General Contractor Practice Exam

What is the preferred method of lowering a high water table prior to earthwork?

1. Wellpoint pumping

2. Pit drainage

3. Subsurface drainage

4. Surface runoff control

The correct answer is: Wellpoint pumping

The preferred method of lowering a high water table prior to earthwork is wellpoint pumping. This method effectively creates a drawdown effect in the soil by using a series of closely spaced, small-diameter wells (known as wellpoints) connected to a vacuum or centrifugal pump. This system allows for the controlled lowering of the groundwater level, making it easier to perform excavation work safely and efficiently. Wellpoint pumping is particularly useful in situations where there is a significant amount of water present in the soil, as it can quickly lower the groundwater level to a manageable point. This method is highly effective in sandy or silty soils where groundwater can influence the stability of the earthworks being performed. By utilizing wellpoint systems, contractors can minimize the risk of flooding, erosion, or destabilization during excavation. In contrast, pit drainage is generally less effective for large areas, as it involves digging a trench or pit that may not adequately lower the entire water table across a wider job site. Subsurface drainage, while useful in managing water after construction, may not be as effective in lowering the water table preemptively in a comprehensive manner. Surface runoff control typically addresses surface water management rather than deep groundwater levels, which is not the primary concern when preparing for earthwork operations