10. Backwater and Surcharge

Most surcharge conditions result from downstream restrictions that reduce sewer capacity.  The flow monitoring data shown here indicate that this sewer operates as expected up to a flow depth of approximately 11 inches.  However, backwater conditions are observed above this point and result in surcharge conditions.  The impact on sewer capacity is readily identified using iso-Qs, presented here as a percent of the estimated sewer capacity determined by the Lanfear-Coll Method.  This downstream restriction results in a capacity loss of 50%.