Northfleet Embankment East is part of the Northfleet and Swanscombe regeneration area adjacent to the River Thames. With its proximity to Gravesend and Dartford and key transport links, this 14 ha site is prime land for mixed-use development. In preparation for this, the site required raising by up to 3.5m for flood protection to provide a suitable platform for future development.
Working on behalf of the Homes and Communities Agency (HCA), Hydrock's objective was to create an engineered platform for future development which would be suitable for a variety of land uses, including industrial, commercial and residential.
Our flood risk assessment determined both the level the land should be raised to and the volume of fill required. The size and scale of this work meant planning permission for the works was required. Hydrock and the HCA liaised closely with all the regulators and stakeholders and this process helped us to identify the two areas of prime concern: the impact of a huge number of lorry movements on the local road network; and the potential to introduce contaminants to the site due to the amount of fill required.
With these concerns in mind, we prepared the land raising contract documents and handled the tender assessment process. BAM Nuttall was appointed who, alongside the HCA and ourselves, engineered an innovative approach to re-use 250,000m³ of processed chalk arisings from the construction of the nearby Lee Tunnel. The arisings were transported to the site by river, eliminating the impact on the local highways.
The importation of processed chalk by river significantly reduced the impact on the local road network, cutting the kilometres travelled by road from an estimated 175,000km to less than 29,000km. In total, the delivery of materials by river enabled a 98% reduction in carbon emissions compared to importation by road.
Processed chalk arisings are not a standard earthworks material, so it was essential to carry out comprehensive compaction trials to demonstrate the geotechnical suitability of materials to form a competent development platform. In addition, the works were governed by a Code of Construction Practice and a detailed Construction Environmental Management Plan.
The works were completed with minimal impact to the environment and in a sensitive manner, which has also preserved the archaeological remains relating to the Rosherville Gardens, which formed part of the site in the 19th century.