I/I: Finding the Culprit
Previously, we explored the causes of inflow & infiltration (I/I) in sanitary sewer pipes, and the significant negative impact it has on those collection systems. This time, we take a look at how we arrived at this point, and how sources of I/I can be detected.
We’ve already discussed the fact that America’s crumbling infrastructure is a main cause of the presence of I/I. It’s just one of the reasons that municipalities have been eagerly waiting to see President Trump’s promised infrastructure revitalization plan. Until that is forthcoming, however, city managers, public works officials and water management agencies will need to continue battling the I/I demon as they have been. Before they can do that, they must first determine the presence of I/I in their systems; and when it’s found, where it’s coming from.
There are two major ways that I/I is discovered in municipal collection systems. One usually leads to the other.
Smaller municipalities usually discover the presence of major I/I sources while inspecting or repairing an area of their system that’s already ailing. There may be a cave-in or sinkhole, a blockage causing a backup, or even an SSO already in progress. At that point, crews are dispatched to locate the source of the problem. Often that source is I/I from a major influx point.
Larger cities and many utility agencies with adequate budget and personnel resources will try to get out ahead of such reactionary response. They conduct regularly scheduled, full evaluations of their sanitary collection elements with a Sewer System Evaluation Survey (SSES). This activity includes:
- Flow monitoring
- Physical survey: Smoke testing, dyed water testing
- Pre-cleaning internal pipe CCTV inspection
- Removal of Infiltration and Inflow sources
- Post-cleaning internal CCTV inspection
A Main Contributor
A huge contributor to the renegade I/I flows in most municipalities is illicit connections to the city sewer system from residential properties. Most homeowner-generated I/I is found during the physical survey portion of the SSES. This includes roof drains tied into the service line, improperly connected sump pumps, and other illegal connections.
Many times, homeowners make such connections without knowing they’re breaking the law. Of course, there are others who are aware of the prohibition against tying in to city sewer without a permit. After all, the ability to save tens of thousands of dollars that would be spent in proper connection is powerful incentive. Nevertheless, when such illicit connections are found, the city usually issues an order to disconnect. The homeowner is given a limited period of time to correct the situation, or face stiff fines.
The Cost on the Ground
Municipalities across the country face increasing I/I issues with smaller budgets to attack them. Most are raising utility rates to help cover the burgeoning cost of repairing and replacing aging sanitary sewer lines most vulnerable to the deterioration that invites I/I.
Some municipalities have started a one-cent sales tax or greater on all purchases. This is earmarked to help pay for infrastructure rehabilitation projects. Based on news coverage over the past several years, it seems more cities are taking a similar tack in their efforts to tackle the I/I issue without bankrupting their coffers.
Here at TrioVision, we offer help for those efforts. Our AssetDMS is the most comprehensive PACP certified software package available to help you track, capture and analyze your I/I issues. This pro-level package provides the capability of assessing not just sewer main lines, but also the health and I/I issues that may be originating from laterals and manholes.
In our fourth and last post in this series, we’ll survey the way several American cities are handling the I/I issue inside of larger infrastructure renewal programs.