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Fieldwork

Mapping the Stamp Sands of Lake Superior



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In September 2018, the USGS Woods Hole Coastal and Marine Science Center (WHCMSC) conducted high-resolution geophysical mapping to determine the distribution and thickness of historical mine tailings on the floor of Lake Superior. Large amounts of waste material, called “stamp sands,” from copper mining were dumped into the lake at many locations in the early 20th century, with wide-reaching consequences that have continued into the present day. Mapping was focused offshore of the town of Gay on the Keweenaw Peninsula of Michigan where ongoing erosion and re-deposition of the toxic stamp sands has buried miles of native, white-sand beaches. The stamp sands are also steadily encroaching on Buffalo Reef, a large area of cobble/boulder substrate that supports productive fisheries in the lake. The objectives of this cooperative mapping project are to develop a framework for scientific research and provide baseline information required for management of resources within the coastal zone of northern Michigan.

Photograph of the entrance to Grand Traverse Bay Harbor showing the dark-colored stamp sands
Above: Photograph of the entrance to Grand Traverse Bay Harbor, located 8 kilometers downdrift of the spoils pile. Migration of the dark-colored stamp sands (moving from left to right) has buried the original beach, overtopped the wall, and partially blocked the channel. The high sedimentation rate requires frequent dredging to maintain navigation, which for the 2018 survey was restricted to the narrow passage along the far wall. Note the nearly complete absence of vegetation on the sandy deposits. [larger version]

This project is jointly funded by the WHCMSC, USGS Midwest Region, and the Detroit District of the US Army Corps of Engineers (USACE). Modeling studies by the USACE previously concluded that the reef area buried by stamp sands will more than double from 25 percent to 60 percent over the next 10 years if no action is taken (Hayter et al., 2015). Several mitigation options are being examined, including

  • construct a stone revetment around the spoils pile,
  • remove the spoils pile and dump in deep water,
  • excavate an underwater trough to intercept the sands before they reach the reef.

To test potential outcomes under these (and other) scenarios, accurate data on the current distribution of stamp sands and the processes/pathways of sediment transport in the area were needed. Cooperating institutions include Michigan Technical University (MTU) in Houghton, MI, where researchers have conducted research on the environmental legacy of copper mining in the region for many years.

Satellite location map with labels overlain
Above: Air photograph showing the extent of the stamp sands in a narrow band along the coast of northern Michigan. White arrows indicate net transport direction of stamp sands from the spoils pile (upper right) to the mouth of Grand Traverse Bay Harbor (lower left). Inset map shows the location of the survey area. Visit Google Earth Engine to view an animation of how this stretch of coast has changed in recent years. [larger version]

The journey between Woods Hole to northern Michigan is long. Barry Irwin, Alex Nichols and David Foster hauled the R/V Rafael, the Center’s well-equipped 25’ mapping vessel over 1200 miles each way to conduct the survey. The crew, including Walter Barnhardt and Brian Andrews, collected approximately 370 kilometers of geophysical tracklines and collected sediment samples at 17 stations over the course of the two-week survey. Bathymetry and backscatter data from a multibeam echosounder and subbottom data from boomer and chirp seismic-reflection profilers were used to map the geologic framework of approximately 30 square kilometers of the lake in depths of 4–35 meters. These data will be compiled with existing lidar, video, and sample data from MTU to produce geologic maps of the area, with particular focus on the stamp sands. The dense array of subbottom data will guide the selection of cores to be collected by Rachel Malburg (ACOE) in 2019.

Photograph of the R/V Rafael alongside dock near the survey site on Lake Superior
Above: Photograph of the R/V Rafael alongside dock near the survey site on Lake Superior. [larger version]

Although unsalted and shark free, Lake Superior certainly lived up to its reputation as a rugged body of water. For several days, an easterly gale blew, waves built to 10 feet, and the lake waters turned brown with sediment derived from the spoils pile. The stamp sands—dark gray in color with metal-rich geochemical signatures—are readily distinguishable from the region’s native quartz sands and thereby represent an excellent tracer for tracking sediment movement across the submerged landscape. The well-constrained history of emplacement and subsequent erosion of the stamp sands offers a unique opportunity to validate models of sediment supply on coastal evolution since mining ceased in the 1930s. Of the approximately 22.7 million metric tons (37.3 million cubic yards) deposited at the Gay site MTU investigators (Kerfoot et al., 2012) have estimated that more than 85 percent of the original pile of stamp sand has been eroded. Movement of that sediment has caused progradation of the beach and damming of stream outlets downdrift of the pile. In the offshore, USGS mapping will characterize the extent of sedimentation on the sensitive hard-bottom habitats, and help quantify the spreading environmental effects from copper and other metals that threaten critical fish breeding grounds.

Photograph showing a high scarp cut into the large pile of stamp sands
Above: Photograph showing a high scarp cut into the large pile of stamp sands at the town of Gay, Michigan. Nearly a century of erosion by waves and currents has transported millions of cubic yards of mine tailings along the coast and spread them across the adjacent lake floor. [larger version]

References:

Hayter, E., Chapman, R., Lin, L., Luong, P., Mausolf, G.,  Perkey, D., Mark, D., and Gailani., J., 2015, Modeling sediment transport in Grand Traverse Bay, Michigan to determine effectiveness of proposed revetment at reducing transport of stamp sands onto Buffalo Reef: US Army Corps of Engineers, ERDC Letter Report, 71 p.

Kerfoot, W.C., Yousef, F., Green, S.A., Regis, R., Shuchman, R., Brooks, C.N., Sayers, M., Sabol, B., and Graves, M., 2012, LiDAR (Light Detection and Ranging) and multispectral studies of disturbed Lake Superior coastal environments:  Limnology and Oceanography, v. 57, p. 749–771, https://doi.org/10.4319/lo.2012.57.3.0749.

Related Sound Waves Stories
Mapping Sediment Distribution and Thickness in Lake Mohave
June 2002
Lake Mead Mapping Completed
June 2001

Related Websites
Timelapse of coastal change in northern Michigan
Google Earth Engine
LiDAR and multispectral studies of disturbed Lake Superior coastal environments
Limnology and Oceanography
Woods Hole Coastal and Marine Science Center
USGS WHCMSC
Stamp Sands
Michigan Technological University
Environmental Impacts of Mining in the Keweenaw
NPS
Legacy Mine Waste Threatening Lake Superior's Buffalo Reef
Wisconsin Public Radio
A slow-moving ‘disaster’ is threatening Lake Superior and way of life
Bridge News

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in this issue:

Cover Story Understanding Erosion on Alaska’s Arctic Coast

News Brief
News Briefs

Research
Added Funding Aids Recovery from 2017 Hurricanes and Wildfires

Field Work
Mapping the Stamp Sands of Lake Superior

Recent Fieldwork

Outreach
Enhancing Science Education and Literacy Partnerships in Cape Cod

Staff amd Center News
Coastal Engineering Contractor Assists Flood Modeling in the Northwest

Publications
Dec. 2018 - Jan. 2019 Publications

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