Wellpoints

A wellpoint is a type of small-diameter well used for dewatering purposes. It typically consists of a perforated pipe or screen driven into the ground, which allows water to enter but prevents soil from entering. Multiple wellpoints are usually installed in a grid pattern around a construction site or excavation area. These wellpoints are then connected to a common header pipe, which is attached to a vacuum pump.

The vacuum pump creates a negative pressure within the header pipe, drawing water from the surrounding soil through the wellpoints. This lowers the groundwater table, creating a dry working environment for construction activities. Wellpoints are particularly effective in sandy or silty soils where water can flow relatively easily. The depth of wellpoints is limited, usually to around 15-20 feet, due to the limitations of vacuum pumping.

For deeper excavations, a multi-stage wellpoint system, where successive rows of wellpoints are installed at lower elevations, may be required. Dewatering with wellpoints is a common and cost-effective method for managing groundwater in many civil engineering projects. The collected water is typically discharged to a designated area or storm sewer system, in compliance with environmental regulations. The installation and operation of wellpoint systems require careful planning and monitoring to ensure effective dewatering and minimal environmental impact.