From: on behalf of Panel Registry Subject: FW: TNG registration of ...

Stratus Consulting Memorandum (4/16/2010)
�� The Proponents estimate that the majority of the mined material will be potentially acidgenerating
(PAG), yet only three of 25 HCTs became acidic with increasing
concentrations of metals, again suggesting flaws in the geochemical testing approach and
methodology.
�� Many of the HCTs show an initial pulse or release of contaminants, but this was not
taken into account in the predictions of contaminant concentrations in water resources.
1.1.2 Short-term leach tests and identification of contaminants of concern
The short-term leach tests were not conducted in a manner that allowed estimation of
contaminant generation. Specific points that Dr. Maest may discuss include the following:
�� Short-term leach tests were too dilute to be used for identification of contaminants of
concern.
�� The elevated concentrations of antimony in the shake flask tests appear to be have been
ignored in modeling of downstream/downgradient transport.
�� Saturated column tests with elevated iron concentrations also had elevated arsenic
concentrations, which was not adequately considered in tailings seepage modeling.
�� The list of contaminants of concern developed by the Proponents ignores other miningrelated
contaminants such as nitrate, nitrite, and ammonia.
1.2 Flaws in Geochemical Modeling
Dr. Maest will also discuss flaws in the Proponents’ geochemical modeling. Some of the topics
that she may discuss in the technical sessions include the following:
�� Contaminants potentially leached from tailings materials stored in the tailings storage
facility (TSF) under either oxidizing or reducing conditions were excluded from the
tailings model.
�� Lag times to acid generation for PAG rocks are greatly underestimated. Using the one
HCT that became highly acidic after 40 weeks as a calibration point, we estimate that the
time to onset of acid for PAG rocks is at least an order of magnitude less than predicted.
Page 3
SC12041