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PhosphoGypsum Disposal 

 
Authors: Jack Caldwell

Summary

This review describes the design, construction, operation, and closure of gypsum tailings stacks (tailings impoundments) in Florida and elsewhere around the world. Consideration is given to site selection, foundation preparation, liners, waste placement and geometry, slope stability, covers, erosion, infiltration, and environmental impact for gypsum and phosphogypsum mining and industrial wastes.

INTRODUCTION

Phosphogypsum Piles or waste disposal facilities are a long way down the line from a typical mine. But the technologies they demand are of interest to the mining practitioner, and hence are discussed here. I put this compendium together for a colleague as a favor, so might as well share it now.

Keep in mind that a quick Google search with key words will bring you up-to-date information. Of course you will have to sort through more than you ever could read, but who knows what gems you will stumble across. Maybe the following brief overview will save you a long trek...Gypsum Pile

Design & Regulations

The regulatory background governing gypsum stacks in Florida is well summarized in a Poly-Flex LineReport. The most significant requirement is of course the need for a liner beneath the stack to protect groundwater.

Photos

Photos of gypsum piles are to be found at this site that has no name or affiliation I can find: http://www.fluoridealert.org/phosphate/photographs2.htm

See Tailings Dam Failure for photographs of spectacular failures of gypsum impoundments in Florida, Kentucky, and South Africa. No details given unfortunately in this UC Davis file.

Environmental Impact

The United Nations in 2001 put out a 68-page book that cover the topic from all angles-see "Environmental Aspects of Phosphate and Potash Mining."

Impoundment Design

An interesting example of an early Phosphate & Gypsum Impoundment constructed in difficult conditions can be found

Reclamation

The University of Florida in 1988 published a 193-page book on reclamation-see "Reclamation of Phosphatic Clay Waste by Capping" Some interesting ideas on covers in wet climates and covers to cover wastes that will continue to settle significantly after closure.

Uranium Tailings

Comparison to Uranium Mill Tailings

See the U.S. EPA study comparing the standards that govern uranium mill tailings and phosphogypsum Impoundments. Keep in mind that gypsum tailings can be radioactive and hence are considered akin to uranium mill tailings.

Contamination

The impact of gypsum mining on birds in North Carolina is described in the U.S. Fish & Wildlife Service report.

Groundwater Impact

Re potential groundwater contamination for South African gypsum tailings and the fluoride therein is discussed by Motlane and Strydom from the University of Pretoria.

EP on Phosphogypsum

Lots of EPA comings and goings recorded on this site: http://www.wise-uranium.org/ptail.html

Discussion of Environmental Impact

As always there is a debate about this topic. Some sites you may want to see to brush up on the issues:

Mechanical Dewatering

One way of decreasing the risk to the environmental is to use less are for your tailings pond. This involves dewatering the tailings mechanically in order to optimise your storage space. In this case in Belgium they would seem to view it as less of an environmental concern, and more of an issue with planning and space, "in a country where space is a problem".

Reclamation

Reclamation

Florida Phosphate Facts includes a good basic description of stacks from design through closure.

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