The Water Environment Research Foundation sponsored a project to investigate the affect of various wastewater characteristics on primary clarifier performance and to quantify the variability of these characteristics. Eight public agencies participated in the study by collecting performance data around a designated test primary clarifier. Three of the agencies studied two test clarifiers. The data presented and analyzed here were collected at the Edmonds, Washington, Wastewater Treatment Plant. The paper describes a new paradigm for evaluating primary clarifier performance, which is confirmed using the Edmonds data. Edmonds tested two clarifier configurations: (1) a square tank with a circular sludge collection mechanism (a so called “squircle” configuration) and (2) a rectangular tank with two circular sludge collection mechanisms. The data collected are inconclusive in regards to which configuration performed better.