- On 19th July 2018
- In Engineering, Research and Development, Sediment Management
- By William Coulet
Brightlingsea’s paddling pool, situated on the Colne estuary, is a sandy shallow water attraction for seaside tourism. Open to the elements it was designed to be replenished with fresh seawater by each high tide. It has been operating for more than 70 years and in that time the tide has also deposited fine sediment (clay and silt) and organic particles during its twice daily refilling of seawater.
Attempts to maintain the pool attractiveness has included the introduction of clean sand on numerous occasions, however this process of intermittent top ups has now come to its limit as it infringes on the water volume. Exo Environmental was contracted by Tendring District Council to sample, analyse and assess the sediment and provide a solution for the refurbishment programme. Exo Environmental has approached three options in their feasibility study:
- Landfill the sediment with introduction of new clean sand.
- Sediment washing and screening utilising vibrating screen and hydrocyclone technology.
- Stabilisation of sediment into GeoBlock rock armour units for coastal protection.
Strange looks were seen when three men in high visibility jackets descended on the paddling pool early morning in July and began excavating one metre deep holes. Trial pits were dug, with the types of sediment, stratification and other particulars recorded. Sediment samples were taken for further analysis, along with in-situ water tests and samples. These test results detailed the composition of the sediment by particle size and chemical composition.
Larger samples were also taken to progress the GeoBlock concept being developed by Exo Environmental Ltd. The aim of the GeoBlock concept is to reuse dredged or excavated sediment that would conventionally regarded as a waste and landfilled or disposed of at cost. This is a challenging brief due to variety of dredged material, salinity, organic matter content, dredge location and potential contaminants.
From the material taken from the paddling pool, stabilised test blocks were created. The material was mixed with binders and placed into test moulds and left to cure for 28days. They have since been sent to the laboratory for strength testing.
These blocks form part of the solution to reuse the material in an environmental, as well as economically, beneficial way. Further information can be seen on our Research and Development pages and updates on the Paddling Pool will follow.