High Pressure Active Water Leak due to Groundwater in Concrete Sump Pit 1

[x5bulldog]

I have a underground precast concrete sump pit that is actively leaking at a(horizontal)construction joint. The leak is due to the groundwater penetrating the joint.

The leak is located about 10 feet below grade, in the corner of the wall, at the joint. Due to the high groundwater table, the water penetrating the corner of the wall is not slowing down any time soon. This is not the first attempt to stop the leak. The 1st repair took place several months ago. The typical waterstop method provided by the precast vendor at the construction joint did not hold. Leaks were occurring in several spots around the perimeter of the joint. The initial attempt to fix the leaks, a Xypex product was utilized. The repair took place when there were minor active leaks. It is possible the installation of the Xypex product was not properly installed or the concrete surfaces were not prepped correctly at the joint, in the corner of the wall. Now, since we are in the rainy season and the groundwater table is high, the water pressure seeping through is high. We do not have access to the exterior of the wall and able to dig our way down to the location of the leak. Our repair will have to come from the inside of the sump pit. The sump pit is not in operation, so it is empty and we have access to the interior.

Does anyone have recommendations on how to approach this?

 

[TehMightyEngineer]

We use a similar system (Waterplug Hydraulic Repair Mortar) for leaking crack or joint repairs in our precast, but they're thankfully rare enough that they've always held. But I don't believe we've faced as much hydraulic pressure as it sounds like you have. I suspect a hydraulic cement system will not be sufficient if you have substantial flows as even with the rapid set time, it will not bond correctly or at least will be difficult to properly repair.

Still, hydraulic cement would have been my first choice as it's easier than other repair methods and generally works well enough for most situations. I'd suggest removing the Xypex repair mortar, locate the construction joint, and seal it with an epoxy injection crack repair system. Sealing the joint for the epoxy over the active leak will be difficult but you don't need a perfect seal; just need to contain the pressure of the epoxy so it's driven into the crack. Place ports over the crack, seal it up per the systems recommendation, inject epoxy, and cure sufficiently. As long as your sealant holds the water pressure will actually help drive your epoxy and hold it in the joint. If your system allows it I'd also fill the sump pit with water to prevent pressure differentials as it cures. Remove the sealant (or leave in place) and check for leakage but as long as the repairs properly done this should hold.

If they have a leak this badly at a construction joint I bet good money the precaster accidentally omitted a butyl rubber seal between the pours at this joint. They should definitely cover the cost of this repair.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[JedClampett]

There's a lot of ways to do this half a$$ed, but I think you know that. Bless those Xypex guys, always willing to suggest their product, and always willing to tell you why this application wasn't really the right way to use it.

I think TME is on the right track. Since you can't get to the wet side, I would drill holes at 45 degrees to intercept the joint and epoxy inject as if your life depends on it. If there's a way to temporarily dewater the area using well points or lateral pipes (it doesn't sound promising) that would sure help.
It's easy to say now, but this was not a good application for precast. Cast in place concrete with waterstops in the joints would of had a much better chance of working. But the hundreds of dollars saved will go far in repairing this .

 

[TehMightyEngineer]

It's easy to say now, but this was not a good application for precast. Cast in place concrete with waterstops in the joints would of had a much better chance of working. But the hundreds of dollars saved will go far in repairing this.

As a (biased) engineer for a precaster, I object to this blanket statement. There are plenty of times where precast doesn't make sense but simply saying that precast concrete can't make a proper joint equal to cast-in-place is ridiculous. We regularly are required to do water leak tests of our precast structures and the only times we've seen leaks like this is if we made a fabrication or installation error. Barring such obvious installation errors, a horizontal construction joint in a 10'+ deep sump structure should be easily sealed with standard butyl rubber joint sealant.

And I highly doubt it's hundreds of dollars, depending on the system and application precast buried structures could save thousands and outlast cast-in-place.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[BridgeSmith]

For what you describe, I would recommend a hydrophilic chemical grout, applied either by injection or soaking oakum in the resin and packing into the joint. As long as it doesn't dry out (it shrinks when dries out), it should provide a permanent seal.
Injecting long life

 

[oldestguy]

It's not my job, but the recommendation for Oakum packing makes sense. Then, if you wish to do more, such as injecting via drilled holes or a small pipe through the packing, you will have a better chance for success.

 

[BridgeSmith]

If you're trying to plug a leak where there is significant head pressure from the opposite side, the oakum gives the resin an anchor point so that it doesn't wash out before it has a chance to expand as a foam into the gap. It will slow the flow and break it up enough that when you inject more of the gel or foam behind the leaking area, it has time to activate and expand to stop the leak completely.

It react similarly to Gorilla Glue, but on a larger scale and more quickly.

 

[x5bulldog]

Thanks for the help on how to approach this.

Does anyone have past experience with injections of polyurethane foam? Drill & Penetrate the wall through the interior, below the horizontal joint and then inject foam to create a curtain barrier. The foam when injected and reaches the exterior, it work it way up and seals off the leaking area.

 

[Spartan5]

Does anyone have past experience with injections of polyurethane foam? Drill & Penetrate the wall through the interior, below the horizontal joint and then inject foam to create a curtain barrier. The foam when injected and reaches the exterior, it work it way up and seals off the leaking area.

That's a relatively common way of rehabilitating sanitary sewer manholes to eliminate infiltration.

https://www.waterworld.com/articles...urethane-grouting-to-reduce-infiltration.html

 

[BridgeSmith]

Good article Spartan5.

x5bulldog, once you choose a supplier, you should be able to get any other specifics you need from them. (likely you could get specifics from any of the suppliers as a potential customer, as well)