A synthetic grass assembly for installation on a supporting soil substrate includes a pile fabric with a flexible sheet backing and rows of upstanding synthetic ribbons representing grass blades, extending upwardly from an upper surface of the backing. An infill layer of two distinct graded courses of particulate material is disposed interstitially between the upstanding ribbons upon the upper surface of the backing and of a depth less than the length of the ribbons. A bottom course of intermixed hard sand and resilient rubber granules with substantially identical particle size distribution characteristics is installed upon the backing and a top course exclusively of resilient rubber granules is placed upon the bottom course.