Shoring for a 2,000 m³ excavation with walls up to 9 m high, designed quickly for soft soils, groundwater and crane loads of up to 300 tonnes.
- Client
- Fulton Hogan for Watercare
- Services
- Temporary works design · excavation shoring
- Location
- Pukekohe, Auckland
- Scale
- 2,000+ m³ · 9 m walls · 300 t crane loads
- Status
- Complete 2016
01 / Project overview
The brief
Watercare's Pukekohe Wastewater Treatment Plant was upgraded in 2009, replacing 34.8 ha of treatment ponds with a plant on a 3.5 ha footprint. The next upgrade aims to rehabilitate a wetland and improve water quality in a tributary of the Waikato River, and includes a new wastewater pump station and storage tanks.
In 2016 we provided temporary works design for the excavation to house them: more than 2,000 m³, with walls up to 9 m high. The site combined soft soils, a nearby stream and groundwater, and the shoring had to carry crane loads of 100 and 300 tonnes alongside the excavation.
02 / Our approach
How we delivered it
Deep shoring in soft ground
Walls up to 9 m high in soft soils call for stiff, well-restrained shoring.
Designing for heavy cranes
Cranes of 100 and 300 tonnes worked beside the excavation, so their outrigger and track loads were designed into the shoring as surcharge.
Stream and groundwater
With a stream nearby and groundwater in the soft soils, the design had to manage groundwater effects on the excavation and its surroundings.
The balancing act
Temporary works at an operating plant are a balance of quick design turnaround, safety, reliability, ease of installation and removal, and cost. Our design was developed to meet the contractor's programme while keeping all of those in view.
03 / The outcome
“A 9 m deep excavation in soft, wet ground, shored quickly and safely so Watercare’s new pump station and storage tanks could be built at an operating treatment plant.”
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