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Central Region Publications

Gravity Study of the Guernsey Landfill Site, Guernsey, Wyoming

By Michael W. Webring, Robert P. Kucks, and Jared D. Abraham

Open-File Report 2004–1383

view of Guernsey, WY
Version 1.0
Published 2005

A gravity survey was conducted in and around an inactive landfill located immediately north of the town of Guernsey, Wyoming. The purpose was to determine the depth and orientation of the bedrock and to help establish hydrologic control of fluid movement through the site. The town of Guernsey and nearby Camp Guernsey are sited on the North Platte River alluvial plain with the landfill situated on an alluvial terrace immediately north of town. Both the town and Camp obtain water from relatively shallow wells drilled in the alluvial plain. Minor amounts of solvents have been identified in some monitoring wells around the landfill site.

The gravity data were collected using an electronic nulling gravimeter and a dual frequency differential GPS unit to measure altitude and position. The target error in the observed gravity is +/- 0.007 mGal and the altitude error less than 2 cm. Highly accurate terrain corrections were a key element in the data processing and allowed a direct density determination of the alluvial terrace soils and an accurate stripping of their effect from the gravity anomaly.

The composition of the terrace is unconsolidated cobbles and soil with a relatively low density, whereas the basement is interpreted to be high density metadolomite which outcrops several hundred meters east of the landfill in a quarry. The gravity signature is a strong 1 mGal in amplitude between two east-west oriented linear features, the gravity low is to the north of the landfill cells and the gravity high is to the south-east of the cells. Approximately 30 meters of basement relief will account for the gravity anomaly.


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Gravity data.

Surveyed topography.

Coordinate metadata for topographic data.

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