A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Templeton Gap Floodway Levees, Investigation, and Mitigation of Mine Subsidence
As part of FEMA's Digital Flood Insurance Rate Map (DFIRM) conversion project for El Paso County, Colorado, the Templeton Gap Levee (TGL) System required certification. The purpose of levee certification is to provide FEMA with documentation that areas behind the levees are protected from the 1% annual chance of exceedance flood event and may be accredited as such by FEMA on the DFIRM. Without certification, property owners behind the TGL could be required to purchase flood insurance, potentially costing the community millions of dollars annually in insurance premiums. During preliminary exploration and literature review, the engineering team found evidence of historic coal mining, predominantly room- and pillar-type mines with approximately 9 to 30 meters (30 to 100 feet) of cover over the coal seams under and around the TGL. Subsequent targeted drilling, geophysical surveys using DC resistivity and reverse vertical seismic profiling, and subsurface sonar and video void imaging confirmed that open mine voids existed under the levee, placing the structure at risk for future subsidence that could threaten the integrity of the TGL. The geophysical investigation: 1) provided detailed information on the subsurface characteristics beneath the TGL; 2) mapped possible mine workings beneath and adjacent to the levee; and 3) provided information for assessing risk for potential subsidence or sinkhole development associated with abandoned mines. Mitigation measures consisted of grouting the areas considered at high risk of subsidence, using staged sanded cement grout injection into open mine voids. The Colorado Division of Reclamation Mining and Safety finalized the mitigation plan and performed the work under the Inactive Mine Program. This paper describes the geotechnical and geophysical investigation and subsidence mitigation as well as the agency partnership that developed to facilitate completion of this work.
Templeton Gap Floodway Levees, Investigation, and Mitigation of Mine Subsidence
As part of FEMA's Digital Flood Insurance Rate Map (DFIRM) conversion project for El Paso County, Colorado, the Templeton Gap Levee (TGL) System required certification. The purpose of levee certification is to provide FEMA with documentation that areas behind the levees are protected from the 1% annual chance of exceedance flood event and may be accredited as such by FEMA on the DFIRM. Without certification, property owners behind the TGL could be required to purchase flood insurance, potentially costing the community millions of dollars annually in insurance premiums. During preliminary exploration and literature review, the engineering team found evidence of historic coal mining, predominantly room- and pillar-type mines with approximately 9 to 30 meters (30 to 100 feet) of cover over the coal seams under and around the TGL. Subsequent targeted drilling, geophysical surveys using DC resistivity and reverse vertical seismic profiling, and subsurface sonar and video void imaging confirmed that open mine voids existed under the levee, placing the structure at risk for future subsidence that could threaten the integrity of the TGL. The geophysical investigation: 1) provided detailed information on the subsurface characteristics beneath the TGL; 2) mapped possible mine workings beneath and adjacent to the levee; and 3) provided information for assessing risk for potential subsidence or sinkhole development associated with abandoned mines. Mitigation measures consisted of grouting the areas considered at high risk of subsidence, using staged sanded cement grout injection into open mine voids. The Colorado Division of Reclamation Mining and Safety finalized the mitigation plan and performed the work under the Inactive Mine Program. This paper describes the geotechnical and geophysical investigation and subsidence mitigation as well as the agency partnership that developed to facilitate completion of this work.
Templeton Gap Floodway Levees, Investigation, and Mitigation of Mine Subsidence
Soule, Nathan (author) / Parekh, Minal L. (author) / Kuehr, Steven (author) / Amundson, Al (author) / Hanna, Kanaan (author) / Bare, Dan (author) / Pauley, Chris (author)
Biennial Geotechical Seminar 2012 ; 2012 ; Denver, Colorado, United States
GeoChallenges ; 134-147
2012-11-09
Conference paper
Electronic Resource
English
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