The wells have inside diameters generally between 6 and 18 inches to accommodate the maximum design flow.
Relief wells intercept underseepage and provide a controlled outlet for the water.
They are used to relieve excess hydrostatic pressures in the pervious substratum overlain by more impervious top strata, conditions which often exist landward of levees. A major disadvantage is that wells require periodic maintenance and frequently suffer a loss in efficiency due to clogging of the well screens. Backflooding of muddy surface water, bacterial growth, or carbonate incrustation can all adversely effect a well. Another disadvantage is that wells may also increase the amount of underseepage, which must be collected at the ground surface and disposed of landward of the levee.