South Sister St. Marys, Tasmania

South Sister

rallings responds strongly ...

[the following letter was delivered to the Minister's office on 7 March, 2005; sender's address has been redacted]

March 7, 2005

Hon B Green
Minister for Infrastructure, Environment and Resources
10 Murray Street
Hobart, Tas. 7000

Dear Mr Green,

Subject: Logging Coupe NI114A, Slope Stability Issues

What should one do when one sees a gross folly committed in one's particular field of expertise, when the folly has the potential for unnecessary impacts on the:

I feel some obligation to try to prevent these unnecessary impacts. As a first step I decided that I should write to you in the hope that you will initiate an appropriate investigation before operations in this particular coupe are allowed to proceed.

I have a considerable experience in slope stability with over 40 years experience in geomechanics. I was member of the Australian Geomechanics Society's Working Group on Landslide Risk Assessment. I have received the fairly rare "Award of Merit" from the Tasmanian Division of the Institution of Engineers for my contribution to engineering knowledge.

The attached map, produced by MRT, shows the distribution of existing "active" and "potential" landslide areas in relation to the proposed coupe. It indicates that the landscape within the vicinity of the coupe is unusually unstable. The map also shows the extent of the mine workings that underlie the coupe.

The folly is Forestry's unwillingness to take seriously and to investigate the potential impact of the proposed logging operations on existing landsides, particularly those landslides that lie outside and below the coupe. While some consideration, though far from adequate, has been given to existing slides in the NE corner of the coupe, those landslides that lie below the coupe have been ignored.

The folly is attributable to a misconception about the activity of existing landslides. Forestry has argued that because the existing slides had probably originated under a more severe climate than that occurring today, these existing slides do not represent any serious threat today. This is quite contrary to reality. David Stapledon, who is recognized both nationally and internationally as an outstanding engineering geologist, showed in his report that the reactivation of slides arising from changes in ground water levels was quite common.

Usually the most effective means of stabilising an active landslide is to reduce ground water levels within the slide. The stabilising treatment would almost always include an attempt to eliminate water entering the slide zone from sources above the slide. On Forestry's own admission, the logging operation will initially increase ground water levels. This is something that should almost never be contemplated. Any rise in ground water levels resulting from logging operations will increase the probability of reactivation of existing slides. My initial impression is that the active zone just below the SE corner of the coupe, the old Jubilee Mine, and adjacent slopes would be very vulnerable to any increase in ground water levels.

The consequences of the reactivation of existing slides is not known at this stage, though it should be borne in mind that the cost of stabilising a large slide may be in the order of millions of dollars.

Mr Green, I am not saying and cannot say that the logging operations will definitely cause slope instability, because the matter has not been investigated. In a similar vein I cannot give any indication of the likely consequences and likely remedial cost of a major landside/s, but neither can Forestry. I am saying though, that there is an aligned set of factors that point to the probability of increased instability in the slopes below the coupe. I am also saying that the failure to properly investigate the slopes below the coupe is imprudent and borders on negligence.

The misconception referred to above indicates a lack of a basic understanding of the shear strength properties of soils and of the mechanics of landslides. However the person, whose understanding I had brought into question in my report, was the one who stood in judgment of my report. Furthermore, no one from Forestry or the Forest Practices Board has contacted me about my report. There has been no consultation whatsoever. My input, which was given in good faith, has been ignored.

From long experience with slope stability and landslides, I know that these matters require quite extensive and detailed investigation and analysis. In my report, the one dismissed by Forestry and the Forest Practices Board, I outlined the basic requirements of an appropriate investigation.

What I believe should happen is this;

Please give the above your urgent attention. I would be happy to discuss any of the above issues with you.

Yours Sincerely

Ralph Rallings, M.E., F.I.E.(Aust), CPEng.
CC: Dr F Daily, for you information

No response from Minister for days.

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