Synthetic Turf - Questions and Answers

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Portland Parks & Recreation (PP&R) is responsible for providing all Portlanders with recreational opportunities that are safe and reliable. Safety is our top priority.
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Evaluating Synthetic Turf and Infill Sports Fields  |  July 2016

Portland Parks & Recreation (PP&R) is responsible for providing all Portlanders with recreational opportunities that are safe and reliable. Safety is our top priority.

Considerations of safety include looking at the composition of the materials we put in our parks, their durability to withstand thousands of hours of play time, and their ability to be maintained in a safe and responsible manner. All of these factors are considered when we make decisions about the assets we build into our parks.

PP&R is paying close attention to the national conversation about our best options for artificial turf fields. 

PP&R has been installing synthetic turf fields for more than fifteen years. Our first artificial turf field—Strasser Field at Delta Park—was installed in 1997 and was the company Field Turf’s first outdoor field in the world. Since that time, we have refined our construction specifications for installation and materials to improve the quality and safety of our fields. We require that the post-consumer recycled tire crumb rubber be sourced in the U.S., we specify that lead levels must be within the limits established by the EPA, and we follow the most recent research on synthetic turf infill materials. Current research around post-consumer tire crumb rubber does not confirm a concerning level of exposure to chemicals, however some believe that more research needs to be completed. PP&R will continue to monitor this research.

Following these specifications and continuing research, PP&R will continue to provide synthetic turf fields in our system that includes the use of crumb rubber infill. Our decision is based on the current information gathered (summarized below) about possible options for synthetic turf infill.

Questions & Answers

1. How do PP&R fields get used?

PP&R’s goal is to provide broad access to recreation, for everyone.

  • We have both formal and casual use of our fields and there is an increasing demand for both.
    • Formal users need a field to be available for reliable play during a specific timeframe and often reserve fields ahead of time through a recreation permit. Portlanders participate heavily in organized sports leagues, resulting in many hours of field reservations.
    • Casual use happens without a reservation ahead of time, with park visitors often playing spontaneous pickup games, or just kicking a ball around with their families and friends.

2. What are the benefits and challenges of managing living grass turf?

Some benefits to living grass fields include:

  • They last about 20 years with regular maintenance and reseeding
  • They function as carbon sinks
  • They filter storm water
  • Their installation cost is lower
  • They absorb heat on hot days

Some challenges to living grass fields include:  

  • They have a limited playing season. Playing on a saturated, soggy field, damages the surface and the grass.  PP&R closes fields seasonally and during heavy rain to prevent major damage.
  • They are less safe when played on in the rain; they become muddy and uneven.
  • Even in dry weather, they become compacted and rutted at the end of the season and the risk for sports injuries goes up.
  • They require regular intensive maintenance, mowing, irrigation, and weed management, reseeding worn spots, aeration of compacted soils, regrading rutted surfaces, etc.
  • They need to rest between play to allow the grass to recover

3. What is synthetic turf?

Synthetic turf consists of a top layer of artificial turf carpet with a granule infill material to support the synthetic grass blades.

Synthetic turf infill:

  • Fills the voids among the blades of synthetic turf, supports the blades of synthetic turf (keeping them upright), and evens the playing surface
  • Adds weight to the playing surface
  • Protects the yarn of the artificial turf carpet
  • Gives the playing field softness/cushioning and the ability to absorb the shock of someone falling on it, which lessens the chances of injury (the lower a field’s shock absorption rating [G-Max], the softer the field)

Below the carpet and infill, there is a subsurface drainage layer composed of crushed stones with plastic tubing for drainage.

Of the existing synthetic turf fields available for permit in PP&R’s system, six are made with a post-consumer recycled tire crumb rubber (SBR), the most common infill used and industry standard. Two other PP&R synthetic fields contain Nike Grind infill or post-industrial grind. PP&R has considered other infill options. See below for more information on our evaluation of those options.

4. What are the benefits of synthetic turf?

Synthetic turf has a life cycle of eight to 12 years, with potential for recycling or reuse in other applications.

Benefits of synthetic turf in the Portland climate include the fact that the turf addresses very high demand for formal use of athletic sports fields. Including:

  • More hours of continuous play time to meet demand
  • Year-round play without damaging fields
  • Less maintenance
  • Good playability (G-Max ratings):  The safety of our users is our top priority; playability refers to a playing field’s cushioning and its ability to absorb shock of a fall, lessening chance of injury both in the short term and over time
  • Increase in number of hours a field can be reserved increases the revenue to the parks department for covering costs

5. How much more play time do you get with synthetic turf?

Below is an industry-standard graphic that also reflects Portland’s experience.

Sports Field Playability by Month. Synthetic Turf 3000 hours vs Living Grass 816 hrs

6. Are there concerns with synthetic turf?

The most frequent concern cited is that the post-consumer recycled tire crumb rubber infill (SBR) may result in chemical exposure.

Chemical exposure and any possible related health concern are important considerations for any materials used in our parks. Other criteria for evaluation include: environmental impacts, recreation value, and the costs of construction and maintenance.

PP&R has completed substantial research on these criteria for post-consumer recycled crumb rubber as well as other possible infill materials. See the following questions for more information.

7. How did PP&R evaluate synthetic turf infill options?

PP&R‘s steps for evaluating infill options are:

1. Research infill options currently on the market.

2. Identify criteria for material selection:

    • Health: Health and safety impacts to users
    • Environment: Environmental impacts
    • Recreation Value: Recreational  value including quantity and quality of play time
    • Cost: Ongoing maintenance costs and lifecycle cost (installation and replacement)

3. Survey other recreation providers in the Pacific Northwest; understand how alternative infills perform in our climate.

8. What are the considerations for evaluating infill materials?

1. Health

  • Chemical Exposure – are there chemicals notably present in materials and are they in a form that will result in unhealthy levels of exposure to players and spectators?
  • Sports Injuries – do injuries result due to playing on these materials? Are the risks manageable through maintenance?
  • Heat Exposure – does the surface of the field absorb and radiate heat at a higher temperature on warmer days such that heat could impact a player’s health?

2. Environment

  • Carbon Footprint – what is the sourcing, manufacturing, and shipping of materials? Do they off-gas? Can the material absorb and hold carbon as a sink?
  • Water Consumption – does the maintenance of the field require significant irrigation?
  • Recycled or Recyclable – are materials infinitely reusable and recyclable?

3. Recreation Value:

  • Hours of Play Available – are the fields available to play on at most times?
  • Reliable Playability – are the fields prone to interruptions in their playability, needing repairs or closures?

4. Cost:

  • Installation and Replacement – what are the cost of installation and major replacements?
  • Annual Maintenance Cost – what are the annual maintenance tasks & costs?
  • Total Cost Over 20 Years – what is the 20-year lifecycle cost?

9. What infill options for Synthetic Turf Infill did PP&R evaluate?

The infill options that PP&R evaluated include:

1. Petroleum-based infills

  • Post-Consumer Tire Crumb Rubber (SBR) – both shredded and cryogenically frozen
  • Post-Industrial Product Grinds (Nike Grind for example)
  • New Synthetic Crumb Rubber (EPDM)
  • New Plastic Crumb Thermoplastic Elastomer (TPE)
  • New Acrylic Polymer Coated Sand

2. Sand infill

  • Silica Sand (Post Industrial application)

3. Plant-based infills

  • Coconut Fiber & Cork Mix
  • Coconut Fiber
  • Cork

10. What did PP&R learn in the evaluation of infill options?

The chart below outlines the evaluation of infill options. Overall, no infill option reaps all of the benefits or reaps all of the concerns. Based on the information below, PP&R has concluded that for our climate, while we will continue to keep many grass fields, where demand requires artificial turf, Post-Consumer Tire Crumb Rubber (SBR) and New Synthetic Crumb Rubber (EPDM) are the most manageable infill options at this time.

The chart below will be continuously updated as additional information becomes available from research, partners and regional parks systems, and other data sources.

Comparison of Synthetic Turf Infill Materials

11. How do the different infill options compare?

1. Petroleum-Based infills: Recycled

  • Post-Consumer Tire Crumb Rubber and Post-Industrial Grind are made from materials that have been processed into small crumbs for use in synthetic turf fields as the infill material.
  • Research around Post-Consumer Tire Crumb Rubber does not confirm a concerning level of exposure to chemicals. However, many feel that there is also more research that can be done—PP&R will continue to monitor any research.
  • Heat can sometimes be an issue with the recycled materials. In Portland, we have fewer days of extreme heat and heat concerns can be managed with field closures in extreme cases.

2. Petroleum-Based infills: New

  • New synthetic infills are specifically designed for sports field infills.  
  • Some new petroleum-based materials are designed with lighter color that helps to reduce heat absorption.
  • The new petroleum-based infills are much more expensive than recycled petroleum-based infill.  Upwards of three to five times the cost of post-consumer recycled tire crumb rubber.
  • New petroleum-based infills have a significant carbon footprint and a greater environmental impact

All the petroleum-based infills have some potential for reuse as infill after the turf carpet is replaced (and recycled)—recycling can sometimes be more expensive than purchasing new infill.

3. Sand infill (PP&R evaluated sand as a standalone infill material):

  • Heat can be an issue
  • Considerable environmental impact due to product weight and transportation distances
  • Chemical exposure can be a concern with some sands due to silica dust content. Engineered sand available from post industrial applications has a reduced amount of silica dust. Local sources of possible sand infill needs further exploration to reduce costs and carbon footprint of this material.
  • Sand compacts more than other infills creating a hard playing surface that is less desirable in the long run and can result in additional sports injuries.

4. Plant-Based infill:

  • Minimal health concerns
  • Significant environmental impact due to growing, harvesting, and transporting non-local materials (e.g., coconut fiber, cork)
  • Coconut fiber requires watering to function properly as an infill
  • The plant-based materials are reusable as landscape materials after their life in the field
  • The hours of play available and reliable playability are slightly less than the petroleum-based infills due to effect of weather events
  • Some additional maintenance may be required in our climate –for example, organic materials may break down more quickly in our wet weather, and cork may float away in heavy rain events.
  • Replacement is needed every two to three years and the material breaks down much faster. Ultimately, the cost of the plant-based materials is significantly higher at install and replacement points.

We will continue to monitor scientific findings on turf products and we will adjust our approach according to best practices as they evolve. 

12. What are other agencies and parks districts in the Pacific Northwest doing with their synthetic sports fields?

The majority of neighboring jurisdictions have Post-Consumer Recycled Tire Crumb Rubber (SBR) as infill material in their synthetic turf fields.

They have found with their synthetic turf fields that:

  • Maintenance costs are greatly reduced
  • Playability and hours available increase
  • Revenue goes up

Seattle Parks has 80 synthetic turf fields, the majority of which are made with SBR infill. Seattle will be piloting one field with a cork and sand mix. PP&R will be looking to this pilot project to see what the outcomes are and how the field performs.

13. What are PP&R’s plans for converting growing grass fields to Synthetic Turf?

Portland Parks currently has 180 growing grass fields in its system and 8 synthetic turf fields that it manages reservations for. There will always be a place in the parks system for natural growing grass as synthetic turf fields are not appropriate in all situations.  However, in some cases where a high demand for sports field’s reservations and field sports play exists, synthetic turf fields will be considered as a solution.

To learn more about current field improvement projects in the parks system [click here to] visit the Portland parks projects webpage.

14. What are PP&R’s resources for this research?
SYNTHETIC TURF INFILL RESEARCH SOURCES -- As of July 2016

CITY OF PORTLAND STAFF SPECIALIST SOURCES
  • Irrigation Specialists
  • Recreation Managers for organized sports
  • Natural Turf maintenance specialists
  • Field and Park Managers
  • Bureau of Environmental Services
NEIGHBORING PARKS AND SCHOOL JURISDICTIONS - PHONE INTERVIEWS
  • City of Tualatin Hills, OR
  • City of Salem, OR
  • West Linn - Wilsonville School District, OR
  • City of Ashland, OR
  • City of Hillsboro, OR
  • City of Tigard, OR
  • Clark County, WA
  • City of Oregon City, OR
  • City of Seattle, WA
  • City of Gresham, OR
  • City of Vancouver, BC
  • City of Olympia, WA
  • City of Vancouver, WA
  • City of Tacoma, WA
  • City of Eugene, OR
  • City of Bellingham, WA
  • City of Corvallis, OR

Research and reports by other jurisdictions, agencies, cities, states, and countries:

Reports, Studies, and Published Papers:

  • Benetti, Mickael & Loubersac, Guillaume. FieldTurf Technical Report: Toxicological Analysis of Performance Infill for Synthetic Turf Fields According to EN 71-3 Standard – Safety of Toys Part 3: Migration of Certain Elements. LaboSport. December 12, 2014.
  • Gentile, Jeffrey. Laboratory Testing Heavy Metals Analysis. Greenplay Toxicology, Metals, Volatiles, Semivolatiles. Sports Labs USA. September 3, 2015.
  • Gentile, Jeffrey. Laboratory Testing Performance Evaluation. Greenplay - Geoturf Impact Comparison. Sports Labs USA. December 2, 2015.
  • Gerry-Zink, Stephanie. A Natural Debate. PRB: Parks & Rec Business. http://parksandrecbusiness.com/archives/facilities-grounds-sports-turf/a-natural-debate/.  November 2008. 
  • Green, Laura, C, Ph.D., D.A.B.T. Comment on CPSC Report #20150608-22F81-2147431268 Assessment of the Risk of Cancer Posed by Rubber Mulch Used in Playgrounds. Memorandum to Jonesport Elementary School.  June 29, 2015.
  • Green, Laura, C, Ph.D., D.A.B.T. Assessment of Recent Media Reports of Cancer Among Soccer Players Using Synthetic Turf Fields. Memorandum to Phil Barlow, Shaw Industries. March 4, 2015.
  • Meil, J and Bushi, L. Estimating the required global warming offsets to achieve a carbon neutral synthetic field turf system installation. Athena Institute, 2007. http://www.athenasmi.org/wp-content/uploads/2012/01/UCC_project_ATHENA_technical_paper.pdf
  • O’Donnell, Kiernan. Laboratory Testing Temperature and Water Loss Evaluation. Greenplay SBR Rubber vs Natural Grass. Sports Labs USA. November 12, 2015.
  • Penn State’s Center for Sports Surface Research, Synthetic Turf Heat Evaluation – Progress Report, http://plantscience.psu.edu/research/centers/ssrc/documents/heat-progress-report.pdfJanuary, 2012
  • Rossi, Frank, Ph.D.  Cornell Turfgrass Program Webpage. Cornell University.  http://www.hort.cornell.edu/turf/.
  • Simon, R. Review of the impacts of crumb rubber in artificial turf applications. University of California, Berkeley, February 2010.
  • Synthetic (artificial) turf vs. natural grass athletic fields, University of Arkansas Division of Agriculture. http://turf.uark.edu/turfhelp/archives/021109.html
  • United States Environmental Protection Agency, A scoping-level field monitoring study of synthetic turf fields and playgrounds, http://www.epa.gov/nerl/download_files/documents/tire_crumbs.pdf, 2009.

News Reports and Videos:

Synthetic Turf Suppliers and Material Information:

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