HOW THE BUNKER DRY SYSTEM WORKS

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The device simply acts as a covered drain or more correctly a hydrostatic weir. The term used describes the function as follows:

Rainfall and or overland water flow from the green, fairway or other surrounds enter the bunker and depending on the rainfall intensity and position of the bunker, begin to saturate the sand.
The bunker only begins to fill with water when the sand becomes saturated. Even if the bunker has a good performing conventional drainage system, the balance point between the bunker staying dry and filling with water depends on flowrate.
When the flowrate into the bunker exceeds the flowrate out of a bunker, water will accumulate and present golfers with a difficult shot or an unplayable lie, even a lost ball! Heavy rains can even render the bunker temporarily out of play. Extended periods of rainfall and water accumulation can start to damage the soil edges, which requires maintenance and the removal of silt washed into the base of the bunker, not to mention putting the bunker out of play for a period of time. Every Greenkeeper knows the perils of working on bunkers during play. Elimination of unnecessary work and keeping staff safe is of paramount importance. If a bunker does not have any drainage system, the bunker will fill quicker and remain full for much longer periods
The problem with conventional drainage systems such as agg pipes and other drains which rely on very small holes or slots to filter the water and limit the sand entering the pipe, is their ability to accept high flowrates. High flowrates in, must be balanced with high flowrates out, a very simple concept.
The Bunker Dry device is different. Unlike conventional drains which features small holes or slots and coupled with geotextile wrapping to filter the water and limit the sand ingress, the Bunker Dry device relies simply on gravity to,
The Bunker Dry system does this by protecting the inlet to the drain with an inverted cap which allows water in at a much higher flowrate and keeps sand out which allows free flow inside the drain. The elimination of sand is a major factor for performance and maintenance of the drainage system.

Water flows freely through sand. The rate of flow depends on the on the type of sand and the depth. The Bunker Dry device is designed to be installed between 125mm and 200mm below the surface of the sand (bunker). It can be deeper if required. This depth allows the device to perform as follows:

Be unobtrusive and invisible
Situated below the depth of a club stroke
Also situated below the depth of maintenance equipment in the bunker eg; grooming machines
Accessible for maintenance
Best location hydraulically, to drain water from the bunker
All bunkers are different, however they all share a number of things in common. Nearly all bunkers have low points either by design or by accident. This is apparent when rain fills a bunker and water is seen pooling over the sand. Most modern bunkers employ a drainage system which draws water from the bunker and most of the water from the low points. The key to Bunker Dry’s success, is to position the device at the low points of a bunker. When installing a Bunker Dry system in an existing bunker, the bunker low point(s) are usually adequate to be effective.

Bunker Types
Category	Size	Depth	Shape	Comments
1	Small	Shallow	Circular	Depth up to 0.6m
2	Small	Deep	Circular	Depth greater than 0.6m
3	Small	Shallow	Elliptical/Irregular	Depth up to 0.6m
4	Small	Deep	Elliptical/Irregular	Depth greater than 0.6m
5	Medium	Shallow	Circular	Depth up to 0.8m
6	Medium	Deep	Circular	Depth greater than 0.8m
7	Medium	Shallow	Elliptical/Irregular	Depth up to 0.8m
8	Medium	Deep	Elliptical/Irregular	Depth greater than 0.8m
9	Large	Shallow	Circular	Depth up to 1.0m
10	Large	Deep	Circular	Depth greater than 1.0m
11	Large	Shallow	Elliptical/Irregular	Depth up to 1.0m
12	Large	Deep	Elliptical/Irregular	Depth greater than 1.0m

Depending on the size of the bunker, it may also be of value to create some additional low points to encourage higher flowrates which will keep the sand area drier.
Bunkers which are larger than the examples shown on the sizing chart below, requires sizing on a case by case basis. Bunker Dry can provide this service at no additional cost.

Bunker Dry Sizing Chart
Area of bunker [m²]	Category	Number of Bunker Dry units	Comments
6-59m²	1, 2, 3 & 4	1	Locate close to centre at lowest point.
60-100m²	2 & 4	1	Locate close to centre at lowest point.
60-100m²	1 & 3	2	Locate close to centre at lowest point @ approximately 2.0 m apart.
101-150m²	6 & 8	2	Locate close to centre at lowest point @ approximately 2.0 m apart
101-150m²	5 & 7	3	Locate close to centre at lowest point @ approximately 2.0 m apart
151-200m²	10 & 12	3	Locate close to centre at lowest point @ approximately 3.0 m apart
151-200m²	9 & 11	4	Locate close to centre at lowest point @ approximately 3.0 m apart

The secret to draining any bunker is to convey rain flows away to a discharge point which is outside the area of the bunker. Any drainage system will rely on gravity to encourage flows to a terminal. The terminal or discharge point can be a dedicated stormwater pipe system which is optimal, or a surcharge pit, or a ground water dispersion system.
At some Golf Courses, the topography can be flat which creates problems grading the surface for overland flow paths as well as installing effective stormwater pipes. Draining bunkers is exacerbated when out of reach from a stormwater system, dam or creek. In these cases, a ground water dispersion/absorption system is one option, another is an evapo-transpiration bed. These systems as the name suggests uses the ground surface and or the subsurface to provide a medium for water transfer and dispersion. The correct option is dependent on the ground strata conditions. Permeable ground conditions such as sand or loam tend to favour a dispersion/absorption system while less permeable ground like homogenous clays or rock will require an evapo-transpiration bed 1.2.
Another option is to construct a vault storage system which essentially collects water from the bunker and retains the volume over a period of time. The volume must be equal to the critical quantity of water which is expected to fill a bunker during a significant rain event.

We have vast experience in drainage systems and can consult with you to recommend the best solution.

Installation Instructions

First of all, it is important to conduct a survey of the bunker to determine where the lowest point/s are. If the bunker is greater than 60m2 and has more than one (1) low point, it is recommended that two (2) Bunker Dry units are installed.

The Bunker Dry unit must be located at the bottom of the bunker and more importantly at the lowest point in the sub-strata (pic). This allows water to infiltrate the sand layer and track along the base of the sub-strata to collect at the Bunker Dry unit. As the volume of water increases, the Bunker Dry unit drains the base of the bunker at a greater rate than conventional sub-soil drainage system.

Having determined the low point/s, it is a simple task of excavating the bunker sand and exposing the base of the bunker. The ideal depth of the Bunker Dry unit from the very top of the dome to the surface of the bunker is between 12mm & 200mm. This can be more, up to 300mm but no less than 125mm. Less than 125mm will reduce the amount of sand required to protect the unit from damage either by grooming equipment or by Golfers.

If the bunker has a drainage system installed, the Bunker Dry can be piped direct to the system providing it is in good working order, eg: flows freely and drains away to a point below the base of the bunker. Ideally the pipe should be a minimum Ø90mm solid wall or corrugated with infiltration slots. If it is an existing sub-soil line, it is important to wrap the pipe in a geotextile or stocking to limit the fines which wash into the system.

If there is no existing sub-soil drainage system in the bunker, the Bunker Dry will require a new pipeline to drain away the water collected. As per an existing drainage system, the new system will need to be installed at the base of the bunker and grade away to a discharge area below the base. This pipe can be solid of corrugated with infiltration slots and we recommend a minimum size of Ø100mm and laid at a grade not less than 1:100 or 1%.

Refer installation instruction including diagrams.

HOW THE BUNKER DRY SYSTEM WORKS

Bunker Types

Bunker Dry Sizing Chart