How Green is Your Sport Field Grass?

Synthetic Surface Sport Fields for Water Conservation & Long-Term Carbon Footprint Reduction

Sustainability experts typically agree on two measures for high performance sport fields: total fresh water saved, and net reduction in carbon footprint with all factors considered over the life cycle of the sports field.

So, what are the water conservation features for synthetic surface sport fields, and what other factors determine how green your sport field grass is? Before outlining features and factors to consider, we’ll take a look at a project at Western Washington University that is an example of a high performance sports field design with synthetic surface fields that are truly greener, including high performance for water conservation.

“If the design and specification is done right, all-weather synthetic surface fields including adequate subsurface drainage will minimize runoff. This is especially important at our Western Washington University (WWU) campus in Bellingham, Washington in the Pacific Northwest,” says Linda Beckman, Vice President for Student Affairs at WWU. “Ideally, synthetic surface will be selected for high recycled content, as a low-VOC product for air quality concerns, and will be maintained properly. Upfront, we decided to fund proper maintenance and also decided it will be recycled when it nears the end of its life, and to select a consultant who understands the full picture of environmental performance from products and systems. Our Pacific Northwest strong environmental commitment is met by using the sport field surface system we approved—we did it right and we did it green.”

In 2011, WWU selected Erik Sweet, RLA, ASLA, of SLA Landscape Architecture as the project landscape architect and project manager for a sport field master plan under a phased design services agreement. He is a registered landscape architect in five states who works mostly within the region for municipal and education sports facility projects. He also travels outside the region to serve professional and major league sports clients.

At the consultant selection stage, WWU took full advantage of all the latest technical information. Erik participated as session panelist at ASLA’s Annual Meeting in Washington, DC in 2010 along with leading industry experts. He is an international sports field design expert who speaks nationally on this topic to ASLA members as well as to Synthetic Turf Council members and locally at Washington Parks and Recreation Association events. Having a landscape architect like Erik Sweet who also played professional soccer internationally, is a national subject matter expert, and volunteers as a referee and a coach did not hurt WWU’s chances for a high performance sport field design.

The WWU campus project demonstrates high water savings in a mild climate zone, with a proposal of four fields in synthetic surfaces that save 90% of water compared to turf. And, at the WWU campus scale, intramural sport participation is approximately 50% of undergraduate student population, so a lighted synthetic all-weather field creates a net positive return on investment over the 10-year life cycle compared to natural turf maintenance expenses, factoring in replacements for both types of field surface systems.

Outlined below are features and factors to consider for synthetic surface sport fields:

Water & Energy

• Source of irrigation water—using treated drinking water from municipal sources during peak times might be problematic. Raw water from shallow wells, ponds, or reclaimed water has less embedded energy compared to pumped, treated, potable water conveyed over large distances. Saving water to save energy is the front edge of best practice in the western US.
• Annual water use—an 80% reduction in water use is common with a typical all-weather turf field. Natural turf typically requires 15 inches of precipitation based on evapotranspiration rates, added to the 38 inches annually of rain and snow, although the normal pattern varies widely.
• Stormwater runoff—synthetic surface placed over a compacted rock drainage layer enables some infiltration. Runoff impacts from a synthetic field are typically less for volume, intensity, time of concentration, and sedimentation compared to natural turf fields. Water quality impacts for synthetic fields are all positive with no silt, fertilizer, herbicides, or pesticides compared to natural turf. In Washington state, the local regulations categorize synthetic sport surfaces as impervious surfaces for stormwater permits. Natural turf may or may not require review.

Materials

• Composition of surface—considering using recycled materials? One example has 30% recycled content. Fossil fuels used in re-manufactured surfacing needs total process life cycle analysis.
• Potential health problems from emissions and heavy metals in some chemical constituents in the plastic and rubber—outdoor vs. indoor fields differ among available synthetic products, and the release of materials varies with field surface temperatures. Typically, outdoor synthetic fields in the Pacific Northwest experience temperatures that do not degrade component elements when users are on the fields.
• Disposition of surface—landfill or recycle? End of design life requires a choice. Since the 1960’s, synthetic surfaces were 100% landfilled at the end of lifespan until new options recently emerged.

Life Cycle Costs & CO2 Considerations

• Though synthetic turf has a higher initial cost (approximately 2x higher compared to natural turf), it has a lower long-term life cycle cost (over 10-, 12-, or 15-year life spans), which results in a smaller lifetime environmental footprint compared to natural grass.
• More hours of play per field for synthetic fields with night lighting compared to grass. Less land is developed, resulting in less total impervious surface coverage to meet the total regional active sport demand.
• Having grass fields necessitates the use pesticides and herbicides, plus fossil fuel energy for mowing and watering. These annual costs and environmental impacts are eliminated with synthetic surface fields.
• Grass has a fairly short carbon dioxide (CO2) cycle from growth to decomposition with the release of CO2, and an emission rate factor should be part of environmental reviews.

by Matt Mathes, PLA, ASLA, Water Conservation PPN Co-Chair

images by SLA Landscape Architecture