-----Original Message-----
From: Kelly Sexsmith [mailto:ksexsmith@srk.com]
Sent: Wednesday, November 10, 2004 6:56 PM
To: bbennett@acres.com
Cc: missal@tahera.com; srtech@nwb.nunavut.ca; Bruce Ott; Pete McCreath (E-mail)
Subject: RE: Bennett Additional Questions

 

Bruce,

 

For clarity, I have provided brief written responses to the items we discussed earlier today, as follows:

 

Q1

Although Table W2 shows the monthly water balance volumes to and from the PKCA, including storage changes, Table W3 does not show the outflow volumes, contaminant concentrations or loads from the other wastewater streams (as per Figure W1) entering the PKCA.  Is there a summary table of the PKCA contaminant load balance for Total Copper and the other contaminants of concern in another Technical Memorandum?

 

Table W6 provides the concentrations from each of the collection ponds and from the pit sump.  Source concentrations for the inflows to each of these areas are provided in Technical Memorandum I of the Sept 2003 submission.  The entire sept 2003 submission was reissued as part of the water licence application as Appendix BB.  If you require a copy of TM-I , please let me know.

 

Inflows from individual sources to the ponds are proportional to the areas shown in Table W1, part 8 (MAR x area).  I believe these are distributed according to the hydrograph shown in Part 2 of Table W1.  Fine PK supernatant inflows are assumed to come in at a constant rate.

 

Q2

It is our understanding that Total Copper concentration values shown for each of the components (Areas A, B, C and the Pit Pond) were derived as an average from each of the contributing loads to that particular pit.  Hence the reason that the Area Concentration values in Table W3 are less than the corresponding Component Area Concentrations in Table W1.  Is there a summary table showing the individual loads and flow volumes into each Area which, in turn, shows the correlation between the Area Concentration in Table W3 and the Component Area Concentration in Table W1?

 

There is no summary table.  However, I believe with the information from above that you should be able to replicate the calculations.

 

Q3

It is our understanding that the Area Concentration values in Table W3 assumed that the footprint of a particular dump or stockpile was in place at the onset of the project and, therefore as a result of this assumption, provided worst case values throughout the Operational Period of the project.  Is there any information to show an estimate of the Area Concentration values (and the end result on effluent concentrations in the PKCA) at a time near the beginning of the project (for example at the end of the 2007 season) to illustrate the concentration differences that would be expected to occur at the onset of the project compared to the assumed worst case situation at the end of project?

 

We would expect that if a Component Area leached higher than expected contaminant concentrations for a particular parameter which, in turn, led to higher than expected concentrations in the PKCA effluent, then this situation would not occur until near the end of the operational period of the project.  Could you please confirm that the PKCA would have sufficient capacity to store all site area runoff without any releases for a sufficient period of time near the end of the project (to enable the particular contingency measure to be implemented) as opposed to the “first two years of operations” as per page 15 of Technical Memorandum W.  If treatment of a particular parameter was found to be necessary, then we would expect that this situation would not manifest itself at the beginning of the project but rather near the end of the project.   

 

My understanding is that the facility can hold 2 years worth of runoff at any time during operations.  Pete McCreath should be able to confirm this.  A gradual build-up in concentrations should allow Tahera ample time to demonstrate contingencies should they be required in the latter part of the mine life.

 

Q4

Page 14 of Technical Memorandum W states that the “…maximum proposed release rates [from the PKCA into Stream C3] are less than the 5 year to 10 year return period estimated flood flows…” and “…additional overbank flooding or local erosion due to the proposed PKCA releases are, therefore expected to minimal or non-existent”.  Please confirm the basis for this conclusion since one might typically assume that the normal bankfull capacity of a stream channel corresponds to a 2 year return period flow rate.  This would suggest that ‘out of bank’ flows and potential streambank erosion may occur in Stream C3 for the proposed PKCA releases.  Was the bankfull capacity of the existing Stream C3 channel determined in the field or estimated using hydraulic calculations in order to support the latter conclusion?

 

This questions will need to be deferred until Pete is available to address it.

 

 

 

 

 

I understand from Kelly Sexsmith that Questions 1 through 4 have been answered by SRK.  The attached answers Q5.  Our answer is in blue font.

Kind regards

Bruce Ott
Senior Environmental Scientist
AMEC Earth & Environmental
2227 Douglas Road
Burnaby, B.C.  V5C 5A9
Tel. (604) 294-3811
Fax (604) 294-4664
Cell (604) 880-3446
<<Acres Additional Technical Questions-Bennett.doc>>