I&I Mitigation Program: How to Build One That Cuts Wet-Weather Overflows
An I&I mitigation program has two jobs. One is keeping water out of the system. The other is making sure the pipe has enough open capacity to carry what still gets in. Most programs only plan for the first. In-Pipe works on the second, and this post shows where each fits.
Find Where I&I Enters
This part is repair work, and it belongs to your engineers and contractors. You need to know which sub-basins to target before anything else.
Flow monitoring by sub-basin in the wet season, matched to rain gauge data
Smoke and dye testing to find direct stormwater connections
CCTV and manhole inspection to find cracked pipe, failed joints, and leaking structures
If you're asking how to find I&I in sewers, let flow data pick the sub-basins and let inspection find the defects inside them.
Rank Sub-Basins by Wet-Weather Response
Compare each sub-basin's wet-weather peak against its dry-weather flow. The basins that jump the most go first.
Then add a second column from your CCTV: how much of the pipe is already lost to grease and biofilm. A basin with heavy I&I and heavy buildup is losing capacity from both ends. That's where wet-weather overflows happen first.
Match the Fix to the Source
Two different problems need two different fixes:
Water getting in: disconnect direct inflow, rehabilitate manholes, line or repair failed pipe, and set policy for private-side laterals. This is the repair side.
Pipe capacity lost to grease and biofilm: this is the side In-Pipe's FOG treatment covers. Bacteria are dosed near the source of the grease and break it down before it builds into deposits, which keeps more of the pipe open.
Treatment doesn't remove a gallon of I&I. What bioaugmentation can and can't do for I&I lays out the limits in plain terms.
Prove It With Flow Data
Monitor the same sub-basins after the work and compare against storms of similar size. A basin that looks better after a light rain has proven nothing.
Track both sides. Rainfall-matched flow data shows whether repairs cut the water. CCTV before and after shows whether buildup has dropped in the treated segments. Take both to council and to your regulator. In-Pipe doesn't have a published I&I case study, so measure the capacity effect in your own system instead of assuming it.
Where In-Pipe Fits, and Where It Doesn't
Use In-Pipe on segments that show grease or biofilm on camera and sit in basins that surcharge in wet weather. Don't use it on segments where the problem is cracked pipe with clean walls. That's a repair job, and the physical side of I&I solutions is where to start.
Find the Capacity You're Losing in Wet Weather
If your ranked sub-basin list includes segments with a grease history, that's worth a look before the next storm season. Talk to In-Pipe about where FOG is eating capacity in your I&I problem areas and what treatment would add to your program.
Related reading: I&I Reduction in Your Sewer Collection System
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