Geotechnical Society of Edmonton

NEWS 2007

Posted September 17, 2007

Event September 27, 2007

2007 GSE Annual Wine and Cheese and University of Alberta Student Presentations

The first event in the Geotechnical Society of Edmonton's 2007-2008 calendar is the annual U of A Wine and Cheese. The two student presentations of the evening are:

Approaches to Achieve Non-Segregating Tailings with Higher Solids Content
Reza Moussavi Nik, PhD Candidate, Geotechnical Engineering Program.

Management of oil sands tailings in Alberta uses production of CT, which is a non-segregating tailings (NST) stream produced by addition of phosphogypsum to a mixture of mature fine tailings and cyclone underflow. A challenge for the industry has been achieving a robust NST which can hold higher angles on deposition, a behaviour which is mainly governed by its water content. The present research deals with studying different methods of making a robust NST, either by further enhancing the solids content of CT, or by dewatering its components (i.e. MFT/Cyclone UF) separately before mixing to make a more concentrated final product. A part of this work has been studying effect of inclination and use of thin layers as an approach for enhanced dewatering of CT (>60%wt solids content). Some sedimentation tests were conducted for CT in vertical and inclined standpipes. Also the rate of dewatering has been studied for different placement thicknesses of CT layers on inclined plates at various angles and different friction on the inclined surfaces. The results indicate that use of inclination along with dividing a thick stream of CT into multiple thinner layers enhances dewatering of the material significantly. Currently some other methods of solid-liquid separation like centrifuging and centrifugal filtration are under review to decide about their practicability in the process of making Non-Segregating Tailings.

Behaviour of Spilled Petroleum Hydrocarbon at Colomac Mine Site, NWT
Olumide Iwakun, Ph.D. Candidate, Geoenvironmental Engineering Program.

Over 50,000 liters of diesel fuel were spilled around the tank farm area at the abandoned Colomac gold mine site between 1990 and 2003 resulting in subsurface contamination adjacent to Steeves Lake. The site is 220 km northwest of Yellowknife and operated between 1990 and 1997 before closure in 1999. The site has 0.5 to 3 m overburden underlain by fractured bedrock. This paper is part of the ongoing characterization of fuel spillage at the site and focused on the behavior of free phase hydrocarbon as light non-aqueous phase liquid (LNAPL) in the permafrost fractured bedrock. The upper seven meters of the bedrock has localized fractures with moderate to high permeability and the ongoing characterization suggests the contamination is limited to the upper fractured zone of the bedrock. The product recovery tests and monitoring of apparent LNAPL thickness in the wells suggests that seasonal groundwater fluctuations and slow intermittent release of residual LNAPL from the overburden and bedrock surface through permeable zones around the well bores may be the active mechanisms contributing to seasonal variation of LNAPL in the monitoring wells. The study also showed that recovery of residual LNAPL in the formation may not be feasible; however, further investigation is required to resolve uncertainty in proposed mechanisms responsible for low LNAPL recharge in the wells.

Generously Sponsored by: Thurber Consultants and Almita Manufacturing

Location: Univeristy of Alberta Faculty Club
Time: 5:30pm Reception, Presentations start at 6:30pm
Date: Thursday, September 27, 2007
Cost: Students: $5, GSE Members: $5, Non-members: $10
Space limited. Please confirm attendance no later than Tuesday, September 25, 2007,
by emailing sean.birch@amec.com

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