When you think of drainage, you might picture a trench filled with gravel and pipe – easy peasy! But the old style of using gravel in a trench is flawed and here is why – gravel overlaid with sand creates a perched water table. Unless the sand depth is at least 10-12 inches, the surface can stay wet and black layer will likely form. Subsurface drainage trenches will perform much better when backfilling the trench with sand; not gravel. Sand also more effectively “wicks” water from surrounding heavier soils than gravel. Some additional and perhaps non-traditional methods to improve drainage at your facility include:
Dirty sand on top of sand – Subsurface trenches should be filled with a well-drained sand – i.e., a sand that drains from 30-60 inches per hour. The top 4-6 inches of the profile should be amended with soil or peat moss to achieve a moisture retention of 15-20%. This will help to retain surface moisture and avoid the “tiger stripes” that will develop if a coarse sand is used at the surface.
Put a sock on it – A geotextile fabric can be used to line the bottom of the trench to discourage fine material from working its way into the drain lines. The fabric should also line the drain pipe.
Do NOT socially distance the drain lines – Water that infiltrates soil will only move laterally very slowly and often no more than a few feet. For example, soil water will move sideways at a rate of only 0.1 inch per hour in a soil that drains at 2 inches per hour and has a grade of 5%. If the same soil is graded at only 1% slope, the internal soil water movement slows to only 0.02 inch per hour! Therefore, in heavy textured soils, drains must be spaced closely – i.e., 10 to 20 feet in many cases.
Deeper is better – A good guideline for the depth at which drain pipe should be installed is 18-24 inches. The slower the soil infiltration rate, the deeper the drains should be. Shallow drains will result in chronically wet surface conditions and black layer.
Surface drainage trumps subsurface drainage every time – Facilities will get much more bang for their buck by capturing surface flow before it puddles in flat and low-lying areas. Rather than focus on the wet areas, capture water with surface drains in higher elevations. From a cost perspective, it is prudent to capture as much surface flow as possible before spending a great deal of time – and money – on subsurface drainage infrastructure.
Google it! – Use Google Earth to help identify surface elevations and plan for both surface and subsurface drainage. To view the elevation changes across the course, move the mouse across the screen. At the bottom right of the screen, the latitude, longitude and elevation in feet will change based on where you move the mouse.
Outsource it – A completed drainage project should be functional and the trenches should be nearly undetected by golfers. Achieving a clean, level surface that blends in with the surrounding turf and terrain is no easy task. In most cases, it is best to outsource this work to a company specialized in drainage installation.
Do your homework before installing any drainage system – Here are some great resources from Turf Drain America:
If your course is planning drainage work or seeking to improve firmness and playability across the golf course, reach out to the USGA Green Section for more information on these strategies or any other agronomic practices.
West Region Agronomists:
Brian Whitlark, senior consulting agronomist – firstname.lastname@example.org
Cory Isom, agronomist – email@example.com