appendix r - okolina pty ltd – hydrogeological summary

Appendix R - Okolina PTY LTD – Hydrogeological summary

The Links at Kangaroo Island

Hydrogeological Summary

March 2014

Prepared for

by

Okolina Pty Ltd March 2014

Author: Marion Santich

The Links at Kangaroo Island Hydrogeological Summary

Contents

1. Introduction ....................................................................................................... 1

2. Hydrogeology .................................................................................................... 1

2.1 Site Specific .............................................................................................................. 1

3. Groundwater use potential ............................................................................... 5

4. Recommendations for further investigations ................................................. 5

References .................................................................................................................. 7

Appendix A Drillhole summary information ............................................................ 8 Figures Figure 1 Drillhole data .................................................................................................................... 3

Figure 2 Local stratigraphic thickness ........................................................................................... 4

Figure 3 Regional surface geology ................................................................................................ 4

Figure 4 Investigative drilling sites ................................................................................................. 6


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1. Introduction

This report presents a summary of local hydrogeology to inform drilling investigations in relation to potential long term groundwater supplies for a future development, The Links (golf course and facilities) at Kangaroo Island, South Australia. Figure 1 shows the site of this development and the broader area of hydrogeological review.

The scope of work input to this report is: research and collation of available hydrogeological literature; a review of drillhole data; and the production of maps with relevant data.

2. Hydrogeology

The occurrence of groundwater for usable supplies on Kangaroo Island is dependent on site specific underlying geology. In general, the groundwater resources across the island are limited in both quantity and quality with good quality groundwater available only in short supplies.

Geologic formation distribution for Kangaroo Island has been developed from stratigraphic or hydrostratigraphic interpretations reported in South Australia’s drillhole database (Alcoe and Berens, 2012) and groundwater resources are known to reside within:

Cambrian fractured rock aquifers;

Permian glacial sediments;

Tertiary limestone and sandstone;

Consolidated Quaternary aeolianite (dune deposits); and

River alluvium.

2.1 Site Specific

In the vicinity of the development area, both the Quaternary sediments of the Bridgewater Formation and the Saint Kilda Formation have both been identified from drillhole logs from ground surface to a depth of greater than 40 m (Figure 2). None of the drillhole logs have indicated complete intersection of these formations by identifying a deeper unit (Alcoe and Berens, 2012) hence the total depth of these formations in the area is unknown.

The Bridgewater and Saint Kilda Formations consist of Quaternary sands and are often interspersed due to the nature of wind driven deposition. The Bridgewater Formation generally comprises poorly consolidated yellow pinkish-brown fine to coarse fossiliferous calcareous sand that may be locally capped by calcrete. The Saint Kilda Formation consists of


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undifferentiated marine sediment that is calcareous, fossiliferous sand and mud of intertidal sand flats, beaches and tidal marshes.

The Bridgewater Formation has been logged on site in the abandoned drillhole 6426-38 as calcareous sand and variably consolidated sandstone with fragments of limestone. The lithological log is provided in Appendix A and gives an indication of the stratigraphy to be encountered in drilling investigations.

The Bridgewater Formation is one of the main aquifers on Kangaroo Island having high permeability due to the presence of solution features in some areas. The unconsolidated sand aquifers of the Saint Kilda Formation, which intersperses the Bridgewater Formation, may also provide a groundwater source. Recharge to the unconfined aquifers occurs by infiltration and within the Bridgewater Formation the percolation through solution cavities can stratify above more saline, higher density saline water, hence variable quality, quantity and accessibility can occur in short distances.

Regional surface geology mapping (Fairclough, 2008) shows the Bridgewater Formation to be present across the site with small areas of the Saint Kilda Formation nearby (Figure 3). On the local scale these formations may be interspersed across site, with the Bridgewater Formation predominant, and are likely to be very similar in terms of groundwater salinity and yield.

Groundwater data, presented on Figure 1, shows drillholes in the site vicinity intersecting high salinity water at 12,000 to 17,000 mg/L to a depth of 40 to 60m. Yields are either undefined or very low with the deepest bore yielding less than 0.5 L/s. Summary information from drillholes in the vicinity of the development site is provided in Appendix A.

Relatively good quality groundwater of 1,000 to 3,000 mg/L has been found at shallow depth, with no yields recorded, approximately 3 km north of the site. These wells most likely access alluvium of limited groundwater supply and suitable for stock watering rather than larger water requirements.

Whilst the deeper units have not been intersected in the vicinity of the development site, regional stratigraphy indicates the Quaternary sediments along the southern coast to be directly underlain by the Cambrian basement rocks of the Kanmantoo Group. The Kanmantoo basement rocks typically have few of the joints and fractures that form fractured rock aquifers and in addition, any joints and fractures have been infilled with clayey weathering material resulting in high salinity due to mineral dissolution (Barnett and Dodds, 2000). This regional basement geology contributes to the regional high salinity with the tight and impermeable rocks acting as a barrier to recharge.

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HAYES

HAYES

MCCANN

HOG

BAY

DAVIES

CATHERS

MITC

HELL

SIMPSON

642600576, 0m, 0L/s, , 0mg/L,

642600459, 1.7m, 0L/s, , 0mg/L,

642600457, 0m, 0L/s, , 1105mg/L, 16/08/1986

642600414, 2m, 0L/s, , 1384mg/L, 20/11/1985

642600452, 2.4m, 0L/s, , 528mg/L, 18/08/1986

642600037, 0m, 0L/s, , 12280mg/L, 30/09/1948

642600453, 5.8m, 0L/s, , 2284mg/L, 16/08/1986

642600053, 3.9m, 0L/s, , 2227mg/L, 16/08/1986

642600036, 5.8m, 0L/s, , 2570mg/L, 30/09/1948

642600038, 41.45m, 0L/s, , 17136mg/L, 9/06/1960

642600396, 58m, 0.3157L/s, 17/02/1984, 12215mg/L,

211000

211000

212000

212000

213000

213000

214000

2140006027

000

6027

000

6028

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6028

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6029

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6029

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6030

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6030

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6031

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6031

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±The Links at Kangaroo Island

Drillhole Data

GDA 1994 MGA Zone 54

500 0 500 1,000250 Meters

Legend

Figure 1Data Sources:DEWNR SA Drillhole DatabaseDPTI SA Generalised Landuse Data

Land UseAGRICULTUREFORESTRYLIVESTOCKMINE_QUARRYRESERVE

RESIDENTIALRURAL_RESIDVACANT

Development site

!

DrillholesLabel: unit no., depth & date, yield & date, salinity & date

! Abandoned

! Operational! Backfilled

Status unknown


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Figure 2 Local stratigraphic thickness

Figure 3 Regional surface geology

Development site

Development site

= Bridgewater Formation Qhck = Saint Kilda Formation

Source: Alcoe & Berens, 2012 (extract Figure 5b)

Source: Fairclough, 2008 (extract)


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3. Groundwater use potential

The south coast has the thickest cover of the Bridgewater Formation, logged near Flour Cask Bay, and good quality groundwater may be found where higher recharge occurs. It is unlikely that this will be located within the development site as the lowest salinity groundwater occurs in the southwest where that highest rainfall occurs and drillhole data does supports this.

Throughout Kangaroo Island water wells predominantly have yields of less than 1 L/s, which will not accommodate the needs of high volume use. Supplies suitable to meet the demands of golf course irrigation and the related facilities will need to target brackish aquifers with higher yields of over 3 to 5 L/s and a borefield with a balancing storage will likely be required to meet desalination and distribution flow rates.

Drilling investigations will be required to confirm groundwater suitability and variability across the site in terms of salinity and yield for consideration as a desalination water supply option.

4. Recommendations for further investigations

It is recommended that:

on site drilling investigations target the Bridgewater Formation and drill into the basement rocks below to completely intersect the formation. This will allow the maximum yield and any salinity stratification to be identified. The estimated total drillhole depth is 60 metres.

the initial investigation well be located close to any identified surface storage site. A borefield connected to the balancing surface storage via a ring or individual supply mains is likely to be required to meet demand and delivery flow rates. These wells will need to be spaced around the site to avoid interference between wells and it is considered prudent to undertake investigative drilling across the site to determine yield and salinity variations.

current yield and salinity information be obtained from existing well 6426-396 if able to be accessed. This well, situated immediately northeast of the site across Davies Road, is recorded as being cased to 58 metres but has no status defined.

Indicative investigation drilling sites are located on Figure 4 and whilst potential development configurations have been considered the drilling sites should be confirmed on ground in accordance site landscape and infrastructure plans.

CATHERS

DAVIES

212000

212000

213000

213000

214000

214000

6027

000

6027

000

6028

000

6028

000

6029

000

6029

000

±The Links at Kangaroo Island

Investigation drilling sites

GDA 1994 MGA Zone 54

Data Source: Google Earth imagery

500 0 500250 MetersLegend

Development site

Figure 4

Investigation drilling sites


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References Alcoe, DW and Berens, V, 2012, Non-prescribed groundwater resources assessment – Kangaroo Island Natural Resources Management Region. Phase 1 - Literature and Data Review, DFW Technical Report 2012/02, Government of South Australia, through Department for Water, Adelaide

Barnett, SR and Dodds, AR, 2000, Groundwater resources on Kangaroo Island, Report Book PIRSA 2000/15, Government of South Australia, through Primary Industries and Resources South Australia, Adelaide

Fairclough, MC. 2008, Kingscote Special Map Sheet, South Australia Geological Survey, Geological Atlas 1:250 000 Series Sheet SI 53-16

Government of South Australia, 2014 Groundwater data https://www.waterconnect.sa.gov.au/Systems/GD/


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Appendix A Drillhole summary information


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appendix r - okolina pty ltd – hydrogeological summary

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