Lake Horowhenua Trust and Lake Accord chairman Matthew Sword said the Lake Trust had supported Horizon's approach.
"This is something our owners have been waiting for."
However, Hokio A Trust chairperson Philip Taueki said he would appeal the Court's decision.
"My attitude to the lake cleanup is simple: remove the toxic sediment from the lake bed, stop further sediment and pollution entering the lake, stop storm water discharging into the lake and relocate the Levin Wastewater Treatment Plant."
He said these were proven safer options than weed harvesting which had never been tried in New Zealand or anywhere in the world.
"What happens if it fails? Even their [Horizons] experts agreed weed harvesting posed a risk of the lake flipping."
Flipping is when the water turns a grey-green colour due to pollution and lack of aquatic plants.
Mr Taueki said he has a dredging firm ready to remove the toxic sediment from the bed, funded by Central Government, that would take only 12 months to complete, and an appeal going through the Maori Land Court to remove stormwater discharge and relocate the Levin Wastewater Treatment Plant.
He said Horizons and the District Council failed to consult with tangata whenua and the lake owners. Muaupoko Tribal Authority and the Lake Trustees are not the lake owners, and do not represent tangata whenua, he said.
Horizons natural resources and partnership manager Dr Jon Roygard said Mr Taueki had expressed his views to two hearings on this matter now.
In both cases the decisions had backed the scientific evidence presented by Horizons from two of New Zealand's leading lake scientists, one from the NIWA and another from the Cawthron Institute who have experience working with Lake Horowhenua.
"It is incredibly frustrating that around $200,000 has been put into an appeal process that has brought us back to pretty much the original decision.
He said the lake had an established history of an annual flipping cycle, due to lake weed growing rapidly over winter and dying naturally in summer, creating algae that caused toxic conditions for aquatic life.
"Weed harvesting will reduce toxic conditions for aquatic life."
Dr Roygard said monitoring clearly showed the Arawhata Stream as the major contributor of lake sediment.
The sediment trap aimed to remove about 50 per cent of sediment from the stream, equating to about 25 per cent of the total sediment from all streams flowing to the lake.
"An additional benefit of the sediment trap is the removal of about 30 per cent of phosphorus that flows into the lake from all tributary streams."
There was also an investigation into potential methods to safely remove the sediment from within the lake, as if incorrectly done it could release significant amounts of nutrient, sediment and toxic chemicals such as sulphides ... that would eliminate most aquatic life in the lake, he said.
Stormwater improvements were also part of the Lake Accord projects as well as working with dairy farmers and horticulture , supporting stream fencing and planting through financial grants.
"Another appeal will likely further delay these works," said Dr Roygard.
