Inflow and Infiltration Investigation

Introduction

The Town of Grimsby is currently completing a Sanitary Sewer Inflow and Infiltration (I&I) Study that aims to identify, quantify and provide solutions to remediate sources of inflow and infiltration into the wastewater system within pre-defined areas in the Town.

Why is the Town conducting an I&I Study?

In previous years the Town of Grimsby completed a town-wide study of its wastewater system, and three specific areas were identified as contributing a significant amount of storm water to the wastewater system. The study we're doing now is to further investigate these three areas to determine where the stormwater is coming from.

To help reduce the combined sewer overflow pollution to the environment, the Town of Grimsby has retained GM BluePlan Engineering (GMBP) to provide services for this study.

There are three high priority areas where this study will take place:

1. Oakes – Extending from North Service Road to the south beyond Main Street West.
2. Lakeside – Lakeside Drive north of the QEW extending from Ontario Street to the west limit of Olive Street.
3. Downtown – St. Andrews, Nelles Boulevard, Murray Street from Main Street West to the CN railway.

Figure 1: High Priority I&I Investigation Areas

Program Objectives

• Preventing sanitary overflows into the natural environment
• Maximize the capacity of sanitary sewers to reduce infrastructure and treatment costs
• Minimize risk of future basement flooding
• Reducing flows being treated at the Wastewater Treatment Plant

What can residents expect?

From April 1^st through to April 19^th, team members from GMBP will be visiting high-priority areas in Town to isolate sources of I&I at the street-level and characterize the type of response from each source.

• The field investigations are completed to gain a better understanding of local drainage conditions, including the interaction between private property drainage and the public drainage system.
• Investigations will be occurring from public and private property, without the need to enter your home.
• The outcomes of the field investigation will inform the development of an I&I reduction strategy.
• As an extension of the town of Grimsby’s I&I investigation, GMBP will also be completing smoke testing of the sanitary sewer system in the high-priority areas of Town.

Background

In 2020, the Town of Grimsby finalized the Baker Road Pollution Prevention and Control Plan (PPCP) with the objective of establishing a Master Servicing Plan (MSP) to support the community's growth while meeting the Ministry of Environment Conservation and Parks (MECP) goals of the F-5-5 Procedure to reduce combined sewer overflow pollution to the environment. The PPCP and MSP assessed both the existing and future state system performance to determine the nature, cause, and extent of issues, reviewed alternative solutions, and recommended a capital plan for the Town.

Subsequently, an I&I Reduction Study was completed in 2021 with the purpose of creating a remediation plan that included flow monitoring analysis and recommended field investigation. The findings of this study provides specific details and recommendations which form the foundation of this current study.

The goal of the current study is to address the recommendations of the PPCP and subsequent Tactical I & I Study and conduct an Inflow and Infiltration study that will take a public-private approach with multiple methods of investigation including suggested approaches by the consultant, closed circuit television (CCTV) sewer inspection data review, smoke and dye testing, desktop assessment of existing and historical information, and curbside drainage surveys in order to meet the Baker Rd. PPCP reduction targets.

Full CCTV inspection of all mainline sewers, sanitary laterals and manholes were recently completed in the I&I target areas and this data has been made available to GM BluePlan.

Table 1: Sanitary Sewer Assets in High Priority Areas

How does stormwater and groundwater enter the sanitary sewer network?

What are the investigation techniques used to locate the unwanted I&I?

• Study Area Background Review
• Resident Survey
• Sewer Flow Monitoring
• Infrastructure Condition Assessment
• Study Area Drainage Survey
• Catch Basin Dye Testing
• Sewer Smoke Testing

What is smoke testing?

• Smoke testing consists of blowing smoke into the sewers and canvassing the area above ground to document locations where smoke is observed (e.g. from catch basins). The smoke used in the test has no odour, is not harmful to your health, and will disappear within a few minutes.
• The test will be performed as a first step to identify the connection points for roof downspouts, catch basins, and other water inlets (e.g. to the sanitary sewer or storm sewer).