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

Stratus Consulting Memorandum (4/16/2010)
The net result is a potential underestimate of seepage, and thus an overestimate of the ability of
the TSF to retain water and maintain saturated conditions for PAG waste. The large range of
uncertainties in hydraulic conductivity in bedrock beneath the TSF also underscores the
uncertainty in the magnitude and timing of groundwater contamination reaching Big
Onion Lake.
2.3 Issues With Water Balance Model
The Proponents’ baseline precipitation and streamflow data are inadequate to characterize the
inflows and outflows to their water balance model. The net result is that their water balance
likely has far greater uncertainty than represented by their probabilistic model.
2.3.1 Precipitation and runoff data
We identified several issues with the precipitation and runoff data that the Proponents used in
their water balance model. Most of these issues were raised in our November report, and we
were unconvinced by the Proponents’ responses. Some example issues that Dr. Maest may
address include the following:
�� Site-specific precipitation data are of very poor quality and are unreliable. The
Proponents acknowledged as much, discarding many of the site-specific data and
suggesting that they were erroneous.
�� Modeled long-term precipitation trends are based on correlations between one site near
the mine and one distant site. However, in the two years for which they Proponents had
data from each site, there did not appear to be any correlation between measured
precipitation near the mine and measured precipitation at the distant site used for the
long-term modeling, thus introducing a potentially large and unquantifiable uncertainty
into the water balance.
�� The most recent estimate of mean annual unit runoff (MAUR) – the key parameter upon
which inputs to the water balance are based – appears to be derived from a single year of
data from a single meteorological station. The low estimate of MAUR appears to have
been obtained from a different gauge during the same year. We question the use of two
data points from the same year to characterize the range of potential interannual
variability in unit runoff.
The Proponents have revised the water balance model several times since the initial EIS was
released. Each iteration of the water balance modeling yields considerably different results than
the previous iterations, providing another indication that the Proponents do not have a solid grasp
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