Most of us have managed an infield under less than perfect conditions at one time or another. The infield may be in need of reconstruction due to years of use or it may have inherent problems caused by improper construction. Whether simply a facelift for an existing infield, or the construction of a new facility, a successful project requires consideration by those involved in the construction process and by those who manage the use of the field.
It’s natural to want the best infield you can have when the opportunity arises to renovate or construct an infield. Typically, designers and engineers look to construction practices used on professional infields as a reference when designing for schools and municipalities.
For the sake of this article I would like to take the liberty of providing my perception of a professional infield. A professional infield is an infield constructed on a full gravel blanket below a loamy sand or pure sand root zone. It has a ½% slope radiating out in all directions from the area around the pitcher’s mound. The skinned area is constructed with two distinct layers. The base is constructed using an infield mix with less than 70% sand. This mix is managed at a precise moisture level to provide just the right resilience to the players. The base is covered with a thin layer of topdressing such as calcined clay, vitrified clay or possibly a mixture of both. The integrity of these layers is protected with the utmost care. For most of us, managing a professional infield such as this would be like Charlie Daniels playing Tchaikovsky’s Violin Concerto. Rather most of us maintain infields in the grey area of right and wrong somewhere between a professional infield and chase out the cows close the gate and play ball.
Perception is nine tenths of the flaw
I have witnessed municipal infields constructed on a full gravel blanket using heavy textured impermeable top soil and a heavy clay infield mix because the perception is that this gravel blanket is going to provide superior drainage for the infield. These designers don’t realize that unless the root zone has a very high rate of hydraulic conductivity and is capable of allowing water to pass through it efficiently, the only real benefit to any subsurface drainage is the control of ground water or a high water table.
These same designers like the ½% slope because; actually I don’t know why they use it other than because it’s used on professional infields. What they fail to realize is that ½% slope is almost as ineffective as a gravel blanket in a turf area unless again, you have a very permeable root zone and some form of subsurface drainage. On the skinned area, ½% slope is very difficult for the average maintenance crew to manage effectively and typically requires laser grading a few times a year to remain effective.
Some designers recommend a heavy textured clayey infield mix like XYZ stadium, not understanding that unless the moisture in that mix is impeccably managed, it’s going to get hard as a rock.
I witnessed a regulation little league infield constructed with a conical grading plan similar to the professional field I described. In this case the designer was sharp. He understood that ½% slope isn’t sufficient. He therefore recommended a 1% slope radiating out in all directions from a point centered on the infield turf. What he failed to realize is that you cannot construct a regulation pitcher’s mound using this grading plan and adhere to the requirement that the pitching rubber be 6” above home plate. In fact, there would be no mound at all. A 1% rise from home plate to a pitching rubber at a distance of 46’ would be about 5.5”. This would however be a very effective grading plan for a softball infield with no mound.
This same consideration afforded to a little league infield is necessary for a 90’ baseball infield where the height of the pitching rubber is required to be 10” above home plate. In this situation you cannot construct a regulation mound using any more than a ½ % slope from the pitcher’s mound to home plate. Even at ½% slope, the mound would only be about 6” high allowing only enough elevation for a 6’ landing zone in front of the rubber. In this situation the desires of the coaches and athletic director need to be understood and the requirements prioritized to allow for a successful project.
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