First off, I am a Nuke/Electrical Engineer, so plese forgive my ignorance here!

The project in question is a gravity block wall system to be constructed on a slope of about 1:1.  Total elevation from the bottom of the first (lowest) wall to the top of the highest is about 22 feet.  I plan on building four walls to terrace about 50 feet of hillside (front to back) to improve accessibility and increase the yard area at the top.  Distance across the project is about 55 feet from the stairway to the gully wall opposite


  Here are some photos:


The walls will be built so the first (lowest ) wall top will be even with the small landing in the center of the first photo.  The top of the highest wall will be level with the blue spruce tree.

Note that this is an arid climate with total annual rainfall of about 10 inches.

The slope is solid fractured basalt rock with a combination of natural overburden and artificial fill as a result of construction of the house about 30 years ago.  Fill is mostly pit-run basalt (2-4 inch size)

The contractor is going to dig a shallow trench for the first course of block (80-pound segmental blocks)and seat them in compacted 3/8 gravel.  

My question is this:  How much distance from the toe of the wall to daylight downslope is necessary?

The contractor has assured me he (and his Engineer) really know what they are doing . . . however, I always like an impartial second opinion.

 

crstrode,

I am not sure about your question.  But, if the contractors engineer had completed the stability assessment and design of the walls, then it may be best to discuss your questions with them.  The distance from the toe of the wall or slope to the retaining wall depends on site and soil conditions.  Loading the bank with soil may be questionable at some locations, but not all.  Sliding (etc.) should have been looked at by contractors engineer.  What is the results from the engineers study and design details?

regards

From the photos, it looks like fairly stable conditions exist. I note the house is close to the banks as well. Toe erosion is probably not an issue. In such a case, the wall can be as close to the edge of the river bank as practicable. However, as noted by cdh61, additional information is required if we are to provide meaningful suggestions.  I would venture a guess of 2-3 m minimum setback of the wall.

What method did you use to fix photos with your submission. Let us know   

I appreciate the responses to date.

The photos are easy to attach.  Merely precede the web address of the photgraph with a left bracket "[" and the letters IMG, then close with a right bracket "]".

There are instructions to do this at the bottom of the screen when you push the PREVIEW POST button

You should ask for a copy of the "engineers" calcs and details for both the wall design and the overall global stability of the slope.  These calcs should be stamped and signed by a registered engineer.  You may even need this to get a building permit (you did get a permit didn't you?) If he can't produce these, don't start construction.

Once you get the cals, a second engineer could very quickly review these and determine if the standards of care have been followed.

current terraced wall status:

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