Former Littlebrook Power Station, Dartford by WSP
Shortlisted for Brownfield Awards Category 8: Best Re-use of Materials
Former Littlebrook Power Station, Dartford
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.
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.
Demolition of D Station turbine hall with chimneys in the background which were crushed to produce 6F2 for piling mat
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
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.
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.
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
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
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