Staged works, April 2023 to April 2024. Perfect Contracting delivered the early works and civil works package for a new building at St Ignatius College Riverview, on Sydney's lower north shore, for a Tier 1 builder. The scope ran from the erosion and sediment controls and the topsoil strip through bulk excavation in sandstone, rock trimming, detailed excavation for the footings and lift pit, subgrade preparation and subsoil drainage, to spoil cartage and the new roundabouts and kerbing on the campus road.
The whole job was done on a working school campus. Classes ran, buses came and went and the campus road stayed open around the work for the full twelve months.
Services delivered
- Erosion and sediment control: silt fencing, catch drains, stabilised site access and shaker grid, maintained for the life of the works
- Site clearance, tree removal and topsoil strip across the building footprint and the new road alignment
- Bulk excavation of the building footprint, working down the face of the new piled retaining wall as it was exposed, through fill and residual soil into sandstone
- Rock breaking and trimming of the sandstone formation to the design levels
- Bulk filling and compaction with the excavated material reused where it met the specification
- Detailed excavation for the lift pit, pad footings and strip footings, handed over to line and level for the builder's formwork
- Subgrade preparation to the specified density and subsoil drainage behind the walls
- Spoil stockpiling, classification and cartage off site on Perfect Contracting tippers, clean material to reuse and the rest to licensed facilities
- Two new roundabouts on the campus road: excavation, subgrade, kerbing, centre islands, asphalt tie ins and line marking
- Licensed asbestos removal from the affected areas under an asbestos removal control plan, with clearance by the independent assessor before the earthworks moved in
The challenge
A school does not stop for a building project. The site sat between existing teaching blocks, with the campus road running past the hoarding and the ovals and boarding houses beyond. Truck movements had to work around drop off, pick up and bus times, and the roundabout work had to be staged so the road was never closed to school traffic.
Below the topsoil the ground was fill and residual soil over sandstone, and the excavation had to come down hard against a new piled retaining wall with the existing buildings a few metres above it. The piles and the capping beam were exposed progressively as the dig came down, so the sequence had to keep the wall supported and the working floor draining the whole way. On top of that, some of the ground contained asbestos that had to be removed under a control plan and cleared before the bulk earthworks could start in those areas.
Perfect Contracting's role
Perfect Contracting was engaged by the builder as its earthworks and civil subcontractor and delivered the package end to end: the hazmat removal at the start, the early works and bulk excavation in the middle, and the detailed excavation, drainage, roundabouts and kerbing at the end. Our estimators priced the package from the geotechnical report, the survey and the civil drawings and priced the options the builder wanted to compare, so the scope was agreed before the first machine arrived.
A Perfect Contracting supervisor ran the site through every stage with our own operators, excavators from mini to twenty tonne class, rock breakers, rollers and the truck and dog tipper fleet. The same supervisor and crew carried the job from the first roundabout to the last footing, so the builder had one point of contact for the ground for the whole twelve months.
How the work was done
The roundabouts came first, while the building site was being set up. Each one was excavated, boxed out and kerbed in stages behind barriers, with the centre island poured, the pavement built up and the asphalt tied in, then line marked and handed back before the next section was opened up. The topsoil strip and the erosion controls went in across the building footprint at the same time.
The bulk excavation started once the piled wall was in and the asbestos removal was cleared. The excavators worked down in benches, breaking the sandstone with rock breakers and trimming it to level, with the material sorted at the face: clean sandstone and soil to stockpile for reuse or cartage, everything else out on tippers to licensed facilities. The floor was kept graded so it drained after rain and the working face stayed clean.
Once the floor was at level, the detailed excavation went in: the lift pit first, then the pad and strip footings dug to line and level with compact machines and cleaned out by hand, so the builder could follow straight behind with the reinforcement and formwork. Subsoil drainage was laid behind the walls and the subgrade proof rolled and tested before it was handed over.
Environmental controls
- Silt fencing, catch drains, a stabilised access and a shaker grid at the gate, checked at every pre-start and after rain
- Excavated material classified before it left site, clean material reused on site or sent for reuse, the rest to licensed facilities on tracked dockets
- Dust suppression on the sandstone breaking and the haul road, and the campus road kept swept
- Asbestos removal under a control plan with clearance by the independent assessor before earthworks started in those areas
Safety on a working campus
Everything about the site plan came back to the students and staff moving around it. The work areas were fully hoarded and fenced, truck movements ran under traffic control at the gate, and arrivals were timed outside the drop off and pick up windows. The roundabout work was staged behind barriers with traffic control so the campus road stayed open.
Inside the excavation the wall was the main risk. The dig came down in benches with exclusion zones under the exposed piles, and the exposed depth of the wall was checked against the engineer's requirements as each bench came down. Every stage had its own work method statement, reviewed by the builder before it started.
Civil and early works in Sydney
Perfect Contracting delivers early works, civil works, demolition, hazmat removal and site remediation for Tier 1 builders across Sydney and New South Wales from its Marrickville depot. Earthworks on occupied sites, where the ground has to be dug out around people and buildings that stay, is a large part of what the civil crew does.
The outcome
Two roundabouts built, kerbed and open to school traffic. The building footprint excavated through fill and sandstone to level against the new wall, the footings and lift pit dug and handed over to the builder's programme, and the spoil out and accounted for. Twelve months on a working school campus without stopping the school.
See more Perfect Contracting projects or contact our estimating team.
Perfect Contracting acknowledges the Aboriginal and Torres Strait Islander people as Traditional Custodians of the country on which we live and work. We pay our respects to the Traditional Custodians and Elders past, present and future, and honour their connection to the land and ongoing contribution to society.