Sports Field Management - July, 2009


Plan Irrigation to Fit Field Needs

What to consider before you buy
By Ken White
Irrigation for synthetic fields should reach from the sidelines to midfield.

There are many issues to consider when working with a company on an irrigation installation and when planning a renovation or update of an existing irrigation system. It will be less costly overall to start with long-range plans in mind. Planning should involve potential future uses of a field and the possible addition of more fields to the site later on.

Start by determining the field basics. A sand or sand/peat profile or a sand-capped field will have faster infiltration and percolation, channeling water away from the surface and into the rootzone. Native soils typically have slower infiltration and percolation rates. A higher percentage of clay in the soil profile may require multiple short irrigation cycles with a delay in between for the water to soak in.

Drainage is a key component in making the irrigation system more valuable and handling natural precipitation. You want to have playability within a couple of hours of a rain event. On a new field or total field renovation, subsurface drainage systems should be installed prior to the irrigation system. For an existing native soil field, a trench and flat drainpipe system, such as the Hydraway, can pull the surface water down into the soil.

A minimal slope will move surface water off the playing surface, but must be channeled properly into detention swales or pipes to prevent excessive runoff. With a sloped field, irrigation heads would be set up in a row running parallel to it. If set up running perpendicular, the output from the heads at the top of the slope will run off toward those at the lower elevations, underwatering some areas and overwatering others.

The climatic region and varieties of turf that will be grown on the field also affect component decisions. You'll need to determine if the field will be used for multiple sports, what those sports will be, the amount of field used during each sport season, and the age and skill level of the players. The larger the players and the more intensive the play, the greater the need in irrigation, drainage and a solid turf management program.

With all that in mind, prepare a basic maintenance practices program that takes into consideration how the irrigation will impact turf growth and the overall maintenance needs. Develop an adequate budget for increased maintenance as part of the overall cost projections for the field.

Analyze the water window, the number of hours available for irrigation during late evening and early morning hours, at the greatest level of field use. You may have a six to eight-hour window to irrigate multiple fields. A larger pipe size and pumping capacity will allow you to run multiple zones on several fields at the same time so fields can be ready as needed.

You'll also want the ability to run each zone for a short cycle during the day to cool down the turf to avoid heat stress or disease outbreak, and to check to make sure all the heads are operating properly.

Field notes

In a stadium setting, whether the turf area is inside a running track or whether the turf serves one sport or multiple sports, the irrigation system should cover the whole turf area, the playing surface and the sidelines. Those areas along the edge of the running track need part circle heads to throw away from the track toward the center of the field.

For an open area practice field with grass sidelines around it, the sprinkler heads could be positioned off the playing surface in the surrounding turf. For a large open space that will be set in different configurations for multiple fields and multiple uses, plan the irrigation for the largest size field. If the field layout will change directions within that open space, take that into consideration when developing the zone design. The crown of the field may have more to do with the irrigation system layout than the type of field use in that situation.

With most rectangular fields, the heaviest areas of play are at the center of the field. Plan for a zone down the middle of the field to control irrigation in that segment.

For a baseball or softball field, it's cost-effective to include a dust control system, one or two zones equipped with high speed rotors, to quickly irrigate the skinned area. Plan to install a quick coupler behind the pitcher's mound and at first and third base down the normal curve of the base path. Set up the infield and outfield zones separately, basing the number of zones on the water source and pressure.

Renovations and retrofitting

Check the existing irrigation system prior to making changes. It may not require a complete water audit, but make sure the heads are all performing properly, checking the precipitation rates and the head-to-head throw to make sure delivery is uniform and consistent.

If you're just renovating the field area between the hash marks, you probably won't need a major renovation of the irrigation system. After removing the existing sod and installing new soil, the heads could be raised or lowered with the swing joints to fit the new surface level.

Head-to-head coverage is the industry standard.
Conduit, irrigation components and subsurface drainage systems all lurk beneath the field.

In a more aggressive renovation, if the system is relatively new, you won't need to dig into the piping unless there are problems. To retrofit an older system, the piping will probably need to be redone. You may be able to reuse the controller, the backflow valve or the booster pump. Often, if the piping is quite old, renovation starts at the backflow preventer with new components installed from there. If you've been replacing heads all along, you may be able to put those into a new system.

Be aware of pressure changes. If a new subdivision has been added in the area, the field irrigation system may have more or less pressure, which may require a change out of the nozzles or resizing of the booster pump.

System considerations

You'll need to know the water source and how many gallons per minute (GPM) you can get from it. You'll also need to identify the electric source and the availability of pressure to move the water, measured in pounds per square inch (PSI). These factors will dictate whether you need a booster pump and the rest of the components for the irrigation system that fit those parameters.

Most athletic fields use municipal water supplies. If you have a primary or auxiliary source that uses effluent water, additional system components, such as an inline filter system, "dirty water" valve or scrubber, might be needed to filter out sediment or grit. These would handle impurities so special heads wouldn't be needed. Piping from the source to the system could be an issue. Usually, the water would be released into a creek or pond with the irrigation system working from there.

The current industry standard for piping is class 200 PVC. Pipe size is based on the size and delivery needs of the system. The majority of PVC has a good life span, so if it's in the right place on an existing system, you may just need to replace the valves and sprinkler heads in a renovation. Plan to install the swing joint type of fitting, which provides greater flexibility.

Head-to-head coverage is the industry standard. Most of the sprinkler throw is calculated with a 4 mph wind factor. If the fields are outside in an open area or within a stadium setting that creates strong wind patterns, track prevailing conditions.

Use good quality sports field heads and valves. Major suppliers, such as Toro, Rain Bird and Hunter, have developed components especially for sports fields. There are multiple options that provide precise coverage for specific field needs. Consider a stainless steel sports field head over a plastic head, especially for a sand or sand-capped field, because of the abrasion factor.

Choose sprinkler heads that fit specific needs, such as these with a low trajectory for open, windswept fields.

Plan to put the valves and valve boxes as far off the playing area as possible. These can be covered with an artificial turf segment on the lid to hide them. Pop-up sprinkler heads will be set within the play area with the top of the rubber cap covering them even with the top of the soil.

Smart water

Smart water is a great concept. Some irrigation systems incorporate a data-gathering system and smart controller as part of the initial installation. Some controllers connect to off-site weather stations, and others use data that is monitored via satellite. There are several choices of small data-collection units that mount to a building on-site, and they communicate with the controller providing wind speed, temperature, humidity, rainfall and the evapotranspiration (ET) rate.

If nothing else, invest in a rain sensor. Just the perception that the facility is wasting water by irrigating during a rain event can damage its ability to retain water use privileges during periods of restrictions or bans.

With so much new technology available, irrigation can be more precise and, even without a computerized system, sports field managers can achieve better water distribution.

Ken White, project manager for Munie Greencare Professionals in Caseyville, Ill., has nearly 20 years of experience in the construction and renovation side of the industry.