The Challenge
The whole site is covered by root protection zones and this informs every element of the project and programme. Traditional construction techniques are not permitted; excavations can only take place using an air spade and heavy plant has to be avoided.
The two new structures – the education centre and gardeners’ hut/WC’s – use steel micro screw piles to float above the ground, thus minimising soil compaction and preventing root damage by not loading the area above protected roots. Traditional pipe-based irrigation systems have also been avoided. Detailed air-spade surveys have been undertaken to map the full extent of tree roots, and our team are in constant close liaison with Westminster’s tree officer to ensure we comply with their arboricultural and ecological planning condition requirements. It has been essential during the tender process to ensure everyone fully understands the constraints and how these can be overcome, and our team has been integral to this process.
Over 7,000 people inputted into the public consultation, and many of the prominent residents who adjoin the square are also contributing towards the project financially. Sensitive stakeholder engagement is therefore key, including with third parties such as the Royal Marsden Hospital who recently used the space for a high-profile charity event whilst air-spade work was ongoing.
Sequencing is also impacted by the nesting session, by significant site access limitations, and by ensuring the supply of such a large quantity of bulbs at the right moment.
The Outcome
Upon completion, the redesign will drive a Biodiversity Net Gain of 15.5%, with a 5 fold increase in the number of plant species and 24 more trees increasing habitats for wildlife and improving air quality and access to nature in the West End. We are currently exploring methods including shock waving and soil-quaking to de-compact the soil whilst avoiding traditional digging methods.
In line with its sustainability commitments Grosvenor will deliver and operate the scheme as carbon neutral from day one. Through a highly sustainable design and management plan, embodied and operational carbon will be minimised, with any remaining emissions offset through verified schemes. Factoring in the significant increase in planting and revitalised soils, additional carbon will also be removed and stored within the square, helping reduce Mayfair’s climate footprint in the long term.