Richard Morrish is a Chartered Landscape Architect and arboricultural consultant, and for 20 years has run his own consultancy in Norfolk. He previously worked in local authority and for consultancy practices in the UK, Hong Kong and Australia. He is concerned that, although there is growing debate about improving management of agricultural soils, management of soils on development sites remains poor.
This is a particular example, made worse by heavy rain, but just this month in our small parish I could list dozens of compacted arable fields standing water whilst adjacent ditches stand dry, areas of substantial soil erosion and trashed tracks and verges. And runoff from land here is only a few hours away from the Wash – in theory one of the most heavily protected wetlands in Europe.
I am no agronomist – but a thorough review of when and how we crop, cultivate, use rotation and ley crops to nurture and safeguard our soil substrates must be long overdue. Apart from winter harvested root crops, biomass maize and outdoor pigs are two other Norfolk ‘crops’ that seem synonymous with soil compaction, localised flooding and soil erosion. There is clearly an urgent need to re-evaluate what is ‘sustainable produce’. Soil conservation, carbon sequestration and minimising costly adverse impacts, both on and off site, must appear on the balance sheet.
Soil on Construction Sites
The theme coming through on the SSA website and wider reporting is that there is growing pressure to change agricultural policy. But I am seeing no improvement in how soils are managed on construction sites.
During the planning process there is little or no mechanism for quantifying the existing soil resource on a prospective building site. Site allocations by planners may consider the agricultural value of land, but in my experience, this is seldom a deal-breaker. Landscape character, settlement continuity and infrastructure provision are all given much more weight in planning processes.
When analysis of a prospective development site commences, ecological surveys include pages of reference to designated sites and habitats that could be affected in the locality; they wax lyrical about the possible presence of bats or newts or water voles. They seldom even mention site soils – even though soils are typically the building block of all site ecology.
Engineers view soils solely as a building material, only really concerned with their bearing strength, drainage capabilities and whether they harbour any contaminants. Architects similarly have little interest in soils beyond the engineer’s advice for foundation design.
Arboricultural consultants are given some power to influence soil management on construction sites through BS 5837(2012) – Trees in relation to design, demolition and construction. A requirement to follow this standard is regularly used as a planning condition. As well as conserving soils within the root protection area of trees, the document recommends soil analysis prior to works and remediation of compacted soils at completion. However, typically arboricultural consultants are not employed to analyse soils or monitor site works and monitoring/enforcement by LPA officers is nowadays unusual.
One might think that Landscape Architects would have the influence to protect soils during construction and to ensure a healthy, functioning soil at project completion – and in my practice I can assure you that we try! My landscape specifications always contain proposals for soil stripping, soil storage, ground amelioration after construction and preparation of planting areas. However, we are seldom employed to monitor site works or visit site after planning consent is granted. Without a planning condition we have no power to enforce good soil management by building contractors. Defra’s Construction Code of Practice for the Sustainable Use of Soils on Construction Sites (2009) is a useful document that I do promote – but I’m in no position to enforce it. I vouch that few building contractors have heard of it.
Soil protection or soil management requirements are seldom included in planning conditions. Where Construction and Environmental Management Plans (CEMPs) are required, these tend to focus on mitigation of contamination (air quality, water bodies, noise, dust) and less so on soils. The great majority of small and medium scale developments do not require CEMPs as a planning requirement.
A re-evaluation of ‘Sustainable Development’
My experience on the vast majority of construction sites is that soil management consists of heaping all excavated material (vegetation, topsoils and subsoils alike) into large mounds, often several metres high. The ‘stockpiles’ are moved several times during the construction process, compacted by heavy machines and contaminated with building waste.
At completion of construction works they are then re-spread, generally over highly compacted substrate and mixed with building waste, leaving a poorly draining, de-natured substrate that will at best take many years to rectify. This is a crass waste of one of the most valuable materials on any site.
By factoring in healthy soils as an essential foundation for ecosystem services and protecting them for their own value, they could immediately become an important asset on every development site. Their value as an existing carbon store and future carbon sequestering habitat could become an important aspect of achieving carbon-neutral development. There would be immediate and obvious benefits for biodiversity, flood prevention, groundwater attenuation and, in residential development, future garden establishment and food production. Where soil retention was not required on a site – planning legislation that gave value to healthy, well structured, clean topsoil would hopefully enable it to become a more viable material to trade and transport elsewhere – rather than just dumped as ‘spoil’. Aftercare and remediation of soil (just like the carrot field) is critical when soil damage is inevitable.
The definition of ‘sustainable development’ is frequently opaque. Part of a future definition should surely include attaining carbon neutrality – and soil conservation could be a key aspect of this.
Four ideas to assist better soil management on construction sites:
1. Local Plans and Neighbourhood Plans should include specific policies that identify conservation of soils and good soil management on construction sites as a key element of sustainable development. A more specific policy on soil conservation may be needed in the National Planning Policy Framework (NPPF).
2. Standard planning conditions need to include requirements for appropriate soil management on construction sites – as they now typically include conditions for tree protection and provision of landscape design. Planning officers need training so as to recognise the value of soil management in attaining sustainable development.
3. Ecologists need to highlight the value of soils as a basic component of biodiversity on the majority of development sites. Ecologists, Arboriculturists and Landscape Architects, as the ‘environmental’ element of most construction teams, need to show a united front in championing soil protection and soil remediation on building sites. However, this will be greatly facilitated by the enforcement element of a planning condition.
4. In the context of shrinking local authority budgets and reduced staffing levels, it will be essential that developer teams are to some extent ‘self-policing’. This might be facilitated by planning conditions that require monitoring reports to be submitted to the LPA indicating that required stages and standards for soil management have been met.