Summary: Install small drainage inlets, or vertical structures, in golf course drainage systems using the following information.
This post will discuss the installation of small, 12″ and under, drainage inlets. I don’t use preformed PVC structures because of the expense. I construct my inlets with double wall, solid, HDPE pipe.
Inlets direct surface water into drainage piping. Installed vertically, they are covered with a plastic or ductile iron grate.
I always add a bottom. You can use an HDPE end cap or make your own out of HDPE sheets. Always drill a few dozen holes to offset any hydraulic pressure that may push the structure up.
When I cut the horizontal pipe holes, I work my measurements from the cover down. It’s critical to have a full corrugation on the HDPE pipe top. If you cut it after installation, you may end up cutting into a weak portion of the pipe, and the structure will fail.
I use a laser to determine the inlet rim elevation. I include a inch or two for pitch. Survey the limits of the inlet swale and be sure to allow for the lowest point. Let’s assume that the rim elevation is 64.00
Next, determine the invert of the incoming and exiting pipe. Work this out with graph paper and surface elevation shots. Let’s assume that the invert is 62.00. The incoming hole is 2.00 below the inlet cover. Measure down 2.00 with the cover installed.
Cut the inlet 2.00 plus 1.00 (the depth of the sedimentation basin) This structure is now 3 feet long.I use a 4″ hole saw with a battery-powered drill to cut the horizontal pipe holes.
Excavate the hole 18″ below the invert. Add 18″ to the rod elevation to assist in determining depth. Add 6″ of 3/8″ crushed stone, then install the inlet. Use a level to install the structure plumb.