Potential Failure Mode Analysis for Groundwater Collection Trench Between a CCR Landfill Dike and a River

John Seymour, Geosyntec Consultants, Inc.
Onur Tastan, Geosyntec Consultants, Inc.
Paul Sabatini, Geosyntec Consultants, Inc.
Victor Modeer, Vistra

Description

Potential Failure Mode Analysis for Groundwater Collection Trench Between a CCR Landfill Berm and a River Authors Mr. John Seymour - United States - Geosyntec Consultants, Inc. Dr. Onur Tastan - United States - Geosyntec Consultants, Inc. Dr. Paul Sabatini - United States - Geosyntec Consultants, Inc. Mr. Victor Modeer - United States - Vistra Mr. Isaiah Vaught - United States - Geosyntec Consultants, Inc. Abstract A potential failure mode analysis (PFMA) was conducted to assess the risks of failure for the construction of a groundwater collection trench located between the containment berm of a CCR landfill and a river. The trench is to be 20-ft deep and over 1,000 ft long. A one-pass trenching method was proposed. The PFMA process is typically used under dam safety programs. The PFMA was adopted for this condition due to the high risk of failure of the trench by collapse that could affect the containment berm. Risks included containment dike failure, human safety, and loss of CCR into the river. Five PFMs were identified during the PFMA workshop. Subsequently, potential risk reduction measures were developed and implemented into the design. The risk assessment included completing a seepage analysis at the base of the trench, conducting a FLAC analysis to assess the impacts of stress relief on the trench excavation, and conducting slope stability analyses of the trench and containment berm and riverbank. The risk reduction was incorporated into the construction technique by including contractor responsibilities for sequencing, limiting the timing of construction to dry/low river flow seasons, construction inspections and monitoring, requirements to avoid having an open trench for an excessive time, and to place backfill quickly.

 
May 14th, 10:30 AM May 14th, 11:00 AM

Potential Failure Mode Analysis for Groundwater Collection Trench Between a CCR Landfill Dike and a River

Grand Rapids, Michigan

Potential Failure Mode Analysis for Groundwater Collection Trench Between a CCR Landfill Berm and a River Authors Mr. John Seymour - United States - Geosyntec Consultants, Inc. Dr. Onur Tastan - United States - Geosyntec Consultants, Inc. Dr. Paul Sabatini - United States - Geosyntec Consultants, Inc. Mr. Victor Modeer - United States - Vistra Mr. Isaiah Vaught - United States - Geosyntec Consultants, Inc. Abstract A potential failure mode analysis (PFMA) was conducted to assess the risks of failure for the construction of a groundwater collection trench located between the containment berm of a CCR landfill and a river. The trench is to be 20-ft deep and over 1,000 ft long. A one-pass trenching method was proposed. The PFMA process is typically used under dam safety programs. The PFMA was adopted for this condition due to the high risk of failure of the trench by collapse that could affect the containment berm. Risks included containment dike failure, human safety, and loss of CCR into the river. Five PFMs were identified during the PFMA workshop. Subsequently, potential risk reduction measures were developed and implemented into the design. The risk assessment included completing a seepage analysis at the base of the trench, conducting a FLAC analysis to assess the impacts of stress relief on the trench excavation, and conducting slope stability analyses of the trench and containment berm and riverbank. The risk reduction was incorporated into the construction technique by including contractor responsibilities for sequencing, limiting the timing of construction to dry/low river flow seasons, construction inspections and monitoring, requirements to avoid having an open trench for an excessive time, and to place backfill quickly.