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An Holistic Approach to Construction

Tuesday 06, Aug 2019

 

In recent months AGCSATech has been involved with consulting, designing and overseeing a number of construction projects as well as discussions with companies prior to the start of major works. In some cases the quality of the final job appears to be very much price orientated, which is a major pressure point for may Turf professionals charged with maintaining the end result.

There is no doubt that not every client has an infinite budget, however, there are certain decisions that must be taken, even if the cost is increased, that will ensure a much better end result.

While an acceptable turf playing surface can be achieved with minimal inputs, it is very dependent on the time of year, grass variety and the amount of usage it will receive.  Winter months in southern Australia provide the most hostile environment for most playing surfaces, whether it’s golf course fairways, greens or sports fields.

This is generally due to their accumulated organic matter, the type of soil present and the presence/absence of adequate surface fall and subsurface drainage. 

The decision makers who chose not to install subsurface drainage, install rootzones with minimal depth or those that lack sufficient surface fall may have playing surfaces the provide suitable surfaces during dry weather but soon become saturated and poor in periods of wet weather or high levels of usage.

The base-ics

Base construction is critical in the formation of any playing surface whether it be a golf green, sports field or racetrack. Establishing a firm, solid, flat base is crucial for the long-term success of a playing surface. With the use of GPS, achieving the desired shape and fall on bases should be relatively straight forward these days, even with cut and fill operations. There is no doubt that rock will always be an issue in certain regions, however, it is hoped that this would have been identified prior and tabled in the geotechnical engineer’s report. 

Encountering soft spots within base construction can be an issue especially on clays where there is differing subsurface moisture contents. Excessively wet areas will be susceptible to soft spots and these must be ripped and allowed to dry before final compaction. In some cases the use of lime stabilisation may be required to ensure these areas meet the required compaction tests.

Irrigation is a crucial component of all playing surface establishment and maintenance. Even with the conversion of cool-season grasses to warm-season grasses on many sports fields and fairways, irrigation is still a required component. Installation must ensure that the base shape and compaction is not compromised and all spoil is removed, leaving the base firm and flat prior to sand placement.

The re-compaction of lateral and main lines is of the utmost importance. Irrigation laterals should also be installed deep enough so that if a decision in later years is to install subsurface drainage this can be undertaken without jeopardising the entire irrigation system.

Irrigation systems need to be checked on a regular basis to ensure optimum performance.

 

This can be as simple as ensuring all sprinkler heads are rotating, to checking nozzle pressure or even undertaking a catch can test. It is amazing when flying into a national capital during summer how many sporting fields have visible signs of poor irrigation uniformity.   Turf Managers wanting to review irrigation performance to ensure uniformity, can utilise the NDVI and NDRE drone service solutions available from AGCSATech

While a few may have been installed poorly, it is more likely that the original pressure obtained at a certain site has reduced and the ability to attain uniform coverage has been impacted.

While some sports fields are choosing not to install subsurface drainage at the time of construction, there is no doubt that fields with drainage installed will provide enhanced playing surface quality during prolonged periods of wet weather. This, however, does rely on correctly spaced laterals and the ability of water to enter the drains. Unfortunately though, not even correctly spaced drains will guarantee successful drainage. 

During construction the most common problem exists with contamination of the drainage lines with the clay base material, particularly around the joins, or fine clay particles migrating into the gravel prior to sand placement.

Issues that develop over time are usually caused through lack of adequate maintenance in terms of depressions developing between drainage trenches or excessive thatch accumulation over the drainage trench. Drainage is an essential component to sustain suitable playing conditions during wet weather but must be strictly monitored during construction and then adequately maintained post construction.

 

Ingrained

Sand selection is generally the most critiqued item in any construction with the three most critical components being particle size distribution, hydraulic conductivity and moisture retention. The particle size distribution and particle shape will define the characteristics of the sand’s performance. 

It must be noted though that hydraulic conductivity (drainage rate) and moisture retention (measured as volumetric water) are not directly related. The drainage rate of a sand is dictated by the amount of macropores within the sand, whereas volumetric water will be determined by the amount of micropores and retention of water by capillary forces. All sands will have differing percentages of macropores and micropores depending on its particle distribution and shape. 

The drainage rate of a sand must be known as part of the selection criteria, as must its moisture retention. It cannot be assumed that a sand within an acceptable drainage rate will have an appropriate level of moisture retention or that a sand which may have a high drainage rate has insufficient moisture retention. The two, as stated previously, are not directly related.  

It is critical though that whichever sand is selected that it remains consistent throughout the project, whether it be building a bowling green, a sports field or 18 golf greens over a prolonged period. The USGA has formulated confidence intervals for quality control testing (Google ‘USGA Guidelines for Establishing Quality Control Tolerances’) and it is strongly recommended that these are included in any construction specification and adhered to with testing of stockpiles in a minimum of 1000 cubic metre batches. Those percentages stated can be used to formulate an allowable window for which all subsequent stockpiles must conform to.

Sand placement should be one of the more straightforward processes in the construction, however, it is imperative that trucks delivering the sand do not travel onto the base as this may compromise surface levels and at the very least lead to differential compaction. Again, with the use of GPS, forming the desired finished shape should be relatively straightforward and if placed over a well constructed base the depth of sand should be consistent throughout the playing surface.

Prior to the sign off of any sand placement it is imperative to check final levels and consolidation especially around the perimeter of the field/green or sprinkler heads. Those areas are the most susceptible to settlement as they tend not to be well consolidated during the placement process.

 

The green stuff

The majority of sports fields in construction projects today are established with warm-season grasses, namely kikuyu or couchgrass, and again depending on budget and time constraints will either be solid turfed or sprigged. 

If solid turfing is to be undertaken it is imperative that a heavier soil type is not imported with the sod.

Previously, washed turf was seen as a mandatory requirement, although in recent years sod has been laid that has been unwashed but grown on a sand.

This is acceptable although it is vital that even with the sand ‘backing’ that a hollow coring is undertaken prior to the first winter and immediately topdressed with the same construction sand to ensure the drainage through the sod is not restricted by that imported sand layer.

Establishing an area with sprigs should not encounter the same interface issues, however, the sprigs must be well incorporated into the growing medium and consistently watered to ensure a successful strike.

It should be noted that if sprigging into in-situ material or a sand that has been incorporated with in-situ material that the likelihood of weed germination will be a major threat to establishment. In this case the use of a turf registered pre-emergent herbicide would always be highly recommended, although it must not be a root-pruning herbicide (Group D chemical). 

 

Renovate, renovate, renovate


Ensuring that a high level of quality has been achieved throughout the construction process in terms of the specification and project management does not guarantee life-long success of any sporting surface, let alone a natural turf surface. It is amazing how many playing surfaces have poor drainage irrespective of the lengths of quality control that may have been undertaken during the construction process. The main reason for this is generally excessive thatch/organic matter accumulation either from lack of renovation opportunity or the cost of undertaking the works.

In recent times AGCSATech has tested the drainage rate of a number of greens with an in-situ disc permeametre to discover their drainage rates are less than 1mm per hour irrespective of their construction sand, simply because there is such an accumulation of organic matter present. 

AGCSA superintendent member Idris Evans from The Western Australian Golf Club in Perth posted some interesting photos on Twitter showing an aggressive coring regime he was trialling on a section of his chipping green. The image showed the green having been cored with 5/8” tynes at 2 x 2 inch spacings, topdressed and then immediately re-cored at 2.5 inch spacings. 

The total area of such a coring event would be 13 per cent of the total area (eight per cent with the first pass and another five per cent with the second) assuming there was no overlap of coring holes. Even with that coring regime it is still less than proposed by O’Brien and Hartwiger (2001) who state that, in their experience, golf courses with successful mature greens have been on a core aeration program where 15-20 per cent of the surface area has been impacted each year. To further increase the amount of core aeration, 4mm ‘Ninja’ tines could be used on a monthly basis through late spring/summer, depending on the severity of the season.

While Evans did not complete the whole course utilising the double coring due to concerns of overlapping core holes and the additional time for that hole then to repair, he did core at a spacing of 1.5 x 2 inches utilising 5/8” tines, pulling out the equivalent of 10.5 per cent of the area, although the photograph would appear far more aggressive. 

There is no doubt that multiple corings of golf greens in particular is becoming more challenging in terms of not disrupting the golfing calendar (in this case or sporting calendar in general) so it is important to maximise the amount of material that is removed when the opportunity arises. It must be remembered that a single 5/8” hole every three square inches (2 x 1.5 inch spacing) will take just as long to recover as a single 5/8” hole every five square inches (2 x 2.5 inch spacing) yet remove 60 per cent more material. Adjusting the core hole spacings can be very good to remove differing amounts of material from greens depending on the amount of accumulated organic matter. 

The best way to check organic matter accumulation is by undertaking loss on ignition (LOI) testing whereby a sample of the greens profile, usually 0-20mm and 20-40mm deep from the surface, is ashed at 650oC to calculate the percentage of organic matter present. Obviously if you have greens of differing ages the difference in organic matter accumulation may be more obvious but a LOI test gives you an accurate figure. 

 

Many new golf courses have greens that are different ages and utilising differing core spacings is a very good way to alleviate those differences to produce a more uniform putting surface across all greens. In saying this, on a recent overseas trip I was fortunate enough to inspect a new golf course being built in Doha. There they were covering their newly constructed greens with tarpaulins until all the greens were ready to sow at the same time, minimising not only issues with management (i.e. mowing and watering regimes) but also negating any issues of differing green maturity.

 

In Summary

Providing high quality playing surfaces relies not only on adequate funds but well written specifications, attention to detail during construction and establishment, strict project management and thorough ongoing maintenance. Turf surfaces are dynamic and their playing condition extremely vulnerable to climatic conditions and usage, but their variability will be determined by the decisions taken prior to construction and their subsequent management.