Bunker Renovation Case Study No. 1

by Patrick O'Brien, Southeast Region Director, USGA Green Section and Tim Kennelly, CGCS, The Farm Golf Club, Rocky Face, Georgia
Submitted February 22, 1999

The 82 sand-faced bunkers at The Farm Golf Club in Rocky Face, Georgia were a nightmare to manage for the past 10 years since the original construction of the golf course. Bunker quality and overall sand consistency was poor due to constant sand washouts that occurred after every storm. Puddles and mud formed on the bunker sand surface and remained for days until the crew could pump out the extra water and reposition the sand with mechanical blades and shovels. During important golf events, the maintenance staff would even rent construction lights to allow work at night since every bunker would have a sand washout. It usually took 60 to 100 labor hours to reposition the sand. Sometimes this task was done 25 times annually during rainy seasons. Even after all this repair work, balls would plug into the soft sand or even be lost. A plan to improve bunker quality and eliminate face erosion was mandated by club officials.

Several golf courses in Georgia and the Carolinas (Table 1) have recently renovated bunkers with a new technique called the "Enhanced Bunker Drainage Method." Billy Fuller of Cupp Design, Inc first came upon this novel idea during his tenure as the golf superintendent at Augusta National. The unique feature is a two-inch gravel blanket over the entire bunker floor. In a traditional bunker, water flows across the soil bunker floor until it intercepts a drainage ditch and tile. If the water moves too rapidly (such as during a heavy rain) it can carry sand particles and soil with it resulting in a washed-out bunker and sand contaminated with silt, clay, and even rocks. With the Enhanced Bunker Drainage Method (Figure 1), water flows through the gravel layer to the drain lines. The movement of sand and other particles is practically eliminated.

Table 1) Popularity Increasing
Augusta National Charlotte Country Club
The Farm Golf Club Cherokee Country Club
Peachtree Golf Club Atlanta Athletic Club
East Lake Country Club Georgian Resort
Hawks Ridge Golf Club Ocean Forest

The following pictures and descriptions illustrate the step-by-step process as it was accomplished.

(1) Regrade the subgrade of the bunker to conform to the general slope of the finished grade.

(2) Check the original outfall drainage pipe on the bunker floor to ensure it still functions. Flushing dyed water through the pipe and viewing its exit at the outlet is essential. If this drainage system doesn't work, it at this time.

(3) The old rootzone was then excavated to a depth of four inches. While the box blade and loader combination was used to remove most of the mix and load it into a waiting truck, the edges of the green had to be excavated by hand.

(4) Install the gravel blanket to a compacted depth of 1.5 to 2.0 inches over the bunker floor. Washed pea gravel or crushed stone with a size of
1\4 to 3\8 inch is preferred.

(5) Install the filter cloth. The 7.5-ounce non-woven Trevira product is the most popular product for this bunker renovation method. Metal staples are used to secure the filter cloth to the bunker floor and edges.

(6) Install the plastic edge liner over the filter cloth liner at the bunker sides. Precut the plastic liner to the desired height. Staple the edging into the bunker sidewall. Eagle Products manufactures a popular liner that's ideal for this purpose. It is the same product used for the interface moisture barrier at putting greens.

(7) Cut the filter cloth over the drainage lines on the bunker floor and install Enkamat. Placing the Enkamat over the drain lines prevents clogging and ensures water flow to the drainage tile.

(8) Install the bunker sand to a compacted depth of 4 to 6 inches.

(9) Turn water away from the bunker (if needed). Any surface water flowing into the bunkers can cause minor washouts if not diverted.

This unique building method solves many bunker renovation concerns. The filter cloth is secure on the bunker floor and edges with metal staples. No tucking of the filter cloth is needed due to the placement of the new plastic edging product. Bunker edging has been simplified with the permanent edge barrier system observable for workers that allows trimming without damaging the filter cloth. Drainage is maximized with the Enkamat product over the drain lines. Sand is not piled to depths of 2 to 4 feet on the bunker faces anymore. Little or no new sod is required after the renovation in most instances. The original bunker design is kept intact for years with proper maintenance.

This bunker renovation method is more expensive compared to traditional methods. Costs are similar to building a putting green. Construction is practically all done by hand work and wheel barrels. The higher cost will be offset by a huge reduction in labor and sand replacement costs. A contractor should be hired to renovate all bunkers, but "if you only have 10 or less bunkers to remedy, most maintenance crews can handle this project," said Kennelly. However, a good size crew is required to tackle this extra work.

Today, we have a solution to remedy the age-old problem of bunker washouts. Next year, bunker maintenance costs will be reduced dramatically with only two to three workers hand raking and checking sand depths. Using this easy formula can keep your bunkers on the right track.

Important Note - Liners have been tried in bunkers for many years, often with poor success. Most problems have stemmed from their use on steeply sloped bunker faces, the use of liners in conjunction with mechanical bunker rakes, and the failure to maintain the sand in the bunker to a sufficient depth (at least 4 inches).

When liners are used on steep bunker faces (where the sand is often shallow (less than 2 inches deep), it is possible for the player to contact the liner when he/she digs in for the explosion bunker shot. There is also the possibility of hitting the liner with the club.

When mechanical bunker rakes are used, great care must be taken to keep the machinery off the steeply sloped areas of the bunker. Also, plow attachments (used to prevent the sand from crusting and to prevent weed seeds from taking root) should not be used. The most severe problems with liners occur when the liner is snagged by the mechanical rake and pulled to the surface. For these reasons, hand raking is preferred when liners are utilized. At the very least, the steep bunker faces should be raked by hand, a practice that should be employed whether or not a liner is used.

Contact with the liner by players or by equipment can be greatly reduced by maintaining a minimum depth of 4 inches of sand anywhere a mechanical rake is to be used (typically in the floor area of the bunker). On steep faces where hand-raking is utilized, the depth should be at least 2 inches.

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