Draining a wet hollow in Co Louth

This week, I feature a drainage job carried out on sloping ground in Co Louth. This job didn’t involve draining a whole field – just the bottom of a saucer-shaped bowl.

In grassland, a single wet spot isn’t a big deal. But this is tillage land and the wet spot was in the centre of a field and therefore very inconvenient.

What made this job interesting was that the small wet spot was surrounded by a circle of higher ground, so there was no simple way to bring water to an outlet.

The drainage pipe would have to tunnel its way through to the lower ground on the far side.

The farm is at Knockbridge. The job was carried out by Dessie Taaffe of Eagle Plant Hire.

Picture one

The wet spot is on the left – the combine certainly didn’t go through it, despite the dry summer. This land is actually quite free-draining.

The problem is that rain runs down steep slopes of this bowl and pools in the bottom.

Because of this, drainage there has become impeded over time.

The surrounding sides of the bowl vary from about 40ft above the hollow at the highest point to 5ft at the lowest and the pipe will route through the lower point.

Dessie didn’t run the pipe through the middle of the wet spot as it could be at risk there of being damaged by wheels at some future point. The drier ground to the side is more stable and easier to work through. “I want to keep the main water carrier safe,” he said. “I’ll run a spur off it into the middle of the wet spot.”

Picture two

A drain in tillage land needs to be placed deep, well under machinery wheels, and this drain had to go deeper than normal.

A deep channel has to be wide, for safe working. All of this would result in a lot of subsoil being excavated.

Dessie wanted to avoid the subsoil mixing with the more fertile topsoil and remaining on the field surface. Therefore, his first step was to strip the topsoil off a wide passage, along the route of the pipe, and place it to one side, in a long row. He then dug out the channel for the pipe, placing this subsoil in a separate row.

Picture three

The subsoil will be placed on top of the pipe to fill in the excavation – and the clean topsoil then spread back on top. The topsoil is fine, workable material.

Meanwhile, in this picture, we can see the higher ground in the background that makes the side of the bowl.

Picture four

At the wet spot, the pipe is placed 4ft deep. Along its route, the ground rises and, here, the pipe is now about 7ft below the field surface (remember, the topsoil layer has been stripped off the bank).

At the deepest point, it is over 8ft. The pipe is 200m long. Just 75m of it – near the wet spot – is perforated. The other 125m is a solid twin-wall pipe. The diameter is 150mm (6in). Here, we can see the subsoil layers.

Picture five

Dessie dug out the channel with his trapezoidal bucket. It is 1.5m (5ft) wide on top and 450mm (18in) on the bottom. Placing the pipe requires someone working down in the excavation, as does later stoning, seen here.

A narrow trench would be at risk of collapse but the wider trench dug by the trapezoidal bucket is safer to work in.

Pictures six and seven

The pipe emerges in the corner of this field into an open ditch which flows on to a large wetland area. The pipe has been in place for only two hours but, already, there is a steady flow of water out of it (picture seven).  

Traditional field gates event in Kilkenny

An event featuring traditional field gates will take place in Castlecomer Discovery Park, Co Kilkenny, on Sunday 12 October from 2pm to 6pm.

A new booklet, The Vernacular Forged Wrought Iron Gate by Shem Caulfield, will be launched on the day.

According to Teagasc countryside management specialist Catherine Keena, this booklet highlights the value of traditional field gates and gives farmers useful information on their care and maintenance.

There will be blacksmith demonstrations, a display of traditional field gates, an exhibition on the history and development of wrought iron gates and screening of films on field gate heritage at the event.