I&I is a major issue that plagues all collection systems. What can be done about it? There are a number of large-scale and costly ways to address it but often these are overwhelming projects to start. So, let’s take a step back and start small with the manholes. A quick review of rain event data will help pinpoint problem areas. There may be numerous issues in a line, but remember we are going for easy manhole infiltration. Start popping manhole covers. We don’t need to look for every minor leak and the large leaks are easy to identify. Obliviously, flowing water is easy to spot but even if a large leak is not active there are normally clear signs of its existence. These signs include staining, native soils being washed in, or joints with bulging ramnecks.
So now, with X number of leaking manholes identified, it is time to set a plan. Inverts and precast joints are often the biggest culprits. Often, they have been previously repaired with hydraulic cement. But hydraulic cement can’t deal with movement, and thus leaking cracks return. While hydraulic cement is cheap, repeating the repair process over and over is very expensive and means more confined space entries. Injecting the joints and inverts with a flexible polyurethane grout will provide a long-term repair, often longer than the expected service life of the manhole. Spetec PUR GT380 is the gold standard for these types of repairs, but at times a hydrophobic grout might be needed and thus Spetec PUR F400 would be the grout of choice.
But what about older brick manholes? Often they are ripped out and replaced. Replacement is not always necessary, can be disruptive, and is very costly. Spetec PUR Highfoamer is an excellent choice for curtain grouting (the ideal application for sealing gushing leaks in old brick manholes). Its set time can easily be field adjusted and its 50x expansion makes it very cost-effective.
So to review...
- Perform a quick review of rain event data to identify potential leaks
- Pop manholes to identify large leaks
- Grout the defects for a long-term fix
The bonus round is to watch treatment costs drop due to less infiltration!
Pro Tip: It is best to waterproof when the leaks are active.