Yard slope and drainage
Slope
The degree of slope in a holding yard can affect cow flow and comfort. It also has an effect on cleaning and drainage.
Upward slopes
3% to 4% slopes (1:30 to 1:25) angled towards the dairy, encourage cows to face the dairy, and are also better for
cleaning.
Greater than 4% slopes (1:25) lead to increased wear at the yard-platform intersection. As the concrete wears smooth
the incidence of slips and falls will increase. Steep upward slopes also cause weight to be transferred from the cows’
front to rear legs which is undesirable as it can result in injury.
Where steep upward slopes are unavoidable, steps are preferable to a slope. Cows prefer to walk up well constructed
steps than on a steep slope because their foot placement is on safe level surfaces.
Downward slopes
Cows are often reluctant to go down slopes exceeding 5% (1:20).
Figure 1. Single slope yard with grooving all running down slope.
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Single slope yard
A single, consistent slope up to the dairy will encourage cow flow into the dairy (Figure 1).
A drain positioned one third of the way down the yard from the dairy allows most of the manure to fall close to the drain,
minimising effluent build up and wash down time (see Figure 2). This provides the same cleaning benefits as a twin slope or
butterfly yard (for a description of this see next section). However, cows may be reluctant to cross the grate, thus impeding
movement towards the dairy.
Figure 2. A single slope yard with drain to aid yard cleaning when a hose is used.
Two slope (butterfly) yard
Some yards have twin falls (slopes) designed to aid drainage and hose cleaning.
A butterfly yard has two converging slopes. Most of the manure falls close to the drain and is quick to wash away (see Figure 3).
Flood washing is not an option for a butterfly yard.
Drains in twin slope yards need to be positioned away from the dairy (as in single slope yards), otherwise they may impede cow
flow into the dairy.
Figure 3. Butterfly yard with twin slopes feeding into a single drain.
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Drainage
Pipes or gutter drains are used to drain holding yards. Regardless of which is used, the system must be sized for the volume
and flow rates of the water used in cleaning the yard, particularly in the case of flood washing.
When flood washing is used, sumps and drains at the bottom of the yard should be sized to cater for the highest flow rates
used.
Pipes
Construction material
It is best to use sewer quality PVC. PVC pipes have a smooth interior, are resistant to acid attack and are easy to
install.
Slope
It is important to get the pipe slope correct. The minimum recommended slope is 1.5% (1:66) with a maximum of 3.3%
(1:33).
At low slopes, the flow velocity is insufficient to flush material away. A slope of less than 1.5% may cause manure and
other solid particles to lodge in the pipe. At high slopes, the liquid ‘jumps’ over solid material.
Size
Individual drainage pipes should have a diameter of at least 150 mm.
The recommended diameter for main drainage pipes is 200 - 300 mm.
Drains
The size of holding yard drains will depend on the flow rates required and viscosity (thickness) of the liquid to be
drained away.
Open drains should have a V shaped bottom for better solids flow.
Kerbing
The perimeters of all concrete yards and races require a kerb which is a minimum of 150mm above the surface level of the yard.
This prevents soil and effluent washing off yards and races.
Figure 4. Kerbing prevents soil and effluent washing off yards and races.
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