Life cycle assessment (LCA) and life cycle costing (LCC) of road drainage systems for sustainability evaluation: quantifying the contribution of different life cycle phases

Previous Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) studies on urban drainage systems only included construction materials in the system inventories. The present study aims to suggest an LCA and LCC method that for the first time, considers the inventories from four main phases in the life cycle impact assessment, including extraction of aggregates and production of construction blocks, transportation, construction, civil work and finally maintenance and end-of-life. LCA and LCC were carried out for 10 drainage systems including filter drains, infiltration trenches, soakaways, permeable pavement, infiltration basin, wetland, retention ponds, swales, filter strip, kerb and gully. Results showed that normalisation of environmental impacts and costs to drainage system size (length or area) was more appropriate for drainage systems with higher flow rate capacities (e.g., kerb and gully). However, drainage systems with low flow rate capacities that were designed to store runoff, required normalisation of environmental impacts and costs to storage capacity. The environmental impacts associated with urban drainage systems that needed considerable amounts of virgin aggregates (e.g., filter drains) were higher than those with limited construction material (e.g., swales). Transportation of materials and construction civil works had a larger contribution in life cycle inventories and associated environmental impacts in drainage systems with higher demand for materials. The lowest environmental impacts and life cycle costing were from swales, wetland and retention pond. Uncertainty assessment revealed that drainage systems with extensive application of materials and civil work had more negative impacts on human health, ecosystems and resources.