Water Infiltration Into Crawl Spaces on Fill Material 1

[monisajack]

A subdivision project has several houses with significant accumulation of water under the crawl spaces as soon as the house is completed. Virtually every situation involves construction on fill material with the bottom of the footing on original soil. What could be the problem?

 

[JedClampett]

I think you need to give more information. Do you live in a rainy area? Is there high groundwater? Is the water potable or sewage or something else? Was the crawl space wet during construction or only after the house was complete?

 

[monisajack]

No, it is not in a rainy area. This site is not in a flood prone or high groundwater area. The water is not from a sewer system. The site was dry prior to constructing the houses with the moisture appearing after the foundation was excavated. The street directly in front of the house has no apparent signs of water related problems.

 

[JedClampett]

I'm no expert, but I can think of two causes. Either the subdivision changed the drainage of the area such that water is ending up in these crawl spaces or the fill is drawing moisture from the soil due to capillary action.

 

[fndn]

Crawl Space area is near the ground surface and so are abandoned field tiles. Have they chopped off any or all of the tiles at the Earthmoving stage? Also check to see that storm sewers are not leaking. By the way, is there a retention pond close to these homes where the high water table is near bottom of footing grade. Please provide any additional information that you have noticed.

 

[bashabo]

I would suggest you to look into the soil investigation (geotech) report of the project area. That might tell you something what is underlying the site and a probable cause of water accumulation. Most likely it is capillary fringe.

 

[Wooten]

Off hand it sounds like trapped runoff. Is the crawl space elevation lower than the surrounding yard elevations. Are gutters and downspouts installed along the roof perimeter? If so, where do the downspouts daylight?

 

[reddog99o]

I agree with all of the responses so far. My best quess is capillary rise, but if the groundwater table was insignificant then you could rule that out. However, if the excavation for the footers was dry, it doesn't mean that the water table wasn't just below the dry line. Heavy construction equipment with associated with vibrations could have caused "perching" of the water table. Check the Site Report as otherwise advised. Check for signs of any flow. If there are none, you can almost bet on capillary "perching"

R.A. Hassett, P.E.
rah1616@hotmail.com