The Challenge:

In April 2019 Kier was tasked with the installation of a 100m new water service connection in Newton Abbot to serve a new industrial unit.  The work required excavation, laying and reinstatement 110m of mains. This would mean the road would need closing for potentially up to two weeks. Care was required as other utilities were present at the site with medium pressure gas main, three 11kva electricity, BT fibre optic and overhead LV electricity. Added to this, trees were present alongside the majority of the route meaning tree roots must not be damaged by the work.

The original work duration was planned at ten days, using excavator and hand digging at all utility crossings as well as watching brief from Wales & West on the medium pressure gas main. Kier managers and supervisors reviewed the job and considered the risks involved to see if there was any way of shortening the excavation time.

The Solution:

Vacuum excavation was identified as the best method to reduce by at least half the time the dig team would be on site and would offer cost savings, health and safety benefits and reduced impact on road users. Wales and West were happy for us to proceed without the need for a watching brief providing the vac-ex truck was used.

Following a full survey/mark-up and consultation with the utility plans the route was cut using a road saw rather than a hand-held cut-off saw. This improved productivity, reduced hand arm vibration for operatives and provided a cleaner cut trench. The section of tar was then removed using the 1.5t mini-excavator in readiness for the 32t vac-ex truck to excavate a 750mm deep trench along the carriageway. The excavated material was then deposited at one end of the site for removal.

The Impact:

Using the vac-ex machine on this project produced numerous benefits.

On safety the high potential (danger to life) service strike, due to working around HV electricity and medium pressure gas main, was reduced. Exposure to hand arm vibration was reduced by approximately 50% using a wheeled road saw instead of hand operated cut-off saw, this also reduced the chance of manual handling injuries. Risk of injury through hand digging around other utilities were also reduced.

By using vac-ex we could follow NJUG4 guidelines for working close to trees. This all but removed the risk of root damage which could have led to prosecution and complaints. The road closure only in place for three days as opposed to two/three weeks - achieving our aim of reducing highway occupation. This had significant benefits to local residents, businesses and road users. In AMP7 we would expect to receive positive feedback under C-Mex and D-Mex measures given the speed and efficiency of the work.

" From a H&S, customer and stakeholder perspective I feel we must make use of vac ex more. This piece of work is very positive "
Neal Harris Developer Services Manager South West Water

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