Limestone Diversion Wells

Dam for a limestone diversion well on a tributary to Swatara Creek, PA
A small stream is dammed, and a portion of the water is diverted through a pipe to the "well" .


The head (elevation drop) provides force which suspends the limestone gravel, creating a "fluidized bed" in which the limestone is tumbled to decrease particle size. The water, with increased pH and alkalinity, flows back into the stream.


These hoppers store limestone gravel, which is fed to the wells approximately every two weeks. Not all diversion wells are equipped with hoppers; many are fed by hand.

This method is most effective for streams that have low pH, but also relatively low dissolved metal concentrations. Iron and/or aluminum hydroxides precipitate in the stream, but probably over a shorter stretch than without treatment. The limestone must be replenished approximately every two weeks, limiting the use of diversion wells to sites that are relatively accessible.

The technology was originally developed in Europe for treatment of streams and lakes affected by acid precipitation.

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