Prevent groundwater and surface water from damaging your Seattle home with drench drains, weeping tile, and land drains by Seattle Rockeries. French rock drains are perimeter trenches filled with gravel or rock that houses perforated drainage pipe. Sub-surface french drains divert surface water away from hardscapes, driveways, and homes. French drains offer an improvement to open ditches through the use of crushed rock, rubble, or natural stone to filter stormwater and cover dangerous trenches. French drains are used heavily in the construction of retaining walls and foundations.