Cuddy's marshy muck-shift on a West Wales golf club

In West Wales, local contractor Cuddy has pitched in to help iron out a few water hazards at the Machynys Peninsula Golf Club near Llanelli. Paul Thompson reports.

It has been a long, wet, miserable summer for the Cuddy team working on the flood alleviation scheme at the Machynys Peninsula Golf Club.

When it rains in this part of Wales, it tends to stay around for weeks and that is exactly what happened here during the summer. It started raining at the end of July and stopped at the beginning of September, making the job of muck-shifting in an area of marshland prone to flooding very difficult indeed.

"We had torrential rain for about a month and there wasn't much we could do," says Gavin Lockyer, Cuddy Group contract manager. "You just have to sit it out and hope for the best."

Eventually, the completed scheme will prove the wisdom of patience as it will protect the course from the worst effects of flooding from the Afan Dafen stream that flows through it. At first glance, it looks little more than a babbling brook threatening only the most wayward of tee shots, but looks can be deceptive and its large catchment area means the river channel struggles to contain the volume of water during peak flows.

Incoming tides

If those peak flows coincide with an incoming tide and high water on the other side of the earth bund that separates the Jack Nicklaus designed course from the tidal Loughor Estuary, the water backs up on the inland side of the bund from the existing outfall, causing flooding.

The proposal now is to increase the capacity of this outfall and build a protective berm on the course side of the Afan Dafen. A large floodwater storage area is also being landscaped, which will feature a flow regulating penstock system to control water levels and flow rates. A total of 35,000m³ of earth will be moved around the site, all of it re-used.

The new bunds are keyed into the existing topsoil by around 150mm, then constructed using earth won from borrow pits at a series of locations around the golf course. Built to a minimum height of 4.35m above chart datum, the new bunds are generally around 4m wide, although there are a few pinch points around the course where the width squeezes to 2.5m. The bunds are built up in 200mm layers and compacted using the heavy, tracked machines that are being used on the site, itself a weather enforced deviation from the initial intention.

"We did have a roller but it wasn't particularly practical," says Lockyer. "We had to change our work method and go to tracked dumpers instead of wheeled."

In the end, the project team have used three 20t Case 360 tracked excavators and three 22t tracked dumpers to run material from the 26,000m³ bulk earthworks that will provide the water storage cell.

But it wasn't just the appalling summer weather that forced this change of tack. No sooner had the team started digging than it ran into problems with running sand - a geological condition that occurs when water flows through loosely packed sand, lubricating the grains and causing them to flow. It can occur in excavations below the water table and at Machynys there are several spots where the sand has a blancmange-like wobble.

"The earth is a bit of a mixture here. A lot of it was imported when the course was initially built. There are patches of clay and sand, some of which are better than others," Lockyer explains. "It would have been impossible to use heavy wheeled equipment in that sort of situation. Using the skidsteer tracked dumpers has been far more practical."

The areas of running sand will be dug out to the required depth with the excavated material stockpiled for use in the next phase of the Pentre Nicklaus Village, a housing development aimed at golf addicts on land overlooking the course.

Dotted around the course are four headwall pairings that help regulate flow into and out of the Afan Dafen from its smaller tributaries around the site. Featuring small 150mm-diameter pipes and valves to stop flood water flowing back up them, these headwalls are dwarfed by the new larger wall and its twin 1,500mm-diameter pipes that are being built to allow the river to flow out into the estuary.

Keeping golfers happy

All of these improvements are aimed at keeping the club's golfers happy and ensuring they can't blame anything but their swing if they post a below-par performance, but for non-golfing Gavin Lockyer there is no temptation to sneak a quick round after work. He just wants to make up for the lost summer.

At the point where the Afan Dafen runs below the existing earth flood protection wall, the project team are carrying out remodelling work to increase the rate of flow through the bund.

The banks of the stream are being straightened and widened and two new 1500mm diameter plastic pipes are being installed as culverts to direct flow out into the Loughor Estuary. Precast concrete headwall structures, manufactured by Norfolk-based drainage product specialist Althon, help shepherd the flow.

Following extensive consultation and studies carried out on behalf of the Environment Agency, the site has been identified as being an important breeding site for water voles. Any construction work has to be closely monitored and the new channels have to be hand-dug around the burrows highlighted by the site investigations.

"There are plenty of issues around outfalls into the sea anyway," says Lockyer. "Here, we've replaced in-situ concrete headwalls with precast to reduce disturbance and to stop the likelihood of concrete leaching into the water."

The large tidal range at this point on the Welsh coast has had its impact on the project too. It's not quite as large as further east along the Bristol Channel, but it is still a mighty 10m, and saw the installation of a steel sheet pilled cofferdam vibrated 3m-4m into the soft clay and sand of the estuary. Access is also limited by the tide.

"We don't work at high tide for safety reasons," says Lockyer. "We try to get at it from mid-tide. We are in effect undermining the existing flood wall so we have to treat the cofferdam as a defence wall itself."