Page 72 - Week 01 - Tuesday, 13 December 2016
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By way of background, the Blue Range section of the lower Cotter catchment carries a large concentration of self-sown pine trees, or wildlings, growing in steep terrain. Due to the difficulty and expense associated with removing these pines, no work has been undertaken to manage this substantial fuel load since the 2003 fires. The Auditor-General noted the need for a plan to manage the Blue Range pines if the fire risk to the lower Cotter catchment was to be adequately mitigated.
After the appropriation of funding by this government in 2015-16, the land manager determined that a trial of removal methods would equip it with valuable information on the relative suitability and cost-effectiveness of possible methods available to remove pines from the Blue Range area.
I can report to the Assembly that the following key milestones have been met by the land manager: an area of 106 hectares of pine wildlings just outside the lower Cotter catchment, but similar in slope and concentration of pine wildlings to that inside the catchment was selected as the trial site in February this year.
A water quality monitoring framework was developed and applied to ensure that the trial removal works could be monitored for their effects on water quality run-off from the work site. This framework was developed with the assistance of Icon Water and completed in February 2016 with monitoring equipment installed on the site in March 2016.
Work commenced on trialling three methods of mechanical removal of pine wildings in May 2016 and was completed in August this year. An evaluation of methods and costs was completed in October this year, yielding two methods as the most suitable means to remove the pine wildings. All planning and approvals for works to commence within the lower Cotter catchment in 2016-17 will be completed by this month.
The pine wilding removal trials are now substantially complete and they have identified that two main methods will be able to be practically applied whilst providing value for money and minimising water quality impacts. Operating on steeper slopes presents challenges to the land manager as machinery stability during operation is the utmost concern. A “trittering machine”, which can be described as an adapted excavator with a mulching attachment, operates by pulping the standing pines into chips, creating a bed of readily compostable material in situ. It is particularly effective and safer to operate on steeper slopes.
The resulting mulched material produced by this machine delivers the added benefit of presenting a shield to rainfall on the ground, thus allowing the gradual seepage of moisture through to the soil layer and minimising the chance of damaging erosion. On gentler slopes, a bulldozer will push over the pines into windrows arranged along the contours for later burning when conditions will allow.
It should be noted that during the four months of the trial over 100 millimetres of rainfall was received by the trial area, and monitoring equipment recorded a negligible increase in the turbidity of run-off into the tributaries feeding the Cotter Dam. More
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