collecting nuisance water underground and connecting to storm drain

[babbaum]

I have a question for the experts out there. I am trying to come up with some options for collecting nuisance water that has been percolating upward under a road and causing pavement distress. A couple of investigations have been conducted that identify the source of the nuisance water as shallow groundwater coming up under hydrostatic pressure.

There is a stormdrain below this nuisance area that the director would like to connect to as a means for diverting this shallow groundwater. Some of the ideas being discussed include installing some drain pipes a couple feet below the surface over the area of nuisance and connecting those pipes to small underground basin. The water would collect there and then be directed to the storm drain my means of a larger pipe.

My questions are this:

Not being a hydrology expert, I need to get a sense if this is a reasonable solution in concept. It seems that way to me, but I don't know how to model the groundwater and size the pipes accordingly.

First, is this reasonable?
Second, can someone point me to some good resources for learning how to model the volume and flow of groundwater in this area and then size the pipes and underground basin properly?

This is a learning experience for me, so any help is greatly appreciated. Forgive my ignorance of hydrologic principles in the process.

Thanks so much,

Matt
babbaum@yahoo.com

 

[beej67]

Where's the project? I'm assuming the water table doesn't inundate your storm drain system regularly. If you're in Florida or someplace similar, and you're dealing with a wet storm drain that bubbles up, totally different ballgame.

Assuming you're not coastal..

If you've got enough room and enough fall, dig a cutoff ditch upgradient from the road and tie the ditch into the stormdrain system somehow - headwall or ditch bottom inlet or whatever makes the most sense with your site. Dig the invert of the ditch a foot or two lower than the subgrade of the road.

If a ditch isn't an option, then you could do a french drain.

I'm not sure I'd worry too much about modeling it, unless required to by a municipality. Others more familiar with subsurface hydrogeology may disagree, but I've never really trusted subsurface geologic models to be accurate unless they're extremely detailed, and I doubt you have money for a model like that in your budget. Just build your french drain lower than you think you need to.

One slick idea might be to perforate your existing storm drain pipes somehow, to use them as a surrogate french drain. I have no idea how you'd construct that, but it's a neat concept. Midget with a power drill?

Over in Japan they sometimes tie entire porous pavement road sections in with subsurface drain stone, which ties into the stone backfill for their storm drain systems, which are perforated pipe. They push all the runoff into the ground water for stormwater management reasons, as a regional way to improve water quality and reduce flooding. I've read some fascinating studies on it, but we might not be able to have as much success with it over here because of soils and much worse road maintenance practices than they have.



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