Environmental Engineering Reference
In-Depth Information
A USGA green consists of a 30-cm-thick layer of sand mixed with 5%
silt and clay and 5% organic material (peat moss), placed over a 10-cm-
thick gravel layer (Fig. 9.2). This series of layers produces a perched water
table, in which water drains only to the intermediate layer rather passing
through it and draining away. Capillary forces hold the water in the fine
pore spaces above the gravel against the force of gravity, where it can be
used by turf-grass for a relatively long period of time. When heavy
rainfall occurs, the excess water easily drains to the underlying gravel,
where capillary forces are not sufficient to prevent it from draining away.
When the rain stops, the weight of water in the sand layer again comes
into balance with capillary forces, and drainage stops. This system of
drainage is thoroughly described in Chapter 3. Note that only if the exact
specifications for the USGA green are followed will its drainage function
correctly.
USGA Green
30 cm
sand/peat
root zone
10 cm
gravel layer
Compacted
subgrade
10
−
15 cm
drain tile
Fig. 9.2. Profile of a United States Golf Association golf green.
