This community rugby club is situated on a multi-sports site and the EGRP solution has meant no disruption to either the rugby or cricket season. Indeed, rugby matches were played on the 1stXV pitch the first three weekends of our weekday installation – the picture above shows the game on the third weekend when over 80% of the drilling had been completed.
The 1st XV pitch is situated at the foot of a large sloping agricultural field with a ditch running along close to the touchline to redirect surface water away from the pitch surface. Although this ditch provides partial protection from groundwater, the pitch suffers from localised standing water and has no existing drainage system in place. Our EGRP System has been designed to improve infiltration rates across the whole pitch and to eradicate standing water on the pitch surface. As the principal contractor, GWD also undertook localised pitch levelling in 12 areas where standing water was ponding along with a 24-month maintenance program which includes, over seeding, fertilising, verti-draining and sand spreading.
Once the EGRP has been capped and vertically inserted into the bore hole it then takes 12 weeks for the soil to close in around the EGRP, a period we term as the ”acclimation period” after which the system begins to work. Groundwater finds its way into the system laterally before using the EGRP as an elevator shaft in order to access lower levels of unsaturated soil. Therefore instead of experiencing saturated ground near the surface, this vertical drainage system is helping to equalise moisture content across the depth of the bore hole, whilst the EGRP device stop the bore holes from closing in. This creates a permanent ”Aeration and Fissuring” across the whole pitch surface.
The 16 working day installation commenced on the 24th March 2014 and involved drilling 1,204 bore holes using our Comacchio 3 tonne specialist drill rig. Bore holes measuring 65mm in diameter were drilled to depths of up to 6.1 metres with approximately two thirds of the holes drilled being 1.5 metres deep. These shallower holes accommodate the 1.5m EGRPs which act as ”collector” devices feeding groundwater towards the deeper bore holes for distribution into much lower unsaturated soil strata.
Each device is capped before insertion and is positioned 200mm below ground level. The bore hole is then top dressed with a free draining soil/sand mix before the core of top soil is replaced. This process causes little or no disruption and completely avoids any form of ground settlement post install.
In order to establish the soil type at Harbury RUFC, GWD carried out a desktop investigation of local borehole records and two local surveys were identified, results
• 1985 Geotechnics Survey – found silty clay to 20m with grey brown and blue grey extremely closely fissured with occasional orange brown silt pockets in the upper
These findings were confirmed as drilling commenced. Soil conditions hardened with depth with lower levels up to 6.5m proving hard to drill and producing a fine dusty spoil from the lower unsaturated layers of silty clay.
The Top 200 millimetres
Regular maintenance of the pitch is undertaken to ensure that surface water can freely peculate through the first 200mm of topsoil and reach our EGRP system. Regular verti draining plays an important part in this process as it breaks up surface compaction and aerates the soil.
The Maintenance Programme
GWD works with the client to ensure that a relevant maintenance plan is developed to achieve the optimum drainage possible and assist the EGRP to stabilise the playing area.
For Harbury RFC the first issue was a dozen hollows that were leveled after the EGRP installation late April 2014.
GWD will continue to work with the Harbury RFC on their pitch maintenance programme with fertiliser applications during this summer and verti-draining in September 2014 and April & September 2015.
Post completion of the works, a review of our relationship with Harbury RUFC was undertaken and GWD was scored as exemplary in the following areas :
• Machinery on site/Start on site
• Lack of disruption to playing surface
• Storage of drilling machine & materials on site
• Deliveries to site
• Conduct of operators on site
• Adherence to Programme of Works for install and pitch maintenance
• Overall communication with client.
Harbury RFC signed-off a Practical Completion Certificate for Sport England on the 2nd May 2014.
Performance and Monitoring
As the major funders of this installation Sport England have commissioned PSD Agronomy to measure infiltration rates at regular intervals over the next 24 months.