Getting Milfoil Under Control

The project team studied the efforts to remove milfoil from other lakes in New York, particularly Upper Saranac Lake and Lake George, and determined that it would be best to use a two-pronged approach:
1) using divers to hand-pull the weeds
2) using benthic matting to smother the plants.

Improving upon effective designs used elsewhere, the team built and tested a pontoon boat with a suction dredging system and compressed air for divers. The divers pull the plants and feed them into the suction hose, which transports the milfoil to the pontoon platform, where it is bagged. A support boat periodically collects the bags and delivers them to shore, where the milfoil is eventually converted to agricultural compost.

In 2010 we started using geo textile mats laid on the lake bottom. These mats starve the plants of sunlight, which eventually kills them. This technique had been used in other lakes and earlier in Skaneateles, but on a smaller scale. We modified the boats and made equipment to roll out 85 foot by 12 foot rolls of geo textile material.

Initially, we used rocks from the bottom to hold the mats down. We discovered quickly, however, that such a system was not workable everywhere we wanted to mat. We needed a better way to weight the cloth to keep it on the bottom. John Menapace did some small-scale experiments with used cable as weight and came up with the amount of weight that would hold the mats down under all conditions. Based on that he built a 14 ft wide sewing machine to sew pockets in the geotextile cloth every 6 ft on the narrow width of the cloth. He inserted a 12ft length of cable into the pockets. He made up 85ft lengths of geotextile in this manner which, when rolled up on a 14 ft 2X4weighed about 150 lbs.

We load these rolls onto the pontoon boats and take them to the site we want to cover. We lower them into the water and divers roll out the cloth on the weed beds just as you would roll out a carpet in your living room. The geotextile is left down for about 10 weeks. We also built a roll-up barge with a hydraulic reel on arms that go down near the bottom to roll up the mats. The rolls can then be moved to a new site and rolled out again. Last year we rolled out approximately 5 acres of mats.

Aggressive Work Plan

Custom-fitted boats are now in operation, manned by specially trained divers. The boats are working from June to September to systematically eliminate milfoil patches around the lake. Early efforts have focused on shallow areas where the spreading potential is greatest.

We do not expect milfoil to be completely eradicated from the lake, however the population has been reduced so thoroughly by September 2011 that we now feel that control of the weed can be achieved with reduced manpower.

The Solution in 2010

Last year we started using geo textile mats laid on the lake bottom. These mats starve the plants of sunlight and kill them. This technique had been used in other lakes and earlier in Skaneateles, but on a smaller scale. We modified the boats and made equipment to roll out 430 foot by 12 foot rolls of geo textile.

There were plenty of rocks on the bottom to weight the cloth in the first area we did near Mandana. Other areas we planned on doing did not have enough rocks for weighting. We needed a better way to weight the cloth to keep it on the bottom. I did some small-scale experiments with cable as weighting. When I came up with the amount of weight that worked we built a 14 ft wide sewing machine to sew pockets in the geo textile cloth every 6 ft on the narrow width of the cloth. We inserted a 12ft length of cable into the pockets. We made up 85ft lengths of geo textile in this manner which rolled up weighed about 150 lbs.

We load these rolls onto the pontoon boats and take them to the site we want to cover. Divers roll out the cloth on the weed beds. The geo textile is left down about 10 weeks. We also built a roll up barge with a hydraulic reel on arms that goes down near the bottom to roll up the mats. The rolls can then be moved to a new site and rolled out again. Last year we rolled out approximately 5 acres of mats.

We do not expect milfoil to be completely eradicated from the lake, however the population can be reduced so thoroughly by September 2011 that maintenance can be easily achieved with limited manpower.