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Mapping utilities in Honolulu

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Mapping utilities in Honolulu included using GPR.

Mapping utilities in Honolulu

The Honolulu Seawater Air Conditioning Project is part of an ongoing effort to bring environmentally friendly air conditioning services to downtown Honolulu.

Paul Vierling of Hawaii Geophysical Services talks about the use of ground penetrating radar and potholing in mapping utilities potentially impacted by the project.

The project commenced in 2011 when the Kiewit-Mortenson JV was awarded a construction contract. So far the project has utilised microtunnelling to install deep sea intakes that will pump cold seawater to a cooling station on the Kakaako shoreline. From this point, the seawater will pass through a heat exchanger, transferring the cool temperature to freshwater that will be circulated through a closed loop pipeline system.

The cool freshwater will then be transported to a network of buildings in downtown Honolulu, providing an air conditioning service that reduces the city’s reliance of fossil fuel energy generation. Fossil fuels have typically been used for powering chillers, condenser pumps and cooling towers.

With a total project value of US$250 million, the long-planned project is scheduled for completion and commissioning in 2017.

Hawaii Geophysical Services (HGS) – a small business providing ground penetrating radar (GPR), utility location and mapping, air excavation and radio frequency contracting services for a range of projects in Hawaii – has played a significant role in the delivery of project work so far.

The contractor was commissioned by project leader Hawaii Seawater Air Conditioning to pothole and locate an estimated total of 40 utilities that could potentially be impacted by the installation of the district cooling network. Working in downtown Honolulu, HGS used a combination of GPR, air excavation and potholing to collate and deliver vital utility information, enabling project works to move forward.

Under the contract HGS recorded the depth of identified utilities, the size and material of pipes, and the distance from fixed survey markers. The contractor also delivered marked-up maps of the identified underground infrastructure, and images and photos of any pothole sidewalls that could provide supporting information on a
utility’s location.

While the utility location work was relatively straightforward, the project was not without its challenges. Mr Vierling says “During our survey we did encounter items buried under the surface of the roadway that we did not expect to find, including light pole bases and animal bones. We were also working in busy traffic conditions downtown, which posed many challenges, including traffic congestion and safety risks.”

HGS’ portion of the project work had an estimated value of US$160,000.

Trenchless benefits everyone

HGS has been using trenchless methods since 2006, and finds potholing technology to be particularly useful in the work it completes.

Mr Vierling says “Potholing provides a cost-saving alternative to common excavation and repair methods, which often require large ‘open’ holes, followed by the removal and disposal of unwanted pavements and soils.

“These conventional practices – which involve several large pieces of equipment such as backhoes, dump trucks and pavement breakers – can sometimes account for
80 per cent of the total cost of a job.”

However, reduced costs is not the only incentive driving Mr Vierling and HGS towards trenchless. The company sees several other benefits of no-dig methods, including:

  • Reduced traffic disruption: Faster one-step permanent pavement repairs mean reduced traffic disruptions with fewer and shorter road closings with no repeat visits. With this method roads can be open for traffic just 30 minutes after the repair.
  • Reduced project footprints: A neat, almost invisible, 18-inch diameter keyhole core – compared to a conventional rectangular road cut, this means reduced ‘scarring’ of the community landscape.
  • Reduced environmental impacts: Using trenchless means that there is no road-cut spoil to be disposed of and no temporary patching compounds with volatile organic compounds that can escape into the atmosphere.
  • Cleaner, safer, and less intrusive worksites: No-dig means no jackhammers or large excavation equipment, less mess during and after the excavation, and reduced disruption for nearby residents and businesses.

From Mr Vierling’s perspective, using Trenchless Technology is no different to selecting keyhole surgery over less invasive methods. He comments “When it comes to making holes, smaller is better. Surgeons have recognised this fact for years – keyhole surgery is less intrusive and causes less trauma and tissue damage to the patient, which contributes to a shorter recovery period. The same holds true for cutting holes in roads to access, repair of view buried infrastructure.”

With this thought in mind, Mr Vierling remains a strong proponent of no-dig techniques.

“Keyhole methods can cut excavation, repair and restoration costs in half,” he explains. “With keyhole techniques maintenance activities are conducted through small pavement openings, resulting in significant cost savings, reduced public inconvenience, and more efficient repairs.”

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