LEXINGTON, KY (Aug. 28, 2014) – The conversion of Keeneland’s 1 1/16-mile main track from a synthetic Polytrack surface to a dirt surface represents more than a year of research by track officials and a team of experts who consulted with noted track specialist Dr. Mick Peterson, executive director of the Racing Surfaces Testing Laboratory, to conduct testing on materials, water drainage systems and race track design.
Dirt Surface a Native Kentucky Blend
A blend of approximately 19,000 tons of sand, silt and clay native to Kentucky forms the main track’s six-inch racing surface. The surface composition consists of approximately 87.5 percent sand and 12.5 percent clay and silt.
The dirt material was created by the Kentucky division of Martin Marietta Materials Inc., the nation’s second-largest producer of construction aggregates. Martin Marietta used materials mined in quarries near Petersburg, Ky., located on the Ohio River in Northern Kentucky, to develop the dirt blend.
The Lexington-based engineering firm S&ME Inc. observed the entire process and inspected the blended materials every 300 tons to ensure the composition of the dirt surface remained consistent. The finished material was then transported to Keeneland for installation.
Class I Sand Base
The base of the dirt track was formed by 26,000 tons of Class I sand. The depth of the Class I sand ranges from two inches at the rail to as much as 18 inches near the center of the track to form a crown and direct water toward the inside and outside rails.
The Class I sand rests atop 720,000 square feet of Mirafi 140N geotextile fabric. The geotextile fabric maintains the integrity of the Class I sand base and prevents it from migrating into the porous asphalt foundation.
New Drainage Features Work in Tandem with Existing Drainage System
Unique components create a one-of-a-kind water drainage system for the dirt track. A design featuring interlocking EcoRain drainage cells filled with pea gravel and topped by a flexible porous paving material along the rails works in tandem with the drainage system installed beneath the track during the 2006 renovation to collect and discharge water.
EcoRain Drainage Cells
A total of 27,500 interlocking EcoRain drainage cells were stacked horizontally under the inside rail and along the outside rail through the straights and chutes of the track.
Made of 100 percent recycled polypropylene material, the cells measure two inches in height and are filled with pea gravel. This design feature mimics natural groundwater infiltration, allowing water to consistently pass through and into the system below and eliminate ponding on the track surface.
The cells are manufactured by California-based EcoRain Systems, which also produces large underground water detention basins. The cells are used in a variety of applications, including retaining walls, athletic fields, roadways, airport runways and roof gardens.
Flexible Porous Paving Material
The EcoRain drainage cells are topped by two inches of flexible porous paving material.
Composed of 100 percent recycled tires, the flexible porous paving material allows thousands of gallons of groundwater and stormwater to be discharged per hour, efficiently ushering water away from the surface while also controlling erosion.
A total of 11,400 linear feet was installed, equal to 6,301 tires.
Environmentally friendly, the material cleans the water as it passes through, reducing dissolved nitrates and phosphates. It is currently in use at golf courses, public parks, trails and paths and parking lots across the country.