What type of wellpoints are sealed at the surface using bentonite or clay?

The type of wellpoints that are sealed at the surface using bentonite or clay are specifically designed to prevent the infiltration of surface water and contaminants into the well. Bentonite and clay provide an effective seal due to their ability to swell when wet, which creates a waterproof barrier. This is critical in sanitary engineering to maintain water quality and protect groundwater resources.

Vacuum wells utilize vacuum pressure to draw water from the ground, which is complemented by proper sealing at the surface to enhance efficiency and prevent contamination. This sealing process is especially important in applications where groundwater is being extracted for drinking water or other sensitive uses, as it helps to ensure that only clean water is drawn into the well system.

Both open wells and deep wells typically do not require such sealing with bentonite or clay at the surface, as their construction may involve different methods that do not necessitate a more intricate sealing process. Shallow wells, while they might also face contamination issues, do not usually employ the same sealing techniques prevalent in vacuum wells. Therefore, the correct association of surface sealing with bentonite or clay is specifically with vacuum wells.