Hi, I’m working on a backyard project in Florida and could use some advice. I have a 5' tall CMU seawall (or call if a retaining wall) that borders a freshwater retaining canal - no tidal action. About 1 foot of the wall sits below the canal’s dry season water level. Of course during heavy rains storms the water level rises 1-2 foot, or ocassionally floods during historical storms. The wall is hollow-core construction, with only the rebar sections grouted. The wall also has deadman anchors which is a rebar embedded in concrete.
The native soil is loamy sand and tends to stay pretty saturated and spongy near the base of the wall. Theres been some erosion in the past. To add, I found a block of concrete poured behind the wall (which is separated from the wall and has a void in between), which looks like someone filled a sinkole or just dumped it there.
I recently removed a few trees that were planted right next to the wall, hugging it, since it would most likely push the blocks away soon. This left me with a few deep holes. I'm now figuring out the best backfill material and also considering running a French drain along the wall to help control water flow from hardscaping and runoff. Not sure if hydrostatic pressure is a concern here. I haven’t noticed any drainage, jets or weep holes.
1. Should I backfill with the original native soil, or would crushed limestone be better for stability and drainage?
2. If I go with crushed limestone, is it safe to place and compact it directly over the existing nnative soil a few feet down or should I excavate down to the base of the wall first to remove potentially saturated uncompacted material?
3. How close can a French drain safely be placed to the seawall? I’m concerned about water potentially migrating through the backfill and increasing pressure against the wall.
4. Would you put a geotextile fabric at the wall to control erosion?
Thanks in advance for any advice!
The native soil is loamy sand and tends to stay pretty saturated and spongy near the base of the wall. Theres been some erosion in the past. To add, I found a block of concrete poured behind the wall (which is separated from the wall and has a void in between), which looks like someone filled a sinkole or just dumped it there.
I recently removed a few trees that were planted right next to the wall, hugging it, since it would most likely push the blocks away soon. This left me with a few deep holes. I'm now figuring out the best backfill material and also considering running a French drain along the wall to help control water flow from hardscaping and runoff. Not sure if hydrostatic pressure is a concern here. I haven’t noticed any drainage, jets or weep holes.
1. Should I backfill with the original native soil, or would crushed limestone be better for stability and drainage?
2. If I go with crushed limestone, is it safe to place and compact it directly over the existing nnative soil a few feet down or should I excavate down to the base of the wall first to remove potentially saturated uncompacted material?
3. How close can a French drain safely be placed to the seawall? I’m concerned about water potentially migrating through the backfill and increasing pressure against the wall.
4. Would you put a geotextile fabric at the wall to control erosion?
Thanks in advance for any advice!
