Plant Utilities worked example

Wastewater Surcharge Cost at 72% share of flow above surcharge threshold: a worked example

Suppose share of flow above surcharge threshold falls to 72%. This page works the full calculation at that level so you can see exactly which result moves and by how much. Estimate wastewater surcharge cost from volume, surcharge rate, affected share, and compliance adders.

The inputs for this scenario

  • Metered discharge volume: 650 kgal (held at the documented default)
  • Wastewater surcharge rate: 4.2 $ / kgal (held at the documented default)
  • Share of flow above surcharge threshold: 72 % (the input this scenario stresses; the baseline uses 100)
  • Sampling and compliance adder: 300 $ (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Total wastewater surcharge cost = surcharge volume × wastewater surcharge rate × volume subject to surcharge + sampling and compliance adder.
  • Total wastewater surcharge cost works out to 2,266 $ at these inputs, and this is the headline figure for the scenario.
  • Cost per item or period works out to 3.49 $ / item at these inputs.
  • Variable wastewater surcharge cost works out to 1,966 $ at these inputs.
  • Fixed utility adder works out to 300 $ at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where share of flow above surcharge threshold sits at 100% and the headline result is 3,030 $, this scenario comes in 25.23% below the baseline at 2,266 $.
  • It computes total monthly wastewater surcharge cost as surchargeable volume times the POTW surcharge rate plus a fixed sampling and compliance adder, and breaks out the variable and fixed pieces. When the numbers land here, the stressed input is the lever to work; the walkthrough above shows exactly how much each output recovers as it climbs back toward the baseline.

Results at a glance

  • Total wastewater surcharge cost: 2,266 $ (headline result)
  • Cost per item or period: 3.49 $ / item
  • Variable wastewater surcharge cost: 1,966 $
  • Fixed utility adder: 300 $

Run it with your numbers

  • To rerun this with your own numbers, open the live Wastewater Surcharge Cost calculator, set share of flow above surcharge threshold to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.