Forest Lake Alum Treatment

Project Description & Outcomes

The Forest Lake Alum Treatment Project is a milestone project in achieving Forest Lake’s water quality goals. The Comfort Lake-Forest Lake Watershed District has worked with many partners to construct water quality projects for more than a decade. With the critical support of the City of Forest Lake and the Forest Lake Lake Association, these projects have led to a significant decline in phosphorus entering the lake. The watershed district targets phosphorus, because in excess amounts, it causes algae blooms and lowers water quality. Less phosphorus is entering the lake, but a project is needed to address the phosphorus that is already in the water.

The lake will be treated with alum which will bind to the phosphorus and make it unavailable for algae growth. Alum is a non-toxic water quality treatment that will result in a cleaner and clearer Forest Lake.

The alum treatment will take place in September 2023. The Watershed District will monitor the lake after the treatment to measure success and determine if a second application is needed in 2025.

Public Hearing Presentation

Shields Lake Alum

Project Status

In-Progress

Project Outcomes

527 lbs/yr phosphorus removal

Financials

Clean Water Fund Grants: $533,600

CLFLWD Grant Match: $133,400

Total Project Budget : $667,000

Lifecycle cost:
$100 per pound of phosphorus removed
(What does this mean?)

Timeline

Fall 2023: Alum application #1

2024: Effectiveness Monitoring

Fall 2025: Potential alum application #2

Upcoming Information Sessions

June

Saturday, June 24th | 10:00AM-12:00PM @ Watershed District Office, 44 Lake St. South, Suite A, Forest Lake, MN 55025
Residents can stop by anytime during the two-hour info session; there will be a 30-minute presentation beginning at 11:00am

Thursday, June 29th | 5:00-7:00PM @ Lakeside Memorial Park, 95 East Broadway Avenue, Forest Lake, MN 55025
Residents can stop by anytime during the two-hour info session; there will be a 30-minute presentation beginning at 6:00pm

July & August

Saturday, July 15th | 10:00AM-12:00PM @ Hardwood Creek Library, 19955 Forest Rd N, Forest Lake, MN 55025
Residents can stop by anytime during the two-hour info session; there will be a 30-minute presentation beginning at 11:00am

More informational meetings and events will be held in August. As the details of those meetings are finalized they will be added to this list. Learn more by reviewing the Forest Lake Alum Treatment Education and Outreach Plan.

Arts in the Park

Unable to attend an info session? District staff will be at Forest Lake’s Arts in the Park every Tuesday this summer to answer questions and lead family-friendly water quality activities. Look for the District booth on the north side of the park near the boat launch.

Past Info Sessions

Wednesday, May 17th | Forest Lake Lake Association Annual Meeting

Project FAQ

What is an alum treatment?

Alum (potassium aluminum sulfate) is a nontoxic compound that many people have in their kitchen cupboard. It is used as an additive in pickling and canning, and used by many municipalities for drinking water clarification. When applied to a lake by a specialized service provider, liquid alum forms a white, cotton-ball looking substance called flock. The flock sinks to the bottom of the lake and forms a one-inch thick layer on the bottom. The alum flock attracts and binds phosphorus in the water. Once it has sunk to the lake bottom, it compresses and creates a seal that prevents phosphorus in the sediment from re-circulating. On average, a typical alum treatment is capable of binding 70-90% of the internal phosphorus load in a lake. The watershed district targets phosphorus, because in excess amounts, it causes algae blooms and lowers water quality.

Why are we conducting an alum treatment on Forest Lake

The CLFLWD has worked with many partners to construct water quality projects for more than a decade. These projects have led to a significant decline in phosphorus entering the lake. While less phosphorus is entering the lake, a project is still needed to address the phosphorus that is already in the water. Alum treatments specifically address the phosphorus that is already in the water and as such are often the final step in a multi-year effort to reduce phosphorus in our lakes. The CLFLWD has performed alum treatments on both Shields Lake and Moody Lake.

Are alum treatments safe for people, pets, and wildlife?

Yes. Alum is a non-toxic water quality treatment that has been used to improve lake water quality for decades. District staff and engineers will be actively monitoring the lake during the application to ensure the proper dosing is being applied and that the pH of the water remains stable.

Read the alum treatment FAQ sheet for answers to more commonly asked questions

Project Description & Outcomes

Project Status

Project Outcomes

Financials

Timeline

Upcoming Information Sessions

Project FAQ

Project Partners

Project Gallery (photos from Moody & Shields)