1 INTRODUCTION
The limestone deposits to the west of Mt Larcom, in Central Queensland, were designated to replace the dwindling stocks of fossil corals in Moreton Bay, for decades dredged by Queensland Cement Lime Co Ltd to supply the State’s cement requirements. To avoid potential visual pollution associated with normal quarrying operations at the central Queensland site(s), a below-ground operation, or open cut, was proposed. Four major leases were involved, covering the East End and Bracewell districts, which were basically dairy farming communities. It was planned that purchase of farms would be confined, initially, to those properties directly covered by the proposed East End open pit mine and its infrastructure. As expansion followed, or as leases in Bracewell were programmed for development, additional farms would then be purchased.
A Mining Court hearing was held in Gladstone in 1974 to discuss, among other matters, the environmental aspects of the project. The writer was invited to appear on behalf of representatives of the farming community, known then as the Mt Larcom
District Mining Protest Group. A report by the writer (1) presented to the Warden’s Court was designed to bring several aspects of the program into focus:-
• In both East End and Bracewell, virtually all permanent water for stock and other farming needs came from wells and bores. High yields were typical in the limestone and, extrapolating from these, a pumping rate between 25 and 50 litres per second was estimated by the writer to be available to achieve dewatering of the proposed open pit. (According to early figures by C.R. Dudgeon, recorded rates averaged 35 litres per second although a figure of 60 litres per second was mentioned in 1980 by the then Minister for Lands, Forestry and Water Resources.) Rates of this predicted order, operating twenty four hours a day, raised concerns not only with regard to the potential magnitude of aquifer depletion but also with regard to the lateral extent of depletion in any affected aquifer. It was predicted in the writer’s above mentioned report that the direct effects in East End would almost certainly be felt as far north as Machine Creek – a distance of some 5km from the mine - while there was also the possibility of some roll-on effects for the surface flows in this creek.
• In view of these predictions, it appeared reasonable to expect that farms located outside the mine’s immediate requirements could be adversely affected over time. If so, such properties would be unlikely to hold their values and, indeed, some might well become non-viable as primary producing units. On this basis, it was conceivable that, when the time came for the mine to purchase such farms, property owners could be financially penalised through no fault of their own. Some safeguards therefore needed to be put in place to cover for this eventuality.
What resulted from the Mining Warden’s Court was:
• A large area covering the four leases, and beyond, was designated for groundwater monitoring, most of the area being shown on Map 1. The numbers of monitoring points in the area rendered the mine probably one of the best groundwater monitoring exercises in the world at that time.
• A guarantee that any utilised wells/bores, which failed through a mine-induced drop in the groundwater table, would be restored by the mine.
2 GEOLOGY
At the time of the Warden’s court, the geology of the region had been described in reports for the project by Oceanics Australia and by T.J. Madden & Assocs. Several distinct bodies of Devonian limestone had been identified, separated by lenticular masses of volcaniclastic rocks, all trending N.N.W. At the time, it was thought that this trend represented the strike of beds with a sub-vertical dip. However, it later appeared more likely (to the writer) that the lenticular blocks were the result of regional shearing along lithological boundaries and also within the lenticular blocks themselves. In limestones, such shear zones tend to become the focus of seepage and transformation into solution channels with, eventually, the development of karst situations.
In both the East End and Bracewell areas, sink holes were recorded in outcrops of limestone, indicating a well-developed karst nature. This was further confirmed by exploratory drilling, where both voids and pockets of clay were encountered in limestone, at depth, these features being indicative of the presence of infilled caverns/drainage channels.
Early information and air photo studies also suggested that the East End limestone, incorporating East End Lease #1, was probably continuous with the limestone body to the north of Machine Creek. In the Bracewell area, there appeared to be hydraulic connections between the upper Bracewell and lower Bracewell leases. However, a line of volcaniclastic hills separated the limestone of lower Bracewell from that at East End.
The aforementioned geological reports mooted that these two main limestone masses lay on the opposite limbs of an anticline. Later surveys by the Geological Survey suggested the two limestone masses might be of different ages. In either case, there was unlikely to be any connection between them at depth. There was, however, a superficial connection of unknown adequacy in the alluvial deposits along Machine Creek where the creek breached the line of volcaniclastic hills separating Bracewell from East End.
A third limestone body was present in the Jacobs Creek catchment to the south of
Bracewell and to the west of East End. This, again, was separated from the East End limestone by volcaniclastic topography, without any alluvial breach - although there was an unknown extent of limestone along Scrub Creek, to the south of the mine, into which Jacobs Creek discharged.
The general geology is shown on Map 2, based on the original geological reports above, a more recent geological map produced by Groundwork, and the writer’s own
1997 field work and air photo interpretations (8) which gave similar interpretations to the most recent survey. Reliable clues as to the location of buried aquifers were also available from geomorphological expressions and, more particularly, from the groundwater responses to mining.
Superficial deposits in the project area include Machine Creek alluvium covering the
Bracewell limestone and thick “terra rosa” deposits covering the limestone in the vicinity of the East End Mine. In the latter environment, the emergence of springs pointed to artesian conditions existing in the underlying limestone, prior to mining.
3 HISTORICAL
The water monitoring program, which stemmed from the 1974 Warden’s Court, was directed by Dr (later Professor) C.R. Dudgeon of the University of NSW, Water Research Laboratory. Existing water supply bores and wells of the region were utilised in the program and these were enhanced by further installations over the following years, particularly to the north of Machine Creek in the East End aquifer. A number of deep observation bores, #01 – #09, were also drilled into the limestone bodies of East End and Bracewell, prior to the onset of mining activities. Some of the monitoring stations, those mentioned in the text, are shown on Maps 2, 3 and 4, and their relevance will be referred to during the following discussions. Unfortunately, observation bore #01 (near the East End mine) was lost quite early in the development of the open pit and #02 somewhat later during the life of the project.
Reading of all monitoring stations was undertaken by officers of the relevant Government Department, on a three monthly basis (NB. The relevant Government Department responsible for environmental matters of this type changed its name and structure so frequently since the 1990s, that it is simpler to refer to it as “the relevant Department”). Maps of groundwater contours were initially produced for each set of readings and were made available to the Mt Larcom Mining Protest Group and, later, to the Citizen’s Liaison Group (CLG), which consisted of landholders and mine representatives. However, no interpretation of the contours appears to have been undertaken and, after a number of years, the contour map distribution ceased by mutual agreements. The important point here is that the original lease conditions made no provisions regarding responsibility for ongoing interpretation of data: either by the mine, or by the relevant Government Department, or by the monitoring program’s director.
Dr Dudgeon did, however, produce a report in March 1980 on the first three years of the program (2). This covered pre-mining conditions and approximately nine months of monitoring after a sudden drop in groundwater occurred in a large number of monitoring stations, in May 1979 (NB. The onset of excavations/groundwater lowering at the mine can be confidently judged by this sudden fall in water levels of around 3m, occurring simultaneously throughout the East End limestone and, indeed, throughout most of the Bracewell limestone areas).
Although, as just mentioned, the Dudgeon report was not required to provide any indepth analyses, it did include passing comments, as follows:-
• ... no attempt has been made to make a quantitative interpretation of the results (as) the cost involved is not warranted unless specific problems arise...
• ... no major aquifers have been located...
• ...changes in the groundwater levels support the opinion given before monitoring commenced that the effect of pumping from quarries (sic) will have a significant and rapid effect within the limestone bodies but that the effect will not spread far beyond the limestone... except where it feeds a confined aquifer...
It is easy to judge how the combination of the second and third dot points allowed both the mine and the relevant Government Department(s) to push ahead without serious environmental concerns. Later, Dr Dudgeon wrote a conference paper espousing similar conclusions (3): namely that there were no sensible effects of mine pumping outside a small cone of depression that extended no more than 0.5 km from the mine. Within the cone, Dr Dudgeon stated that water levels had dropped by a modest 2-3m, maximum. This same view was reiterated in a 1995 report (4). The view, however, was wildly in error as will be demonstrated; both the East End and the Bracewell aquifers were much more severely affected and to far greater distance from the mine. Indeed, as regards dot point 2 above, the aquifers could be clearly identified by the groundwater depletions even at the outset of operations at East End, as can be inferred from Map 3, discussed later.
Giving such lip service to what was expected in the limestone aquifers, rather than initiating some rigorous analyses, the Dudgeon reports were probably the main reasons for the lack of alarms raised about groundwater depletions until as late as 1995. This date incidentally coincided with a time of extended dry periods in southern Queensland and thus further complications were introduced into the debate, as will also be discussed.
By 1995, the affected communities were becoming increasingly aware of the serious nature of groundwater depletions. CLG meetings were called to try to reach some rational conclusions on the matter. The present writer was invited to attend one of these and the visit included a brief drive over parts of the monitoring area and the provision of a selection of hydrographs from the monitoring program.
Stemming from this initial and brief meeting, the present writer mistakenly accepted two parameters espoused by Dr Dudgeon. The first was that some 8m of the drop in aquifer levels was associated with developing drought conditions. Although this sort of dramatic climatic response is atypical of a confined aquifer, two items were taken as support for the proposition. Firstly, a well in the East End aquifer, W53, had been deepened by some 8m beyond the 1978 water table at the location. Wells cannot easily be excavated below the water table, so it was inferred that the additional 8m of deepening would have been carried out as the original water table was lowered, by drought (NB. An alternative explanation for this well deepening, related to mine pumping depletion, was given later by EEMAG representative, Mr Alec Lucke). Secondly, by 1995, the water table in the Bracewell aquifer had been lowered by the same amount, 8m. Since the Bracewell aquifer was then seen to be separated from the East End aquifer, the 8m depletion through drought effects was taken to be supported by two independent sources of information.
Even mistakenly accepting this view, there still arose a conflict with the Dudgeon interpretations of 1995. As mentioned, the Dudgeon proposal adhered to the belief that only 2m, or perhaps 3m, of depletion in the East End aquifer was mine-induced.
In fact, the monitoring clearly showed depletions of the order of 13m in the East End aquifer, extending north to Machine Creek. That is, even allowing for the alleged 8m of drought effects, there was still left some 5m of the depletion which could only be mine-induced. For some reason, there was an overt unwillingness by Dr Dudgeon and the Departmental officers at the meeting to accept the latter figure.
As a result of this initial conflict, the groundwater section of the Geological Survey decided that a computer model should be undertaken – although, in fact, the monitoring was quite amenable to analysis by hand methods. The computer modeling was carried out by Dr Franz Kalf, of Kalf & Associates, Sydney, (5) and (6). The model, after a second trial run, was in substantial agreement with the manual analysis of the East End aquifer: 13m depletion, perhaps including a small drought component. However, the modelling still claimed that the 8m depletion in the Bracewell aquifer was a drought phenomenon.
At this point the writer was again called on by the CLG to review the situation. On this second occasion, all monitoring hydrographs and maps were made available and the writer was able to spend a week on site coming to terms with both the geography and geology of the region, and with locations of the monitoring stations. An analysis of hydrographs allowed the production of groundwater contours, taking cognizance of geological boundaries where possible. The resulting reports, (8) and (9), agreed in general with the computer model of the East End aquifer but questioned some of the basic Kalf conclusions with regard to Bracewell. This was allegedly labelled as unprofessional conduct, but the report was welcomed by the farming community which felt that the interpretations were in accordance with their own long term experience in the area (NB. By this time, the community had formed the East End Mine Action Group, EEMAG, which is still extant as these words are written).
Accordance between the writer’s report and the computer model, for the east End aquifer, is illustrated by Figure 2. Both the writer’s manual interpretation and the computer model produced similar groundwater sections, as shown – at least to the north of the mine. Obvious from the first two decades of mine pumping are two phenomena: a reduction in water table levels and a northern shift of the water divide. (There was also a partial recharge in the 1990-91 wet season, as indicated.)
Under pre-mining conditions, then, the water divide was linked closely to the lower reaches of Machine Creek. Incidentally, even in pre-mining times, this creek disappeared into the eastern side of the East End aquifer and seepages from the water divide migrated both to the south (to the mine area) and also to the north, feeding the Hut Creek catchment. After rain, these seepages emerged at the ground surface in the vicinity of the proposed mine, and on the northerly slopes beyond the Mt Larcom- Bracewell Road, in the Hut Creek catchment.
Over the first two decades of mine pumping the water divide shifted north beyond the Mt Larcom-Bracewell Road, while also losing something like 15m in elevation. The effect of this was, firstly, to dry out the above mentioned springs and, secondly, to reduce severely the quantities of seepage into the Hut Creek catchment. Hut Creek dried out in the 1990s, partly as a result of this.
The effects of mine pumping were also felt to the south of the mine, as shown in
Figure 2, despite the discharge of mine water to Larcom Creek. The depletion in the south gradually progressed west, up Scrub Creek towards Cedar Vale. By the 1990s, the lower reaches of the Jacobs Creek aquifer also began to drain into the depleted aquifer along Scrub Creek, as discussed in the writer’s 1997 report (8).
On the other side of the coin were the main criticisms of computer model as presented in the Kalf report. The criticisms focussed on the Bracewell aquifer and on the alleged responses to drought. The “drought” view was severely criticised for several reasons:
• The calibrations used in the computer model for the Bracewell aquifer were unrepresentative of the aquifer. One calibration bore was located in the adjacent (Jacobs Creek) catchment, while the two calibration wells chosen in the flat valley environment of lower Bracewell, W28 and W43, were shallow wells in alluvium. What made the choice of these stations more puzzling was the fact that the deep monitoring bores in the Bracewell aquifer, #04 and #05, were quite near but were not utilised. Hydrographs for the two wells and for the two deep monitoring bores are given in Figure 1, to illustrate the different responses between the alluvium and the aquifer during the 1980s.
Shallow alluvial wells are obviously more responsive to seasonal climate variations than a massive confined aquifer, protected from the effects of evaporation. However, water levels in the wells stood close to the ground surface throughout the 1980s, apart from a few minor variations no doubt synchronised with short dry spells and/or possibly exacerbated by usage. By contrast, the water levels in the limestone aquifer, as revealed by the deep monitoring bores, bear no such relationship to the seasonal variations of the alluvial wells. In other words, the patterns of large depletions in the Bracewell aquifer occur without any nexus with seasonal changes, during the 1980s.
• The effects of these unrepresentative calibration stations, W28 and W43, become even more obvious when one compares the hydrographs of the Bracewell observation bores, #04 and #05, with the hydrographs of observation bores #02 and #03 in the East End aquifer. This comparison is also available on Figure 1. Bores #02 and #03 were located in the East End aquifer close to the open pit mine, so they could be expected to reflect the quasi-immediate reactions of the East End aquifer to mine dewatering. The unambiguous parallelism with the East End hydrographs, displayed by the Bracewell aquifer monitoring bores, demonstrates the existence of some direct hydraulic connection between the two major aquifers as well as dispensing with any climatic variation connections.
The only difference between the two aquifers is, of course, that the hydrographic parallelism stops when depletion reaches 8m in the Bracewell aquifer, while in the downstream East End aquifer the water table lowering continues to almost twice this amount. By the late 1990s the East End aquifer stood at an elevation some 25 – 30m lower than the Bracewell aquifer. The explanation for this is given below.
• It was pointed out both to the author of the computer model report and to the relevant Government Department - on more than one occasion - that the use of the unrepresentative calibrations provided by W28 and W43 could not be expected to lead to any realistic conclusions on the Bracewell aquifer behaviour. However, the Bracewell model was not re-run to correct the errors. Refusal to enter into discussions on certain topics was to become a repeated reaction of the relevant Government Department and its consultants.
• Finally, the explanation for the elevation differential between the two aquifers was clearly illustrated in a presentation by the hydrogeology section of the Geological Survey, at a formal meeting at Mt Larcom in 1998 (10). Figure 3, herein, has been taken from the GSQ presentation, and shows the existence of a subsurface barrier of volcaniclastic rocks in the vicinity of Weir 2. This subsurface barrier has since been proven by seismic traverses, deep test pits, and drilling.
It is worth pointing out at this stage that the Machine Creek alluvial zone, connecting Bracewell and East End, rests on top of the barrier and the capability of this alluvial veneer, to act as a hydraulic connector between the two major aquifers, is treated in more detail in Section 4.3, based on the above further investigations. Sufficient to state at this point is that each and every facet of these investigations has been subject to quite extended – and sometimes farcical - controversy between the writer and the relevant Government Department(s). But there are a couple of independent pieces of evidence also pointing to the alluvial zone as the outlet for the Bracewell aquifer.
Firstly, the groundwater contours in the Bracewell aquifer, prior to the commencement of mining activities in 1977, are shown in Map 4. A distinct downstream migration of water within the aquifer is revealed with the discharge point somewhere near the entrance to the broad alluvial deposit; that is, in the vicinity of Weir 2. Secondly, the same seepage orientation is obvious in the groundwater contours of 1988, when the Bracewell aquifer was showing marked signs of quite serious depletion. This will be illustrated to better effect when discussing Figure 4, in Section 4.3.
*
As a final gesture towards resolution, the relevant Government Department(s) nominated a senior officer to produce an in-house report in the new century. This was intended to summarise the project as a whole, as a basis for discussion. A Draft Final Report (DFR) resulted, with Version 1 presented in May 2006 (16). The first paragraph of the Executive Summary of this version ends with: “... the investigation (sic) has been designed to be able to provide an informed background and understanding of the geology, hydrology and hydrogeology of the East End and Bracewell area with a view to be able to assess the options for dispute resolution and agree on a method to move forward with constructive and unilaterally agreeable set of actions.”
This is followed in the second paragraph of the Executive Summary by: “The fact is that the East End Mine, various consultants and the Department have unanimously held that (based on available information) the Bracewell aquifer is not affected by mine dewatering.”
This blatantly unequivocal statement at the beginning of a Draft Final Report, designed as a basis for discussion, should be assessed in the light of the some of the evidence already given above. It should be kept in mind during further discussions of the behaviour on the Bracewell aquifer, given below.
At the conclusion of the DFR’s Executive Summary, the statement is made that the Department has acknowledged and reviewed all of the previous investigations that have been completed at, and adjacent to, the east End Mine, by all parties to the dispute. In fact, the original Dudgeon report of 1980 (2) was not referenced, while the response to it submitted by this writer in 2005 (15), was only added in a later version and listed as unpublished. A number of other reports by the present writer, dealing with fundamental matters were also omitted. The seismic survey likewise was not originally referenced and, most surprising of all, nor was the extensive study of the project carried out for EEMAG by the Australian National University team. This included a dye tracing experiment and an expert analysis of the cessation of surface flows in Machine Creek (12). Some of these references have since been included in the Final Draft Report, while some of the original references have been deleted.
In the event, several meetings between EEMAG, its consultants, departmental officers (including the report’s author), and mine representatives, were held over the following couple of years without any sensible changes being made to the conclusions drawn in Version 1. Discussion of the conflicts follows in Section 4.
This, briefly, is the geohydrological history of the project. Below, the major conflicts that have arisen in the decade since 1995 are outlined and analysed.
4 MAJOR CONFLICTS
At the outset, it can be stated that the depletion recorded in the East End aquifer have now generally been accepted by all parties as a mine-induced phenomenon. There remain matters dealing with the effects on surface streams, the degrees of mine-induced aquifer depletion and, in many cases, the compensation to be determined on the basis of the conditions alluded to in the original lease conditions.
The major technical conflicts are largely related to the Bracewell and other adjacent aquifers within the project area. The conflicts are discussed under the following headings, allowing that there is sometimes an overlapping of physical problems:-
• The early Dudgeon Report and aquifer definition
• The relative effects of drought on groundwater depletion
• The Bracewell-East End connection
• Surface flows in Machine Creek
• Evapouration from the open pit and long term prospects
• Other environmental violations
4.1 The Early Dudgeon Report and Aquifer Definition
The exact date of commencement of pit excavations and dewatering for the proposed mine is, in itself, a subject of controversy. According to a letter from the Minister for Lands, Forestry and Water Resources (To Mrs H. Lucke, dated May 1980) dewatering began in November 1979. However, it is known that the mine was sited in a locality subject to artesian seepages and hence it is reasonable to anticipate that before any excavations beyond superficial depths could be attempted, some groundwater lowering would have been required, a typical method being to pump from sumps. The relevant hydrograph patterns of the first Dudgeon report (2), as already discussed, would appear to provide fairly conclusive indications that dewatering of some kind had begun just before the middle of 1979.
The pre-mining monitoring, begun in 1977, provides baseline information on the pristine aquifers. The first Dudgeon Report (2) covers this pre-mining period and on to early 1980, nine months after the sudden drop in groundwater elevations of May 1979. Depletions of some 3m, recorded over these nine months, were almost entirely confined to the major limestone bodies of Bracewell and East End. With few exceptions, stations outside the aquifers were unaffected. This is illustrated by Map 3.
Unfortunately, this pattern defining the aquifer locations was not picked up by the author of the Dudgeon report, who stated that no major aquifers had been located. Nor was any analysis of the monitoring results undertaken by either the mine consultants or the Department. Indeed, nothing was done with the data until the report came to the writer’s notice over two decades later (15).
There is more to the above pattern. The quasi-instantaneous response of the water tables in both the Bracewell and the East End limestone bodies reveals not only intimate hydraulic connections throughout each limestone aquifer but also points to an intimate hydraulic connection between the Bracewell aquifer and the East End aquifer.
Had the Dudgeon report been given satisfactory attention when first presented, most of the ongoing controversy about groundwater issues could perhaps have been avoided. Instead, both Dr Dudgeon and the relevant Government Department maintained that the depletion pattern in Bracewell was caused by dry conditions and had nothing to do with dewatering at the mine. Let us now look a little closer at this proposal.
4.2 The Relative Effects of Drought on Groundwater Depletions
An interesting indicator on the effects of dry weather on the water table is available in the monitoring data for 1977, that is, well prior to any mining activities. In the five month period from June to November of that year, a mere 6mm of rainfall was recorded in the Bracewell area. One would expect, if the onset of dry conditions seriously affected the aquifers, some widespread response would have been recorded during these dry five months. This was not the case. During the 1977 dry period, the stations available for monitoring in the lower Bracewell limestone - which is the particular area of contention – were W5, W6, W27, W28 W43; B12, B13, B31B. None of these showed any response to the 1977 dry period and, in fact, most of the water levels went up slightly. By contrast, when some 160 mm of rainfall was recorded in a similar time period from May 1979, - that is, after indications that groundwater lowering had commenced at the mine - water levels in the East End aquifer and in the above bores B12, B13 and B14 of the lower Bracewell limestone, dropped by some 2 to 3m.
On the same topic, it is also worth recording here that, on several occasions during the 1980s, the water levels in observation bores #03 (East End) and #04 (Bracewell) went down by some 3m during a twelve month period of average rainfall conditions. This unequivocally can not be attributed to drought effects. Even more extreme examples of the lack of response to prolonged dry periods come from quite separate sources.
The deep monitoring bore #07 on the western side of the monitoring area is in limestone but just beyond the boundary of the Machine Creek catchment, suggesting it is possibly isolated from the Bracewell aquifer. Here, a drop of only 0.5m was recorded over the whole of the prolonged dry period of the 1990s. On the opposite side of the monitoring area, levels in Wilmot Lagoon - again isolated, this time from the East End aquifer - were not noticeably affected during the same extended dry period of the 1990s.
How is it, then, that drought could be so localised that it affected only the lower Bracewell aquifer and nowhere else?
A second approach to assessing drought effects in the Bracewell aquifer is available from the patterns of depletion. Pre-mining and later groundwater contours in Bracewell show a subsurface seepage pattern down Machine Creek towards the Weir 2 “outlet”, a point that has already been mentioned and is illustrated by Map 4. A better illustration is given in section, taken through the middle of the lower Bracewell aquifer, Figure 4. Here, the 70m contour gradually moves some 4 km upstream, while the pattern of depletion clearly indicates an aquifer draining out through the downstream end: that is, in the direction of Weir 2. Had the cause of this aquifer depletion been drought, one would surely expect to see its effects first apparent in the upper reaches of the drainage system.
There is a further supporting factor. When looking at the levels of water supply bores in the Lucke property (just to the south of observation bore #04 in lower Bracewell), it was noted that the rates of aquifer depletion depended to a large degree on the water table elevation. Figure 5, taken from the writer’s report (17), shows a rate of depletion directly proportional to elevation, that is, to hydraulic head. This is a normal hydraulic relationship that has nothing to do with ambient climatic conditions.
In summary, all of the evidence available from the monitoring program indicates - contrary to the claims of the Department in paragraph 2 of the Executive Summary,
Version 1 - that drought has played no significant role in the depletion of the Bracewell aquifer.
The “drought” view does, of course, relieve the East End Mine of any obligation to make good losses in water supply in the Bracewell area.
4.3 The Bracewell-East End Connection
The probability of a hydraulic connection between the Bracewell and East End aquifers, via the alluvial veneer below the Weir 2 constriction, was first mooted by the writer in 1997 (8). The inference required confirmation by facts.
One piece of confirmatory evidence, albeit of a qualitative nature, came from the EEMAG observation that dry pools, downstream of Weir 2, begin to fill after rainfall events. This occurs despite the lack of flow over the weir and the lack of any surface flows in the creek bed for one or two hundred metres downstream of the weir. The observation stands alone as an adequate demonstration that there are strong subsurface flows within the alluvial deposits through the Weir 2 constriction. This view, however, has been dismissed by the relevant Government Department.
The first investigative follow-up on the proposal of an alluvial connection was a preliminary seismic survey. A traverse was run from upstream of Weir 2 for a distance of some 150m downstream, parallel to Machine Creek. Near to Weir 2, a cross line was taken from the stream to the Mt Larcom-Bracewell Road, about 100m distant. During the survey, the geophysicist happened to remark that he had not seen such a well-defined seismic record of basement (bedrock). This distinct basement was not, however, evident in the seismic sections of the seismic report (16). The layer overlying hard bedrock was designated as fractured/weathered rock OR boulders. The mine consultants chose to accept the weathered rock interpretation.
It is always a risky business to accept seismic profiles without some follow-up drilling. Two boreholes (BH98/1A & B) were drilled near to Weir 2, at locations chosen by the mine consultants – incidentally where the seismic profiles indicated localised highs in the bedrock. There was some controversy over the interpretation of the borehole logs, while insitu permeability tests carried out in the boreholes indicated relatively low permeabilities. The value of the alluvium as a hydraulic connector was therefore dismissed by the mine consultants and the relevant Government Department(s).
EEMAG then financed the excavation of two deep test pits carried out in the same locality as the drilling. The findings of these test excavations were detailed in the present writer’s report to the relevant Government Department. Here, the profile near Weir 2 revealed a sequence of strata comprising topsoil and alluvial silt overlying a whitish-yellow clayey silt, labelled “magnesite”, to around 3 - 5m depth. Below this was a calcrete horizon, 1 – 2m thick: hard when dry but more plastic beneath the water table (NB. The writer has come across similar calcareous materials elsewhere. A calcareous rock sample in India was like concrete, when dry. When put in a bucket of water overnight, it could be moulded like plasticine. Yet allowing it to dry out once more returned it to “concrete”). Below the calcrete horizon, a fine to medium subangular gravel was encountered. This was loose and had a tendency to collapse into the pit. Beneath the gravels was hard volcaniclastic bedrock at a depth of around 8m near to Weir 2. In the erosion environment that led to this breach in the line of volcaniclastic hills, one would expect the rockhead beneath an alluvial channel of this type to be relatively fresh and hard.
The calcrete horizon had other interesting properties. Although semi-cemented, it contained (solution) conduits of a centimetre or more in diameter. When the horizon was penetrated a short distance by the excavator bucket, clean water gushed into the pit and a very approximate permeability (equivalent to that of a coarse clean gravel) was estimated from the rate of rise of water in the pit. Neither the mine consultants not the Government officers were convinced that this sequence constituted an effective hydraulic connection between the two aquifers.
Subsequently, in 2007, EEMAG financed a further borehole, near the downstream end of the seismic profile. Here, bedrock had been indicated at around 12m depth. The drilling revealed the same sort of stratification as the test pits, with the exception that the bedrock was deeper although this depth was spot-on with the seismic profile. The calcrete horizon in the borehole was again a couple of metres thick and under subartesian pressures, even in the depleted water table conditions of the region. Again, the alluvial gravels underlying the calcrete were loose and found to contain a significant calcareous content. Bedrock, when encountered, was once more fresh volcaniclastic rock with no calcareous content. The borehole log is given in Figure 6.
This sequence now explained the interpretation of the “distinct basement” indicated in the 1997 seismic profiles. The cemented calcrete layer, with a higher seismic velocity than the underlying loose alluvial gravels, would have masked the gravels, making the stratum “invisible” in the seismic records. An alluvial sequence directly resting on the hard bedrock was therefore the sequence that produced such a distinct basement signature. Furthermore, the seismic survey as a whole showed that the Machine Creek alluvium had a width of at least 100m and a depth ranging from 6 to 12 m.
For the record, the mine consultant and the officer engaged to write the definitive Draft Final Report for the relevant Government Department still adhered to the geological interpretations put forward by predecessor(s) from the previous decade. In fact, out of hand, both allegedly told the driller he might as well stop drilling when he reached the calcrete as that was bedrock and the underlying loose gravels were no more than the product of drilling in highly fractured and weathered rock. The fact that the gravels were calcareous and so loose in nature that it was necessary to insert plastic lining tubes in the drill hole to prevent the gravels collapsing into the hole, was ignored.
Insitu pump-out tests made in the borehole gave reasonable permeability values, but not enough to justify declaring the alluvial connection adequate to produce the rate of Bracewell drawdown. It is, of course, an established fact that permeability testing in boreholes into calcrete or karstic limestone, each with a variety of drainage conduits, will typically provide gross underestimations.
Using the permeability values indicated from the test pits, that of a coarse clean gravel say (1 x 10-2 m/sec) the rate of loss within the calcrete horizon can be approximately given by the formula:
Where:
Q = A. k. i
Q = quantity of seepage
A = aquifer dimensions (100m wide, 2m thick)
k = calcrete permeability, 1 x 10-2 m/sec
i = hydraulic gradient
The hydraulic gradient here needs to take into account that the water in the calcrete horizon is under sub-artesian pressure and, at the commencement of mining, the head may have been four or five metres in this horizon, near the location of Weir 2. This head would have been lost on reaching the first of the semi-permanent pools some 200m downstream of Weir 2. Thus, a hydraulic gradient in the calcrete horizon of 1 in 40 or 50 would not be out of the question.
Substituting the above values in the equation gives a seepage rate of the order of 40 litres per second, even neglecting the contribution of the alluvial gravel stratum below the calcrete horizon. This rate is of the same order as the early pumping rate at the mine, a rate that initially led to the sharp decline in levels in both the Bracewell and East End aquifers. It is therefore inferred that, when the East End aquifer levels dropped as a result of mine pumping, it was as if a plug had been removed from the downstream end of the alluvial connection between the two aquifers. Under a subartesian hydraulic head, the Bracewell aquifer was then able to drain out to East End through the calcrete horizon with only a very short response time.
In 2002, in an independent attempt to establish a direct connection between the Bracewell and East End aquifers, a dye tracing experiment was undertaken by EEMAG under the direction of Senior Fellow D. Smith of the ANU, (13). The dye was injected into a sink hole near observation bore #04, in Bracewell. Samples were taken twice daily from the sump at the mine and tested. After some 39 days, one sample obtained at the mine was found to contain traces of the dye. So, too, was its back-up.
This, however, was declared to be the result of contamination by the relevant Government Department. A further back-up sample, held at the mine under unknown storage conditions for several months, was tested and found to be negative as might be expected for a sample stored for a long period – unless the storage was under strictly controlled conditions. On the basis of this doubtful testing - and some misleading hypothetical calculations regarding the rate of seepage from Bracewell to East End using a Darcian flow model (NB. According to work in the USA, rates of groundwater movement in karst terrains can be as high as 0.5km per day (James Sherrard, pers. comm.) - the relevant Government Department dismissed the positive results, stating that no further dye tracing would be countenanced. Once again, one would have to ask “Why not?”
4.4 Surface Flows in Machine Creek
These were first discussed in a report by the writer (9), after print-outs of the recorded flows over Weir 2 were produced in hard copy by the DNR, in 1997. The period covered was 1979–1996.
The records revealed that pre-mining flows over Weir 2 averaged 1.2 – 1.3 mgl/day, or around 15 litres per second. Flows reduced during the 1980s, paralleling the stopgo decline of water levels in Bracewell. There was a full recharge during the wet years of 1989-1990 and, following that, annual rainfalls were slightly below the average in 1991 and 1992, then well below the average in 1993. The rate of flow over Weir 2 also dropped sharply in this time. It began seriously in 1991: that is, well before the onset of the prolonged dry period of the 1990s. By 1993 flows over the weir became virtually non-existent and have remained so, apart from sporadic and short lived events associated with heavy rainfall. The stream bed below Weir 2 has dried out and the long and deep pools that used to be a characteristic of the lower reaches of Machine Creek also dried out by the late 1990s. Machine Creek is now devoid of fish.
A study of the historical flows of machine Creek over the weir was undertaken by a specialist team from the ANU in 2002, (12). This study reached the conclusion that the decline in flows was not a climate driven phenomenon but was the result of mine dewatering. The study concluded: “... we can safely dismiss claims that the changing rainfall patterns were causing Machine Creek to dry up... and we have discovered ... a compelling case for compensating water users in the vicinity.”
The relevant Government Department has, however, chosen to adhere to the 1995 view that this pattern of depleted flow is the result of drought alone. Again, we find a serious environmental consequence being demonstrated but receiving no cognizance by the relevant Government Departments.
4.5 Mining Effects on Other Aquifers
There was little effect on the water levels in the Jacobs Creek aquifer during the 1980s, despite the fact that the adjacent aquifer of lower Bracewell was allegedly suffering severe drought. By the 1990s, however, groundwater depletion to the south of the mine had migrated along the Scrub Creek environment, causing drainage of the Jacobs Creek aquifer. By the new century, rainfall events were producing freshets in the main (western) branch of Jacobs Creek, which is underlain by volcaniclastics. These would flood down from the high ground onto the flat valley floor and then disappear into the depleted Jacobs Creek aquifer.
A similar situation was exhibited by the Hut Creek system. With the original, pre-mining, water divide in the East End aquifer, Figure 2, water drained north into the Hut Creek catchment and springs developed on the slope north of the Mt Larcom-Bracewell Road. In the 1980s, these springs dried up as the water divide moved several kilometres to the north into the Hut Creek catchment and lost elevation. In this situation, the seepages in the Hut Creek catchment now drained south, to the mine. Hence, the supplies to Hut Creek were progressively depleted.
4.6 Evapouration from the Open Pit
In the long history of debate on the contentious issues, no written mention has ever made by the relevant Government Department, nor by the mine’s consultants, on the effects of evaporation from the open pit at the cessation of mining. The problem was mentioned to the writer, in passing, by the author of the Golders Report (11), although the matter was not raised in the report itself.
A pit one or two kilometres in length and at least 0.5 km wide is expected to remain at the cessation of mining. This pit would continue to receive seepages from the Bracewell-East End aquifer systems, keeping the open excavation partially filled. Evaporation from a pit of these dimensions in rock was estimated by the writer to be of the order of 50-60 litres per second and the matter was brought to the attention of the relevant Government Department. The Department replied with an estimate of 39 litres per second, after applying some doubtful reduction factors for a lake environment. The Department’s conclusion: “the matter does not warrant attention...” (Letter of 21 October, 2003).
Despite this dogmatic denial, it needs to be recorded that the modest evaporation figure admitted to by the Department is of the same order of magnitude as the average rate of pumping from the open excavation in the early days of mining, as recorded by C.R. Dudgeon. This rate was quite sufficient to deplete the aquifers at their full capacity; it was also sufficient to “mine” the aquifers, making them now unable to recharge fully, even after major rainfall events, as shown by the latest monitoring.
Future evaporation from the abandoned open pit will therefore ensure that the aquifers will never recharge; that Machine Creek and other surface streams in the region will remain dry and never be able to resume their former flows nor support their former spectrum of life.
These are serious environmental indictments but, according to the relevant Government Department, they do not warrant attention.
4.7 Other Violations of Good Environmental Practice in the Lease Conditions
Conditions for the East End Mining Lease renewal were granted in 2003 by the DNR and the Environmental Protection Agency (EPA). The lease conditions were based on the interpretations presented in the 1995 Dudgeon Report (4). It might be recalled that, in 1995, Dr Dudgeon still held to the belief that aquifer depletion in East End was of the order of 2 – 3m maximum, with a cone of depression extending no further than about 0.5 km from the mine. In fact, depletions of the order of 13m were already being recorded in the East End aquifer, extending some 5km distant from the mine.
Despite the recognised tenet that good environmental practice requires all new information to be taken on board when it becomes available, and despite all the information gained since 1995, the DNR and EPA chose to utilise obsolete and misleading data.
In the new lease conditions, liberal conditions were imposed on the mine regarding the quantities of waste water that could be pumped from the mine and discharged into the natural watercourse, Larcom Creek. The limits imposed depended on conductivities. The Annual Water Monitoring Reports of 2002-2003 and 2003-2004 (presented by Groundwork Environmental & Management Services P.L.) reveal that the criteria have been breached for months at a time in both 2003 and 2004. Apparently, no disciplinary measures have been taken.
The writer’s understanding is that the original lease conditions imposed a bond of $25,000. Such an amount is quite inappropriate for a project of this magnitude, particularly where environmental concerns have been raised at the very outset. An inappropriately minor bond provides no incentive for a mining company to adhere to any conditions of lease or to making good at the end of the project’s life. It is more economical to walk away from a mess and simply pay the bond.
5 THE DRAFT FINAL REPORT (DNRM&W, DERM)
In May, 2006, the relevant Government Department (Department of Natural
Resources, Mines and Water) produced a Draft Final Report for discussion, Version
1: Review of Groundwater Issues, East End Mine. Following discussions at Bracewell with EEMAG and its consultants (NB. Professor Brian Finlayson (Melb. Univ.) and Senior Fellow Dingle Smith (ANU), both global experts on the behaviour of karst aquifers, together with the writer), this has been modified twice, being now at Version 3. However, the Department’s stance on drought (in Bracewell) and on a number of other vital matters, has not been sensibly altered.
In other words, the plethora of errors from Version 1 is generally still extant; others have been added. Some of the most glaring have been discussed above, some have recently been relayed to the relevant Government Department in references (20), (21) and (22).
For instance, one does not realistically continue groundwater contours from an aquifer across a geological boundary into volcaniclastics where the change in permeability is several orders of magnitude. This has been done consistently in the DFR (NB. A lower permeability unit can be taken as “impermeable” when a permeability difference of only one order of magnitude obtains).
Possibly the most outrageous renunciation of the principles of groundwater behavior is to be found in the Departmental author’s classification of aquifers, from which he has produced a series of meaningless tables. The aquifer “units” comprised an interfusion of aquifer portions, volcaniclastic terrains, elevated catchment boundaries, and alluvial flats. Aquifer Unit 3, for instance, shown herein as Map 5 (Map 17 of Version 3 report) is labelled as “Jacobs Creek-Scrub Creek limestones in the Lower Bracewell area”. The title is perplexing enough, since neither the Jacobs Creek nor the Scrub Creek limestones are within the Bracewell area. The unit itself is even more out of touch with reality. It takes in almost the whole of the lower Bracewell limestone aquifer and extends south across the catchment boundary of Machine Creek into theelevated volcaniclastic rocks of the upper reaches of Jacobs Creek. The unit then continues south over Scrub Creek’s catchment boundary and down to the flat alluvial lands fringing Scrub Creek. How this could be presented as a unit defies belief. Even the relatively uniform East End aquifer is broken up into four units: 1, 4, 5, and 9, again with pockets of volcaniclastic rocks. The only outcome from such illogical classifications, and the dismissal of basic hydrogeological principles, is a confusion of data. Either the confusion is intentional or we have here the clear inference of gross ineptitude.
Early in 2010, when the most recent version of the DFR was issued, the Department requested that all outside parties, including EEMAG, give written approval for their discussion-based submissions to be included in the final report. Since all the outside submissions selected for inclusion in the DFR, to date, have been followed by Departmental refutation, typically specious, it appeared to the present writer that giving written approval could be tantamount to giving official condemnation of one’s own submissions. On questioning the requirement for written approval, the reason was said to be necessary in order to satisfy freedom of information and/or privacy requirements. A request was then made by the present writer to the Department for information on the legislation/ruling(s) that covered this requirement. As of now, there has been no Departmental response to this.
REFERENCES
1 James P.M. (1974). Report on the geohydrological effects of proposed limestone mining, Mt Larcom-Bracewell area.
2 Dudgeon C.R. (1980). Bracewell-East End groundwater monitoring, Review of the first three years’ results; plus Attachments. Univ. NSW Tech. Rpt 80/4
3 Dudgeon C.R. ( ). (Tech Paper, n.a.)
4 Dudgeon C.R. (1995). Water resources around East End limestone mine: effects of proposed extension of QCL (Gladstone). Univ. NSW Water Research Lab., Rpt 95/11 (draft)
5 Kalf & Assocs (1997). Groundwater model determination of current and future East End mine pit drawdowns. Rpt, Feb. 1997
6 Kalf & Assocs (2000). Interpretation of the groundwater situation at East End and Bracewell. Rpt Dec. 2000
7 James P.M. (1995). Bracewell-East End: groundwater monitoring review. Rpt to Kershaw & Co., Sept.
8 James P.M. (1997). East End mine: groundwater review. Rpt to CLG, July
9 James P.M. (1997). Historical flows - Weir 2. Rpt to CLG, 25 November
10 DNR (1998). Position paper, East End mine and environs. Presented at meeting in Rockhampton
11 Golder Assocs (2001). Review of hydrological impacts: East End Mine. Rpt to EPA, May
12 Spate J. (2002). Investigation into stream flow data for the Machine Creek catchment. Rpt to EEMAG by Centre for Resources & Environmental Studies, ANU, Canberra
13 Smith D.I. & EEMAG (2002). Artificial pulse dye injection trial at Bracewell, 9 May – 30 June. Aug.
14 Lucke A (2005) Water injection of sinkholes. Rpt, July
15 James P.M. (2005). Bracewell-East End hydraulic connection: new and definitive data. Rpt to DNR/QCL/EEMAG
16 Velseis (1997). Seismic refraction survey, East End Mine. Rpt to Kershaw
17 James P.M. (1999). Lucke farm, Bracewell: underground water supply failures & East End Mine. (April)
18 DNR Mines & Water (2006). Review of groundwater issues, East End Mine.
19 Dept of Natural Resources and Water (2010) Review of groundwater in the Mt Larcom-Bracewell area. Draft Final Report, 3rd version
20 James P.M. (2005). Open cut East End Mine, Groundwater studies 1977- 2005: Summary of environmental impacts and official responses. August
21 James P.M. (2007). Bracewell-East End hydraulic connection, further investigation. Rpt for EEMAG & DNR&M. June
22 James P.M. (2008). Response to certain specific matters in DNR&M Final Draft Report on groundwater, Nov. 2008. 2nd version.
23 EEMAG: Various reports and communications since 1995
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