The well casing should terminate above ground and the ground surface at the well site should be built up when necessary so that surface water will drain away from the well in all directions. A well should be located so it will be accessible for pump repair, cleaning, treatment, testing and inspection. The top of the well should not be within a basement nor under a building with no basement. When adjacent to a building, the well should be at least five feet outside any projection, such as overhanging eaves.
Minimum distances from a well to possible sources of pollution should be great enough to provide reasonable assurance that subsurface flow of contaminated water will not reach the well. Minimum safe distances vary so much with the character of subsurface formations that arbitrarily fixed distances cannot be established.
The real determination of potability of water must be based on bacteriological tests, not on arbitrary distances. The following distances, however, can be used as a guide – providing subsurface materials have the natural filtering capability of sand:
Minimum recommended distances between water supplies and various sources of contamination:
Where the earth formations near the ground surface consist of coarse gravel, limestone or disintegrated rock, distances on the order of those just given do not apply. Greater distances are needed. Distance cannot be relied upon where surface materials such as these permit rapid percolation of water with little chance for natural purification.