5/2020 – Taking a school sports field to new heights

Fill slope stabilisation with Terraforce

In June 2019, St Cyprian’s school in Oranjezicht, Cape Town, ZA, received the great news that they had the go ahead to upgrade the Upper Orange field into an international standard hockey field.

The lower end of the field is supported by a composite Terraforce retaining wall

The lower end of the field is supported by a composite Terraforce retaining wall

Urban renewal for St Cyprians School

The school, together with Good Hope Seminary School, has enjoyed use of the Upper Orange Field as a hockey venue for almost a decade. Plans were submitted to the City of Cape Town to upgrade the field and replace the existing surface with synthetic grass, commonly referred to as Astro turf.

St Cyprian’s applied to lay a Hockey 20 ND sand-based Astro turf. Each potential location is thoroughly researched by Synsport, synthetic sport surface specialists. Based on geo-technical details particular to the Upper Orange Street site, the turf was installed on top of a sealed slurry base.

The Boundaries of the field proved too narrow to allow for any sloping around the field and the natural ground level followed that of the steep mountain, so getting a level was unobtainable using cut to fill methods.

Terraforce walls up to 2m and 5m high

Says Lucas Stiger, Civil Engineering Technician, Isidima Civils, a Cape-based civil engineering firm and empowerment vehicle of Martin & East Group: “The job required us to build a concrete block wall at heights anywhere between 2m and 5m at angles ranging from 65 to 85 degrees. The retaining wall would need to retain 1900 tons of G7 fill so that the last 30 meters of the field could fit within the boundaries and have no forms of slope failure or settlement as the field tolerance was only 6mm.

Terraforce walls at the new St Cyprians Hockey field

Terraforce walls at the new St Cyprian’s Hockey field

Three exposed fill slopes needed earth retaining walls

Three exposed fill slopes needed earth retaining walls

Terraforce. Proven eco-friendly retaining system

Ultimately, Terraforce was specified – as a proven and eco-friendly earth retaining system – by Isidima to provide the earth retaining measure for the resulting steep slopes. Says Stiger: “Terraforce walls are cost effective and if built right, structurally sound. The client was required to design the field with heritage aspects and feel, which was achievable due to the many options Terraforce can provide.“

Stiger adds: “to begin installation, we cast a base of 25mpa and backfill with G7 in layers behind the blocks. Every second or so layer required geofabric out to spans of approximately three meters. Behind the wall subsoils and outlet pipes were installed every two meters apart and wrapped with bidim. Where the walls transitioned to 85 degrees, we were required to backfill the blocks with concrete and fix steel within the blocks.”

Happy clients!

Isimida completed installation late November 2019 and the first few matches were successfully played at the end of the last school term, getting the thumbs up from all around. Says Marelize DeKlerk, Facilities Manager, St Cyprian’s School:

“We are very happy with the Terraforce wall, and the landscaping that will take place once schools reopen will finish it off beautifully, although, I do like the clean look too – it is growing on me! To me it makes a statement of the enormity of that project and add something special to the look and feel of the Astro!”

Project team

Engineer: Integrate structural and Civil Engineering

Quantity Surveyor: Zaandre Bredenkamp/ Lucas Stiger

Wall Design Engineer: Fred Laker, Icos Engineering

Main Contractor: Isidima Civils / Martin & East

Taking a school sports field to new heights with Terraforce

Taking a school sports field to new heights with Terraforce

A special thanks to Isidima and Martin & East for a job well done!

For more details on the technical aspects of the project, watch the Interview with Lucas Stiger, Civil Engineering Technician and Hilton Mc Neill, Site Engineer, Martin & East:

And some stunning drone footage, courtesy Martin & East: