3-D Modeling to Support Interim and Postconstruction Groundwater Management Decisions for a Large Remediation Project
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Construction projects that have a need for hydraulic control during an excavation often require groundwater models to optimize aspects of the design and estimate future groundwater flow conditions during interim and post construction conditions.

The presence of impacted groundwater in the vicinity of an excavation can further complicate the dewatering process by requiring water treatment that can significantly increase the cost of the project. Although a 2-dimensional seepage analysis can provide adequate groundwater inflow estimates in idealized settings, three-dimensional groundwater models are preferable in complex hydrogeologic settings with nearby surface water bodies, variable stratigraphy and complex geometries.

As part of the Port Lands Flood Protection and Enabling Infrastructure Project (PLFPEI) in Toronto, Ontario, a series of three-dimensional models were developed to support construction of a new river channel through an approximately two square mile former industrial area connecting the mouth of the Don River to Lake Ontario. A preconstruction model simulating existing conditions was developed with Site-specific and regional hydrogeologic data and Don River and Lake Ontario stage elevations and calibrated using groundwater levels measured in wells throughout the Site. An Interim construction model was developed to simulate the impacts of vertical cutoff walls and horizontal drain systems during construction while a post construction model was developed to incorporate final design elements including a horizontal barrier to isolate impacted groundwater, new river valley finish materials, and final re-development elements such as parks, roads, and buildings. The PLFPEI illustrates how groundwater models were used to evaluate optimal hydraulic cutoff wall tip elevations, estimate groundwater inflow volumes for dewatering purposes, inform future long-term post-construction monitoring through the use of predict advective contaminant flow paths and travel times, and assess potential for groundwater mounding outside the cutoff wall system during periods of high lake levels.

Publication Summary

  • Geosyntec Authors: Dariusz Chlebica, Denise Tripp, Sharon Lau, David Adilman, Danielle Thorson
  • All Authors: Dariusz Chlebica, Denise Tripp, Sharon Lau, David Adilman, Danielle Thorson, Geosyntec Consultants; Laura Solano, Michael Van Valkenburgh Associates, Inc.; Meggen Janes, Waterfront Toronto
  • Title: 36th Annual International Conference on Soils, Sediments, Water, and Energy
  • Event or Publication: Event
  • Practice Areas: Groundwater Assessment and Remediation
  • Citation: Multiple Geosyntec practitioners will present at the virtual 36th Annual International Conference on Soils, Sediments, Water, and Energy on October 19-23, 2020.
  • Date: October 19-23, 2020
  • Location: Virtual
  • Publication Type: Platform Presentation