Erith Park will replace the former high-rise Larner Road Estate constructed in the 1970’s. The site occupies an abandoned clay quarry. The quarry was partially backfilled with random fill during the 1970’s that was proven to contain significant contamination.
Clarkebond were appointed as civil, structural and ground engineering design engineers for the development under a design-and-build contract.
The site investigation revealed significant contamination in fill that was placed to reprofile about 30% of the site area in the 1970’s. This presented a potential risk to the underlying chalk aquifer. Through close consultation with the Environment Agency and detailed quantitative risk assessment we were able to establish a series of protocols for adoption in the construction to enable development without the requirement for extensive site remediation.
The legacy of the former clay quarry resulted in highly varied topography and a level difference of 13m across the site presenting a particular challenge to the required high-density development comprising medium rise apartments and a high proportion of house units. Reprofiling of the site to facilitate the development involved moving 70,000m3 of earth. An earthworks balance was achieved utilising all granular demolition arisings and no contaminated soil was removed from site.
The topography complicated the requirement to replace an equivalent residential floor area to the former high-rise development, and to achieve compliance to the London Housing Design Guide Lifetime Homes and Code for Sustainable Homes Level 4. Much of the new development was also required for disabled occupancy, and all site areas were required to allow for disabled access. The site being a bowl shape also presented particular drainage challenge to provide protection for all dwellings against flooding from a potential off-site overland flow exceedance event.
Clarkebond were able to address all constraints to achieve the objectives of the development and code compliance. The structural design and drainage were designed to provide fully effective protection of the underlying chalk aquifer from potential contamination pathways. Apartment blocks extended to 7-storeys accommodating a variety of unit sizes and were designed to allow for conventional concrete frame construction with little or no recourse to transfer structures, providing a significant cost advantage assisting viability of the essentially public and affordable housing development.