Inflow and infiltration refers to rainwater and groundwater that enters the sanitary sewer. A certain amount of I&I is unavoidable and is accounted for in routine sewer design. However, when I&I exceeds design allowances, sewer capacity is consumed and may result in overflows, risks to health, damage to the environment and increased conveyance costs.

CRD Inflow & Infiltration Program

The CRD’s Inflow and Infiltration (I&I) Program was created in the early 1990’s as part of the CRD’s Core Area Liquid Waste Management Plan (LWMP).

The purpose of the program is to reduce the amount of rainwater and groundwater entering the sanitary sewer system when it is cost-effective to do so. Reduction of I&I in the system lowers the risk of sanitary sewer overflows and can decrease the costs of conveying and treating wastewater.

The LWMP mandates a joint responsibility between the municipalities and the CRD in reducing sanitary sewer I&I.

Problems Caused by Inflow and Infiltration

  • Overflows back up into homes and businesses, damaging personal belongings, which can result in costly cleanup.
  • Overflows spill into roads, creeks and beaches, which can harm the environment and pose a health hazard to residents as well as marine and wildlife.
  • I&I increases wastewater pumping and treatment volumes, resulting in increased operational costs.
  • I&I consumes valuable sewage capacity, resulting in potential costly upgrades to the system.
  • I&I is associated with sewer deterioration, which can lead to pipe collapses and sinkholes.

Sanitary Sewer Maintenance Responsibilities

Sewer service laterals are sewer pipes that connect a building’s plumbing to the municipal sewer system. Homeowners are responsible for maintaining sewer service laterals within their private property. Municipalities are responsible for maintaining sewers and sewer laterals on public right of ways.

Maintenance Responsibilities in Oak Bay

Homeowners within Oak Bay are responsible for maintaining the entire sewer service lateral.

Homeowners Can Reduce I&I from their Property

  1. Check that gutters and outside drains are not connected to the sewer system. Contact the municipality to find out how to connect drains to the dedicated storm drainage system.
  2. Avoid planting trees and shrubs over sewer laterals. The roots can damage the structure of the sewer lateral and cause leaks.
  3. Ensure that basement drains are not connected to the sanitary sewer and install a sump pump to the drainage system instead.
  4. Replace any known broken, leaky or problem sections of sewer that are located on your property.

Note: Regulations are being considered within the CRD to promote I&I reduction on private property.

I&I Video Series:Understanding Inflow and Infiltration

I&I Video Series: Sources of I&I

I&I Resources