HOPKINTON, N.H. – The U.S. Army Corps of Engineers will temporarily close the swimming beach at Elm Brook Park on Monday, June 3rd and Tuesday, June 4th while portions of both Hopkinton Lake and Drew Lake are treated for the invasive variable milfoil plant. The Stumpfield Road Boat Launch off Route 202/9 and the Drew Lake Boat Ramp off Sugar Hill Road in Hopkinton will also be closed on these dates.
During this time period, Elm Brook Park will continue to remain open to the public (weekday hours of 9 a.m. to 6 p.m.). However, since swimming will be prohibited, user fees will not be charged for entry into the park. Group picnic shelter reservations will still be accepted at normal fees.
Variable milfoil is an invasive plant species that displaces native aquatic plants that provide food, shelter, and habitat for animals, fish, waterfowl, birds, and insects. If left untreated, milfoil will destroy the lake habitat and many of the wildlife species that depend on it will perish.
A chemical herbicide named CleanAmine, EPA Reg. No. 34704-1204-12059 and also State of New Hampshire approved, will be used to treat the variable milfoil. CleanAmine is a formulation of 2,4-D that has been used successfully for the control of noxious aquatic plants, including milfoil, for more than two decades. However, CleanAmine is a recently certified herbicide using the 2,4-D active ingredient. It will be applied as a liquid sub-surface treatment using weighted hoses. For the few areas where the weighted hoses are denied access a calibrated spray system will be used.
Previous treatments used Aqua-Kleen or Navigate and both are also 2,4-D herbicides but applied in pellet form. A pellet form in a clay capsule was not considered with this application for several reasons. It is suspected that because of the influence that the level of sediments in portions of the lake bottom, pellet application may have resulted in delayed or incomplete release of the active ingredient. This can occur because some pellets being deposited in the sediments do not release the herbicide in concentration or exposure time sufficient to maximize control results. This could result in a more than expected rapid rate of milfoil reestablishment.
By contrast the liquid form is designed to release the active ingredient of 2,4-D into the water column faster and at higher concentrations which may result in improved control. A liquid application is also the lower cost product that uses less chemicals while still providing the adequate concentration rates to the milfoil needed to kill the invasive plant and it is recommended for large area treatments.
In addition on May 15, 2013 a pre-treatment survey was coordinated by Amy Smagula, Exotic Species Coordinator for the NH Department of Environmental Services to determine milfoil locations and confirm water depths at several locations in the lake. This will enable the professional applicator to adjust the concentration of herbicide liquid release to coincide with the product label based on water depth.
2,4-D has a short half-life and does not bioaccumulate in the aquatic environment. It is a systemic growth regulator that injures new growth and kills the leaves, stem, and roots. It forces new growth to accelerate causing the plant cells to rupture, thus killing the plant.
The beach closure is a precautionary measure. While CleanAmine has no swimming restriction required by the EPA on the product label, the State of New Hampshire imposes a 24 hour restriction immediately following treatment.
Variable milfoil treatment must take place during the growing season at normal lake levels. Since Hopkinton and Drew Lakes are part of a flood control project that stores water every spring, the timeframe for treatment is limited.
For additional information concerning the Hopkinton Lake and Drew Lake variable milfoil treatment or the temporary beach and boat ramp closures, contact the project office at 603-746-3601.