Cost and playability analysis of synthetic infill and natural grass in OR
By B.L. Daviscourt, A.R. Kowalewski, J.G. Lambrinos, B. Eleveld, and M. Gould
There have been several investigations into the costs associated with installing and maintaining synthetic infill and natural turfgrass systems. However, no studies have been in depth enough to include a cycle that goes beyond the warrantee period of a synthetic infill field or include the product of maintenance, number of provided hours of use, in the cost analysis.
The objectives of this study were to compare the cost of installation and maintenance across a 20-year period and establish and compare a cost-per-hour of player use value for natural turfgrass and synthetic infill athletic fields. Field budget, maintenance practice, and hours of use data was collected on five natural grass and five synthetic infill fields from field and maintenance managers and directors, athletic directors, field reservation schedules, and player rosters. The average costs of installation and maintenance for natural grass fields were $325,000 and $27,000 while the average costs of installation, maintenance, and resurfacing for synthetic infill fields were $1,212,000, $7,000, and $377,000. Only one of the five natural grass fields was resurfaced or planned to be resurfaced and it cost $21,600. The average costs of the 20-year budget cycle and of providing a single hour of use for natural grass fields were $903,000 and $2.18 while the synthetic infill costs were $1,902,000 and $2.15. These results support the idea that synthetic fields are able to be just as cost effective as natural grass fields, despite their larger costs, by providing greater amounts of player-use hours.
During the 1970’s and 1980’s synthetic turf surfaces started being installed in only a few premier high schools, universities, and professional stadiums. Today the Synthetic Turf Council believes there are currently over 8,000 synthetic multi-use fields in the United States. Part of the reason for this rise in popularity is the ability for the fields to be heavily scheduled with multiple consecutive events with little risk of reducing the longevity of the field. Play on synthetic surfaces is not restricted by weather. There is also belief that the low maintenance associated with synthetic fields balance out the high costs of installation. These assumptions contribute to the popularity of synthetic fields have also sparked a common debate today over the costs associated with natural turfgrass and synthetic infill.
The Turfgrass Resource Center suggests that installation costs of synthetic fields range from $850,000 to $1,000,000 at $7.80 to $10.75 per sq. ft. They also suggest installation of a sand-based natural grass field ranges from $350,000 to $500,000 at $6.50 to $7.95 per sq. ft. However, the Sports Turf Managers Association prices synthetic infill systems at $6.50 to $11 per sq. ft., and conventional sand-based fields at $7 to $10 per sq. ft.
Case studies on annual maintenance would suggest that the amount spent on maintenance varies greatly with the level of athletics being supported. This makes it difficult to compare annual maintenance costs. Previous investigations have found that annual maintenance costs of natural grass systems ranges from $5,500 to $48,960. Annual maintenance on synthetic infill systems ranges from $5,000 to $29,000.
Resurfacing a synthetic field consists of removal and disposal of old carpet and infill material, additions of new material, and labor. In communication with local contractors the cost of resurfacing a synthetic infill system has been estimated to be $4.00 per sq. ft. for material and labor. The Synthetic Turf Council ranges the cost of transporting and landfilling the product from $30,000 to $60,000 for an 80,000 sq. ft. field ($0.38 to $0.75 per sq. ft.). For this study $.56 sq. ft. ($45,000/80,000 sq. ft.) was used to calculate disposal of synthetic infill material.
These installation and maintenance costs for synthetic infill and natural turfgrass systems have primarily been provided by industry sources and commodity groups. They were also not expansive enough to include the practice of resurfacing for either natural turfgrass or synthetic infill fields at multiple locations, or for facilities of different athletic levels in the same analysis. Another unexplored aspect in the literature is hours of player use. The question here is, “How many maintenance dollars are being used to provide an hour of use for an individual?”
Therefore, the objectives of this study were to: 1) compare the cost of installation and maintenance across a 20-year period, and 2) establish and compare a cost-per-hour of player use value for natural turfgrass and synthetic infill athletic fields.
Materials and methods
This case study assembles and compares the 20-year life-cycle costs of five natural turfgrass and five synthetic infill fields in the Willamette Valley, OR. Annual player-use data was collected on these fields to create to compare the cost efficiency of the 10 fields over their life cycles. This was accomplished by calculating the cost of providing one hour of use for a single individual [20 year life-cycle cost / (annual hours of individual use * 20 years)]. Surface temperature and hardness data were also collected monthly in 2014-2015 using the testing procedures found in ASTM F1963—10 standard procedures for field hardness testing and using a FieldScout TruFirm and Raytek non-contact thermometer. In order to represent a broader range of maintenance capabilities fields were selected for this study to cover maintenance levels from K-12 schools to the NCAA level.
Cost of installation
The overall average of natural grass athletic field installation, which includes three sand-based fields and two native soil fields, was $325,000 with a cost per square foot range of $1.50-$6.50. The average cost of installing the five synthetic infill fields was $1,212,000 with a cost per square foot from $12.50-$20.40. By comparison the average cost of natural grass installation was $887,000 less than the average cost of synthetic field installation. A possible reason for the larger values when compared to the literature is the cost of soil stabilization required for clay soils present at the sites.
Cost of maintenance
The average cost of a single year of maintenance for five natural grass fields was $35,000 while the average cost of a single year of maintenance for the 10 synthetic infill fields was $7,000. The average annual maintenance budget for natural grass fields was almost five times as much than the average annual maintenance for synthetic infill fields with a difference of $28,000.
Of the five natural grass fields only field 1, the university field, is on a schedule to be resurfaced. The cost includes removal of old surface, rolling, topdressing, and seeding. It is planned to be done every 5 years at the cost of $21,000. Re-carpeting of the five synthetic fields was planned for all fields after 8-10 years. The average cost of re-carpeting synthetic fields was $376,000.
The average cost of a 20-year maintenance cycle for the five natural grass fields was $903,000. The average cost of a 20-year maintenance cycle for the 10 synthetic infill fields was $1,952,000. The average on synthetic infill fields was two times as much the average for natural grass fields.
The calculated individual annual hours for the natural grass fields averaged 22,000 hrs. Expanded to the 20-year period the usage-hours were an average of 438,130 hrs. Similarly the synthetic fields averaged 22,000 hrs. The average annual hours of use on the synthetic fields was caused by low use on the high-school level field. Expanded to the 20-year period the usage-hours were an average of 1,402,000. Comparatively the average usage-hours on the synthetic fields for the 20-year period was three times as much than as on natural grass fields. The average cost to provide an individual with an hour of use for the five natural grass fields was $2.18. The average cost per individual player hour for the synthetic infill fields was $2.15. This figure emphasizes the importance of how necessary it is for synthetic fields to be adequately used. To be effectively used synthetic fields, with their life-cycle costs, need to be used for enough hours to be competitive with natural grass fields.
Firmness and temperature
The months of June and July were the hottest month during the data collection with the synthetic fields’ surface temperature measuring at over 140oF on the test points located in full sun. The hottest points on the natural grass fields’ surface temperature were up to 100oF, but these areas had been worn by traffic and recently sand and seeded, the unworn full sun areas were measuring in the 80’s.
Surface hardness on natural grass fields showed great variation during the rainy season from November through March with firmness levels reaching up to 1.5”of depression in poorly drained areas that could be judged unplayable. The synthetic fields in this study showed little variation in firmness even during the rainy season, maintaining a depression range between 0.2” and 1.0”.
The synthetic infill fields in this study were able to be as cost effect as natural grass with the player-hour use cost of 2.15 to the natural grass cost of 2.18 despite being twice as expensive over the 20-year period of analysis. This is likely to be credited to the synthetic fields’ ability to maintain surface quality with high levels of use and little impact from weather. The synthetic surfaces maintained consistent surface hardness through the rainy season while the natural grass fields varied in hardness with the rainy season, losing stability. These results support the idea that synthetic fields are able to be just as cost effective as natural grass fields, despite their larger costs, by providing greater amounts of player-use hours. It also suggests that if sufficient hours are used on the field it could potentially be a poor investment depending on the situation of the facility. For example, a high school football coach who wants to protect the field by not letting other groups use it would have would increase the cost per player-use hour.
Brian Daviscourt is a graduate assistant; Alec Kowalewski, PhD, is a turfgrass specialist; John Lambrinos, PhD, is a landscape ecologist; Bart Eleveld, PhD, is an agricultural economics specialist; and Micah Gould is a graduate assistant, all at Oregon State University in Corvallis.