An Economic Appraisal of Methods to Overcome Surface Drainage Problems on a Golf Course
(9th International Turfgrass Research Conference, Guelph, Canada, July 2001)
Between tee and green, areas of a clay loam texture with little fall (less than 3%) are prone to waterlogging at the soil surface during prolonged wet winter months. Drain lines with porous material to the surface do not readily remove surplus water between drains unless they were very closely spaced (.4-1.00mm apart). In addition drains also have a tendency to become ineffective with covered grass growth and the eventual accumulation of silt and fine sand.
In a comparative exercise, the landing area on a new golf course, prone to excessive surface waterlogging, was reshaped creating swales to lead accumulating surface water away from the playing area while still maintaining a pleasant undulating surface for golf. With the installation of the drains only in the swale inverts there was a considerable reduction in drainage installation. Total costs, which included the replacement of topsoil, soil preparation, seeding and sand dressing on either side of the drain lines, proved to be more economic and effective than installing a grid like system of close spaced drainage pipe lines.
In 1997 a newly constructed Ian Woosnam golf course was opened in Flimwell, East Sussex, England. The entire site was reshaped, the greens seeded to Providence creeping bentgrass and the fairways and tees seeded with Lex 86 and Lorina dwarf ryegrass in a 50:50 mixture. The soil type on the fairways is a silt loam material and in agricultural terms was classified to be slowly permeable (reference Appendix 1). While the grow-in proceeded according to plan with good establishment there were expected drainage problems in low lying areas and in particular in the invert of valleyed or swaled areas.
On the landing area of the first hole the ground was generally level with very minor undulations. A suitable outfall was 90 metres distance. During the winter of 1997-98 this area on the first hole became saturated and some 12 puddles made it unplayable. In order to promote continued play the hole had to be reduced to a short par 4 with tee position beyond the landing area.
Algae developed and the ryegrass died off in the depressed areas to present a disappointing condition. This condition was more severe in the 1998-1999 winter than in the winter immediately after opening the golf course.
No underground water was located within 1.5 metres of the surface. Possible options for overcoming the problem were considered. They included random drains to numerous soakpits, ‘fin’ drains (geotextile wrapped polypropylene moulding 200 x 20mm), gravel band slitting (gravel inserted in slits opened without removal of material) and mole ploughing. After discussion, none of these possibilities were considered acceptable either due to the cost or the short-term relief that would be achieved. The installation of soakpits was investigated, but the deep silt clay horizon made this impractical.
The most successful drainage measures undertaken on waterlogged football pitches has proved to be the incorporation of close spaced slit drains 50mm wide to a depth of 250mm at spacing of 1-2 metres. These slit drains cross over lateral piped drains at 5-15 metre spacing which convey surplus water to main collector drains and on to a preferred outfall. The slit drains comprise 150mm clean stone gravel 5-10mm covered to the surface with a selected coarse sand or grit. (Refer to Appendix 2). The materials were selected on the basis that at least 20% of the grit material should be of particles greater than one sixth of the size of the smallest 20% of the particles in the stone material below.
As a measure of conveying surplus surface water away from relatively impermeable soils in a ‘by pass’ installation it is vital that these slit drains are kept ‘open’ with regular sand topdressings over the drained area. The method was seriously considered and costed (reference Appendix 3). However, apart from the cost, the minor undulations made the setting out of any close spaced drains in a systematic layout impractical it was expected that surplus surface water would not reach all slit drains even at a one metre spacing.
As an alternative operation, the task of removing the topsoil and reshaping the subgrade to create an undulating fairway with positive outfall was then considered. By establishing deepening swales with side slopes not exceeding 20% and fall approaching 5-6% good surface water run-off was assured. With a rough assessment of the amount of machine hours needed together with final preparation, reseeding and the installation of drains in the invert of swales, the overall cost reduction looked significant and the work was undertaken.
The entire area was sprayed with Glyphosate and sufficient time was allowed for complete breakdown of the grass cover. The removal of the topsoil was undertaken with a 12 ton 360o excavator with the aid of a 6 ton tipping dumper vehicle. Preferred equipment would have been a D4 with tilting blade which might have been quicker. Reshaping of the subgrade was roughly planned and shaping incorporated a distinct swale pattern with high and low areas forming an undulating terrain where water from a high point did not have to move more than approximately 15 metres to lower points before being conveyed away in a drain installed in the invert of the swale.
Shaping, grading and topsoil replacing was completed and the installation of drains was delayed until grass cover was fully established.
In the drains the backfill material comprised the stone and grit used in the slit drains. It was intended to cover the immediate area on either side of the drains with an approved topdressing sand to prevent contamination in the upper layers of the drains. This treatment was not immediately carried out and the accumulation of silt and organic matter debris in the drains did impair drainage initially though the surface displacement of water was significant.
In the following dry season the contaminated grit at the surface of the drains was replaced and grass growth was encouraged to cover as quickly as possible. Topdressings with sand have not been as frequent as intended, but immediate stabilisation was significant.
In appraising the established reshaped landing area a year after completion during the winter of 1999-2000 there was no doubt that surplus surface water was quickly removed so much so that the ryegrass covered did not suffer. Naturally there persisted a small degree of wetness around the swale drains where uneven soil surface immediately adjacent the drains prevented water entering the drains.
From the golf standpoint the majority of firm dry elevated areas made play much more feasible. The undulations were not severe enough to produce unsatisfactory lies on the up and down slopes and there was just the little accumulating moisture immediately adjacent the swale drains.
In assessing the comparison in the cost of the two approaches there is no doubt that even at the time of completion of both exercises there was a significant reduction in the cost of reshaping over the installation of the slit drains (reference Appendix 4). Furthermore, the importance of keeping a surface slit drain installation open is labour intensive involving the topping up of drains, which only eventually ceases once grass cover over the drains is complete. There is also the annual costs of sand topdressing added to the costs and effort following the disturbance from rabbits and the displacement of sand from the slit drains by operating mowing machinery over the area.
What has become evident two years on is an apparent settled undulating landscape that gives an impression it was an integral part of the original layout and in no way looks foreign to the balance of the course which as severely shaped in construction.
The only maintenance costs will be the ongoing monitoring of the drains in the invert of swales to ensure they do not become obstructed with accumulating thatch, organic matter debris and silt, but the overall distance of some 150mm drains in total does not present an excessive labour intensive exercise.
Appendix 1: Particle Size Analysis – Local Soil
Topsoil Topsoil Subsoil Subsoil 9F 13F 13F 9F Total organic matter % 27 26 1.2 1.0 fine gravel 5–2.00mm % 3 8 5 12 v.coarse sand 2–1.00mm % 2 2 2 2 coarse sand 1–.5mm % 1 2 1 1 medium sand .5–.25mm % 1 2 2 1 fine sand .125–.06mm % 1 5 4 1 v.fine sand .125–.06mm % 3 4 4 1 silt .06–.002mm % 74 60 64 70 clay <.002mm % 15 17 18 12 ph % 5.9 5.8 5.9 6.0
Appendix 2 : Particle Size Analysis – Slit Drain Materials
10mm clean stone % passing sieve sizes mean maximum minimum 10.00mm 89.09 99.20 81.00 5.00mm 8.25 28.10 1.80 2.36mm 0.56 1.50 0.10
4mm crushed grit % passing sieve sizes mean maximum minimum 16.300mm 99.76 100.00 97.90 5.000mm 98.38 100.00 94.60 4.000mm 96.04 99.10 90.60 3.35mm 92.50 96.90 84.50 2.36mm 78.98 85.70 67.90 1.18mm 44.03 48.70 33.50 0.6mm 20.46 24.60 14.10 0.3mm 8.70 44.00 4.50 0.15mm 3.98 5.10 2.00
Appendix 3 : Area approximately 70m x 40m
Area approximately 70m x 40m
Main line drain 90m of 100mm pipe drainage at £8.50/m 765.00 Lateral drains at 10m spacing 280m of 60mm pipe drainage at £6.50/m 1820.00 Slit drains 50mm wide at 1m spacing 2800m stone/grit slits at £1.30/m 3640.00 Contingency including junctions, transporting equipment and outfall 500.00 Topdressing initially 8mm 50 tons at £15.00/ton 750.00 application 200.00 950.00 ——— £7675.00
Appendix 4: Actual Cost of Reshaping and Drain Installation
Spraying with Glyphosate 100.00 Earthworks charged on a day rate basis included: topsoil stripping and stockpiling reshaping subgrade replacing topsoil and rough grading 2200.00 Contractor costs for final soil preparation and seeding 250.00 cost of seed 300.00 cost of fertiliser 160.00 710.00 Installation of drains in swale inverts (with 150m installed this work was done in-house) cost of piping (150m at £1.00/m) 150.00 cost of aggregates (20 ton at £16.00/t) 320.00 470.00 Sand dressing adjacent drains 20 ton at £14.00/t 280.00 application, say 100.00 ——— £3860.00