Shortlisted for Brownfield Awards Category 8 - Best Re-Use of Materials

Details of the Site 

The Site at Emerson’s Green comprised a 2.3ha  historic landfill located within the boundary of a  larger 99ha site in South Gloucestershire approved  by the local planning authority for a mixed-use  development called Emerson’s Green Urban Village  being constructed by a consortium of national  housebuilders. The landfill was a former valley in the  natural topography that was infilled under license  granted by the local authority with approximately  52,000m3 of commercial and industrial waste in  the 1980’s. The site was covered with a clay cap and  restored to grassland in the early 1990s. 

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Remediation Strategy 

Following removal of the landfill capping materials,  excavation for off-site disposal of the entire volume  of landfill waste and reinstatement of the resultant  void with inert material to construct a development  platform would have involved in the region of 26,000  haulage vehicle movements on local roads. 

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To avoid the disruption posed by this approach, a  remediation strategy comprising excavation of the  landfilled waste for on-site processing to recover  materials that are suitable for re-use to construct  the development platform (soils, gravel, rock,  brick, masonry, concrete) was proposed. Materials  unsuitable for re-use on-site would still require off site disposal, however their quality (by virtue of the  processing to remove all adhering soils) would render  them suitable for recycling (with regard to metals  and rubber) and energy production (with regard to  wood, textiles and paper/cardboard). The resulting  material shortfall to construct the development  platform would comprise imported soils generated  from foundation and drainage excavation arisings across the wider 99ha development area, which  would otherwise have required off-site disposal as  a potential waste. 

 

Regulatory Context 

Prior to commencement of this project, landfill  remediation projects that involved treatment  of site-won materials for on-site re-use had  been undertaken using a mobile plant permit to  Regulate excavation and treatment of the waste in  conjunction with the CL:AIRE Definition of Waste:  Code of Practice (DoWCoP) as a mechanism to  demonstrate that the recovered materials intended  for re-use were not a waste. This regulatory  approach was akin to that adopted at many sites  affected by land contamination (other than landfill  sites) that regularly undergo remediation to enable  redevelopment through the Planning regime. 

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However, at the time that VertaseFLI began pre start discussions with Regulators (January 2018),  it became clear that there was a shift in focus  with regard to the most appropriate Regulatory  regime for landfill remediation projects in England  and Wales. Specifically, it was recognised by the  Environment Agency that, whilst being a valuable  tool to the land remediation industry, the CL:AIRE  DoWCoP was not really intended for materials that  had been previously intentionally discarded into  landfill (and were thus already classified as a waste).  This contrasted with land affected by contamination,  where the Environment Agency considered it  plausible that the contamination was a result  of accidental release as opposed to intentional  discard, and thus the contaminated materials were  not necessarily already classified as a waste. 

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Instead, the Environment Agency’s preferred  mechanism to Regulate the Emerson’s Green  landfill remediation project was a bespoke Waste  Recovery Permit whereby permanent deposit of the  waste to land was the mechanism of ‘recovery’. This  Regulatory position was understandable due to the  unambiguous evidence that the landfilled material  was already a waste. However, in the absence  of case histories (at that time) of landfills being  remediated under this permitting regime, both the  client and VertaseFLI were concerned about the  ongoing viability of the project via this Regulatory  route. Primary concerns were around the following: 

• The timescales to obtain the permit to  commence the works; 

• The timescales to surrender the permit upon completion of the remediation and whether they were compatible with the build and sales programme for the new development  (i.e., would mortgage lenders lend to home buyers if the permit was still active at the time of conveyancing); 

• The apparent hazard-based approach underpinning the waste permitting regime, which is a stark contrast to the risk-based approach underpinning the assessment and remediation of land contamination set out in best practice guidance (e.g. Land Contamination Risk Management guidance published by the Environment Agency on .gov.uk); 

• The potential tendency for the Environment Agency waste permitting team to view the remediation activity as creation of a new landfill, rather than a strategy to break pollutant linkages and render land affected by contamination suitable for proposed new use under the Planning Regime. 

Notwithstanding the concerns, VertaseFLI  proceeded with an application for a site-based  (bespoke) waste recovery permit for the permanent  deposit of waste to land, which was successfully  obtained eight months after submission of the  application and confirmation that it had been ‘duly  made’. 

Importantly, the permit application procedure shaped the remediation and re-use strategy in two  key ways: 

• Firstly, the waste permitting regime put significant emphasis on ensuring the permitted activity did not lead to a deterioration of environmental quality relative to baseline conditions (a key requirement to satisfy the legal test for permit surrender).

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Therefore, rather than the derivation of  risk-based remediation/re-use criteria for  contaminants in soil and groundwater, the  remediation criteria for contaminants of  concern were underpinned by background/ baseline conditions to ensure that a net  deterioration in quality could not occur. This  required comprehensive documentation of  the baseline site conditions from previous  site investigation reports and additional site  investigation prior to commencement of the  remediation activity. 

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• Secondly, the permitting regime put  significant emphasis on ensuring ‘pollution  control measures’ (temporary and  permanent) were incorporated into the  works (also a key requirement to satisfy the  legal test for permit surrender). The most  significant of these for the remediation  strategy was the requirement to use of a  minimum 1000mm thick low permeability  engineered geological barrier at the base  of the development platform constructed  from inert engineered clay. The intention  of this geological barrier, from a Regulatory  perspective, was to minimise the downward  migration of contaminants from recovered  wastes into the groundwater beneath the  site. Arguably, this represented a measure  that was unnecessary had a risk-based  approach to the derivation of remediation  criteria been accepted. Furthermore,  construction of this barrier using inert clay  sacrificed valuable void space for the re-use  of site-won recovered materials from the  landfill waste. 

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Importantly, none of the above associated with  the Permitting regime precluded the more typical  Regulatory checks and balances undertaken by the  Local Authority Environmental Health department  and the National House Building Council (NHBC)  to ensure that risks posed by contaminants and  ground gas were adequately addressed by the  remediation measures. The remediation measures  included the on-site treatment of contaminated  soils (source reduction), use of a cover system in  gardens and open spaces (pathway interruption)  and inclusion of ground gas protection measures in  buildings (pathway interruption).

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Furthermore, a Geotechnical Design Report was  produced in accordance with the now withdrawn  HD22/08 guidance on managing geotechnical  risk published by Highways England to ensure  the geotechnical suitability of the development  platform constructed using recovered materials for  its intended purpose of road, infrastructure, and  residential construction.