Review of the Dalzell Estate Project: Use of Soils and Recycled Materials

Transcription

1 Review of the Dalzell Estate Project: Use of Soils and Recycled Materials Dr David Hackett March 2012

2 Step 1: Resource Audit Site audit should take in the quantity and quality of soils and subsoils present: There is more biodiversity within soils than on them soil biodiversity is usually overlooked. The nature and depth of soils and subsoils largely determine the natural drainage characteristics (important in SuDS and landscape management) and the vegetation that can be supported Soils and subsoils can be used in, for instance, the creation of footpaths when mixed with recycled scalpings or in retaining structures when combined with a binding material (e.g., in rammed earth structures). Soils are the power houses for the recycling of carbon and nitrogen. Need to work with soil fertility, such as in low-maintenance wildflower meadows, coppice etc in higher fertility soils.

3 Soil biodiversity threat map

4 Step 2: Recognise inherent values Minuaria verna (Spring sandwort) on lead spoil, Peak District National Park Lichens and broyphytes on shale, Bolton

5 Step 3: Audit Findings Should Inform Design Kokedra, Kyoto, Japan working with the environment

6 Step 4: Amend, Improve, Enhance and Create Work with the materials at hand Strip, relocate, amend and enhance soils Generate soils as required from subsoils Be informed and be inventive

7 Soil Naturally Occurring and Made What is soil? Oxford English Dictionary: the upper layer of earth in which plants grow, a black or dark brown material typically consisting of organic remains, clay and rock particles Naturally occurring v Made soils Naturally occurring soils: highly variable, biologically active media, developed through interaction of environmental and biogenic process on exposed geology. More biodiversity in soils than on them. Twice as much carbon in soils than in the atmosphere. An ecosystem and resource to be conserved. Made soils: growing media which replicate qualities of naturally occurring soils in supporting plant growth

8 Geological Reference The underlying geology has a fundamental influence on the soils generated and the nature of the vegetation supported.

9 Consider Made Soils Made soils : the characteristics Soils constructed from recycled and site-won materials Replicates qualities of natural topsoils in supporting plant growth Specifically tailored to end use Soils which haven t been stripped from greenfield sites Made soils : the benefits Enhanced biodiversity Soils suit specific end uses Sustainable re-use of materials including OGM Reduced carbon footprint of development Reduced development costs to client Reduced ongoing maintenance costs

10 What s not in a made soil? Contaminants above a certain level: Soil Guideline Values (SGVs) : trigger levels of contaminants for all soils. Constantly updated by Environment Agency against current scientific understanding. Contaminated Land Exposure Assessment (CLEA) : sets out current SGVs. Available from Environment Agency website. Contaminants include: PAHs (incomplete combustion of organic materials and oil products, including bitumen) Metals such as lead Sharps (broken glass, sharp metal) Plastic Unsuitable micro-organisms (Salmonella and E. Coli) All contaminants are accepted below a certain level Some elements necessary in low volumes for plant growth become contaminants at higher levels (eg manganese and zinc)

11 Why make/enhance soils?: degradation and loss Parliamentary Office of Science and Technology, UK SOIL DEGRADATION July 2006: Soil degradation involves both the physical loss (erosion) and the reduction in quality of topsoil associated with nutrient decline and contamination. It has implications for the urban environment, pollution and flooding, through loss of storage capacity, soil-sealing etc. In 2006, 2.2 million tonnes of topsoil was being eroded annually in the UK and over 17% of arable land showed signs of erosion. 20% of all upland peat is currently at risk. Initially prevent loss then increase capacity

12 Made soils + biodiversity Growth can be tailored to planting mix Chorley testing showed made soils outperforming naturally-occurring soils Creating soils more closely related to indigenous flora + fauna Allows focus on local objectives: eg Lancashire Biodiversity Action Plan habitats + species

13 Landscape uses

14 Landscape options

15 Codes of Practice

16 Supporting documentation