Glacier Bytes

Jamieson and colleagues published a very neat investigation of the applied glaciology challenges at Kumtor Mine, Kyrgyzstan, this week in the AGU Journal of Geophysical Research: Earth Surface (open access here). The recovery of subglacial gold deposits at Kumtor Mine has necessitated the excavation of an open ice pit into the Lysii and Davidov Glaciers. In addition to excavating glacier overburden, a major geotechnical challenge at Kumtor Mine has been managing the flow of both glaciers. In their study, Jamieson et al. (2015) use a comprehensive set of high resolution satellite images to document recent artificial surges induced in both these glaciers in response to mining activities. Photos released by Radio Free Europe in 2013 suggest that these artificial surges quite adversely impacted mining operations (Figure 1).

Figure 1 – Infrastructure damage resulting from what is now a confirmed glacier advance at the Kumtor Mine in Kyrgyzstan (originally discussed in this earlier post)

The dumping of waste rock on both glaciers, in which waste rock piles reached up to 180 m thick, substantially increased the driving stress of the ice beneath. Given that ice deformation is related to driving stress to an exponent of three, and potentially higher exponents at higher driving stresses, this resulted in a significant increase in ice velocity. Jamieson et al. (2015) estimate that surface velocities of the Davidov Glacier increased from a few meters per year to several hundred meters per year within a decade. During this time, the Lysii and Davidov Glaciers advanced by 1.2 and 3.2 km, respectively, with Davidov Glacier terminus advance reaching 350 meters per year in c. 2012 (Figure “7”).

This study is probably the most textbook-comprehensive documentation of a human-induced artificial glacier surge to date, and will provide a great resource for my students to debate the sometimes fine line between geotechnical misstep and natural hazard!

Reference

(Jamieson, S., M. Ewertowski and D. Evans. 2015. Rapid advance of two mountain glaciers in response to mine-related debris loading. Journal of Geophysical Research: Earth Surface. 120: doi:10.1002/2015JF003504.

Quick blog on new study of human-induced 3.2 km #glacier surge at #Kumtor mine: http://t.co/mTYVeQDzcb pic.twitter.com/ONMkQETlRm

— William Colgan (@GlacierBytes) July 27, 2015

In August of 2014, a mixed earth and rockfill dam impounding a tailings pond at the Mount Polley Mine in Canada breached¹. Over the following four days, c. 4.5 million m³ of tailings slurry was released into Polley Lake. An expert inquiry reviewed potential causes of the breach: cracking, overtopping, foundation failure, and human intervention. The inquiry noted that “the presence of a glacially pre-sheared surface in the dam foundation posed significant uncertainty throughout the design process”, and, after eliminating overtopping and human intervention, assigned maximum likelihood to the scenario of foundation failure stemming from preferentially oriented glaciolacustrine deposits underlying the dam.

While glaciofluvial deposits and glacial tills were also present beneath the dam, the fine silt and clay of the glaciolacustrine deposits made them the most likely culprit for instability. The presence of glaciolacustrine deposits was well documented in borehole records. In c. 2005 the mine operator (Mount Polley Mining Corporation) recorded that “the glaciolacustrine deposit encountered in [borehole] GW96-1A is a discontinuous unit and will not adversely affect the dam stability”. The breach occurred c. nine years later 300 m due west of borehole GW96-1A.

Breach of the earthen dam at the Mount Polley Mine tailings pond in August 2014 (from CBC.ca).

Although the Mount Polley Mine is located more than 50 km away from present-day glaciers, the site was covered by the Cordilleran Ice Sheet during the last glaciation, which reached a maximum c. 22 kaBP. During the subsequent deglaciation, which lasted until c. 11 kaBP, proglacial rivers and lakes evidently left substantial lacustrine deposits as the ice margin retreated through the site. Despite the last deglaciation ending millennia ago, the strong residual imprint of glacier processes on local stratigraphy compels them to be considered in the design of sensitive infrastructure in formerly glacierized areas.

The Kumtor Mine, Kyrgyzstan, shares some analogous geotechnical challenges with the Mount Polley Mine. At the Kumtor Mine, an earth dam impounds a c. 3.4 million m² tailings pond, which is located c. 7.5 km downstream of the Petrov Glacier. The Petrov Glacier terminates in the proglacial Petrov Lake, which is itself impounded by glacial moraines and tills. Given the equilibrium line lowering and growth of glaciers during the past glaciation², it is very likely that glaciolacustrine and glaciofluvial deposits are present in the vicinity of the Kumtor tailings pond. The growth of Petrov Lake upstream of the tailings pond, from 1.8 to 4.3 million m² between 1977 and 2014 (due to climate change enhancing glacier retreat and melt), presents an additional geotechnical hazard: glacial lake outburst floods upstream of the tailings pond³.

Evolving hydrological and glaciological features in the vicinity of the Kumtor Mine, Kyrgyzstan, between 1977 and 2014.

When existing infrastructure is confronted with such unique geotechnical challenges associated with operating in a proglacial setting, adaptive engineering solutions are often be employed. For example, deformation and creep of glaciolacustrine sediment rich embankments can be monitored with cm-scale accuracy using spaceborne radar, and mm-scale accuracy with ground-based radar. While this may potentially allow embankments to be reinforced as needed, given that the Mount Polley tailings pond instability progressed to a complete breach in just a few days, monitoring alone may be insufficient to avoid a breach. Perhaps the lesson from the Mount Polley Mine, for sites like the Kumtor Mine, is to ensure that unstable glacial sediment is comprehensively identified and factored into robust hazard management and infrastructure design plans!

¹Mount Polley Review Panel. 2015. Independent Expert Engineering Investigation and Review Panel: Report on Mount Polley Tailings Storage Facility Breach. Province of British Columbia.

²Koppes et al., 2008. Late quaternary glaciation in the Kyrgyz Tien Shan. Quarternary Science Reviews. 27: 846-866.

³Jansky et al., 2009. The evolution of Petrov Lake and moraine dam rupture risk (Tien-Shan, Kyrgyzstan). Natural Hazards. 50: 83-96.

Twitter: @GlacierBytes

I have started this open file of selected glacier mining photos and videos with content mostly gleaned from Twitter. At present its coverage is limited to Kumtor Mine, Kyrgyzstan, but I am interested in content that illustrates the unique geotechnical challenges of working with glaciers from other proglacial mining projects too. So please contact me if you have some!

Photos

Open ice pit at Kumtor Mine, Kyrgyzstan in 2013 (via Ryskeldi Satke).

Open ice pit at Kumtor Mine, Kyrgyzstan in 2013 (via Ryskeldi Satke).

An excavator used for glacier mining at Kumtor Mine, Kyrgyzstan (via Ryskeldi Satke).

A glacier cut face at Kumtor Mine, Kyrgyzstan (via Ryskeldi Satke).

Videos

Proglacial mines, meaning mining operations adjacent to, or very close to, glaciers, face a variety of unique glaciological challenges not present in conventional mining operations: (1) Removing ice overburden to access a subglacial ore introduces both ice excavation and ice flow management challenges. (2) In addition to potential crevasse hazards, supraglacial vehicle access roads must use adaptive engineering to counteract ice movement (both horizontal and vertical) as well as differential surface ablation. (3) Tremendous glacier meltwater runoff, concentrated during the summer melt season, can be difficult to route across highly transient glacier surfaces in order to minimize site inflow/contact water. (4) The dust created by open pit operations or access roads can darken the surface of nearby glaciers, enhancing their solar absorption and surface melt rates, and ultimately expand the impact footprint of a mine. (5) The catastrophic drainage of supraglacial and/or ice-dammed lakes represent outburst flood hazards which can rapidly increase site inflow rates. (6) Subglacial hydrology can interact with the groundwater seepage in underground mining operations beneath glaciers. We touch on some of these glaciological hazards in the new textbook: “Snow and Ice-Related Hazards, Risks, and Disasters”. These geotechnical challenges make proglacial mining projects very unique. I started this “open file” inventory of proglacial mining projects (past, present and future) and their associated glaciological challenges as I pull together information for an applied glaciology review paper. Please alert me to any errors or oversights!

Below are some site overview figures, they are available for distribution without attribution tags as well. I hope to make one for each project by the end of 2015. Content on this page can be cited as:

Colgan, W., H. Thomsen and M. Citterio. in press. Unique Applied Glaciology Challenges of Proglacial Mining. Geological Survey of Denmark and Greenland Bulletin.

Figure 1 – The Isua Mine in Greenland: Contemporary ice margins, proposed approximate pit area, and winter 2005/06 ice surface velocity vectors overlaid on a 2014 Landsat image.

Figure 2 – The Kumtor mine in Kyrgyzstan: Historic ice margins and contemporary mine area overlaid on a 2014 Landsat image.

Figure 3 – The Kerr-Sulphurets-Mitchell Mine and Bruckjack Prospect in Canada: Contemporary ice margins, approximate mine surface areas, and proposed supraglacial access roads overlaid on a 2014 Landsat image.

Figure 4 – The El Morro mine in Chile: Contemporary ice margins and mine area overlaid on a 2014 Landsat image.

Figure 5 – The Pascua Lama mine on the Chile/Argentina border: Contemporary ice margins and mine area overlaid on a 2014 Landsat image. The Valadero mine is also visible immediately south of the Pascua Lama mine.

Figure 6 – The Svea Nord / Gruve Mines in Svalbard (Norway): Contemporary ice margins and underground mine area overlaid on a 2014 Landsat image.

Figure 7 – Grasberg Mine in Indonesia: Contemporary mine area and ice margins in a 2003 Landsat image.

When the glaciology lexicon was in its infancy, Carl Benson described glaciers as “monomineralic metamorphic rocks” in his pioneering work with the US Army Engineers¹. Given the lower density and strength of ice than coal, it may seem like glacier ice is an easy overburden to remove for open pit mining. Experience, however, has demonstrated that there are exceptional geotechnical challenges associated with removing glacier ice overburden. These challenges stem from geometry, hydrology and phase, all of which change far more rapidly in glaciers than hard rock². The apparent surge of a waste rock pile at the Kumtor Mine, in Kyrgyzstan, highlights the exceptional geotechnical challenges confronting Centerra Gold in maintaining the world’s largest open ice pit mine.

With glaciers serving as a highly visible indicator of climate change, glacier mining projects often face exceptional social challenges in comparison to conventional hard rock mining projects. The Pascua Lama Mine, which spans the Chile-Argentina border, highlights how glacier preservation is a global movement that adapts to local issues. Glaciers therefore serve as the basis for a “glocal”, or globalized local, social movement³. Barrick Founder Peter Munk has commented on the social challenges confronting Pascua Lama: “It’s not enough to have money, it’s not enough to have reserves, it’s not enough to have great mining people. Today, the single most critical factor in growing a mining company is a social consensus – a license to mine.”⁴

The combination of long term increases in resource demand, retreating glaciers due to climate change, and improved mining technology and prospecting techniques, are making the exploitation of pro- and sub-glacial mineral deposits more feasible. This means a more widespread confrontation of the geotechnical and social exceptionalism of glacier mining in the coming decades!

Glacier and waste rock extent between 1975 and 2013 in the vicinity of Kumtor Mine (from Landsat archive).

Glaciers in the vicinity of the Pascua Lama Mine on the Chile-Argentina border (from WikiCommons).

¹Benson, C. 1962. Stratigraphic studies in the snow and firn of the Greenland ice sheet. Snow, Ice and Permafrost Research Esatablishment. US Army. Research Report 70.

²Colgan, W. and L. Arenson. 2013. Open-Pit Glacier Ice Excavation: Brief Review.
Journal of Cold Regions Engineering. 27: doi:10.1061/(ASCE)CR.1943-5495.0000057.

³Urkidi, L. 2010. A glocal environmental movement against gold mining: Pascua–Lama in Chile. Ecological Economics. 70: 219-227.

⁴Smith, C. 2014. Sustainability Challenges: When Good Intentions Backfire. NSEAD Knowledge

Additional Landsat images of Kumtor here.

I have a paper in this month’s issue of the Journal of Cold Regions Engineering that examines the ice excavation required to establish and maintain an open ice pit. Excavating an open ice pit is a very non-linear applied glaciology problem, as the excavation of ice from an open ice pit enhances subsequent ice flow into the open ice pit. This is because ice velocity is very sensitive to changes in ice geometry, with third and fourth order dependencies on ice slope and thickness respectively! The paper examines scenarios based on excavating an open ice pit on the Greenland ice sheet margin that extends 1000 m into the ice sheet, with a 200 m high ice wall. That is the approximate dimension of the Isua Prospect, Greenland, which is projected to excavate about 36,000,000 tonnes of glacier ice per year.

Working with such unnatural combinations of ice slope and ice thickness compels you to reconsider fundamental principles of glacier mechanics, such as the appropriate relation between stress and strain at tremendous basal shear stresses, which are inconceivable in virtually all natural glacier settings. Despite an increasingly pressing need for a comprehensive understanding of how glaciers respond to highly transient forcings, however, most private sector glacier management projects cannot contribute meaningful observational data to advance such fundamental science due to proprietary considerations. Perhaps that can change in the future!

W. Colgan. 2014. Considering the ice excavation required to establish and maintain an open ice pit. Journal of Cold Regions Engineering. 28: 04014003. doi:10.1061/(ASCE)CR.1943-5495.0000067. Available here.

Supplementary online material (including animations): http://www.williamcolgan.net/som/CRENG113

Cross sectional ice velocities flowing into an open ice pit at excavation years 2.5 (left) and 10.0 (right) sampled from 30-year animations. Dashed black line denotes original ice surface, dash red line denotes ice pit wall. (from Colgan, 2014)

Last week Radio Free Europe released some photos of the Kumtor Gold Mine in Kyrgyzstan, where Centerra Gold Inc has been excavating approximately 10 MT of ice per year from the Lysii and Davidov Glaciers that flow into the open pit. In 2012 Mining.com reported that production estimates were down-revised due to a combination of “substantial acceleration of ice” and labor disruptions. These recent photos show infrastructure damage resulting from what appears to be glacier advance.

While no doubt curious, such a geotechnical management challenge would not be unique. In 1977, Eyles and Rogerson described how several positive mass balance years on the Berendon Glacier in Canada could cause sufficient terminus advance to threaten the adjacent Granduc Operating Company ore processing plant. In response, the Granduc Operating Company began discharging 30°C wastewater, year-round for five years, directly on to the glacier terminus to prevent advance. Glaciers are indeed dynamic landscape features for planning purposes!

Radio Free Europe photo series: http://www.rferl.org/content/qishloq-ovozi-kumtor-gold-mine-bad-shape/26555319.html

Eyles, N. and R. Rogerson. 1977. Artificially induced thermokarst in active glacier ice: An example from northwest British Columbia, Canada. Journal of Glaciology. 18: 437–444.

Infrastructure damage resulting from what appears to be glacier advance at the Kumtor Mine in Kyrgyzstan (from Radio Free Europe: Kumtor Gold Mine Appears To Be In Bad Shape)

Intentional thermokarst of the Berendon Glacier by the Granduc Operating Company. Red line denotes Summit Lake stream, which has been diverted upglacier at A. Hot waste water is added at B, and flow is subglacial until C. The stream exits the glacier terminus at D. (from Eyles and Rogerson, 1977)