Ground (not surface) water drainage into house

[akay]

Rainy season in Northern CA - ground is saturated. Hillside permeated with gopher tunnels (entire county is like this!!) so water problems are subterranean in origin and surface runoff is not logical (i.e. marked water flow often starts from a hole in the ground!). This house is built into the hillside, where the finished basement floor is 5-6 feet below grade. Supposedly a french drain was installed several years ago, but we don't know where or how deep. Several years ago and again this year (as we speak!) there is water seeping through the concrete wall or floor (the wall is paneled, so I can't tell exactly at what height water is seeping through - paneling is dry to surface touch, but water could run down wall behind it). There does not appear to be significant surface water - I believe most, if not all of this water is coming below grade. What would you recommend to prevent the hillside water (from grade to 6 feet below grade) from seeping into the house? If I need to have a local consult, what sort of expertise should I seek out? Thanks much!

 

[boo1]

Check the following:
Inadequate Grading
Defective or Missing Gutters and Downspouts
Ineffective Drain Tile and Sump Pit
Improper Drainage with Underslab Ducts
Structural Cracks

talk to a few contractors
you may need to hire an engineer

 

[KRSServices]

My first inclination would be to investigate if the sump and drain pipe was even installed by the original contractor. If water is mounding below the gradient from the hillside, then it is a sure bet that the walls (assuming concrete) were not propoerly protected against seepage. How much gravel is below the footings and where would collected water drain to? A Sump? The municipal storm system?

What needs to happen is that an effective catchment/barrier needs to be investigated with the idea of intercepting any mounding water, or water migrating from the hillside. A word of caution, if the hillside is weeping that much water is there a danger of a subsidence or slide? KRS Services

http://www.krs-services.com

 

[pigdog]

akay,
If you get a posthole digger and go up-slope of the house a little ways, you could sink some "wells" down to the basement floor elevation. Get some plastic electrical conduit, or PVC and cut some slots with a hacksaw, every few inches. Cap the bottom of the pipes and stick them in the holes, and if you really want to be fancy backfill with sand. Let it sit a day or so, and check the pipes for water level. If you are seeing standing water in the pipes, that is your static or ground water level and the elevation of the piezometric surface or water table at that point. If the excavation for the house pierced the water table, you are going to have to lower the water table around the house to dry out the house. You will be making a "cone of depression" that includes the house, and possibly affecting the water table for 10's of feet, around the house.

In mines, you can use dewatering wells and pump it down.
Any thing you find, you will have to disclose in a home sale, and, even this level of well is subject to groundwater regulation.
good luck
pigdog