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Source/Receiver Methodology

To understand the process of identifying potential I & I sites, FloCis has developed a concept that considers the characteristics of the clear water drainage system and potential entry points into either sanitary mains, manholes or service laterals.  This clear water “source” can drain into sanitary pipes – the “receivers”, through an “interface” such as direct connect pipes or soils that surround sanitary structures. Thus the name, “Source, Interface, Receiver”, or Source/Receiver for short. Identifying a source’s origins and ground water flow patterns determined by the watershed, storm collection system, and where it is being received within a sanitary collection system will enhance the investigation process and allows the utility to separate these two flows.

Source waters, precipitation or snow melts, can reach the receiver asset by percolating through interface soils from a variety of sources: storm water systems, temporary ponding, or directly from gutters, sump pumps or foundation drains.   As these water sources find a path of least resistance, the interface will begin to react to the intrusion.   These sources often make their way through the watershed unseen but their presence will begin to manifest as they flow to the trenches where sanitary structures are buried.

Receivers of direct or watershed flows are assets in a sanitary sewer system that were never designed to resist clear water intrusion. Also, improper connections or cracked pipes in a sanitary system are common receivers of unintended flows.   Areas where storm and sanitary assets are in close proximity of each other are often prime places of intrusion.  These are more specifically described as piping, parallel-runs, cross-overs, and cross-unders.   During wet weather, as receivers pass the excess flow through the sanitary system, the wet weather loading can contribute to SSOs, I &I, and added stress to a treatment plant.

Over time, as physical evidence begins to indicate infrastructure problems, within either the sanitary or storm systems, the initiation of a preventive maintenance program is crucial.  The Source/Receiver concept combined with asset inspections can help determine what areas of a system require immediate attention, as well as then developing a schedule for proactive maintenance.   Repairs can be prioritized to ensure that cost-effective decisions are made to prevent more severe problems from occurring.  It has been shown that preventative maintenance is less expensive than reactive maintenance. 

 FloCis has developed tools that measure, analyze and view flow patterns within an infrastructure, documenting a system’s behavior that are indicators of ground water intrusion.   These tools utilize the Source/Receiver concept to locate potential I&I sites so that the entire sanitary collection system does not require the same level of inspection. Working with these tools will allow decision-makers to:


These are steps that should be implemented to help ensure flow efficiency, address deterioration and mitigate I & I. Knowing the conditions that contribute to how a collection system behaves supports a preventative maintenance program needed to achieve long-term asset sustainability.