Date of Award:

8-2020

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Paul Grossl

Committee

Paul Grossl

Committee

Grant Cardon

Committee

Colleen Jones

Committee

Seth Lyman

Abstract

Oil and gas well pad reclamation in arid environments such as in the Uinta Basin of Utah, presents unique challenges, including remote locations, limited water, and elevated soil salinity and sodicity. Successfully reclaimed Plugged and Abandoned (P&A) well pads should resemble the surrounding rangeland once fully reclaimed. Revegetation of native species is the primary indicator of successful reclamation, but the lack of water makes it challenging to re-seed native plants, while trying to prevent the encroachment of invasive plant species such as Bromus tectorum (cheatgrass), Salsola tragus (Russian thistle), and Halogeton glomeratus (halogeton). Could successful reclamation be reflective of good soil health? Our objective was to determine if land disturbance negatively impacted soil health and consequently successful revegetation, by performing a soil health assessment on P&A well pads (disturbed soils) and comparing that to the soil health of the surrounding, adjacent rangeland (undisturbed soil). By using undisturbed rangeland soil as the desired reclamation goal for the P&A well pad, certain soil health indicators were chosen for comparison between the two sites.

Overall, P&A well pads had reduced soil health compared to the undisturbed rangeland. There was a difference in soil texture, with the undisturbed rangeland having a coarser soil texture (sandy loam) and the P&A well pads having a finer soil texture (clay loam, sandy clay loam). Compared to the rangeland, the P&A well pads had higher sodicity levels, measured by sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP), making the P&A well pads more susceptible to sodic crust formation and reducing aggregate stability. Electromagnetic induction sensing (EMI) was also used, to see if it could quickly identify soil health indicators (ECe, SAR, pH, texture, etc.) to aid land managers in a more direct, targeted reclamation strategy. Many different soil properties can impact EMI reading, so while useful, EMI cannot always be relied on for the desired soil health indicators for reclamation.

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