One Seam at a Time: Interactive Quality Assurance to Identify Coal Seams during Foundation Construction-Paper

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The Aeolus–Jim Bridger Transmission Line Project in southern Wyoming involved 551 structures across a 138-mile alignment, in an area where coal seams and other variable ground conditions posed risks to foundation performance and construction. Environmental access restrictions, a fixed schedule, and the need to finish before winter made a full pre-construction geotechnical investigation impractical.<br /><br />The project used an Engineer-Procure-Construct (EPC) contract and a proactive quality assurance (QA) program to manage uncertainty. Initial designs drew on 118 borings, geological mapping, historical mine records, and risk assessments. Designs allowed for field adjustments, while the team prioritized supplemental investigations at sites likely to be affected by coal or other problematic ground.<br /><br />During construction, professional geologists monitored excavation behavior and communicated changing conditions to engineers in real time. Rather than relying primarily on drill cuttings, QA focused on excavation stability, sidewall sloughing, swelling, and equipment performance. Engineers often issued revised instructions within hours, helping limit delays.<br /><br />The program identified mismatched soil profiles, unexpected or larger-than-anticipated coal seams, and groundwater. At one site, shafts were extended below coal seams; at another, loose silty sands and then strong quartzite prompted successive redesigns using available tools and materials. The line’s foundations were completed in December 2019, before major snowfall.<br /><br />The case demonstrates how integrated design, construction, and QA can enable work to proceed despite incomplete geotechnical data. Early risk planning, targeted investigation, and rapid communication helped manage subsurface hazards and support on-time completion.

Keywords

Aeolus-Jim Bridger Transmission Line

southern Wyoming

geotechnical investigation

foundation performance

coal seams

Engineer-Procure-Construct

quality assurance

subsurface hazards

ground conditions

construction monitoring