The City of Newcastle’s storm drains were operating at capacity and could therefore not afford take any extra run off from storm water events. This was a large hurdle in the planning application of the all-weather hockey pitch proposed by the Girls Day Schools Trust (GDST) on behalf of Newcastle High School for Girls. The drainage system to be installed in conjunction with the pitch would have to retain all storm water on site and not allow any run off to the city’s storm drains. Groundwater Dynamics’ EGRP (Energy Passive Groundwater Recharge Pump) system was recommended by STRI as the preferred solution for keeping all water on site as opposed to a traditional drainage system which diverts storm water into the city’s storm water drains.
All Weather Pitch Formation
Groundwater Dynamics worked in conjunction with CLS (Cleveland Land Services), a respected groundworks contractor and sports facility installer in the North East and across the UK. CLS initiated the project by removing the top soil from the proposed site of the all-weather pitch and grading it off to create a level surface on which to begin installing the EGRP and later build the artificial playing surface. GWD used 4 specialist drill-rigs simultaneously in order to get the large quantity (1325) x6 meter EGRP devices in the ground within the relatively small amount of time allocated for drainage works.
There were two significant parts of the EGRP design.
Phase one of the design was the 1250 6m long EGRP devices evenly installed across 7000sqm playing surface. For each device an 89mm diameter bore hole were drilled into which three interlocking devices inserted 300mm below formation level and backed filled with 20mm gravel. This first part of the design deals with normal and prolonged rain fall events.
Phase two of the drainage installation comprised of a linear soakaway trench 88.5 meters in length which took water out of 4 lateral drains spanning the width of the pitch every 20 meters. The soakaway also had 45 6 meter devices installed in the base every 2 meters and 90 3 meter devices either side of it at 1 meter spacing. The 1.5 meter deep x 0.3 meter wide soakaway, combined with the lateral drains across the pitch and the extensive amount of vertical EGRP devices provide enough storm water storage/retention to deal with a peak rain fall event designed to a 100 year storm even plus 30% for climate change in order to prevent any build-up of water in the sub base.
The Principal Contractor were able to lay their type 3 sub base as the installation across the 7000sqm surface progressed, enabling them to remain on of schedule.