![The Great Western Highway between Katoomba and Blackheath. The Great Western Highway between Katoomba and Blackheath.](/images/transform/v1/crop/frm/7PapGKjYPrPEgYfvAPt3Wq/2096e3dc-71ea-42f7-8f96-5a2e875424b3.jpg/r0_376_4032_3028_w1200_h678_fmax.jpg)
DRILLING has been extended in the Blue Mountains as part of investigations into a future duplication of - and possible tunnel underneath - the Great Western Highway.
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Transport for NSW said earlier this year that drilling rigs and small excavators would be at work between Katoomba and Blackheath for geotechnical and utility investigations from mid-April through to June 30.
Though federal and state government funding has been deferred for the highway upgrade, Transport for NSW told the Advocate in April that the investigations would go ahead to "better inform future tenderers for the work to complete the Great Western Highway Upgrade Program".
"It will ensure that the designs for the remaining sections can be safely and efficiently constructed, comply with environmental safeguards and will provide the community with a resilient highway," a spokesperson said at the time.
"It is best value for money to complete these investigations now, so that contracts for the remaining work can be procured as soon as possible after the NSW Government and Australian Government release the funding for the work."
In an update this week, Transport for NSW told the Advocate that geotechnical investigations are continuing between Blackheath and Katoomba "to assess geology, contamination, and surface and groundwater movement".
"The results will help to further inform any potential future design or road work," a spokesperson said.
![An image from the environmental impact statement released last year for the proposed tunnel. An image from the environmental impact statement released last year for the proposed tunnel.](/images/transform/v1/crop/frm/7PapGKjYPrPEgYfvAPt3Wq/4afa62a1-6640-4d24-b3b9-5331e6920215.jpg/r0_10_589_341_w1200_h678_fmax.jpg)
"The Department of Planning and Environment also requested further investigations to inform any potential future design refinement of the proposed upgrade of the Great Western Highway between Blackheath and Little Hartley."
Between Blackheath and Little Hartley is where the previous NSW Government had planned to build twin 11-kilometre tunnels of two lanes both ways.
The tunnels - for which an environmental impact statement was released in January - are on hold after first the Albanese federal government and then the Minns state government deferred funding.
The Transport for NSW spokesperson said the current geotechnical investigations on the Great Western Highway will, weather permitting, be complete by mid-July.
![A previous "indicative visual concept" of the Blackheath portal for the twin tunnels to Little Hartley looking westbound. A previous "indicative visual concept" of the Blackheath portal for the twin tunnels to Little Hartley looking westbound.](/images/transform/v1/crop/frm/7PapGKjYPrPEgYfvAPt3Wq/290f3c82-8061-4a19-8125-957819fbc560.jpg/r0_14_631_369_w1200_h678_fmax.jpg)
Traffic changes
The work hours for the geotechnical investigations between Blackheath and Katoomba are between 7am and 6pm Monday to Friday.
Traffic changes will be in place for one investigation location in the layover bay towards the base of Victoria Pass.
Changes will include a reduced 40 kilometres an hour speed limit and temporary lane closures where necessary for the safety of motorists and workers.
Motorists are advised to drive to the conditions and follow the directions of signs and traffic control.