The Wyoming Department of Environmental Quality Abandoned Mine Lands Office was presented with an Abandoned Mine Lands Reclamation Award for the Western States from the Office of Surface Mining Reclamation and Enforcement (OSMRE) at the recent National Association of Abandoned Mine Lands Programs conference in Canaan Valley, WV.
Situated atop the Hanna No. 3 Mine, CR 297 serves as the secondary and emergency access roadway from US Hwy 287 to the communities of Hanna and Elmo. Dozens of historic subsidence events recorded in the Hanna No. 3 Mine impacted the useability of this important roadway to the point its use was restricted. The solution to bring CR 297 back into service was to inject over 28,000 cubic yards of void-fill grout into the mine workings below a 3,500-foot stretch of this important corridor during a 5-month period.
Brierley Associates was retained by the Wyoming AML office to perform a geological, geophysical, and geotechnical exploration program to identify the true limits of the mine workings, the depth of mine, determine the geologic stability of the area, identify potential geomechanical modes of failure, develop a risk profile to the overlying roadway, bridge, and railroad along CR 297, and recommend potential mitigation strategies with cost estimates.
Brierley created project specifications, plans, drawings, and cost estimates to mitigate the subsidence risk using a custom designed high mobility grout mixture to penetrate and stabilize the heavily rubblized underground workings. Brierley provided engineering and construction management services during the project and performed geologic logging of the 306 boreholes drilled during mitigation.
Learn more about this project here.