HomeMy WebLinkAboutOPS 34-23Report to
Executive Committee
Report Number: OPS 34-23
Date: December 4, 2023
From: Brian Duffield
Director, Operations
Subject: Mechanical Harvesting of Eurasian Watermilfoil Weeds in Frenchman’s Bay
- Results of 2023 Pilot Project
- File: A-1440
Recommendation:
1. That Report OPS 34-23 regarding Mechanical Harvesting of Eurasian Watermilfoil
Weeds in Frenchman’s Bay be received for information.
Executive Summary: On April 24, 2023, Council approved the 2023 Current Budget
which included a total of $100,000.00 to continue with the pilot project of cutting and removing
Eurasian Watermilfoil weeds from Frenchman’s Bay. An additional $55,000.00 was approved
in the 2023 Current Budget for consulting enabling TRCA to conduct water testing and a
vegetation survey of aquatic plants in Frenchman’s Bay.
The pilot project was first initiated in 2021, which included a single cut using a dredging
machine that emulsified the aquatic vegetation. After consulting with TRCA on this method of
cutting, it was determined that this was not the best method to control the water weeds and it
was likely to contribute to the spread of Eurasian Watermilfoil weeds. In 2022, Council
approved $100,000.00 in the Current Budget to allow for two cuts through a new method
whereby the weeds are cut, removed from the water and allowed to dry on land, and then
disposed of as waste. Results for the pilot projects in 2021 and 2022 can be found in Reports
OPS 01-22 and OPS 18-22 respectively.
The City consulted with stakeholders who use Frenchman’s Bay for recreational purposes to
review the areas cut during the 2022 pilot project and to determine recommendations for 2023.
It was determined that cutting one lane of five acres twice from oriented north to south would
best benefit the Dragon Boat Club, Pickering Rouge Canoe Club, and small watercraft users.
PHC agreed to cut an additional five acres, in a triangular pattern at their expense to
accommodate the needs of small sail boat programming for the Frenchman’s Bay Yacht Club.
The areas to be cut were marked appropriately with buoys for easy visual identification and
follow up inspections to evaluate the pilot project.
The first cut in 2023 of the delineated areas commenced on July 17 and was completed on
July 25. The second cut commenced on August 31 and was completed on September 6. A
final on-water site inspection was completed September 8 and it was determined by City staff
that the delineated cut areas were acceptable and conformed to the contract.
Report OPS 34-23 December 4, 2023
Subject: Mechanical Harvesting of Eurasian Watermilfoil Weeds Page 2
in Frenchman’s Bay
Discussion: On an annual basis, PHC completes weed harvesting around the docks of
Frenchman’s Bay Marina, Frenchman’s Bay Yacht Club, and an east/west oriented channel
linking the two to the harbor entrance. The weed harvesting is normally undertaken twice
during the growing season, but it may be completed up to five times per season if lower water
levels accelerate weed growth. In 2023, PHC was contracted by the City to continue with a
pilot project for the mechanical weed harvesting and removal of Eurasian Watermilfoil and
other weeds in the areas of Frenchman’s Bay as identified in the contract.
A pre-cut inspection by boat of the areas to be cut was completed on July 14, 2023. The
purpose was to verify the proper delineation of the areas to be cut and to document and
determine the density and height of the weeds to be cut. The first cut commenced on July 17,
2023 and was completed on July 25, 2023. The aquatic weeds were cut, harvested and stock
piled on PHC lands to dry and to reduce the overall weight prior to. The City conducted an
inspection on August 16, 2023 by boat of the cut areas to assess the effectiveness and
success of the completed areas. It was observed that the cut area was very visible, providing a
clear channel for small watercraft use and overall, City staff determined the first cut to be
successful.
Four weeks later, a second harvesting of the weeds commenced on August 31, 2023 and was
completed on September 6, 2023. City staff conducted a final inspection by boat on September
8, 2023 and the observations appeared to validate the recommended methodology of cut and
removal of the aquatic weeds for the 2023 pilot project. TRCA have been providing their
support and expertise during the pilot project in 2021, 2022 and 2023 and verified that the cut
and removal methodology was better suited for a long-term weed management program. The
main takeaways from the 2023 pilot project were as follows:
• It is essential to use the entire allowable cutting season from the start of July to the end
of August to maximize the benefits of a second cut.
• Harvesting and removal of the weeds from the Bay reduces the reseeding and self-
propagation of cut aquatic weeds.
• The harvesting vessel used in 2023 seemed to be effective and efficient in the limited
cut.
• PHC outfitted a net on the rear of the harvesting machine to ensure all cut weed pieces
were collected for disposal.
• Higher water levels in 2023 maintained the cut areas better and longer than when
Frenchman’s Bay experienced lower water levels in 2022.
The pilot project identified the following challenges that will need to be addressed in a
sustainable weed management program:
i. The minimum depth of water needed to operate the harvesting vessel prevents the
weeds from being cut close to shore which can hinder small watercraft access.
ii. Fluctuations in Lake Ontario water levels can decrease the relative depth to the top of
the cut weeds as the water level drops after a successful cut as experienced in 2022.
iii. The five acres cut twice in the 2023 pilot project only allowed one north/south channel
suitable for kayaks and dragon boat activities, but some distance from shore and a
Report OPS 34-23 December 4, 2023
Subject: Mechanical Harvesting of Eurasian Watermilfoil Weeds Page 3
in Frenchman’s Bay
considerable distance from Bruce Handscomb Memorial Park located on the west side
of Frenchman’s Bay.
iv. Cutting a significantly larger area is a more efficient removal method for the weeds, as
frequent returns to shore to empty the cut weeds is inefficient.
The consulting by TRCA, consisting mainly the water testing and aquatic vegetation survey, is
ongoing and will undergo a one year monitoring process with results expected in Q2 2024. The
report by TRCA will provide detailed scientific information that is expected to help identify
reasons why we are experiencing excessive growth rates of Eurasian Watermilfoil and other
aquatic weeds in the Frenchman’s Bay watershed. It will also get an accurate count of the
types and densities of various aquatic vegetation in Frenchman’s Bay to better understand the
best management practices to implement for control of weed growth.
Next Steps
The combined three year pilot project has allowed for the development of a weed harvesting
methodology that can be used in a weed management program and permit an increased level
of small watercraft use of Frenchman’s Bay. Given the unique ownership rights of PHC to
control access to Frenchman’s Bay for weed control, staff will assess the appropriate method
to participate in a weed management program moving forward considering the rights and
responsibilities of both parties.
Attachment: None.
Prepared By: Approved/Endorsed By:
Original Signed By: Original Signed By:
Rob Gagen Brian Duffield
Manager, Parks & Property Operations Director, Operations
BD:rg
Recommended for the consideration
of Pickering City Council
Original Signed By:
Marisa Carpino, M.A.
Chief Administrative Officer