French Drain in Front of Retaining Wall?

[BungoPete]

I have been asked to comment about a problem of a retaining wall with water leaking under it. The wall istself is made from 10 x 10 PT beams and is about 6' high. Because of its location it is impossible to excavate behind it. The wall is about 15 yrs old and is in very good condition.

It is located near a beach and a small building (up on posts). Unfortunately, there is water coming from three or four places at the base of the wall. This appears to be natural run-off from the water table. There are several places in the imediate area where water naturally flows to the sea.

The problem is that some of the water remains standing and the ground is generally wet, mucky and covered with rotted leaves etc. This is also causeing parts of the building to rot.

My idea is to put a french drain in front of the wall about 6 inches below grade and two or three "Ts" going under the wall to collect water where there appears to be a major source. The natural grade will facilitate this and I will put an elbow at the end to allow the water to the beach (currently it runs under the building). Again, because of the inaccessable location, it is not possible to excavate behind this wall.

Any insight or suggestions will be greatly appreciated.

 

[civilperson]

If there is enough natural fall to accomplish your french drain to daylight, then there is a enough slope to grade the ponding area to slope around the building and then to the beach.

 

[BungoPete]

Hello and thank you for the message.

Please forgive my ignorance but I need some clarification. Are you saying that I should just build an open trench to carry the water away? I have thought about that but the building is only about 2 to 3 feet away from the wall and the area is constantly getting filled with leaves.

My plan was to surround the pipe with crushed stone right up to grade level so any rain water will not linger and then the ground and leaves will dry out.

 

[gbam]

Why not capture the runoff in a catchbasin or two and convey it in stormdrain? I am not talking about a large system just a landscape system.

 

[dik]

If you can create a French drain without undermining the retaining wall and the building, this would likely work to get rid of the water. The French drain would have to go to free drainage or a sump and pump...

Dik

 

[TDAA]

I think civil person is suggesting there should be enough slope to allow you to just make a swale / and or fill the low, ponding area, and this could be designed to flow around the building. No trenching required.