Syncrude Tailings Dam
Encyclopedia
The name Syncrude Tailings Dam often refers to the Mildred Lake Settling Basin (MLSB). This is an embankment dam
that is, by volume of construction material, the largest dam in the world. It is located 40 km north of Fort McMurray, Alberta
, Canada
at the northern end of the Mildred Lake lease owned by Syncrude Canada Ltd.
. The dam and the tailings
artificial lake within it are constructed and maintained as part of ongoing operations by Syncrude
in extracting oil from the Athabasca Oil Sands
. Other tailings dams constructed and operated in the same area by Syncrude
include the Southwest Sand Storage (SWSS), which is the third largest dam in the world by volume of construction material after the Tarbela Dam
.
Two starter dams were constructed during 1976 to 1978 and were required until sufficient sand was available for building the embankments. The north starter dam had a crest elevation of 312 m. The original ground surface varied from 294 m to 305 m while up to 1.5 m of original ground was stripped for a trench above which was a compacted clay core. The crest width was 30 metres.
The main embankment was taken to a final elevation of 352 m for more than half of its length by 1994 and completed in 1995. For construction purposes the embankment was considered to be in a collection of 30 “cells”, each with a crest length of about 600 metres. Acceptable side slopes were determined on a cell-by-cell basis, based on the strength of available materials and foundation movement. The slope of the outer part of the embankment is much smaller than that of the inner part, in a ratio of about 4:1.
As this dam is frequently appears in lists as the largest dam structure in the world, it is necessary to estimate the accuracy of the quoted volume of construction material. The quoted the length of the embankment of 18 km is reliable. The average height of the embankment is quoted to be 40 m, and a check on this using four cross sections yields 45 m, which is of the same order of magnitude. The average base width of the embankment is variously 1,800 m, 800 m from Google Earth and 660 m. So whereas one report gives an embankment volume of 720×106 m3, calculations based on the width of the embankment base from these three sources give embankment volumes of 660, 290 and 240×106 m3 respectively. So there's some uncertainty as to the total volume of construction material
The embankment length is 19.5 km. The maximum embankment height is at least 30 m and the average embankment height is about 18.5 m. The average embankment base width is about 800 m from Google Earth. So the total embankment volume is about 145×106 m3.
The embankment length is 11.6 km and the average embankment base width is about 260 m from Google Earth. The surface elevation is 341.4 m.
Embankment dam
An embankment dam is a massive artificial water barrier. It is typically created by the emplacement and compaction of a complex semi-plastic mound of various compositions of soil, sand, clay and/or rock. It has a semi-permanent waterproof natural covering for its surface, and a dense, waterproof...
that is, by volume of construction material, the largest dam in the world. It is located 40 km north of Fort McMurray, Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
at the northern end of the Mildred Lake lease owned by Syncrude Canada Ltd.
Syncrude
Syncrude Canada Ltd. is the world's largest producer of synthetic crude oil from oil sands and the largest single source producer in Canada. It is located just outside Fort McMurray in the Athabasca Oil Sands, and has a nameplate capacity of of oil, equivalent to about 13% of Canada's consumption...
. The dam and the tailings
Tailings
Tailings, also called mine dumps, slimes, tails, leach residue, or slickens, are the materials left over after the process of separating the valuable fraction from the uneconomic fraction of an ore...
artificial lake within it are constructed and maintained as part of ongoing operations by Syncrude
Syncrude
Syncrude Canada Ltd. is the world's largest producer of synthetic crude oil from oil sands and the largest single source producer in Canada. It is located just outside Fort McMurray in the Athabasca Oil Sands, and has a nameplate capacity of of oil, equivalent to about 13% of Canada's consumption...
in extracting oil from the Athabasca Oil Sands
Athabasca Oil Sands
The Athabasca oil sands are large deposits of bitumen, or extremely heavy crude oil, located in northeastern Alberta, Canada - roughly centred on the boomtown of Fort McMurray...
. Other tailings dams constructed and operated in the same area by Syncrude
Syncrude
Syncrude Canada Ltd. is the world's largest producer of synthetic crude oil from oil sands and the largest single source producer in Canada. It is located just outside Fort McMurray in the Athabasca Oil Sands, and has a nameplate capacity of of oil, equivalent to about 13% of Canada's consumption...
include the Southwest Sand Storage (SWSS), which is the third largest dam in the world by volume of construction material after the Tarbela Dam
Tarbela Dam
Tarbela Dam on the Indus River in Pakistan is the second largest dam in the world by structural volume. It is located in Haripur District, Khyber Pakhtunkhwa, about northwest of Islamabad.The dam is high above the riverbed. The dam forms the Tarbela Reservoir, with a surface area of approximately...
.
All Syncrude Tailings Dams
Syncrude Canada Ltd has oilsands mining operations on three lease areas (Mildred Lake, Aurora North and Aurora South), all about 40 km north of Fort McMurray. There are many tailings dams on those leases. The lease that has the greatest number of tailings dams, and the largest tailings dams, is the Mildred Lake lease. The Mildred Lake and Aurora North leases together contain: the Mildred Lake Settling Basin (MLSB), Southwest Sand Storage (SWSS), West In-Pit (WIP), East In-Pit (EIP), Southwest In-Pit (SWIP), Aurora Settling Basin (ASB) and Aurora East Pit Northeast (AEPN-E). Those referred to as “in pit” have only small containing embankments. In Aurora South lease the main tailings dam will be the External Tailings Area (ETA). This doesn’t exist in 2010, construction will start before 2016.| Site | Facility | | Fluid Fine Tails (106 m3) | | Water (106 m3) | | Total Fluid (106 m3) |
|---|---|---|---|---|
| Mildred Lake | MLSB | 196.5 | 13.4 | 209.9 |
| Mildred Lake | SWSS | 46.3 | 10.1 | 56.4 |
| Mildred Lake | WIP | 168.6 | 22.9 | 191.5 |
| Mildred Lake | EIP | 0.1 | 2.5 | 2.6 |
| Mildred Lake | SWIP Jr. | 1.2 | 0.3 | 1.5 |
| Mildred Lake | SWIP Major | 13.2 | 28.6 | 41.8 |
| Aurora North | ASB | 76.7 | 48.3 | 125.0 |
| Aurora North | AEPN-E | 0.21 | 0.81 | 1.01 |
Mildred Lake Settling Basin (MLSB)
The Mildred Lake Settling Basin is located on the north side of the Mildred Lake lease area. It is a tailings pond that serves three purposes. Firstly, the embankment was planned as storage for a substantial volume of sand. Secondly, the basin acts as a storage basin for process water, which is recycled, with a planned ultimate storage capacity of 350×106 m3. Thirdly, the fines that are not captured elsewhere settle and compact in the basin, and are later pumped out for long term storage. This means that the MLSB is a true dam in the sense that it is filled with water in the long term, rather than being quickly filled by solids as in many other tailings dams. The embankment has a circumference of about 18 km, an average height of about 40 m and a maximum height of about 88 m.Two starter dams were constructed during 1976 to 1978 and were required until sufficient sand was available for building the embankments. The north starter dam had a crest elevation of 312 m. The original ground surface varied from 294 m to 305 m while up to 1.5 m of original ground was stripped for a trench above which was a compacted clay core. The crest width was 30 metres.
The main embankment was taken to a final elevation of 352 m for more than half of its length by 1994 and completed in 1995. For construction purposes the embankment was considered to be in a collection of 30 “cells”, each with a crest length of about 600 metres. Acceptable side slopes were determined on a cell-by-cell basis, based on the strength of available materials and foundation movement. The slope of the outer part of the embankment is much smaller than that of the inner part, in a ratio of about 4:1.
As this dam is frequently appears in lists as the largest dam structure in the world, it is necessary to estimate the accuracy of the quoted volume of construction material. The quoted the length of the embankment of 18 km is reliable. The average height of the embankment is quoted to be 40 m, and a check on this using four cross sections yields 45 m, which is of the same order of magnitude. The average base width of the embankment is variously 1,800 m, 800 m from Google Earth and 660 m. So whereas one report gives an embankment volume of 720×106 m3, calculations based on the width of the embankment base from these three sources give embankment volumes of 660, 290 and 240×106 m3 respectively. So there's some uncertainty as to the total volume of construction material
South West Sand Storage (SWSS)
The SWSS facility is located in the southwest corner of the Mildred Lake lease area. It was commissioned in 1993. The facility was designed to provide coarse tailings sand storage, returning water and thin fine tailings to other sites within the Mildred Lake Project area. The crest elevation is 400 m or 390 m. An upgrade to increase the water storage to a maximum water surface level of 397 m was constructed in 2009 to 2010.The embankment length is 19.5 km. The maximum embankment height is at least 30 m and the average embankment height is about 18.5 m. The average embankment base width is about 800 m from Google Earth. So the total embankment volume is about 145×106 m3.
Aurora Settling Basin (ASB)
This is located to the South East of the Aurora North lease, adjacent to the Muskeg River.The embankment length is 11.6 km and the average embankment base width is about 260 m from Google Earth. The surface elevation is 341.4 m.
See also
- Syncrude Canada Ltd.SyncrudeSyncrude Canada Ltd. is the world's largest producer of synthetic crude oil from oil sands and the largest single source producer in Canada. It is located just outside Fort McMurray in the Athabasca Oil Sands, and has a nameplate capacity of of oil, equivalent to about 13% of Canada's consumption...
- Athabasca Oil SandsAthabasca Oil SandsThe Athabasca oil sands are large deposits of bitumen, or extremely heavy crude oil, located in northeastern Alberta, Canada - roughly centred on the boomtown of Fort McMurray...
- List of largest dams in the world