Hillside troubles

[MikeT]

Well....my building project has taken a small hit in the process; hopefully it is just a bump in the road, however.  I poured the footings a few weeks ago on my Oregon coast hillside property.  I went down this weekend to get the wall foundation forms started, and I discovered that the recent heavy rains have caused a slide upslope of my footings.  I quickly covered what I could of the hillside and the exposed earth, but with 75 mph winds forecast, part of me feels this might be an exercise in futility--even with as much bracing and weights as I could think of and find.  

So now I am faced with moving dirt off the foundation sifficient to erect the forms and doing it all in a race against more sliding that might just occur.

The upside: if any sliding were to occur between the excavation and the basement/retaining wall being done, I suppose this is the best time-- the footing is poured and the dirt can be "easily" moved.

Just sharin' the fun in rainy Oregon where we have had three days of unrelenting rain.  Hillslides everywhere.

Cheers,
Mike

[glenn kangiser]

There's not much stopping it if it wants to go, Mike.  Now might be a better time to deal with the drainage and hillside problem than to continue putting more into something that may get buried.  I don't know your exact situation.  My mom is in Rose Lodge area and said it has been continuous rain there for a bit.  

It's not pleasant to work in the rain either -- part of the reason I wimped out and went south.

[PEG688]

 



It's not pleasant to work in the rain either -- part of the reason I wimped out and went south.

Coward  
  G/L Mike , I agree with Glenn might be wize to do what ya can with what you've got and wait it out.

 PEG

[glenn kangiser]

 :'(

[MikeT]

I agree that the ground will do what it wants to do, I just want to time the next stage as well as I can so that I don't get caught in a real bad place.  I can deal with the current slides--I just hope the there aren't any more.  Like I said to my wife: this is the penalty we paid for going on vacation this summer instead of getting the excavation done.  Now I am faced with winter (read wet) construction.  If I can just get these walls poured, drainage placed, and properly weatherproofed, I will rest much better.

More as soon as I find out how much more slid over the past two days....

[glenn kangiser]

Just don't do work it may undo.  2 years ago I removed a retaining wall for a customer, put in the year before.  The mud backed up behind it and pushed it about 12 feet to the garage.  It was about 3 feet high and 30 feet long.  Gophers uphill put water into the ground.  A nice drainage cut above the site can help take the water from higher up the hill off to the side and around your work area helping to prevent more instability.

[MikeT]

Tell me more about a drainage cut.  This might be the thing to do to sleep better for the inbetween time when a wall is formed and when it is poured, waterproofed and backfilled.

I do not think I am in much danger of my foundation sliding down the hill.  It was engineered by a good structural engineer who was working off a soils report.  Then to add to the foundation's strength, I put in a keyway under the footing of the retaining wall/basement wall, which is tied to a stepped foundation all the way around.

To give you a sense of the slope/site:
At the top of the property there is a road.  From the edge of the road to place where my excavation starts it is about 15 feet.  Over this 15 feet, the ground slopes about 1 1/2 feet.  Then the excavation is a 14 foot cut.  From the bottom of the cut to the beginning of the foundation is three feet about.  The foundation first is an engineered footing that will support a 10 foot high retaining wall.  The footing is six feet wide with the wall and its #6 rebar starting at 4 feet from the edge.  Just before the rebar is where I put in the keyway.  Then this engineered wall continues around the sides of the Victoria's Cottage perimeter and gets stepped twice.  The lower 12 X 14 room's footing ends up being about 8 feet below the main excavation.

What slid (up till yesterda--I do not know waht happened overnight) was about a unit's worth of dirt.  The optimist in me says that I can move this dirt into the inside of the foundation and this can serve as the lowermost fill before I place the rock, etc for the concrete floor.

I am rambling here, but I would love to get a sense of what a cut at the top of the property might look like.

Thanks much,
Mike

[glenn kangiser]

Always hard to explain by typing.  I'm going from things learned from Mike Oehler's Underground House Book along with other discussion from this site.

12 inches of rain on one square foot of ground = 7.48 gallons  or 1" on 12 square feet is the same.  So 1200 square feet above your excavation - an area 30x40 or 10 x 120 could drain 750 gallons of water into your excavation with a rainfall of 1".  Easy in the PNW.  4" of rain on that area = 3000 gallons.  Any ditch above your excavation to divert the water around your excavation will help.  Your road could improve the situation by taking water away from above the site or if it drains into it, it could make things worse.  Depends on how it is situated.

If the water is moving underground above the site then a French drain could be of use - a ditch filled with gravel and drain pipe at the bottom -- they make socks to slip over the drain pipe also to keep it from getting filled with silt or in some cases to eliminate the gravel.  The purpose here would be to short circuit the water and take it away from your site before it gets into the excavation.  It would drain down and away to a lower level around  one or both sides of the excavation.  Hope this makes sense - hope it is of use.  PNW is due to get another soaking it looks like. :-/