What types of openings are permitted in the casing wall?

The correct choice emphasizes that only pitless adapters are permitted openings in the casing wall, which aligns with safety and regulatory standards in well construction and maintenance. Pitless adapters are specifically designed to create a watertight connection between the well casing and the water delivery system. This prevents contamination from surface water and ensures that the integrity of the well is maintained.

Allowing any type of opening would pose a significant risk to groundwater quality, as it could introduce contaminants and compromise the well's structure. Similarly, large diameter openings would not only be impractical but would also weaken the casing wall, making the well more susceptible to collapse or contamination. The sole allowance of holes cut for lifting the casing does not adhere to the principle of maintaining a secure and protected well structure during installation or removal. Instead, focusing on the utility and design of pitless adapters provides a reliable solution that meets both operational and safety needs.