Several methods to delay the onset of acidic drainage have been tested:

· bactericide application;
· deposition in permafrost;
· phosphate application; and
· irrigation with alkali,

Other methods have been applied as permanent controls but could be designed as delays:

· simple soil covers;
· oxygen-consuming organic covers;
· blending; and
· lime application,

Information about each of the above methods was collected from literature and from interviews with mine operators and researchers. A brief overview of each method is presented, and case histories are described. The extent to which the case histories prove the effectiveness of each method is reviewed.

In general, the review concludes that there is a lack of well-designed and documented studies of methods to delay the onset of acidic drainage. However, several of the reviewed methods are promising enough to warrant further research. A well-designed field study of bactericides is needed to demonstrate whether this method can be effective in metal mine waste. Alkali addition and soil covers are clearly effective for dealing with waste that is already acidic, but their effectiveness as delay methods needs to be demonstrated. Organic oxygen-consuming covers have been shown to be effective for tailings but still need testing on waste rock. Low temperatures have been shown to slow ARD, but further work is needed to quantify the benefits and investigate possible difficulties associated with depositing waste into a permafrost setting.

A list of general requirements for such studies is presented. The review also provides specific recommendations for studies of each method.