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TGMS: An In-Depth Review of the Whitgift School Hybrid Pitch and Playground Project

By Lisa Marie Bruce

Authors:
Dr. Richard Earl, Principal Consultant, TGMS / PSD
Mr. Daniel Ratling, Grounds & Estate Manager, Whitgift School
Dr. James Welsh, Technical Director, White Horse Contractors Limited

BACKGROUND AND OBJECTIVES
Whitgift School is an independent day and boarding school in South Croydon, London with 1550 boys, of which 150 board. The site is an eighteen hectare parkland estate comprising ten hectares of sports facilities and two hectares of gardens and woodland.

Sport is a significant part of life at Whitgift and participation at all ages and abilities is high, with 91% participation at lower-middle school ages. In 2021-22, the school competed in 55 national finals, winning 7 of the core team sports (rugby, football, hockey and cricket) as well as a number of individual titles.

Figure 1. Whitgift School

The school is located in a semi-urban environment and is land-locked with limited space. In order to sustain and develop sports participation and achievement, and to encourage casual play in lunch breaks, the school identified a strategic need to increase the hours of use per week that can be accommodated on the existing limited pitch provision, and also to construct a new playground facility. Two pitches (‘Bigside’ and ‘Puntabout’) were identified for pitch improvement works. Bigside is home to the 1st XV but is also used by other teams down to U13’s, whereas Puntabout is a junior pitch predominantly for younger age groups, but is used by all ages including seniors.

Prior to the pitch improvement works, the pitch surfaces would regularly decline in the winter period resulting in soft, boggy conditions.

Figure 2. Puntabout on 2nd March 2020.

INVESTIGATIVE WORK
TGMS was commissioned by the school to conduct a detailed site investigation and feasibility study, and to assist Daniel Ratling (Grounds & Estate Manager) with the development of a business case for consideration by the senior management team and school Governors. Investigative work included:
• Topographical and geophysical surveys.
• Assessments of pitch orientation and gradients.
• Flood risk assessment.
• Proximity to a groundwater source protection zone (for soakaway suitability).
• BRE Digest 365 soakage tests to inform the design of a surface water drainage system that retains all
water on-site (a likely planning condition).
• The excavation of test pits to characterise the underlying soil and geology to inform pitch and playground design.

Figure 3. An electro-magnetic induction survey and levels survey in progress.
Figure 4. Electro-magnetic survey results.
Figure 5. Levels survey results (0.5 m contours).
Figure 6. Groundwater source protection zones.
Figure 7. Test pit arisings – loamy sand over chalk.
Figure 8. BRE Digest 365 soakage test.

It was concluded that the solution would be to construct a new porous polymeric playground in combination with converting Bigside and Puntabout to the first stitched-hybrid grass pitches in a UK independent school. The rationale for selecting a hybrid grass system was:
• Increased hours of use on turf surfaces from 3-6 hours/week to 15-20 hours/week.
• Reduced likelihood of match cancellations.
• The production of high quality & hardwearing grass surfaces

Figure 9. Schematic diagram of the GrassMaster stitched-hybrid system.

DESIGN
TGMS assimilated the results of the investigative work and developed a design solution which included the following:

New playground
• Establishment of a haul route through an established woodland area with root protection requirements.
• Topsoil strip.
• Cut and fill remodeling earthworks.
• Construction of retaining walls.
• Installation of drainage infrastructure.
• Relocation of fencing.
• Construction of the stone foundation.
• Macadam surfacing.
• Polymeric surfacing
• Colour coating.
• Construction of steps from the new playground up to Puntabout.

Puntabout
• Topsoil strip to temporary stockpile.
• Cut & fill re-modelling earthworks.
• Topsoil replacement and grading.
• In-situ stone separation.
• Installation of a geocellular crate soakaway system.
• Installation of a primary land drainage scheme.
• Installation of a fully automatic irrigation scheme.
• Installation of sand bands at 0.5 m spacing.
• Installation of ACO GroundGuard maintenance access track.
• Installation of a ball-stop netting system.
• Application of base fertiliser.
• Placement of 85 mm of sand and 100 mm of rootzone (sand/soil mix).
• Application of pre-seeding fertiliser.
• Seeding.
• Installation of a GrassMaster stitched-hybrid surface reinforcement system.

Bigside
• Rotary cultivation of the topsoil.
• Topsoil re-grading.
• In-situ stone separation.
• Installation of a linear soakaway.
• Installation of a geocellular crate soakaway system.
• Installation of a primary land drainage scheme.
• Installation of a fully automatic irrigation scheme.
• Installation of sand bands at 0.5 m spacing.
• Application of base fertiliser.
• Installation of rootzone carpet.
• Placement of 85 mm of sand and 100 mm of rootzone (sand/soil mix).
• Application of pre-seeding fertiliser.
• Seeding.
• Installation of a GrassMaster stitched-hybrid surface reinforcement system.

TENDER
TGMS conducted a competitive tender process on behalf of the school which resulted in the contract being awarded to White Horse Contractors Limited (part of the S&C Slatter Group).

CONSTRUCTION PHASE
The construction works were project-managed by TGMS in partnership with the school’s Grounds & Estate Manager. The construction team worked efficiently alongside TGMS and the School to deliver the project on time and to budget. Selected photographs of the construction phase are presented below.

Playground

Figure 10. Tree root protection along a haul route through established woodland.
Figure 11. Excavation down to the formation surface in progress.
Figure 12. Concrete foundation for the retaining structures.
Figure 13. Installation of the Type 3 stone sub-base in progress.
Figure 14. Installation of the L section retaining structures in progress.
Figure 15. Laying of facing bricks along the L section retaining structures in progress.
Figure 16. Facing bricks and a galvanised rail along the retaining structure now complete.
Figure 17. Construction of steps from the playground up to Puntabout in progress.
Figure 18. General view across the playground following macadam surfacing
Figure 19. Basketball goal now installed.
Figure 20. General view across the playground following polymeric surfacing (base course).
Figure 21. Installation of temporary protection of perimeter features in progress
Figure 22. Planter constructed along the northern perimeter.
Figure 23. Steps from the playground up to Puntabout now complete.
Figure 24. Polymeric surfacing of the wearing course now complete.
Figure 25. Polymeric surfacing of the wearing course now complete.
Figure 26. Turf removal through fraise mowing using a Koro Field Top Maker in progress.
Figure 27. Turf removal through fraise mowing using a Koro Field Top Maker in progress.
Figure 28. Chalky subsoil formation surface following topsoil strip and cut & fill remodeling earthworks
Figure 29. Placement and grading of topsoil over the subsoil formation surface in progress.
Figure 30. Installation of an irrigation ring main in progress.
Figure 31. Installation of an irrigation ring main in progress.
Figure 32. Installation of the collector drain in progress.
Figure 33. Backfilling land drains with sand in progress.
Figure 34. Lateral drains installed at 3 m spacing and now backfilled with granite chippings and sand.
Figure 35. Sand bands at 0.5 m spacing now complete.
Figure 36. Importation, placement and grading of an 85 mm deep sand carpet.
Figure 37. Importation, placement and grading of a 100 mm deep rootzone.
Figure 38. Seeding (26/08/21).
Figure 39. Stitching of the hybrid grass system in progress (following seeding).
Figure 40. Close-up of the stitched surface with fibres 20 mm above the rootzone, and newly emerging
grass seedlings.
Figure 41. General view across the site (08/09/21)
Figure 42. First cut in progress (15/09/21).
Figure 43. Installation of the maintenance track crategrass reinforcement system.
Figure 44. Installation of the maintenance track now complete but awaiting grass development.
Figure 45. Installation of a ball stop netting system in progress.
Figure 46. General view across the site following two passes of the fraise mower.
Figure 47. General view across the site following regrading.
Figure 48. Moling in of perimeter irrigation infrastructure in progress
Figure 49. Installation of an irrigation sprinkler head in progress.
Figure 50. Linear soakaway now installed and backfilled with granite chippings.
Figure 51. Installation of the lateral drains at 3 m spacing in progress.
Figure 52. Connection of an 80 mm diameter lateral drains to the 160 mm diameter collector drain.
Figure 53. Installation of Top Drain sand bands at 0.5 m spacing in progress using a GKB Drainmaster.
Figure 54. Installation of Top Drain sand bands at 0.5m spacing in progress with approximately 90% completed.
Figure 55. Importation, placement and grading of an 85 mm deep sand carpet.
Figure 56. Importation, placement and grading of an 85 mm deep sand carpet.
Figure 57. Importation, placement and grading of the 100 mm deep rootzone carpet over the 85 mm deep sand carpet.
Figure 58. General view following seeding (17/08/21) and irrigating ahead of the stitching machine.
Figure 59. Stitching of the hybrid grass system in progress.
Figure 60. Close-up of the stitched surface with fibres 20 mm above the rootzone surface.
Figure 61. Hand stitching around irrigation heads in progress.
Figure 62. General view with natural grass
development through the stitched hybrid fibres.
Figure 63. Close-up of the stitched fibres and natural turf leaves.
Figure 64. General view across the site following the
first cut on 07/09/21.
Figure 65. General view across the on 05/10/21.

POST-CONSTRUCTION PHASE
A Performance Quality Standard (PQS) assessment was conducted on both pitches on the 26th of October 2021 prior to the proposed first use on Friday 29th October 2021.

Figure 66. Assessment of sward height using a prism.
Figure 67. Assessment of grass cover, weed content and earthworm casts using a 0.25 m2 quadrat.
Figure 68. Assessment of thatch accumulation and bulk root depth using a split soil core sampler.
Figure 69. Assessment of surface water infiltration rate using a double ring infiltrometer.
Figure 70. Assessment of surface uniformity using a 3 m straight edge and graduated wedge.
Figure 71. Assessment of surface uniformity using a 3 m straight edge and graduated wedge.
Figure 72. Assessment of surface hardness using a 2.25 kg clegg impact soil tester.
Figure 73. Assessment of traction using a studded plate.

The PQS results, presented below, confirmed that both pitches met the performance criteria stipulated in the specification of works:

PQS Results

HANDOVER AND PITCH USE
The pitches were handed over to the school in September 2021 following 7 and 6 ½ weeks grow-in from seeding for Bigside and Puntabout respectively. What a difference two years make.

Figure 74. Puntabout on 2nd March 2020.
Figure 75. Puntabout on 2nd March 2022.

In autumn / winter 2021-2022 the pitches accommodated ~15 hours of use per week with no cancellations due to rain. There was some natural grass cover loss, but the surface remained flat and stable. From 1st April 2022 until the summer holidays average use increased to more than 30 hours per week.

“I am delighted with the outcome of this project which has created first-class pitches and a new playground ontime and to budget in a working school setting, and has solved a major logistical challenge for the School regarding the provision of sufficient recreational space for our students.”
– Mr. James Stremes, Director of Estates & Facilities

Figure 76. Puntabout on completion.
Figure 77. Bigside on completion.
Figure 78. Bigside immediately before first use
Figure 79. Bigside in use.

Authors:
Dr. Richard Earl, Principal Consultant, TGMS / PSD
Mr. Daniel Ratling, Grounds & Estate Manager, Whitgift School
Dr. James Welsh, Technical Director, White Horse Contractors Limited

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