Dec 03, 2020

The importance of hydrogeology when building infrastructures

All too often, during construction projects or infrastructure development, we discover problems managing excessive quantities of water during the excavation phase. This type of issue occurs when the water table is shallow and when soils or bedrock are permeable.

These significant water volumes and flows are mostly unexpected and often left to the contractor to deal with. In addition to complicating daily construction site management, this can negatively affect schedules and budgets. In the end, work quality can suffer, for example, with inadequate installation of the waterproofing membrane under the foundation. In some cases, a dewatering system must be installed to permanently drawdown the water table.

This problematic situation can be easily be managed upstream by integrating a comprehensive and adequate hydrogeological component into the preliminary geotechnical and environmental studies. All too often, the hydrogeological component in these types of studies is neglected and consists only of a simple approximation of the water table depth.

Using hydrogeology

More specifically, the hydrogeological component is intended to determine basic geological and hydrogeological conditions, including:
- the geological description of existing soils and bedrock
- the depth of the water table
- the groundwater flow direction and hydraulic gradient
- the hydraulic conductivity or permeability of existing soils and bedrock
- the quality of groundwater that needs to be managed
To achieve this, the following activities are performed on site during the study:
- Drilling and installation of observation wells
- Piezometric level survey
- Hydraulic conductivity test
- Groundwater sampling
In the event soils and bedrock are highly permeable, a more exhaustive analysis, including pumping wells and pumping tests, may be required.

Acquiring this data and determining these basic hydrogeological parameters helps anticipate groundwater infiltration problems during the excavation phase.

More specifically, the following aspects are analyzed:
- Groundwater volume and flow determination based on the depths that need to be reached or the excavation phase to carry out
- Development of efficient drainage and excavation dewatering methods, such as:
- sump pump system at the bottom of the excavation
  
  - well points at the periphery
  
  - pumping wells
- Aids in deciding whether a waterproofing membrane should be installed under the foundation.
- Management of groundwater discharge based on its quality
- Detailed design of a permanent drainage/dewatering system after excavation and construction of the infrastructure, if applicable:
  
  - design and sizing of a drainage system under the infrastructure and periphery
  
  - design of a water table drawdown system using pumping wells
There are also tools to optimize dewatering methods and drainage system design, like numerical modelling of groundwater flow. These tools enable hydrogeologists to accurately determine anticipated water flows or optimize dewatering systems (number and spacing of pumping wells).

Concrete benefits

Performing the hydrogeological component provides multiple and very concrete benefits:
- Anticipation of potential problems
- Improved site work planning and increased synergy
- Reduced health and safety risks
- Improved selection and design of dewatering methods
- Sound risk management (on time and on budget)
Conclusion

Stay alert! Improve your preliminary construction project studies by adding an adequate and comprehensive hydrogeological component. If you invest effort and energy in defining the geotechnical and environmental conditions of the subsurface, why not take the opportunity to integrate hydrogeology? The benefits will help you at all project stages, from design to completion.

Contact us to learn more.

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Using hydrogeology

Concrete benefits

Conclusion