Turf, whether natural grass or synthetic, gets wet when exposed to rain, irrigation, or dew. The fundamental difference lies in how these surfaces manage water. Natural grass fields absorb moisture into the soil and plant structure, while synthetic turf is a manufactured material designed to shed water. Understanding this distinction and the engineered systems required for artificial surfaces is necessary to evaluate the consequences of water exposure.
How Turf Materials Handle Water
Natural grass utilizes capillary action, where water adheres to soil particles and moves upward, while plant roots absorb water and release it through transpiration. This mechanism allows the field to function like a sponge, holding large volumes of moisture within the soil profile. This natural absorption also helps regulate the field’s temperature through evaporative cooling.
In contrast, synthetic turf fibers are constructed from hydrophobic polymers like polyethylene or polypropylene, which repel water molecules. Since the plastic fibers do not absorb water, moisture rests on the surface or flows down the blades. This non-absorbent nature requires a completely different strategy for water management.
The infill material provides ballast and cushioning between the fibers but exhibits limited absorption compared to organic soil. Common infills, such as crumb rubber or silica sand, are porous to allow for drainage, not absorption. While some newer infills retain a small amount of moisture for evaporative cooling, the bulk of the water must be actively drained away.
Engineered Water Removal Systems
Since synthetic materials cannot absorb water like soil, the field relies on a comprehensive, engineered sub-base system to manage precipitation. The turf carpet is manufactured with a perforated backing, featuring small holes to allow water to pass through. This perforated layer is the initial point of drainage, directing all surface water downward.
Beneath the turf, a deep aggregate sub-base, composed of layers of crushed stone or gravel, facilitates rapid vertical filtration. This stone base is often installed in layers, creating a highly permeable foundation. This structural layer provides stability and acts as a reservoir for water flow.
The entire sub-base is constructed with a precise grade or slope to guide the filtered water laterally toward perimeter drainage systems. These systems usually consist of perforated pipes or trench drains installed around the edge of the field. This infrastructure ensures the surface drains quickly, even during heavy rainfall events.
Operational Impact of Wet Surfaces
When synthetic turf becomes saturated, the operational characteristics of the field change, particularly impacting player safety and ball dynamics. The coefficient of friction (CoF), which measures the resistance to sliding, is generally higher on dry synthetic turf compared to natural grass. When the turf is wet, this CoF decreases significantly, sometimes dropping from a maximum of 0.65 dry to as low as 0.16 saturated.
This reduction in friction causes the surface to become slicker, increasing the risk of slips and falls. The performance of the ball is also affected, though less dramatically than on a waterlogged grass field. Studies indicate that a soccer ball’s roll distance on wet synthetic turf is only slightly longer, by about 0.3 meters, compared to its roll on a dry field.
Wetting the surface has a temporary effect on the field’s thermal properties. Synthetic turf retains solar energy, leading to high surface temperatures. Applying water causes temporary cooling through evaporation, but this effect is short-lived. Surface temperatures can quickly rebound, returning to levels above 120°F within 90 minutes after irrigation ceases.
Moisture and Microbial Concerns
The moisture trapped within the turf system, specifically in the infill layer and backing material, creates an environment conducive to biological growth. The combination of warmth, moisture, and organic debris accumulating on the field can lead to the formation of mold and mildew. This fungal growth is often visible as discoloration or detected by a musty odor.
Of greater concern are pathogenic bacteria, such as Staphylococcus aureus, which thrive in warm, moist environments. These bacteria can be transferred through skin abrasions, commonly known as turf burn, if the field is not regularly maintained. Moisture retention in the infill facilitates the longevity of these microorganisms.
To mitigate these risks, field operators must employ specific sanitation and maintenance protocols. This includes regular grooming to redistribute the infill and prevent compaction, which aids drainage and aeration. Specialized disinfectants and sanitizers are also applied to the surface to control bacterial and fungal populations, ensuring a hygienic playing environment.