Multi-faceted approach for CCR pond dewatering and depressurization – A Case Study.pdf

Cleveland Tarp, Haley & Aldrich Inc.
Christopher Jones, Haley & Aldrich Inc.
Shawn Coughlin, Keller
Tom Holden, Haley & Aldrich, Inc.

Description

Multi-faceted approach for CCR Pond dewatering and depressurization-A Case Study Authors Mr. Cleveland Tarp - United States - Haley & Aldrich Inc. Mr. Christopher Jones - United States - Haley & Aldrich Inc. Mr. Shawn Coughlin - United States - Keller Mr. Tom Holden - United States - Haley & Aldrich, Inc. Abstract CCR Pond closure by removal can present a wide range of challenges, with CCR dewatering and depressurization sometimes being the greatest. CCR ponds built over pre-existing stream beds and located in close proximity to water bodies can be particularly difficult to dewater and present stability and safety hazards. Due to the hydrogeologic conditions at this particular project site, a multi-faceted approach was needed to facilitate not only CCR dewatering but also depressurization of underlying materials. Previous construction work experienced significant and sustained groundwater inflows from beneath the ponded ash. In this case study, the system currently in progress, is comprised of shallow vacuum well-points, deeper gravity wells, surface dewatering features (ditches, sumps, etc.) and a perimeter of a groundwater cut-off (TRD) wall and surface liners to reduce infiltration. Dewatering system performance is monitored using a system of near real-time vibrating wire piezometers and field observations. The construction sequencing, dewatering system, and instrumentation system have been developed to proceed in concert with excavation activities at the site. An automated dewatering status reporting system was also developed to help inform the construction teams on progress and to support planning construction activities. This presentation will discuss the state of the current active dewatering system, our basis for design and original groundwater flow model. We will compare the original groundwater flow model results coupled with observed conditions to show how the data are used to help the project team excavate the ash efficiently and safely.

 
May 16th, 8:00 AM May 16th, 8:30 AM

Multi-faceted approach for CCR pond dewatering and depressurization – A Case Study.pdf

Grand Rapids, Michigan

Multi-faceted approach for CCR Pond dewatering and depressurization-A Case Study Authors Mr. Cleveland Tarp - United States - Haley & Aldrich Inc. Mr. Christopher Jones - United States - Haley & Aldrich Inc. Mr. Shawn Coughlin - United States - Keller Mr. Tom Holden - United States - Haley & Aldrich, Inc. Abstract CCR Pond closure by removal can present a wide range of challenges, with CCR dewatering and depressurization sometimes being the greatest. CCR ponds built over pre-existing stream beds and located in close proximity to water bodies can be particularly difficult to dewater and present stability and safety hazards. Due to the hydrogeologic conditions at this particular project site, a multi-faceted approach was needed to facilitate not only CCR dewatering but also depressurization of underlying materials. Previous construction work experienced significant and sustained groundwater inflows from beneath the ponded ash. In this case study, the system currently in progress, is comprised of shallow vacuum well-points, deeper gravity wells, surface dewatering features (ditches, sumps, etc.) and a perimeter of a groundwater cut-off (TRD) wall and surface liners to reduce infiltration. Dewatering system performance is monitored using a system of near real-time vibrating wire piezometers and field observations. The construction sequencing, dewatering system, and instrumentation system have been developed to proceed in concert with excavation activities at the site. An automated dewatering status reporting system was also developed to help inform the construction teams on progress and to support planning construction activities. This presentation will discuss the state of the current active dewatering system, our basis for design and original groundwater flow model. We will compare the original groundwater flow model results coupled with observed conditions to show how the data are used to help the project team excavate the ash efficiently and safely.