Engineering against the elements: protecting foundations from groundwater
Protecting foundations from groundwater starts before excavation. Site investigation, temporary dewatering, excavation support, drainage and waterproofing form one coordinated system shaped by the ground conditions and the structural design.
An engineering discussion with the STMK team explains why a dry winter survey does not rule out water in summer, when wellpoints are used and why maintenance must be designed into the underground structure. Nine short, silent video diagrams accompany the article. The original on-screen diagram labels are in Russian; the equivalent explanations are provided here in English.
Seasonality: why one survey is not the whole picture
A site investigation records conditions at the time of the survey. Where groundwater levels vary seasonally, a dry winter observation does not necessarily describe the conditions that will occur during excavation.
The STMK discussion describes a project where water was approximately 1.5 metres higher than expected when the team began excavating closer to summer. Routine construction drainage was insufficient, and three wellpoint installations were used for the construction stage.
Designers need site-specific information on hydrogeological conditions and possible changes. Any additional investigation and monitoring should respond to the risks of that site; there is no universally dry month for every location.
The cost of decisions postponed until excavation
A difficult site is a distinct engineering problem. Groundwater protection, the sequence of works and associated costs should be addressed while designing the underground structure, rather than after water appears in the excavation.
The budget and programme need to account for enabling works, equipment, pumping, observations and subsequent operation. Decisions deferred until a foundation or a finished basement is in place may require substantial rework and additional expenditure.
How wellpoint systems work
Wellpoints are vertical filter tubes connected to a pumping installation. They can lower groundwater during construction where the ground conditions and the designed system make this approach appropriate.
The aim is to establish the specified conditions for preparing the formation and building the underground structure. The number and depth of wellpoints, pumping regime and effects on neighbouring structures require site-specific design. Temporary wellpoints do not replace the completed building’s permanent waterproofing.
Why dewatering takes time
The 7–10 day period in the STMK discussion refers to waiting for a noticeable reduction in water level after starting the system. It is an example used for planning particular works, not a standard duration for every site.
The actual response depends on inflow, ground permeability, excavation dimensions and the selected system. Readiness for the next stage is confirmed through observations and the required project controls, rather than simply counting days.
Deep excavations: water, ground and support
Deep basements and parking levels require the team to retain the ground, control water and monitor the supporting structures together. The source discussion considers excavations 7–10 metres deep.
Water-saturated sandy soils deserve particular attention: seepage and loss of particles can alter the behaviour of the ground and excavation support. Support stiffness, dewatering and monitoring must be designed for the specific excavation. Observations need to reach the team responsible for design decisions.
Where the water goes: drainage and pumping
Collecting water is only part of the task. Under-slab drainage, perimeter drainage, a collection chamber and pumping equipment need to operate as one coordinated arrangement. The discharge point and any connection to a stormwater network must be checked for the particular project.
The STMK discussion describes a pumping station below foundation level. Its indicative factory lead time was around two months, and installation could require a separate wellpoint circuit. These are examples from that construction scenario; actual arrangements and lead times are confirmed during design and procurement.
How groundwater changes the structural design
Saturated ground and water pressure influence the formation, foundations and underground structure. Groundwater protection therefore cannot be designed independently of the building’s structural system.
Depending on conditions, formation preparation, replacement of weak soils, drainage and waterproofing details may need revision. The examples discussed included granular preparation and treatment of wet soils. Actual thicknesses and quantities come from the project design, not a generic diagram in an article.
Designing waterproofing for maintenance
Waterproofing maintenance should be considered before walls, backfill and finishes restrict access. The STMK discussion describes a PVC membrane divided into compartments, with provisions for local injection.
The intention is to introduce injection material into the affected zone if a local leak occurs and the designed system permits it. Maintainability depends on detailing and installation across the complete system; a PVC label alone does not guarantee performance.
Membrane, bituminous and other solutions should be compared against site conditions and project requirements. The relevant comparison is between coordinated systems, the quality of their details and repair access, rather than an absolute protection claim for one material.
What to coordinate before work starts
Ground and groundwater information, dewatering, excavation support, water discharge, waterproofing details, monitoring and maintenance. Coordinating these decisions early reduces uncertainty on site.