How to Select the Best Sandfor Your BunkersThere's a lot to learn about the sand you select for your course.

by JAMES FRANCIS MOORE

Playing quality is unquestionably the most subjective parameter when choosingbunker sand. The most important component in the selection process is allowingan adequate amount of time to fully evaluate the various factors.

WTH THE possible exceptionof green speed, sand bunkersare the most controversial and

discussed features on golf courses,regardless of the golfer's ability. Pre-dictably, opinions vary widely on issuessuch as design, location, playing qualityof the sand, and even what color isbest. Generally, there are four majorareas that must be considered whenevaluating bunkers. These are sandselection, architecture, construction,and maintenance.

Selecting the proper sand forbunkers is arguably the most difficult ofthese four areas. The makeup of thesand strongly impacts maintenanceand playing quality. The sand can alsoinfluence the architecture and style ofconstruction of bunkers.

There are seven factors that shouldbe considered when selecting the sand.

• Particle size.• Particle shape and penetrometer

value• Crusting potential• Chemical reaction (pH) and

hardness• Infiltration rate• Color• Overall playing qualityValues for and interpretation of

particle size, shape and penetrometervalue, crusting potential, chemicalreaction and hardness, and infiltrationrate all should be determined by anaccredited physical soil testing labora-tory. Color and overall playing qualityare highly subjective values that arebased on personal preference.

Particle SizeAs a general guideline, a sand used

in bunkers should be composed ofparticles with a large majority in therange of O.25-1.00mm. Silt and clay(particles below O.05mm) should bekept to a minimum, since they areassociated with surface crusting. Notethat this size range should be utilizedonly as a first step in determiningwhether the sand is likely to be accept-

able overall. In other words, it is un-likely that a sand that falls significantlyoutside this range will perform well interms of crusting, hardness, porosity,and/or playing quality. On the otherhand, it would be a mistake to assumethat a sand will be appropriate forbunker use simply because it fallswithin this particle size range. Forexample, depending on particle shape,some sands that fall in this rangewould be considered too firm or toosoft for play. Since particle sizescreening is a simple, inexpensive testthat is performed by most sandsuppliers, it is the best first step indetermining if the sand is worthy offurther testing.

When evaluating the particle sizerange of the sand for bunker use, keepin mind that bunker sand often endsup on the green in surprisingly largequantities. As golfers blast their wayfree of the hazard, the sand is thrownonto the adjacent green. Therefore,when selecting sand for use in green-

side bunkers, the makeup of thegreen's rootzone must also be con-sidered. The best rule of thumb is toavoid using a sand in the green-sidebunkers that is significantly finer ingradation than that used in the root-zone of the green. This is the same basicrule used for selecting greens topdress-ing materials. You can safely lay acoarser material over a finer rootzonemix without creating significant drain-age problems, but just a few top-dressings with a finer material over amore coarsely graded rootzone cancause drainage problems.If a bunker sand is selected that is

significantly finer in gradation thanthe rootzone mixture used in thegreens, additional aerification shouldbe practiced on the affected areas ofthe green. Backfilling the aerifier holeswith a more coarsely graded sand helpsmover water more rapidly into therootzone.

Material that is too coarse also cancreate problems. Particles greater than

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Table 1Potential for Fried-Egg Lies

(Thomas TurfServices)

Penetrometer Reading Fried-Egg Potential

Greater than 2.4 kg/cm2 Very low tendency to bury

2.2 to 2.4 kg/cm2 Slight tendency to bury

1.8 to 2.2 kg/cm2 Moderate tendency to bury

Less than 1.8 kg/cm2 High tendency to bury

Soil testing laboratories perform apenetrometer test to measure a sand'sresistance to compression. The valuefrom this test is used to predict thesand's potential for fried-egg lies.

2.00mm are classified as gravel. Ifpresent in large quantities, particles inthis range damage mowing equipmentand cause the ball to deflect off line.

Particle Shape andPenetrometer Value

The shape of the sand particles has astrong influence on playing quality andmaintenance. A sand particle's shape isclassified by examining both the rela-tive sharpness of the particle's edgesand the overall shape of the particleitself. By referring to Figure 1- Angu-1arityand Sphericity of Sand Particles,it can be seen that the surface ofparticles can range from very angular(many sharp, well-defined edges) towell rounded (smooth surfaces). Theshape of the particle can range from

low sphericity (an elongated particle)to high sphericity (a particle that isnearly round).

The angularity and sphericity of theparticles have a strong influence onthe playing quality of the sand. Forexample, a low-sphericity, very angularsand generally has high resistance tofried-egg lies. Such sands also tend tostay in place better on the face of thebunker. However, this same sandwould produce very firm bunkers thatsome players may find objectionable.Well-rounded, high-sphericity sandscan produce fried-egg lies and aremore likely to move off the bunker faceduring maintenance and irrigationrainfall.

Sands usually consist of a mixture ofparticle shapes and sizes. This is impor-tant to the stability and playing qualityof the sand. Again, as a general rule,sands that are highly uniform in sizerange and shape (particularly ifrounded with high sphericity) tend tobe less stable than a sand that has awider range of particle dimensions.

Determining a sand's angularity andsphericity is helpful in predicting theultimate playing quality of a bunker, butis by no means an exact science. TheUSGA currently is funding researchto attempt to develop better measure-ment techniques to aid in the selectionof sands for rootzone mixtures andbunkers.

The angularity of the sand is deter-mined by examining the particles witha microscope and comparing them tothe chart in Figure 1- Angularity andSphericity of Sand Particles. Aftermeasuring the angularity, the labora-tory performs the penetrometer test todetermine the sand's tendency to pro-duce fried-egg lies. The penetrometermeasures the sand's resistance to com-pression. The values are reported inkglcm2• The potential for fried-egg liesis based on penetrometer values asdescribed in Table 1 - Potential forFried-Egg Lies (Thomas Turf Services).

Crusting PotentialCrusting is the formation of a layer

of dried, stiff sand on the surface ofthe bunker. Such layers typically are;Is to ~ inch in thickness, and theyseverely decrease the playing quality ofthe bunker. Sands that are prone tocrusting require more frequent rakingto maintain good playing quality. If thecrusting potential is high, the bunkerswill require raking following each irri-gation and rainfall event. This greatlyincreases the labor required to keep thebunkers in good condition.

Crusting is directly related to thepercentage of silt and clay in the sand.As silt and clay increase, the severity ofcrusting increases as well. To test forcrusting potential, the laboratory wetsa thin layer of sand and allows it todry overnight. They then attemptto lift the layer on the edges using aspatula. Whether or not a crust hasformed will be recorded on the lab testresults and is usually reported as N(none), L (light), M (moderate), or S(severe).

Chemical Reaction and HardnessSome laboratories also test the sand

for its chemical reaction (pH). Thisvalue is much less important overallthan the other test results and, on itsown, should not be used to disqualifya sand being considered for use. ThepH value provides insight into thechemical makeup of the sand. A sandwith an extremely high pH (> 8.0) islikely to be strongly calcareous andtherefore subject to physical andchemical weathering.

Sand particles also can change inshape and size due to mechanicalwear. Sand particles that are very softcan be crushed into smaller particlesduring raking. A soft sand may playand drain perfectly at first, only todegrade in quality as the particlesare broken down. Some laboratoriesnow perform a hardness test to deter-mine the likelihood of this type ofdegradation.

Infiltration RateInfiltration rate refers to the sand's

ability to drain. It is also referred to bylaboratories as saturated hydraulicconductivity. This measurement ismost relevant to rootzone mixes foruse in putting greens, but it is also usedby some labs to evaluate bunker sands.

Since straIght sand is used in bunkers,the initial infiltration rate measurementis likely to be very high - often inexcess of 50 inches per hour. As a

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Heavy rains wash soil into the bunker, detracting from the appearance and playabilityof the sand.

Proper s'and selection is one of four components in evaluating bunker sands.An improper choice at this course resulted in cement-like slabs that requiredcomplete removal soon after installation.

their assessment of what constitutesgood playing quality. One of the fewshared opinions seems to be a desirefor all the bunkers on the course toplay in a consistent manner. For thisreason, 'when adding sand to existingbunkers it is a good practice to per-form the work on all of the bunkers onthe course.

From a testing standpoint, particlesize, particle shape, crusting potential,and infiltration rate all provide insightas to how the sand will play. However,other factors that have nothing to dowith the makeup of the sand haveequal if not greater impact on playingquality. The other factors include:

• Raking frequency.• Raking method.• Green-side irrigation coverage.• Depth of the sand.• Length of time the sand has been

in the bunker.The number of times per week the

bunker is raked has impact on playingquality. On courses that rake daily, thepossibility of even minor crusting iseliminated. The upper few inches ofthe sand remains loose. The sand alsotends to be drier as a result of increasedevaporation.

Machine versus hand-raking alsoaffects playing quality. Hand rakingusually results in sand that is firmer andless prone to fried-egg lies. Machineraking can be either deep (useful toprevent weed establishment) or verylight, depending on the attachmentused.

patibility of two sands. An annual taskon many courses is to add an inch ortwo of sand to existing bunkers toreplace what is lost from explosion-typeshots and water and wind erosion. Ifthe new sand is a markedly differentcolor from the existing sand, it can takemonths of raking for the two sands toblend into a uniform color.

Overall Playing QualityWithout question, playing quality

is the most subjective evaluation ofbunker sands. Players vary widely in

general guideline, a sand being con-sidered for use in bunkers should drainat a minimum rate of 20 inches perhour.

Infiltration rate measurements aremore useful when evaluating the suit-ability of a sand that has been in thebunker for some time. In most cases,the sand in the bunker gradually be-comes contaminated with the soil fromthe base and sides of the bunker. Thisprocess occurs more rapidly in bunkerswith steep faces and in areas subject toheavy, frequent rains. A sand that hasbecome heavily contaminated with soiland organic debris will drain muchmore slowly than a sand that is clean.Simply installing new or additionaldrainage pipe would be only partiallyeffective under such circumstances.Complete removal and replacement ofthe contaminated sand may be theonly complete solution.

ColorUnfortunately, bunker sands occa-

sionallyare selected based primarily ontheir color. Although sand color isimportant, since it strongly impactsthe appearance of the course, it shouldnot be given greater considerationthan particle size, particle shape, orcrusting potential.

Laboratories measure the color ofsand by comparing it to the MunsellColor Chart. As a general rule, lighter-colored sands are preferred since theycontrast beautifully with the greengrass. Color measurements are alsouseful when evaluating the visual com-

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Personal preference is one of the most influential factors in bunker sand selection.Allow golfers to try several sands to assess their playing qualities.

Evaluating the particle size range of the sand for bunker use is an important compo-nent in the selection process. A coarse sand will impact maintenance and playability.

Usually, a complete analysis can beobtained for less than $200. The labora-t~ry will need a gallon of dry sand toperform all of the tests. Be sure tosubmit a sample of each sand that isbeing considered. Allow at least twoto three weeks for the laboratory tocomplete the tests.Conclusion

Clearly, there is more to selectingthe right sand for your bunkers thancalling the local sand plant and order-ing a few truckloads. Today's golfers (atleast in the United States) are becom-ing increasingly more demanding ofbunkers that play consistently, drainrapidly, and provide additional beautyto the course. One of the most impor-tant pieces of advice this article canoffer is to remember that time is anecessary component to achieve thesegoals. Allow plenty of time for testingto narrow your choices to sands thatare properly sized, stable, and easier tomaintain. Time also is needed for theconstruction and use of a test bunkerto allow golfers to evaluate the differ-ent sands for playing quality. Finally,time will be required for the newlyinstalled sand to firm up and take onits final playing characteristics.

JIM MOORE joined the USGA GreenSection in 1985, spending his time con-ducting Turf Advisory Service visits inthe Mid-Continent Region. In 1996, heassumed the duties of director of thenewly formed Construction EducationProgram.

constructed to allow golfers to field-testthe sands for themselves. Assumingthree sands are being considered (eachof which has already been evaluated byan accredited physical soil testinglaboratory), use 2 x 6's to divide thetest bunker into three areas. Evaluatethe sands for a period of at least twoto three months to allow the sand tocompact and better simulate what willhappen on the course. Unfortunately,while this testing process will demon-strate the playing quality of each pro-spective sand, it cannot guarantee aunified opinion among the golfers. TheUSGA currently is funding research tobetter predict the playing characteris-tics of sands through laboratory testing.

Several soil testing laboratories pro-vide bunker sand evaluation services.

The green-side irrigation system al-most always overlaps into the bunkers.Thus, during times of the year whenit is necessary to water the greensfrequently, the sand in the bunkers willbe wetter. And, since the irrigationsystem is designed to apply water asevenly as possible to the surface ofthe green rather than the surroundingareas, it is likely the bunkers adjacentto the green will receive varyingamounts of water.

The depth of the sand usually varieseven within the same bunker. The sandis almost always deeper on the low, flatportion of the bunker and shallower onthe faces and slopes. It would be amistake to attempt to maintain a con-sistent depth throughout the bunker.Golfers should gauge the depth andfirmness of the sand while takingtheir stanc,e and adjust their shotaccordingly.

Sands often change significantly intheir playing quality over the first fewmonths as they become compacted andcontaminated with soil and organicdebris. Newly installed sand may seemsoft at first, but soon will become morefirm. The speed at which this firmingoccurs depends on the angularity andparticle sizing of the sand, as well asraking practices. Since most bunkersare subject to at least some erosionduring irrigation and heavy rainfallevents, the sand will gradually becomecontaminated with the underlying andsurrounding soil. As a result, the play-ing quality of the bunker graduallychanges as the bunker ages. The sandparticles can also change in size andshape due to mechanical weathering,as discussed earlier.

Determining which sand yields thebest playing quality is such a subjectiveprocess that a test bunker is often

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