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22244-002-Rev1 Barina Ct
26 February 2024 Project No. 22244-002-Rev1 Mark Kussrow C/- CadCon Surveying & Town Planning Email: [email protected] GEOTECHNICAL INVESITGATION OF EXISTING DAM 38 BARINA COURT, POMONA Dear Mark, 1.0 INTRODUCTION Tectonic has undertaken a geotechnical investigation, including a slope stability assessment for the existing main dam at 38 Barina Court, Pomona. Tectonic previously completed a slope stability assessment for a proposed subdivision (Ref. Tectonic Report No. 22244-001-Rev1, dated 8 December 2022). Although it was concluded that failure of the main dam would not impact the recommended Low Risk building and effluent disposal areas as outlined within our report, it is understood that a geotechnical investigation was requested by Noosa Council to assess the main dam and provide recommendations to achieve a Low Risk of dam instability. This report presents the results of our geotechnical investigation, together with geotechnical advice for the existing dam. In summary, subject to implementation of the recommendations made herein, and based on the condition of the dam at the time of our assessment, a satisfactory factor of safety (FOS) against dam embankment instability would be achieved. 1.1 Details of Site and Background The property is formally described as Lot 3 on RP226620, covers an area of about 6.4 ha, has narrow frontage to Barina Court in the north-eastern corner, and direct frontages to Pomona Connection Road and Cooroy-Gympie Road along the western and southern boundaries, respectively. At the time of our assessment, an existing residence and outbuildings were located in the north-eastern corner of the site, with the main dam along the western boundary. The main dam wall comprised an earth fill embankment, located along the southern edge of the reservoir, and was estimated to range between about 2 m and 4.5 m high. The wall crest varied between about 3.5 m and 5.5 m wide, with the downstream embankment formed at about 20° in the west increasing up to about 27° progressing eastwards. The upstream edge of the embankment was battered at about 30° for a height of 1 m below the crest, reducing to about 10° extending below the water level. A spillway was present in the south-western corner of the dam, being about 4 m wide and 1.5 m lower than the dam wall crest. Overflow from the dam was directed to the south by a relatively narrow channel, before ‘dog legging’ to the east towards a natural drainage line further downstream. Scouring within the dam overflow channel up to about 1 m deep was observed, some of which had been reinstated with rock fill. It appeared that the dam had been historically constructed over a natural drainage line which traced the western property boundary before continuing in a south-easterly direction towards a creek in the southern part of the site. A smaller dam was located downstream (south-east) of the main dam; however, was not included as part of this assessment. Text Figure 1 overleaf is a 2023 aerial image of the site and surrounds. Tectonic Geotechnical Pty Ltd PO Box 899, Buderim, QLD 4556 Office: (07) 5478 9016 Email: [email protected] www.tectonicgeo.com.au A.B.N. 83 165 727 828
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Mark Kussrow 22244-002-Rev1
C/- CadCon Surveying & Town Planning 26 February 2024
Main dam
Subject site
Text Figure 1: 2023 aerial image of the site and surrounds (courtesy of Nearmap imagery)
Site images at the time of the investigation are provided in Text Figures 2 to 4 below and overleaf.
Text Figure 2: Westerly view across the dam, with drill rig set up at borehole BH1
Text Figure 3: Easterly views of the downstream face of the dam wall
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Mark Kussrow 22244-002-Rev1
C/- CadCon Surveying & Town Planning 26 February 2024
Text Figure 4: Views of the overflow channel below the dam embankment
Historic aerial photographs from Nearmap and Qimagery were reviewed which suggest that the dam was
constructed sometime between 1986 and 1993. Since then the embankment has remained relatively
unchanged. What appeared to be cattle tracks developed in the south-eastern corner of the main
embankment sometime between 2015 and 2017. These seemed to have been reinstated between 2022 and
2023. No obvious signs of previous global dam wall instability were observed in higher resolution imagery as
part of the historic aerial review, nor were there any surface features identified during the investigation which
would indicate recent instability.
2.0 METHOD OF INVESTIGATION
2.1 Fieldwork
An experienced geotechnical engineer from Tectonic undertook a site walk-over on 22 January 2024 to
visually assess any indicators of past slope instability around the main dam wall. The walk-over included
assessment of soil outcrops, surface drainage conditions, topography, evidence of erosion, and vegetation
coverage/condition. This was complimented by a subsurface investigation comprising:
One borehole (designated BH1) drilled to a depth of 7.5 m below ground level (BGL), in the eastern
part of the dam wall crest (highest embankment area).
One borehole (designated BH2) was drilled to 3.5 m BGL, on the gently sloping ground below the
toe of the dam wall.
One standalone dynamic cone penetrometer (DCP) test was conducted within the drainage line
adjacent to the toe of the dam wall for an assessment of the consistency/density of the materials in
the bed.
Boreholes were drilled using a 4WD mounted solid flight auger rig in the presence of an experienced
geotechnical professional from Tectonic. In situ strength of soil materials in the boreholes was estimated
from DCP testing adjacent to and within each borehole, along with pocketer penetrometer testing on
relatively undisturbed auger cuttings. Disturbed samples were collected from selected horizons in the
boreholes through the dam embankment, and natural soils at depth below.
Logs of the boreholes are attached, together with explanatory notes. Approximate borehole locations are
shown in Figure 1, attached at the end of the report text.
2.2 Laboratory Testing
Selected soil samples were dispatched to Construction Sciences, a NATA accredited geotechnical laboratory
located in Kunda Park, for testing in accordance with Australian Standard AS1289 Method for Testing Soils
for Engineering Purposes. The laboratory testing scheduled comprised two Atterberg Limits, Particle Size
Distribution and Emerson Class Number (ECN) tests to assist with assessment of material properties and
classification. Laboratory test results are summarised in Section 3.3, and test certificates are attached at the
end of this letter.
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Mark Kussrow 22244-002-Rev1
C/- CadCon Surveying & Town Planning 26 February 2024
3.0 DESCRIPTION OF EXISTING CONDITIONS
3.1 Geology
The 1:100,000 scale Gympie Surface Geological Map 1 (Ref. Text Figure 5 below) indicates that the site is
underlain by materials derived of the early to middle Triassic age Kin Kin Beds (blue-green shading),
which are described as “commonly cleaved and commonly kinked mudstone…” The Australian
Stratigraphic Units Database describes the Kin Kin Beds as “arenite, argillite and phyllite.” Quaternary
age alluvial deposits are mapped around a creek along the southern boundary of the site.
Approx. Site Location
Text Figure 5: Extract of Gympie Surface Geology Map
3.2 Subsurface Conditions
Detailed descriptions of the subsurface conditions encountered in the boreholes are provided in the
borehole reports attached, along with definition sheets which describe terms and abbreviations used on the
reports. DCP results are also provided on the borehole logs. Subsurface conditions encountered in the
boreholes are summarised as follows:
Fill/Topsoil – comprising mostly stiff to very stiff, silty and gravelly clays of medium plasticity to
depths between 0.9 m and 3.3 m BGL; then
Natural Soils – very stiff to hard, silty and gravelly clay of medium to high plasticity to depths
between 2.1 m and 7.5 m BGL (borehole BH1 termination depth).
Extremely Weathered (XW) Materials – borehole BH2 intersected hard, gravelly clay of medium
plasticity which was noted to be tending towards very low strength phyllite to the termination depth
of 3.5 m BGL.
Standalone DCP1 which was conducted in the bed of the drainage line below the main dam wall toe
indicated a stiff/medium dense (or stronger) profile to 2.2 m BGL, becoming very stiff/dense (or stronger) to
the termination depth of 2.4 m BGL.
Groundwater inflow was encountered below about 3.1 m BGL in borehole BH1, with no groundwater
encountered in borehole BH2.
1
State of Queensland, Dept. of Natural Resources, Mines and Energy, Gympie Surface Geology, Sheet 9445, 2018
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3.3 Geotechnical Laboratory Test Results
Full geotechnical laboratory test certificates are attached at the end of the report text. Table 1 summarises
the results of geotechnical laboratory testing conducted on soil samples recovered from the boreholes.
Table 1: Summary of Geotechnical Laboratory Results
Atterberg Limits
Depth Linear
BH ID Liquid Limit Plasticity ECN
(m BGL) Shrinkage Fines (%)
(%) Index (%)
(%)
BH1 0.3 – 0.6 42 17 8.5 47 4
BH1 3.4 – 3.6 42 19 9.5 78 4
Notes: Fines Content is the percentage of clay/silt fraction in the soil sample
Laboratory test results indicate that the soils tested from borehole BH1 were gravelly and silty clays of
medium plasticity. ECN testing of disturbed samples from borehole BH1 returned values of 4. This indicates
that there was slaking but no dispersion before remoulding and no dispersion after remoulding. The results
suggest that the existing dam wall fill materials, and natural soil samples tested, have a low dispersion
potential.
4.0 STABILITY ASSESSMENT
4.1 Existing Embankment Construction
No records have been sighted regarding certification and testing of the fill placed during the construction of
the earthen dam embankment, and no formal construction records regarding site stripping, foundation
preparation, fill placement, moisture conditioning and compaction were provided prior to our assessment.
However, based on the results of borehole logging and in situ testing completed as part of the investigation,
we make the following comments:
The embankment appears to be of homogenous construction.
Materials forming the embankment mostly comprised silty and gravelly clays that could generally be
considered acceptable for dam construction. Rootlets were encountered at the fill/natural soil
interface but topsoil materials were not apparent.
From in situ soil strength testing in the boreholes, it is inferred that the embankment fill has been
compacted to some degree (rather than being end tipped and loosely placed). However, it cannot
be stated whether compaction levels meet the minimum standard of compactive effort (i.e. typically a
dry density ratio of 95 % of the Maximum Standard Dry Density Ratio [DDR]).
The foundation subgrade beneath the crest of the dam appears to comprise stiff to very stiff clays.
4.2 Stability Assessment (Quantitative)
A global stability assessment was carried out for the main dam wall, based on our investigation results, and
our understanding of the construction. Combined with our site observations, we have completed a
quantitative assessment of slope stability, comprising numerical analysis using Slope/W. This has been
used to calculate a factor of safety (FOS) against slope instability, and to check that a FOS ≥ 1.5 can be
achieved based on the model developed as part of this report. FOS values of ≥ 1.3 and ≥ 1.5 are the
general industry minimums for short- and long-term conditions, respectively.
Our model was developed based on the following assumptions:
The dam embankment profile across the upstream, downstream and crest areas was developed by
field mapping as described in Section 1.1. The analysed section considered the highest
embankment observed, this being about 4.5 m high, with a crest width of 3.5 m and a downstream
face slope of about 27°.
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Mark Kussrow 22244-002-Rev1
C/- CadCon Surveying & Town Planning 26 February 2024
For long term conditions the reservoir water level was plotted at about 1 m below the crest wall, with
the associated groundwater level reducing through the embankment to ‘daylight’ just below the toe
level. This was consistent with the measured groundwater inflow level in borehole BH1 drilled
through the embankment during the investigation.
For short term more adverse conditions, a ‘rapid drawdown’ scenario was considered, where the
reservoir level remains high (at 1 m below the crest) and groundwater extends at a similar level
through the embankment, with the maximum extent of the downstream toe ‘dry’.
The spillway will need to be upgraded based on design for the anticipated stormwater flows and
velocities, such that the main dam wall does not overtop during flooding events.
Results of the numerical slope stability analysis are illustrated in Text Figures 6 and 7 below and overleaf.
The key points from our analysis are summarised as follows:
Unit weight and shear strength parameters adopted for the soil strata were taken from the mid-range
of values recommended for similar materials in Appendix D of Australian Standard AS4678-2002
Earth Retaining Structures.
Analysis was undertaken for specified slip entry and exit zones, generally covering the upstream
dam face and crest area, together with the downstream face and toe area, respectively.
Minimum FOS values of 1.3 and 1.5 were calculated for the existing dam for short- and long-term
conditions, respectively. This assumes that a minimum freeboard of 1 m is maintained below the
crest of the dam wall.
Our analysis indicates that an acceptable FOS, and subsequent Low Risk, against global slope instability is
achievable for the existing dam, subject to implementation of the recommendations in Section 5.
Text Figure 6: Slope/W output for existing dam wall – long term conditions
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Mark Kussrow 22244-002-Rev1
C/- CadCon Surveying & Town Planning 26 February 2024
Text Figure 7: Slope/W output for existing dam wall – short term conditions
5.0 ENGINEERING ASSESSMENT
5.1 Dam Embankment Rehabilitation
To achieve a Low Risk against global instability for the main dam wall, the following rehabilitation works are
recommended:
A civil/hydraulic RPEQ must complete an assessment of the catchment hydrology and anticipated
flows. Subject to the results of the civil/hydraulic assessment, the existing spillway may need to be
upgraded to ensure that a minimum freeboard of 1 m is maintained beneath the embankment crest,
thus preventing water overtopping the embankment including during flood events.
The surface of the dam embankment is to be protected from erosion by spreading topsoil to not
more than 200 mm thickness and planting out using Lomandra Longifolia at spacings of about 1 m.
Depending on the civil/hydraulic assessment and the anticipated stormwater flows, the existing
channel along the embankment toe may also require upgrades to accommodate future flows during
flood events. Stormwater flows must not be allowed to overtop the dam embankment crest or
associated discharge channels.
Areas exhibiting existing erosion scours within the main spillway discharge channel must be
reinstated and protected from future erosion. The erosion protection required will be dependent on
the anticipated stormwater flows which are to be determined by hydraulic analysis by a civil/hydraulic
RPEQ. An indicative specification for rock fill is provided below, however the necessary grading for
the rock fill should be assessed by a hydraulic or civil RPEQ prior considering anticipated stormwater
velocities.
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Mark Kussrow 22244-002-Rev1
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Clays if required for reinstatement are to be placed in layers not more than 200 mm (loose thickness) and
compacted by several passes of a pad foot roller to achieve a dry density ratio (DDR) of at least 95%
(standard) at a moisture content within +1% to +2% of the optimum moisture content.
Select rock fill shall be sound igneous or metamorphic material that will not disintegrate when exposed to
weather, or easily erode. Rocks should be fresh or slightly weathered, being of very high strength (or
stronger) as defined by AS1726. The least dimension of the rock should be not less than half its greatest
dimension.
Select rock fill could have the following grading:
D50 (mm) 500-700
D15 (mm) 250-350
D85 (mm) 700-1000
DMAX (mm) 1000
Rock fill shall be placed in such a manner that all relatively large stones shall be essentially in contact with
each other, and all voids filled with the finer rock to achieve a well graded, compact mass. Rock fill shall be
washed on adjacent areas, or prior to being transported to site, to remove fine material prior to handling and
placement. The rock fill must be ‘benched’ into the slope. Rock fill placement and compaction should be in
accordance with the mechanical interlock method as specified in Clause 15.4 of Main Road Technical
Standard MRTS04 General Earthworks.
5.2 Dam Monitoring and Maintenance
In general, make sure that the dam spillway is kept clear of debris and that the minimum freeboard of 1 m is
maintained at all times. The downstream face of the dam embankment should be planted out and kept free
from weeds. Trees, including small saplings, should not be allowed to develop on the embankment.
A maintenance inspection of the dam should be made following any rainfall exceeding 100 mm within 24
hours, during which the spillway, dam embankment and downstream toe area should be assessed, as
discussed below. It is recommended that the dam inspections should be undertaken by the property owner.
Should any signs of instability be observed, Tectonic and the design civil engineer should be advised
immediately to arrange a site inspection and determine an appropriate course of action.
The embankment should be examined for signs of cracks, piping, settlement, slides, and development of
seepage (on the downstream face). Any cracks should be filled immediately with well compacted clay.
There are three main kinds of cracks: transverse, longitudinal and shrinkage. Transverse cracks are those
that run straight through the dam from the upstream to the downstream side. Longitudinal cracks develop
parallel to the crest length. Shrinkage cracks develop in a random pattern of both transverse and
longitudinal defects. Cracks can also lead to another kind of failure known as piping, which is a term used
when seepage water creates a tunnel or pipe along a line of weakness through the dam.
Settlement in the crest should be rectified by building up the crest level to ensure that there is no overtopping
of the embankment, however such work should only be conducted under the direction of an experienced
geotechnical RPEQ.
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Mark Kussrow 22244-002-Rev1
C/- CadCon Surveying & Town Planning 26 February 2024
6.0 LIMITATIONS
This assessment relates only to the main dam embankment. Existing structures, slopes, embankments, and
driveways may be subject to risk of slope instability, but assessment of those matters was beyond the scope
of our commission for this assessment.
Your attention is drawn to the document Limitations, which is attached to this letter report.
Please contact the undersigned should you wish to discuss any of the above matters.
Yours faithfully
TECTONIC GEOTECHNICAL PTY LTD
Michael Cocks BEng NER RPEQ 27540
Senior Geotechnical Engineer
Attachments: Figure 1 – Site Plan
Borehole & DCP Reports and Explanatory Notes
Laboratory Test Certificates
Limitations
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Tectonic Geotechnical Pty Ltd
PO Box 899
Buderim Qld 4556
Office: 07 5478 9016
Email: [email protected]
PROJECT:
GEOTECHNICAL INVESTIGATION
Main Dam #38 OF EXISTING DAM
38 BARINA COURT, POMONA
TITLE:
SITE PLAN
BH1
CLIENT:
MARK KUSSROW
DCP1
DRAWN: DATE:
MO 23/02/2024
BH2 CHECKED: DATE:
MCC 23/02/2024
SCALE:
AS SHOWN (APPROX.)
LEGEND:
APPROXIMATE BOREHOLE
LOCATIONS
APPROXIMATE
STANDALONE DCP
LOCATION
Notes: PROJECT NO.: FIGURE: REV:
Base image courtesy of Nearmap imagery, dated 1 July 2023 0 10 20 30 40 m 22244-002 1 0
Page 11
Borehole No.
BH1
Page 1 of 1
Engineering Log - Borehole Project No.: 22244
Client: Mark Kussrow Commenced: 22/1/2024
Project Name: Assessment of Existing Dam Completed: 22/1/2024
Hole Location: 38 Barina Court, Pomona Logged By: MO
Hole Position: 483860.0 m E 7081633.0 m N MGA2020 Zone 56 Checked By: MCC
Drill Model and Mounting: 4WD Auger Inclination: -90° RL Surface: No survey
Hole Diameter: 100 mm Bearing: 360° Datum: AHD Operator: WD
Drilling Information Material Description and Observations
Relative Density
Classification
Pocket DCP TEST
Penetration
Consistency
Graphic Log
Samples Material Description
Penetrometer
Recovery
Condition
Tests soil type: plasticity or particle characteristics,
Moisture
UCS Blows per 100 mm
Symbol
Method
Remarks secondary and minor components, colour
Water
RL Depth (kPa)
(m) (m) 0 5 10 15 20 25
100
200
300
400
500
340
Silty SAND (TOPSOIL), fine to medium grained, MD 370
brown, with rootlets 280
DS Gravelly CLAY (FILL), medium plasticity, pale
0.3-0.6m brown, fine to medium subangular gravel, with
fine to coarse grained sand VSt
310
DS 1 290
0.9-1.2m
160
M Augered to 1.6m
DS
1.6-1.9m
2 140
St
TECTONIC 3.00.2 LIB.GLB Log 1 TECTONIC BOREHOLE 22244.GPJ <<DrawingFile>> 23/2/2024 10:39 10.02.00.04 Datgel Lab and In Situ Tool - DGD | Lib: Tectonic 3.00.2 2021-03-30 Prj: Tectonic 3.00.2 2021-03-30
180
DS
2.7-3.0m Augered to 3.0m
3
Groundwater [email protected]
20/90mm
CI Silty CLAY, medium plasticity, pale brown, with
DS fine to coarse grained sand, trace fine gravel, with
3.4-3.6m rootlets
AD/T
Augered to 4.0m
4
becoming grey
DS St to
4.1-4.5m VSt
5
DS W
5.2-5.4m
6
Augered to 6.1m
VSt to
H
7
DS
7.0-7.4m
Hole Terminated at 7.50 m
Target depth
Method Penetration Water Samples and Tests Moisture Condition Consistency/Relative Density
AD/T-Auger Drilling TC Bit VE - Very Easy Level (Date) U## - Undisturbed Sample (## mm) D - Dry VS - Very Soft
AD/V-Auger Drilling V Bit E - Easy DS - Disturbed Sample M - Moist S - Soft
RT - Rotary Tri-cone Bit Inflow BDS - Bulk Disturbed Sample W - Wet F - Firm
RD - Rotary Drilling F - Firm SPT - Standard Penetration Test VSt - Very Stiff
Partial Loss
NMLC -Rock Core H - Hard H - Hard
VH - Very hard Complete Loss
HA - Hand Auger Plastic Limit VL - Very Loose
Graphic Log/Core Loss L - Loose
Classification Symbols and < PL MD - Medium Dense
Core recovered (hatching Soil Descriptions
indicates material) = PL D - Dense
Based on Unified Soil < PL VD - Very Dense
Core loss Fr - Friable
Classification System
Page 12
Borehole No.
BH2
Page 1 of 1
Engineering Log - Borehole Project No.: 22244
Client: Mark Kussrow Commenced: 22/1/2024
Project Name: Assessment of Existing Dam Completed: 22/1/2024
Hole Location: 38 Barina Court, Pomona Logged By: MO
Hole Position: 483872.0 m E 7087600.0 m N MGA2020 Zone 56 Checked By: MCC
Drill Model and Mounting: 4WD Auger Inclination: -90° RL Surface: No survey
Hole Diameter: 100 mm Bearing: 360° Datum: AHD Operator: WD
Drilling Information Material Description and Observations
Relative Density
Classification
Pocket DCP TEST
Penetration
Consistency
Graphic Log
Samples Material Description
Penetrometer
Recovery
Condition
Tests soil type: plasticity or particle characteristics,
Moisture
UCS Blows per 100 mm
Symbol
Method
Remarks secondary and minor components, colour
Water
RL Depth (kPa)
(m) (m) 0 5 10 15 20 25
100
200
300
400
500
Silty SAND (TOPSOIL), fine to medium grained, MD
brown, with rootlets
DS Silty CLAY (FILL), medium plasticity, brown, with
0.3-0.7m fine to medium sub angular gravel St
1 CI Silty CLAY, medium plasticity, pale brown,
(NATURAL)
Not Encountered
DS VSt
1.2-1.5m
Augered to 1.6m
AD/T
M
VSt to
2 H
DS CI Silty Gravelly CLAY, medium plasticity, pale 20/90mm
2.1-2.4m brown, fine to medium gravel, tending towards
very low strength phyllite
TECTONIC 3.00.2 LIB.GLB Log 1 TECTONIC BOREHOLE 22244.GPJ <<DrawingFile>> 23/2/2024 10:39 10.02.00.04 Datgel Lab and In Situ Tool - DGD | Lib: Tectonic 3.00.2 2021-03-30 Prj: Tectonic 3.00.2 2021-03-30
H
DS
2.8-3.0m 3
Augered to 3.5m
Hole Terminated at 3.50 m
20/60mm
4
5
6
7
Method Penetration Water Samples and Tests Moisture Condition Consistency/Relative Density
AD/T-Auger Drilling TC Bit VE - Very Easy Level (Date) U## - Undisturbed Sample (## mm) D - Dry VS - Very Soft
AD/V-Auger Drilling V Bit E - Easy DS - Disturbed Sample M - Moist S - Soft
RT - Rotary Tri-cone Bit Inflow BDS - Bulk Disturbed Sample W - Wet F - Firm
RD - Rotary Drilling F - Firm SPT - Standard Penetration Test VSt - Very Stiff
Partial Loss
NMLC -Rock Core H - Hard H - Hard
VH - Very hard Complete Loss
HA - Hand Auger Plastic Limit VL - Very Loose
Graphic Log/Core Loss L - Loose
Classification Symbols and < PL MD - Medium Dense
Core recovered (hatching Soil Descriptions
indicates material) = PL D - Dense
Based on Unified Soil < PL VD - Very Dense
Core loss Fr - Friable
Classification System
Page 13
CLIENT : Mark Kussrow SHEET : 1 OF 1
CONTRACTOR :
PROJECT : Assessment of Existing Dam
LOCATION : 38 Barina Court, Pomona
PROJECT No. : 22244
TEST: DCP1
LOGGED: MO 22/1/2024 CHECKED: MCC
EASTING: 483867.0 m NORTHING: 7081619.0 m
MGA2020 Zone 56
Depth (m)
Blows per 100 mm
0 5 10 15 20 25
1
2
3
TECTONIC 3.00.2 LIB.GLB Log IS DCP 3 PER PAGE 22244.GPJ <<DrawingFile>> 23/2/2024 10:39 10.02.00.04 Datgel Lab and In Situ Tool - DGD | Lib: Tectonic 3.00.2 2021-03-30 Prj: Tectonic 3.00.2 2021-03-30
4
5
6
7
Comments
Page 14
TERMS USED ON LOGS
DRILLING/EXCAVATION METHOD
AD* Auger Drilling RA Rotary Air BH Tractor Mounted Backhoe
ADH Hollow Auger RD Rotary Blade or Drag bit EX Tracked Hydraulic Excavator
HA Hand Auger RT Rotary Tri-cone bit HMLC Core – 63mm
*T TC-Bit HQ Core – 63mm
*V V-Bit NMLC Core – 47mm
NQ Core – 52mm
R Ripper
RH Rock Hammer
WATER
GROUNDWATER NOT The observation of groundwater, whether present or not, was not possible due to drilling water,
OBSERVED surface seepage or cave in of the borehole/test pit.
GROUNDWATER NOT The borehole/test pit was dry soon after excavation. However, groundwater could be present in
ENCOUNTERED less permeable strata. Inflow may have been observed had the borehole/test pit been left open
for a longer period.
SAMPLING AND TESTING
SPT Standard Penetration Test to AS1289.6.3.1-2004
5,4,10 N=14 5,4,10 = Blows per 150mm. N = Blows per 300mm penetration following 150mm seating
30/65mm Where practical refusal occurs, the blows and penetration for that interval are reported
RW Penetration occurred under the rod weight only
HW Penetration occurred under the hammer and rod weight only
HB Hammer double bouncing on anvil
DS Disturbed sample
BDS Bulk disturbed sample
SV Field shear vane test expressed as uncorrected shear strength (sv = peak value, sr = residual value)
PP Pocket penetrometer test expressed as instrument reading in kPa
U50 Thin walled tube sample - number indicates nominal sample diameter in millimetres
DCP Dynamic cone penetration test
CPT Electronic cone penetration test
CPTu Electronic cone penetration test with pore pressure (u) measurement
Rev1
February 2021
Page 15
METHOD OF SOIL DESCRIPTION
USED ON LOGS
CLASSIFICATION AND INFERRED STRATIGRAPHY
Soil is classified and described in borehole and test pit logs using the preferred method given in AS1726 – 2017.
The material properties are assessed in the field by visual/tactile methods.
Particle Size Plasticity Properties
Major Sub Division Particle Size
Division
BOULDERS > 200 mm
COBBLES 63 to 200 mm
Coarse 19 to 63 mm
GRAVEL Medium 6.7 to 19 mm
Fine 2.36 to 6.7 mm
Coarse 0.6 to 2.36 mm
SAND Medium 0.21 to 0.6 mm
Fine 0.075 to 0.21
SILT 0.002 to 0.075
CLAY < 0.002 mm
NOTE: The U line is an approximate upper bound for most materials.
Data which plot above the U line may represent unusual/problem soil
behavior, or unreliable data and should be considered carefully.
MOISTURE CONDITION AS1726 - 2017
Symbol Term Description
D Dry Sands and gravels are free flowing. Clays & Silts may be brittle or friable and powdery.
M Moist Soils are darker than in the dry condition & may feel cool. Sands and gravels tend to cohere.
W Wet Soils exude free water. Sands and gravels tend to cohere.
CONSISTENCY AND DENSITY AS1726 - 2017
Symbol Term Undrained Shear Symbol Term Density Index % SPT “N” #
Strength
VS Very Soft 0 to 12 kPa VL Very Loose Less than 15 0 to 4
S Soft 12 to 25 kPa L Loose 15 to 35 4 to 10
F Firm 25 to 50 kPa MD Medium Dense 35 to 65 10 to 30
St Stiff 50 to 100 kPa D Dense 65 to 85 30 to 50
VSt Very Stiff 100 to 200 kPa VD Very Dense Above 85 Above 50
H Hard Above 200 kPa
In the absence of test results, consistency and density may be assessed from correlations with the observed behaviour of
the material.
# SPT correlations are not stated in AS1726 – 2017, and may be subject to corrections for overburden pressure and
equipment type.
Rev1
October 2017
Page 16
METHOD OF ROCK DESCRIPTION USED ON LOGS
CLASSIFICATION AND INFERRED STRATIGRAPHY
Rock is classified and described in borehole and test pit logs using the preferred method given in AS1726 – 2017.
The material properties are assessed in the field by visual/tactile methods.
STRENGTH
Point Load
Symbol Term Index, Is(50) Field Guide
(MPa)
VL Very 0.03 to 0.1 Material crumbles under firm blows with sharp end of pick; can be peeled
Low with knife; too hard to cut a triaxial sample by hand. Pieces up to 30 mm
can be broken by finger pressure.
L Low 0.1 to 0.3 Easily scored with a knife; indentations 1 mm to 3 mm show in the specimen
with firm blows of pick point; has dull sound under hammer. A piece of core
150 mm long by 50 mm diameter may be broken by hand. Sharp edges of core
may be friable and break during handling.
M Medium 0.3 to 1 Readily scored with a knife; a piece of core 150 mm long by 50 mm diameter
can be broken by hand with difficulty.
H High 1 to 3 A piece of core 150 mm long by 50 mm diameter cannot be broken by hand but
can be broken with pick with a single firm blow; rock rings under hammer.
VH Very 3 to 10 Hand specimen breaks with pick after more than one blow; rock rings under
High hammer.
EH Extremely >10 Specimen requires many blows with geological pick to break through intact
High material; rock rings under hammer.
Relationship between Is(50) and UCS (unconfined compressive strength) will vary with rock type and strength, and
should be determined on a site-specific basis. UCS is typically 10 to 30 x Is(50), but can be as low as 5.
ROCK MATERIAL WEATHERING
Symbol Term Field Guide
Soil developed on extremely weathered rock; the mass structure and
Residual
RS substance fabric are no longer evident; there is a large change in volume
Soil but the soil has not been significantly transported.
Extremely Rock is weathered to such an extent that it has soil properties - i.e. it either
EW
Weathered disintegrates or can be remoulded, in water.
Whole of rock is discoloured, usually by iron staining or bleaching to the
extent that the colour of the original rock is not recognizable. Rock strength
Highly
HW is significantly changed by weathering. Porosity may be increased by
Weathered
leaching, or may be decreased due to deposition of weathering products in
Distinctly
DW pores.
Weathered
Whole of rock is discoloured, usually by iron staining or bleaching to the
Moderately extent that the colour of the original rock is not recognizable; but shows little
MW
Weathered or no change of strength from fresh rock.
Slightly Rock is slightly discoloured but shows little or no change of strength relative
SW
Weathered to fresh rock.
FR Fresh Rock shows no sign of decomposition or staining.
ABBREVIATIONS FOR DEFECT TYPES AND DESCRIPTIONS
Defect Type Coating or Infilling Roughness
CS/CZ Crushed seam/zone (Fault) Ca Calcite Po Polished
DB Drilling break Clay Clay Sm Smooth
EW Extremely weathered seam Cn Clean Sl Slickensided
HB Handling break Co Coating ( > 1mm) Ro Rough
IS/IZ Infilled seam/zone Fe Iron oxide VRo Very rough
Op Open
J Joint
Qz Quartz
Pt Parting St Stain Planarity
SS/SZ Sheared seam/zone (Fault) Vn Veneer (<1mm) Cu Curved
Vn Vein X Carbonaceous Dis Discontinuous
Ir Irregular
Pl Planar
St Stepped
Un Undulating
Rev4
February 2021
Page 17
Construction Sciences Pty Ltd Laboratory: Sunshine Coast Laboratory
ABN: 74 128 806 735 Phone: 07 5452 0100
Fax: 07 5452 0133
Address: Email: [email protected]
32 Hi-Tech Drive,
Kunda Park QLD 4556
QUALITY OF MATERIALS REPORT
Client: Tectonic Geotechnical Pty Ltd Report Number: 3740/R/63629-1
Client Address: 924 David Low Way, Marcoola Project Number: 3740/P/2437
Project: 38 Barina Court, Pomona Lot Number:
Location: Various Internal Test Request: 3740/T/48064
Supplied To: Tectonic Geotechnical Pty Ltd Client Reference/s: O/N 22244
Area Description: Report Date / Page: 1/02/2024 Page 1 of 2
Test Procedures AS1289.3.6.1, AS1289.3.1.2, AS1289.3.2.1, AS1289.3.4.1, AS1289.2.1.1, AS 1289.3.3.1
Sample Number 3740/S/251370 Borehole name BH1
Sampling Method Tested As Received Start Sample Depth (m) 0.3
Date Sampled 22/01/2024 End Sample Depth (m) 0.6
Sampled By Client Sampled (m)
Date Tested 25/01/2024 Material Source Insitu
PSD Preparation Washed Material Type -
Atterberg Preparation Dry Sieved / Oven Dried Prep Material > 53.0mm (%)
Material Description CI Clay, medium plasticity, with sand, with gravel
Specification Percent Specification PARTICLE SIZE DISTRIBUTION GRAPH
AS Sieve (mm)
Minimum (%) Passing (%) Maximum (%)
100
26.5 100
9.5 91
6.7 85 80
4.75 78
Percent Passing (%)
2.36 70
60
1.18 63
0.600 57
0.425 55 40
0.300 53
0.150 49
20
0.075 47
0
6.7
9.5
1.18
2.36
4.75
13.2
19.0
26.5
0.075
0.150
0.300
0.425
0.600
AS Sieve Size (mm)
Specification Specification Specification Specification
Test Result Result Test Result Result
Minimum (%) Maximum (%) Minimum (%) Maximum (%)
Liquid Limit (%) 42 0.075/0.425 Fines Ratio 0.85
Plastic Limit (%) 25 PI x 0.425 Ratio (%) 935.0
Plastic Index (%) 17 LS x 0.425 Ratio (%) 467.5
Linear Shrinkage (%) 8.5 Shrinkage Observations -
Remarks
Accredited for compliance with ISO/IEC 17025 – Testing
Accreditation Number: 1986
Corporate Site Number: 3740
Approved Signatory: Thomas Hewitt
Form ID: W85Rep Rev 3
Page 18
Construction Sciences Pty Ltd Laboratory: Sunshine Coast Laboratory
ABN: 74 128 806 735 Phone: 07 5452 0100
Fax: 07 5452 0133
Address: Email: [email protected]
32 Hi-Tech Drive,
Kunda Park QLD 4556
QUALITY OF MATERIALS REPORT
Client: Tectonic Geotechnical Pty Ltd Report Number: 3740/R/63629-1
Client Address: 924 David Low Way, Marcoola Project Number: 3740/P/2437
Project: 38 Barina Court, Pomona Lot Number:
Location: Various Internal Test Request: 3740/T/48064
Supplied To: Tectonic Geotechnical Pty Ltd Client Reference/s: O/N 22244
Area Description: Report Date / Page: 1/02/2024 Page 2 of 2
Test Procedures AS1289.3.6.1, AS1289.3.1.2, AS1289.3.2.1, AS1289.3.4.1, AS1289.2.1.1, AS 1289.3.3.1
Sample Number 3740/S/251371 Borehole name BH1
Sampling Method Tested As Received Start Sample Depth (m) 3.4
Date Sampled 22/01/2024 End Sample Depth (m) 3.6
Sampled By Client Sampled (m)
Date Tested 1/02/2024 Material Source Insitu
PSD Preparation Washed Material Type -
Atterberg Preparation Dry Sieved / Oven Dried Prep Material > 53.0mm (%)
Material Description CI Clay, medium plasticity, with sand, trace of gravel
Specification Percent Specification PARTICLE SIZE DISTRIBUTION GRAPH
AS Sieve (mm)
Minimum (%) Passing (%) Maximum (%)
100
9.5 100
6.7 99
4.75 98 80
2.36 95
Percent Passing (%)
1.18 90
60
0.600 86
0.425 84
0.300 82 40
0.150 80
0.075 78
20
0
6.7
9.5
1.18
2.36
4.75
0.075
0.150
0.300
0.425
0.600
AS Sieve Size (mm)
Specification Specification Specification Specification
Test Result Result Test Result Result
Minimum (%) Maximum (%) Minimum (%) Maximum (%)
Liquid Limit (%) 42 0.075/0.425 Fines Ratio 0.92
Plastic Limit (%) 23 PI x 0.425 Ratio (%) 1601.7
Plastic Index (%) 19 LS x 0.425 Ratio (%) 800.8
Linear Shrinkage (%) 9.5 Shrinkage Observations -
Remarks
Accredited for compliance with ISO/IEC 17025 – Testing
Accreditation Number: 1986
Corporate Site Number: 3740
Approved Signatory: Thomas Hewitt
Form ID: W85Rep Rev 3
Page 19
Construction Sciences Pty Ltd Laboratory: Sunshine Coast Laboratory
ABN: 74 128 806 735 Phone: 07 5452 0100
Fax: 07 5452 0133
Address: Email: [email protected]
32 Hi-Tech Drive,
Kunda Park QLD 4556
EMERSON CLASS NUMBER REPORT
Client: Tectonic Geotechnical Pty Ltd Report Number: 3740/R/63641-1
Client Address: 924 David Low Way, Marcoola Project Number: 3740/P/2437
Project: 38 Barina Court, Pomona Lot Number:
Location: Various Internal Test Request: 3740/T/48064
Supplied To: Tectonic Geotechnical Pty Ltd Client Reference/s: O/N 22244
Area Description: Report Date / Page: 1/02/2024 Page 1 of 1
Test Procedures: AS1289.3.8.1
Sample Number 3740/S/251370 3740/S/251371
ID / Client ID - -
Lot Number - -
Date / Time Sampled 22/01/2024 22/01/2024
Date Tested 1/02/2024 1/02/2024
Material Source Insitu Insitu
Material Type - -
Sampling Method Tested As Received Tested As Received
Prep Material > 53mm (%) - -
Water Type Distilled water Distilled
Water Temperature (°C) 23 23
Borehole name BH1 BH1
Start Sample Depth (m) 0.3 3.4
End Sample Depth (m) 0.6 3.6
(m)
CI Clay, medium plasticity, with CI Clay, medium plasticity, with
Soil Description
sand, with gravel sand, trace of gravel
Slakes. No dispersion Slakes. No dispersion
Emerson Class Description
Calcite or gypsum present Calcite or gypsum present
Emerson Class Number 4 4
Remarks
Accredited for compliance with ISO/IEC 17025 – Testing
Accreditation Number: 1986
Corporate Site Number: 3740
Approved Signatory: Thomas Hewitt
Form ID: W22Rep Rev 4
Page 20
LIMITATIONS This document has been prepared for the purpose outlined in Tectonic’s proposal and no responsibility is accepted for the use of this document, in whole or in part, for any other purpose. The scope of Tectonic’s Services are as described in Tectonic’s proposal, and are subject to restrictions and limitations. Tectonic did not perform a complete assessment of all possible conditions or circumstances that may exist at the site referenced in the report. If a service is not expressly indicated, do not assume it has been provided. If a matter is not addressed, do not assume that any determination has been made by Tectonic in regards to it. Conditions may exist which were undetectable given that economic and time constraints limit the practical extent of geotechnical investigation. Variations in conditions may occur between investigation locations, and there may be special conditions pertaining to the site which have not been revealed by the investigation and which have not therefore been taken into account in the document. Where variations exist on site, additional studies and actions may be required. Tectonic’s opinions are based upon information that existed at the time that the work was performed. The passage of time, man-made or natural events, may alter the site conditions. It is understood that the Services undertaken allowed Tectonic to form an opinion of the actual conditions of the site at the time the site was visited and cannot be used to assess the effect of any subsequent changes in the quality of the site, or its surroundings, or any laws or regulations. Any assessments made in the preparation of this document are based on the conditions indicated from published sources and the findings of the investigation described. Actual subsurface conditions may differ from those indicated in the document (e.g. between boreholes or test pits). No warranty is included, either express or implied, that the actual conditions will conform exactly to the assessments contained in this document. Where data supplied by the client or other external sources, including previous site investigation data, have been used, it has been assumed that the information is correct unless otherwise stated. No responsibility is accepted by Tectonic for incomplete or inaccurate data supplied by others. This document is provided for the sole use by the Client and its professional advisers. No responsibility whatsoever for the contents of this document will be accepted to any person other than the Client. Any use which a third party makes of this document, or any reliance on or decisions to be made based on it, is the responsibility of such third parties. Tectonic accepts no responsibility for damages, if any, suffered by any third party as a result of decisions made or actions based on this document. Rev 1 (March 2016)