To improve the health of Normandale Lake, the Nine Mile Creek Watershed District and City of Bloomington will conduct a lake-level drawdown, selective herbicide treatment, and alum treatment.
Normandale Lake has high phosphorus levels (>60 µg/L) and potentially high phytoplankton amounts, which contribute to water quality concerns. The lake has an abundance of curly-leaf pondweed, an aggressive invasive aquatic plant, which results in limited plant diversity. Low plant diversity along with low dissolved oxygen levels pose concerns for the lake’s aquatic communities. Excessive aquatic plants and filamentous algae in the lake cause late summer algal blooms, resulting in bad odors and impaired recreational use of the lake. The Normandale Lake Water Quality Improvement Project will address these issues.
Winter conditions were favorable for a good freeze of the lake sediment. In February, the top 15-24 inches of sediment across Normandale Lake were frozen. We are quite hopeful that we will see a dramatic reduction in the curly-leaf pondweed plant population. Comprehensive aquatic plant monitoring will be conducted in summer and fall of 2019 to measure the success of the lake drawdown in controlling curly-leaf pondweed. We will have a much better understanding of the effect of the drawdown once the plant surveys are complete.
The project involves multiple steps to address concerns associated with a prevalence of curly-leaf pondweed in Normandale Lake and the release of phosphorus from lake-bottom sediments (internal loading).
A temporary pump and an existing bypass pipe was used to draw the lake down in late-summer 2018. At the same time, the District installed a larger bypass pipe to maintain the lake drawdown and decrease potential impacts of rainfall or snowmelt events during the drawdown period. The new pipe was installed on the north side of the existing lake outlet structure. The pipe extends into the deepest spot in Normandale Lake and conveys water from the lake, under the embankment and directly into Nine Mile Creek downstream of the existing outlet. Once the larger pipe was installed, the pumping stopped and the larger pipe was used to maintain the drawdown. Following the drawdown, the lake was re-filled in mid-March 2019.
A drawdown is one way to control curly-leaf pondweed, and to a lesser extent internal phosphorus release from sediment. Curly-leaf pondweed primarily reproduces through vegetative propagules called turions. Turions are produced in late spring, remain dormant in sediment through the summer, and germinate under cooler water conditions in the fall. However, a winter freeze of the lake sediment bed can kill the turions, thus stopping the curly-leaf pondweed’s reproductive cycle.
In-lake Alum Treatment
When aluminum is applied to a lake as a solution of alum (aluminum sulfate), it forms an insoluble aluminum hydroxide floc that settles to the lake bottom. The aluminum binds with phosphorus in the sediment to prevent it from recycling back into the water column. The alum application was conducted on May 7-8, 2019, after the lake was refilled. Alum was applied from a treatment barge. Conducting the alum treatment before aquatic plants are reestablished in the lake will allow the aluminum floc to reach the sediment more uniformly.
Chemical Treatment of Curly-leaf Pondweed
Herbicide treatment with Endothall, a curly-leaf pondweed-selective herbicide, will occur to target any remaining curly-leaf pondweed in Normandale Lake. Endothall is most effective when applied in the spring when the water temperature is approximately 55-60oF. Endothall is applied from a treatment boat or barge. This will occur in 2020, based on results from the 2019 plant survey. The herbicide treatment may need to occur yearly, for up to five years. The need for herbicide treatment will continue to be assessed based on plant surveys.
A 2018 fish survey indicated that carp are at a level in Normandale Lake where management is recommended. A follow-up fish survey was completed in 2019 to assess carp levels and the native fish population following the drawdown. It was noted during the survey that a large carp spawning event had occurred following the drawdown. The survey results from 2019 will be available soon. In addition, 12 carp were radio-tagged for tracking in 2019. It was found that carp were leaving Normandale Lake, suggesting that there are carp nurseries outside of the lake. Efforts will continue in 2020 to determine the best methods for carp control in Normandale Lake.
The lake drawdown began August 20th, 2018. The District began refilling Normandale Lake on March 7th and the lake was full on March 14th, 2019. The alum treatment occurred on May 7-8, 2019. The herbicide treatment is planned for 2020.
What’s happening now?
(June 21, 2019) Algae in Normandale Lake
With the recent drawdown and alum treatment, it can be expected that 2019 will be a transition year in terms of the amount of algae in Normandale Lake and overall water quality. We anticipate that the amount of native aquatic plants in the beginning of the 2019 summer season will be lower than normal. Aquatic plants compete directly with algae by taking up nutrients (phosphorus) and by causing shading. With the potential for lower aquatic plant abundance in 2019, algae may thrive due to the reduced competition for nutrients and sunlight. The result may be more variable algae populations in the lake this summer. In following years, we anticipate the native plant population rebounding and the overall amount of algae reduced. While in the long-term we anticipate reduced algal blooms, it is important to recognize that there will likely always be moderate levels of algae in Normandale Lake, with Nine Mile Creek flowing through and serving as a daily source of phosphorus to the lake. Learn More
(May 7-8, 2019) Alum Treatment
On Wednesday, May 8th, HAB Aquatic Solutions finished the alum treatment on Normandale Lake. The alum was applied via an alum treatment barge, which was refilled from tanks stationed at the Normandale Lake boat launch.The treatment began on Tuesday, May 7th, and was mostly completed then to take advantage of the calm weather. The alum treatment will help control phosphorous in the lake, the nutrient that fuels algae growth.
(April 15, 2019) Carp Radio Tagging
Staff from Carp Solutions were at Normandale Lake radio tagging carp. They inserted radio tags in the fish before releasing them back into the lake for later tracking. The results from the radio-tagging and a fish survey that Riley-Purgatory-Bluff Creek Watershed District will perform this summer will help determine the best approach for managing the carp population in Normandale Lake.
(April 10, 2019) Alum Project Notice to Proceed
A contractor has been selected, HAB Aquatic Solutions, to conduct an alum treatment on Normandale Lake and the notice to proceed has been issued. It is anticipated that the alum treatment will occur on May 7 and 8.
The alum treatment will help control phosphorous levels in the lake. Phosphorous is a nutrient that feeds algae. Alum is applied to the lake using specialized equipment and barges that ensure the precise placement of the material in the lake. On contact with the water, the liquid alum forms a fluffy aluminum hydroxide precipitate called floc. Aluminum hydroxide (the principle ingredient of common antacids such as Maalox) binds with the phosphorus to form an aluminum phosphate compound. This compound does not dissolve in water and the bound phosphorus can no longer be used to fuel algae growth. As the floc settles to the bottom, phosphorus and particles are removed from the water, leaving the lake noticeably clearer. The floc then forms a thin layer on the bottom. The floc layer keeps the phosphorus from entering the overlying water and makes it unavailable to algae. The result is a reduction in the frequency and intensity of nuisance algal blooms, rather than the total elimination of all algae.
Join us for a demonstration of this process by HAB on Wednesday, May 8 at 12:15 at the Normandale Lake Boat Launch on Chalet Road in Bloomington.
(March 14, 2019) Normandale Lake Full
Normandale Lake filled quickly due the rain and melting snow, and is full as of today. The Nine Mile Creek Watershed District closed the outlet structure allowing the to refill on March 7, 2019.
The District will conduct plant surveys this summer to determine the success of the drawdown on the curly-leaf pondweed population. However, the weather conditions this winter were conducive to a hard freeze of the sediment. At the beginning of February, the top 14-24″ of the sediment across Normandale Lake was frozen.
(March 7, 2019) Refilling Normandale Lake
The pipe keeping Normandale Lake drained was closed today, so the lake will refill for the spring. The length of time it will take for the lake to refill will depend on weather conditions. However, it is expected that the lake will be full by the end of March. Watch progress from the Normandale Lake Cam.
(December 22, 2018) Normandale Drone Video
As Normandale Lake remains drawdown for the winter, this drone footage provides a great view of Nine Mile Creek as it flows through the lake.
(November 26, 2018)
Remember, you can take a live look at Normandale Lake from the Normandale Lake Cam!
(November 1, 2018) Pipe Installation
The contractor has installed the upstream portion of the 36″ pipe (the section of the pipe that goes into Normandale Lake). This allows us to continue the drawdown without pumping.
(October 12, 2018) New Project Update Video
Learn about the latest project updates with a new video from the City of Bloomington.
(October 5, 2018) Pipe Installation
Installation of the downstream portion of the permanent 36″ bypass pipe and new manhole is complete. With this installed, the pumps have been shut off at Normandale Lake. Using the newly installed 36″ pipe and the 18″ pipe that was in the lake, lake levels will drop about 0.5 feet a day once the rain stops. When lake levels are low enough, the upstream portion of the 36″ pipe will be installed into Normandale Lake. The project remains on track for the lake to be drawndown for winter freeze.
(September 27, 2018) Drawdown Pumping Resumes
Water levels at Normandale Lake have dropped enough from the recent rains to allow pumping to resume to continue the lake level drawdown.
(September 20, 2018) Live Camera
Watch the Normandale Lake Project live from the Normandale Lake Cam!
(September 19, 2018) Drawdown Update
Normandale Lake was substantially drawndown on September 15 and water levels continued to drop in the lake through September 17th. With several inches of rain falling during the week, the lake quickly filled up due to Nine Mile Creek flowing through the lake. It was anticipated that lake levels would bounce up and down during the project due to fall rains, and the project remains on schedule. Once flooding subsides at Normandale Lake, pumping will resume.
(August 20, 2018) Drawdown Begins
The drawdown on Normandale Lake began on August 20. Lake levels will remain drawn down until March 2019 when the lake will be allowed to refill. The lake will refill by April 2019, depending on climatic conditions.
Current Project Activities:
- Pumping water until new bypass pipe is installed (complete)
- Opening an existing bypass pipe (complete)
- temporary fencing to protect turtles and guide them to new overwintering habitat (complete)
- a temporary weir to control upstream water levels (complete)
- a larger, permanent bypass pipe (complete)
During the drawdown you will notice:
- Low lake levels until early April
- Restricted access to the lake edge due to the turtle fencing
- Closed boat ramp
How will the drawdown affect the wildlife?
A turtle protection fence was installed to guide turtles to safe over wintering habitat as the lake levels go down and keep them off nearby roads. As required by the Minnesota Department of Natural Resources, the lake drawdown needs to be substantially complete by September 15, 2018. This allows turtle enough time to leave the lake, find new habitat,and begin hibernation before the winter. Contact Bloomington Animal Control if you see turtles on the road or paths near Normandale Lake: (952) 563-4942.
As lake levels drop, fish can leave the lake over the outlet dam (until water levels are below the dam) and through the bypass pipe. There will also be a pool of water left in Normandale Lake throughout the drawdown period. The District will work with the Minnesota Department of Natural Resources to restock Normandale Lake in the spring of 2019.
Muskrats and Beavers
Upstream and downstream of Normandale Lake are habitat areas suitable for muskrats and beavers. Muskrats and beavers should leave Normandale Lake on their own during the drawdown to find suitable habitat.
Many lakes in the area, including Normandale Lake, can serve as stop-over resources for migrating waterfowl. During the drawdown period, Normandale Lake may become less attractive for migrating waterfowl, causing birds to seek refuge at other nearby lakes (Bush Lake, Anderson Lakes, Hyland Lake, Lake Edina, etc.). Effects to migratory waterfowl are expected to be temporary, lasting only for the duration of the lake drawdown. Normandale Lake is expected to again function as a migratory waterfowl resource upon completion of the drawdown phase.
More information on wildlife impacts is available in the Environmental Assessment Worksheet that was voluntarily completed for the project:
Two public meetings were held on May 15th and May 24th regarding the project, and a public hearing was held on June 12th, 2018. An Alum Treatment Demo was held on May 8, 2019.
Project Brochure: Normandale Water Quality Improvement Project Brochure (PDF)
Fish Survey Results: Normandale Lake 2018 Fish Survey Summary
The City of Bloomington and the NMCWD partnered to create two educational videos about the project.
Pack your bags, pondweed!
Upcoming water quality project to clean up Normandale Lake
Lake users will notice low water levels in the lake from late summer 2018 to early spring 2019 during the drawdown. You will see boats on the lake in May 2019 completing an Alum treatment. After the lake refills, and the project is complete, a healthier plant population will grow in the lake.
The lake management practices considered as part of this project are part of a holistic approach to improving the water quality and ecological health of Normandale Lake. The practices are intended to reduce internal phosphorus loading, improve the native aquatic plant community, and increase the concentrations of dissolved oxygen in the water column, helping the lake’s fishery, reduce foul odors often produced during the summer months, and improve recreational use of the lake.
The District has recently expanded its emphasis on the role of ecological indicators (aquatic plants, phytoplankton, fish, etc.) in overall lake health, as well as the feedback mechanisms between these indicators. Several evaluation factors for holistic assessment of lake health, including water quality, aquatic communities, water quantity, wildlife habitat, and recreation are emphasized. While numerical goals exist for some of these factors (e.g., MPCA water quality standards), other ecological lake health factors will be assessed without strict numerical goals (e.g, health of the aquatic plant communities) before and after the project.
Contact Erica, Program and Project Manager, at 952-358-2276.
DID YOU KNOW?
The City of Bloomington and the NMCWD created Normandale Lake in 1979 for flood control. Since its creation, it has prevented significant flooding in Bloomington. More Information
Normandale Lake Project: Past Updates
(July 31, 2018) Contractor Selected for Project
The District’s Board of Managers awarded a contract to Rachel Contracting to draw water levels down in Normandale Lake and construct a new, permanent outlet pipe in the lake. The lake drawdown is anticipated to begin no later than August 23rd. Once the the drawdown begins, you will slowly see water levels begin to drop in the lake. The lake will be substantially empty by mid-September, depending on rainfall during that time. A pool of water will remain on the west side of the lake. The District will close the bypass pipe in early March to allow the lake to refill by April. In addition, a temporary water control structure (weir) will be installed in the Nine Mile Creek channel just upstream of Normandale Lake to maintain normal water levels in the wetland area north of West 84th Street during the lake drawdown. The District will also install turtle fencing around the perimeter of the lake, allowing turtles to safely find new winter homes.
(June 20, 2018) Normandale Water Quality Improvement Project Ordered
On June 20, 2018, the NMCWD board of managers ordered the Normandale Water Quality Improvement Project.
(June 20, 2018) NMCWD Board decided Environmental Impact Statement (EIS) not necessary
The NMCWD Board of Managers issued a negative declaration that the preparation of an Environmental Impact Statement is not necessary.
(May 30, 2018) Environmental Assessment Worksheet (EAW) Comment Period Closed
The Nine Mile Creek Watershed District released a voluntary Environmental Assessment Worksheet (EAW) for the Normandale Lake Water Quality Improvement Project located in Bloomington, MN for review and comment. The project includes lake-level drawdown, herbicide treatment, alum treatment, possible aquatic plant harvesting and in-lake oxygenation. Written comments on the EAW were received through May 30, 2018.