Flow Monitoring and Its Role in Inflow and Infiltration (I&I) Studies (Part 1)

In the first three installments of the Flow Monitoring Webinar Series, Civica discussed the various ways to make existing flow monitoring systems better, through available technology and improved data quality. Now, part four of this five-part series explores the role flow monitoring plays in inflow and infiltration (I&I) studies. An overview of the webinar will be provided in two parts.

What Is Inflow and Infiltration (I&I)?

Inflow and Infiltration (I&I) refers to extraneous flow in a sanitary sewer from rain/snowmelt and groundwater.

There are many reasons why municipalities would want to measure and reduce I&I, specifically because measuring I&I from rainfall or snowmelt can help reduce instances of flooding. In addition, I&I reduction can assist environmental protection by reducing combined sewer overflows (CSOs), sanitary sewer overflows (SSOs), and bypassing at treatment plants.

There are also various ministry documents and new CLI-ECA regulations that pertain to I&I, so it’s important to be compliant with all regulations.

I&I and wet weather flow studies can also be time-consuming and costly. If infrastructure constantly needs to be upgraded to accommodate new developments or growth, there is a large driver to reduce these flows.

Civica’s Inflow & Infiltration Programs

At Civica, there are three I&I programs offered:

• New Subdivision I&I Prevention: This is a relatively new program across Ontario. It encompasses standards and guidelines development, flow and rainfall monitoring, and conformance reporting. Preventing I&I from new subdivisions is a key first step.

• I&I Reduction: This refers to existing infrastructure. Through monitoring, assessment and testing, evaluation and remediation of defects, and stakeholder communication and engagement, municipalities can identify areas where there is a lot of I&I getting into the system.

• I&I Acceptance and Mitigation: This refers to solutions to accommodate the flow, and includes factors such as hydraulic and hydrologic modelling, solution alternatives development, and design and construction. Cost-effective reduction is a preferred method before upsizing pipes and pumping stations is considered.

How to Utilize Flow and Rainfall Monitoring to Assess the Systems from an I&I Perspective

There are some key input to assess systems from an I&I perspective, which include rainfall analysis and climate forecasts.

Rainfall Analysis

The first step is to analyze rainfall and characterize it based on other data that have been collected. An Intensity-Duration-Frequency (IDF) curve describes the relationship between rainfall intensity, rainfall duration, and the return period (probability of exceedance). Data is analyzed for each site where there is a rain gauge.

Typically, rainfall analysis involves more than one rain gauge and can have a fairly large geographic area that is covered with rain gauge networks. In this case, it is a good idea to plot the data and IDF analysis in such a way that the data from across the region is displayed.

Another analysis tool that is used is distributed rainfall modelling (interpolation) to understand what happens between rain gauges. In addition, municipalities can leverage radar data to calibrate what happened at a location where there wasn’t a rain gauge and then use that same information to understand how much rainfall fell at those locations.

Climate Forecasts

Many of the above-mentioned techniques involve analyzing what occurred in the past. With climate forecasting, it’s about looking forward to what is going to happen in a given area.

There are various climate forecasts available, which include:

• GEM-LAM: Global Environmental Multiscale – Local Area Model (a model data updated every six hours)
• NAM: North American Mesoscale Forecast System
• HRRR: High-Resolution Rapid Refresh 
• RAP: Rapid Refresh 

Why Choose Civica?

Civica is a leader in municipal wastewater management solutions and water flow monitoring systems. Stay tuned for part two of the webinar recap, which will take a deeper look into flow analysis. For more information on flow and rainfall monitoring, please contact Civica today. 

Learn more at: 

Flow Monitoring and Its Role in Inflow and Infiltration (I&I) (Part 2)

Methodology of Sanitary Maintenance Hole Inflow and Infiltration

Inflow and Infiltration Inspection Case Studies

New Subdivision Flow Monitoring to Assess Performance of I/I Prevention

About CLI-ECA Regulations

5 Key Takeaways from the CLI-ECA Stormwater Regulations