The playing surface of PNC Park is Tuckahoe Bluegrass, which is a mixture of various types of Kentucky Bluegrass.[92] Installed before the 2009 season, the grass surface was selected for its "high-quality pedigree that is ideal for Northern cities such as Pittsburgh".[92] The infield dirt is a mixture known as "Dura Edge Custom Pro Infield Mix" and was designed solely for PNC Park.[92] The 18-foot (5.5 m) warning track is crushed lava rock.[92][93] The drainage system underneath the field is capable of handling 14 inches (36 cm) of rain per hour.[94] The original playing surface consisted of sand-based natural grass,[95] and was replaced before the 2006 season.[92] The playing surface also underwent a significant renovation following the 2016 season.