make sure you do not contaminate surface water
  • The liner system and how it will function to protect groundwater
  • Erosion control features and predicted erosion patterns during operation and post closure
  • Closure intentions including cover construction, revegetation, monitoring, and potential remedial actions and responses

Ultimately in the EIS (or equivalent) you will have to document data, studies, and calculations to prove that the heap leach pad will not detrimentally impact the environment or people. And to the extent there are predicted negative impacts, you will have to prove that mitigation will be undertaken and will be effective.

If one has to do this much for stock exchanges, investors, and regulators, surely you should have to do something similar before you can get money from the World Bank.

Maybe it does not even have to be so complex. Maybe all we should demand is the correct answer to these two questions before we let the World Bank finance a new mine that involves a heap leach pad.

1) Are the heap leach pad materials acid drainage generating, and if they are how will the mining company avoid water treatment in perpetuity?

2) Can the mining company ensure geomorphic stability of the closed heap leach pad the absence of perpetual maintenance?

The point is that the IFC guidelines are simplistic. It matter not whether they are prescriptive or performance based. They are simply inadequate, period.