Need Drainage Advice--Paver Sidewalk
I live in Atlanta, GA in an older neighborhood that uses 18" hex concrete pavers for sidewalks; our sidewalk is 80 years old. I've recently pulled up the pavers to remove broken ones, reroute others around tree roots, etc. As part of this project, I'm also trying to remedy a drainage problem where water collects after heavy storms.
(And, yes, the sidewalk is the homeowners responsibility in our area. The City doesnÂt take care of them; nice, huh?)
The problem area originally was due to two issues:
1. the pavers were sitting in a depression, possibly caused by erosion over the years
2. incorrect slope on the sidewalk, both along the run and down the hill and from the house towards the street
Additionally, roots from a large pecan tree in the center of the walk pushed up the pavers, creating a rise in the middle of the run. Water was both coming down the hill from the corner and then back down from the other direction due to the rise in the middle. Even though the sidewalk is properly sloped (about a 2' drop over 50' or 4%), the rise was causing the water to puddle.
I've now leveled out the ground and tried to ensure a constant slope:
a) from the house to the edge of the sidewalk
b) from the top of the sidewalk to the bottom
and c) I also created a perimeter around the tree to protect the tree roots, narrowing the sidewalk there
Doing c), though, created a barrier wall in essence, as the ground around the tree is now higher than the sidewalk pavers. I think the water will now run down the sidewalk correctly, both from the top and away from the house, but will collect in that new corner.
Also, by excavating the sidewalk edge (by the street) to create a decent slope down from the house, I've now exposed the dirt below the curb edge and I'm concerned about that eroding.
A neighbor suggested building a french drain to route the water around the corner/tree and on down the hill.
1. Is a french drain the correct solution?
1a. If so, do I need to build it from the top of the sidewalk all the way to the bottom (approx. 50') or can I start it further down near the problem area?
1b. If I build a french drain, do I need to use 4" pipe or can I go narrower?
2. Do I need to build a retention wall out of 1x6" board along the drain to protect the exposed dirt wall caused by my excavating the walk edge?
Some photos (below) to explain better plus elevation map.
1. Problem AreaÂMarked
2. Elevation Map
3. Problem AreaÂFlooded, Before Resetting Pavers
4. SidewalkÂAfter Resetting Pavers, Looking Down
5. SidewalkÂAfter Resetting Pavers, Looking Up