Product Manual

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2004 Revision of the USGA Recommendations for a Method
of Putting Green Construction*
Mater
ial
Description
Gravel: Intermediate layer is
used
Not more than 10% of the particles greater than 1/2"
(12mm)
Gravel: Intermediate layer is
used
At least 65% of the particles between 1/4" (6mm)
and 3/8" (9mm)
Gravel: Intermediate layer is
used
Not more than 10% of the particles less than 2 mm
Intermediate Layer Material At least 90% of the particles between 1 mm and 4
mm
Performance Factors Recommendation
Bridging Factor D15 (gravel) less than or equal to 8 X D85 (root zone)
Permeability Factor D15 (gravel) greater than or equal to 5 X D15 (root zone)
Uniformity Factors D90 (gravel) / D15 (gravel) is less than or equal to 3.0
Uniformity Factors
No particles greater than 12 mm
Uniformity Factors
Not more than 10% less than 2 mm
Uniformity Factors
Not more than 5% less than 1 mm
A. Selection and Placement of Materials When the Intermediate Layer Is Used
Table 1 describes the particle size requirements of the gravel and the intermediate layer material when
the intermediate layer is required.
The intermediate layer shall be spread to a uniform thickness of two to four inches (50 to 100 mm) over
the gravel drainage blanket (e.g., if a 3-inch depth is selected, the material shall be kept at that depth
across the entire area), and the surface shall conform to the contours of the proposed finished grade.