The challenge on this project was to install the sports field slit drainage system without any damage to the insitu geo-fabric layer, installed at a depth of 300mm below the turf grass surface.
After carefully surveying the sports field surface levels and checking the profile depth. The field grades were found to be consistent and the surface sagging minimal. Therefore, we designed a system of slit drainage, without pipe, using washed pea gravel and drainage sand. The system is reasonably intense to counter the slower flow rates and also to achieve a field with a minimum of surface ponding.
A brief scope of the works is as follows;
We excavated the mainlines on the northern and the southern perimeters of the field, with outlets to discharge into the existing storm-water system. The 150mm diameter agricultural pipe was laid on a pvc membrane at the base of the trenches and connected to the existing storm-water pits. The trenches were back-filled with washed river gravel and selected coarse drainage sand to achieve the perched water table required. Total length was 320 metres.
The un-piped slit trenches are 70mm wide and excavated east/west across the field over the existing irrigation and geo-fabric 3 metres apart. The 70mm slit trenches are also excavated north/south, at 3 metres apart, laser graded to ensure drainage to the main pipe trenches. Generally, the trenches are 250mm deep just above the fabric and back filled with river gravel and topped with selected drainage sand. The gravel in these slits meeting the gravel in the carrier slits and main pipe trenches. Total length was 10,900 metres.
The project was completed in two weeks and the sports field slit drainage system has been performing well.
Our thanks go to Randwick City Council for the opportunity to complete these works for them.