Slit Drain Systems

Many sports are played in the spring, fall and winter months when there are rainy periods. On native soil fields, this often leads to muddy playing conditions because many native soils do not drain very well. Since the 1930's there have been options for improving the drainage capability of native soil fields. These options have included (in order of relative cost):

* Complete field construction of a sand-based field, with the percentage sand 85% or higher by wt.

* Sand amended fields, whereby sand is blended with the native soil, on or off-site, to bring the sand percentage of a field to 75% or more by wt.

* Sand slit drains installed in the surface of the field (see picture left) and

* Annual sand topdressing programs to gradually improve soil texture over time.


The first recorded attempt to install a slit-drained field was at Twickenham (England's Rugby Stadium) in 1969. At that time, slits were produced with mole ploughs and backfilling with sand to produce a level surface was difficult. Nowadays, there are specific pieces of equipment designed to produce sand-slit drains and leave a true playing surface. Slit-drained fields are designed whereby surface water bypasses the native soil, so that the local soil has less of an influence on drainage rates. There are a wide range of slitting techniques. For example, a common specification in England is sand slits 2-inches wide, 10-inches deep, on 3 ft. spacings**. Most importantly, the slits must transmit surface water through the native soil surface to a more permeable material underneath - such as a gravel layer or permeable fill over pipe drains. The slits run perpendicular to the pipe drains.

Two problems can occur with slit drained fields: (1) when the permeable material does not come into contact with the sand slit (i.e. there is a soil layer between the sand slit and the underlying permeable material), or (2) when the slit is not kept directly at the field surface and the slit is sealed off by adjacent native soil. This can occur rapidly, even during one game if field conditions are very wet. To prevent the latter, a heavy annual sand topdressing program has to be initiated to make sure that the slits are not "capped off" over time.

Research by the STRI has indicated that these types of field can accommodate 6 hours adult play per week (95-125 events per season). In addition, they have suggested that, if managed correctly, a slit-drained field should last about 7 years before needing to be slit again.

** Ref: Dr. W.A. Adams (2004) Construction Methods Theory & Practice, STRI Turfgrass Bulletin, Issue 226, p.26-30.


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