Summary #
Diversion wells add alkalinity to acidic, low-metal water by dropping it through a pipe into a well filled with crushed limestone. The force of falling water suspends and crushes the limestone, preventing armoring and maximizing neutralization. This page explains how diversion wells work and their frequent maintenance needs.
Information taken from:
Swatara Creek Diversion Wells – Pictures of successful limestone diversion wells on a Swatara Creek tributary.
DEP – The science of AMD and passive treatment
Diversion wells add alkalinity to waters that have low pH and low dissolved metal concentrations.
In a diversion well, acidic water falls vertically through a pipe from an upstream dam into a downstream “well” that contains crushed limestone. The drastic drop in elevation gives the water enough force to suspend limestone gravel located at the bottom of the well, creating a “fluidized bed.” This churning limestone gravel crushes itself, increasing its neutralization ability and preventing armoring (the coating of limestone with iron oxide from the AMD).
The water, now with higher alkalinity, flows upward and overflows the well, where it is diverted back into the stream. Some of the pieces of limestone are also carried up out of the well and enter the stream, where they line the stream bed to continue neutralizing acid.
Operations & Maintenance Considerations #
Diversion wells have to be refilled with clean limestone approximately every two weeks.
Related Pages #
- Limestone Channels — Another simple limestone-based approach
- Limestone Sands — For small streams with low metals
- Treatment Strategies — When to use diversion wells
- Operations, Maintenance and Replacement
Source and Last Reviewed #
Source: AMR Clearinghouse (amrclearinghouse.org). Migrated to AML-Connect. Last Reviewed: 2026-03-13.
[Admin note: Some external links in this article may be outdated. Verify before relying on them. Flag dead links for removal or replacement.]
Tags: passive-treatment, alkalinity, o-and-m, practitioner
