How to deal with springs?

[brnt]

We are rough grading a large commercial site and have encountered some underground springs--water is bubbling up to the surface. The original ground in these areas was holding water and it was a slough. The contractor pumped the standing water and began removing the saturated ground with the intention of padding in dry clay. There is about 5 feet of fill to be placed in this area which will eventually be a parking lot. When dealing with a spring is it better to try to place a seal of clay over top or would it be better to place a french drain of some sort to drain the water away?

Thanks

 

[Ron]

I would go with underdrain. Clay is difficult to work with, particularly when wet.

 

[msquared48]

The water will eventually win if you overlay it with clay. It's just a matter of time. Create a drain system and drain it to a landscape pond that would work into the landscape plan. Make a lemon into a peach...

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[MiketheEngineer]

As mentioned - drain it

 

[oldestguy]

Not so fast with the drains. Sure that may carry off obvious water flows, but the muddy site will be difficult to place any fill on to any degree of compaction.

In my experience it is sometimes necessary to come in with coarse broken rock, in this area called 3" clear. It may take over 12- 18" to get a stable place to work on. The open gradation of the stuff allows mud to squeeze in there and eventually a stable area will result. Then at that time, I'd look for some type of drain system, properly graded. That 3" clear stuff, with mud in-the voids won't work as the drain. Keep in mind filter requirements if you want it to be a permanent fix.

 

[fattdad]

before you dug, there was saturated soil at these depths. It wasn't mud, it was wet soil.

I'd of hoped that the preliminary engineering for the project would have disclosed the position of the water table at the excavation grade. I'd of hoped that the contract documents would have address dewatering requirements. As it stands, the contractor's means and methods have taken otherwise stable (but wet) soil and reduced it to mud.

I'd never even remotely consider undercut and replacement with dry clay. That's just plumb hollow!

Depending on the required strength for the subgrade, I'd consider a drainage blanket consisting of filter fabric and #57 aggregate. Outfall drain is up to you. I mean do you really need to perminently lower the water table after the project is completed and to what extent could that affect the stresses in neighboring property? don't know. . .

f-d

¡papá gordo ain’t no madre flaca!

 

[brnt]

A differant firm did the geo-technical analysis of the site. They drilled 15 bore holes and the water table was 9 feet down. They drilled in early April and in this location--close to a creek--the water table fluctuates with the seasons.Nobody realized there was a spring --most thought the pond was runoff--until they began removing the saturated soil. The spring, where the water comes to the surface, is an area with a 10ft radius.

We ended up digging a trench, placing washed rock--then perforated pipe--then washed rock all rwrapped up in filter fabric. We drained it to a retention pond on the site. It seems to be working--water is running into the pond and the ground above the drain is solid.

 

[chicopee]

One thing about wet soils, it will craze the asphalt pavement and ultimately the pavement will brake apart with weather conditions.