0001 Reason for amendment is to change the quantity from each to lbs. The total requested it 1425 lbs. Surge stone for a wastewater trickling filter. Trickling filters have historically used crushed stone or slag as media, and surge stone is a suitable type of crushed stone for this application. However, the effectiveness of stone media, including surge stone, depends on specific characteristics like size, void space, and surface area. Considerations for using surge stone in a trickling filter Size and uniformity: The rocks must be a uniform size, typically 3 inches in diameter, to create sufficient void space for ventilation. If the stones are not uniform, smaller pieces can fill the gaps and reduce the flow of air and wastewater, leading to clogging and poor treatment.