Sump pump
A sump is an area or space where liquids are allowed or encouraged to accumulate. Sump pumping is the process of evacuating that liquid using pumps.
In ground engineering works – such as foundations, deep basements, trenches, tunnels and other excavations – groundwater is very often present. This must be dealt with so that work on the site is not difficult, dangerous or even impossible. Modern geotechnical techniques allow groundwater to be safely managed by a process of dewatering.
Without suitable control measures, inflows of groundwater can flood excavations or tunnels, and can also lead to instability when the soils or rock around the excavation weaken and collapse – either locally or on a large scale. The objective of dewatering is to lower groundwater levels to below working level in the excavation. Examples of this group of techniques include sump pumping, well points, deep wells and ejector wells.
Sump pumping is one of the simplest dewatering techniques: groundwater seeps into the excavation and is allowed to collect in sumps – which can either be the lowest point of the excavation or may be an area specially created into which water may seep naturally e.g a well or sump. Each sump will typically have one or more robust electric-powered pumps with the capacity to handle the solids that will inevitably be present. The collected liquid is then pumped away for disposal, either with pumps running continuously or activated automatically as the water level rises.
Sump pumping can be a very effective and economic method to modestly reduce the liquid (‘drawdown’) in a sump, especially in favourable ground conditions such as well-graded course soils (e.g sandy/coarse gravels and gravelly sands).
In unfavourable ground conditions, such as in silts, fine sands and other fine-grained soils, sump pumping may lead to instability as it may draw out fine particles from the soil, potentially causing ground movement such as settlement. Furthermore, depending on the soil type, sump pumping may see high levels of sediment in the pumped water which could have an adverse environmental effect at the point of disposal.
Over the past few decades, there have been several high-profile projects around the world that have been seriously delayed by groundwater problems. However, a greater number have successfully dealt with groundwater.
In the south of England, projects such as High Speed 1 (known as the Channel Tunnel Rail Link during its construction in the early 2000s) and Crossrail have routes which successfully passed through multiple water-bearing strata, including crossing beneath the River Thames. Both projects involved successful dewatering and the use of sump pumps.
[edit] Related articles on Designing Buildings
Featured articles and news
ECA 2024 Apprentice of the Year Award
Entries open for submission until May 31.
UK gov apprenticeship funding from April 2024
Brief summary the policy paper updated in March.
For the World Autism Awareness Month of April.
70+ experts appointed to public sector fire safety framework
The Fire Safety (FS2) Framework from LHC Procurement.
Project and programme management codes of practice
CIOB publications for built environment professionals.
The ECA Industry Awards 2024 now open !
Recognising the best in the electrotechnical industry.
Sustainable development concepts decade by decade.
The regenerative structural engineer
A call for design that will repair the natural world.
Buildings that mimic the restorative aspects found in nature.
CIAT publishes Principal Designer Competency Framework
For those considering applying for registration as a PD.
BSRIA Building Reg's guidance: The second staircase
An overview focusing on aspects which most affect the building services industry.
Design codes and pattern books
Harmonious proportions and golden sections.
Introducing or next Guest Editor Arun Baybars
Practising architect and design panel review member.
Quick summary by size, shape, test, material, use or bonding..