The Challenge
The client required 5,000 tonnes of topsoil for new residential allotments at their new housing development. The existing nutrient values of soils were determined as ‘sub-optimal’ and required improvement to enable plant growth without exporting unsuitable material and subsequently importing new topsoil material to replace it.
Our Solution
Target nutrient value ranges were identified based on existing threshold values within the British Standard for Topsoil (BS3882) and agreed with the Project Landscape Architect. The following works were thereafter successfully carried out in full accordance with CL:AIRE Code of Practice:
• Samples of site soils to be modified were obtained from site and sent for comprehensive physical/chemical analysis to verify nutrient and constituent components compared to the specification;
• Bench-scale trials then completed in-house by a Soilfix Engineer, modifying site soils using varying proportions/blends of spent mushroom compost – a sustainable, nutrient rich amendment for improving soils, with the resulting blends sent for chemical analysis;
• An optimum blend ratio of mushroom compost vs site soils was identified which balanced nutrient improvement and cost drivers; and,
• Full-scale implementation of the topsoil improvement using the optimal blend ratio was carried out using Soilfix screening plant.
Soilfix successfully completed the soil improvement works with nutrient values within the target ranges, to enable sustainable construction of the residential allotments.
Aside from achieving significant cost savings (~£180K for disposal and re-import) and preventing over 500 HGV movements on/off-site, generating 5,000 tonnes of site-won topsoil will provide a significant long-term carbon sequestration potential for years to come.
