12. Continuous Backwater This scattergraph displays data obtained during dry weather from a flow monitor installed in a 27-in sewer just upstream from a 12-in Parshall flume. By design, the flume causes the upstream sewer to operate under continuous backwater conditions. This flume is no longer used for flow measurement. […]
Yearly Archives: 2018
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11. Backwater and Surcharge Orifice The scattergraph show here reveals the presence of a dead dog and a downstream restriction that cause backwater and surcharge conditions. However, note that flow rate increases from 6.9 MGD to nearly 9.2 MGD as the flow depth increases during surcharge conditions. This phenomenon is […]
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. […]
09. Surcharge Surcharge conditions are common in sewer systems, especially during wet weather event. The flow monitoring data shown here indicate that this sewer operates as expected up to its rated capacity of 20.8 MGD. This value is shown using an iso-Q. Although surcharge conditions are common, it is uncommon […]
08. Debris Amusement The scattergraph depicted here reveals shifting debris that reduces the pipe capacity at this monitoring location. The iso-Qs depict the average daily minimum and maximum flow rates. As the debris accumulates, the same daily flow rates are carried under deeper and slower conditions. The Manning Equation is […]
07. Iso-Q Lines The relationship between flow depth and velocity is important to understanding the hydraulic conditions in a sewer. The addition of flow rates to a scattergraph deepens the operational understanding of these conditions. Flow rates can be scaled within a scattergraph and displayed using iso-Q lines. Simply put, […]