Regional Park Boat Access #1 Closed as Zebra Mussel Containment Barriers Installed

IMG_2859From the Minnehaha Creek Watershed District

Wednesday, August 24, 2016

The Minnehaha Creek Watershed District (MCWD) has discovered zebra mussels at the public boat access to Lake Minnewashta in Chanhassen. While official confirmation from the Minnesota Department of Natural Resources (DNR) is pending, the MCWD and Carver County are working with the DNR to plan a rapid response in the hopes of preventing their spread lake-wide.

MCWD’s aggressive early detection monitoring led to the discovery. During a regular site visit on Thursday, August 18, MCWD staff found four zebra mussels on rocks in shallow water under one dock at the public boat access. Ten more were found in the same vicinity during a lake-wide search the following day. No additional zebra mussels were found outside of the public access. The zebra mussels were between two and 12 millimeters in size, indicating they were likely not reproducing. Water samples were taken to determine whether zebra mussel larvae (veligers) are present. Those test results are pending.

MCWD staff and Carver County are working with the DNR to plan a vigorous and effective course of action. MCWD’s and Carver County’s aquatic invasive species (AIS) programs have set aside funds for AIS rapid response. A barrier has been placed around the public boat access in an effort to contain the infestation. A second barrier was placed at the channel that connects the bay where the public boat access is located to the rest of the lake. Boats are being redirected by signage to the former boat launch area #2, approximately ¼ mile further into the park, until further notice.

Minnewashta channel area

Treatment options are being considered. The low number of zebra mussels detected, their young age and their location improve the chances for success. The approximately 30-acre bay where the public boat access is located is connected to Lake Minnewashta by a small channel that lacks the conditions conducive to zebra mussel survival. Due to these factors and the early detection, it may be possible to eliminate the zebra mussels from the site and prevent their spread throughout the lake.

MCWD conducts regular monitoring of Lake Minnewashta, which is considered at high risk for zebra mussels due to its proximity to Lake Minnetonka, where zebra mussels have been present since 2010. Weekly early detection checks at the public access include examining the zebra mussel sampler and checking rocks and other hard surfaces. MCWD staff also conduct a snorkeling survey at the public access and have equipped citizen volunteers with zebra mussel samplers that they monitor throughout the lake.

More information will be provided as it becomes available. Learn more at

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Zebra Mussels in Lake Minnewashta – Update and Proposed Rapid Response Plan

A meeting was held on 8/22/16 at the Minnehaha Creek Watershed District’s offices to review the discovery of zebra mussels in Lake Minnewashta and develop a Rapid Response Plan of attack. Representatives from the MCWD, Carver County, the city of Chanhassen, the MN DNR, Christmas Lake Homeowners Association and the LMPA attended and the spirit was very cooperative. The MCWD’s Aquatic Invasive Species Program Manager, Eric Fieldseth, led the meeting and provided the following information.

On August 18th, during a routine weekly check, four zebra mussels were found under one of the two piers at the Carver Parks boat launch on Lake Minnewashta. The following day, a team of people inspected a broader area of “Little Minnie” as well as 8 other areas of the lake. Ten additional zebra mussels were found near the launch but none were found beyond the public access. The mussels all appear to be juveniles but water samples were taken to see if infant mussels (veligers) were present. If found, that would indicate the mussels were reproducing. Those results are not yet available.

There is some good news.
1. The mussels were found only in the public areas.
2. The channel connecting Little Minnie to the rest of the lake offers a very poor substrate for mussels to adhere. They like rock and weeds not muck.
3. It appears that only juveniles are present but we are awaiting the water samples
4. It appears to be a recent introduction. As a reference, when Christmas Lake reported their mussel problem, they saw over 5000 in their sample. We caught it early.
5. Conditions are such that containment and treatment are a reasonable option.

Christmas Lake’s experience in 2014 offered some valuable lessons on Rapid Response
1. Immediate response is needed
2. Treat a much larger area than when you found them
3. We’ve learned a lot on what products can be effective at killing them without harmful side effects

A PROPOSED plan of attack was developed. Final actions, costs, approvals and timing are being worked but the proposal is to:

1. Close Carver Park’s Boat Access #1 and reopen Boat Access #2 . Access #2 is to the left of the Public Beach as you are looking to the water. This may prevent transporting zebra mussels from Little Minnie to the larger section of the lake and may happen as soon as Wednesday August 24th. NOTE: This is a shallower launch than Access #1 so proper care much be taken especially with inboard and V-drive boats and some pontoon boats with bunk/fixed height trailers.

2. Purchase and install containment barriers in Little Minnie. The area to be contained is being finalized. Delivery and installation of the barrier may happen as soon as Wednesday August 24th. This effectively closes that launch and all boat traffic into and out of the lake will take place at Launch Access #2.

3. Once contained, work the next steps of the process to eradicate the zebra mussels. This is the hard part!

4. Ensure the zebra mussels have been eradicated, remove the containment barriers and reopen Boat Access #1.

5. Continue monitoring Little Minnie as well as our 10 existing monitoring stations around the lake to assure that zebra mussels are fully eradicated.

The team is still working on finalizing the Rapid Response Plan including developing the eradication plans, securing agreement, approvals, materials and vendors and communicating our plans. The very capable leaders of the team are Eric Fieldseth from the Watershed District and Drew Dickart from Carver County’s Aquatic Invasive Species program. The LMPA offers them and the entire team our hearty thanks.

Finally, although we expect that the MCWD and Carver County will provide a lot of the funding, the LMPA has offered financial support as well. Stay tuned and when a request for donations is made, please give generously.

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About Zebra Mussels

Zebra mussels are small, fingernail-sized animals that attach to solid surfaces in water. Zebra mussels are native to Eastern Europe and Western Russia and were brought over to the Great Lakes in the ballast water of ships. Populations of zebra mussels were first discovered in the Great Lakes in 1988.

Impacts: Zebra mussels can be a costly problem for cities and power plants when they clog water intakes. Zebra mussels also cause problems for lakeshore residents and recreationists; for example, they can:

• attach to boat motors and boat hulls, reducing performance and efficiency,
• attach to rocks, swim rafts and ladders where swimmers can cut their feet on the mussel shells, and
• clog irrigation intakes and other pipes.

Zebra mussels also can impact the environment of lakes and rivers where they live. They eat tiny food particles that they filter out of the water, which can reduce available food for larval fish and other animals, and cause aquatic vegetation to grow as a result of increased water clarity.

Status: Zebra mussels have spread throughout the Great Lakes, parts of the Mississippi River, and other rivers and inland lakes. They are established in Minnesota and were first found in the Duluth/Superior Harbor in 1989. See the infested waters list for more information on water bodies in Minnesota where zebra mussels have been found or water bodies that are closely connected to zebra-mussel-infested waters.

Source: Minnesota DNR

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Zebra Mussels Found in Lake Minnewashta at the Park Boat Launch/Access.

Eric Feldseth from the Minnehaha Creek Watershed District reported that Zebra mussels were found in the water at the Lake Minnewashta boat launch in the Park. More in-water assessments will be done Friday and a plan of attack developed. This might include treatment with copper sulfate. It was suggested that the boat launch be closed and the old launch be used instead. More to follow as information unfolds.

Please check your docks, lifts and boats for any signs of Zebra Mussels, especially those of you living close to the public boat launch. You are the key to early detection of new invasions. Alert us if you find a suspicious plant or animal. Here’s what to do:

1. Note the exact location you found it

2. Take up-close, detailed photos if possible

3. Identify basic characteristics (do you know what it is?)

4. Please complete the online reporting form and notify an MCWD AIS Specialist at or 952-471-7873.

Click here for more info on Zebra Mussels

Additionally please report any suspicious findings to Steve Gunther at

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Carver County Parks Beach on Lake Minnewashta Remains Closed Due to e Coli

UPDATE: I spoke with Sam Pertz at Carver County Parks on 8/16 at 2PM and the net is that their beach on Lake Minnewashta is still closed. Despite the heavy rain last week, the e Coli levels have not declined. They checked the levels at the OLD boat launch and Camp Tanadoona checked theirs and they are both fine. Another sample was collected Monday night at the fishing pier by the beach and results are expected Wednesday.

NOTE that there have been NO reports of illness that Sam or I are aware of.

AUGUST 11, 2016: Lake Minnewashta Regional Park beach remained closed this week after elevated levels of E.coli were recorded in recent water samples.

Sam Pertz, Park and Trails manager for Carver County, said it was a precautionary closing and there have been no reports of illness.

The county closed the beach after two water samplings last week showed E.coli levels above safety thresholds. E.coli is a bacteria that live in the intestines of healthy people and animals and can cause abdominal cramps, diarrhea and vomiting, according to a Mayo Clinic website.

The cause of the E.coli readings were unclear, Pertz said. He noted that a large flock of geese has been at the park this summer but E.coli readings can also be affected by heat and lack of rainfall.

The county routinely takes water samples near the beaches and that’s how the elevated levels were discovered.

“We’ve taken the steps to inform the public and keep the parks safe,” Pertz said.

While Lake Minnewashta Regional Park Beach in Chanhassen hasn’t closed in recent years, Pertz said it’s not uncommon for beaches to face temporary closures. He said beaches on Lake Minnetonka have been closed in recent years and the beach at Baylor Regional Park in Norwood Young America is currently closed for algae blooms.

Another water sampling was scheduled for Tuesday at Lake Minnewashta to determine whether safety thresholds are met, Pertz said. The testing takes several days before final results are available.

Meanwhile, the beach at Lake Waconia Regional Park, which is approximately 15 minutes away from both Lake Minnewashta Park and Baylor Park, is open. Daily vehicle permits purchased at any of the park locations, or valid annual permits, provide access to any of the regional park locations in Carver County.

The rest of Lake Minnewashta Regional Park remains open.

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Aquatic Invasive Species Update

Mike Hoff, an AIS coordinator with the US Fish and Wildlife Service gave a preview on the highly impactful AIS plants and animals that we could likely see in Minnesota and by extension, Lake Minnewashta. These species include:

Spiny waterfleas – this invasive animal is very small, but does significant damage to the zooplankton in the water. In fact, the spiny waterfleas do more damage to the lowest level of the fish food chain than zebra mussels. This species is already in Minnesota and is in Lake Mille Lacs, Lake Superior, and many rivers and lakes in the northern Minnesota counties of Cook and St. Louis

Hydrilla – This plant is commonly referred to as “milfoil on steroids”. It is coming up from the southern US and is already as far north as Indiana. Hydrilla grows aggressively and competitively, spreading through shallower areas and forming thick mats in surface waters that block sunlight penetration to native plants below. Its heavy growth may obstruct boating, swimming and fishing in lakes.

Quagga mussels – The larger cousin of the zebra mussel does more damage to the zooplankton than the zebra mussel. It is widely found in the easternmost Great Lakes and and is having a significant impact on Lake Mead, Lake Powell and the Colorado River in the western US. As of now it is only found locally in the Duluth-Superior harbor area of Lake Superior.

Viral hemorrhagic septicemia (VHS) – This virus affects fish and is currently established in Lake Superior. The virus may have limited affect on some fish, but others may become hyperactive and display nervous symptoms. In its most severe form, fish become lethargic and dark, with bulging eyes as well as liver and kidney abnormalities. They also have bleeding in their eyes, skin, gills, fin bases, skeletal muscles, and internal organs. This form of the disease almost always kills the infected fish.

Starry stonewort – A fast growing algae, found in Minnesota only in Lake Koronis (near Paynesville), but prevalent in New York, Indiana, and Michigan. It forms dense mats from the lake bottom to the surface reaching heights of 10-12 feet. The dense mats directly impact the habitat used by native fish for spawning. It is difficult to mechanically remove from an inland lake because of the large amounts of biomass. Additionally, it is typically the first to reestablish in the disturbed area because it is such an aggressive and efficient recolonized.

Supporting and using the pre-launch inspection at all accesses to the lake is important to prevent any of these invasives from entering our lake.

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