SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: https://read.dmtmag.com/i/40933
Irrigation&Drainage Many factors must be considered in de- termining the correct drainage system, in- cluding (but not limited to) soil type, local precipitation, field use, budget, existing slope and local regulations. Work with a design professional to help choose the right type, with the correct specifications for the amount of water you want to move. The traditional type of drainage system for a sports field has been the pipe drain which uses perforated pipe placed in trenches in the subgrade. These pipes are laid in trenches, surrounded by coarse sand or clean stone to within 4 inches of the surface of the inches) filled with sand or blended im- ported rootzone materials with known high infiltration rates) at a relatively narrow spac- ing (typically less than 3 feet on center) that are crossed by deeper trenches (typically around 12 to18 inches in depth, typically between 2 and 6 inches in width) with small diameter perforated drains. These drain trenches run perpendicular to the shallow sand trenches and follow the field slope in order to de-water the field. This type of sand drainage system is a cost-effec- tive method of building into a native soil field some of the same benefits of a sand- Most everyone knows about proper irrigation. But not everyone, it seems, knows about maintenance beyond that. subgrade and capped with sand. Water then drains through the rootzone and stops in the trench where it enters the pipe from the bot- tom. Drains are typically placed 3 to 10 feet apart for native soil, and 10 to 30 feet apart for sand-based fields. They are surrounded by clean stone or coarse sand. Another type of system exists: flat drains, sometimes called strip drains, 6 to 18 inches wide and 1 to 2 inches thick, without a wrapping of filter fabric, which are placed horizontally on the subgrade during con- struction. They also may be trenched in and placed vertically after installation of the root- zone in either native or sand-cap fields. In addition, say builders, there's the least expensive (and still highly effective) sand vein system, sometimes called a sand silt sys- tem. This in particular works well in a native soil field, says Devin Conway, Verde Design Group, Santa Clara, CA) when attention is paid to the finer points of installation. "A few items I would suggest an owner consider for natural turf fields in terms of drainage (assuming the field is not sand- based and the native soil has high levels of silt and clay content) would include a drainage system that extends into the play- ing field area, and not just at the field's low points," says Conway. "An example of a sys- tem that would suffice is a slit sand drainage system, which would have a series of shal- low trenches (typically less than 12 inches in depth, typically no wider than a few 32 SportsTurf | September 2011 based field, without many of the large con- struction costs, and the field also uses much less water than a traditional sand-based field. Other traditional methods of drainage for a natural turf field include surface drain inlets (though these should only be used outside the area of play for obvious safety reasons) and subsurface drain tiles, such as French drain." And sometimes, says Andy Hord of Preci- sion Sports Surfaces, Inc. in Charlottesville, Virginia, those tried and true systems last be- cause, well, they're tried and true. "Last summer, I started to dig up a 30- year-old sand-based drain along the edge of a track we were stripping and overlaying," Hord notes. "After tearing out the first 50 feet we stopped as it appeared to be working as well as it did the day it was put in. We stopped and rebuilt the part we had re- moved." MAINTENANCE It's the least glamorous of all subjects when it comes to fields. Everyone knows about mowing. Most everyone knows about proper irrigation. But not everyone, it seems, knows about maintenance beyond that. "Proper maintenance will really help drainage issues," says Dan Wright. But, he adds, like drainage itself, it's where too many cut back in order to save money. "If you're a pro team or a major univer- sity, you can probably afford it," he notes, "but a park and rec or a local high school often has budget issues, and that's where they might cut." Conway recommends doing regular walk- throughs of fields to keep an eye out for problems. "Tell-tale signs to keep an eye out for in- clude the obvious, such as standing water after irrigation cycles or rain events, as well as soft areas, even in warm weather, which can indicate water is not getting through the soil profile quickly." He also recommends going over all as- pects of the drainage system in order to make sure it isn't degrading with time. "As with any system, the drainage infra- structure should be checked at least on a semi-annual basis. If the field has a slit sand drainage system, it is recommended the shal- low sand trenches be supplemented with ad- ditional sand at least every ten years, if not sooner, in order to continue to improve the water pathways to the in-field piping (and as an added benefit, it improves the soil charac- teristics of the native soil field over time by improving the sand content in the playing field). Drain lines and surface drain inlets should be inspected and cleaned, and low spots and depressions should be addressed so that the water can flow uniformly towards the intended drainage vehicles." Of course, says Hord, not all maintenance people have been trained in proper field care. "We see people covering storm inlets with impervious covers and leaving them in place," he says dryly. "Makes me scream." Keep inlets clean, and keep Bermuda grass trimmed back in order to facilitate drainage. If a track encircles the field, check the adjacent drains routinely to make sure they have not become covered or clogged— something else that contributes to water ponding on both the field and the track. If, as with a baseball or softball field, there are skinned areas that are dragged in order to ensure uniformity, make sure the dragged material isn't creating a dam at the edge of the grass and impeding drainage off the field. ■ Mary Kay Sprecher wrote this article on the behalf of the American Sports Builders Associa- tion, which helps designers, builders, owners, operators and users understand quality sports facility construction. www.sportsbuilders.org www.sportsturfonline.com