Tanners Lake Alum Treatment Facility

A unique treatment facility to remove phosphorus from stormwater.

The Tanners Lake alum treatment facility was constructed to reduce phosphorus in stormwater for the Tanners Lake watershed. This water quality treatment method was fairly new and unique at the time of its construction.

Aluminum sulfate (known as alum) is injected into stormwater, which is diverted to a settling pond upstream from Tanners lake. The alum binds to phosphorus in the water and forms floc, a thick sludge that settles to the bottom of the pond. Stormwater that drains out of the pond and eventually to Tanners Lake contains 70 to 80 percent less phosphorous than it did before.

The project included construction of a small building to house the alum injection equipment and the floc settling pond with a weir at the outlet.

*This project is part of a larger plan called Tanners Water Quality Improvements, which was implemented based on results of a diagnostic feasibility study that began in 1989.