Well Siting, Isolation Distances, and Source Water Protection
This domain tests whether a proposed well location protects drinking water from contamination. The exam expects you to apply Iowa isolation distances, evaluate drainage and flooding, and recognize source-water threats that are not captured by a simple tape measure.
Isolation distances
Iowa's rule includes a table of minimum setbacks between a well and contamination sources. Common domestic requirements include at least 50 feet from a septic tank and at least 100 feet from an absorption field or disposal field. Larger setbacks apply to livestock yards, lagoons, chemical storage, and land application areas. Measure from the well casing, not from the pump, pitless adapter, or property line. The setback must be met at the actual proposed location, not at the driveway entrance.
Source water protection
A well should be on higher ground with surface drainage away from the casing. Avoid flood-prone areas, swales, and zones where runoff ponds. In karst or fractured limestone terrain, contaminants can travel quickly, so setbacks alone may not be enough. Check whether the site is in a source water protection area and whether upgradient land use poses a risk.
Worked example
A proposed well is 40 feet from a septic tank and 90 feet from the absorption field. It fails both minimums: 50 feet and 100 feet. Moving it to 60 feet from the tank and 110 feet from the field satisfies those two distances, but the plan still must check setbacks from property lines, livestock, and chemical storage, and confirm drainage away from the casing.
Traps
Measuring from the wrong point; assuming a downhill location is safe because the tank is far away; ignoring seasonal high water; and treating a waiver as automatic when a variance requires documented review.