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Sub-soil Drainage

Total Turf Care specialise in sub-soil sports turf drainage. This aspect of sports turf maintenance and construction is a large part of our business.

Since 1999, we believe we have installed conservatively well over 350,000m of sub-soil drainage. The majority of this being on sports grounds. We have the capacity to trench, collect the material, lay the ag-pipe and back-fill the trench in one continuous motion, all in a single pass.

We typically start with a site visit to look into the conditions that are present. It is always good to look at the ground in the worst conditions, typically in winter following a sports game. Give Nic a call and he will come out to inspect the site at this time. From this inspection, a drainage plan can be drawn up and appropriate budget pricing aligned to this.

Sub-soil turf drainage is typically made up of two parts. Firstly, the primary drainage component, this being the ag-pipe lateral drains, and secondly the sand binding or slitting component.

The 2-way approach

  1. Primary piped sub-soil drains. ​​These are 65mm ag-pipe, 5-7mm blue metal with
    150mm +/- of free draining sand toppped, spaced at 2.5m centres +/-.

  2. Sand banding at 90° to the 65mm piped ag-drains. These at 1m centres x 50mm wide x 200mm deep. These intersect with the gravel layer of the piped ag-drains and carry the drainage water directly to the piped sub-soil drain.

The essence of good sub-soil drainage design, centres around having the 65mm piped drains at or as close to 90° to the major fall grade on the playing surface of the oval. This will enable the excess water (rainfall) to travel the least possible distance prior to interception with a sand topped/gravel backfilled sub-soil drainage line. Existing irrigation infrastructure does not always allow this to happen. This is where the sand bands make a major contribution. 

The sand bands move the surface free water much slower than the primary piped ag-drains. This is because there is no blue metal for the water to transverse quickly through. Therefore, these secondary sand bands need to be at the greatest grade fall possible on the ground to maximise the speed at which the water can travel through them, before reaching the piped ag-drain to release water into.

Total Turf Care use either GPS or laser control for accuracy control.

Sub-soil Drainage Maintenance

The area of 3 years +/- post installation of sub-soil drainage maintenance is one turf maintenance area that is largely overlooked, and we don't understand why. It is a very critical piece of turf maintenance works.

When the sub-soil drainage works are initially installed there is a free draining medium of sand installed above the 65mm blue metal encased drains, usually about 130-160mm in depth. What happens over time (three years plus) is that these sand drain lines , approximately 160mm wide will become mixed (top 10mm +/-) with the surrounding loam material on the oval. When this happens, this has the effect of dramatically slowing the infiltration rate of the water down from the oval playing surface through this 150mm +/- thick layer of sand into the drain pipe themselves.

Less than 5% of water that is removed through sub-soil drainage pipes comes into the drainage pipe through the 'soil wall' in the drainage trench. Rather the excess eater enters the drainage pipe work by traversing across the playing surface until reaching the sand top of a sub-soil ag-drain. The water infiltrates down through the initial 150mm +/-  sand medium and into the lower gravel layer and into the drainage pipe network and away. This is at an increased infiltration rate to the surrounding clay loam ground area.

To overcome this problem, Total Turf Care have developed a hollow coring methodology that sees 25mm cores removed from this area and 500mm either side of the drain centre line. These cores are then brushed sideways and collected. The remaining hole is then filled with the original used free draining sand again. This work then ensures that the drain lines maintain their original integrity.

Total Turf Care also carries out an intensive de-thatching/scarifying process along these drainage lines. This material is again collected and removed from site.

These activites are undertaken by using sub-2cm auto-steer GPS guided tractors. This is a tremendously important point. When Total Turf Care install the sub-soil drainage network on the sports ground, GPS data is taken of each lineal metre of drain. This information is then re-used in the maintenance works to ensure complete sub-2cm accuracy on the maintenance works. No guessing where the drains are, cm perfect accuracy.

These sub-soil drain turf maintenance activities ensure that the sub-soil drainage systems are kept to work at peak efficiency.

Total Turf Care is happy to provide pricing to carry out these very specialised sub-soil turf drainage works.

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