Protecting our waters

Opus was recently tasked by Ashfield District Council to collect silt samples on King's Mill Reservoir. The work is to determine whether dredging would have a detrimental effect on the reservoir chemistry, resulting in an increase of blue green algal blooms that naturally occur at the reservoir.

Due to several decades of sediment deposition from an urban catchment, King’s Mill Reservoir in Sutton in Ashfield, Nottinghamshire had become silted up and its capacity to be utilised for recreational purposes and water sports, such as sailing, significantly reduced. Furthermore, in recent years the reservoir had been affected by blue-green algal blooms, which have been linked to high nutrient levels associated with the sediments, and led to the reservoir being temporally closed to the public.

Knowing that there was a requirement for action, Ashfield District Council wished to assess the environmental implications of potentially reusing dredged silt to avoid costly landfill disposal. In addition, there were concerns that dredging activities could liberate large quantities of nutrients from the sediments resulting in an algal bloom that may adversely affect the reservoir’s ecosystem.

In order to provide the most cost-efficient solution for the client, Opus utilised a handheld multisampler to recover sediment cores from the reservoir. The works were completed by two Opus engineers with the multisampler operated from the lowerable working platform of a motorboat. 

Opus was able to demonstrate that the sediments to be dredged did not present potential risks to humans and the environment if they were reused by the district council. As a result, it was determined that the sediments would be suitable for use in creating a new wet woodland landform on the western shore of the reservoir.

Opus' assessment enabled Ashfield District Council to be able to proceed with the most cost-effective solution that eliminated any disposal costs and significantly increased the project's sustainability. In doing so, a new environment can be created that benefits the local community and ecosystem, and the reservoir can also be significantly improved as a water sports facility.