6.6. SR 11-01-2004
Item # 6.6.
MEMORANDUM
TO: Mayor and City Council
FROM: Rebecca Haug, Environmental Technician
DATE: November 1,2004
SUBJECT: Clarification on the Curly leaf Pond Weed Remediation in Lake
Orono
On Wednesday, October 20, 2004, city staff met with the Lake Orono Water Quality
Task Force. The eradication of Curly-leaf pondweed in Lake Orono was discussed.
There were concerns about the information that was discussed at the October 4, 2004
City Council meeting regarding the Lake Orono drawdown.
To clarify the concerns from the two residents who spoke at the Council meeting, there
was an article in the Elk River Star News prior to the drawdown in 2003. Since the
Lake Orono Improvement Association (LOlA) was sending a flyer out to all the
residents on the lake, city staff did not see a reason to also send an additional flyer from
the city to all the residents along the lake. As far as notifying residents of this year's
proposed drawdown, staff and LOlA were waiting for the proper permits from the
DNR and City Council support prior to notifying residents.
Unfortunately, the information about the turtles being harmed during the draw down in
2003 was brought to the DNR's attention during the week of September 20. 2004. The
DNR was not aware of any negative impacts to the lake. They were in full support of
the draw down until the information about the turtles was presented to them.
Since Lake Orono is a reservoir of the Elk River, the Curly Leaf Pondweed flows down
from upstream. However, if there are no attempts to control this non-native invasive
species, like Eurasion Milfoil, it will choke out the lake, making it undesirable to live on
and lower property values.
The mention of considering the pros and cons when considering the drawdown has
been discussed in depth with the DNR, LOlA. and city staff. The other methods,
mechanical harvesting and herbicide control, of controlling curly-leaf pondweed have
also been discussed. In addition. LOlA contacted other lake associations about their
experiences and costs involved in the eradication of Curly leaf Pondweed. The
following is a pros and cons description for each method:
Winter Draw-down
Pros
Inexpensive
Convenient for the City
Cons
May cause fish kills (not evident in 2003)
Need a DNR permit
Results may be hard to determine until growing season
Mechanical Harvesting
Pros
None
Cons
Can be costly
ALL plants must be removed from the lake
Need a DNR permit
Temporary solution
Herbicide Control
Pros
Contact herbicides act quickly and kill all plant cells that they contact
Aeration, particularly at night, for several days after treatment may help control the
oxygen depletion
Cons
Temporary Water-use restrictions are imposed in treatment areas
Requires a DNR permit
Costly
Sometimes only the stems and leaves die
Oxygen depletions can kill fish
Determining area and/or volume of the pond or area to be treated (much harder when
dealing with a reservoir that has constant water flowing through it)
The DNR has suggested that if the City decides to draw down the lake in 2005. we
begin October I" and October I Sth at the latest. This will give the turtles time to move
down below the new water line. The DNR does understand that this may interfere
with recreational activities on the lake. However, City staff is recommending that the
draw down occur in 2005.
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