Inflow & InfiltrationAdvanced 32 min read

Inflow & Infiltration: Advanced Quantification, Cost-Benefit Analysis & Sanitary Sewer Evaluation Surveys

Advanced-tier I&I study methodology for Class 4 operators: basin metering and flow isolation to pinpoint sources, full flow-data component analysis, cost-benefit comparison of rehabilitation versus capacity expansion, and the structured Sanitary Sewer Evaluation Survey (SSES) process.

A Class 4 operator is expected to do more than recognize I&I or even quantify it at the basin level — they are expected to be able to design and interpret a full I&I study, weigh rehabilitation against capacity expansion in real dollar terms, and understand the structured survey process utilities use to move from "we have an I&I problem" to a funded, prioritized construction program. This guide covers that advanced-tier methodology.

Full I&I Study Methodology: Isolating the Problem

A system-wide flow monitor at the treatment plant tells you that you have I&I. It does not tell you where. A full I&I study drills down through progressively smaller pieces of the collection system to isolate the actual source areas.

Basin Metering and Sub-Basin Ranking

The collection system is divided into monitoring basins — typically drainage areas bounded by trunk sewers or major interceptor

Read the full guide

Create a free account to unlock the complete guide — every concept explained in depth, worked examples, and cited sources — plus practice exams and an AI tutor scoped to your license.

Create free account Sign in

Free to start · no card required