Last week, I travelled to Castlerea, Co Roscommon, to see a drainage job being carried out on very challenging ground. The field has, for some years, carried a very dense and high cover of rushes, providing just rough grazing. But adjacent fields, which had been drained, limed and reseeded, give good grazing, so the landowner decided that it was time to do likewise here.
The 12-acre field is rectangular, level and slopes down to a sizeable river flowing along the bottom (see Figure 1). No attempt had been made to drain this field in modern times.
There were a number of ditches – including one running down the long side of the field to the river – but these were shallow and did little more than allow the worst surface water to escape.
The farmer called in Dessie Taaffe of Eagle Plant Hire, based in Co Louth, for advice. Dessie dug test holes and took levels. The test holes showed shallow topsoil over very slow-draining subsoil, a sandy, more permeable layer at 2ft to 3ft and below this, more slow-draining layers.
The laser showed the river to be, in summer anyway, 3ft to 4ft below most of the field. Dessie recommended:
Deepening the open drain running down the long side of the field. This would allow drainage pipes to be placed across the field, at the depth of the sandy layer, to collect water and carry it to the deepened ditch.The pipes to be installed approximately every 12m.Pipes to pass through a number of localised wet/low spots.The pipes to run in a herringbone angle from the open ditch to take best advantage of slopes.He also advised that it would not be possible to do this work with the dense cover of rushes in place.
He recommended this be cleaned off before drainage work began. The farmer went with this plan.
Picture one
The rushes were sprayed off and, after some weeks, the dead vegetation chopped by tractor and mulcher. This picture gives us a good idea of what Dessie Taaffe was dealing with when he moved on site. Despite the dry summer the ground was waterlogged and very soft.
Picture two
The river at the bottom of the field is large. We can see how much lower it is, in August, than the field.
Finding an outlet for excess water lying on this field was, therefore, not an issue. The only question was how to get it there. The ground adjacent to the river is dry.
Note that in a wet winter, this river can rise and flood on to surrounding land by a distance of up to 100m.
The landowners along this river would benefit if it was cleaned out.
Picture three
Dessie Taaffe’s first action was to clean and deepen this ditch, which runs along the side of the field.
He lowered the bottom by 2ft to 3ft. Again, once the ditch was opened, the closest 10m or so of ground dried up, but there was no big flow of water from the main body of the field.
Further help would be needed in the form of plastic drain pipes, running from the middle of the field into this ditch.
Picture four
Next, Dessie cleaned and lowered this second, open ditch, which ran across the field halfway up. It was 1ft deep – it’s now 4ft.
Dessie also made this new bridge to give access between the two parts of the field, using Corripipe.
The centre ditch runs as far as the edge of the field and stops abruptly.
Picture five
We can see the heavy cover of rushes in the field over the fence, where the ground is similar. It gives us a good idea of what this field was like before it was sprayed off and the vegetation chopped.
Picture six
This is the sandy material, which runs across the field in a layer at 2ft to 3ft depth.
Underneath impermeable, dense subsoil, Dessie placed the drain pipes in this layer to catch excess water.
Picture seven
This 80mm pipe is being laid in a 160m drain. The drain is 600mm deep at the open ditch outlet and up to 1m deep at the other end.
The pipes run out at an angle from the ditch, taking advantage of the rising ground. If the pipes were to run out straight, they would have to be placed deeper to get under all low spots.
Picture eight
This is the wettest part of the field. Dessie had to move quickly with the stoning cart to cover the drainage pipe. The cart has wide tyres but they still sink in the wet ground. The field will be ploughed and levelled ahead of liming and reseeding.
Picture nine
The heaped spoils were all dug out from the top 3ft. The topsoil layer is shallow, the subsoil dense and slow-draining.
Draining this 12-acre field will cost approximately €13,000, or €1,080 per acre.
However, if the open ditches are kept clean, the stoned, plastic drains can be expected to keep working for many years.
Last week, I travelled to Castlerea, Co Roscommon, to see a drainage job being carried out on very challenging ground. The field has, for some years, carried a very dense and high cover of rushes, providing just rough grazing. But adjacent fields, which had been drained, limed and reseeded, give good grazing, so the landowner decided that it was time to do likewise here.
The 12-acre field is rectangular, level and slopes down to a sizeable river flowing along the bottom (see Figure 1). No attempt had been made to drain this field in modern times.
There were a number of ditches – including one running down the long side of the field to the river – but these were shallow and did little more than allow the worst surface water to escape.
The farmer called in Dessie Taaffe of Eagle Plant Hire, based in Co Louth, for advice. Dessie dug test holes and took levels. The test holes showed shallow topsoil over very slow-draining subsoil, a sandy, more permeable layer at 2ft to 3ft and below this, more slow-draining layers.
The laser showed the river to be, in summer anyway, 3ft to 4ft below most of the field. Dessie recommended:
Deepening the open drain running down the long side of the field. This would allow drainage pipes to be placed across the field, at the depth of the sandy layer, to collect water and carry it to the deepened ditch.The pipes to be installed approximately every 12m.Pipes to pass through a number of localised wet/low spots.The pipes to run in a herringbone angle from the open ditch to take best advantage of slopes.He also advised that it would not be possible to do this work with the dense cover of rushes in place.
He recommended this be cleaned off before drainage work began. The farmer went with this plan.
Picture one
The rushes were sprayed off and, after some weeks, the dead vegetation chopped by tractor and mulcher. This picture gives us a good idea of what Dessie Taaffe was dealing with when he moved on site. Despite the dry summer the ground was waterlogged and very soft.
Picture two
The river at the bottom of the field is large. We can see how much lower it is, in August, than the field.
Finding an outlet for excess water lying on this field was, therefore, not an issue. The only question was how to get it there. The ground adjacent to the river is dry.
Note that in a wet winter, this river can rise and flood on to surrounding land by a distance of up to 100m.
The landowners along this river would benefit if it was cleaned out.
Picture three
Dessie Taaffe’s first action was to clean and deepen this ditch, which runs along the side of the field.
He lowered the bottom by 2ft to 3ft. Again, once the ditch was opened, the closest 10m or so of ground dried up, but there was no big flow of water from the main body of the field.
Further help would be needed in the form of plastic drain pipes, running from the middle of the field into this ditch.
Picture four
Next, Dessie cleaned and lowered this second, open ditch, which ran across the field halfway up. It was 1ft deep – it’s now 4ft.
Dessie also made this new bridge to give access between the two parts of the field, using Corripipe.
The centre ditch runs as far as the edge of the field and stops abruptly.
Picture five
We can see the heavy cover of rushes in the field over the fence, where the ground is similar. It gives us a good idea of what this field was like before it was sprayed off and the vegetation chopped.
Picture six
This is the sandy material, which runs across the field in a layer at 2ft to 3ft depth.
Underneath impermeable, dense subsoil, Dessie placed the drain pipes in this layer to catch excess water.
Picture seven
This 80mm pipe is being laid in a 160m drain. The drain is 600mm deep at the open ditch outlet and up to 1m deep at the other end.
The pipes run out at an angle from the ditch, taking advantage of the rising ground. If the pipes were to run out straight, they would have to be placed deeper to get under all low spots.
Picture eight
This is the wettest part of the field. Dessie had to move quickly with the stoning cart to cover the drainage pipe. The cart has wide tyres but they still sink in the wet ground. The field will be ploughed and levelled ahead of liming and reseeding.
Picture nine
The heaped spoils were all dug out from the top 3ft. The topsoil layer is shallow, the subsoil dense and slow-draining.
Draining this 12-acre field will cost approximately €13,000, or €1,080 per acre.
However, if the open ditches are kept clean, the stoned, plastic drains can be expected to keep working for many years.
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