Lake Minnewashta Preservation Association

LMPA Bulletin – August 25, 2016

Memo From Sam Pertz, Carver County Parks

August 25, 2016

Dear Resident,

This letter is to advise you of changes in boat access operation at Lake Minnewashta Regional Park starting on August 24, 2016 and continuing until further notice. The recent findings of zebra mussels near the Boat Access #1 (main lake access) has resulted in the deployment of water containment barriers in an attempt to eradicate zebra mussels near the ramp and out into a portion of the channel. The containment barriers needed for water treatment will prevent watercraft from entering/exiting the lake from this access.

The former boat access #2, located south of the park’s beach is open for use. We realize water levels can greatly impact the functionality of this access. Having received above average rainfall, the current water level is suitable for most watercraft.

At this time, we do not have a schedule to reopen the main lake access. We are working closely with the DNR and Minnehaha Creek Watershed District staff and will provide information as it is available. Please refer to our park webpage for updated information – specifically located on the Minnewashta Regional Park page (Public Boat Access) at http://www.co.carver.mn.us/departments/public-works/parks-recreation/parks-trails/lake-minnewashta-regional-park.

Should the treatment require a longer-term closure, coordination will be made to allow watercraft the ability to leave the lake through the primary access.

Additional information on the water treatment effort can be found through the Carver County Planning and Water Management webpage at http://www.co.carver.mn.us/departments/public-services/planning-water-management or by phone 952-361-1871, and the Lake Minnewashta Preservation Association website at https://lakeminnewashta.org.

Should you have questions about boat access operations, please contact our office at 952-466- 5250 M-F 7:30a.m. – 4:00p.m.

Sam Pertz
Parks and Trails Supervisor
Carver County Parks

From 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.

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 www.minnehahacreek.org/ais.

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.