Abstract: Drain wet bunker floors by installing drainage tile. Check working grades before starting the project.
Soggy bunker sand creates playability and appearance problems. Repair involves removal of existing sand and installation of double-wall HDPE pipe into the bunker floor.
Start the retrofit process by locating a suitable discharge point for the bunker drainage pipe. Set the laser on level. and take a shot on the top of sand on the low point of the bunker. Add the depth of sand and depth of pipe to this measurement. For this example , I’ll use a 6″ sand depth. The pipe invert, or bottom, is 12″ below the sand layer. The combined measurement is 18″ below the top of sand. This is the depth of the bottom of the drain pipe.Measure up on the rod, and add 18″ to the rod elevation. Remember that the bottom of the rod goes down when height of the reciever goes up. Let’s assume the rod elevation of the sand layer is 5 feet, the combined elevation is 6 feet, 6 inches.
Next, locate the discharge point. Choose this point carefully because it will usually be wet. Be sure that the exit drain discharges into a down slope without creating a water pocket. If you can’t find a suitable discharge location, consider tying into nearby drain culverts or pipe. Some construct cisterns or leaching catch basins.
Work the laser from the discharge point to the bunker. Establish a minimum slope of .1 %, or 1 tenth of an inch in 100 feet. Remember to land at the low point in the bunker at a point 18″ below the sand surface.
Install pipe in a herring-bone configuration, 12″ below the bunker floor, not the sand. Be sure to slope pipe down to the low bunker floor point.
I prefer to remove all the sand. Store the sand on plywood next to the bunker, or install new bunker sand after the pipe is installed. The partial sand method involves painting the pipe pattern on the sand, and removing only enough sand to excavate the trench and install the pipe.
I like to backfill bunker drainage pipe with bunker sand. Others use 3/8″ pea stone.
If the discharge point is exposed, add a rodent guard, a wire barrier that keeps rodents from entering, and clogging, the pipe.