Collecting nuisance water and diverting 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

 

[cvg]

what you are describing is a spring and a spring box. Alternatively might be called a french drain or a sub drain or a weeping tile. you can search the forums and find numerous posts describing how to construct the drain.

if this is really a groundwater spring than you will need a permit to dewater. This "collection system" would be considered a well. You may want to confirm this is not a leaking pipe, pond or swimming pool.

Modeling groundwater is a specialty and if you really want to model it, get a hydrogeologist to do it for you. You can read up on it with the "Ground Water Manual", by USBR.

http://search.barnesandnoble.com/Gr...9781410221964/?itm=1&USRI=ground+water+manual

 

[beej67]

What state is this? You may not need a special water use or dewatering permit, depending on where you're at.

Is there enough fall between the side of the road and the invert of the storm system to where you could put a cut off ditch in the right of way, instead of a french drain? If so, that'd be a more reliable solution that'd be easier to maintain. Dig the ditch to an invert a foot or two lower than the road subgrade, and direct the ditch to a ditch-bottom inlet or a headwall that ties into the existing storm drain system.

I echo hiring a hydrogeologist specialist to do a groundwater model if you think it's necessary, but depending on the solution, it may not be. Those guys do some pretty complicated modeling, and it isn't cheap. You'll need additional geotechnical survey too.



Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[babbaum]

Thank you to both of you for your time and valuable input. I am in California. According to the assessments that were done, this was considered groundwater coming up under hydrostatic pressure. The soils were mostly fine grained below the base material.

As far as the dewatering scenario is concerned and requiring a permit with our water board...does it matter if it is a stable water table that is fluctuating with seasons vs. groundwater that is coming up under hydrostatic pressure? or is groundwater, groundwater? my initial feeling on the matter is that we would require some kind of permit with water board. would this require compliance monitoring with testing? would we have to treat the groundwater before putting it in storm drain?

as far as the location of the distress and subgrade buildup of water...it appears to be happening closer to the median of the road. the storm drain is about 15 feet deep...so whatever we do, we would have to tie into something deep. i wanted to explore the concept of this cutoff ditch. does this seem feasible in our situation?

thanks again for your assistance and advice.

 

[cvg]

You say the base soils are "fine grained". I would not expect a lot of groundwater to emanate from fine grained soils. Maybe you mean fine sand?

in california, I can almost guarantee you will need a permit to collect groundwater in a pipe. Discharge of anything in California to the drainage system is subject to NPDES requirements. You might want to review the regulations before deciding what to do.

 

[oldestguy]

Keep in mind this general concept. It is much more effective to do draining job if you catch the water before it reaches the problem area than to try to have it drain my gravity to some collection system. The side ditch thing is a good cut-off system at some sites, per beej67 above.

In California I'd contact your State DOT geotechnical division and ask them about their horizontal drain specs and contractors that do it. They have perfected this system quite well. But, remember that is a way of asking water to drain by gravity,not cutting it off ahead of the site, so it has difficulties doing a good job.

 

[brandoncdg]

Is the road a city road or state highway? That will make a huge difference on top of the issue.

Civil Development Group, LLC
Los Angeles Civil Engineering specializing in Hillside Grading

http://www.civildevelopmentgroup.com

http://www.civildevelopmentgroup.com/blog

 

[babbaum]

Thanks again to everyone for the input.

The project would be on a city road.

 

[greenone]

I work in California-it is possible to get a dewatering system permitted to discharge into a storm system. You will have to submit a permit application with design details, and a PE will have to take day-to-day responsibility for its operation. Your regional water board should have the application docs on its website.

Ongoing monitoring will depend on what the area is like, and what your first round of sampling shows. Treatment will depend on the results-I have a site that needs to treat for VOCs, even though the site is not the source of the VOC contamination, because the pump system pulls it in from off-site. We are required to sample monthly and report quarterly.

 

[roncity]

Is the ground water seepage associated with rainfall or does it occur in dry seasons?
Did the appearance of the ground water coincide with any other construction work in the area ?
Look for evidence of utility trench backfill settling. If the water is seeping up over the storm drain trench, it’s possible that the pipe bedding – or the trench backfill – is already acting line a French drain and caring water from a long way off . …from other utility projects ( new water lines ) or from older active lines that are leaking. …or even older lines that have been abandoned. Or undocumented landscape irrigation systems