A bunker renovation is an opportunity to address aging infrastructure, replace contaminated sand, and install a modern liner where necessary.
If there is ever a doubt about the role bunkers play in golf, one should look no further than hole 17 on the Old Course in St. Andrew’s. The road hole bunker, arguably the most famous bunker in the world, provides strategy for every shot hit while playing the hole, challenge, and aesthetic beauty – the big three in golf course architecture. Despite the positive attributes of bunkers, they also can be a source of frustration because of their complexities around playability, design, construction, and maintenance.
Regardless of your feelings about bunkers, they all need to be renovated at some point, even the road hole bunker. Bunker renovations are on the rise worldwide, in part because increased participation in the game has provided an influx of capital resources at many facilities. In most cases, the motivating factors to perform bunker renovations include:
- Improve playability and consistency
- Reduce bunker area (m²)
- Reduce maintenance costs
- Replace contaminated sand
- Install new drainage and liners where necessary
- Establish stronger turfgrasses on bunker surrounds
- Make architectural changes
The cost and disruption of bunker renovations is significant, and most courses can’t afford to make a mistake with these types of projects. This article aims to cover the factors that impact bunker performance, the latest trends in bunker construction/liners/sand selection, and the keys to a successful renovation project.
Bunkers add strategy, aesthetic beauty, and challenge to golf courses.
Factors Impacting Bunker Performance
When planning a bunker renovation, it’s important to start by reviewing the primary factors that impact bunker performance – design, drainage, sand, and maintenance practices. These factors are not of equal importance. For instance, a high-quality silica sand will play poorly if drainage water flows into a bunker or pipes within the bunker are malfunctioning. Conversely, a lower quality sand could play beautifully with a good design and ample drainage. Design and drainage are paramount.
Raking techniques, regular sand depth checks/redistribution, and removing debris from grass clippings and leaves influences daily bunker conditioning, but maintenance practices cannot overcome infrastructure or design issues. Addressing infrastructure and design issues is a critical aspect for any bunker renovation to be successful.
Design and Maintenance Implications
A golf course architect can design and build extremely attractive and strategic bunkers, but if they can’t be maintained to the required level the project won’t be a success. The number, size, and style of bunkers has a significant impact on the required maintenance and long-term performance of bunkers. All bunker renovations should include an anticipated budget for maintenance. This is especially important when the bunker design style is changing. Switching from sand flashed faces to grass faces requires a significantly different maintenance plan, with the latter usually costing 25-50% more annually. In addition, stylistic changes such as going from a curvilinear edge to a more irregular/jagged edge will require more maintenance resources. The best place to start is to calculate the maintenance costs for existing bunkers, and then work closely with an agronomist to develop an agronomic plan for the renovated bunkers. A time and motion study can also be performed to predict the labor hours required for all bunker maintenance tasks.
Bunker Area Reduction
Famed architect Alister MacKenzie once said “on many courses there are far too many bunkers (MacKenzie, 1920).” This statement remains accurate a century later. Fortunately, bunker area reduction is a part of most bunker renovation projects today. The motivation to reduce bunker area is two-fold – reducing maintenance costs and creating more strategy/options for players. Reducing bunker area by as much as 30 to 50% is common, and there have been a few projects recently that eliminated bunkers entirely, creating strategic interest primarily from contours. It seems straightforward, but reducing bunker area is more complicated than most envision, so hiring an ASGCA/EIGCA golf course architect is strongly recommended.
Reducing bunker area is a common aspect of most bunker renovations projects.
Drainage
Unless your course has world-renowned architecture the likes of Royal Melbourne or Pine Valley, surface water should not drain into bunkers. When this occurs, bunkers will washout during storms and become contaminated from silt or clay, reducing their life expectancy and long-term performance. Directing surface water away from bunkers is an effective method for limiting washouts, however this method is not always in keeping with the architects plan. Liners may help reduce washouts, but they cannot prevent them when surface water flows directly into a bunker. Adequate internal drainage is also vital. Bunkers with poor internal drainage are prone to a wide range of issues, including poor playability, washouts, and contamination.
Bunker with poor internal drainage are prone to poor playing conditions, washouts, and contamination.
Liners
Liners have become an important and costly component of bunker construction. By minimizing contamination and washouts, liners can improve playability, reduce maintenance, and extend the life expectancy of bunkers. A brief overview of various liners on the market is provided below, but there are dozens of factors that need to be considered when determining which liner to use, or whether a liner is necessary at all. Collaborate with a skilled agronomist, an experienced builder, and a golf course architect to understand if the design warrants a liner and if so, which one to use.
Porous Aggregate Liners
Porous aggregates such as stabilized gravel – e.g., Better Billy Bunker – and porous concrete – e.g., Capillary Bunkers – have become popular liners worldwide. These liners serve as drainage layers and help hold sand on bunker faces. In addition, they eliminate contamination from the subsoil and are more durable than most other liner options. Some have expressed concerns over the durability of porous aggregate liners in cold climates, but problems with cracking have not been widely reported when properly installed.
Porous aggregate liners are becoming popular choices worldwide, but sand depths need to be tested to avoid problems with sand staying too wet.
It’s important to acknowledge that porous aggregate liners create a perched water table due to the difference in particle size between the sand and aggregate. This can result in sands staying wet and the formation of algae. First and foremost, proper sand depths determined by a water release curve is the most effective strategy for minimizing the effects of wet sands near the surface. Leaving gaps in low-lying areas when using porous aggregate liners can also help overcome issues with sands staying too wet due to the perched water table. Sinking drainage trenches deeper than usual to allow for 8+ inches of sand immediately over the drainage trench is another method used by contractors and golf course architects. However, leaving a gap in the liner or having deeper drainage trenches may not be necessary if sand is installed at the proper depth from the onset.
Porous aggregate liners cannot be installed on a vertical bunker edge, so rolling sod over the edge is often necessary to prevent soil contamination. Synthetic turf materials like EcoBunker and DURAbunker can connect with porous aggregate liners to seal the bunker if a grass lip isn’t desired.
Synthetic Turf
Synthetic turf can make for a very effective bunker liner in the right situation. They act as a barrier from underlying subsoils and help reduce washouts, but these liners don’t serve as a drainage layer. Water travels through the sand and liner down the slope to the drainage pipe that is exposed or above the liner. A frequently cited benefit of synthetic turf liners is the fact that they don’t create a perched water table.
Bunker Solutions and Zline are two of the newer synthetic turf liners on the market. These three-part liner systems have slight variations with their drainage design and bunker edge. The material is flexible, which may be appealing for those worried about frost heaving or golfers hitting the liner when playing from a bunker. When possible, contractors orient the synthetic turf fibers up the slope, potentially holding sand on faces better.
Synthetic turf can make for an excellent bunker liner.
Fabric
Fabric liners – e.g., Sandtrapper II, SandMat, BunkerWool – were the industry standard at one point due to their ability to reduce washouts and contamination. Drainage is not enhanced with these products as water generally travels through the sand to drain lines, which can contribute to washouts. Tearing and material clogging issues can be difficult to prevent with fabric liners, but these can still be a good option in the right situation because of their affordability.
Porous Rubber
Porous rubber liners utilize crumb rubber mixed with a binding agent – e.g., Blinder and Sand Guard – or are delivered as sheets – e.g., PolyLast – that can be rolled, cut to size, and secured to the subgrade. Porous rubber liners act as a drainage conduit like porous aggregate liners but they are flexible. A perched water table is to be expected with porous rubber liners, but anecdotal observations suggest it may not be as noticeable compared to porous aggregate liners.
Hybrids
Hybrid designs usually include a combination of two liners or just installing a liner on the bunker face. Hybrids seem to be used most often when there is a desire to avoid perched water or save costs.
Product Testing
There are many additional liner options that could be considered for a bunker renovation including the use of sod. When preparing for a bunker renovation, testing a few different liners along with different sands is very helpful to learn how they perform at your site. This information coupled with input from an agronomist, builder, and architect will help you make the best decision about liners.
Sand Selection
Sand selection should be specific to the bunker design style and site. Shipping sands from hundreds of miles away may produce excellent results, but a local and significantly more affordable sand might work well depending upon the design style. Evaluate bunker sands through a combination of on-site testing and laboratory analysis. The soil physical testing should focus on particle size analysis and particle shape, but other valuable tests are uniformity coefficient, infiltration rate, penetrometer data, angle of repose, crusting potential and set-up, acid reaction, and a water release study. Laboratory tests should be compared to onsite evaluations of a test bunker since that is the best way to understand the true playability of a given sand. The color of the sand has no impact on the physical performance of a bunker. However, bright white sands may show imperfections quicker than buff or tan-colored sands and thus may need to be replaced more frequently.
Conclusion
A bunker renovation can transform a golf course by enhancing course aesthetics, creating more strategy, improving playability, and reducing maintenance. The keys to success include replacing aging infrastructure, proper construction, and accounting for the appropriate level of maintenance/resources required after the work is complete. Bunkers have a relatively short life expectancy, but there usually aren’t second chances if a renovation doesn’t go well. Research, planning, and working with an experienced team consisting of an agronomist, golf course architect, and builder is the best way to ensure long-term success.
References
MacKenzie, A. 1920. Golf architecture. Simpkin, Marshall, Hamilton, Kent & Co. Ltd. London.
About the Author
Adam Moeller
Director of Agronomy – North America
Adam Moeller is the former director to the USGA Green Section Education and editor-in-chief of the USGA Green Section Record digital magazine. He has consulted with over 330 golf courses and collaborated with host superintendents to prepare 22 USGA national championships, including prestigious events like the U.S. Open and U.S. Women’s Open.
Adam is a highly accomplished individual with a Bachelor of Science degree in Horticulture from the University of Wisconsin and a Master of Science degree in Agronomy from Purdue University.
He is widely recognized as an industry leader and authority in his field, developing educational content for golf course superintendents, course officials, and golfers.
Due to his sought-after expertise, he frequently presents on golf course maintenance topics at turfgrass conferences in both the USA and at an international level.
In his free time, Adam loves to spend time with his wife and two sons. As an avid snowboarder and golfer, he enjoys seeing his young sons become interested in these sports.