23 DECEMBER 2024 WorldWide Drilling Resource® Safety Concerns When Building in Yellowstone National Park Adapted from Information by the United States Geological Survey The Yellowstone River Bridge in Wyoming, was constructed in the early 1960s and has structural problems that require it to be replaced; it will be removed once the new Yellowstone River Bridge is completed. This project will also reroute part of the Northeast entrance road to the intersection of Grand Loop road. Safety was a concern when constructing this new 1285-foot-long and 175-foot-high steel girder bridge which is located within a hydrothermally active zone with multiple gas vents along the river’s edge. Because of its proximity to thermal activity, the large-drilled shafts which are 5-10 feet in diameter and 40-60 feet in depth required sulfate-resistant cement and thermal monitoring of belowgrade concrete curing to assure a stable bridge structure. To determine if modern-day drilling was impinging on the adjacent local hydrothermal system, geologists from the University of Wyoming measured and recorded temperature and pH variations in groundwater, the dirt and rock removed from the drill holes, and changes in groundwater electrical conductivity at specified time and depth intervals. A particular concern related to drilling was hydrogen sulfide gas (H2S), a toxic gas often associated with Yellowstone’s hydrothermal systems which has a faint rotten egg smell. At higher concentrations, H2S is odorless and extremely dangerous. Prolonged exposure can cause nausea, headaches, fatigue, dizziness, as well as eye and respiratory tract irritation and death if exposure is not reduced within 30-60 minutes. Geologists also monitored gas concentrations to help ensure a safe work environment. This monitoring involved equipping each worker with a personal H2S gas sensor to continuously monitor H2S levels around the drill site. In the event of an accidental and hazardous gas exposure, an oxygen supply and full protective gear were on-site to ensure a fast and effective response. A trigger action response plan was implemented to address any geologic hazards or risks to the workers. The plan gave three levels of response for various conditions that might be encountered during drilling operations of the bridge footings. Daily activities were documented with detailed reports of the drilling activities and a final drilling log for each of the 20 drilled shafts as part of the project. The drilling phase of the bridge project was completed without incident. Construction aboveground is ongoing, and scheduled to be completed in the fall of 2026. Photo courtesy of Ken Sims with the University of Wyoming. CONST The current bridge. Photo courtesy of Jacob Frank. A small, yellow, personal 4-gas safety monitor can be seen on the upper left breast pocket on the person in the far right of the picture. Photo courtesy of Ken Sims. Booth 502
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