A project the size of Auckland’s City Rail Link generates a huge amount of material waste in the centre of the country’s largest CBD. Getting rid of that resource is a challenge.
The first two CBD-based contracts for the City Rail Link project are well advanced – tunnel construction at Lower Queen Street and under the existing Britomart station (C1 contract), and a 350-metre long cut and cover trench for the rail tunnel under the northern end of Albert Street (C2 contract).
A third contract, C6, involves the excavation of a new stormwater main at Mt Eden. Construction of the substantial C3 contract – completing the 3.45 kilometre-long tunnel and building two underground stations – will start in the new year.
The CRL’s manager who oversees this waste is Liz Root as the project tracks waste from the contracts currently in construction, two of which (C1 and C6) have significant demolition elements to them in addition to typical construction waste.
To date, 7784 tonnes of C&D waste have been produced, and 6540 tonnes of that – 84 percent – has been diverted from landfill.
The larger C1 and C2 contracts have achieved 97 percent and 95 percent diversion respectively, with most of the waste sent to landfill coming from the demolition of two buildings that were removed to make way for the C6 tunnelling.
“The focus on waste minimisation stems from the adoption of Auckland Council’s goal of zero waste to landfill for all our contracts,” says Liz.
“For the larger C1, C2 and C3 contracts we are also pursuing the independently verified Infrastructure Sustainability (IS) rating, which includes waste targets for spoil, C&D and office waste.
“These targets are included in tender and contract documents, and the achievement of them incentivised through KPIs. All contracts report monthly on their waste generation and diversion.”
Liz adds that there are several steps in CRL’s waste minimisation process and the first step, of course, was to have targets from the start.
Contracts 1 and 2 had Early Contractor Involvement (ECI) phases when Waste Avoidance and Resource Recovery Management Plans (WARRMPs) were developed with contractors, while for C6 a waste plan was developed after the contract was awarded but before works started.
“This helps us anticipate what waste will be generated, how that might be avoided, and then how unavoidable waste can be dealt with without sending it to landfill.
“During the ECI phase for Cs1&2 we also visited operations such as Green Gorilla and Green Vision to help inform the waste plans,” says Liz.
“For C1, which involves the demolition and then, once tunnelling work is complete, the reinstatement of the interior of Britomart Station, we also created a re-use register for items that can be re-furbished and re-used.”
Contractors have primary responsibility for ensuring the plans are followed and targets achieved under monitored plans and targets. At the same time CRLL is involved, for instance, with Auckland Council and the two Community Recycling Centres (CRCs) to identify building demolition items for CRCs to sell either at their stores or online.
Temporary works are used as an opportunity to reduce waste and cost by minimising the amount of materials used and designing temporary works so that they can be safely removed and re-used afterwards.
One example is 375 tonnes of temporary propping steel that C2 removed and sold at a premium for re-use rather than the low value that could have been paid for scrap.
C2 has also been able to reduce cost by using recycled crushed concrete (45,500 tonnes to date) as backfill instead of virgin aggregate. This has the added benefit of generating a demand for recycled material.
C1 has not decommissioned any temporary works yet, says Liz, but all the steel procured for temporary works has been permanently marked with an identifier to easily track its provenance when it is made available for re-use.
That includes 340 tonnes of steel – the equivalent weight of 45 of Auckland’s double-decker buses – supporting the Chief Post Office heritage building while the tunnels are built under it. Another example on C1 is the re-use of demolition framing timber for formwork, saving around $12,500 by eliminating the cost of buying and transporting new timber and paying for the disposal of the demo timber.
“The project has learnt much in terms of our commitment to waste minimisation,” Liz says.
“Success involves influencing people’s attitudes and behaviour to waste in our on-site project teams. Waste minimisation also needs a champion to keep driving that commitment.
“Once people are on board, there’s a lot of enthusiasm, particularly where they can see a cost or social benefit as well.
“Thinking early about potential waste can allow engineers to consider how they can design out waste, avoiding it in the first place. The waste hierarchy remains a good touch point: avoid, reduce, reuse, recycle.”
Liz acknowledges that in hindsight there were beneficial processes that could have been introduced earlier for the contracts now in construction.
“We didn’t have a formal design process to ensure the temporary works, which are quite significant for C1 and C2, could be safely and economically removed for re-use.
“So far, we have been able to remove a lot for reuse but, including it earlier in our design process for the upcoming C3 work, in the same way that safety in design is included, will mean it is thought about much sooner, which should increase the amount that is re-used.”
She adds that there are lessons from CRL that can be adopted elsewhere by local authorities and others.
“Setting targets early in the process and demonstrating commitment to them from the client by way of monitoring, KPIs and collaboration, is probably the most important aspect of our approach.”
As part of the City Rail Link’s stormwater realignment works at Mt Eden, Auckland – its C6 contract – two buildings were demolished – a residential complex of 18 apartments and a two-storey office block.
To help save resources and divert waste from landfill, City Rail Link and its contractors worked with the Helensville and Waitakere Community Recycling Centres to survey the two buildings to identify materials that could be salvaged and re-sold.
Hundreds of re-useable items were identified, ranging from hot water cylinders, fire doors, stoves and kitchen sinks.
Approximately five tonnes of salvaged items were removed and re-sold by the CRCs in their shops or online. Funds raised from the sales supported projects like the HiTech Studio, which runs a creative, technology-focused after-school programme for teenagers.
CRLL also worked with its C1 contractors to salvage and reuse items no longer required at the Britomart Station that would have traditionally been sent to landfill.
Items such as hand basins, taps, partitions, mirrors, urinals, hand-driers, hand-rails, shower fittings, cubicles, doors and wooden benches were removed from the old train crew facilities and re-sold through the Waitakere Transfer Station’s recycling shop to raise funds for the local community.