Lightweight Fill Provides an Effective Drainage Solution






Leca recently collaborated with WSP and Alun Griffiths Contractors to pneumatically deliver LECA® LWA as a drainage solution for a remedial work on a steep embankment in Newport, Wales. This unusual project assembled by the Government in South Wales required a lightweight drainage solution to be delivered to a difficult to access area with heavy oncoming traffic area from the A4042. The average depths of lightweight fill required on site was around 2.3m. 

The busy highway section of the A4042 meant there was no opportunity for the contractors to the stockpile material, so the ability to pneumatically deliver LECA® LWA provided an effective solution, with a pneumatic delivery system which could reach up to 50m and be blown to a high tier of the hillside. To compound this was the major concern of any potential damage to the delicate underground filter drainage system which was to be surrounded by the lightweight fill. There was concern that any alternative material installed at a 600mm thickness would impose excess weight on the delicate filter drain piping system – resulting in insufficient support around the pipe. Through specifying LECA® LWA, this issue was solved simply and effectively – thanks to LECA® LWA’s lightweight properties.

As it was identified early in the process that LECA® LWA as a material did not meet the MCDHW Specification for Highways work, a departure was required and this aligned with Leca’s own standard Departure document - this was checked and completed quickly and work could begin.

Leca’s technical team identified that LECA® LWA was suitable for this project as the overall depth of the drainage layer from 2 – 3.5m allowed for LECA® LWA to fully support the 225mm filter drain and to minimise any settlement – requiring a minimum number of passes from a vibrating plate compactor to achieve the required level of compaction. It was confirmed that when LECA® LWA was installed in 600mm layers, this would pose no problems for the installation or more importantly pose no issue for the delicate underground piping system. Furthermore, the project could be completed with a capping layer with a geotextile installed to ensure that there was no possibility of uplift buoyancy from excess rain conditions. 

For the completion of this project the roads were left open during peak traffic periods of 9.30am – 3.30pm, with a single lane closure required, which could accommodate the Leca’s pneumatic delivery vehicle.

This project was completed on time and within the design requirements. Proving that LECA® LWA once again could provide an effective structural engineering solution – offering a multitude of further properties to accommodate the complexity of this project.