“My field doesn’t drain!”
This is the most common gripe we hear from coaches and facility managers. A wet field means unsafe playing conditions, lost revenue, and re-scheduling headaches. In this three-part series of the H&K Manintenance Minute, we’ll examine the largest barrier to quality athletic fields: drainage. First, we’ll cover the non-grass portion of the field, known as the “skin.”
The only way to remove excess water from an infield skin is with a proper surface grade. Water always flows along the path dictated by gravity- and it is far easier for water to move across a surface rather than through it. When water flows along a slope, it encounters little resistance. On the other hand, when water flows through a porous medium- be it stone, sand, or soil- the water must move around the individual particles. Along its path through the profile, the water encounters frictional and attractive forces from the soil particles. Therefore our goal is to move as much water off the surface as possible, so as little water as possible has to go through the surface.
Figure 1: On native soil athletic fields, the surface grad is vital because water always moves quickly along the surface than through the soil.
Many people believe that installing a system of sand trenches, gravel layers, or pipes beneath the infield dirt will reduce rainouts. Unfortunately, thousands of dollars are wasted each year based on this idea, which couldn’t be further from the truth. The soils used to construct infields are too fine-textured and too compacted for water to seep through to the drainage gravel or pipes. The system never has a chance to transmit water away from the field, because the water can’t even get into the pipes. The only way to get water to “drain” from an infield skin is to slope the surface correctly and allow gravity to work its magic. Additionally, poor-quality soil is commonly used on baseball infields which can cause the field to retain too much water. Infield soil amendments will be addressed in a future issue.
Figure 2: Drainage systems beneath skinned infields is an un-needed expense because water will never reach them.
The surface grade of an infield skin is most often compromised near high traffic areas- where the base runners slide and take their lead-offs, and also where the infielders stand. As players walk, run, and field ground balls, soil is slowly but surely displaced from these areas. The material is carried off the field on players’ cleats, equipment, and uniforms, and it may wash into the grass areas of the field during rain storms. These processes happen so gradually that they are often hard to perceive. Eventually though, the low spots will become large enough to collect water and prevent proper surface drainage. Small areas can be repaired by scarifying the surface, adding material to level the depression, and re-compacting the soil. For more severe undulations, the entire surface must be re-graded with a tractor and laser-leveling equipment. Any buildup of soil along the “lip,” where the dirt meets the grass edge, also must be removed to permit water to flow uninhibited from the dirt to the grass.
Figure 3: Low spots typically form around bases, position areas, and the back arc of the infield skin.
Figure 4: Laser-guided grading equipment fills in low spots on the infield and allows water to drain off the back edge.
In the next two articles, we’ll discuss ways to improve drainage on grass areas. For more turf maintenance tips, stay tuned for future editions of the H&K Maintenance Minute, or contact H&K’s Evan Mascitti at evan@HKSportsFields.com.