This multi-family property was experiencing water seeping over a sidewalk and across a portion of the parking lot. One tenant had already fallen and injured herself. The source of the water was subsurface flow that was being exposed as it migrated to the lower elevations where the walkway and parking area were located.
In this photo, you can see the fabric used to line the trench and the perforated pipe placed in the bottom. Not shown is the gravel that will be used to backfill the trench to near the top. The theory is that water will flow across the trench and fall through the spaces between the gravel aggregate to the bottom of the trench. It will then enter the pipe through the holes in the pipe and then flow with the slope of the pipe to the discharge point.