Bingham Canyon Mine Experiment

A 3-year research grant, funded by Kennecott Utah Copper (KUC), is examining wintertime temperature inversions in KUC's Bingham Canyon mine, and their relationship to the persistent multi-day wintertime inversions that form in the Salt Lake Valley. The project was initiated to augment the National Science Foundation-supported Persistent Cold-Air Pool Study (PCAPS) that was planned for the Salt Lake Valley in the winter of 2010-2011. Analyses of both the KUC and NSF-funded datasets are continuing following the 1 December 2010 through 7 February 2011 PCAPS field experiments. The KUC project has supported student research at the University of Utah and is intended to improve understanding of valley and basin temperature inversions.

The Bingham Canyon mine is on the east side of Utah's Oquirrh mountains in the Salt Lake Valley about 25 km southwest of Salt Lake City. The mine is thought to be the world's largest manmade excavation. The shaded topography map below shows the mine in relation to Salt Lake City and its surroundings, followed by two photos of the mine.

Figure 2: Topography of the Salt Lake Valley, with the Bingham Canyon Mine indicated.	Figure 3: Long-range photo of the 3000 m diameter Bingham Canyon Mine showing the elevations of the major topographical features. Base figure © Kennecott Utah Copper. Used with permission.

In the winter of 2010-2011, meteorological data were collected in and around the mine to supplement the meteorological data collected in the Salt Lake Valley during the PCAPS program. The data consisted of:

1) A line of surface-based temperature dataloggers on the west sidewall of the Salt Lake Valley running westward up the Oquirrh Mountains from the Jordan River at Riverton to the east edge of the Bingham Canyon Mine and down onto the floor of the mine. The purpose of this line was to determine concurrently the characteristics of temperature inversions within the mine and within the Salt Lake Valley at it's southern end. This line of data loggers supplemented two other lines that were part of the PCAPS program -- one line ran up the west ridge of Grandeur Peak on the east side of the valley. Another ran up Harker's Ridge towards Nelson Peak on the west sidewall of the valley in the Oquirrh Mountains. The lines were used to determine, at 5-min intervals through the whole winter, the characteristics of wintertime temperature inversions. The lines were used as a proxy for free-air temperature soundings, and could be compared to free-air temperature soundings made twice-daily from the Salt Lake International Airport at the north end of the valley.

2) An automatic weather station was placed at Bingham Pass, the lowest elevation opening of the mine. This standard weather station measured temperature, humidity, pressure, wind speed and wind direction. This weather station supplemented a network of KUC weather stations that are located around the mine. Placing the weather station at the low pass aimed to increase understanding of the exchange of air between the Bingham Canyon mine basin and the Salt Lake Valley.

3) A scanning Doppler LiDAR was placed near the floor of the mine. This laser-based device measures the light that is backscattered by atmospheric aerosols and determines the particle speed through the Doppler shift of the laser light's frequency. Besides the backscatter information, which ios a function of aerosol abundance and particle size, Doppler-dwerived line-of-sight speed information from several beams can be combined mathematically to determine vertical wind speed and direction profiles. This instrument was placed in the mine to observe the influence of strong winds above the mine on inversions that form in the mine. Data from the instrument can also be used to detect waves that are generated at the top of the inversions by strong wind shears.

The meteorological instruments used in this research are shown in the following photos. A map of the measurement locations is also shown. The LiDAR, unfortunately, was delivered too late in the inversion season for us to get the data we wanted, so we returned to the mine for more data in the 2011-2012 winter season.

Figure 4: Photos of the UU Automatic Weather Station at the Bingham Canyon Pass (left, Joe Young photo), of a "Hobo" temperature data logger (center), and of the scanning Doppler wind LiDAR near the bottom of the Bingham Canyon Mine (right, Sebastian Hoch photo).

Figure 5: Map of equipment locations for the 2010-2011 Bingham Mine Experiment. Shown are the locations of the temperature dataloggers (red dots), the LiDAR (blue triangle), and the KUC (black squares) and University of Utah (green square) automatic weather stations. The Oquirrh ridge line is indicated by a dashed line..	Figure 6:  Same as previous figure, but for the 2011-2012 Bingham Mine Experiment.

The instrumentation listed above was set up in the mine again for the 2011-2012 season. This winter season, however, was mild and cloudy and had only a few strong inversions. We planned to take some tethersonde and/or radiosonde (i.e., free-air) temperature soundings from the mine floor during this winter. Safety considerations in the mine, however, precluded this, although we were able to launch several soundings outside the mine from the Butterfield Canyon area southeast of the mine. These soundings were collected to compare free-air temperature soundings with surface based pseudo-vertical soundings from the nearby temperature datalogger line outside the mine.

We are planning to purchase a laser ceilometer this winter with our research funds to make measurements of the aerosol layer depth in the Salt Lake Valley. The utility of this instrument was demonstrated by student Joe Young, whose has conducted research as part of his MS thesis with data collected by an identical instrument provided by the National Center for Atmospheric Research during the winter 2010-2011 PCAPS experiment. An example of data collected with NCAR's ceilometer is shown in the following figure (Fig. 7). We hope to be able to display the data from this instrument on a website in real time so that the depth of the aerosol layer in the Salt Lake Valley can be tracked this winter. We hope to have the instrument working by late in the winter. It will supplement data from two obsolete ceilometers that were donated to us by the National Weather Service. Watch this website to see our progress.

Figure 7: Example of data and analyses from the NCAR-provided laser ceilometer used in the Salt Lake Valley during the 2010-2011 PCAPS experiment.

Temperature profiles during a shallow cold-air pool at 2300 MST on 7-8 January 2011. Shown are pseudo-vertical temperature profiles from the Grandeur line (east side of thr Salt Lake Valley), the Kennecott Outer Line (on the west sidewall just outside the Bingham Canyon Mine), and the Kennecott Inner Line (inside the mine). At this time, temperatures are warmer inside the mine than at the same height in the Salt Lake Valley outside the mine.

	Mixout of aerosols from the mine during a high wind episode on 13-14 February 2011, as observed with a scanning Doppler LiDAR in the mine. Aerosol backscatter values in the upper figure show that high aerosol loading inside the mine decreased suddenly at around 1100 MST as strong winds (lower figure) descended into the mine from aloft.
	The mixout event from the Bingham Mine in the previous figure was accompanied by an increase in aerosols on the floor of the valley, as observed by a laser ceilometer and seen in this figure. This dust originated at the valley floor and is apparently fugitive dust entrained by the strong winds that had occurred earlier at the mine's higher elevation.

Atmospheric gravity waves were produced on the top of the inversion above the mine on 2000-2100 UTC (1300-1400 MST) 5 January 2012 by an increase in westerly wind speeds above the mine. The gravity waves are thought to have been produced by a flow over the Oquirrh Mountain ridge line west of the mine.

Solar radiation and shadows cast into the mine from surrounding topography

• Hoch, S. W., C. D. Whiteman and J. S. Young, 2012: Doppler wind LiDAR observations and temperature structure evolution in a deep open-pit copper mine. 15th AMS Conference on Mountain Meteorology, Steamboat Springs, CO, 20-24 August 2012.