Inert Recycling (UK) Ltd
DATE OF PROJECT:
Chichester, West Sussex
- Materials Consultancy
- Landfill Engineering
- Construction Quality Assurance (CQA)
- Project Management
Boxgrove Quarry is a former gravel extraction quarry located to the east of the A285 at Halnaker, Chichester, West Sussex. The site has planning permission for the importation of inert waste materials for restoration purposes. To accord with the Environmental Permit a containment facility comprising an artificial geological barrier was to be constructed to the base and peripheral side slopes of the quarry.
The objective of the project was to achieve Environment Agency approval of containment engineering works, in accordance with the Environmental Permit.
ACS were appointed initially to prepare a design and associated Construction Quality Assurance (CQA) Plan for the development works. The design work included undertaking a site investigation and associated materials suitability assessment. These assessments were to determine whether there was a suitable quantity and quality of site derived materials with which to construct the artificial geological barrier.
Following materials assessment, a test pad was constructed using standard procedures and witnessed by an ACS Engineer. Samples of the pad were collected and tested at our laboratory. The tests were to demonstrate acceptable impermeability and confirm optimum moisture content for placement.
Once this was achieved, ACS were retained to provide part-time CQA supervision throughout the development works. At the end, we produced a CQA Validation Report verifying the works were undertaken in accordance with the approved CQA Plan.
We had to show the Environment Agency that we could create a low permeability barrier using the saturated material from the site. This had to be to specified criteria detailed in the Environmental Permitting Regulations: Inert Waste Guidance document. The material comprised a gravel and sand based clay with occasional cobbles and boulders which was stockpiled on site.
This was demonstrated by undertaking a field trial attended by the Environment Agency. The material was placed in layers, ripped, oversize materials removed and the clayey material left to dry prior to compaction.
Undisturbed core samples were recovered from the trial pad and submitted to ACS testing laboratory for triaxial permeability testing. Trial holes were excavated through the full thickness of the trial pad. This enabled a visual inspection as to whether the engineering works had formed a homogeneous layer.
The Environment Agency confirmed that materials from the site could be used as a low-permeability barrier, based on laboratory testing and field trials. This was only if engineered in accordance with the procedures documented as part of the field trial.
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