Well Siting, Setback Distances, and Grouting/Sealing Requirements
This domain tests the minimum distances that keep a well away from contamination and the sealing work that keeps surface water and shallow groundwater from moving down the annulus. Illinois sets statewide minimums; local ordinances may be stricter but cannot be looser.
Statewide minimum setbacks
- 50 feet: septic tank, privy, sewer line, or other potential source of contamination.
- 100 feet: sewage lagoon, land application of sewage, and similar treatment areas.
- 200 feet: landfill, dump, or hazardous waste site.
Measure horizontally from the closest point of the source to the well. Also avoid floodways and drainageways, and grade the site so runoff drains away from the casing.
Grouting and sealing
The annular space is filled with approved grout - neat cement or bentonite - placed by tremie pipe or positive-displacement pump from the bottom upward. Grouting must be continuous, with no bridging or voids, and must reach the ground surface. Drill cuttings and sand are not substitutes for grout. The wellhead is finished watertight, with the casing extending above grade and a sanitary seal.
Worked example
A proposed well is 45 feet from a septic tank, 90 feet from a sewage lagoon, and 150 feet from an old landfill. All three fail: 45 < 50, 90 < 100, and 150 < 200. The well must be relocated or the source removed; grouting does not cure a setback violation.
Traps that cost marks
Measuring to the house instead of the septic tank; assuming a 50-foot separation covers lagoons and landfills; grouting from the top down, which bridges and leaves voids; and backfilling with cuttings because "the clay will seal it."