Net Down Anchor System
Site: Shanks Argyle and Bute Ltd, Moleigh Landfill Site, Oban
Background: The designer, SLR Consulting Ltd (Dr Darren Keogh), were tasked with designing a final capping structure to cap off approximately 15 000m2 of completed landfill.
A 1mm HDPE textured membrane and a geo-synthetic drainage layer (GDL) were chosen as the water proofing layer which would be placed on the prepared sub-grade.
The main challenge facing SLR Consulting Ltd within this project was the fact that no final restoration materials were available for placement upon the 1mm geo-membrane and geo-synthetic drainage layer, which meant both materials, would be left exposed to potential wind displacement, and possible damage, and harmful UV sunlight.
It would be a number of years before an appropriate stockpile of restoration materials could be amassed so SLR Consulting Ltd had to make a very considered and careful decision regarding how the structure would be anchored.
The prospect of potential wind displacement and subsequent damage was very real as Moleigh Landfill site was an extremely exposed site which was regularly subjected to very high wind events, and the site had also experienced previous wind damage to a similar final capping structure which had been anchored by an anchor pin system a number of years prior.
Solution:
Net Down system was chosen to provide the 15 000m2 of deployed geo-membrane and geo-synthetic drainage layer with secure anchorage against potential wind displacement, and protection against harmful UV sunlight until such time that a suitable stockpile of appropriate restoration materials could be built up and deployed.
NET DOWN was supplied in 500cm wide x 100m rolls with each width of NET DOWN being stitched together with a double threaded stitching machine.
Our installation team worked directly behind the geo-membrane installation team: NET DOWN was deployed directly on top of the 1mm geo-membrane and geo-synthetic drainage layer with the outside edges of all the materials placed and back filled in the same anchor trench.
It was important that our installation team worked directly behind the geo-membrane installation team to ensure the installed geo-membrane and geo-synthetic drainage layer were securely anchored as soon as they were deployed.
As well as providing the capping structure with a secure anchor against potential wind displacement, NET DOWN also afforded the below geo-membrane and drainage mat with an 80% UV block.
Considering the UV resistance of the chosen geo-membrane and drainage mat were limited, it was vital that a system of UV protection was implemented to prevent degradation of the below materials which could compromise the integrity and performance of the capping structure.
NET DOWN also provided the below capping structure materials with added durability and protection against potential damage from scavenging animals and vermin.A further benefit of using NET DOWN was the products drainage flow properties which added to the capping structures controlled drainage and dispersal of surface water.
An aesthetic benefit of using NET DOWN was also gained: NET DOWN is supplied in Green which provided an unformed appearance and ensured the capped area blended into the adjacent environment and lessened the visual impact on local residents.
NET DOWN is UV stabilised for a minimum of 5 years ensuring the integrity and performance of the product would comfortably exceed the lifespan requirement of this particular application.
