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Bunker Liner Basics

by David McPherson

Installation of SandMat bunker liner. Ted Fist, a technical and installation expert for Milliken & Company, recommends using galvanized staples, rather than steel, during installation. “It’s an investment in the longevity of the product,” he says. Photo courtesy of SandMat by Milliken.

With the lingering recession and slashed budgets, superintendents are looking to cut their capital spending while still offering the highest quality product for golfers. Bunker liners are one area where greenkeepers can’t afford to skimp; they need to take a long-term view. Bunker maintenance is costly, but liners will help reduce the amount of labor required to maintain these hazards.

“Unfortunately, the use of bunker liners has been impacted by the economy,” says Clive Mills, market development director for Fiber Bond Corp. “Bunker liners are very often, especially on a new course, in the group of the very last materials that go into the course in the construction sequence. If it gets late in the year, and you have a builder who wants to get this done before the snow flies, or if you have a course that is over budget, or challenged with budgets and needs to make last-minute cuts, the bunker liners often are the victims ... they lose track of long-term benefits for short-term gains.”

Rain, combined with the topography of today’s bunkers, where architects have gotten progressively more creative with shapes, means bunker drainage is a constant challenge. Heavy rains can cause washouts that require a lot of labor to get them back to playing shape.

“They reduce the amount of sand that will wash out in a rain event, especially on a steep face,” explains Mills. “If there is no drainage blanket under the sand, or no stabilizer below the sand, a typical .5-inch rain event is enough to cause the sand to wash out and slump up that face.

“With liners in there, these products have the ability to assist in the drainage of the sand,” he says. “The sand will stay more stable to the face and reduce the labor costs involved to repair the sand surface. The labor savings can be pretty dramatic.”

Besides the economic benefits, bunker liners also improve the consistency and playability of the sand.

“The sand is more consistent, more uniform and drier throughout the whole bunker,” explains Mills. “From bunker to bunker on the golf course, it is more consistent. The course tends to play better as the sand tends not to get contaminated like it does if there is no liner there.”

Liner options

When choosing a liner, Mills says that you need to look at soil conditions, the environment and the slope of the bunkers. The first question Mills asks a superintendent is whether or not the bunker is draining well. If not, he says to fix the drainage system first before investing in bunker liners.

“There is no sense putting in brand-new bunker liners and more expensive sand if your drainage system is compromised to begin with,” he explains. “They should go together. A lot of people don’t grasp that. You are putting in a liner that functions by drainage, taking the water out of the sand very rapidly.

“You can exacerbate a bad drainage system because the liner is going to get water to that drainage system even faster,” he adds. “So, if you had a bad drainage system before, you are going to have a real bad system after you put a liner in. If putting new liners in your sand, you should definitely spend the extra money to evaluate that your drainage system is really good.”

Mills represents Fiber Bond Corp. (www.fiberbond.net). The company is introducing a new bunker liner in 2010 called TrapTex. According to Mills, it’s a high-end textile product with built-in UV protection, which is its biggest advantage. So, if a bunker liner is installed and there is a delay in the delivery of sand, the liner won’t deteriorate.

“These textile products are all made from polyester fiber,” he explains. “Polyester has some resistance to sunlight, but not a whole lot. The materials will eventually degrade, lose color, lose strength, and start to get crunchy and crispy like fiberglass left in the sun. Without having extra UV stabilizers in the product, they become quite suspect to sunlight degradation.”

Also built into the product is an anti-biological growth additive, which they call a “bio-blocker.”

“This will stop the potential buildup of sludge that accumulates in the liner over time with wet conditions,” he explains. “This additive helps the product be free and open to stop that buildup, so the product will keep draining and performing longer.”

Mills says TrapTex is suited more to a tropical climate where you have extreme rain. Fiber Bond will launch a second liner in 2010 to serve the day-to-day North American environment where there aren’t extreme wet conditions.

The SandMat solution

Before choosing what type of liner to install, Ted Fist, a technical and installation expert for Milliken & Company, which distributes SandMat products, says superintendents need to assess soil conditions and bunker slopes.

“Our products provide a separation media for when it rains,” says Fist. “Water drains through the sand into our liner ... It doesn’t stop the water flow, but it stops the separation. The sand slows the flow of the water into the drainage system.

SandMat is a geosynthetic bunker liner that comes in three levels: SandMat 200, SandMat 350 and SandMat 400. According to Fist, SandMat 200 is the economy product for flatter bunkers and moderate slope, while SandMat 350 is for medium slope, and also where there are more subgrade contamination concerns with clay or gravel. SandMat 400 is the company’s most high-performance, heaviest-weighted product for the most severe conditions for slope and stabilization.

SandMat products, Fist adds, have some of the widest rolls in the industry at 116 inches, almost 10feet wide.

Angle of repose

Fist says another important consideration prior to choosing the right bunker liner begins with understanding the “angle of repose” of your sand. The angle of repose is an engineering property for granular materials and equals the angle a pile forms with the ground. Material with a low angle of repose forms flatter piles than material with a high angle of repose.

“Take the sand that is going to be used in the bunker system and measure the slope of the bunker,” he explains. “You cannot build the floor of the bunker any steeper than the natural repose of the sand. If you match the floor of your bunker with the angle of repose of your sand that you are using in your bunker, you’ve eliminated the potential for slumping and reduced labor that will be involved in maintaining the bunkers over time. If the floor is steeper than what the sand can hold, the sand will naturally slump to its natural state and guys will always be pushing sand back up the face. Bunker liners are not sand magnets.”

Fist also recommends using galvanized staples, rather than steel, during installation. “It’s an investment in the longevity of the product,” he says. “A lot of contractors like to use standard steel staples, and in certain environments, those rust very quickly. Galvanized staples or plastic stakes might be a better option in certain soil conditions.”

A unique choice

Al Schwemler, property manager at Toronto Golf Club, did a complete renovation of the course last summer. The total project cost around $5 million, and one aspect was enhancing and improving the bunkers. They went from 83 bunkers to 90 and put liners in all of them.

“Because we have very sandy soils here, we found when we had major storm events, even with other types of liners we’ve tried, the water would go through the sand and wash it off the faces into the subsoil, which in turn would contaminate the sand,” he explains.

On a pond project a few years ago, the club used a Bentofix liner, (www.bentofix.com). Schwemler says Bentofix is basically clay between a layer of two geotextiles.

“We were still going to have steep-faced bunkers and the other ones [liners] didn’t perform properly for us, so we felt we would still get the washout and contamination in the subsoil,” he says. “I reflected on what our pond was originally done in, which was the Bentofix liner.” Schwemler contacted the Bentofix distributor and explained their proposal.

“They thought we had grown two heads,” jokes Schwemler. “No one had ever done it, apparently, but they said ‘sure,’ and sent us a skid of scraps from other projects. We did a test bunker on our nursery by our maintenance facility, and we had that in two years prior to the start of this project; it performed flawlessly. The sand stays up on the steep faces. We had several major thunderstorms and it stayed in place. There was no undermining of the subsoils, even as the sand got washed off the face of the liner, it stayed clean.”

During the renovation, Schwemler says they only lined the steep faces. The bunker liner was installed by toeing it in along the top of the bunker. They hand-dug a trench and then pulled the liner into it.

“The nice thing about this liner is you don’t have to staple it in,” Schwemler says. “The seams on the Bentofix can be fused together with a heat gun, so there are no staples to go in at all.”

When a representative from the USGA came out to the course, he thought the idea was great, but wasn’t sure Toronto Golf Club should be the guinea pigs. His concern, Schwemler says, was the same with all kinds of liners: if someone hits it with a golf club, what happens? A club could catch it, and the player could injure their wrist.

“We beat the Bentofix up with a wedge and couldn’t make a dent in it though,” says Schwemler.

During the 2009 golf season, while Toronto Golf Club was building the bunkers, they had 16 major thunderstorms. Schwemler says the bunkers that had the liners in worked flawlessly.

“If we didn’t have these liners, we would have probably had to rebuild our bunkers three times this year,” he states. “Being a pond liner, the water is not going to get through it. Water hits the barrier, flows down into a drainage trench, channels water into the drain lines, and then gets rid of the water.”

Prior to this renovation, Schwemler says the course didn’t have a lot of drains in their bunkers, but now every bunker has an extensive drainage system.

Schwemler says, “It’s a permanent liner and a natural product. In theory, it should be there forever.”

Schwemler is still analyzing the costs, but estimates to line the 90 bunkers cost approximately $145,000, which includes all the installation and the cost of the product.

“It’s a pretty novel idea, and it will survive or I won’t,” Schwemler says. “The liners we tried always lasted three to four years. This has been in the ground in our test bunker for three years and we’ve seen no breakdown at all yet.”

Laying Bentofix liner into the bunker face and into the drain lines at the Toronto Golf Club. Once completely laid out, the seams will be sealed with a heat gun. Photos courtesy of Toronto Golf Club. At Toronto Golf Club, the boards have been installed and they’re ready to form the bunker faces over the liner toed in the top of the bunker face.

The author is a freelance writer who has written extensively on the role of superintendents and the issues they face.