----Original Message-----
Sent: Friday, July 20, 2012 2:04 PM
To: Hamilton, Chris EAO:EX; James, Tracy A EAO:EX
Subject: Diffuser and hotspots
Dear Chris,
Following on from our quick discussion in which you expressed that some stakeholders have concerns about my review of the proponent's Morrison Lake water quality predictions, there isn't much I can add to my report. In summary I was asked to assess the preliminary design of a diffuser that will provide initial dilution of treated effluent, as well as to assess the impact of seepage from a proposed tailings storage facility. Using what I think is a more appropriate set of assumptions than those used by the proponent, I treated the proposed treated effluent inflow into the lake hypolimnion as a negatively buoyant fountain filling box, and showed that a minimum 100:1 dilution could be attained over summer stratified period with a properly designed single port diffuser, even considering a prolonged summer stratified period due to climate change. Even higher dilution could be obtained with a multi-port diffuser. At 100:1 dilution there is no concern of developing density stratification that cannot be mixed by seasonal overturn. If fully lining the tailings storage facility with a geomembrane prevents seepage from entering into Morrison Lake and creeks entering Morrison Lake, then there is no concern with hotspots due to this seepage. The report is fully documented and there is enough information in the report and works cited that anyone with the input data provided by the proponent could reproduce what I have done.
I will be away on holidays for the next three weeks.
Regards,
Bernard
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Bernard Laval, Associate Professor
Associate Head for Undergraduate Programs Department of Civil Engineering,
University of British Columbia
6250 Applied Science Lane, Vancouver, BC, Canada,
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