Desilting ponds and lakes
“Given time, it is the ambition of every lake and pond to become dry land”
Soil washed downstream by rivers or migrating from banks, organic matter from dying vegetation and leaf litter, waste from fish and wildfowl – all these things build up in a lake or pond.
Over time, that lake or pond will become eutrophic with very little oxygen at the bed to oxidise organic waste.
As the build-up of waste increases, emergent plants colonise the surface.
Eventually, small trees and scrub will become established and our pond or lake will have fulfilled its ambition.
Periodically, therefore, build-ups of silt shoud be removed so as to extend the life of the lake or pond and make it more biologically diverse, supporting a greater variety of flora and fauna.
Silt removed from a lake or body of water is classified as waste by the Environment Agency, and as such is subject to the waste regulations. This means that the silt disposal process is controlled by legislation. (See our Waste Management section for more details.)
The desilting process
The first stage of the desilting process is to carry out a survey to establish the depth, and to analyse the chemical composition of the silt to characterise it for disposal. Silt may contain heavy metal contamination or hydrocarbons from road-runoff that make it hazardous and mean that it cannot be spread on land without remediation. When the quantity and quality of the silt have been established then a disposal plan can be formulated for the purposes of getting permission from the Environment Agency.
Kingcombe Aquacare use various techniques to remove silt and transport it to a disposal area.
Floating dredgers can work on the surface of the water and pump silt ashore using underwater dredge pumps. Alternatively, excavators can be mounted on floating platforms to dig silt and cast it ashore, or put into barges for disposal. Floating excavators can also feed pumping systems.
If water can be drained out of a lake, silt can then be excavated and hauled in dump-trucks to a tip site, or it can be loaded into a pumping system where it is screened and macerated before being pumped to a disposal area.
Pumping silt reduces the impact of the works because there are not dumpers running backwards and forwards to the tip area.
We have carried out various hazardous waste remediation projects where the quality of the silt has been changed to remove the pollutants, so allowing the silt to be disposed of on site.
The costs for off-site disposal of silt are very high because of haulage, land fill tax and tipping fees. Before silt can be transported off-site it must be dried, and this requires additional equipment and storage space.
Silt can be composted by the addition of green waste to condition it. The composting process is controlled by legislation and the material that is ultimately produced is considered a product, not a waste and so can be used in different ways.
For more information, or to discuss your particular requirements, call Chris Keech on 01460 279200.