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70% Infiltration in a Sanitary Sewer! Impossible! Step by Step Confirmation of Outrageous Infiltration Values

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When a total R-value of 0.7 was reported for a major flow basin in an I/I study in the City of Columbus, it raised some eyebrows. A total R value of 0.70 meant that 70% of the rain water falling on the basin was making its way into the sewer system. Most shockingly, the sewer had only a very small section of combined sewer; it was almost entirely a separate sanitary sewer! When these extremely high values were calculated from the flow monitoring data, everybody was skeptical. Questions were asked. Were the flow monitors calibrated accurately? Was flow crossing boundaries? Were the computer programs making the correct calculations? Was there some other hidden error? This paper documents the step-by-step process used to trackdown and confirm this number.

Keywords: Flow Monitoring; Infiltration; Inflow; R value; Rainfall; Sanitary Sewer

Document Type: Research Article


Publication date: 2009-01-01

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