under slab erosion

[sjvicker]

What's everyone's thoughts on how I should handle this erosion situation?

We had our patio slab poured last year and this winter we've received a record amount of rain in the Seattle area. The blue line in the photo represents where I would like to continue building a retaining wall and the red line is where I'm starting to get washout. This is worse where the blue and red lines intersect. I want to eventually do more permanent steps from the lower slab (not shown) to the upper one just to the left of the retaining wall (blue line).

I was thinking about putting in a concrete retaining wall about 2' off of the slab then compacting dirt between the two until its at the same height as the slab but drainage will still be an issue.

Thanks,
Spencer

 

[isb cornbinder]

A contractor was doing some slab leveling next door. He used urea formaldehyde expanding foam to lift and fill under the slab. This is another idea to consider, maybe.

 

[Falcon67]

We have a corner of the house that is below a valley in the roof that channels a lot of water during a rain due to the large "fetch" in that part of the roof. It comes off like a water fall. I used a lot of gravel in that area where the water impacts the ground. No problems with erosion. You could either do a ditch maybe 6~12" wide by 6" deep with gravel, or go with a French drain setup - buried pipe punched with holes buried in a gravel bed and channeled "elsewhere".