Gauge-adjusted radar rainfall (GARR) is a powerful tool that combines rain gauge and radar data to produce high-quality, spatially distributed rainfall data used in I/I studies and hydraulic modeling. This webinar will provide an overview of GARR and discuss how to apply it. Planning considerations will be provided, as well as practical considerations needed for successful implementation and maximum benefit.

The key objective of an I/I study is establishing the relationship between the rainfall and the I/I that it generates; often called the Q vs i relationship. Each basin has its own relationship that varies with Winter and Summer seasons as well as with Wet Years and Dry Years. This relationship not only is an answer in I/I studies, but it is also a Key Performance Indicator (KPI) of how the work was conducted. We will discuss how the Q vs. i plot can be used to spot storms that were affected by snowmelt, high winds, base infiltration, restricted pipes, and sanitary sewer overflows (SSOs). Rainfall measurement is mathematically just as important as flow measurement, and rainfall measurement continues to be the greatest source of error/variation of results. We will discuss Control Basins and how they can overcome the vagaries of rainfall in assessing Pre- and Post-rehabilitation success.

The success of a rainfall-dependent inflow and infiltration (RDII) project strongly depends on project planning and execution. This webinar will define the several steps necessary to produce a useful analysis that can determine where RDII is originating and the severity of RDII throughout the study area. Key items to consider include, basin size, determining sewershed boundaries, Gross and Net RDII hydrographs and precompensation of base infiltration. We will discuss the 14 historical methods for quantifying and normalizing RDII values and recommended method(s) for normalizing RDII. Will also discuss the use of Seasons and the number of storms to be included in a study.

To understand the wet weather performance of your sewers, you first have to understand how they perform during dry weather conditions. This webinar will define a “dry day” in the context of I/I studies and show how to extract this information from study data. Key performance indicators (KPIs) include minimum, average, and maximum dry weather flow rates, as well as estimates of wastewater production and groundwater infiltration. Four methods of estimating groundwater infiltration will be discussed, including the % Minimum Method, the Wastewater Production Method, the Stevens-Schutzbach Method, and the Mitchell Method. Once KPIs are obtained, they can be used to benchmark performance against a variety of sewer design guidelines.