Shortlisted for Best Sustainable Re-Use of Materials
A brief history
Paragon Park is located on the former Courtaulds factory site, close to the City Centre in Coventry.
The 15 hectare site had a history of contamination through a multitude of previous uses including a scrap metal works, an industrial park, a factory, and associated brickworks.
As such the made ground was impacted with Asbestos Containing Materials, Total Petroleum Hydrocarbons and other deleterious materials associated with the former uses. Areas of perched water within the alluvial soils were also contaminated with Light Non-Aqueous Phase Liquids.
The presence of six underground storage units (USTs), large areas of reinforced concrete hard standing, as well as several stands of mature Japanese Knotweed.
The area had been earmarked for regeneration for many years however planning permission was only granted for development in 2015.
The land was acquired by the client, Persimmon Homes Plc for a development including 450 homes, a park, employment zone and canalside features, without any adverse effects to the neighboring community and businesses.
An adjacent metal recycling facility therefore posed a visual and acoustic concern to the developer. Part of the Persimmon Homes planning approval required that the overall site be raised, whilst a 450m long and colossal 9.5m high visual & acoustic bund wall to act as a barrier to separate homes from the neighboring metal recycling facility had to be constructed.
With insufficient site won fill available, Dunton were required to import no less than 80,000 cubic meters of material that satisfied the geotechnical criteria of the geotechnical engineers, Geo-man Ltd. With a fundamental part of the assignment to balance the sustainability credentials with the commercial viability requirements set for the project. Dunton set to work applying all three of their business units.
Dunton considered numerous designs, finally settling on a geogrid reinforced slope with a 70 degree external face angle and a 1 in 2 internal face angle. The bund was to be constructed from imported waste soil arisings from local construction projects. By their nature, these arisings were inconsistent mixes of soil classifications. The geo-technical design criteria required Class 2A/2C cohesive material, stoney cohesive material with a Phi = 30º angle of internal friction. Interestingly, the geo-grid solution realized a reduction of 58% of CO2e versus a conventional solution using selected granular material Class6I/6J for the bund.
Dunton went even further to propose that the formation layer consisting of compacted waste soils would satisfy the bearing the requirements of the bund and geo-technical requirements of the development as a whole. Meaning a further 47,000 cubic meters of waste material could be imported as fill from these local sources.
Environmental Agency permission was sought to obtain SR2010 No.12 and SR2008 No 27 permits to treat waste and produce soil, soil substitutes and aggregate on the site using mobile a treatment plant.
The entire project consisted of a complex scope of works that required the management of in-situ remediation and enabling works, whilst strictly managing the logistics of the imported fill from numerous construction
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projects in the local area. Careful monitoring of all receipts, required, separate stockpiling, testing, batching, specific treatment, screening and further stockpiling post treatment.
Each incoming consignment necessitated determination and classification of the waste to regulate whether the material was suitable to be accepted onto site for treatment under the Environmental Agency guidelines.
Yet the biggest challenge with the operation was ensuring material was geotechnically suitable for the construction of the bund and formation; this required Dunton to ensure the correct treatment process was implemented, whether this was screening to remove oversize material or blending to create the ideal material for the construction.
Blending of post treatment soils, was required to ensure correct sizing and distribution of particles, to meet the rigorous testing regime set by the engineers. These tests comprised particle size distribution and shearbox tests. Once the fill had been placed and compacted it had to further pass nuclear density and plate bearing tests to a minimum CBR (California Bearing Ratio) of 15%, and 95% of Standard Proctor density with a maximum moisture content of 10%.
The import and treatment of soils arising from the local construction sector was managed in accordance with Definition of Waste Code of Practice and an environmental permit that promoted the sustainable use of waste soils. Site specific hazard and environmental risk management ensured that reusable soils did not pose a threat to the environment for future users of the site.
Paragon Park was a project where Engineering, Social values and Sustainability met.
98% of the waste received was re-directed from landfill and re-used within a remediated brownfield site.
With the local authorities wishing to protect local businesses and the community. A developer as inspired to enhance the community as it was to ensure sufficient return for their substantial risk.
Dunton successfully managed to design and deliver an engineered solution that married the motivations of all the stakeholders; Social values, Sustainability and reward for the client.
Whilst it is practically impossible to calculate the exact total carbon savings; Conservative estimates are that over 12100 Heavy Goods Vehicle (18% of UK vehicle Green House Gas emissions) loads were removed from what would have been the traditional accepted imported fill practice cycle (avg 10 miles). Thus, a minimum Co2 emissions saving of approximately 1313 tCO2e was realised.
As with any brownfield development, we could further conceive that 15 hectares of Greenbelt carbon sinks were spared or at the least development delayed through the determination of all the stakeholders, to re-use a brownfield site.