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Recommendations For A Method Of Putting Green Construction
by the USGA Green Section Staff
Please note that you may need to consult with your Agricultural Extension Agent and or the USGA when using these instructions.
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Following is the 1993 revision of the USGA Recommendations for
a Method of Putting Green Construction.
Step 1. The Subgrade
The slope of the subgrade should conform to the general slope of
the finished grade. The subgrade should be established approximately
16 inches (400 mm) below the proposed surface grade - 18 to 20
inches (450 to 500 mm) when an intermediate layer is necessary - and
should be thoroughly compacted to prevent further settling. Water
collecting depressions should be avoided.
If the subsoil is unstable, such as with an expanding clay, sand,
or muck soil, geotextile fabrics may be used as a barrier between
the subsoil and the gravel blanket. Install the fabric as outlined
in Step 2.
Construct collar areas around the green to the same standards as
the putting surface itself.
Step 2. Drainage A subsurface
drainage system is required in USGA greens. A pattern of drainage
pipes should be designed so that the main line(s), with a minimum
diameter of 4 inches (100 mm), is placed along the line of maximum
fall. Four-inch (100 mm) diameter laterals shall run up and across
the slope of the subgrade, allowing a natural fall to the main line.
Lateral lines shall be spaced not more than 15 feet (5 m) apart and
extended to the perimeter of the green. Lateral lines should be
placed in water-collecting depressions, should they exist. At the
low end of the gradient, adjacent to the main line's exit from the
green, drainage pipe should be placed along the perimeter of the
green, extending to the ends of the first set of laterals. This will
facilitate drainage of water that may accumulate at the low end of
that drainage area. Drainage design considerations should be given
to disposal of drainage waters away from play areas, and to the laws
regulating drainage water disposal. PVC or corrugated plastic
drainage pipe is preferred. Where such pipe is unavailable, clay or
concrete tile is acceptable. Waffle drains or any tubing encased in
a geotextile sleeve are not recommended. Drainage trenches 6 inches
(150 mm) wide and a minimum of 8 inches (200 mm) deep shall be cut
into a thoroughly compacted subgrade so that drainage lines slope
uniformly. Spoil from the trenches should be removed from the
subgrade cavity, and the floor of the trench should be smooth and
clean. If a geotextile fabric is to be used as a barrier between an
unstable subsoil and the gravel drainage blanket, it should be
installed at this time. Under no circumstances should the fabric
cover the drainage pipes or trenches. A layer of gravel (see Step 3
for size recommendations) should be placed in the trench to a
minimum depth of 1 inch (25 mm). It may be deeper, as necessary, to
ensure a positive slope along the entire run of drainage lines. If
cost is a consideration, gravel sized 1/4 to 1 inch (6 to 25 mm) may
be used for the drainage trench only. All drainage pipe should be
placed on the gravel bed in the trench, assuring a minimum positive
slope of 0.5 percent. PVC drain pipe, if used, should be placed in
the trench with the holes facing down. Backfill with additional
gravel, taking care not to displace any of the drainage pipe.
Step 3. Gravel and Intermediate
Layers Place grade stakes at frequent intervals over the
subgrade and mark them for the gravel drainage blanket layer,
intermediate layer (if included), and root zone layer.
The entire subgrade then shall be covered with a layer of clean,
washed, crushed stone or pea gravel to a minimum thickness of four
inches (100 mm), conforming to the proposed final surface grade to a
tolerance of ± l inch.
Soft limestones, sandstones, or shales are not acceptable.
Questionable materials should be tested for weathering stability
using the sulfate soundness test (ASTM C-88). A loss of material
greater than a 12% by weight is unacceptable.
The LA Abrasion test (ASTM C-131) should be performed on any
materials suspected of having insufficient mechanical stability to
withstand ordinary construction traffic. The value obtained using
this procedure should not exceed 40. Soil engineering laboratories
can provide this information.
The need for an intermediate layer is based on the particle size
distribution of the root zone mix relative to that of the gravel.
When properly sized gravel (see Table 1) is available, the
intermediate layer is not necessary. If the properly sized gravel
cannot be found, an intermediate layer must be used.
PARTICLE SIZE DESCRIPTION OF GRAVEL AND
INTERMEDIATE LAYER MATERIALS
layer is used
||Not more than 10% of the
particles greater than 1/2" (12mm)
||At least 65% of the particles
between 1/4" (6mm) and 3/8" (9mm)
||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
SIZE RECOMMENDATIONS FOR GRAVEL WHEN INTERMEDIATE
LAYER IS NOT USED
||D15 (gravel) less than or equal
to 5 X D85 (root zone)
||D15 (gravel) greater than or
equal to 5 X D15 (root zone)
||D90 (gravel) / D15 (gravel) is
less than or equal to 2.5
||No particles greater than 12 mm
||Not more than 10% less than 2
||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
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.
B. Selection of Gravel When the Intermediate Layer Is Not Used
If an appropriate gravel can be identified (see Table 2), the
intermediate layer need not be included in the construction of the
green. In some instances, this can save a considerable amount of
time and money.
Selection of this gravel is based on the particle size
distribution of the root zone material. The architect and/or
construction superintendent must work closely with the soil testing
laboratory in selecting the appropriate gravel. Either of the
following two methods may be used:
- Send samples of different gravel materials to the lab when
submitting samples of components for the root zone mix. As a
general guideline, look for gravel in the 2 mm to 6 mm range. The
lab first will determine the best root zone mix, and then will
test the gravel samples to determine if any meet the guidelines
- Submit samples of the components for the root zone mix, and
ask the laboratory to provide a description, based on the root
zone mix tests, of the particle size distribution required of the
gravel. Use the description to locate one or more appropriate
gravel materials, and submit them to the laboratory for
Gravel meeting the criteria below will not require the
intermediate layer. It is not necessary to understand the details of
these recommendations; the key is to work closely with the soil
testing laboratory in selecting the gravel. Strict adherence to
these criteria is imperative; failure to follow these guidelines
could result in greens failure.
The criteria are based on engineering principles which rely on
the largest 15% of the root zone particles "bridging" with the
smallest 15% of the gravel particles. Smaller voids are produced,
and they prevent migration of root zone particles into the gravel
yet maintain adequate permeability. The D85 (root zone) is defined
as the particle diameter below which 85% of the soil particles (by
weight) are smaller. The D15 (gravel) is defined as the particle
diameter below which 15% of the gravel particles (by weight) are
- For bridging to occur, the D15 (gravel) must be less
than or equal to five times the D85 (root zone).
- To maintain adequate permeability across the root
zone/gravel interface, the D15 (gravel) shall be greater than or
equal to five times the D15 (root zone).
- The gravel shall have uniformity coefficient (Gravel
D90/Gravel D15) of less than or equal to 2.5.
Furthermore, any gravel selected shall have 100% passing a 1/2"
(12 mm) sieve and not more than 10% passing a No. 10 (2 mm) sieve,
including not more than 5% passing a No. 18 (1 mm) sieve.
Step 4: The Root Zone Mixture
Sand Selection: The sand used in a USGA root zone mix shall
be selected so that the particle size distribution of the final
root zone mixture is as described in Table 3.
PARTICLE SIZE DISTRIBUTION OF USGA ROOT ZONE MIX
||Recommendation (by weight)
||2.0 - 3.4 mm
||Not more than 10%
of the total particles in this range, including a maximum of 3%
fine gravel (preferably none)
|Very coarse sand
||1.0 - 2.0 mm
||0.5 - 1.0 mm
||Minimum of 60% of
the particles must fall in this range
||0.25 - 0.50 mm
||0.15 - 0.25 mm
||Not more than 20% of the
particles may fall within this range
|Very Fine Sand
||0.05 - 0.15 mm
||Not more than 5%
||0.002 - 0.05 mm
||Not more than 5%
||less than 0.002 mm
||Not more than 3%
||Very fine sand + silt + clay
||Less than or equal to 10%
Soil Selection: If soil is used in the root zone mix, it
shall have a minimum sand content of 60%, and a clay content of 5%
to 20%. The final particle size distribution of the sand/soil/peat
mix shall conform to that outlined in these recommendations, and
meet the physical properties described herein.
Organic Matter Selection: Although the USGA encourages the
use of organic matter in root zone mixtures due to its beneficial
properties, it is recognized that some sands may meet the particle
size and physical properties guidelines without modification.
Therefore, the guidelines no longer specify a minimum organic matter
percentage. Note: Since such sands rarely occur, the vast majority
of sands must be modified with organic matter to meet the required
Peats - The most commonly used organic component is a
peat. If selected, it shall have a minimum organic matter content of
85% by weight as determined by loss on ignition (ASTM D 2974-87
Other organic sources - Organic sources such as rice
hulls, finely ground bark, sawdust, or other organic waste products
are acceptable if composted through a thermophilic stage, to a
mesophilic stabilization phase, and with the approval of the soil
physical testing laboratory. Composts shall be aged for at least one
year. Furthermore, the root zone mix with compost as the organic
amendment must meet the physical properties as defined in these
Composts can vary not only with source, but also from batch to
batch within a source. Extreme caution must be exercised when
selecting a compost material. Unproven composts must be shown to be
non-phytotoxic using a bentgrass or bermudagrass bioassay on the
Inorganic and Other Amendments: Inorganic amendments
(other than sand), polyacrylamides, and reinforcement materials are
not recommended at this time in USGA root zone mixes.
Physical Properties of the Root Zone Mix: The root zone
mix shall have the properties summarized in Table 4, as tested by
USGA protocol (proposed ASTM Standards).
PHYSICAL PROPERTIES OF THE ROOT ZONE MIX
||35% - 55%
||15% - 30%
||15% - 25%
||6-12 inches/hr (15-30 cm/hr)
||12-24 inches/hr (30-60 cm/hr)
Under the heading Saturated Conductivity in Table 4,
Normal range refers to circumstances where normal conditions
prevail for growing the desired turfgrass species. Accelerated
range refers to conditions where water quality is poor, cool
season turfgrass species are being grown out of range of adaptation,
or dust storms or high rainfall events are common.
IT IS ABSOLUTELY ESSENTIAL TO MIX ALL ROOT ZONE COMPONENTS
OFF-SITE. No valid justification can be made for on-site mixing,
since a homogeneous mixture is essential to success.
A QUALITY CONTROL PROGRAM DURING CONSTRUCTION IS STRONGLY
RECOMMENDED. Arrangements should be made with a competent
laboratory to routinely check gravel and/or root zone samples
brought to the construction site. It is imperative that these
materials conform to the recommendations approved by the laboratory
in all respects. Some tests can be performed on site with the proper
equipment, including sand particle size distribution.
Care should be taken to avoid over shredding the peat, since it
may influence performance of the mix in the field. Peat should be
moist during the mixing stage to ensure uniform mixing and to
minimize peat and sand separation. Fertilizer should be blended into
the root zone mix. Lime, phosphorus, and potassium should be added
based on a soil test recommendation. In lieu of a soil test, mix
about 1/2 pound of 0-20-10 or an equivalent fertilizer per cubic
yard of mix.
Step 5. Top Mix Covering, Placement,
Smoothing, and Firming The thoroughly mixed root zone
material shall be placed on the green site and firmed to a uniform
depth of 12 inches (300 mm), with a tolerance of ± 1/2 inch. Be sure
that the mix is moist when spread to discourage migration into the
gravel and to assist in firming.
Step 6. Seed Bed Preparation
Sterilization: Sterilization of the root zone mix by
fumigation should be decided on a case by case basis, depending on
regional factors. Fumigation always should be performed:
- In areas prone to severe nematode problems.
- In areas with severe weedy grass or nutsedge problems.
- When root zone mixes contain unsterilized soil.
Check with your regional office of the USGA Green Section for
more information and advice specific to your area.
Step 7 - Fertilization
Contact your regional USGA Green Section office for establishment
fertilizer recommendations and grow-in procedures.
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