Approval of Existing Retaining Wall 3

[CANeng11]

A client of ours is renovating their home and in order to get a development permit, the jurisdiction is asking for a "retaining wall disclosure statement" be completed for the existing retaining wall at the front of the house (see pic attached). This disclosure statement is a standard document from the jurisdiction, and it asks you to provide things like the soil parameters used and the factors of safety from design (sliding, overturn, bearing, etc.). The house is 50+ years old, and the retaining wall, we believe, is at least 30 years old - possibly older. I have no idea how I could provide the city with the information required on this statement, without knowing the complete construction. I can see there are 2 tie-back anchors, and I can get the thickness and height. But without knowing information on the footing, the tiebacks, etc., I'm not sure how to proceed.

How would you approach a situation like this? The wall seems to be performing adequately. There are a couple vertical cracks, but the wall has a slight lean backwards.

 

[Aesur]

If I was on the project, I would require a Geotechnical investigation of the soils and a contractor to dig down and verify foundation size, etc. May also need scans to figure out the reinforcing spacing and core drilling to figure out the sizes. Once you had the information you could perform the calculations. It's not an easy or cheap task. Being that this is existing, it seems a little strange to have to do this for an existing structure unless the renovations affect this wall of it wasn't permitted when built, however I am not familiar with your local codes or your project so cannot speculate the reasoning behind needing this, just find it odd.

 

[r13]

The above is the desirable way to handle this situation. But for your own information, you might consider use the presumptive soil pressures in the code to come up an estimate, then decide.

 

[STrctPono]

Are you sure those are tiebacks and not utility cleanouts? Are tieback anchors common in your area for short walls like this? There doesn't seem to be a lot of room from the backface of the wall to the stairs to provide a sufficient tieback embedment. Is it concrete or CMU block with plaster?

You may want to approach it from a perspective of a structural inspection as opposed to figuring out the design parameters and a full analysis (if the city will allow that). Have Engineer check plumbness, hammer sound it, and check for cracks and other signs of distress. If none, then perhaps an assessment report from the structural stating that retaining wall appears to be in good condition with no signs of movement and this being after an assumed 30 years of service.

Everything else you mentioned and Aesur suggested will be very costly.

 

[r13]

Note, the wall seems fully enclosed, if so, the rotation and sliding are out of considerations.

 

[XR250]

Seems like an unusual request by the city. Do they realize its age?

 

[r13]

I guess it is a procedural requirement for filling the check box. Find out why they are interested in it, then start from there. An simple inquiry may save your time and money. Actually, it is more of a huge flower bed than earth retaining structure, in my opinion.

 

[BAretired]

Try to convince the authority having jurisdiction (AHJ) into accepting the wall as is. It has not moved in years and would not be a life threatening situation, even if it fails. In all probability, the retaining wall was not properly constructed in the first place. That is likely the reason for the two tie-back anchors.

If the AHJ insists on further measures, lower the grade on the high side of the wall. This will mean temporarily removing vegetation between retaining wall and stair.

There are no weep holes at the bottom of the retaining wall. If the native soil is typical Alberta clay, it may be advisable to place drain rock behind the wall just above driveway elevation and drill one or two weep holes through the wall to let water drain out onto the driveway.

BA

 

[CANeng11]

Thanks everyone. I will talk to the AHJ and see if we can approve it based on satisfactory past performance.

 

[r13]

Past performance can only be a plus on top of other supporting evidence/calculation. Be prepared for rejection if it is the sole point.

 

[HauerEng]

I can guarantee this wall will not meet current code requirements! Your picture indicates it has no visual signs of distress and it has "withstood the test of time."
Convince the "jurisdiction" that any report is unwarranted.

 

[r13]

Hauer,

Do you mean "will" but miss typed "will not"? If the latter stands, why it will not pass the current code? Just curious.

 

[CANeng11]

In part L of the National Building Code of Canada Commentaries it allows for approval of buildings and components that have demonstrated satisfactory capacity to resist loads rovided: An engineer review does not reveal evidence of damage, distress or deterioration; the system is reviewed and critical details examined and checked for load transfer; the building has demonstrated satisfactory performance for at least 30 years; and there have been no changes within the past 30 years that could significantly increase the loads on the component or affect its durability, and no such changes are contemplated.

 

[hokie66]

HauerEng is correct. But the best thing about this wall is that it is leaning into the retained soil. I would submit my own version of a "retaining wall disclosure statement", describing the observed long term performance of the wall rather than all those design parameters. Then hopefully, common sense will exist at the jurisdiction.

 

[JoelTXCive]

Do those ties go all the way through to the other side? Is there any evidence of them on the stairway side?

It looks like there is only about 3 feet between the back of wall and the staircase wall. I can't imagine there is a deadman back in there. I would think that maybe the original builder just tied the two wall stems together with a threaded rod.

 

[CANeng11]

Joel, no evidence of that, but I suspect you may be right.

 

[SKJ25POL]

CANeng11 (Civil/Environmental)(OP)

Can you provide us couple more pictures from different angles so we can better help you with.

 

[Tomfh]

I agree you need to find out what the council requirements really are. It would be a pity to tear apart the garden for no reason. If the city is officious and demands all the parameters to the letter you may need invasive investigation, however I’d err on the side of less destruction if possible.