A recent, innovation on an unsealed road in Glenorchy LGA in Tasmania, challenged the more conventional “re-sheeting” approach with a result that saved Glenorchy Council both time and money yet delivered a quality sustainable outcome for its road users.
The Council’s traditional re-sheeting involved more than 100mm of fresh gravel placed on a road at substantial investment in capital cost. On unsealed roads, such as Fairy Glen Road in Glenorchy city’s rural suburb of Collinsvale, the council found this method not as successful due to a location often subject to heavy and prolonged rain conditions, surrounded by very dense forest vegetation.
The Fairy Glen road can be saturated for months, according to council staff, with water causing recurring potholes, corrugation, rutting and potentially more serious failures in the road base.
During a routine maintenance request the council’s maintain team tried a new approach to the project – and it worked.
This time around, according to council staff, a milling machine was used to precisely excavate the saturated failed areas of the wearing surface only, prior to “top dressing” with some fresh material.
Glenorchy council staff commonly use milling on sealed roads but it is unheard of for unsealed roads. The Glenorchy crew trialled this method, leaving the road base untouched and undamaged, working to the old adage ‘if it ain’t broke, don’t’ fix it’. A conventional re-sheet would have seen the base ripped up and disturbed regardless of it’s current condition at the time and expense of the ratepayer.
Next the team used fresh material to “top dress” the wearing course but only to a nominal depth of 35mm again saving almost two thirds of the stipulated 100mm gravel. Using less gravel in this instance meant less compounding problems caused by excessive material being introduced. Clogged drainage by excessive gravel will only lead to more potholes and, when gravel collects on a road shoulder, there is an increased potential for a landslip. All these outcomes were considered by the crew onsite and they hope the result will protect the longevity and safety of the site in the future.
Visit Glenorchy City Council’s website www.gcc.tas.gov.au
