What is a characteristic of bentonite in well construction?

Bentonite is widely recognized in well construction for its sealing capabilities, stemming from its highly absorbent properties. When bentonite clay absorbs water, it expands significantly, creating a waterproof barrier that effectively seals off the well. This characteristic helps to prevent contaminants from entering the water supply, ensuring the safety and quality of the groundwater.

The other options do not accurately reflect the primary uses or characteristics of bentonite in well construction. While some materials may facilitate water flow or be utilized in drainage systems, they do not possess the same sealing properties that bentonite does. Additionally, bentonite is not primarily a construction material in the sense of providing structural integrity in construction projects; its main role is in sealing and preventing fluid migration in well applications.