Geotech Report - Acid Sulfate Soil Assessment

Page 2

SECTION 2 - THE SITE

Ca a
PARTNER S

 
 
 
    
 
 
  
 
 
 
 
   
  

TABLE OF CONTENTS
Page No
SECTION 1 - INTRODUCTION......csssssssssssssees ‘4
11 Project.......sccsceceers A
132 Proposed Scope of Work . il
1.3 Commission A

 

2.1 Site Description
2.2 Geology........
2.3 ASS Mapping
SECTION 3 - FIELDWORK .......ssssssssssssssssssssssesssssssssseseseteees
3.1 Drilling and Sampling Methods.
3.2 Bore Locations and Supervision
SECTION 4 - INVESTIGATION RESULTS wcescsssssssssecsssssssssssssensnees
41 RESUS .....esssecesssesersnnen
4.2 Subsurface Conditions .
4.3 Groundwater
4.4 Laboratory Testing
4.4.1 Screening Tests............
4.4.2. Chromium Suite Analysi
SRC TON CIES crmnirnnnveninssneaunsesenutescanissiuastrievesbe six otiianacova chu AiaassceneaciavavbsshoMiSuUEaopInsEIOS
5.1 Assessment Criteria for Acid Sulfate Soils
5.2 Acid Sulfate Soils ......sssssssessssssessssnssesseues ;
5.3 Neutralisation of Disturbed ASS.........ssssssssussessssessssnesssssssssessssnnssnuuseseesseneee
TABLES:

 

 

Table 1: Observed Groundwater Depths/Reduced Levels During Drilling ......:sscscsessesssssseened
Table 2: Summary of Screening Test Results. 6
Table 3: Summary of Laboratory Results 8
Table 4: Action Criteria Based on ASS Analysis for Three Broad Texture Categories............... 9
ATTACHMENTS:

Drawing No. 1 Locality Plan & Test Locations

Appendix A Bore Reports with Explanatory Notes

Appendix B Laboratory Report Sheets

Appendix C Draft Acid Sulfate Soil Management Plan

 

Residential Development
215-219 David Low Way, Peregian Beach
Project No. 07160 18 June 2007

Page 3

 

SECTION 1 - INTRODUCTION

1.1 Project

It is understood that it is proposed to develop the site by the construction of a residential development partly
suspended over a single level basement carpark at approximately RL 4.0m to RL 6.1m, involving approximately
2m maximum depth of bulk excavation. The location of the site and a potential layout for the development are
shown approximately on Drawing No. 1 attached.

1.2 Proposed Scope of Work

It was anticipated that the site ground conditions might comprise fill material, sands and silts overlying estuarine
clays. Based on the scope of the proposed development, the anticipated ground conditions and the
requirements of Sections 6 to 8 of the State Planning Policy 2/02 Guidelines - Planning & Managing
Development Involving ASS, it was proposed to investigate the site at the same time as (but separate from) an
Environmental Site Assessment (ESA) by:

© collecting samples at 0.25m intervals from six bores to a depth of 2.5m, or prior refusal;

* conducting acid sulfate soil (ASS) screening tests on all samples recovered from the bores;
© undertaking Chromium Suite laboratory testing on selected soil samples; and

© — preparation (if required) of an Acid Sulfate Soils Management Plan (ASSMP).

1.3 Commission

Based on the proposed nature of the development, the anticipated subsurface conditions and the scope of work,
a fee to undertake the assessment was presented in a proposal of 23 March 2007. Butler Partners was
subsequently commissioned by Scanlon Properties Pty Ltd to undertake the assessment as proposed.

 

Residential Development Page 1 of 10
215-219 David Low Way, Peregian Beach
Project No. 07160 18 June 2007

Page 4

 

SECTION 2 - THE SITE

21 Site Description

At the time of investigation the site was developed as a caravan park. A one and two storey ‘Manager's
Residence/Office’ and a single storey ‘Amenities Block’ were located on the eastern side of the site, with the
remainder of the site comprising caravan parking areas surrounded by grassed areas with medium to tall trees
and a gravel and partly paved ‘ring-road’ around the site. Ground surface levels reduce non-uniformly across
the site from east to west from a high at David Low Way of approximately RL10m to a low along the western
boundary of approximately RL2.5m. Three general views of the site at the time of the investigation are given in
Photographs 1 to 3.

 

   

Photograph 2: General view of the site looking north from the south-western corner

 

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215-219 David Low Way, Peregian Beach
Project No. 07160 18 June 2007

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ia ii =a as E
Photograph 3: General panoramic view of the site looking north-west to north-east from the southern side of the site

2.2 Geology

Reference to Queensland Department of Mines and Energy’s 1:100,000 Gympie Special sheet indicates that the
site is mapped in an area of Quaternary Parabolic Dunes comprising quartz sand and Estuarine Deposits
comprising sandy mud, muddy sand and minor gravel.

2.3 ASS Mapping

Reference to the Department of Natural Resources and Mines’ (DNR&M) Acid Sulfate Soils Redcliffe to Teewah
Map 2 indicates that the site is located approximately on the boundary of areas mapped as “land >5m with low or
negligible probability of ASS occurrence” and “land with limited field assessment, but where there is a
reasonable probability of ASS occurrence”,

 

Residential Development Page 3 of 10
215-219 David Low Way, Peregian Beach
Project No. 07160 18 June 2007

Page 6

 

SECTION 3 - FIELDWORK

3.1 Drilling and Sampling Methods

Fieldwork was undertaken on 14 May 2007 and comprised the drilling and sampling of six bores using a trailer-
mounted Hydrapower Trekker drilling rig operating solid flight augers. Strata identification and sampling was
from drill cuttings brought to the surface on the auger flights.

All soil samples collected from the bores were placed in plastic bags that were sealed after removing as much air
as possible and stored on ice prior to analysis.

3,2 Bore Locations and Supervision

Bore locations were determined in the field by direct measurement from existing site features and are indicated
approximately on the attached Drawing No. 1. The ground surface levels at the bore locations have been
interpolated from contours given on PMM’s Combined Detail Survey Plan (Drawing No. 7328-03, dated 18 April
2007).

An experienced senior geotechnician set out the test locations, logged the stratigraphy encountered in the bores
and directed the in-situ sampling and testing program.

 

Residential Development Page 4 of 10
215-219 David Low Way, Peregian Beach
Project No. 07160 18 June 2007

Page 7

 

SECTION 4 - INVESTIGATION RESULTS

44 Results

The subsurface conditions encountered in the bores are given on Bore Report Sheets included in Appendix A,
using classification and descriptive terms defined in the accompanying notes. Laboratory test report sheets are
included in Appendix B.

4.2 Subsurface Conditions

For a description of the stratigraphy encountered in the bores, the Bore Report sheets should be consulted.
However, in broad summary, the subsurface conditions encountered in the bores generally comprised a surface
layer of either fill material (in Bores 1 to 4) that varied up to a maximum depth of 0.8m, or silty sand (in Bores 5
and 6) to a maximum depth of 0.4m. In Bores 1 and 2 only, the fill was underlain by natural, dark grey-brown
silty clays that were underlain in turn by silty sands that were indurated below 2m depth. In Bores 3 to 6, the
surface fill or silty sand layer was underlain by sands.

4,3 Groundwater

Free groundwater was encountered during the drilling of four of the six bores at the depths/RLs given in Table 1.
It should be noted that groundwater levels can vary seasonally and with prevailing weather conditions.

Table 1: Observed Groundwater Depths/Reduced Levels During Drilling

Groundwater Observations

Folp Depth Reduced Level
1 0.8 RL 2.3m
"2 08 | RL23m
3 46 RL 6.0m
4 Not encountered
5 16 | RL 5.9m
6 Not encountered

44 Laboratory Testing

4.4.1 Screening Tests

Screening tests were undertaken on all soil samples collected from all bores. The screening tests comprised
two small sub-samples of soil; one mixed with approximately 20 mL of distilled water, and the other mixed with
approximately 20 mL of hydrogen peroxide, buffered to a pH of 5.0 with sodium hydroxide.

Slurry pH was measured with a calibrated pH meter. The pH of the distilled water/soil slurry (pHr) was
measured approximately one hour after mixing, whilst the pH of the hydrogen peroxide/soil slurry (pHrox) was
measured approximately one to two hours after mixing.

 

Residential Development Page 5 of 10
215-219 David Low Way, Peregian Beach
Project No. 07160 18 June 2007

Page 8

 

The pH screening tests can be used for preliminary identification of potential or actual ASS, using a combination
of three trigger factors' as follows:

(a)

The strength of the reaction with peroxide is a useful indicator but cannot be used alone. Organic

matter and other soil constituents such as manganese oxides can also cause a reaction.

(b)

A pHrox value at least one unit below pHr may indicate a potential acid sulfate soil (PASS). The greater

the difference between the two measurements, the more indicative the value is of a PASS. The lower

the final pHrox value the better the indication of a positive result.
If the pHrox <3, and the other two conditions apply, then it strongly indicates a PASS. The more the

(°)

pHrox drops below 3, the more positive the presence of sulphides.

The results of the screening tests undertaken on samples recovered from the bores are given in Table 2,
together with an indication of which (if any) trigger factors were noted.

Sample
Depth
ea)
0.0-0.25

Bore

0.5-0.75
0.75-1.0
1 | 1.0-4.25
4.25-1.5
1.51.75
1.75-2.0
2.0-2.25
0.0-0.25
0.25-0.5
0.5-0.75
| 0.75-1.0
2 | 4.0-4.25

4.25-1.5

4.5-1.75
1.75-2.0

2.0-2.25

 

 

0.25-0.5 |

Table 2: Summary of Screening Test Results

Material
Type

Fill
Fill
Fill
Fill and Silty Clay
Silty Clay and Silty Sand
Silty Sand
“Silly Sand
Silty Sand
Silty Sand
‘Fill
Fil
Fill
Fill and Silty Clay
Silty Clay and Silty Sand
‘Silly Sand
Silty Sand
Silty Sand
~ Silty Sand

 

Reaction

Medium
“Medium —
Strong
Strong
Strong
Weak
Very Weak
Very Weak
Very Weak
Very Strong
Very Strong

Very Strong

Strong
‘Strong
Medium
Medium
Medium

"Medium

 

pHr

47
48
46
55
54

5.6

| Bia

5.0

“49

6.5
5.3

5.3

5.4
5.7
5.4

| 5.1

54 |

 

pHrox

2.0

29 |

1A
1.2
17
23
“4.9
28
~ 28
27
24
15
17
13
1.9
24
18

| 1.8

 

Screening Test Indicators

Strong reaction
with peroxide

 

PHr-pHrox>1 | pHrox<3
v v
v v
v v
v v
v v
v v
v —v
vo v
v v
vo v
v v
v v
—+——-
v v
v v
v v
v v
7 7

 

1 Ahern C.R., Ahern M.R., Powell B. Guidelines for Sampling and Analysis of Lowland Acid Sulfate Soils (ASS) in

Queensland 1988

 

Residential Development
215-219 David Low Way, Peregian Beach

Project No. 07160

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18 June 2007

Page 9

 

 

 

 

 

 

 

 

  
 

 

~ Screening Test Indicators

 

| Strong reaction
with peroxide

pHr-pHrox>1 | pHrox<3

 

 

 

 

 

 

 

 

 

 

 

Semple Material
Bore | Depth Reaction | pHr | pHrox
Type
Sb i | : Sk
0.0-0.25 Fill and Sand Weak | 5.2
0.25-0.5 | “Sand SSs|s«CVery Weak | 4.5
05-0.75| ~~ Sand Very Weak | 5.0
ee Ma ee fag
; ry Weak | 50 |
Very Weak | 4.8
Sand " VeryWeak | 5.3 | 5.
Sand | VeryWeak | 5.6 | 58
Sand ———™s«WVery Weak | 559 | 5.8
Sand Very Weak | 6.1 | 5
FillandSand | Weak | 62 |
Sand Very Weak | 5.4
i Sand ‘| Very Weak | 5.3
Sand | VeryWeak | 49] 52 |
r Sand | VeryWeak | 5.7 | 56
Sand VeryWeak | 5.9 | 5.1
Sand Very Weak | 5.5 | 55
Sand | VeryWeak | 5.9 | 5.5
Sand VeryWeak | 6.0 | 55
Sand | VeryWeak | 59 | 56
Silty Sand Weak | 5.5 | 23
Silty Sand and Sand Weak 57 | 24
7 Sand Weak | 64] 44
Sand Weak | 58] 43 |
5 | 10425 Sand | Very Weck | 5.0) 48 |
1.25-1.5 Sand Very Weak | 4.9 | 5.0
4.51.75 Sand Very Weak | 5.2 | 5.7
1.75-2.0 Sand VeryWeak | 5.8 | 5.6
(20-225) Sand VeryWeak | 5.7 | 56 |
2.25-2.5 Sand Very Weak | 5.9 | 56 |
/ 0.0-0.25 Silty Sand | Weak | 62| 39
0.25-0.5 | Silty Sand and Sand Very Weak | 6.3 | 5.0_
05-075| Sand VeryWeak | 5.9 | 54 | |
0.75-1.0 Sand Very Weak | 6.2 | 57
| 104.25 _ Sand | VeryWeak | 5.9 | 44 -
4.25-1.5 Sand Very Weak | 6.1 | 5.8
1.5-4.75 Sand —Sséd|s«VeryWeak | 5.6 | 58
75-20} Sand  —~'| *‘VeryWeak | 58) 57 |
Sand “Very Weak | 5.4] 5.1
“Sand | VeryWeak | 5.9] 57 |

 

 

 

 

 

 

 

 

 

v
v
v
7

 

 

 

The results of the screening tests indicate reactions ranging from very weak to very strong after the addition of
hydrogen peroxide; pHrox values 1 pH unit below the pH value measured in nearly all the samples analysed;
and a significant number of samples analysed yielded pHrox values below 3 pH units.

 

Residential Development
215-219 David Low Way, Peregian Beach

Project No. 07160

Page 7 of 10

18 June 2007

Page 10

 

PARTNERS

In summary, the results of the screening tests are considered to give a reasonably strong indication of possible
ASS presence in Bores 1 and 2, However, it is considered that there was generally no strong indication of ASS
presence (with some exceptions in the upper 1.5m depth) in Bores 3 to 6. As a result of the mixed screening
test results, it was considered that Chromium Suite laboratory analysis should be conducted on selected

samples.

4.4.2

Chromium Suite Analysis

Based on the results of the screening test results, samples were selected for Chromium Suite analysis and were
kept on ice until transported to Australian Laboratory Services Pty Ltd (ALS) under standard chain of custody
protocol. A summary of the test results is given in Table 3.

Depth
(m)

Bore

0.25-0.5
4 | 1.01.25
2.25-25
0.75-1.0
2 | 15-475
2.25-2.5
 0.5-0.75

2.0-2.25
1,75-2.0

 

a ari w

Results in Bold exceed the QASSIT Action Criteria for disturbance of >1000 tonnes of soil (Section 5.1)

125-45 |

 

Table 3: Summary of Laboratory Results

Material

Fil
Silty Clay and Silty Sand
Silty Sand
Fill and Silty Clay
Silty Sand
Silty Sand
Sand
Sand
Sand
Sand

 

pHke

5.6
5.4
5.4
5.4
5.7
5.6

i,

6.5
63
6.5

 

Titratable
Actual
Acidity

hs

<0.02
<0.02
<0.02
0.02
<0.02
<0.02

30.02 |

<0.02
<0.02
<0.02

 

Chromium
Reducible
Sulfur - (Scr)
%S

<0.02
~ <0,02,
<0,02
0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02

Net
Acidity
%S

<0.02

<0.02 |

<0.02
0.04
| <0.02
<0.02
<0.02
<0.02
<0.02
<0.02

 

Liming
Rate*
(kgit)

* Based on the use of good quality fine ag-lime with a neutralising value of 100 % and incorporating a factor of safety of 1.5 to allow for
inconsistencies in mixing during application

 

Residential Development

215-219 David Low Way, Peregian Beach

Project No. 07160

Page 8 of 10

18 June 2007

Page 11

 

SECTION 5 - COMMENTS

5.1 Assessment Criteria for Acid Sulfate Soils

ASS in Queensland are assessed in accordance with the Queensland Acid Sulfate Soils Investigation Team
(QASSIT) Guidelines for Sampling and Analysis of Lowland Acid Sulfate Soils (ASS) in Queensland 1998
(QASSIT Guidelines) and the State Planning Policy 2/02 Guideline Planning and Managing Development
Involving Acid Sulfate Soils. The State Planning Policy 2/02 Guideline provides Action Criteria for assessing the
results of laboratory testing quantifying the acid producing effects based on the sum of existing plus potential
acidity. These action criteria are presented in Table 4.

Table 4: Action Criteria Based on ASS Analysis for Three Broad Texture Categories

Action Criteria Action Criteria
Type of Material (1 - 1000 tonnes disturbed) (> 1000 tonnes disturbed)
Existing + Fptential Acidity Existing + Potential Acidity
Equivalent Equivalent Acidity | Equivalent | Equivalent Acidity
ik Teanbbiie een Sulfur (%S) | (molHtitonne) | Sulfur (%S) | (mol H*/tonne)
5 "! | (oven-dry basis) | (oven-dry basis) | (oven-dry basis) | (oven-dry basis)
Coarse Texture
ede tober aendl <5 0.03 18 0.03 18
Medium Texture
Sandy loams to light clays on 0.06 id 9.03 8
Fine Texture

Medium to heavy clays, silty clays 240 ort 62 0.03 18
As the amount of natural soil to be disturbed during the proposed works is anticipated to exceed 1,000 tonnes of

soil, the ‘greater than 1000 tonne’ Action Criteria of 0.03 %S from Table 4 has been used as the basis for
assessment of site soils.

5.2 Acid Sulfate Soils

Samples tested from within the fill material and natural sands/silty sands reported net acidity levels less than
0.03% and these materials are therefore not considered to be ASS.

Samples tested from within the natural silty clays indicated levels of actual acidity below laboratory reporting
limits, with one exception. The silty clays are therefore considered to include an apparently limited amount of
ASS, potentially at isolated locations. Whilst the amount of ASS in the silty clay soils appears to be relatively
low, under State Planning Policy 2/02 they will nevertheless require management and treatment to neutralise
any net acidity, if they are to be disturbed. As such, an Acid Sulphate Soil Management Plan (ASSMP) is
required and a draft ASSMP is presented in Appendix C for consideration.

 

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215-219 David Low Way, Peregian Beach
Project No. 07160 18 June 2007

Page 12

 

5.3 Neutralisation of Disturbed ASS

The calculated liming rate for the natural silty clay soils based on the results of the Chromium Suite results is
given in Table 3 (and on the laboratory report sheets included in Appendix B) and is 2 kg of ag-lime/tonne of dry
natural silty clay soils, based on a factor of safety of 1.5 and the use of good quality fine ag-lime with a
neutralising value of 100 %.

It is suggested that consideration be given to the adoption of a neutralising value of 80 % in calculation of the
required liming rate to allow for potential inconsistencies in the quality of the ag-lime. The calculated liming rate
using a neutralising value of 80 % for the ag-lime would be approximately 3 kg dry natural silty clay soils.

 

BUTLER PARTNERS PTY LTD
Reviewed by
BRUCE BUTLER MIKE NEIGHBOUR
Principal Principal
Residential Development Page 10 of 10

215-219 David Low Way, Peregian Beach
Project No. 07160 18 June 2007

Page 13

 

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