60yr old seawall has Grand Canyon degradation

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Old 09-14-19, 05:26 PM
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60yr old seawall has Grand Canyon degradation

32ft long vertical wall built 60yr ago, then the sloped reinforcement added a few yr later. There are no weep holes, or french drain behind wall to relieve hydraulic pressure. What began as surface repair revealed Mother Nature relieved hydraulic pressure by creating the Grand Canyon in center of wall (see pics).
Ready to start the repair, and have Q's:

Should I punch a hole in the dirt under the vertical wall to lay 1.5" PVC extending behind the wall to provide a weep hole through to front of wall before pouring concrete? Idea is that that PVC runs into stone around french drain that will be added after repair.

The base has a slope of 7 to 8" over 24". Will use bonding agent and Quikrete Concrete mix and add some larger stones. Will a dry mix match this slope without slumping? If not, what is recommended to slope the 7 to 8" over 24"?

How deep recommend for the french drain? Water level reaches approx half way up vertical section for awhile in early spring, then most of warm months is below the sloped section to well below the wall.

Thanks for your time!
Surfin
 
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Old 09-15-19, 05:10 AM
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Your pictures are too close to see your wall's construction.

You did not say where you are located. In NC we have a government organization called CAMA that has god like jurisdiction over almost anything coastal including many/most sea walls. I would contact your regulatory agency regarding your damage and intended repairs and gain their approval before beginning work. CAMA here can be quite unforgiving of unapproved work.

I would plan on excavating the back/land side of your retaining wall and install a drainage system. While the area is exposed you may need to pump in some grout to fill in and seal up the washed out areas. Damaged areas of the wall may have to be removed and re-built. A seawall is such a harsh and demanding structure that it might not be the best place for concrete fillers or patches.
 
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