Efficient rainwater drainage presents challenges, particularly for ancient urban areas with drainage systems that have surpassed their intended lifespan. Overhauling these infrastructural systems incurs high costs in terms of material and ongoing maintenance. The 'city sponge' paradigm offers a sustainable alternative, facilitating water retention and purification while reducing costs. This approach repurposes the retained water to promote vegetation growth, enhance air quality, and diminish noise pollution. This research introduces a novel sponge infrastructure, termed 'rain-garden bands,' designed for rapid and uniform water absorption from road surfaces. The study investigates various layers' water retention capacities and filtration rates within filtration columns. This was achieved by administering a predetermined volume of used oil, recording the duration required for the oil to traverse a set height sample, and subsequently measuring the water and oil volumes post-leakage at the column base. The findings indicate a notable duration exceeding 26 days for oil to traverse a 300-mm sand layer and substantially reduce volume leakage.
