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Low-flying Helicopter Survey to Map Subsurface Geology and Groundwater Near Silverton, Colorado

March 25, 2019

In the public interest, and in accordance with FAA regulations, the USGS is announcing this low-level airborne project. Your assistance in informing the local communities is appreciated.

What:          A low-flying helicopter under contract to the U.S. Geological Survey will image subsurface geophysical variations of                                  sediments and rocks for scientific research purposes in the Silverton, Colorado area. The USGS is working in                                           cooperation with the U.S. Forest Service, Colorado Department of Public Health and Environment, and U.S.                                               Environmental Protection Agency.

Where:        Silverton, Colorado, with focused efforts in the designated Bonita Peak Mining District Superfund area.

When:         Starting on or about April 1, 2019, and lasting for about two weeks.

Airborne electromagnetic system similar to that which will be used for the Silverton, Colorado survey.
Airborne electromagnetic system similar to that which will be used for the Silverton, Colorado survey.​​​​​​​Photo credit: Geotech,

Citizens can expect to see a low-flying helicopter towing a large wire loop hanging from a cable in the Bonita Peak Mining District Superfund area near Silverton during the survey.

The electromagnetic system resembles a large hula-hoop towed beneath the helicopter to measure tiny voltages that can be used to map the earth’s subsurface. The USGS will analyze these data to characterize subsurface variations of sediment and rock properties.

A helicopter-borne geophysical system will collect measurements in the Bonita Peak Mining District, with focused efforts in the Mineral Creek basin, the upper Cement Creek basin, and the Eureka, Placer, California and Arrastra gulches.  These surveys involve flying low to the ground upon a specific planned path to measure the electrical properties of the earth’s subsurface. Data collected during this survey will assist USGS scientists in mapping groundwater flow paths of varying water quality, faults that may be permeable for groundwater flow and different types of subsurface sediments and bedrock. Some of the bedrock areas are associated with altered and mineralized zones that have been mined historically for base metals such as copper, lead and zinc, and precious metals such as silver and gold. The airborne geophysical survey data and models of the subsurface will be released to the public following completion of the survey. The surveys will be conducted by Geotech, a specialty airborne geophysical company. Experienced pilots who are specially trained for low-level flying required for geophysical surveys will be piloting the helicopter. The company works with the Federal Aviation Administration to ensure flights are in accordance with U.S. regulations. 

More information about this project can be found online

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