A decade of work reduces pollution in St. Cloud's Lake George

Image of in-progress installation of stormwater treatment facility near Lake GeorgeLake George has long been a centerpiece and gathering place for many community events and recreation in St. Cloud. Elevated phosphorus levels, and subsequent low water clarity, resulted in Lake George being placed on Minnesota’s Impaired Waters list in 2012. "Impaired" waters are those that don't meet water quality standards.

The City of St. Cloud conducted an analysis of the 125-acre sub-watershed surrounding Lake George to determine what was causing the water quality problems, find solutions, and implement restoration and protection strategies. With the analysis completed in 2017, the city and its partners started taking action in 2018.

A stormwater treatment pond just south of Lake George, affectionately known as Little George, was constructed in 1998 to capture sediment and pollutants before they reach the lake. Little George was dredged for the first time in November 2018 to restore treatment capacity. More than 900 tons of sediment — about 50 semi-truck loads — were removed from the pond and disposed of at a landfill. The city also added iron filings to the pond as part of a partnership study project with the University of Minnesota, with assistance from the Minnesota Conservation Corps. The iron filings are intended to trap phosphorus and reduce its release from the pond, to keep it out of Lake George.

The lake also received four alum treatments in 2018. When applied to water, alum forms a fluffy aluminum hydroxide precipitate called a floc. As the floc settles to the bottom, it removes phosphorus and particulates (including algae). The floc settles on the lake-bottom sediment where it forms a layer that acts as barrier to phosphorus, which is then no longer available to fuel algae growth.

Further treatments were completed in 2019 and 2020, in an effort to reach water quality goals. For some lakes, alum treatments are a safe, relatively low-cost, effective, and long-term method for controlling phosphorus, minimizing algae growth, and improving water quality.

To address stormwater runoff before it enters Lake George, an underground stormwater retention and filtration treatment facility was installed in 2020, under the parking lot off the northwest corner of the lake. It uses settling chambers and a filtration system to capture sediment and remove phosphorus before it enters the lake. Each year, the system keeps estimated 29.7 pounds of phosphorus and 23,600 pounds of sediment out the lake. This project was funded with a $697,000 Clean Water Land and Legacy Grant received in partnership with Stearns County Soil and Water Conservation District.

These projects, along with improved rain gardens and expanded shoreline restorations, have combined to help Lake George meet, and exceed, water quality standards; the MPCA has proposed removing the lake from Minnesota’s Impaired Waters list in 2022. The state phosphorus standard for Lake George is 40 parts per billion (ppb). When the lake was added to the 2012 list, phosphorus levels were at 45 ppb. With all the work done by the City of St. Cloud and its partners, phosphorus levels in 2021 are holding at 18 ppb, and water clarity has increased from a depth of 5.8 feet in 2010 to nearly 10 feet currently.

Learn more on the City of St. Cloud website: Lake George water quality improvement project