Costco Coomera Car Park

How A Costco Car Park Became a Climate Asset

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BENEATH THE ASPHALT

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A Story of Partnership

On a summer afternoon in Queensland’s southeast growth corridor, the sun is relentless. The tarmac radiates heat like a stove top. But at the Costco Warehouse, Coomera, something unusual is happening underfoot.

Shoppers step out of their cars into the dappled shade of emerging tree canopies. Rainwater doesn’t flood but filters slowly into the ground. The car park, often the hottest, most lifeless part of a development, is pulling its weight. It’s not just a place to park - it’s a respite from the hot sun.

This is not an accident. It’s the result of bold design, early collaboration, and a hidden matrix of subterranean Stratavault that’s transforming how hardscape urban spaces can respond to extreme climate conditions.

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PROJECT DETAILS

LOCATION

47 Creek Rd, Coomera QLD Australia

COMPLETED

June 2023

CLIENT

Costco Wholesale (Gold Coast)

LANDSCAPE ARCHITECT

Group GSA Pty Ltd

PRINCIPAL ENGINEER

Mott MacDonald

PRINCIPAL CONTRACTOR

ADCO Constructions

CONSTRUCTION PARTNER

Citygreen PROJECTS

CITYGREEN PRODUCTS

Stratavault™, RootRain™ inlets and aeration

SCOPE

783 parking bays, 89+ large canopy trees, over 300 Stratavault modules

TREE SPECIES

Cupaniopsis anardioides (Tuckeroo), Elaceocarpus eumundi (Eumundi Quandong), Elaceocarpus reticulatus (Blueberry Ash), Melaleuca linarifolia (Snow-in-Summer), Tristaniopsis laurina (Water Gum), Waterhousea floribunda (Weeping Lilly Pilly), Delonix regia (Royal Poinciana)

Breaking Conventions for Better Outcomes

Retail car parks are, by design, challenging. Vast, paved, and engineered for efficiency, they leave little room for ecology. Add in Queensland’s subtropical extremes, summer temperatures soaring past 30°C, surface heat reaching 65°C, and unpredictable flash floods, and the stakes rise even further.
Yet when Costco and its project partners, Group GSA (landscape architecture) and ADCO
Constructions (build), and Citygreen PROJECTS set out to build the 14,346 m² warehouse store, on
a 53,661sqm site, with a 760-bay car park, they refused to fall back on conventional design. “From the outset, this wasn’t going to be just another sea of asphalt,” explains Catherine Atkinson, who leads Citygreen’s PROJECTS Division in Australia. “Costco wanted performance - shade, stormwater
function, long-term tree health - and they wanted it without sacrificing parking capacity.”

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A Climate-Responsive Car Park, Engineered Below the Surface

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To meet those goals, the team turned to Citygreen’s Stratavault™, an engineered deep soil zone system designed to support vehicle loads while providing optimal soil environments for trees.

Stratavault can withstand loads of up to 8t/16,000 lb per wheel (HS20/W80 compliance), which enables the system to support roads, drive lanes, and car parks.

The Stratavault matrix retains over 93% open vault space for soil volume, allowing tree roots to grow freely without compacting the ground or disturbing pavements.

The design solution specified more than 300 Stratavault modules to be installed beneath shared bays, kerb islands, and perimeter rows, without sacrificing a single parking
space.

Each of the trees were planted into a 30m³ vault of uncompacted,

sandy loam soil, wrapped in geotextile, and fitted with RootRain™ inlets to deliver passive irrigation and long-term aeration. These systems capture rainfall and overland flow, directing water deep into the soil where it’s absorbed or filtered before reaching the stormwater system.

“It’s a complete system,” Atkinson explains. “It supports healthy tree growth, handles runoff, and protects pavements. You install it once and let nature take over.”

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A Complex Build - Delivered with Precision

The Costco car park site presented a number of construction challenges that meant the Stratavault
modules had to be installed alongside major civil works, under tight deadlines and in coordination with multiple trades.
Yet the project ran to schedule and won praise for its execution.
“This has been a fantastic project, especially given the challenges in today’s construction market,” says Brenton Sonnego, Project Manager at ADCO.
“Citygreen were engaged early and brought both international expertise and local engineering knowledge to shape whole-of-life outcomes. We look forward to working with them again”.

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ADCO’s site team were unfamiliar with Stratavault and working with the Citygreen PROJECTS team prior to this build.

“We’d never used Stratavault before,” recalls Site Manager Michael Burn. “But from the first meeting, we were sold on the team’s attitude and attention to detail. Honestly, if every trade on site worked like the Citygreen PROJECTS team, the job would’ve flowed like a dream”.

Growing Shade, Slowing Storms

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While the system itself is invisible now to shoppers, buried beneath asphalt and mulch, its effects are emerging quickly.

The tree species were selected for resilience and canopy spread, and include Tuckeroo, Water Gum, Blueberry Ash, and Royal Poinciana. Featured photos were taken just 12 months after planting, but in just a few years, they’ll begin delivering to targets:

• Shade over 25% of all parking bays
• Surface temperature reductions up to 20°C under canopy
• Detention of ~25,000 litres of runoff per storm event
• Natural filtration of hydrocarbons, metals, and silt
• No root heave or pavement uplift

These benefits will come without mechanical irrigation. Thanks to passive systems and smart soil engineering, the trees have everything they need to thrive with minimal intervention.
“It was a complex job with lots of trades on site,” says Grant Radbourne, who led the Stratavault installation for Citygreen. “But we delivered it on budget, ahead of schedule, and exceeded every safety and quality metric. Now we get to watch it flourish!”

The Costco car park, Coomera case study doesn’t just prove that climate-cool car parks are possible, it sets a precedent. As cities push for heat resilience and water sensitive urban design, this case study
demonstrates that using Stratavault as a stormwater system for passive tree irrigation, developers can future proof landscapes without sacrificing commercial outcomes.

“We’ve turned one of the most hostile surfaces in urban design into a low carbon asset,” says Atkinson. “And we did it without slowing down delivery.”

For developers, designers, and planners, the takeaway is clear: when you treat the car park like part of the landscape, not an afterthought, you unlock new potential.

Green infrastructure works best when it’s planned early and Citygreen’s early involvement helped align technical design with real-world construction.

Sustainability adds value, improves environmental comfort, reduces energy load, and protects long term maintenance budgets.

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“Great customer service, quick response times and a very in depth QA system with constant support.”

- Laura Wiesenekker, Project Engineer, Densford Civil -

“Citygreen is a very professional  business, and I found everything was great in terms of deliveries, product supply and information. It was all forthcoming and helped us to complete the project.”

- Keith Burns, Architect/Designer, Keith Burns Architect -

“Citygreen offered training and invaluable technical assistance during the works.”

- James Callan, Estimating Manager, Complex Co Pty Ltd -

“Our experience, in working with a Citygreen Design Studio was second to none. We found responses from the design studio to be very timely, and technically thorough. We went backwards and forwards a number of times, looking at different iterations of the design and, nothing was too much trouble to examine and explore different possibilities. I would highly recommend the Citygreen Design Studio to any future client considering using your services.”

- Sandra Smith, Principal Landscape Architect, City Of Monash -

“We are big on compliance on all projects, and the fact that their SmartCertify cloud platform covers all bases, and supports their 20 year warranties, is critical – especially that these pits are being installed under roadways and footpaths.”

- Johny Purkaystha, Civil Program Engineer, Central Coast Council -

"I reviewed all the previous projects that we have installed in the past couple years using your product and I can happily report back that we have 0% mortality in the soil cells, which is incredible!"

- Brendan Wilton, CEO, Trim Landscaping, Bedford, Canada -