Well Casing, Grouting, and Sealing Requirements
Domain 3 covers the barriers that keep surface water and shallow contamination out of the well: casing, grout, and the sanitary seal.
Casing
Casing must be watertight and structurally adequate. Steel or PVC is acceptable if it meets the specified wall thickness and diameter for the class of well. Casing must extend above finished grade-commonly at least 12 inches-and be installed into competent material, not stopped in loose fill.
Grouting
The annular space between the borehole and casing must be sealed for its full length with an approved grout such as neat cement, bentonite, or cement-bentonite. Grout is placed by tremie from the bottom upward in one continuous operation to avoid bridging and voids. The grout must cure before drilling out the shoe.
Sealing
A sanitary well cap, screened vent, and proper pitless adapter keep insects and surface runoff out. No direct connection to a sewer or drain is allowed.
Worked example
A 60-ft well has 30 ft of clay over sand. Casing is set to 50 ft into the clay, and grout is tremied from the bottom of the annulus to the surface. This seals the shallow sand and prevents downward migration along the casing.
Traps
Pouring dry bentonite from the top creates bridges and unsealed voids. Grouting only the top 10 ft, stopping casing in fill, and leaving the annulus open are frequent violations. A well cap is not a substitute for grout.