Thursday, August 31, 2023

Unpacking the Two-Pass Solution in InfoSewer

 Unpacking the Two-Pass Solution in InfoSewer

InfoSewer's dual-pass methodology is a cornerstone for achieving a meticulous and comprehensive analysis of sewer system performance. The two distinct passes each offer a layer of insight into various facets of the system, particularly focusing on the depth-to-diameter ratio (d/D) and the Hydraulic Grade Line (HGL).

Phase 1: Laying the Groundwork with Manhole Loads and Link Flows

The first pass serves as the initial survey, setting the stage for the entire simulation. During this phase, InfoSewer calculates the loads for each manhole and estimates the flow dynamics in the links connecting them.

  • Key Output: The primary yield from this stage is the initial d/D values, which are often used for preliminary mapping.
  • Primary Focus: At this juncture, the main attention is given to calculating manhole loads and estimating link flows.
  • Use-case: This is especially useful for generating an initial hydraulic snapshot of the sewer network, which can be invaluable for early-stage planning and decision-making.

Phase 2: Advancing the Analysis with Backwater, Surcharge, and Pressure

The second pass builds upon the foundational data gathered in the first. This phase engages in a more nuanced analysis by incorporating calculations for backwater effects, surcharge conditions, and intra-system pressure.

  • Key Output: The adjusted d/D values and the HGL emerge as the critical outputs from this phase.
  • Primary Focus: The emphasis here is on advanced hydraulic modeling, including backwater estimation, surcharge analysis, and pressure calculations.
  • Use-case: The second pass is vital for risk assessments, emergency response planning, and other high-stakes decision-making processes.

Interplay Between the Two Phases

The two passes are not isolated events but rather interdependent processes that feed into each other. The second pass takes the first-pass data as a baseline but refines it to account for the more intricate hydraulic phenomena, often resulting in higher adjusted d/D values.

Why Adjusted d/D Matters

The adjusted d/D, born out of the second pass, usually exceeds the initial d/D computed during the first pass. This variation is not arbitrary but indicative of the complex hydraulic factors like backwater effects and surcharging that were considered in the second pass. As such, the adjusted d/D serves as a more reliable and nuanced metric for assessing system performance and associated risks.


This expanded perspective offers a multi-dimensional view of the Two-Pass Solution in InfoSewer, shedding light on its nuances, capabilities, and the significance of each stage in contributing to a robust and reliable sewer system model.

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