Supporting report C - Hydrogeology

Supporting report C - Hydrogeology.pdfFLOW ENVIRONMENTAL MANAGEMENT PTY LTD ACN 089 767 279
PO Box 3358 Norwood SA 5067 T: + 61 8 8333 0870 F: + 61 8 8431 4628
FINAL REPORT
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EXECUTIVE SUMMARY
Flow Environmental Management was engaged by Heathgate Resources Pty Ltd to undertake a desktop study of the local and regional hydrogeology of the Beverley Mine Exploration Lease 3251 (EL3251). This ‘Technical Report’ report will act as a basis to support any environmental approval documentation required for an additional mining lease within EL3251 (the study area).
This report provides the details of a desktop study of the hydrogeological characteristics of the study area and updates the hydrogeological assessment of the June 1998 Environmental Impact Statement (EIS) for the current mine operation. A large part of the regional geological discussion in the EIS remains valid for the study area. Therefore, the hydrogeological setting discussion is primarily sourced from the EIS but also includes revisions of the conceptual understanding and detailed evaluation of water level observations, which has been collected since the commencement of monitoring in 2001.
The Beverley uranium deposit is located within the western Frome Embayment region where groundwater occurs in several separate aquifer systems (from deepest to shallowest):
Mt Painter Complex and other fractured rock aquifers (Proterozoic); Great Artesian Basin (GAB) aquifer - the Cadna-Owie Sandstones (Mesozoic); Eyre Formation - blanket and palaeochannel sands which are not thought to be extensively
developed at Beverley (Tertiary); Namba Formation aquifers - Beverley and Alpha, Beta and Gamma Sands (Tertiary); and, Willawortina Formation and younger aquifers - conglomerates and poorly sorted sands in clays,
and those aquifers in the younger stream sediments, which have been incised into the Willawortina Formation (Tertiary and Quaternary).
Between and within each of these aquifers are aquitards.
New exploration drilling and re-interpretation of old drilling data have led to the recognition of a more complex pattern of channel sands than that outlined in the EIS.
In plan view, several new mineralised zones, referred to as “trends” have been described:
Northeast sands lying immediately to the east of the North Beverley Orezone and trending towards the east. This sand body has been tested for continuity with Beverley North and found to be essentially a separate sand lens surrounded by sits and clays.
Beverley East trend, which extends from the eastern side of the Central Beverley Orezone in a position, which approximately coincides with the projected Central Channel shown in EIS Figure 6.4.
Deep South area with two essentially north-south trending mineralised sands, including: 1. Russell trend, which lies to the east of a southerly extrapolation of the Beverley South
Orezone (roughly coinciding with the South channel shown on EIS Figure 6.4); and 2. Poontanna trend, which lies approximately one km west of the Russell trend and over three
km south of the current mine lease (ML) boundary.
EL 3251 HYDROGEOLOGY STUDY BEVERLEY URANIUM MINE
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In vertical profile, drilling below the Alpha Mudstone (which lies below the Beverley Sand) has revealed a series of mineralised sequences of sand, separated by mudstones and grading laterally into silts/clays. These sands have been designated Alpha, Beta and Gamma sands and the intervening mudstones bear the name of the underlying sand zone. Thus the stratigraphic sequence, where fully developed consists from top downwards of:
Beverley Sand; Alpha Mudstone; Alpha Sand; Beta Mudstone; Beta Sand; Gamma Mudstone; Gamma Sand; Delta Mudstone; Delta Sand; Lower Namba Carbonate; and Eyre Formation.
Since the commencement of mining operations, a series of monitoring wells have been installed within and near the boundaries of the channel sand deposits, predominately within the current mining lease boundary. The majority of these wells intersect the Beverley Sand aquifer, providing a very good spatial distribution for understanding the water level responses in this aquifer. These wells are either screened within the sand body of the orezone or within low permeability silty-clay sediments at the margins of the channel sands, both laterally and vertically. A total of eight wells have been screened across the Alpha Sand aquifer. In addition, a number of wells intersect the overlying Willawortina Formation. Gauging information pertaining to these wells is available from 2001. Three wells have been installed within the southern portion of the EL3251. For two of these wells, gauging records since early 2005 are available for the assessment of temporal trends. Apart from these three wells, the hydrogeological setting for the study area is primarily sourced from the EIS.
Water levels measured in the Namba Formation, prior to the commencement of the 1997 round of groundwater pumping activities at Beverley (the method of mining), were approximately 60 m below ground level, at elevation levels of 17.74 m (+/-0.16 m) AHD. These levels may be taken to represent the undisturbed groundwater levels within the palaeochannel sands. The recorded levels within the aquifer infer a very low hydraulic gradient, indicative of a low potential for groundwater flow. More recent water level data observed at monitoring wells outside the boundaries of the orezones and the current mining lease area indicate static water levels, which are not considered to be influenced by mining activities. A detailed review of the temporal water level trends within the current mining lease area and near the mining zones has identified the following key findings:
Water levels of wells intersecting the low permeability sediments show a slow water level recovery back to pre-mine baseline levels following well development and routine groundwater sampling. This slow recovery process has been observed within the wells intersecting the low permeability silt-clay sediments of the aquitards within the different mineralised sand aquifers.
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Wells intersecting the Beverley sand aquifer respond rapidly to on-going mining activities. Pumping tests and groundwater level observations have been used to determine the hydraulic
connection between North, Central and South Orezones. Based on these observations, the North Beverley Orezone is considered to be poorly hydraulically connected with the Central Beverley Orezones but a higher degree of hydraulic connection exists between the South and Central Beverley Orezones.
Water level responses to mining correlate with the inferred geological boundaries of the channel sand deposits and can be used to confirm these boundaries.
The existing mine Environmental Monitoring Management Plan (EMMP) was based on the known extent of the Beverley Channel Sands at the time of the commencement of mining. As new mineralised zones have been discovered and developed, changes to the monitoring well layout have been progressively approved but not consolidated within the EMMP documentation on a regular basis. The Beverley mining leases currently operate under three sets of legislation, each requiring a planning document. The three documents currently submitted are:
EMMP; Mining and Rehabilitation Plan; and Radioactive Waste Monitoring Plan.
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TABLE OF CONTENTS
2.1.1 Regional Groundwater Wells ................................................................................ 12 2.1.2 Groundwater Monitoring Wells at Beverley ........................................................... 12
2.2 Mr Painter Complex Hydrogeology ....................................................................................15 2.3 Great Artesian Basin..........................................................................................................15 2.4 Eyre Formation ..................................................................................................................17 2.5 Namba Formation ..............................................................................................................18
2.5.1 Lower Namba Formation (Alpha Mudstone Sequence) ........................................ 23 2.5.2 Upper Namba Formation (Beverley Sands and Beverley Clay) ............................ 25
2.6 Willawortina Formation.......................................................................................................30
4 REGIONAL AND DISTRICT GROUNDWATER QUALITY ........................................................49 4.1 Regional Groundwater Quality Data Sources ....................................................................49 4.2 Groundwater Quality in the "Shallow" Aquifer of the Flinders Ranges and Plains..............49 4.3 Groundwater Quality in the Great Artesian Basin (GAB) Aquifer ......................................52 4.4 Groundwater Quality in the Baseline Study Area ...............................................................53 4.5 Groundwater Quality in Beverley Site Aquifers ..................................................................61
4.5.1 Willawortina Formation.......................................................................................... 61 4.5.2 Namba Formation ................................................................................................. 63
5 GROUNDWATER FLOW, INTERCHANGE AND DISCHARGE ................................................67 5.1 Regional Patterns ..............................................................................................................67 5.2 Beverley Aquifers...............................................................................................................69
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6 CONCEPTUAL MODEL OF THE BEVERLEY AQUIFER SYSTEM ..........................................72
7 REFERENCES ..........................................................................................................................75
Figure 1: The Study Area
Figure 2: Location of Registered Groundwater Wells within Approximately 25 km Radius of the Study Area
Figure 3: Location of Beverley Mine Monitoring Wells
Figure 4: Location of GAB Bores
Figure 5: Cross Sections
Figure 7: Alpha Mudstone Surface with Schematic Geological Cross Sections
Figure 8: Upper Namba Formation (Beverley Sand and Lateral Silt Equivalent Wells) Local Water Levels (m AHD) – June 2005
Figure 9: Upper Namba Formation (Beverley Sand) Local Water Levels (m AHD) – June 2005
Figure 10: Upper Namba Formation – Selected Hydrographs
Figure 11: Location of Water Wells
Figure 12: Willawortina Formation Regional Water Levels (in m AHD) – Pre-Mine
Figure 13: Willawortina Formation Local Water Levels (m AHD) – July 2006
Figure 14: Location of Poontana Fault Zone
Figure 15: Poontana Fault Zone
Figure 16: Water Level Trends of Wells Intersecting Low Permeability Sediments and Wells Intersecting The Beverley Sand Sediments
Figure 17: Regional Salinity Data for Hard Rock Aquifers
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Figure 18: Regional Salinity Data for the Willawortina Formation
Figure 19: Regional Variation in Groundwater Salinity with Depth, Willawortina Formation
Figure 20: Groundwater Salinity Distribution, Baseline Study Area
Figure 21: Groundwater pH Distribution, Baseline Study Area
Figure 22: Uranium in Baseline Study Area Shallow Aquifer Water Samples
Figure 23: Distribution of Uranium Concentrations in Baseline Study Area Shallow Aquifers
Figure 24: Distribution of Radium Concentrations in Baseline Study Area Shallow Aquifers
Figure 25: Distribution of Radon Concentrations in Baseline Study Area Shallow Aquifers
Figure 26: Willawortina Formation Local Electrical Conductivity Observations (mS/cm)
Figure 27: Beverley Formation Local Electrical Conductivity Observations (mS/cm), July 2006
Figure 28: Regional Groundwater Flows
Figure 29: Conceptual Model in Vicinity of Beverley Channels
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TABLES
Table 2: Stock Wells and Springs .................................................................................................... 32
Table 3: Aquifer Test Data, Willawortina Formation......................................................................... 34
Table 4: A Namba Formation Aquifer Hydrological Parameter Values ............................................ 42
Table 5: North East Pumping Test Results ...................................................................................... 44
Table 6: Water Quality in GAB Bores............................................................................................... 53
APPENDICES
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1 INTRODUCTION
Flow Environmental Management was engaged by Heathgate Resources Pty Ltd to undertake a desktop study of the local and regional hydrogeology of the Beverley Mine Exploration Lease 3251 (EL3251). The site is located on the arid plains between the North Flinders Ranges and Lake Frome, approximately 600 km north of Adelaide. This ‘Technical Report’ will act as a basis to support any environmental approval documentation required for an additional mining lease within EL3251 (the study area, Figure 1).
The report provides details of a desktop study of the hydrogeological characteristics of the study area and updates the hydrogeological assessment of the June 1998 Environmental Impact Statement (EIS) for the current mine operation. A large part of the regional geological discussion in the EIS remains valid for the study area. Therefore, the hydrogeological setting discussion is primarily sourced from the EIS but also includes revisions of the conceptual understanding and detailed evaluation of water level observations, which have been collected since the commencement of monitoring in 2001.
Figure 1: The Study Area
Source: URS (2007)
2 OUTLINE OF HYDROGEOLOGY
Within the western Frome Embayment region, the major hydrogeological system in which the Beverley deposit is located, groundwater occurs in several separate aquifer systems (from deepest to shallowest):
Mt Painter Complex and other fractured rock aquifers (Proterozoic);
Great Artesian Basin (GAB) aquifer - the Cadna-Owie Sandstones (Mesozoic);
Eyre Formation - blanket and palaeochannel sands which are not thought to be present at Beverley (Tertiary);
Namba Formation aquifers- Beverley and Alpha, Beta, Gamma and Delta Sediments (Tertiary); and,
Willawortina Formation and younger aquifers - conglomerates and poorly sorted sands in clays, and those aquifers in the younger stream sediments, which have been incised into the Willawortina Formation (Tertiary and Quaternary). These systems are considered as a single unit in this text.
Between and within each of the aquifers are aquitards. The complete stratigraphy is shown in Table 1.
In the following sections the aquifer sequence is described, with emphasis on those potentially affected by the proposed mining, the Namba Formation and Willawortina Formation aquifers.
Table 1: Summary of Groundwater Analytical Results
Time Units * Symbol Unit Description
Qha1 Sands and Gravels Modern stream deposits. Intermittently reworked sands, gravels and cobbles. Holocene
Qhe2 Simpson Sand Modern dune system of the Strzelecki Desert.
Late Pleistocene to Holocene Qec Coonarbine Formation Flat low-lying clayey sand plains.
Qu ate
rn ar
y
Medial to Late Pleistocene Qpae Eurinilla Formation Flat low-lying clayey sand plains with lower part
cemented by gypcrete or calcrete.
Late Miocene to Early Pleistocene TpQaw Willawortina Formation
Sheeted gravels and clayey sands. Forms basic landscape of uplifted High Plain flanking the Flinders Ranges.
Late Eocene to Palaeocene Tsi Undifferentiated Duricrusts
Silcrete-Porcellanite-Greybilly, usually local cap rocks to other units in proximity to the Range Front. Multiple ages.
Namba Formation-Upper Olive Grey swelling clay, dolomite nodules, and beds, greenish laminated silt and fine sand. Includes Beverley Sands. No exposures.
Miocene Topn
Namba Formation-Lower
Olive Grey swelling clay, dolomite nodules, and beds, greenish laminated silt. Includes Alpha, Beta and Gamma Sands and associated Mudstones at Beverley. Localised dark sandy claystones. No exposures.
Ca ino
zo ic
Te rtia
Palaeocene- to Eocene Taee Eyre Formation
Uncemented quartz sand, some clay beds, minor lignite. Often capped by Tsi. Exposed near ranges 25Km north of Beverley, concealed at depth to the east.
Kmb Bulldog Shale
Clay and silt, lesser sandy lenses. Local exposures in the western portion of the high plains. Concealed at depth to the east.
Knr Parabarana Sandstone
Knr: Quartz Sandstone, pebbly conglomerates, and basal channel fill deposits. Local relict outliers in the ranges and low relief areas of the western portion of the High Plains.
Me so
zo ic
Cr eta
ce ou
Palaeozoic Ordovician Undifferentiated eOdi British Empire Granite Granite, Freeling Heights area.
Ne o -
Pr ote
ro zo
Sandstones, siltstones, shales and limestones, lesser mafic volcanics. - Gammon Ranges
Pr ote
ro zo
Quartzite, pebble conglomerates, rhyolites: porphyries and granites. schists and gneiss – Mt. Painter ~ Mt Neil (Range s due west of Beverley).
* The time units of this table are oldest at the bottom and youngest at the top
Source: Mines and Energy South Australia (MESA), now Department of Primary Industries and Energy Resources SA.
2.1 Groundwater Monitoring Network
2.1.1 Regional Groundwater Wells
Registered groundwater wells within approximately 25 km radius of the site are shown in Figure 2. The locations have been extracted from the PIRSA groundwater database. The figure also includes the recorded depth, well purpose and observed total dissolved solids. The majority of the registered wells have been drilled to depths less than 100 m below ground level. The current status of the wells is not known and some may have been abandoned.
2.1.2 Groundwater Monitoring Wells at Beverley
Since the commencement of mining operations, a series of monitoring wells have been installed within and near the boundaries of the channel sand deposits, predominately within the current mining lease boundary. Figure 3 shows the location of the groundwater monitoring wells, including the aquifer that the wells are monitoring.
The majority of these wells intersect the Beverley Sand aquifer, providing a very good spatial distribution for understanding the water level responses in this aquifer. These wells are either screened within the sand body of the orezone or within low permeability silty-clay sediments at the margins of the channel sands, both laterally and vertically. A total of eight wells have been screened across the Alpha Sand aquifer. In addition, a number of wells intersect the overlying Willawortina Formation. Gauging information pertaining to these wells is available from 2001.
Three wells (DSMW1, PRC1 and PRC2) have been installed within the southern portion of the EL3251 (Figure 3). For two of these wells, gauging records since early 2005 are available for the assessment of temporal trends. No gauging information is available for PRC1. PRC1 monitors the Beverley Sand aquifer, PRC2 the Beta Sand aquifer and DSMW1 the Willawortina Formation. For the area outside the current mine lease, apart from these monitoring wells, the hydrogeological setting for the study area is primarily sourced from the EIS.
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2.2 Mr Painter Complex Hydrogeology
The Mt Painter Complex and other crystalline rocks of the Flinders Ranges comprise fractured rock aquifers with the highest yields near to faults, where most springs occur (Ker 1966). Recharge is by limited direct infiltration from rainfall. Water quality is variable, from less than 1,000 mg/L to more than 10,000 mg/L Total Dissolved Solids (TDS). The water table in the fractured rock system, though variable, is the highest in the western Frome Embayment region. Discharge occurs into the numerous ephemeral creeks and along the range front at springs, such as Paralana Hot Springs. Discharge probably occurs also by under flow into the sedimentary aquifers of the Frome plains where these directly overlie or abut the fractured rocks.
2.3 Great Artesian Basin
The Lake Frome Embayment is identified as a discharge area for water from the GAB aquifer system. In the basin in general, pressure declines to the west and south, away from the recharge areas in New South Wales and Queensland (Habermehl 1980, Callen 1981b). Discharge is from identifiable point sources (the mound springs) and from other dispersed leakages through the overlying Bulldog Shale, particularly where it thins towards the basin margin. Water lost from the GAB aquifer by diffuse upward vertical leakage enters aquifers higher in the sequence and is eventually lost to evaporation, which is the principal discharge mechanism of the Lake Frome region.
There are no mound springs close to the Beverley Project. The nearest mound springs are on the Lake Frome bed, and north of Moolawatana station on the northern fringe of the Flinders Ranges (Boyd 1990). The water source of the nearer Paralana Hot Springs appears to be local recharge from the Flinders Ranges. The head in the GAB system is less than 100 m Australian Height Datum (AHD) to the west of Lake Frome and the potentiometric surface exhibits a broad depression, centred on Lake Frome, due to the influence of springs and flowing bores.
The Cadna-Owie Formation is the only GAB aquifer present in the area to the west of Lake Frome.
Seismic data and drilling appear to confirm the continuity of the Cadna-Owie Formation beneath the Beverley site and the Cadna-Owie Formation is thought to be the aquifer intersected in the Four-Mile Flowing Bore (“Camp Bore”) at Beverley. The aquifer exceeds 19 m thickness in Camp Bore and flowed at 5 L/s with a shut in head equivalent to approximately 90 mAHD and a temperature of 50 degrees celsius. It is regionally a moderate salinity groundwater source being approximately 2200 mg/L TDS at Camp Bore.
A new GAB water supply well (GAB 3, refer to Figure 4) was drilled in 1999 within the current mining lease. This well is used to provide feedwater to the RO Plant to provide
potable water for the camp supply and in the plant as make-up water at a TDS of 2050 mg/L.
The Cadna-Owie Formation is capped regionally by the Bulldog Shale (Marree Subgroup). The Bulldog Shale may be absent or thin in the Camp Bore intersection, being replaced with the Lower Namba Formation, a major aquitard. The vertical separation between the GAB aquifer and the Beverley mineralised zone aquifer horizon exceeds 100 m at Camp Bore and 194m (including 116 m of Bulldog Shale) at the new water supply well.
Recent exploration drilling on the Poontana Trend has intersected a sequence of Cretaceous sediments, which have now been identified (palynology) as Bulldog Shale overlying Cadna-Owie Sands. These units can be seen in Figure 5 section E – E’ below about 145m in Drillhole PR106 which is located on the upthrow side of the Poontana Fault. Several exploration holes on the upthrown side of the fault have penetrated at least part of the Creatceous sequence. These holes include PR106, PR104, PR102, PR074, PR073, PR063, and PR072, PR071, PR051 and PR0070.
Figure 4: Location of GAB Bores
2.4 Eyre Formation
The Eyre Formation is not thought to be well represented in the stratigraphic column at Beverley. However, regionally it comprises a blanket sand over the central and western Frome Embayment margins (Callen 1977, Waterhouse and Beal 1978). The Eyre
Formation is the host aquifer for uranium deposits within palaeochannels in the southern portion of the Frome Embayment (eg. the Honeymoon Deposit).
Water in the Eyre Formation is generally of poor stock water quality or worse, and it is an aquifer of last resort where better quality water cannot be found in shallow aquifers near by. The salinity range of Eyre Formation water is 3,000 to 10,000 mg/L for wells 45 km to 85 km south of Beverley.
2.5 Namba Formation
Drilling by Heathgate has included the installation of several new observation wells in the Namba Formation. The location of these wells is shown in Figure 3. Hydrographs since the commencement of gauging are presented in Appendix 1.
Figure 5 presents a number of cross sections showing the surface elevation of the Namba Formation sediments.
Water levels measured in the Namba Formation, prior to the commencement of the 1997 round of pumping activities at Beverley, were approximately 60 m below ground level, at Elevation Levels of 17.74 m (+/-0.16 m) AHD.
The baseline water levels were measured in the Central area in March 1997 after the aquifers had lain undisturbed since the mid-1980s. A series of water levels recorded in the RM series of holes at the same time fall within the same range and includes holes RM1 from the North area to RM7 in the South area (Figure 6). These levels may be taken to represent the undisturbed water levels within the palaeochannel sands.
Figure 5: Cross Sections
2.5.1 Lower Namba Formation (Alpha Mudstone Sequence)
The Lower Namba Formation unit is widespread, comprises black clays and confines the Eyre Formation regionally and the Cadna-Owie Formation where Eyre Formation is absent. At Beverley, recent drilling penetrating the Lower Namba Formation has revealed a more complex sequence than previously described.
The surface topography of the Alpha mudstone is illustrated in Figure 7 together with several stylised cross sections showing the entrenched nature of the Beverley channels (Figure 5).
Figure 6: Beverley Sand Baseline Water Levels
6660000mN
6658000mN
Figure 7: Alpha Mudstone Surface with Schematic Geological Cross Sections
In the vicinity of the Beverely Channel the Alpha Mudstone sequence contains several older lenticular sand zones, which have been designated Alpha, Beta and Gamma in order of increasing depth below the base of the Beverley Sand. These sands are believed to be associated with former strand lines of a proto Lake Frome and each sand is underlain by a similar dark clay layer (Figure 5). In Camp Bore the unit exceeds 100 m in thickness and in GAB3 within the existing mining lease, a thickness of 78m was intersected. The geological section shows the unit to thicken somewhat to the east from Camp Bore.
2.5.2 Upper Namba Formation (Beverley Sands and Beverley Clay)
Callen (1977) has identified the Upper Unit of the Namba Formation over a wide area of the Frome Embayment. Regionally it comprises clays and silts within subordinate thin, fine-grained sand beds. The Namba Formation is not generally considered to comprise a significant aquifer and accordingly, there is no regional quantitative assessment of its hydraulic properties. The sands of the Upper Unit, wherever they do occur, are capped by a clay (Callen 1975, 1977). The deposition of the clay capping concluded sedimentation in the Namba Formation.
At Beverley, there are three sub-units identifiable within Callen’s Upper Unit where there is a thickening in the palaeochannel. These comprise:
Beverley Clay;
Beverley Silt; Beverley Sands up to three sand units with silty lateral equivalents separated by finer
grained interbeds.
Figure 8 shows computer drawn water level contours for the Upper Namba Formation, which includes the wells intersecting both the Beverley sands and their lateral silty/clay equivalents. The potentiometric surface shown in Figure 8 suggests a spatial hydraulic gradient variation across the unit. The steep gradients reflect the extremely low hydraulic conductivity of the silts/clays intersected by the wells located along the margins of the channels (i.e. lateral confinement due to facies changes from sand to silt/clay within the same stratigraphic horizon). Exclusion of the wells intersecting the low permeability silts and clays outside the channel proper, shows a plateau-like area of elevated pressures within the channel with a very low hydraulic gradient, indicative of a low potential for groundwater flow as shown in Figure 9.
In the immediate vicinity of Beverley, water level fluctuations (Appendix 1) are variable with time associated with mining activities. Selected wells showing the water level fluctuations are presented as Figure 10. Compared to the baseline water levels, the observed water levels show a response to mining activity for the wells intersecting the Beverley sands. Water levels of wells intersecting the low permeability sediments show a slow water level recovery back to pre-mine baseline levels following well development and routine groundwater sampling. Water level data observed at monitoring wells outside the boundaries of the orezones and the current mining lease area indicate static water levels, which are not considered to be influenced by mining activities.
Figure 8: Upper Namba Formation (Beverley Sand and Lateral Silt Equivalent Wells) Local Water Levels (m AHD) – June 2005
Note: Density correction not applied
Figure 9: Upper Namba Formation (Beverley Sand) Local Water Levels (m AHD) – June 2005
Note: Density correction not applied
Figure 10: Upper Namba Formation – Selected Hydrographs
Well Intersecting Beverley Sands – Outside Channel Sand Deposit
Well Intersecting Beverley Sands
Well Intersecting Beverley Silts/Clays
2.6 Willawortina Formation
There are over twenty stock watering wells of relatively low yield within the area shown in Figure 11, which appear to be drawing water from the Willawortina Formation. For those within 15 km of the Beverley site, the reported static water level (SWL) varies from 4 to 40 m, with an average of 19 m (Table 2).
A reconstruction of the regional Willawortina Formation potentiometric surface is presented in Figure 12, which is derived from the water level observations of Ker (1966), which were reported in feet, and includes the undisturbed pre-mining water level observed at the Central FLT site (16.2 m) for comparison. The general gradient is towards the discharge area of Lake Frome to the southwest at approximately 0.5 m per km.
Stock bores are deliberately sited where the prospects of obtaining better quality water at shallow depths are improved, particularly along the banks of the incised creeks which cross the western Frome region from west to east. Consequently they may tap more recent creek channel deposits rather than the Willawortina Formation, in the strict sense, but these are considered to comprise the recharge sources for the Willawortina Formation, and will be considered as integral with it.
The Willawortina Formation at Beverley has been shown from cuttings logs, downhole geophysics and the observation well data to comprise a number of thin aquifers separated by clay layers. The Formation extends from the surface to a depth of approximately 100 m. The suggested geological environment would lead to the deposition of sheet-like over-bank deposits and immature alluvial channel fill. Such environments produce multi-layered, poorly interconnected aquifers in which the permeability, while variable, is usually low as a consequence of the poorly sorted nature of the aquifer sands.
Pre-mining results are included in Table 2. The piezometric data show the formation to be saturated below about 60 m depth. Airlifted yields range from 0.001 to 0.3 L/s, which are extremely low for material classified as an aquifer. Aquifer property data for the Willartina Formation are presented in Table 3.
Figure 11: Location of Water Wells
WOOLTANA HS
WOODNAMOKA WELL
Table 2: Stock Wells and Springs
WELL ID WELL NAME TOTAL DEPTH SWL TDS RADIONUCLIDES (Ker 1966) (Ker1966) (m) (m **) *(mg/L) U µg/L Ra Bq/L
23 Paralana Hot Springs
1058 (n=5) 16 (n=4) 14 (n=7)
25 Box Bore 49 14 758 (n=3) 34 Pepegoona Bore 75 21 1072 29 20
36 South Poontana Bore
Bore 110 27 1010 96 26
47 North Mulga Bore 42 30 1495 34 40
49 Buxton Bore 2616 53 Mungaroonie Bore 37 24 799 69 99.5
54 Christmas Well and Bore
23 4 3084 81 34.3
55 Sandridge Bore 26 18 2845 119 36.7 67 Mulga Park Bore 39 4 3850
121 Ram Bore 29 15 6504 13.5 0.05
133 On Wooltana Station
138 John Brown Bore 44 40 1515 20.5 4.8
Munyallina Creek 3.7 0.018
Note: Unspecified method of determination ** metres below ground level (n=5) etc: value shown is average from n analyses.
Source: Armstrong(1998)
Figure 12: Willawortina Formation Regional Water Levels (in m AHD) – Pre-Mine
4.9
5.0
10.0
12.5
12.3
Table 3: Aquifer Test Data, Willawortina Formation
BOREHOLE SCREEN (m) TEST AIRLIFT (L/s)
K (m/d) TDS (mg/L) SWL (m **) COMMENTS SOURCE
37/04 84.5 - 90.5 Airlift 0.001 - 2,400* 65.56 No connection to
aquifer
?
VSH1 Various79- 100.5
Falling Head - 0.1 - 1.8 17,250 65.08(Av.) 5 zones tested VSHI drilled with Cable Tool
Rig
aquifer
aquifer
aquifer
aquifer
completed
H29C 94.6-101.6 Airlift - 14700 65.12
H34 90.0-93.0 Airlift 0.3 - 4090 56.27
H35 90.0-93.0 Airlift 0.04 - 4443 56.31
H38 87.8-90.3 Airlift - 3585 NA
H39 88.0-91.0 Airlift 0.015 - 3280 NA
H42 89.0-92.0 Airlift 0.2 - 4170 55.75
Impossible to analyze due to slow recovery and
interference from other works
Notes: * This analysis may be incorrect, as its SO4-- value is anomalously low and the piezometer is reported not to be in communication with an aquifer.
** Metres below ground level NA Not available C&H Coffey and Hollingsworth
Source : Armstrong(1998)
Drilling by Heathgate has included the installation of several new observation wells in the Willawortina Formation. The location of these wells is shown in Figure 3. Water level trends for the wells monitoring the Willawortina Formation are shown in Appendix 1. Figure 13 shows computer drawn water level contours for this aquifer (wells that have been screened above the Namba Formation have been considered to be representative of the Willawortina Formation). The inferred flow direction is towards the south-east with a steeper gradient at North Beverley compared to Central and South Beverley.
In the immediate vicinity of Beverley water level fluctuations (Appendix 1) are variable with time associated with recharge to the uppermost permeable zone. The highest fluctuations are typically observed along the major creeks to the north and south of the deposit.
Figure 13: Willawortina Formation Local Water Levels (m AHD) – July 2006
3 BEVERLEY PALAEOCHANNELS
3.1 Palaeochannels Geometry
Extensive exploratory drilling, carried out since the opening of the Beverley Uranium Mine has revealed a series of sand lenses, most of which appear to occupy depressions in the surface of the Alpha Mudstone and in similar positions with respect to the Beta and Gamma Mudstones lying deeper in the sequence. These “channels” are thought to be the expression of a series of fluvio-lacustrine sedimentary cycles within the region. Each cycle is interpreted at present to have been deposited during a single rise and fall of lake level in the proto-Lake Frome, in response to climatic fluctuations. Together they comprise the depositional system responsible for the sedimentary and facies architecture of the Beverley Region.
The nomenclature at the Beverley Mine has been extended in order to accommodate this new concept, and the stratigraphy now comprises the Beverley, Alpha, Beta, Gamma and Delta Sequences. The Alpha Sequence corresponds to the regionally distinctive horizon referred to by previous authors as the Alpha Mudstone (or Lower Member), occurring immediately beneath the main mineralised horizon at Beverley.
In addition to the originally described North, Central and South Beverley sand lenses that were originally thought to be separate bodies of sand but are now understood to be to some degree hydraulically interconnected, the following sand bodies have been delineated:
Northeast Beverley – extending from close to MW013 to the current ML boundary where it is monitored by MW046 to MW050.
Beverley East – extending from the east side of the Central Beverley sand body in a direction slightly east of southeast then swinging towards the south and again to the south east outside the current ML boundary. This sand body is identifiable as the Central Channel in the EIS (Figure 14).
Deep South – two trends have been recognised beyond the southern ML boundary,
Russell trend aligned approximately with South Beverley; and
Poonatana Trend associated with the upthrown side of the Poontana Fault
Figure 5 shows the locations of a series of cross sections of the newly discovered sand bodies with section A - A’ showing the eastern edge of the Central Ore Zone, B – B’ and C – C’ illustrating the distribution of sands in Beverley East. The Beta Sand is well developed in section B – B’ and two of the drillholes have been extended into the Gamma Sand on section C – C’.
Sections D – D’, E – E’ and F – F’ illustrate the sand distribution in the Deep South area. The full sequence from Beverley Sand down to Delta Mudstone is penetrated by one hole in section D – D’.
The whole sequence is seen in section E – E’ where, beneath the Gamma sequence is a calcareous unit named the Lower Namba Carbonate which overlies what has been tentatively identified as Cretaceous (undifferentiated). The considerable depth of sediments penetrated by this section necessitated the representation of each cyclic depositional sequence (Beverley, Alpha, Beta and Gamma) as a single unit, which include the upper mudstone and lower sand components.
Section F – F’ includes the Poontana Fault which has a vertical displacement of the order of 70 m at this locality.
All sections show the stratigraphy but do not attempt to describe the detailed facies changes, which are likely to play an important role in the control of fluid movement during ISL mining.
From the hydrogeological point of view the lateral limits of the "active" channels may be either:
The steep sloping surface of the Alpha (or other) Mudstone where the channel is deeply incised;
The facies change from active stream sediments dominated by sand to overbank sediments dominated by clays and silts; or,
The lateral limits of the mineralised sand body where it abuts against older channel sediments in the channel-within-channel sequence.
From the observed hydraulic behaviour of the channel aquifers both during pumping tests and in response to mining to date, it appears that any of the above are effective lateral constraints which restrict groundwater flow normal to the channel axis.
Figure 14: Location of Poontana Fault Zone
(refer to EIS for the Beverley Deposit Stratigraphic Cross Sections, Figure 6.5)
PO O
N TA
N A
U D
Drill Holes
Resource Outlines
3.2 Faulting Near the Beverley Palaeochannels
The position of the Poontana Fault zone is shown in Figure 5 and 14. The cross sections show the structure to be a high-angle fault. This faulting appears to have been active during channel deposition and displaces the Namba Formation down to the west by a combined total of up to 70 m, passing through a probable 100 m of Alpha Mudstone beneath the level of the channel sands.
Movement along a fault in highly clay-rich sediments such as the Alpha Mudstone leads to shearing and "smearing" of the clays on the fault surfaces resulting in an impermeable fault fill.
The persistence of the large pressure difference between the Cadna-Owie Formation (GAB) aquifer and the channel sands at Beverley confirms that faulting in the Alpha Mudstone does not offer a permeable connection. Any significant permeability in the fault zones would:
Permit pressures to equilibrate between the two aquifers; and,
Result in the water quality in the channel sands being close to that in the GAB aquifer.
Field observations of pressure and water quality indicate that neither of these situations has developed.
3.3 The Beverley Palaeochannels
The sands within the channel sequences at Beverley are highly permeable (Table 4). There is a directional contrast in permeability with values observed in pumping tests along the channel being higher by a factor of at least 1.5, than those across it. This reflects the depositional environment similar to that of a braided stream.
At the channel edges the sands pinch out against the channel bank or pass laterally into lower permeability facies.
Pumping tests conducted on partially penetrating wells show a small degree of hydraulic leakage. This is interpreted to be largely intra-formational within the Beverley Sands and to be due to some communication between lenses of sand which represents a series of channels-within-channels, frequently fringed by thin clay / silt units.
The underlying Alpha Mudstone and the capping clay above the channel sands are judged to be capable of providing a high degree of confinement for the Beverley Sands and each mudstone/sands sequence in the vertical section appears to have similar properties except where a younger sand has been deposited in an erosional feature directly on top of or alongside an older sand.
Leakage through old exploration boreholes has been suggested as a possible breach of the integrity of the overlying clays. Leakage of this type was not noticed in any of the earlier pumping tests, which were designed to obtain data on the major aquifer properties within the ore zone. Additional pumping tests carried out in August and September 1997 were specifically designed to detect such leakage. These tests indicate that, in the Northern and Central areas of the deposit, the capping clay is intact despite the fact that the pumping wells and piezometers were located within a few metres of old exploration holes.
More recent testing has confirmed the overall “tightness” of the channel sand sequences.
A pumping test was carried out in April 2006 (Table 6) to assess the degree of connection between the North East sand lens, the Alpha Sand unit and the main North Beverley Orezone.
The North East lens was found to be very poorly connected to the main ore zone and the general response was typical of that of a fully bounded aquifer. There was found to be sufficient connection at the test site, between the Alpha Sand and the North east sand for the former to be regarded as being part of the Namba Aquifer sequence for purposes of water balance calculation.
Current experience of the behaviour of the aquifer system shows that whilst the drawdown response during pumping is rapid, recovery is extremely slow and typical of a system, which is almost completely sealed from outside sources of water. Any attempt at constructing a conceptual model of the present day flow system in its natural state must take into account the fact that the palaeochannel sediments are hydraulically almost completely isolated from seasonal and other changes occurring elsewhere in the system.
Groundwater quality at various sampling points over the Beverley Retention Leases show variations from 3,000 to 15,000 mg/L (ppm) TDS. There is currently no evidence to demonstrate the existence of vertical stratification at individual sites within the Beverley sand aquifer system. However, it is likely that semi-regional scale salinity zoning is present due to historic interaction between water in the channel and brines developed near the evaporative sink of Lake Frome.
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Table 5: North East Pumping Test Results
3.4 Confining Beds for Mineralised Zones
There are two degrees of vertical confinement of the mineralised zones:
Beverley Clay and Alpha Mudstone, above and below the mineralised Beverley sands; and,
Intra-formational clayey horizons within the Beverley Sands, which provide localised confinement.
as well as lateral confinement due to facies changes from sand to silt/clay within the same stratigraphic horizon.
3.4.1 Beverley Clay and Alpha Mudstone Confinement
The degree of confinement provided naturally by the Beverley Clay and Alpha, Beta and Gamma Mudstone units is very high. They are thick, highly plastic clays, which are continuous over areas much larger than the extent of the mineralisation. While logging of cores in these units’ records some fissured horizons corresponding to heavily over- consolidated weathered layers, the majority of the clay is massive. In the presence of free water the fissured clays would be expected to swell in the same manner as the Hindmarsh Clay of the Adelaide Metropolitan area.
The extremely low permeability of the Alpha and other underlying Mudstones, and therefore high degree of confinement afforded by it, is indicated by the very large vertical hydraulic gradient across the unit. The static head in the Cadna-Owie Formation at GAB#3 Bore is approximately 86 mAHD compared with 17.7 mAHD in the Upper Namba Formation in the Beverley Palaeochannel, a head difference of 68.3 m over a vertical distance of over 200 m.
If the Alpha Mudstone sequence were even moderately permeable, there would be prolific vertical flow into the channel sands from below. In such circumstances, the salinity of the water in the channel sands would be very close to that of the Cadna-Owie Formation, not up to 5 times more saline as it is towards the southern end of the mineralised channel.
The Beverley clay layer has been perforated by prior drilling activities and the boreholes were not back-filled to modern standards. A series of pumping tests, some of which were designed to test whether communication can be observed between the Beverley Sands and the lowermost Willawortina Formation aquifer zone demonstrated that no such communication could be detected.
3.4.2 Intra-formational Confinement
Within the Beverley Sands are numerous clay, sandy clay or silty clay horizons, which range from thin laminae to thick beds. These have been noted in all geophysical logs and cores. Individually they have confining or semi-confining properties. Collectively, these layers provide a high degree of confinement. The closely spaced drilling has shown that these can be of limited lateral extent. They have nonetheless provided sufficient confinement to restrict the fluids to the zones within which they are circulated, during mining. Pressure differences are readily transmitted through these minor aquitards but they exhibit a sufficient permeability contrast with aquifer sands to contain the mining fluids, unless excessively high pressures (in excess of the fracture pressure) are used.
Although drilling has not intersected any high angle confining beds within the channels, the pumping test data indicate that such low permeability zones must be present at the edges of the mineralised sand zones in order to create the degree of lateral constraint observed in the pumping test data. These data indicate strip widths of 170 m at North Beverley and up to 275 m at Central. These values compare with total width of channel sand of 350 m at the North site and 500 m at the Central site. The hydraulic behaviour suggests therefore that the pumped aquifer extends over only approximately half of the full width of the sands although the calculated widths can only be regarded as approximate owing to the many complexities present in the tested aquifer geometry.
Operational experience has shown that monitor wells in the Central Beverley area responded slowly and in a much-muted mode, to fluctuations in pressure induced by mining in the North Beverley mining zone. Figure 15 shows the responses in North Beverley and Central/South Beverley with the latter areas responding slightly up to the commencement of mining in Central in October 2003 then directly responding to mining activity in Central Beverley. North Beverley responses in 2004/5/6 tend to be dominated by pressure fluctuations associated with operation of the disposal well. South Beverley monitor wells respond in a similar fashion to Central indicating a high degree of connection between Central and South although during pumping tests, a well defined change in slope of the distance-drawdown plot occurs between Central and South Beverley suggesting a change in hydraulic properties sufficient to influence flow between the two zones.
The lateral confining effect of facies change is illustrated in Figure 16 which shows the response of a monitor well CMW017, completed in silt adjacent to the Central Beverley Sand compared with a long term monitor well RM7 during mining activity at Central. Two points can be made:
The water level in the “silt” well has not recovered to “normal” Beverley (Namba) levels after drilling and
Responses do not appear to be related to pressure fluctuations in the sands.
No pumping tests have been carried out in the Deep South area therefore the degree of confinement cannot be categorically defined. However, the similarity of lithologies and facies changes implies that a similar situation should prevail in this area as applies to the already developed parts of the Beverley Channel Sequence.
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4 REGIONAL AND DISTRICT GROUNDWATER QUALITY
4.1 Regional Groundwater Quality Data Sources
Data on regional groundwater quality, including recent sampling and analysis, is described in detail in Armstrong (1998). Currently available stock and domestic bores within an area extending 20 km to the north, east and west, and 30 km to the south, were sampled to provide baseline hydrochemical data for regional groundwater quality. The information obtained will certainly have an unavoidable bias towards the better end of the water quality scale since early bores which intersected water of unusable quality tended to be abandoned on completion and their salinity and location lost.
Water samples collected during the current phase were analysed for the standard suite of major ions, trace elements and radionuclides.
4.2 Groundwater Quality in the "Shallow" Aquifer of the Flinders Ranges and Plains
The range of salinity found in the fractured rock aquifers can be seen in Figure 17 showing the results for 36 samples from the regional historic database ranked in order of increasing salinity. The range, essentially from 600 to 3,000 mg/L, extends well into the stock water range. This is appropriate since many of the bores are used exclusively for stock watering.
Close to the Flinders Ranges the shallow aquifer is the outwash fan material of the Willawortina Formation, but, further to the east of Beverley the shallowest water intersections may be in Namba Formation or Recent alluvium.
The salinity range in the Willawortina Formation is shown in Figure 18 to extend from less than 1000 mg/L to more than 20000 mg/L indicating that fresh water, recharged by streambed infiltration during storm events, is subjected to evaporative concentration and may also be acquiring some additional salinity by mixing with saline waters near Lake Frome.
The plot of salinity versus depth for the Willawortina Formation waters (Figure 19) shows no correlation between the two parameters, which is ascribed to the fact that evaporative processes are acting on the shallower groundwaters leading to increase in salinity independent of depth.
Figure 17: Regional Salinity Data for Hard Rock Aquifers
0
1,000
2,000
3,000
4,000
5,000
6,000
TDS (mg/L)
Figure 18: Regional Salinity Data for the Willawortina Formation
0
5,000
10,000
15,000
20,000
25,000
TDS (mg/L)
Figure 19: Regional Variation in Groundwater Salinity with Depth, Willawortina Formation
0
20
40
60
80
100
120
140
160
SALINITY (mg/L)
DEPTH (m)
4.3 Groundwater Quality in the Great Artesian Basin (GAB) Aquifer
Analytical data for five GAB bores is given in Table 6. Moolawatana Bore #2, and the two Cootabarlow bores are located to the east of the northern end of Lake Frome and Camp Bore (also known as 4 Mile Flowing Bore) lies just to the west of the Beverley Retention Leases boundary and GAB#3, completed in August 1999, is adjacent to the Plant on the Mining lease.
The thickness of Lower Namba Formation plus Bulldog Shale, between the Beverley Sands and the GAB aquifer in the recently drilled GAB#3 is 194 m.
The three eastern bores all have high levels of bicarbonate typical of GAB waters originating from the north and east whilst Camp Bore and GAB#3 have higher calcium and magnesium with less than half of the bicarbonate content of the eastern bores and lower pH. This is interpreted to be the result of recharge from the hard rock aquifers of the Flinders Ranges to the Cadna-Owie sandstones at the western margin of the sub-basin. The presence of radionuclides in Camp Bore water further supports a contribution to its make up from the Flinders Ranges.
Table 6: Water Quality in GAB Bores
HOLE OR SAMPLE ID Moolawatana Bore 2
Cootabarlow Bore 1
Cootabarlow Bore 3
DEPTH (m) 437 437 419 312 Screen 336 to 360m
pH (pH Units)
8.1 7.3 7.2
CATIONS
CALCIUM (mg/L) 5 8.6 7.1 38.8 31.6
MAGNESIUM (mg/L) 2 2.9 4.3 12.9 12.3
SODIUM (mg/L) 670 663 690 745 773 POTASSIUM (mg/L) 6 28.5 25.2
ANIONS
RADIONUCLIDES
4.4 Groundwater Quality in the Baseline Study Area
The distribution of salinity within the baseline study area is presented in Figure 20 illustrating the tendency for salinity to increase towards the east.
Many of the lower salinity waters are immature with bicarbonate present in a similar milli- equivalents/litre range as the other major ions, with the exception of sulphate. The more saline waters are of Na-Cl-HCO3 type indicating a moderate residence time.
The distribution of pH in the baseline study area database samples is given in Figure 21. All but one (Pepegoona Well and Spring pH 5.8) are slightly alkaline which is consistent with the generally high levels of bicarbonate.
The range of uranium content exhibited by the "shallow aquifer" water samples in the regional database, which includes both Proterozoic rocks of the Flinders Ranges and the shallow aquifers of the foothills and plains is illustrated in Figure 22. It can be seen to extend from zero to in excess of 300 micrograms/L. The spatial distribution of these values is given in Figure 23, from which it can be seen that uranium concentration tends to increase towards the west reaching a maximum of 310 ug/L.
Radium (Figure 24) reaches a maximum value in this sample set of 178.7 Bq/L at Camp Bore (GAB) and elsewhere is less than 20 Bq/L with values to the west dropping to below 1 Bq/L. The high radium reported from Camp Bore in these past samples is not supported by current sampling for which the radium value is 0.44 Bq/L.
Radon distribution (Figure 25) shows one high value at Paralana Springs, which is well known as a radon anomaly.
Figure 20: Groundwater Salinity Distribution, Baseline Study Area
kilometres
360000m E
370000m E
380000m E
Paralana House Bore (2200)
Wooltana Bore 38 (950)
Pepegoona Well & Spring (3000)
Speculation Well & Spring (1900)
Figure 21: Groundwater pH Distribution, Baseline Study Area
kilometres
Figure 22: Uranium in Baseline Study Area Shallow Aquifer Water Samples
0
50
100
150
200
250
300
350
URANIUM (microgm/L)
Figure 23: Distribution of Uranium Concentrations in Baseline Study Area Shallow Aquifers
kilometres
Figure 24: Distribution of Radium Concentrations in Baseline Study Area Shallow Aquifers
kilometres
Figure 25: Distribution of Radon Concentrations in Baseline Study Area Shallow Aquifers
kilometres
4.5 Groundwater Quality in Beverley Site Aquifers
4.5.1 Willawortina Formation
Water quality immediately overlying the Beverley aquifer, within the Willawortina Formation, has been routinely sampled. Field parameters electrical conductivity (EC), pH and sulphate have been collected. Temporal water quality trends for regulatory compliance monitoring locations (located within the current mine lease), intersecting the Willawortina Formation, are shown in Appendix 2.
Figure 26 shows the local EC observations (and averages) at monitoring wells intersecting the Willawortina Formaltion. Spatially the water quality in the Willawortina Formation is variable, with average values of EC ranging from 3 mS/cm to 20 mS/cm, where it overlies the Beverley Deposit. Figure 26 shows a continuous trend from north to south of increasing salinity, similar to the trend observed for wells intersecting the Namba Formation but with some evidence for localised changes in conductivity possibly associated with recharge from surface drainage lines. Temporal EC trends (Appendix 2) suggest little variability of EC over time.
Figure 26: Willawortina Formation Local Electrical Conductivity Observations (mS/cm)
4.5.2 Namba Formation
Routine water sampling from the Namba Formation has been carried out with the collection of field parameters, electrical conductivity (EC), pH and sulphate. Temporal water quality trends for regulatory compliance monitoring locations (located within the current mine lease), intersecting the Namba Formation, are shown in Appendix 2. The wells sampled include samples collected from wells intersecting:
The Beverley sands;
The low permeability silt-clay sediments along the margins of the channel sands; and
The Alpha sediments.
Figure 27 shows the local EC observations at monitoring wells intersecting the Beverley Formation (at monitoring locations screening both the mineralised sands and surrounding low permeability silt-clay sediment) and Alpha Sediments. Figure 27 shows two groups of EC observations, with North Beverley having ECs generally less than 10 mS/cm and Central and South Beverley falling in the 10 to 20 mS/cm range. The data suggests a continuous trend from north to south of increasing EC in the channel sediments. The two wells intersecting the Alpha Sediments have recorded similar EC to near by Beverley locations. Temporal EC trends (Appendix 2) suggest little variability of EC over time.
There is currently no evidence that the Beverley Sands is stratified with respect to water quality at any specific site. The semi-regional scale distribution of salinity within the sand can possibly be accounted for on the basis of an historic interaction between water in the channel sands and brines associated with an evaporative sink near the site of the present day Lake Frome. This in turn has lead to the establishment of a saline plume maintained in position by the density contrast between brine and fresher channel water. An alternative interpretation of the salinity distribution requires historic flow within the channel sands, (although present day gradients indicate that the aquifers are stagnant), at a low rate and originating to the north and east. This infusion of fresher water could have originated as recharge to the Willawortina Formation leading to much higher water levels and some vertical leakage, or throughflow from basement. The flow rate must have been small and duration relatively short since the brackish to saline waters in the channel sands have not been totally displaced.
Uranium concentrations encountered in the water samples from within the Namba Formation are typically less than detection.
Figure 27: Beverley Formation Local Electrical Conductivity Observations (mS/cm), July 2006
4.6 Radionuclides in Potential Water Supplies
Water resources within approximately 15 km of the Beverley deposit comprise supplies from the GAB at Camp Bore and GAB#3, the Willawortina Formation along the major creeks, and surface supplies, of which some are permanent. Some of these waters have significant levels of radionuclides. The radionuclide levels in regional stock bores, already listed in Table 2 exceed drinking water standards for uranium (0.02 mg/L) but are below the 0.5 Bq/L radium permissible under current National Health and Medical Research Council guidelines (NHMRC and Agriculture and Resource Management Council of Australia and New Zealand, 1996). Radionuclides in surface waters (Table 8) exceed drinking water standards for both uranium and radon. Levels of radionuclides are within
acceptable limits for their present use as stock waters, with the notable exception of Paralana Hot Springs.
Table 7: Radionuclides in Surface Waters
LOCALITY TDS (mg/L) U (ug /L) 226 Ra (Bq /L) 222 Rn (Bq /L)
Black Spring 1,300 62 0.06 122
East Painter Creek ? 21 0.02 12
Four Mile Creek 1,500 197 0.06 17
Munyallina Creek 1,400 4 0.02 6
Pepegoona Well & Spring 2,700 16(Av 3) 0.14(Av 3) 12
Spring North of Paralana 4,100 253 0.07 Nd
Stubbs Water Hole ? 14 0.03 Nd
Terrapinna Water Hole 6,700 52(Av 3) 27(Av 3) 0.3(av 2)
Unnamed Creek (4.5km North of Four Mile Creek)
700 17 0.09 17
AVERAGES (No. of samples) 102(11) 0.05(11) 23(8)
Paralana Hot Springs
Pool Water 115 14 1800
17 2081
5 GROUNDWATER FLOW, INTERCHANGE AND DISCHARGE
5.1 Regional Patterns
Figure 28 shows the original conceptual regional groundwater flow model. The highest heads, found to the west in the Flinders Ranges drives the hydraulic system. Springs at the range front, such as Paralana Hot Springs, discharge at approximately 100m AHD. These Proterozoic fractured rock aquifers recharge the sedimentary aquifers of the Frome Embayment, including the GAB aquifer. In addition, the Cadna-Owie Formation aquifer west of Lake Frome receives a component of recharge from the north, which cannot be depicted on the east-west section of Figure 28. Further to the east, near Lake Frome, the flow in the GAB is from the east and north and there are discharges of GAB waters at mound springs and flowing bores along the eastern edge of the lake and flowing bores further to the east. The location of the groundwater divide cannot be precisely determined from the sparse data for the GAB system. However, the conceptual modelling of Diaconu indicates that the lowest part of the piezometric surface is controlled by discharge from the flowing bores and springs on the eastern side of Lake Frome. Lake Frome is the regional groundwater sink with a minimum surface elevation of approximately 5 m below sea level.
Overlying aquifers may be recharged from the Cadna-Owie Formation via faults (where brittle lithologies are present on both sides of a fault plane) and slow seepage upwards from the pressurised GAB system, a process that is limited by the permeability and thickness of the aquitards and the driving head difference.
To the south and east of Beverley, where the Eyre Formation lies directly on Proterozoic rocks, it too would be recharged from these underlying fractured rocks, as well as receiving contributions from the Cadna-Owie Formation. The potentiometric surface in the Eyre Formation regionally declines towards Lake Frome, although no data exists west of the lake to demonstrate this in the Beverley region.
The other major source of recharge (available to the highest aquifer in the sequence) is direct infiltration from rainfall and streambed infiltration. In a semi-arid climate, streambed infiltration can be expected to be dominant. The Willawortina Formation aquifer (including in this discussion the post-Pleistocene stream bed deposits incised into it) is the source of good stock quality water where it is tapped along the banks of the creek channels. The potentiometric surface is closer to the surface in the numerous wells drilled into it than is the case in the interfluvial areas, such as at Beverley. The overall potentiometric pattern suggests a net movement of groundwater in the Willawortina Formation towards the east and Lake Frome. Locally, the flow is away from the influent creek beds and along the watercourses in the underlying sediments.
The Namba Formation, where it includes an aquifer locally at Beverley, lies beneath the Willawortina Formation and above the Cadna-Owie Formation (and above the Eyre
Formation, if it is present). Recharge to the palaeochannel aquifers from above and below appears to be minimal within the lease area for the reasons given below.
During major rainfall events resulting in flow in the surface watercourses (eg. Four Mile Creek), infiltration through the streambed may give rise to a localised recharge mound in the uppermost permeable interval. This mound appears to dissipate with time but contributes to the resource of better quality water stored in the shallow aquifer (streambed sands and gravels/shallow Willawortina Formation beneath the drainage lines.
Figure 28: Regional Groundwater Flows
Source: Prepared from J Higgins investigations by JLC Exploration Services June 2007
Please note that there is strong vertical exaggeration of about 30:1
5.2 Beverley Aquifers
The data at Beverley shows that there is a difference of up to 1.5 m in hydrostatic head between the Namba Formation and the deepest permeable zone in the Willawortina Formation at the Central FLT site, 0.5 m at the North FLT site and a negligible horizontal gradient within the channel sands. A similar situation exists throughout the channel as indicated by the results of a recent review of the water levels obtained after long periods of rest.
It is evident from water level monitoring during current FLT operations, that disturbances to the water balance in the channel take a long time to recover. Therefore, much of what were considered to be static water levels in earlier reports are now considered to have been subject to disturbance prior to measurement.
The water in the channel sands is considered to be close to stagnant under the present day natural hydrologic regime.
The Willawortina potentiometric surface over much of the Beverley area is up to 1.5 m higher than that of the Namba Formation aquifer. However, the Willawortina potentiometric surface failed to respond to up to 7 m of draw down in the upper Namba sands over 3 days of recent pumping tests. This indicates the extremely low permeability of the clay aquitard.
In addition the hydraulic gradient in the channel sands is flat, indicating negligible horizontal flow. Response to recharge in an open hydraulic system is by flow from the recharge area to the discharge area thereby requiring a horizontal hydraulic gradient.
In a bounded hydraulic system, such as the Beverley channel aquifer, the response to recharge would be an increase in potentiometric level modifying the existing vertical hydraulic gradients. The response would cease when the head in the channel was equal to the head in the overlying aquifer.
The Namba sands at North Beverley have a lower potentiometric surface than both the Willawortina aquifer above and the GAB aquifer below; thus vertical hydraulic gradients would suggest that:
Either the palaeochannel is a sink for both external aquifers, or,
The aquitards above and below the channel are resisting vertical flow.
The persistence of relatively high salinities in the channel, compared with salinities above and below, plus the absence of vertical salinity variation in the channel sands supports the hypothesis that the aquitards are effective barriers to vertical flow and thus to vertical recharge.
At Central Beverley the Willawortina Formation heads are lower than channel aquifer heads therefore any vertical movement of water would be expected to be upwards both from the underlying artesian aquifer into the Namba and from the Namba into the Willawortina Formation. The persistent high salinity of the channel aquifer at the central FLT site compared with the overlying and underlying aquifers suggests that, like the north site, it is effectively isolated by the almost impermeable Alpha Mudstone and Beverley clay.
In addition, attempts at replicating channel water compositions by theoretical mixing of Willawortina and GAB waters in any proportions using numerically based water quality modelling software failed to produce a satisfactory match. This supports the concept that the channel water originated from other than simple mixing due to leakage from the vertically adjacent aquifers.
Discharge from the Namba Formation aquifer is believed to be virtually zero since:
There is a zero hydraulic gradient;
Vertical hydraulic gradients are directed towards the channel sands from above (small gradient) and below (very large gradient); and,
The mineralised parts of the channel appear, from the recent pumping test results to be bounded to the north and south by low permeability potential flow paths and to the east and west by similar restrictions.
Any discharge originating from the Willawortina Formation aquifers would be expected to be ultimately to the south east towards the evaporative sink at Lake Frome. This is supported by the distribution of salinity in the shallow aquifers.
6 CONCEPTUAL MODEL OF THE BEVERLEY AQUIFER SYSTEM
Taking account of all hydrogeological information, including that obtained from current operations, a conceptual model has been developed for the immediate environs of the Beverley channel aquifers. The model is illustrated in Figure 29. The essential features of the conceptual model are:
The Beverley channel aquifer system is effectively sealed within an envelope of fine- grained sediments and containing water with a rest level, when undisturbed for long periods, of 17.7m AHD;
Alpha, Beta and Gamma sedimentary cycles have been included.
Bulldog Shale (Cretaceous Shale/mudstone overlying the GAB aquifer)
Internal facies changes, too small in scale to be shown in Figure 29 and thought to originate from the channel-in-channel nature of sedimentation, play a role in limiting the effective width of the ore bearing sands in the areas tested to date;
There is no hydraulic gradient within the channel sands, therefore there is no lateral flow;
Recharge to the Willawortina Formation occurs primarily along surface drainage lines during major rainfall events with lateral flow and discharge towards the regional sink of Lake Frome;
The basal permeable zone in the Willawortina Formation is represented as a continuous aquifer in the model, but it may be a series of disconnected lenticular fine sands/silts;
The Paralana Fault zone, where it displaces the Alpha Mudstone Sequence and Beverley Clay, is impermeable due to the high clay content of both lithologies. The head in the underlying artesian aquifer (GAB or Eyre Formation) is of the order of 90m AHD and vertical leakage through the Alpha Mudstone is negligible; and,
The artesian aquifer may be receiving a contribution to its chemical composition from water originating in the fractured rock environment of the Flinders Ranges.
There is neither significant recharge to, nor discharge from, the channel sands under natural conditions. During mining, experience has shown that the only horizontal flow in the channel sands will be in response to pumping and, where a bleed stream is maintained, this horizontal flow will be towards the pumping centres.
When in situ leaching is completed, the channel will return to the stagnant natural hydraulic regime by the slow recovery process which involves internal flow towards the areas of imposed draw down, with a very small component of horizontal flow from outside the boundaries of the pumped aquifers.
Figure 29: Conceptual Model in Vicinity of Beverley Channels
7 REFERENCES
Australian Groundwater Consultants Pty Ltd (1981). Beverley Project Hydrogeological Program – field methods and data presentation. Company Report, June 1981 (unpub).
Australian Groundwater Consultants Pty Ltd (1982). Beverley Uranium Project: Hydrological evaluation for assessment of in situ leaching impact for SA Uranium Corporation. Beverley Project Draft Environmental Impact Statement Supporting Document No. 2. South Australian Uranium Corporation.
Australian Groundwater Consultants Pty Ltd (1984). Beverley Project supporting document No. 11. Geology and hydrogeology implications of ISL mining. Consultant’s report to South Australian Uranium Corporation, Adelaide.
Boyd, W E (1990). Mound Springs. in Tyler, M.J., Twidale, C.R., Davies, M. and Wells, C.B. (eds) Natural History of the North East Deserts. Royal Society of South Australia Inc, Adelaide
Callen, R.A. (1975). The stratigraphy, sedimentology, and uranium deposits of Tertiary rocks: Lake Frome area, South Australia. South Australia Department of Mines Report Book 75/103.
Callen, R.A. (1975). Geological map of the Frome sheet. Department of Mines and Energy, South Australia. 1:250,000 Mapping Series. No SH 54-10.
Callen, R.A. (1977). Late Cainozoic environments of part of north eastern South Australia. Geological Society of Australia Journal 24: 151-169.
Callen, R.A. (1981a). Geology of the Beverley area, Tarkarooloo Basin. SA Department of Mines Open File 28/1/81.
Callen, R.A. (1981b). FROME, South Australia, sheet SH54-10. South Australia Geological Survey. 1:250 000 Series - Explanatory Notes. Department of Mines and Energy, Adelaide.
Coffey and Hollingsworth Pty Ltd (1973a). Beverley Prospect, SML 564, Soil and groundwater investigation. Report on Stage 1 feasibility study. Company Report (unpublished) A79/1-2. Company Report (unpubl.)
Coffey and Hollingsworth Pty Ltd (1973b). Beverley Prospect, SML. 564, soil and groundwater investigation. Report on Stage 2 Feasibility Study. Report A79/2-1. Company Report (unpubl.)
Habermehl, M.A. (1980). The Great Artesian Basin, Australia. BMR Journal of Australian Geology and Geophysics 5: 9-38.
Heathgate Resources Pty Ltd (1998). Beverley Uranium Mine. Environmental Impact Statement.
Ker, D.S. (1966). Hydrology of the Frome Embayment in South Australia. SA Department of Mines Investigation Report.
National Health and Medical Research Council and the Agriculture and Resource Management Council of Australia and New Zealand (1996). Australian drinking water guidelines 1996. NHMRC, Canberra.
.
C:\Project\fem\fem0561- beverley\reporting\ConceptualModelReportAug06\Beverley CHM Sept06 V2.doc
APPENDICES
APPENDIX 1 HYDROGRAPHS
SO UT
H BE
VE RL
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-4
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0
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0
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50
-20
-10
0
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30
0
10
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50
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0
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60
-20
-10
0
10
0
10
20
30
40
-10
0
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20
30
40
0
10
20
30
40
0
10
20
30
40
0
10
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30
40
0
10
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0
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0
10
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0
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40
60
0
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60
0
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60
0
20
40
60
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0
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40
60
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0
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60
0
5
10
15
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25
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0
20
40
60
-20
0
20
40
60
-20
0
20
40
-4
0
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8
12
16
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-4
0
4
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12
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0
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8
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-4
0
4
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0
4
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4
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0
10
20
30
40
0
20
40
60
-40
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0
20
40
60
-25
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-5
0
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0
10
0
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30
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0
10
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30
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0
0
10
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0
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0
20
40
60
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-20
-10
0
10
0
20
40
60
0
20
40
60
0
20
40
60
80
0
20
40
0
20
40
60
0
20
40
60
80
0
4
8
12
16
0
5
10
15
20
25
0
5
10
15
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25
0
5
10
15
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0
5
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25
0
5
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0
4
8
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0
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APPENDIX 2 WATER QUALITY TIME
SERIES PLOTS
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Supporting report C - Hydrogeology

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