Dynamic Hydraulic Model Calibration of Storm Recession Tail Runoff Hydrographs Using Soil Conservation Service Data and InfoWorks ICM

Wastewater flows generally include three major components: base wastewater flow (BWF), groundwater infiltration (GWI), and rainfall-dependent inflow and infiltration (RDI&I). This article describes how the near-term recession tail portion of RDI&I was generated by matching California Soil Conservation Service data with appropriate infiltration module parameters within the dynamic hydraulic modeling software InfoWorks ICM. The process yielded a more defensible groundwater saturation starting point in the model, flexibility in modeling from any groundwater saturation state, and provided the basis for a detailed wet weather calibration and long term simulations for the Napa Sanitation District as part of a 2019-2020 collection system master plan completed by GHD.