A comprehensive Soil Resource Survey carried out for the Royal Horticultural Society by soil scientists at Tim O’Hare Associates (TOHA)for the proposed RHS Garden Bridgewater will provide an exemplar case study on the sustainable re-use and management of existing soils.
The proposed new garden – on the site of the former Worsley New Hall in Salford, to the north west of Manchester – has been designed by landscape designer Tom Stuart-Smith. Soils on the 63 ha site, which slopes down to the Bridgewater Canal on its southern boundary, range from a sandy loam, through alluvial silts and clays in the woodland areas, to peaty soils in the meadows abutting the canal.
TOHA Principal Consultant Tim O’Hare and Senior Associate Ceri Spears carried out a baseline assessment of all soils found on the site in November 2016, in advance of the commencement of construction of the planned visitor centre,with a view to their re-use for the new garden. The survey will also help to refine decisions made on the final landscape design and planting schemes provided outline planning permission is granted.
“This is an intriguing project that has the potential to act as an exemplar for future schemes where insitu soils, if correctly managed, can be re-used to their full potential” explained Tim O’Hare. “The range of soils within the four main areas of the site will need to be treated differently. Some of the sandy clay loams are very delicate and susceptible to compaction, for example. A good soil management strategy should be developed to ensure these soils are protected throughout the different phases of the garden’s construction.”
The diversity of in situ soils – a result of topography, hydrology and past land use - is a bonus for the development of the RHS’s new garden. An old boating lake on the site, which is heavily silted up, will be restored and the hope is that the infertile dredgings will be used to create perennial meadows. Areas of existing grazing land that will accommodate the planned visitor centre and car park have soils that will be ideal for planting in the site’s original walled garden where the existing soil is poor.
Tim O’Hare believes RHS Garden Bridgewater is a perfect opportunity to demonstrate how in situ soils can be effectively re-used to provide the right materials for a range of landscape applications. The creation of a detailed Soil Resource Plan, which gives guidance on soil stripping, storage, spreading, amelioration, and handling during landscape construction, has been recommended as the next step in the project’s soil strategy.