introduction and background - coorong district … b... · demonstrate a low risk to groundwater...

‘making water work’

AUSTRALIAN GROUNDWATER TECHNOLOGIES

ABN 97 110 928 928

GPO Box 2645, ADELAIDE SA 5001

Tel: (08) 8212 5622

Fax : (08) 8231 5399

www.agwt.com.au

20/1/2017

Jim Quinn

Manager Development and Environmental Services

Coorong District Council

PO Box 399

Tailem Bend, SA, 5260

our ref: 1597-16-DAI

Dear Jim

RE: Wellington East Groundwater Desktop Study.

Please find the following groundwater desktop study for Wellington East land development. The results

demonstrate a low risk to groundwater receptors from nutrient seepages including the River Murray

channel. Groundwater is interpreted to discharge to the adjacent floodplain rather than the River itself. This

negates the need for groundwater modelling, a water balance study and detailed risk assessment.

1. INTRODUCTION AND BACKGROUND

The Coorong District Council (CDC) own land on the Highland at Wellington East. This land has been

owned since the 1800’s and is currently being released for residential development. The land parcels are

located on the eastern side of the River Murray downstream from Lock 1. Up to 223 allotments will be sold

and developed over the coming years (i.e. next 10-20 years). The allotments are situated on the highland

above the 1956 flood level. The general location and specific details on the allotments are presented in

Figures 1 and 2.

As part of the development Council have developed a community waste management system (CWMS) for

the western part of the development (Figure 2 – “finger allotments”). However most of the land parcels

incorporating the “1800’s allotments” will have on-site waste management systems. These systems will

received residential waste water including sewage and grey water. There is potential for these systems to

be converted to a CWMS once a critical mass of allotments are developed. This is expected to occur in 10-

15 years (J. Quinn, pers comm., 2017).

Given the proximity to the River Murray and Floodplain i.e. the River Murray Protection Area, the

Environmental Protection Authority (EPA) have requested that additional work be undertaken to

demonstrate that seepage from on-site waste systems will not affect water quality, in particular whether

seepage could:

Impact water quality in the River Murray.

Impact environmental receptors on the River Murray Floodplain.

Limit the availability of groundwater to 3rd party users.

This request was provided as a response to the Statement of Intent (SOI) submitted by the CDC. The EPA

response is presented in Attachment 1. To respond to the EPA the CDC engaged Australian Groundwater

Technologies to undertake a groundwater desktop study, gauge the level of risk from on-site management

systems and outline the next steps.

http://www.agwt.com.au/

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2. SCOPE OF WORK

As agreed in the proposal dated 28/11/2016, the scope of work included:

Characterising baseline groundwater conditions within 3 km of the development. This included

review of the geology, hydro-stratigraphy, groundwater levels and salinity.

If sufficient information is available develop groundwater flow paths through the generation of

groundwater elevation contours.

Construct an east-west cross section detailing the conceptual hydrogeology. This was required to

understand how aquifers on the highland interact with the floodplain, and their relationship to the

River Murray and Lower Lakes.

Discuss the level of risk to groundwater receptors from the proposed development, and if required

develop mitigation strategies.

Outline the next steps.

3. DATA REVIEW

The groundwater data review involved downloading well data within 3 km of the allotments and review of

available hydrogeological literature. The following data sources were utilised as part of the review:

Surface geology and stratigraphic descriptions available from the Department of State

Development (SARIG, 2017) and Geoscience Australia Stratigraphic database (GA, 2017).

Hydrogeological Map of the Adelaide-Barker area published by the Murray Darling Basin

Commission (1994).

Groundwater and stage river level data available on WaterConnect (DEWNR, 2017).

Various technical reports on the lower River Murray published by the EPA and Murray Darling

Basin Authority (MDBA).

Geotechnical investigations conducted at Wellington East (Coffey, 2005).

Information provided by CDC.

The results of the data review are presented below.

WELLINGTON

TAILEM BEND

JERVOIS

WELLINGTON EAST

Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS,

AeroGRID, IGN, and the GIS User Community

350000 352000 354000 356000 35800060

90

00

060

92

00

060

94

00

0

BRINKLEYTAILEM BEND

JERVOIS

WELLINGTON

Figure 1 | Site location map - Wellington East.

GDA 1994 | MGA Zone 54°0 2

Kilometres

1:40,000

Australian Groundwater Technologies does notwarrant that this documentis definitive nor free of error and does not accept liabilityfor any loss caused or arising from reliance uponinformation provided herein.

A4

Project Allottments - Wellington East

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Figure 2. Residential allotments including detail of waste management systems. Note the titles

created in the 1800’s will have on-site waste management systems (source: CDC, 2016).

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4. GEOLOGY

4.1 Surface Geology

The surface geology (Figure 3, SARIG 2017) outlines that to the west of the River Murray the surface

geology is dominated by Quaternary Rocks commonly deposited in alluvial/fluvial (river) and playa lake

environments. To the east of the River Murray the Blanchetown Clay is the dominant Highland feature, with

small sections of Murray Group Limestone outcropping near Jervois. A summary of the surface geological

units is presented in Table 1.

Table 1. Descriptions of surface geology in the general area. See Figure 1 for locations.

Map Symbol Strat Name Description

Q Unnamed undifferentiated Quaternary Rock -Pleistocene to Holocene

Quaternary Rocks -Marine to intertidal shelly sand and clay, locally calcarenited at top. Calcreted foredunes of medium to coarse-grained skeletal carbonate sand.

Qha Unnamed undifferentiated Holocene Alluvial

Alluvial/Alluvial sediments (deposited in river environments).

Qhl Unnamed undifferentiated Holocene Lacustrine

Lacustrine/ Playa sediments

TpQlb Blancetown Clay Clay, greenish grey, interbedded with thin limestone and quartz sand; Clay green grey, mottled sandy.

Ty Murray Group Limestone Limestone -Consolidated well bedded pale grey, yellow, white, cream, highly fossiliferous skeletal calcarenite, calcareous cemented quartz sandstone, bioclastic limestone interbedded with minor carbonaceous clay and silt

4.2 Sub-surface Geology

WaterConnect (DEWNR, 2017) was interrogated to obtain stratigraphic logs of the sub-surface. Of

particular interest are two stratigraphic drillholes on the banks of the Murray adjacent to the Wellington

Road Ferry crossing. A summary of these logs is presented in Table 2.

The logs report that the Coonambidgal Formation extends to > 25 m depth in the Wellington area. This unit

is of particular importance due to it’s low-permeability. Unlike other locations where the Murray River

channel is directly underlain by permeable Monoman Formation sand (e.g. the Riverland), the

Coonambidgal Formation acts as a hydraulic barrier, reducing infiltration between the River and adjacent

limestone aquifers. This is discussed further in Section 5 and presented in the Hydrogeological cross

section (Figure 9).

Lithology on the highland differs somewhat to the floodplain, as shallow sediments are dominated by wind

blown sands which are further underlain by clay and limestone. Lithology logs obtained from WaterConnect

and used in the cross section (Figure 9) are presented in Appendix 2. Coupled with interpretations from the

Adelaide-Barker Hydrogeological Map (MDBC, 1994), the Limestone units to the east of the River are

Quaternary in age (Coomandook Formation), while to the west the Murray Group Limestone is present

(Tertiary Limestone). The transition between the two Limestone units is unclear as the drillholes do not

extend to sufficient depth below the River Channel.

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Table 2. Stratigraphic logs at the Wellington Road River Crossing.

Unit Number Depth from (m)

Depth to (m)

Map Symbol

Stratigraphic name

Unit Description

6727-1105 0 45 Qhac Coonambidgal Formation

Alluvial flood plain and fan deposits, channel sands and clay playettes

45

Qam Monoman Formation

Fine to coarse sands and gravels, channel sands.

6727-1196 3.5 22.25 Qhac Coonambidgal Formation

Alluvial flood plain and fan deposits, channel sands and clay playettes

22.25

Qam Monoman Formation

Fine to coarse sands and gravels, channel sands.

6727-2460

6727-1101

6727-3921

6727-3074

6727-30736727-3072

6727-3071

6727-30706727-3069

6727-2968

6727-2882

6727-2811

6727-2810

6727-2458

6727-2461

6727-2442

6727-2441

6727-2440

6727-24336727-11976727-11966727-1190

6727-1189

6727-1187

6727-11136727-1112

6727-1111

6727-1110

6727-1105

6727-11046727-11036727-1102

6727-1100

6727-10996727-1098Q

TpQlb

Qha

Qha

water

water

Ty

Qhl

Qhl

Qhl

Ty

Qhl

Qhl

Qhl

Qhl

QhlQhl

Qhl

Qhl

Qhl

E

BH6

BH2BH8

WELLINGTON

TAILEM BEND

WELLINGTON EAST

JERVOIS

NALPA

348000 350000 352000 354000 356000 35800060

88

00

060

90

00

060

92

00

0

Figure 3 | Surface Geology and water wells within 3 km of the residential allottments. Wells labelled by unit no / well name. Generalised cross section presented as A-A'.

GDA 1994 | MGA Zone 54°0 2

Kilometres

1:40,000


A4

LegendGeotechnical wells (Coffey, 2005)

Well data within 3 km

Surface geologyQ - undifferentiated quaternary sediments

Qha - Quaternary alluvial/fluvial sediments

Qhl - lacustrine/playa clays

TpQlb - Blanchetown Clays

Ty - Murray Group Limestone

River Murray and Lower Lakes

A

A'

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5. HYDROGEOLOGY

The following section describes the hydrogeology of the area in more detail. Information has been derived

from DEWNR WaterConnect (2017) and the MDBC hydrogeological map sheet (Adelaide-Barker

Hydrogeological Map, 1994).

5.1 Groundwater salinity and yield.

Salinity can be used to infer the potential uses and value of groundwater in the general area. Groundwater

that is fresh will have a high value as it can be used for multiple purposes including drinking water, stock

and irrigation. On the other hand if groundwater is brackish (1,500-3000 mg/L) or saline (>3,000 mg/L),

uses are restricted for stock, salt tolerant irrigation (e.g. Lucerne) or for industrial purposes only.

Figure 4 provides groundwater salinity at wells within 3 km of the Project. The results demonstrate a high

level of variability, with salinities ranging between 343 mg/L (fresh) and 17,874 mg/L (saline). There is no

specific trend on the eastern side of the River, and in this area salinities show the greatest variation.

To the west of the River salinity is more consistent, reporting above 2000 mg/L to a maximum of

8,780 mg/L. This salinity range is classed as brackish to saline and is suitable for stock or industrial

purposes only.

5.1.1 MDBC Hydrogeological Mapping

The hydrogeological map for the study region (Adelaide-Barker Map Sheet – MDBC 1994) confirms that

groundwater salinities on the eastern side of the River range between 3000-7000 mg/L, with yields ranging

between 5 and 50 L/s. This corresponds with the Quaternary Limestone Aquifer, presumably the

Coomandook Formation (S Barnett pers comm., 2017). On the western side of the River salinity is mapped

between 7000-14,000 mg/L and corresponds to the Murray Group limestone. These salinities are at the

upper limits for stock (nominally 10,000 mg/L) and more suited to industrial purposes (e.g. road

maintenance). Yields are reported between 5-50 L/s (MDBC, 1994).

Generally speaking mapping undertaken by MDBC is consistent with findings from Figure 4, and

demonstrates that aquifers are brackish to saline. Some wells report fresh water, but it is not clear if they

remain fresh as they were drilled in the 1950’s / 1960’s and may now be saline.

5.2 Depth to groundwater (m below ground level).

Depth to water provides an indication of how close groundwater levels are to the land surface. This

information can be used to infer how seepage (if any) from on-site waste systems could influence or modify

the water table over time.

Figure 5 displays depth to water at available water wells within 3 km of the Project Site. The results confirm

that groundwater generally resides within 10 m of the land surface, with groundwater on the Floodplain

(immediately west of the allotments) very shallow, ranging between 0.29 and 1.1 m below ground.

Groundwater to the east of the site is generally higher and is reported up to 18.6 m below ground level. The

deeper groundwater at these locations is likely a reflection of ground elevation (being on the highland),

although pumping from stock wells could also be a factor (thereby lowering groundwater levels).

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5.3 Groundwater Elevations (m Australian Height Datum) and flow direction.

Groundwater elevations referenced to a common datum are important for interpreting groundwater flow

direction. Groundwater levels need to be referenced to metres Australian height datum (mAHD) so water

levels can be compared “like for like”. Once levels have been “geo-rectified” groundwater flow paths can be

broadly predicted. This is because groundwater moves from high groundwater elevation to low groundwater

elevation.

Available groundwater elevations (mAHD) were obtained from WaterConnect (DEWNR, 2017), while

geotechnical holes drilled by Coffey (2005) were referenced to mAHD using the Geoscience Australia

digital elevation model (GA, 2011). The spatial distribution of these levels is presented in Figure 7.

The results demonstrate that groundwater elevations (mAHD) are highest in the Highland areas reporting

between 0.8 and 13.30 mAHD, while groundwater elevations are lowest in the floodplain immediately west

of the Project (reported at -0.8 mAHD). Levels below the floodplain are particularly interesting as elevations

are reported below sea level. The suggest potential for groundwater discharge to the floodplain (see further

discussion below).

5.4 Stage River Levels below Lock 1.

Stage River levels below Lock 1 were obtained from WaterConnect from real-time monitoring station

(A4261159). The results over the period 2012-2016 demonstrate that River levels vary seasonally with flow,

but generally range between 0.15 and 1.5 m AHD (Figure 7). The only exception is the late 2000’s

(Figure 8) when River levels dropped to below sea level (< 0 mAHD). This is attributed to the hydrological

drought caused by widespread rainfall reduction in upstream catchments. Also to note on Figure 8 is the

red line which indicates the 0.4 mAHD River level. This is the level required to enable irrigation from the

Murray and Lower Lakes (Moseley et al., 2013).

5.5 Implications of Groundwater Elevations and Stage River levels for groundwater seepage.

The findings from Section 5.3 and 5.4 have relevance for the residential development. Groundwater and

River elevations confirm that groundwater moves from the highland and discharge to the floodplain. The

results also confirm that flows are likely to move from the River to the floodplain. Thus the floodplain

adjacent residential allotments is a “groundwater sink” and would capture any seepages derived from the

development. This would avoid potential water quality impacts from nutrient waste or discharge to the River

created by mounding.

The only exception to this would be in periods of exceptionally low River flow where channels levels

dropped below 0 mAHD. In extreme cases such as this groundwater may have potential to discharge to the

River, although this would need to occur through very low permeability Coonambidgal Clay and would

occur at a very slow rate (See section 6).

.

974605

643343

871

7405

7144

7144

21431191

2188

2870

2052

3684

27161043

5880

18388780

4883

7970

50704404

16401345

1787417850

WELLINGTON

TAILEM BEND

WELLINGTON EAST

JERVOIS

350000 352000 354000 35600060

88

00

060

90

00

060

92

00

0

Figure 4 | Groundwater salinity (mg/L) at nearby water wells. Wells without salinity have been filtered out.

GDA 1994 | MGA Zone 54°0 1

Kilometres

1:33,840


A4

LegendWater Wells labelled by salinity



!(

!(!(

!(

5

5.3

1.1

13

6.5

7.1

5.2

0.630.43

0.85

0.29

0.831.37

0.67

0.91

2.44

8.71

6.095.49

1.982.03

16.4518.59

17.0717.07

17.6716.74

WELLINGTON

TAILEM BEND

WELLINGTON EAST

JERVOIS

350000 352000 354000 35600060

88

00

060

90

00

060

92

00

0

Figure 5 | Depth to water at available wells (m bgl).

GDA 1994 | MGA Zone 54°0 1

Kilometres

1:33,858


A4

Legend!( Geotechnical wells (Coffey, 2005)

Depth to water (mbgl)



3

1

-1

-0.8

5

2.3

0.78

0.06

0.03

0.790.52

4.28

3.943.58

0.88

2.092.69

13.3

0.29

13.25

WELLINGTON

TAILEM BEND

WELLINGTON EAST

JERVOIS

350000 352000 354000 35600060

88

00

060

90

00

060

92

00

0

Figure 6 | Groundwater elevations referenced to sea level (mAHD). Data derived from WaterConnect and Coffey, 2005. Land surface elevations derived from DEM, 2011.

GDA 1994 | MGA Zone 54°0 1

Kilometres

1:33,840


A4

LegendGeotechnical wells (Coffey, 2005)

Groundwater elevations (mAHD)



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Figure 7. Stage River Heights below Lock 1 (mAHD) – Station A4261159 (source: DEWNR, 2016).

Figure 8. Historical stage River Levels below Lock 1 – Station A4261159. The red line indicates the

level below which irrigation cannot occur. Source: DEWNR, as cited in Moseley et al., 2013.

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6. CONCEPTUAL HYDROGEOLOGICAL MODEL

Based on the data review a conceptual hydrogeological model has been developed for the site. This is

presented in Figure 9 and confirms:

The surface geology comprise shallow wind-blown sands while the floodplain comprise low

permeability clay (Coonambidgal Clay).

To the east and west in the Highland areas wells typically target a limestone aquifer. These rocks

are invariably covered by 5-10 m of Quaternary Sediments (sands and clays).

To the east of the River the dominant aquifer is the Quaternary Limestone (Coomandook

Formation), while to the west they target the Tertiary Murray Group Limestone.

Deep wells drilled adjacent to the River channel report thick sequences of Coonambidgal Clay. This

unit is known to be highly impermeable and locally act as an aquitard i.e. inhibit groundwater flow

between the highland areas and River channel.

Below the floodplain, Monoman Formation sands (channel sands) are noticeably absent in the

upper 20 m. This suggests that connection between the River and adjacent aquifers is limited.

Groundwater elevation are highest in the highland and lowest in the floodplain. River stage heights

are consistently above floodplain groundwater levels. This confirms potential for groundwater and

surface water to move towards the floodplain.

Levee banks have been constructed on the edge of the River to keep the channel artificially high.

Coupled with controls from Lock 1 (and barrages in the Lower Lakes) this explains why the River

Channel levels are consistently higher than the floodplain groundwater elevation. Levee Banks are

common in the lower reaches of the Murray, and support irrigation and the diary industry.

The floodplain immediately west of the development is a “groundwater sink”, driven by evaporative

discharge and concentration of salts in the upper soil profile. This is confirmed by salt scalding

seen in aerial imagery (see Figure 10).

For the above reason water from the River Murray and the highland regions immediately east is

directed to the floodplain. The shallow depth to water allows for evaporation and consistent

lowering of the water table, thereby maintaining groundwater discharge (see arrows in Figure 9).

Based on the above any seepage from the residential development is likely to discharge to the floodplain.

This immediately averts a risk to River Murray water quality should nutrient seepages be sufficiently high.

4000

Figure 9 |East-west Cross Section and conceptual hydrogeological model. Cross section line presented in Figure 3.

P:\(FAE)_Frankston_Golf_Course\Project\1469-16-FAE ASR Phase 2\Graphics

30

20

10

0

-10

-20

0 1000 2000 3000 5000

-30

-40

6000 7000

Quaternary Sand Clay Tertiary LimestoneQuaternary Limestone Bore

8000

6727-24606727-2461

BH 6

BH 8

6727-1189

Groundwater Level (mAHD)

WELLINGTON

EAST PROJECT

SITE

MAIN CHANNEL –

MURRAY RIVER

FLOODPLAIN

GROUNDWATER

ELEVATION

<0 mAHD

6727-2458

6727-2441

6727-3069

6727-3070

BH 2

LEVEE

BANK

Groundwater flow Evaporative discharge

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7. DISCUSSION

This work has been commissioned to outline baseline groundwater conditions in proximity to a residential

development at Wellington East, with the purpose to gauge the level of risk imposed by on-site waste

systems from 223 allotments.

The findings suggest that any seepage to shallow aquifers derived from the development will flow down

“hydraulic gradient” towards the River Murray, but will most likely discharge at the groundwater floodplain

adjacent to the the River, rather than to the River itself. This is because River channel levels are artificially

raised above 0.15 mAHD on a semi-permanent basis. This occurs by regulating structures including Lower

Lake barrages and levees banks constructed parallel to the River. This finding is supported by real-time

River level data, groundwater elevation data (referenced to mAHD), and aerial imagery confirming salt

scalding at the floodplain (Figure 10). By nature salt scalding within the floodplain suggests a high level of

evapotranspiration and groundwater discharge. It is also supported by geological information that confirms

that Clay beneath the Floodplain is particularly deep (>25 m for the Coonambidgal Formation). This clay

layer is of low permeability and acts to retard groundwater flow. Therefore, any seepages derived from the

development would take a long time to reach the floodplain, allowing adequate time to discharge at the

surface (prior to entering the River).

Figure 10. Salt scalding observed on the floodplain west of the development. This confirms

discharge of groundwater from shallow aquifers.

Shallow GW

discharge and

Salt scalding

Levee banks

Levee banks

Development

area with onsite

waste systems

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Nonetheless, should all the allotments be developed in the next 10 years there is potential for some

seepage to occur to shallow Quaternary aquifers (shallow sands in the upper 10 m). This would occur if

water use was sufficiently high and significant volumes were discharged to underground waste systems.

It is understood that water supply for the new allotments will utilise rainwater tanks rather than reticulated

systems. This suggests that a typical household may only use 120 kilolitres for domestic usage.

Approximately 50% of this use would be used internal to the house (bathroom, washing, drinking water)

while approximately 50% would be used for gardens (SA Water usage data as cited in Bureau of statistics,

2011). Water use internal to the house would be directed to the on-site waste system while discharge to the

ground surface for gardens would be diffuse in nature. Thus there may be potential for approximately 60

kL/annum to seep to the aquifer. This is likely an upper estimate as:

1) Residential properties will not be permanently occupied.

2) Not all properties will be developed in the next 10 years.

3) Water usage of 120 kL/annum per household is an upper estimate. Ultimately the level of usage is

dictated by size of rainwater tanks and individual water use habits.

Assuming a development level of 50% and an occupancy rate of 40%, an upper estimate of seepage would

be:

Total seepage per household = seepage/annum x occupancy rate = 60 kL x 40% = 24 kL/annum.

Assuming only 50% of allotments are developed in the next 10 years this equates to total seepage potential

of 2,676 kL/annum or 7,300 litres per day. Spread across the area (~1500 m x 500 m) these point source

seepages are very small (65 L/household/day). At the local to regional level these seepages may not be

detectable over a 10 year time frame.

7.1 Factors that could change the above assessment.

The above assessment assumes a 50% occupancy rate and water use derived from rainwater tanks only.

Should the development be fitted with reticulated Mains water and have higher occupancy rate potential for

seepage would be enhanced. Coorong District Council have indicated that on-site waste management

systems are a temporary control, and once the development reaches an occupancy threshold the intention

is to convert the entire development to a CWMS (J. Quin., pers comm., 2017). This confirms that seepages

will not occur in the long term as on-site waste systems will only be used for 10-15 years.

7.2 Need for groundwater modelling

Based on the conceptual model developed for the site it is considered that impacts to water quality will be

low and for this reason groundwater modelling or detailed seepage assessments are not required. Any

seepage from the site will be detained by the floodplain and in time be eliminated after upgrading allotments

to a CWMS.

8. CONCLUSIONS AND NEXT STEPS.

The following conclusions can be drawn from the study:

The allotments will be developed systematically over the next 10-15 years, but are unlikely to be

occupied on a full time basis.

Seepages per household are likely to be small, only averaging 24 kL/year.

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Any seepages to the groundwater system will move towards the floodplain and will not reach the

Murray due to the presence of levee banks and raised River channel levels (>0.15 mAHD

compared to groundwater elevation below floodplain of -0.8 mAHD). This suggests a low level or

risk to River water quality or aquatic ecosystems.

Groundwater in the area is brackish to saline with the nearest 3rd party well located ~1 km to the

east. Its status is unknown, however any seepages from the development are unlikely to impact

this user.

At this stage of the development the need for additional modelling does not seem warranted. As a

worst case some shallow monitoring wells could be constructed to detect groundwater level

changes. These could be used as “leading indicator wells” and if significant groundwater level

changes were detected additional work could be undertaken to gauge potential risks.

Council intends to convert on-site waste management systems to CWMS over a 10-15 year period

(J. Quinn pers comm., 2017). This will avoid ongoing seepages in the medium to long term.

Thank you for the opportunity to conduct this assessment. If you have any queries please contact the AGT

office on 8212 5622.

Regards

Paul Magarey

Senior Hydrogeologist

Australian Groundwater Technologies.

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9. REFERENCES

Barnett, S. pers comm. (2016). Personal communications Dec 2016. Principal Hydrogeologist, Department

of Environment, Water and Natural Resources.

DEWNR (2017). Groundwater Data application accessed via WaterConnect.

https://www.waterconnect.sa.gov.au/Systems/GD/Pages/default.aspx#Unit Number

MDBC (1994). Murray Darling Basin Hydrogeological Map Sheet – Adelaide-Barker. Hard copy map.

Moseley, L., Palmer., D., Mettam, P/, Cummings, C., and Leyden, E., (2011). Lower Murray Reclaimed Irrigation Area (MLRIA) Acid Drainage Project: final summary report 2013. Environmental Protection

Authority.

Quinn, J., (2017). Personal communications January 2017. Manager Development and Environmental

Services, Coorong District Council.

SARIG (2017). South Australian Resource Information Geoserver. Department of State Development.

https://sarig.pir.sa.gov.au/Map

https://sarig.pir.sa.gov.au/Map

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APPENDIX 1 – EPA COMMENTS ON COORING DISTRICT COUNCILS

STATEMENT OF INTENT.

EPA comments on the SOI

EPA is concerned that this SOI foreshadows modification of policy to enable treatment systems at

Wellington East. While it is acknowledged that the 223 allotments of approximately 2,000 square

metres were created in the 1800s, it is noted that Policy Area 10 is located within the River Murray

Protection Area (River Murray Act 2003) and the River Murray Water Protection Area (Environment Protection Act 1993). The Land is in close proximity to the River Murray flood plain. The surrounding

environment is therefore sensitive to cumulative actions affecting water quality.

The EPA supports the existing Coorong District Council Development Plan policy for Wellington

East Residential Policy Area 10 to the extent that it promotes the protection of water quality. The

existing Development Plan policy encourages:

future development to be Linked to the construction of wetlands that will play a role in

improving water quality

residential development that will be linked to the provision of adequate water and effluent

disposal infrastructure, and

connection to a community wastewater management scheme.

The EPA recommends that detailed investigations be undertaken at Wellington East to determine

the potential risk to water quality arising from envisaged development. More specifically these

investigations should model the likely nutrient and water balances for the fully developed 223

(2,000m2) allotment township and document the impacts of offsite movement of wastewater onto

the floodplain, the downslope wetlands and the River Murray.

The EPA recommends that the following investigations be included in the SOl:

Investigate the capacity of existing CWMS and mains sewer systems to ensure they are

able to manage the additional community wastewater that will result from the increased

development.

Undertake a full evaluation of onsite wastewater disposal system constraints and

capabilities (including modelling the likely nutrient and water balances) of the affected land

at Wellington East to determine if the Land is suitable for on−site disposal of wastewater.

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APPENDIX 2 – LITHOLOGY LOGS USED IN CROSS SECTION.

Sequence W to E

Unit Number / Borehole name

Ground elevation

SWL (bgl)

From depth(bgl)

To(bgl) Lithology

1 6727-1189

4.74 2.44 0 1 Topsoil

1 3.05 Sand

2 6727-3069

1.89 1.37 0 0.5 Fill

0.5 1 Sandy clay

1 1.25 Clay grey stiff clay

1.25 2 Clay grey moderately hard

2 4 Sand grey fine to medium grained quartz sand

3 6727-3070

1.62 0.83 0 0.75 Road fill

0.75 1.5 Clay grey plastic, soft

1.5 2 Clay grey green, plastic soft

2 3 Sandy clay grey green

3 4 Clayey sand grey green, clayey fine grained quartz sand

4 4.5 Clayey sand grey, clayey fine grained quartz sand

4.5 6 Clayey sand fine grained quartz sand

River Murray

4 BH8

0.3 0 0.5 Clay medium to high platicity black brown

0.5 2.2 Clay high plasticity

5 BH2

0 1.5 Sand fine to coarse Brown

1.5 2 Sandy clay low plasticity calcareous fine to coarse sand

2 3.8 SANDY CLAY medium plasticity grey brown red mottling

6 BH6

0 1.8 Sand fine to coarse light brown

1.8 2.6 Sandy gravel fine to medium angular to rounded fine to coarse white calcrete

of 22

Sequence W to E

Unit Number / Borehole name

Ground elevation

SWL (bgl)

From depth(bgl)

To(bgl) Lithology

2.6 4 Sand fine to coarse yellow.

7 6727-2458

13.6 8.1 0 0.5 Topsoil

0.5 1.1 Limestone

1.1 5.3 Clay

5.3 10 Sand

10 14.5 Sand

14.5 15.2 Clay

8 6727-2440

13 8 0 0.5 Limestone Cap

0.5 2 Soft limestone

2 9.7 Red Clay

9.7 11.9 Rubbly Limestone

11.9 12 Hard Limestone

9 6727-2441

14.3 9.3 0 1 Limestone Cap

1 6 Red Sandy clay

6 10.3 Yellow sandy clay

10.3 14 Hard Limestone

10 6727-2461

12.4 7.4 0 0.8 Hard white limestone

0.8 6 Soft Limestone, sandy with depth

6 7.5 Very soft sandy Limestone

7.5 14 Brown sandy nodular Limestone

14 14.5 Clayey Limestone

11 6727-2460

15.5 0 1.5 Top soil

1.5 1.8 Limestone

1.8 2.5 Yellow clay

2.5 5.4 Silty white limestone

5.4 6.6 Brown Clay

6.6 12.6 Brown clay ,sand

12.6 16 Grey Clay

16 17 Yellow sandy clay

17 19 Yellow fine sand(flowing)

19 24 Silty WHITE CLAY

introduction and background - coorong district … b... · demonstrate a low risk to groundwater...

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