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MDAG.COM
MINES, MINING, AND THE ENVIRONMENT







MDAG.com: Since 1997, Providing Valuable Technical Information on Minesite-Drainage Chemistry and Environmental Geochemistry through the Internet

The 20th Anniversary of This Website,
the 20th Anniversary of Environmental Geochemistry of Minesite Drainage: Practical Theory and Case Studies,
and the 35th Anniversary of Morwijk Enterprises,
are Being Celebrated by Free Books, Spreadsheets, and Papers

 


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Case Study #48, The MDAG Dynamic ARD-Onset Simulator, can now be downloaded.  This simplified spreadsheet-based model simulates and visually displays the onset, growth, and migration of ARD in a vertical cross-sectional grid.  The grid contains user-specified net-acid-generating cells within a matrix of net-acid-neutralizing cells. A separate PDF document contains details, instructions, and examples for this model.

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Case Study #47, A Case Study Revisited of Full-Scale ARD from a Waste-Rock Pile with Abundant Reactive Neutralization Potential, can now be downloaded.  More than 8000 measurements of in-field rinse pH, during removal of a full-scale waste-rock pile releasing ARD, provide some new information!

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Case Study #45, A Case Study of Rapid Water Flow through Full-Scale Waste-Rock Piles, can now be downloaded.

Case Study #46, A Case Study of High-Frequency Time Series for Individual Chemical Elements in Waste-Rock Drainage, can now be downloaded.

For decades, full-scale waste-rock piles have been recognized as complex minesite components in all three spatial dimensions and through time. While many waste-rock investigators recognize this complexity of coarser and finer material, many ignore its reality and oversimplify water movement in the coarser material. It appears the primary reasons for this are:
(1) the lack of high-frequency monitoring data (hourly and more frequently) to characterize the rapid flow of water through full-scale waste rock;
(2) detailed studies of smaller "test piles" and laboratory columns that are unavoidably unrepresentative of full-scale waste rock; and
(3) the desire to model water flow through waste rock despite a lack of realistic equations to simulate turbulent, non-Darcian, non-capillary flow in coarse rock.

MDAG Case Study 45 helps here by reviewing one previous case study of rapid flow through a full-scale pile. Then the subsequent sections present a new case study, based on new interpretations of an existing high-frequency monitoring database of waste rock. For example, after minimal "wetting up" of tens of meters of full-scale, run-of-mine waste rock (wetting of ~1% or less of rock volume), rapid flow occurred within 0-2 days after peak precipitation, sometimes persisting for only 15-60 minutes. For prominent one-day peaks of precipitation, 75% or less of the volume of precipitation passed through the local waste rock in less than a day or two.  

MDAG Case Study 46 carries on by showing that aqueous high-frequency chemical concentrations in the minesite drainage of Case Study 45 can be significantly autocorrelated and cross correlated. Close examination of individual time series showed that, during storms at this minesite, daily outflows at the stations often increased sharply by 400-900%. Simplistically, this may lead one to expect aqueous concentrations to decrease substantially through dilution.  Instead, aqueous concentrations of some parameters decreased by no more than 35%, some showed little correlation with flow or pH, and some increased in concentration (the opposite of dilution). These trends in concentrations highlighted how quickly infiltration could accumulate chemical constituents during the hours it passed through the waste rock, and confirmed 1:1 positive or inverse correlations with flow are not observed. Overall, trends in aqueous concentrations differed among elements and parameters, among the selected time periods, and before and after brief significant changes in pH.

Also, a standard predictive technique for minesite drainage divides an estimated geochemical loading by an estimated flow to obtain a predicted full-scale concentration. This assumes a 1:1 inverse correlation of flow and chemistry, which violates documented relationships between flow and aqueous concentrations on several scales and in mining-related and non-mining-related catchments.  Therefore, this standard predictive technique is based on error, is unreliable, and should be abandoned.

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Free for personal use, the new book entitled, "Spectral Analysis of Drainage from Highly Reactive Geologic Materials" (ISBN 978-0-9952149-1-0), is now available for download here at MDAG.com.

This book contains a novel and unconventional approach for interpreting and understanding the flows and chemistries of field-scale drainages from reactive geologic materials. Recent advances in other sciences are adapted and applied to drainage, with emphasis on emergent properties important at larger scales. As the Preface points out about this novel approach, "Now I understand better what that past work was trying to tell me."

MDAG Case Studies 43, 44, 45, and 46 expand on some issues raised in the book.


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Interested in minesite-drainage chemistry, but not sure where to start? Looking for a basic introduction with dozens of colour photographs from minesites around the world?

MDAG Publishing has released a free ebook by Dr. Kevin Morin, entitled Minesite Drainage Chemistry: An Introduction. This printable ebook in PDF format can be read on many ebook readers, laptops, and desktops. This free ebook can be downloaded immediately, and contains no digital-rights management or security limitations.

Click here, and then scroll down to the link for the ebook.


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We have also published many informative papers at conferences and in journals, as well as Internet case studies and books here at MDAG.com.
 

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We steadfastly believe that the environmental effects of drainage chemistry can only be understood, predicted, and moderated by thoroughly understanding past competent work and by carefully studying existing operations and sites. Heed the old words of wisdom: "Those who ignore the past are doomed to repeat it". Is that why we hear that up to 90% of predictions of minesite-drainage chemistry are too low, leading to unexpected costs and adverse environmental effects for mining companies?  This is why we heavily emphasize real case studies with abundant data, followed by theory and modelling in subordinate roles.

 

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