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REMEDIATION OF THE OFFSITES
DRAINAGE CHANNEL
FINAL VALIDATION REPORT
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TABLE OF CONTENTS
1.
INTRODUCTION ..................................................................................................................... 3
1.1
1.2
1.3
BACKGROUND .............................................................................................................. 3
OBJECTIVES ................................................................................................................. 4
SCOPE OF WORK .......................................................................................................... 4
2.
SITE DETAILS ......................................................................................................................... 5
2.1
GENERAL ..................................................................................................................... 5
3.
REMEDIATION AND VALIDATION ACTIVITIES .......................................................... 5
3.1
3.2
3.3
3.4
3.5
3.6
3.7
GENERAL ..................................................................................................................... 5
INVESTIGATION TRENCHES ............................................................................................ 5
EXCAVATION AND TRANSPORT TO THE HELIPAD .............................................................. 6
DISPOSAL OF CONTAMINATED SOIL ................................................................................ 7
VALIDATION PROGRAM .................................................................................................. 7
IMPORTATION OF BACKFILL ............................................................................................ 7
RESTORATION AND REVEGETATION ................................................................................ 7
4.
ASSESSMENT GUIDELINES................................................................................................. 8
4.1
4.2
OFFSITE DISPOSAL CRITERIA ......................................................................................... 8
VALIDATION CRITERIA ................................................................................................... 9
5.
ANALYTICAL RESULTS ....................................................................................................... 9
5.1
5.2
5.3
5.4
CONTAMINATED SOIL .................................................................................................... 9
VALIDATION SAMPLES ................................................................................................. 10
BACKFILL SAMPLES ..................................................................................................... 11
DATA QUALITY ............................................................................................................ 12
6.
DISCUSSION........................................................................................................................... 14
7.
CONCLUSION ........................................................................................................................ 14
8.
REFERENCES ........................................................................................................................ 15
9.
LIMITATIONS OF THIS REPORT ..................................................................................... 16
TABLES
Table 1. Results of soil analyses from trench samples.................................................................................... 6
Table 2. Contaminant Thresholds based on total concentration analyses only ............................................... 8
Table 3. Contaminant Thresholds based on total concentration and TCLP results ........................................ 8
Table 4. Summary of Contaminated Soil Analyses – Total Heavy Metals..................................................... 9
Table 5. Summary of Contaminated Soil Analyses – TCLP for Mercury, Lead & Nickel .......................... 10
Table 6. Summary of Contaminated Soil Analyses – Total Petroleum Hydrocarbons ................................. 10
Table 7. Summary of Validation results ....................................................................................................... 11
Table 8. Summary of CleanfillSoil Analyses – Total Heavy Metals ............................................................ 12
Table 9. Summary of backfill analyses – Total Petroleum Hydrocarbons.................................................... 12
Table 10. Summary of Quality Assurance / Quality Control Criteria........................................................... 13
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ATTACHMENTS
Attachment A
Attachment B
Attachment C
Attachment D
Attachment E
Remedial Action Plan (RAP)
Site photographs
Waste classification report
Calculation of the number of samples required from base of channel to validate the
remediation
Laboratory results, including QA / QC
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1.
INTRODUCTION
ADI Limited has commissioned several reports into the extent and degree of soil
contamination at the Mulwala facility. The most recent and most comprehensive report,
entitled “Environmental Site Assessment ADI Mulwala” URS 2001, summarised previous
studies as well as reporting on a further comprehensive sampling program. A risk assessment
was conducted on all the areas of contamination found. The Offsites Drainage Channel was
identified as an area of high lead contamination with concentrations exceeding the ANZECC /
NHMRC Environmental Investigation Levels (EIL) and the Health Investigation Levels
(HIL), consequently another report was commissioned from URS, on the management options
for the channel. This report found that the potential for the elevated concentrations of lead to
represent an unacceptable risk to human health is low. The management options canvassed by
the report were:

To do nothing

Leave the contamination in-situ and ensure that a good vegetation cover is maintained.

Capping of the soil contamination to contain it and eliminate potential surface exposure
and dust creation.

Fencing of the area to exclude access.

Excavate the contaminated soil and dispose off-site.
ADI and Department of Defence decided after consulting with the EPA and local community,
that the best long-term solution to the contamination in the Channel was to excavate the
contaminated soil and dispose off-site. This report documents the work done to remove the
contaminated soil and replace it with uncontaminated material and so leaving the site suitable
for all uses.
1.1
Background
The Drainage Channel is a open ditch approximately 2 metres wide and 1120 metres long that
was used from when the ADI facility was constructed in the 1940s until 1989 to convey
process effluent and stormwater from the Effluent Treatment Plant to the Murray River. After
1989, the flow was diverted to underground pipes. In the Effluent Treatment Plant (ETP), the
waste nitric and sulphuric acids are neutralised with lime and the resultant saturated lime /
calcium nitrate / calcium sulphate solution discharged to the river.
The drainage channel was constructed with a clay bottom and sides. Over the years the
calcium sulphate (gypsum) has changed the structure of the clay making it more porous and
allowing a proportion of the effluent to soak into the ground rather than reaching the Murray
River. The sediment on the bottom of the channel is reported as being up to 0.4 metres deep,
with the depth decreasing with distance from the start of the channel at Bayly Street.
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In the ADI facility, lead sheeting is used to protect parts of the plant from corrosion by
medium strength sulphuric acid. A very small amount of lead is dissolved by the acid and
also flows to the ETP with the waste acids. Approximately half of this dissolved lead is
precipitated out of solution when the effluent is neutralised with lime and is incorporated in
the gypsum sludge. The rest of the lead remains in solution in the effluent flowing to the
River.
Mercury was once used at the Mulwala Facility in various vacuum seals. Process upsets
caused some of this mercury to be spilt into the plant sewer system. The mercury would
slowly dissolve in the acidic plant effluent and be washed to the Effluent Treatment Plant
where it would not be removed by the lime treatment and so it would pass through and enter
the Drainage Channel. Mercury is not currently used on site.
1.2
Objectives
This validation report has been prepared by ADI Mulwala Environment Section to document
that the following objectives have been met:
1.3

Removal of soil / gypsum contaminated with lead and mercury in a safe and
environmentally acceptable manner.

Removal of a potential source of groundwater contamination in a safe and
environmentally acceptable manner.

Validation of residual soil and restoration of the area in accordance with NSW EPA,
ANZECC and ADI requirements.
Scope of work
The remediation and validation works involved the following activities:

Excavation of three trenches across the Channel and sampling from them, to determine
the depth of the contamination.

Preparation of a Remedial Action Plan (RAP) for the Drainage Channel.

Presentation of the RAP to the EPA and Corowa Council for information and comment.

Contractor supervision.

Excavation of the contaminated soil.

Transport of the contaminated soil to ADI and temporary storage on the Helipad.

Classification of the contaminated soil according to NSW EPA regulations.

Disposal of the contaminated soil.

Validation of the in-situ soil to confirm compliance with NSW EPA regulations.

Restoration of the Channel profile with clean backfill.
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
Revegetation of the Channel.
A Remedial Action Plan (RAP) was prepared to document procedures for the remediation of
the Channel and included site management procedures necessary to address environmental
and safety issues. A copy of the RAP is in Attachment A.
2.
SITE DETAILS
2.1
General
The Offsites Drainage Channel is located to the south of Bayly Street the southern boundary
of the Mulwala facility, providing a link between the facility and the Murray River. A site
plan is included as Figure 1.
The length of the channel is about 1100 metres, with a base width of about 2 metres. The
channel is tree lined for parts of its length, and had prior to the remedial works, a continuous
grass cover over the whole of the invert.
A series of photographs of the channel before and after the remedial works were undertaken,
are included in Appendix B.
3.
REMEDIATION AND VALIDATION ACTIVITIES
3.1
General
Based on the Mulwala Site Environmental Assessment conducted by URS, the lead
concentration in the surface of the base of the channel was about 300 to 600 mg/kg, which
exceeded the “Solid waste” category of the NSW EPA, unless leachate tests were done.
However, because excavation was to occur to a depth of about 0.5 metres, full sampling and
analysis to determine the disposal of the contaminated soil was left until the material was
stockpiled on the concrete Helipad.
3.2
Investigation trenches
Three trenches were dug by a backhoe on 8 August 2001 across the channel at different
locations, down to a depth at which hard clay was found. The location of these trenches is
also shown in Figure 1. Samples were taken from the sides of these trenches and analysed for
calcium, nitrates, sulphates, lead and mercury. These analytical results are shown below in
Table 1, and confirmed that the lead and mercury contamination was confined to the top layer
( < 0.3 m) and that excavation down to the heavy clay would be adequate to ensure that the
remaining soil concentrions were under the EIL levels.
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The results also indicated that it would be impractical to try and remove the nitrate
contamination because it has been washed much further into the soil, and possible into the
groundwater metres below. This meant that it would only be possible to achieve the second
objective of the plan, removal of a potential source of groundwater contamination, with
respect to lead and mercury. The soil below the drain would continue to act as a source of
contamination of nitrates and sulphates into the groundwater.
Table 1. Results of soil analyses from trench samples
Location
Depth
cm
PH
Nitrate
mg/kg
Sulphate
mg/kg
Calcium
mg/kg
Lead
mg/kg
Mercury
mg/kg
Trench 1,
30
6.7
18
2000
1400
750
1.4
80
6.2
60
1900
1600
240
3
120
4.2
60
530
610
360
0.08
30
3.8
380
3400
3000
230
0.28
60
4.2
240
450
1500
52
0.13
60
4.2
210
280
1300
47
0.13
120
4.1
180
330
850
21
0.05
40
6.7
14
5100
5900
340
0.44
60
5.6
80
3800
2100
140
0.2
100
5
160
1800
1100
130
0.05
Trench 2
Trench 3
3.3
Excavation and transport to the Helipad
Excavation and transport of the contaminated soil from the base of the channel was
done by Judd Contracting of Yarrawonga, under supervision of the Environmental
Section of ADI Limited. The material was removed from the channel using a
traxcavator which was able to reach right across the channel to scrape material from
the opposite side. The highly manoeuvrable traxcavator was able to work between
most of the trees lining the banks of the channel. Only one tree had to be removed to
allow access to the sides of the channel, although some small branches were lopped.
Trucks were usually able to park along side the traxcavator and be loaded directly
without double handling of the soil being required. The loads were tamped down by
the back of the traxcavator’s bucket to minimise any loss on the trip into ADI. No
spillages occurred during the transport to the Helipad. Access into ADI was via the
REFA gate in Bayly Street to minimise the distance to be traveled. A security guard
was stationed at this entrance during the excavation period to maintain site security.
Approximately 2400 tonne of soil were removed from the Channel and stockpiled on
the Helipad.
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3.4
Disposal of contaminated soil
The contaminated soil on the helipad was sampled by WSL Consulting, to enable
classification according to the EPA Waste criteria. Four soil samples were compiled
representing the four quadrants (North, South, East & West) of the stockpile. The
results of the analyses are set out in Section 5.1 and the classification report from
WSL is in Attachment C.
The WSL classification report was sent to Corowa Shire Environment & Planning
Engineer who, on the advice of the EPA, accepted the material for disposal at the
Corowa Shire Landfill. The stockpile of contaminated soil was transported to the
Corowa Landfill facility during the period 5/11/01 – 12/11/01.
3.5
Validation program
Samples were taken from the undisturbed soil along the base of the channel after the
contaminated soil had been removed according to the NSW EPA brochure,
“Contaminated Sites: Sampling Design Guidelines” with the minimum size hot spot to
be located with 95% confidence being 30 metres diameter. This meant that 22
samples were taken along the base of the channel at 25 metre intervals. Computation
details are included in Attachment D. As a check, using Table A in the brochure, for
the area of the channel, the minimum number of samples required is 8.
Analytical consultants, WSL, selected the exact sampling locations, took the samples,
transported them back to the laboratory in Melbourne and conducted the analyses. All
samples were analysed for calcium, sulphate, nitrates, mercury and lead using NATA
approved methodology.
During the same visit, the WSL consultant, took four samples from the stockpile of
material stored on the Helipad, and four samples of the backfill material.
3.6
Importation of backfill
Backfill material was sourced from an area at ADI Mulwala that had no history of
association with the processing plant. Prior to being placed into the channel, WSL
Consulting compiled four composite samples from the stockpile adjacent to the
channel. These samples were analysed for heavy metals, petroleum compounds and
pesticides. The results of these analyses are set out in Section 5.3.
3.7
Restoration and revegetation
The sandy soil was spread over the channel to approximately the original profile of
before the start of the remediation work. A selection of indigenous trees and grasses
were planted in and along the banks of the channel.
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4.
ASSESSMENT GUIDELINES
4.1
Offsite disposal criteria
The NSW EPA guidelines, Environmental Guidelines : Assessment, Classification,
and Management of Non-liquid Wases, July 1997, set out contaminant threshold
values for a number of waste classifications. These classifications are for “inert”,
“solid” and “industrial” waste. The guidelines also give values for leachable
concentrations (TCLP) for the three classifications.
Tables 2 and 3 summarise values for each waste classification, with regard to total
contaminant thresholds and TCLP values.
Table 2. Contaminant Thresholds based on total concentration analyses only
Mg/kg
Inert Waste
Solid Waste
Industrial
Waste
Arsenic
10
100
400
Cadium
2
20
80
Chromium (VI)
10
100
400
Lead
10
100
400
Mercury
0.4
4
16
4
40
160
Nickel
Table 3. Contaminant Thresholds based on total concentration and TCLP results
Mg/kg
Inert Waste
Solid Waste
Industrial
Waste
TCLP
conc.
Total
conc.
TCLP
conc.
Total
conc.
TCLP
conc.
Total
conc.
Arsenic
0.5
500
5.0
500
20
2000
Cadium
0.1
100
1.0
100
4
400
Chromium (VI)
0.5
1900
5
1900
20
7600
Lead
0.5
1500
5
1500
20
6000
Mercury
0.02
50
0.2
50
0.8
200
Nickel
0.2
1050
2
72
8
288
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4.2
Validation criteria
The Australian and New Zealand Environment & Conservation Council and the National
Health and Medical Research Council (ANZECC / NHMRC) Guidelines for the Assessment
and Management of Contaminated Sites, Jan. 1002, was used as the basis for assessment.
These guidelines have been set on the basis of current toxicological data and are considered
to be conservative.
In general the investigation levels are considered adequate to protect the most sensitive
receptors. Where the levels of chemcals in soils are below the ANZECC / NHMRC
guidelines, the condition of the land is considered to satisfy the requirements for protection of
all beneficial uses (except groundwater quality).
5.
ANALYTICAL RESULTS
Results of all samples were compared against the above assessment guidelines. Certificates of
laboratory results are presented in Attachment E.
5.1
Contaminated soil
Four composite samples were prepared from the stockpile of contaminated soil. The
analytical results reported elevated concentrations of lead in all four samples as detail below
in Table 4.
Table 4. Summary of Contaminated Soil Analyses – Total Heavy Metals
Mg/kg
As
Cd
Cr total
Cr(VI)
Cu
Pb
Hg
Ni
Zn
North
8
<0.2
64
<1
20
310
2.3
40
56
South
10
<0.2
76
<1
23
290
1.4
36
50
East
7
<0.2
52
<1
19
180
1.5
30
61
West
<5
0.3
110
<1
18
610
4
72
80
348
2.3
Average
Criteria *
Inert waste
10
2
10
10
0.4
4
Solid waste
100
20
100
100
4
40
Industrial waste
400
80
400
400
16
160

Contaminant Threshold Values for Waste Classification without TCLP
Subsequent to the receipt of the above results, TCLP analysis for mercury, lead and nickel
were performed on two composite samples. The results of the leachable concentration
analyses for heavy metals indicated that all samples were below the NSW “Inert Waste”
category. The report from WSL Consulting certifying this classification is in Attachment C.
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Table 5. Summary of Contaminated Soil Analyses – TCLP for Mercury, Lead & Nickel
Mg/kg
Pb
Hg
Ni
Composite A
0.23
<0.001
40
Composite B
0.45
<0.001
36
Inert waste
0.5
0.02
0.2
Solid waste
5
0.2
2
Industrial waste
20
0.8
8
Criteria *

Contaminant Threshold Values for Waste Classification with TCLP
Table 6. Summary of Contaminated Soil Analyses – Total Petroleum Hydrocarbons
Mg/kg
TPH
C6-C9
TPH
C10-C14
TPH
C15-C28
<TPH
C29-C36
North
<20
34
62
78
South
<20
33
70
63
East
<20
<20
<50
53
West
<20
24
140
200
Inert waste
650
5000 *
Solid waste
650
10000 *
Industrial waste
2600
40000 *
Criteria *

5.2
Criteria is for total C10 – C36
Validation samples
Twenty two samples were taken from the base of the channel and analysed for calcium,
sulphates, nitrate, mercury and lead. All analysis results were below the ANZECC/ NHMRC
Investigation guidelines.
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A summary of the laboratory results of the validation samples is presented in Table 7.
Table 7. Summary of Validation results
Mg/kg
Calcium
Sulphate
Nitrate
(N)
Mercury
Lead
Sample 1
1400
1000
28
0.05
50
Sample 2
740
160
260
0.15
61
Sample 3
1100
920
610
0.43
100
Sample 4
710
800
330
0.43
93
Sample 5
2200
3100
710
0.07
37
Sample 6
5300
4200
410
0.1
35
Sample 7
1000
420
120
0.17
43
Sample 8
2000
1600
140
0.12
27
Sample 9
2700
1600
360
0.22
27
Sample 10
1100
440
480
0.21
79
Sample 11
1200
560
420
0.35
81
Sample 12
4500
2100
400
0.14
79
Sample 13
3000
3600
79
0.15
72
Sample 14
1100
46
270
0.05
74
Sample 15
1800
290
410
0.05
21
Sample 16
1300
110
52
0.12
150
Sample 17
1300
93
100
0.08
96
Sample 18
1600
240
170
0.17
38
Sample 19
1300
810
56
0.05
39
Sample 20
1500
630
300
0.07
23
Sample 21
3400
1600
45
0.16
34
Sample 22
2300
580
130
0.05
67
30
600
1
600
Criteria
NEPM HIL
5.3
NEPM EIL
2000
Background
150
10
Backfill samples
Composite samples were taken of the four piles of soil proposed to be used as backfill. The
results of the analyses are summarised in Tables 8 & 9. The laboratory analysis for chromium
was for both total chromium, which includes the normally common Cr (III) as well as the
rarer, toxic for Cr (VI).
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Table 8. Summary of Back fillSoil Analyses – Total Heavy Metals
Mg/kg
As
Cd
Cr
(total)
Cr (VI)
Cu
Pb
Hg
Ni
Zn
Pile A1
<5
<0.2
12
<1
6
7
0.09
9
22
Pile B2
<5
<0.2
11
<1
5
7
0.09
8
18
Pile B3
<5
<0.2
13
<1
6
6
0.07
9
18
Pile B4
<5
<0.2
12
<1
5
5
0.08
9
17
Environmental
Investigation Level
(NEPC 1999)
20
3
400
100
600
1
60
200
Health
Investigation Level
200
40
24%
2000
600
30
600
14000
Criteria *
NEPC (HIL)
Table 9. Summary of backfill analyses – Total Petroleum Hydrocarbons
Mg/kg
TPH
C6-C9
TPH
C10-C14
TPH
C15-C28
<TPH
C29-C36
Pile A1
<20
<20
<50
<50
Pile B2
<20
<20
<50
<50
Pile B3
<20
<20
<50
<50
Pile B4
<20
<20
<50
<50
65
1000*
Criteria *
Environmental
Investigation Level
NEPC
Health
Investigation Level
NEPC
5.4
Data quality
Verification of the removal of the contaminated soil was verified by visual inspection by
members of the Environmental Section of ADI Limited.
Quality assurance checks were conducted by the analystes, WSL Consultants. These involved
blank samples, spiked and duplicate samples. A summary of the results of these analytical
checks is set out in Table 10, and the full reports are in Attachment E.
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Table 10. Summary of Quality Assurance / Quality Control Criteria
Objective
Summary of
results
Compliance
Agreement between
visual inspection and
laboratory results
All samples
Yes
Chain of Custody
documentation
Completed
Completed in
full
Yes
Sample analysis
and extraction
holding times
Comply with reference
AS4482.1
All within
guidelines
Yes
Analysis of 5% field
split duplicate
samples
RPDs within 30-50%
AS4482.1
All RPDs were
<20%
Yes
Analysis of 5% field
blind replicated
samples
RPDs within 30-50%
AS4482.1
All RPDs were
<20%
Yes
Analysis of
laboratory method
blanks
No contamination of
blanks
All non-detects
Yes
Recoveries of 70-130%
All recoveries in
range of 77% 127%
Yes
RPDs within 20-35%
All RPD’s were
<20%
Yes
Comparison of field
and analytical data
Analysis of spike
recoveries
Analysis of
laboratory
duplicates
Reference
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6.
DISCUSSION
The results of the heavy metal analyses of the soil removed from the channel were reported
below the NSW “Inert Waste” category and so disposal to the Corowa Shire Landfill is
appropriate.
The results of the validation samples collected from the base of the channel all reported heavy
metals below the ANZECC/NHMRC Environmental Investigation Guidelines. It is therefore
reasonable to conclude that all of the soil contaminated with heavy metals has been removed.
The results of the backfill soil sample analyses found all heavy metal and TPH analyses
below the ANZECC/NHMRC Environmental Investigation Guidelines, and so use of this
material as backfill is justified.
7.
CONCLUSION
The process effluent from the ADI Mulwala, containing a suspension of gypsum and some
lead and mercury was drained to the Murray River via an open unlined channel for many
years. This practice has now stopped. While the drain was in use, much of the gypsum and
heavy metals in the effluent, precipitated along the base of the channel. A report by URS
consulting (Site Assessment Report 2001) found that concentrations of lead exceeded the EIL
and HIL in some samples. ADI in consultation with Defence and the local community
decided that remediation of the site by removing the contaminated material and disposing of it
offsite was the best long term solution to the situation to allow full beneficial use of the site.
The results of the remediation and validation program indicate that the project objectives have
been achieved and the areas of contaminated soil have been removed and replaced with
uncontaminated material.
The project objective of eliminating a potential source of groundwater contamination has only
been achieved with respect to lead and mercury. The soluable nitrates and sulphates from the
original effluent, have been washed down much deeper into the soil and possible into the
groundwater, over 10 meters deep. Remediation of this contamination is not possible by the
simple excavation technology used in this project.
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8.
REFERENCES
ANZECC & NHMRC
Guidelines for the Assessment and Management of Contaminated
Sites, Australian and New Zealand Environment and Conservation
Council, and National Health and Medical Research Council,
January 1992.
Australian Standard
Guide to the Sampling and Investigation of Potentially
contaminated Soil. Part 1: Non-Volatile compounds, AS 4482.1,
1997.
NSW EPA
Environmental Guidelines: Assessment, Classification, and
Management of Non-liquid Wastes, NSW Environment Protection
Authority, July 1997.
NSW EPA
Guidelines for Consultants Reporting on Contaminated Sites,
NSW Environment Protection Authority, November 1997.
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9.
LIMITATIONS OF THIS REPORT
The advice provided in this report only relates to the project described herein and ADI –
Limited accepts no responsibility for other use of the data.
Where laboratory tests, geophysical tests and similar work have been performed and recorded
by others the data is included and used in the form provided by others. The responsibility for
the accuracy of such data remains with the issuing authority, not with ADI-Limited.
This report is based on information obtained from the investigation locations, test points and
sample points and is not warranted in respect to the conditions that may be encountered across
the site at other locations. The actual subsurface conditions between sample points may differ
substantially from those reported at the sample points. However, the sample point locations
were chosen to be representative of the general area.
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Attachment D
Final Validation Report
Remediation of the Offsites Drainage Channel
CALCULATION OF THE NUMBER OF SAMPLES REQUIRED FROM BASE OF
CHANNEL TO VALIDATE THE REMEDIATION
Basis: NSW EPA, Contaminated Sites: Sampling Design Guidelines, 1995, Procedure A, page
16.
This method is based on detecting circular hot spots with 95% confidence using a square grid
sampling pattern.
Equations used:
G = R/ 0.59b
N = A/ G2
Where n = number of sampling points required.
A = size of the sampling area, m2
G = distance between two sampling points, ie, the grid size.
R = radius of the smallest hot spot that the sampling intends to detect.
For this area, let R = 15 metres.
And the sampling area A =
=
Hence, G
And, n
=
15/ 0.29
=
25 m.
=
A / G2
150 m @ 3 m wide + 250 m @ 2 m wide +400 m @ 1.5 m
1550 m2
=
1550 / ( 25 * 3 ) where the area of a grid “square” is taken as 25 m *3 m as
the sampling area is a long narrow area rather than a wide “square“ area.
=
22
So, the number of samples to be taken is 22 at a spacing of 25 metres.
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