Planning is Progress: A World First in Project Preparation

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Let’s Get Wellington Moving is a multi-decade, transformational programme of work and, as with any large-scale, city-altering programme, the process is more complex than many of us might imagine.

There are initial designs and options, public engagements, feedback, adjustments, more feedback, and finalisation of the design, before construction even begins. A lot of this happens behind the scenes, long before any road cone hits the road. But planning is progress, and all part of the process. 

Comprehensive planning reduces risk while saving time and money. It is the bedrock upon which major change is built. And speaking of bedrock, somewhere between the bedrock and the surface is the subsurface – home to all manner of pipes and cables, from water and electric to gas and communications. 

Since 2019, Let’s Get Wellington Moving has partnered with Reveal, a Wellington-founded and headquartered company, to use world-leading technology in its underground utility surveying, with the company completing key scans for both the Golden Mile and mass rapid transit (MRT) projects across four stages. The surveys have resulted in the most comprehensive underground utility model in the world (by a large margin), and an invaluable single source of truth for Wellington’s underground utilities. 

CAPTION: A underground utilities scan showing the spaghetti network of underground utilities, where red (wastewater), blue (potable water), green (stormwater), orange (gas), yellow (electricity), purple (communications), and pink (unknown) intersect and serve the city centre.

“We’re thrilled to be able to use this local, cutting-edge technology to help us understand what’s beneath our roads before excavation and construction, which will be incredibly important in designing projects in our city” says LGWM Programme Director Sarah Gardner.

“Historically, civil infrastructure projects have had challenges with relying on built plans that can be out of date and less than accurate, which can result in unexpected encounters with buried underground utilities, including critical assets like gas mains or high-voltage electricity lines.”

Using ground-penetrating radar, the scans send a radar wave down and, when it hits something solid, a reflection is sent back. How long it takes for the signal to return gives a rough idea of the utility’s depth, while the breadth of the signal tells us how wide the utility is.

CAPTION: Lambton Quay and side streets detections

Accidental utilities strikes can be very costly. Figures from Reveal – based on a mix of New Zealand and overseas data – show that each strike costs between $4,000 and $11,000 in direct costs (replacement costs, callout of health and safety, etc.) and between $11,000 and $110,000 in indirect costs (project delays, unforeseen disruption to communities, etc.). All told, utility strikes cost the New Zealand economy an estimated $2.5 billion every year.

The practical value of a single source of truth for underground utilities should not be underestimated. Previously, the records for each asset – electricity, gas, water, or communications – lay with the asset owner. This meant that each set of records existed in isolation and required a great deal of coordination to gather and analyse. Even then, these records would usually be in 2D, and would not show width and depth, giving, at best, an inconclusive view. But with this 3D underground utilities model, the city will gain a new level of understanding of its underground services, which can then be used by any number of planners.

“"Having a complete picture of what lies beneath the city helps avoid costly damage and disruption of utilities,” says Greater Wellington Transport Chair Thomas Nash. “It will minimise disruption to pedestrians and road users, as well as assist our city planners, designers, and engineers to plan and design more efficiently. The vast majority of the work LGWM is doing is not immediately visible and this is totally normal for major infrastructure projects of this scale and size. It’s exciting to be able to get a snapshot of some of this behind-the-scenes underground work being done with a world leading innovative Wellington business."

Pinpointing the location of underground utilities is the main objective but, at times, the scans “unearth” some interesting finds. While scanning sections of Courtenay Place, for example, the scans showed the tram lines for the old tram buried beneath the road’s surface. Technically unowned as the tracks are not assets, there were no existing records of the lines. Without scanning, this could have been a costly discovery further down the line as the construction company broke ground only to find unknown assets in their path, complicating their works and causing delays.

Other finds can include voids, where the earth under the ground has eroded away and is not solid enough to return a radar reflection. If these voids are left unmanaged, they can lead to potholes or sinkholes, creating a potential safety risk for workers during construction.

As Let’s Get Wellington Moving shifts into delivery mode, it is the work done ahead of spades hitting the ground that will help mitigate cost increases and delays once construction begins. Not only will these underground surveys play a key role in our own project delivery, they will also be an important resource for Wellington that can be used for proactive project planning for years to come.  

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