Ask two operators why their sedimentation basin is passing turbid water and you can get two very different diagnoses — unless both of them know how to read the numbers the basin is actually giving them. At the Class C level, sedimentation stops being something you just observe and becomes something you calculate, monitor, and adjust. This guide builds the core process-control toolkit: surface overflow rate, weir loading rate, detention time, and the troubleshooting logic that ties them together.
Surface Overflow Rate (SOR)
Surface overflow rate — sometimes called surface loading rate or surface settling rate — is the single most important control number for a sedimentation basin. It's defined as:
SOR=AQ where Q is the flow through the basin and A is the basin's surface area (the plan-view area, length times width for a rectangular basin, or πr2 for a circu