Site Activity – Phase 1
Mobilisation and initial set-up in 2013
During February 2013, temporary welfare units and cabins for use by the site staff were erected. Monitoring points were fixed around the site boundary and excavators removed the discharge pipe from the lagoon which was then decontaminated. In addition, John’s Lane was tidied with the rubbish removed and vegetation cleared. We also had to remove some of the site’s vegetation to give access to the perimeter of the lagoon.
Site Activity – Phase 2
Landscape alterations in 2013
Due to the works that had to be conducted onsite, we had to create a perimeter track for use as access around the lagoon. Where possible we used existing material onsite to widen areas around the edge of the lagoon. The North bank was not suitable for this method and required a path to be created at the top of the bank. We also widened and reinforced the causeway (the land platform between the two lagoons) by importing material (crushed concrete) from off site and depositing it on the causeway. In addition, excavators created a level beach area on the southern side to assist with the launching of the geotextile sheet.
Northern Slope stabilisation
When the access route for the northern area was being confirmed, it was identified that the northern slope would benefit from work being undertaken to further strengthen and stabilise it. As a result the northern slope has undergone dramatic change; it has been completely re-profiled and compacted. The slopes of the north bank have also been re-planted.
Site Activity – Phase 3
Dredging the small lagoon in 2013
The aim of this phase was to dredge and remove the sediment from the smaller lagoon into the large lagoon.
During the dredging of the small lagoon, the dredger struggled with the density of algae in the bottom of the lagoon. As a result, the algae had to be raked out and removed from the lagoon. The algae was then used as a composting material mixed with topsoil and placed on the eastern bank of the site.
Site Activity – Phase 4
Dredging the large lagoon in 2013
During this phase, the sediments at the base of the large lagoon were levelled with the dredger to provide a level surface in preparation for the installation of the geotextile sheet. The sediment was treated during the dredging process to encourage rapid resettling.
Significant amounts of algae were identified in both lagoons and prior to dredging the algae had to be removed. It was then de-watered and used as composting material mixed with topsoil and placed on the eastern bank of the site.
Wastes potentially contaminated with phosphorus, for example the geotextile from the trial, have been retained on site, in line with the waste management licence.
The image above shows the head of the dredger cutter.
Site Activity – Phase 5
Geotextile sheet installation in 2013
The next key stage in the works programme was the installation of the geotextile layer on top of the levelled sediments, at the base of the large lagoon. The layer was pulled out in sections onto the lagoon, which were sewn together once on the water.
Once sewn together, rocks were placed on the geotextile in order to sink it to immediately above the silt in the lagoon – this then provided a supporting layer for the sandy material. Once the geotextile layer had been sunk, it was anchored to the shoreline. Sand was then imported and placed over the geotextile, forming a cap. During this time, the site was very active, with up to 40 deliveries of sand a day.
Site Activity – Phase 6
Sand deposition in 2013
Following the submersion of the membrane, sand was delivered to the site and was deposited on top of the geotextile sheet to secure it in place and provide a barrier between the waste and the feeding birds.
Site Activity – Phase 7
During this phase, work occurred around the edge of the large lagoon in order to anchor the geotextile sheet in place. In addition landscaping of the north bank was completed.
Site Activity – Phase 8
This represented the last phase of works at the site and involved demobilising everything from site, for example removing all of the welfare cabins, the temporary works-related monitoring points and tidying the site.