I live in the outer Richmond district of San Francisco, so the soil is more like sand than dirt. We've terraced our back yard with two ~3' retaining walls. We are putting in two paver patio's, but I'm not sure how to handle the runoff from the patio surface.
Is a drainage system needed in such sandy soil?
Soil drains very well, but concerned about the runoff accumulating behind the retaining wall.
As far as I can tell there is no existing drainage, so even if I put in a drainage system to handle the runoff where would it drain to? No drainage going to the street or anything like.