Sports Field Management - August, 2012
Field Care: Drain the Rain
New trends in moving water
In May, a much-anticipated baseball game between Illinois State and Illinois Wesleyan was canceled because of wet field conditions. It was the second consecutive year that rain prevented the Horenberger-Bass Classic from being played. Rainouts are a common occurrence in baseball and many other sports, but it's not always the rain itself that stops the game, it's the aftermath of standing water on the field. While no one can stop the rain, new advances and techniques in field drainage can help move water off sports fields to give athletes a better chance of getting in the game.
Greenshield Systems digs a trench for drainage on a sports field in the Pacific Northwest.
The most basic technique for moving water off a sports field is through surface runoff. Constructing a field with proper crowning and grade is critical to move the water off the playing surface. Dan Hodson, president of Sportscapes Construction in Red Oak, Texas, likens the contour of a natural turf sports field with proper surface drainage to a turtle's back.
In a paper called "Drainage for Sports Fields," Dr. James McAfee, associate professor and extension turfgrass specialist at Texas A&M, outlines basic recommendations for the slope or crown of fields, depending on the sport:
- Football fields: 12 to 18-inch crown in the center of the field with a continuous grade from the center of the field past the sidelines.
- Soccer fields: 6 to 12-inch crown. An alternative is to slope from sideline to sideline, or end zone to end zone, ensuring a continuous slope.
- Baseball fields: The pitcher's mound should be the highest point of the field, 10 inches higher than home plate. From the mound, the field should be sloped in all four directions at a 1 to 1.5 percent slope.
- Softball fields: The most common grade is to slope the entire field, starting at the backstop moving toward the outfield fences at a .6 to 1 percent slope. "A second method," McAfee writes, "is to provide a level crown through the center of the softball field going from home plate to the pitcher's mound through second base and then to center field. Then the field is sloped at a 1 to 1.5 percent grade from the center of the field toward the right sideline and from the center of the field to the left sideline. The advantage of this design is that home plate and the pitcher's mound are at the same height, which for fast-pitch softball is important."
Greenshield Systems' Jeff Horan talks with a crew member during installation of a drainage system on a sports field at Highland Middle School in Bellevue, Wash.
However, surface drainage is often not enough to keep a field playable. Underground drainage systems can help move water faster. Two companies are using innovative techniques to improve how underground drainage systems work on natural and artificial turf fields.
When building an underground drainage system, "the first thing to consider is if we have an outfall point to connect to," says Jeff Horan, co-owner of Greenshield Systems, based in Mount Vernon, Wash. Horan says most existing sports fields have some kind of stormwater system in the form of a series of swales, holding ponds or ditches. If no catch basin is available, an outflow area can be created by digging a dry well.
Since 1999, Greenshield Systems has installed piped drainage systems primarily on existing natural turf sports fields and golf courses. What makes the Greenshield methodology unusual is that all of the trenched pipe is backfilled with sand, the same quality sand used to build USGA golf greens. Horan says that although the sand backfill is commonly used in Europe and Australia, his company is one of the few using the method here in the U.S.
Trenches are dug and pipe is laid using laser-guided machinery developed by Greenshield Systems. Trenches are dug at a minimum of 14 inches. The pipe is laid in the sand trench and backfilled all the way to the surface, creating a column of sand. The sand column is the critical element of the system in that it allows for easy percolation of water down and away from the playing surface. Once the system is complete, new turf is put down over the sand, either sand-grown sod or hydroseeded. It's important that sod be sand-grown, otherwise the rootzone will be too dense and block water flow down into the sand column.
"The pipe has small perforations in it. When the water goes down through the sand column, it doesn't just go right into the perforation and go into the pipe. Actually, this is the same for all drainage; it builds a water table in the trench. As the water table gets tall enough, it enters the pipe from the bottom. The pipe is really just holding a void space in the ground. The water table builds up and it then moves laterally because the void space allows it to move unrestricted," explains Horan. "All the drainage is installed with a gradient and it all goes to a low point, which is going to be a storm system or a swale or a ditch or whatever each particular site has available."
Sportscapes Construction President Dan Hodson says he's started using a new flat pipe drainage system with great success, especially on artificial turf fields in the Dallas area. The AdvanEDGE flat pipe from ADS, which Hodson purchases through Ewing Irrigation, consists of a 1.5-inch-tall by 12-inch-wide perforated plastic pipe with internal pillars for structural support. It can be installed using a knitted polyester sock wrap to help keep out debris.
AdvanEdge flat pipe from ADS.
"When I build a synthetic field in Texas, we excavate. We put in a big liner like a 20-mil PVC liner. We don't want water to hit the ground. We've got heavy clay soils here and when water hits it, it really messes it up. So, on top of that liner, on a football field I'll lay out, in a herringbone pattern, around 4,800 linear feet of that 12-inch AdvanEDGE pipe. Then I'll put my 6 inches of stone directly on top of it. AdvanEdge makes a fitting that goes onto the end of the 12-inch pipe that turns it into a round fitting. What it does is it enables you to take a flat piece of pipe and put it into a round pipe. That's why I prefer to use it. A lot of companies don't make the fittings that tie into a round pipe," Hodson says.
Without the connector into a round pipe, the water would simply filter out into a ditch covered with gravel, along the order of a French drain. Hodson says his method is preferable because "I actually tie into the collector pipe for a faster infiltration rate."
The 12-inch flat pipe will move about the same amount of water as a 4-inch round pipe, Hodson notes, yet it takes up a lot less room in the project. "It's the same area you're draining, but it takes up less space vertically. I can put my rock on top of it, put all the drainage in there, and still have enough base stone for my synthetic turf."
For the past five years, researchers at Michigan State University (MSU) have been working on an alternative drainage system for use on sports fields. The Sand Cap Build-Up System, developed by A.R. Kowalewski, J. N. Rogers III and J.R. Crum at MSU's department of crop and social sciences, utilizes a system of drains and an extensive topdressing regimen to create a "sand cap" to aid in percolating water through the rootzone. The benefit of the program, though still in testing, is that the system can be implemented with little disturbance to the field.
According to the MSU plan, drains are cut into the existing field running lengthwise on 6 to 20-foot centers, depending on the surface grade and slope. Drain tile is put in the lines and it is backfilled with pea stone and then sand. Once the disturbed surface is regrassed, more than likely by hydroseeding, then begins an aggressive program of topdressing with sand. Over a period of months, the goal is to achieve a cap of at least 2 inches of sand topdressing.
In the research report, findings indicate that "as much as 1/3 inch of topdressing can be applied in a single application without being detrimental to turfgrass health. However, lighter more frequent applications (.5 inch of topdressing applied over a one-month period) will increase turfgrass cover, density and surface stability. Up to 4 inches of rootzone topdressing material applied over a two-year period, while not improving stability, will increase turfgrass coverage."
Hire a pro
McAfee wrote that it is critical to hire "an architectural firm and/or contractor that has extensive experience in the construction of sports fields. Just because someone knows how to run a grader doesn't mean they can build a sports field."
Hodson agrees. "If you've got a field that doesn't have the proper crowning, you have to do a lot more work to get it right," he says. "A contractor who will contour your field properly, get it to flow, is so important on natural grass fields."
In the end, it's all about moving water off the playing surface. "Drainage is simple," Hodson says. "Water goes to a low spot; see where the water is going and take it out of there."
The author is a freelance writer and photographer based in Burlington, Wash.