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Former Littlebrook Power Station, Dartford by WSP 

Shortlisted for Brownfield Awards Category 8: Best Re-use of Materials

Former Littlebrook Power Station, Dartford 

Summary 

Probably the largest land reclamation and commercial development project within the M25 in recent years, the enabling works comprised demolition of three former Power Stations across the 50 Ha site, with recovery and recycling of 99% of demolition arisings,  excavation, crushing and reuse of a large  volume of demolition concrete on site,  retention and reuse of former foundation  arisings and import of over 500,000 m3 of  naturally occurring clay excavation material  from other construction projects across the  South East, for flood mitigation land raising. 

In addition to land raising, material reuse included  creation of a green river corridor as part of the flood  embankment raising works, with integration of habitat  and open space for the local community. The closure of  the Coal Fired Power Station has contributed significantly  to UK Decarbonisation and Net Zero aspirations, and  the enabling phase of the development also focused on  recycling the vast majority of decommissioning materials  and using recycled materials for land raising and flood  defences to further contribute to these significant  environmental benefits. 

Background 

WSP was appointed by Bericote Properties  Ltd to support the enabling works associated  with development of the former Littlebrook  Power Stations in Dartford, for a unique  cross-docked warehouse development with  multiple units in excess of 1 million ft2. Scope  include environmental management of the  decommissioning and demolition process, with  99% for demolition arisings recycled for ruse.  This included recovery and recycling of steel, and  testing, crushing and reuse of brick and concrete  to 6F2 specification in line with WRAP protocols. 

Due to the number of deep basements at site  associated with the former Power Station, up to  20m deep, and a requirement to raise levels by  circa 2 meters to mitigation flood risk, a large  volume of material was required to raise levels.  To ensure this was completed in a sustainable  manner, three Materials Management Plans  were developed across the various development  phases, with significant dialogue with a range  of construction companies generating large  volumes of clay from London and South East  Basement excavations.  

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Demolition of D Station turbine hall with chimneys in the background which were crushed to produce 6F2 for piling mat

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Materials being imported ready for placement and land raising in former A and B Station areas

Land raising in area of former D Station with  concurrent new building construction in background

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To minimise volumes of material leaving site  to satisfy permit surrender and planning  remediation requirements, extensive  supplementary ground investigation was  completed to target volumes excavated and  ensure focused removal. 

Due to the site being developed in phases,  three separate DoWCoP material Management  Plans were developed to support individual  development areas and support verification  reporting across a very large scheme. 

WSP reviewed characterisation assessments  from multiple sites over the three-year  decommissioning, remediation and land raising  process, auditing sites, monitoring transport  and completing quality assurance including  visual monitoring of infilling and sampling and  chemical analysis.

 

Concrete demolition arisings were also crushed  on site under a geotechnical and chemical  specification in general accordance with WRAP  protocols, supporting use as a piling mat after  placement of clay land raise material. 

In addition to monitoring of demolition material  quality during reclamation, quality control and  production of the MMPs, WSP also provided  Qualified Person support by an individual outside  the core project team to allow declaration to be  made to CLAIRE. 

In addition to recycling 80,000 tonnes of steel,  crushing and reuse of concrete demolition  materials and import of 500,000 m3 of  recycled clay from off-site construction projects  (which would have been designated as waste  and possibly landfilled if not beneficially reused),  the large volume of water contained within deep  basements was recovered, treated, and used for  the crushing process and dust suppression on site. 

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A further important element was excavation  and retention of Japanese knotweed impacted  areas on site in a containment cell, outside  the development footprint, in line with JKW  best practice. This again minimised transport  of materials off site and landfill and extensive  monitoring over three years has verified the  success of this element. 

Throughout the programme, Bericote have been  actively involved with community engagement  including school age STEM education activities,  and local young people have visited the site to  witness first hand the sustainable benefits of  materials recovery and reuse.

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Bericote Brief/Project Challenges

 

  • Minimise waste to landfill 

  • Beneficial reuse of material on site wherever possible 

  • Minimise construction traffic leaving site 

  • Use of sustainable construction arisings for  land raising to minimise use of quarried  aggregates 

  • Creation of green space for the local  communities and habitat enhancement  during raising of flood defences via an  enhanced green corridor 

  • Challenges included completing earthworks through two winter seasons  with associated challenges of filling clay  in wet weather conditions and water  management in deep structures 

Our Approach 

 

  • Careful monitoring of decommissioning  and demolition process to ensure produced aggregates are ‘clean’ and fit for use 

  • Working closely with earthworks contractors to identify, characterise, control and allow quality assurance on  imported clay materials 

  • Extensive dialogue with geotechnical  and structural engineers and client’s  development management team to ensure  quality of development platforms, and  design and management of foundation solutions 

  • Careful management of geo-environmental  elements during remediation and land  raising including water quality monitoring  and testing through works 

Outcome 

WSP has  

  • Supported Bericote’s aspirations of  a truly sustainable development enabling  phase, minimising waste, supporting  environmental permit surrender, making  the development ‘future ready against  flood risk and climate change risks 

  • Led on integrating decommissioning,  demolition, ground remediation and land  raising to ensure these elements were  joined up and offered optimal benefits  through synergies 

  • Achieved integration of demolition, remediation and land raising works in  a relatively short programme and space  with construction works rapidly following