PROPOSED STORMWATER HARVESTING - Hornsby Shire · 2016. 5. 3. · Tel: 02 9888 5000 • Fax: 02 9888 5001 • Email: [email protected] • ABN 17 003 550 801 REPORT TO STORM

Jeffery and Katauskas Pty Ltd CONSULTING GEOTECHNICAL AND ENVIRONMENTAL ENGINEERS

Postal Address: PO Box 976, North Ryde BC NSW 1670 Tel: 02 9888 5000 • Fax: 02 9888 5001 • Email: [email protected] • ABN 17 003 550 801

REPORT

TO

STORM CONSULTING PTY LTD

ON

GEOTECHNICAL INVESTIGATION

FOR

PROPOSED STORMWATER HARVESTING

AT

WAITARA OVAL

PARK AVENUE, WAITARA, NSW

27 October 2010

Ref: 24360Vrpt Waitara

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TABLE OF CONTENTS

1 INTRODUCTION 1

2 INVESTIGATION PROCEDURE 1

3 RESULTS OF INVESTIGATION 3

3.1 Brief Site Description 3

3.2 Subsurface Conditions 3

3.3 Laboratory Test Results 4

4 COMMENTS AND RECOMMENDATIONS 4

4.1 Summary of Principal Geotechnical Findings and Issues and Further Work 4

4.2 Excavation, Groundwater and Retention 7

4.2.1 Excavation Conditions 7

4.2.2 Groundwater 9

4.2.3 Retention and Batter Slopes 9

4.2.4 Lateral Pressures 11

4.3 Site Classification and Foundation Design Guidelines 12

4.3.1 Sandstone Bedrock Foundations 12

4.3.2 Engineered Fill and/or Residual Clay Foundations 13

4.4 General Guidelines on Subgrade Preparation and Engineered Fill 15

5 GENERAL COMMENTS 17

TABLE A: SUMMARY OF LABORATORY TEST RESULTS

BOREHOLE LOGS 1 AND 2

FIGURE 1: BOREHOLE LOCATION PLAN

VIBRATION EMISSION DESIGN GOALS

REPORT EXPLANATION NOTES

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1 INTRODUCTION

Jeffery and Katauskas Pty Ltd have been commissioned by Mr Ben Wolfgramm of

Storm Consulting Pty Ltd to carry out a limited scope geotechnical investigation for

proposed stormwater harvesting system at Waitara Oval, Park Avenue, Waitara,

NSW. The commission was by Acceptance of Proposal Form, Ref. P32423V, signed

on 28 September 2010. Preliminary information based on the field borehole data

were emailed to Mr Wolfgramm on 12 October 2010. This report provides the

laboratory test results and presents the final results of the investigation.

At this concept stage, we were not supplied with details of the proposed works,

with exception of the locations of the stormwater harvesting system within the oval

grounds and that the structures may comprise construction of underground tanks,

gross pollutant trap (GPT) and maintenance access way. Details of tank sizes, base

or excavation levels and loads were unknown.

The scope of the investigation was limited to assessing the subsurface conditions at

two nominated locations as a basis for comments and geotechnical

recommendations on suitable foundation strata with bearing capacities for

underground or above ground tanks, excavation conditions, retention/batters and

comments on the permeability of the subsurface soils and on further geotechnical

work deemed necessary at a later stage.

A summary of the principal geotechnical findings and issues for the proposed

development is provided in Section 4.1.

2 INVESTIGATION PROCEDURE

The investigation included:

1. Electronic Scan for buried services at the two borehole locations, with

reference to ‘Dial Before You Dig’ plans.

Ref: 24360Vrpt Waitara Page 2

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2. The auger drilling of two boreholes (BH1 and BH2) using our JK250

specialised geotechnical drilling rig.

3. The boreholes were set out at locations as close as practical to those

nominated by Mr Ben Wolfgramm of Storm Consulting Pty Ltd in an email

dated 28 September 2010, as shown on Figure 1. The locations were set out

by tape measurements from existing surface features. Location of the

boreholes was partly dictated by access and buried services constraints

imposed by existing site conditions/development.

4. The apparent compaction of fill and strength of the residual silty clay profile

was assessed by Standard Penetration Test (SPT) 'N' values, which were

augmented, where possible, by hand penetrometer tests on cohesive samples

recovered in the SPT split tube.

5. The strength of the sandstone bedrock was assessed from observation of

drilling resistance using a tungsten carbide (TC) bit, examination of the

recovered rock cuttings and subsequent correlation with the results of

laboratory moisture content tests. It should be noted that strengths assessed

in this way are approximate and variances of one strength order should not be

unexpected.

6. Groundwater observations were recorded during drilling and on or shortly after

completion of the boreholes. No long-term groundwater monitoring has been

carried out.

7. Selected samples were returned to Soil Test Services (STS), a NATA

registered laboratory, for moisture content and Atterberg Limits testing; these

results are summarised in Table A. Contamination screening of site soils was

outside the limited scope of this geotechnical investigation.

The fieldwork for the investigation was carried out under the direction of our

geotechnical engineer, Mr David Schwarzer, who was present full-time on site, to set


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out the test locations, log the encountered subsurface profile and nominate insitu

testing and sampling. The borehole logs (which include field test results and

groundwater observations) are attached, together with a glossary of logging terms

and symbols used. For more details of the investigation procedures, and their

limitations, reference should be made to the attached Report Explanation Notes.

3 RESULTS OF INVESTIGATION

3.1 Brief Site Description

The potential tank/GPT sites are located on the north and south eastern perimeters

of the oval as shown on Figure 1 (BHs 1 and 2). The ground slope of the sites is

about 2º down to north. The adjoining grassed oval appears to have been

substantially filled to make it almost level. There is a small gully feature running

across the north-eastern corner of the reserve. Other feature of the general oval site

can be discerned from Figure 1.

3.2 Subsurface Conditions

Reference should be made to the attached borehole logs for details at each specific

location; however, a general discussion of the encountered subsurface conditions is

presented below.

1. Fill was penetrated in both boreholes to depths of about 1m-1.3m. The fill

profile was predominantly silty clay with gravel and sand and roots. The fill

appears variably compacted. This assessment is mostly based on SPT tests

and our observations during drilling, which do not give a precise determination

of in situ densities since they are affected by friction during driving/pushing

(SPT only), the presence of gravel within the fill and the moisture content of

the fill. Nonetheless, they provide a qualitative guide.


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2. Residual Silty Clay was found below the fill in BH1 only. The silty clay was of

high plasticity and hard strength.

3. Sandstone bedrock was found below the residual clay at depth of 2.4m in

BH1 and below the fill at 1m in BH2. In BH1, the sandstone was extremely

weathered and of extremely low strength down to 4.6m; below this it was of

low to medium strength. In BH2, the sandstone was slightly weathered and of

medium strength; high of greater strength bedrock was encountered at base

of the borehole where TC auger bit refusal occurred (1.7m). Note that

strength assessments on the basis of augered samples are approximate (refer

to Section 2).

4. Groundwater was not encountered during and on completion of drilling the

boreholes. However, in BH1 only, a groundwater level was measured at a

depth of 4.7m in BH1 after one hour of completion of drilling. We note that

the groundwater level may not have become stabilised within the limited

observation period.

3.3 Laboratory Test Results

The results of the Atterberg Limits and Linear Shrinkage tests on the residual silty

clays indicated these clays to be of high plasticity and have a high potential for

shrink/swell movements with changes in moisture content. The results of moisture

content tests on selected samples of the bedrock correlate reasonably well with the

field strength assessments.

4 COMMENTS AND RECOMMENDATIONS

4.1 Summary of Principal Geotechnical Findings and Issues and Further Work

As discussed in Section 3.2, the boreholes penetrated fill that was underlain by hard

residual clays in BH1 and by sandstone bedrock in BH2. Sandstone bedrock was

found in BH1 at a depth 2.4m and at 1m in BH2. The sandstone was of extremely


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low strength in BH1 and of medium strength in BH2. Further strength improvements

occurred at 4.6m in BH1 and 1.7m in BH2 (where TC auger bit refusal occurred).

The highest groundwater level measured was at a depth of 4.7m in BH1 after one

hour of drilling completion. Based on these results, we consider the following to be

the principal geotechnical issues to be taken into consideration in the planning,

design and construction of the proposed stormwater harvesting system:

1. The fill appears to be variably compacted, with its upper layers containing

roots like a topsoil. Also, we are unaware of records that document the

manner of placement, compaction specification and control of the fill.

Accordingly, we consider this existing material to be ‘uncontrolled’ fill.

Because of this fill, the site is considered to be Class P in accordance with

AS2870. The fill is deemed unsuitable as a bearing or supporting subgrade

stratum for the tanks, GPT and slabs.

2. The underlying residual silty clays have a high potential for shrink/swell with

changes in moisture content, i.e. Class H in terms of AS2870.

3. Depending on final base levels, the excavations for underground tank

installations will be carried through fill and/or residual clays. However,

excavations deeper than 2.4m in BH1 location and 1m in BH2 location would

encounter sandstone bedrock. The soils and extremely weathered sandstone

as encountered in BH1 will not be self supporting and consequently, full

support of the sides of the excavations will be required by either cutting the

sides at safe batter slopes or by installation of appropriate retention systems

prior to excavation commencing. However, the slightly weathered sandstone

of medium or greater strength as encountered in BH2 from a depth of 1m

would be suitable for near vertical, unsupported excavations, subject to

geotechnical inspections as the excavation progresses.

4. Excavations deeper than 4.7m in BH1 location will encounter groundwater

issues since this is the highest level of groundwater measured in BH1. It is


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possible that this level may not represent the stable groundwater level, which

might be moderately higher, especially after rainfall.

5. Depending on final base levels, around BH1, the tanks may be on residual clay

subgrade which is highly reactive. The most competent foundation stratum

for tanks, GPT and slabs is the sandstone.

6. In general the subsurface profile is considered to be of very low permeability

given that it is mostly composed of silty clay fill, residual clays and sandstone;

hence, absorption capacity of such conditions is very diminished and an

absorption system would not be recommended by us.

At the time of our investigation, only general details of the proposed development

were known. The subsequent earthworks and foundation recommendations are,

therefore, provided in general terms only, and may require revision once exact

development details, such as earthwork levels, final tank and GPT levels, etc. are

finalised.

Although only a limited subsurface investigation was completed, we believe

sufficient information has been gained to be reasonably confident as to subsurface

conditions. However, it will be essential during earthworks and construction works

that geotechnical inspections be commissioned to check initial assumptions about

excavation, foundation conditions and possible variations that may occur between

inspected and tested locations and to provide further relevant geotechnical advice.

Irregular or ‘milestone’ inspections by a geotechnical engineer are often not adequate

for earthworks and foundation works. It is recommended that the Client be made

aware of the need to commission a geotechnical engineer for regular frequent

inspections. The comments provided in this report should be reviewed following

these inspections.

Further comments on the above issues are provided in the subsequent sections of

this report.


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4.2 Excavation, Groundwater and Retention

Excavation depths and levels for the underground tanks and GPTs were unknown or

not advised at the time of report preparation. Also, it is possible that an above ground

tank solution may be chosen. Hence, the following are only general guidelines on

excavation and retention matters, which may need revision at a later stage once the

design concept and details have been finalised.

Depending on final base levels and locations, the excavations for proposed

underground tank installations will be carried through fill and/or residual clays that can

be readily removed using a conventional hydraulic excavator. However, excavations

deeper than 2.4m in BH1 and 1m in BH2 would encounter sandstone bedrock, which

will require the use of rock excavation equipment, in particular where it increases in

strength to low/medium below depth of about 4.6m in BH1 and medium or greater

strength from 1m and 1.7m in BH2.

The soils and extremely weathered sandstone (BH1 only) will not be self supporting

and consequently, full support of the sides of the excavations will be required by

either cutting the sides as safe batter slopes or by installation of appropriate retention

systems prior to excavation commencing. However, the slightly weathered sandstone

of medium or greater strength as encountered in BH2 from a depth of 1m would be

suitable for near vertical, unsupported excavations, subject to geotechnical inspections

as the excavation progresses.

4.2.1 Excavation Conditions

An assessment of the excavation characteristics of the various strata is presented

below. The excavatability of the sandstone and the selection of appropriate

excavation equipment have been assessed on the basis of augered borehole

information. Note that strength assessments based on augered borehole data are


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approximate (refer to Section 2). Assessment of excavation characteristics and

productivity is not an exact science and contractors must make their own evaluation

based on experience with specific equipment. The contractor must make his own

judgement on all of these factors.

The soils and extremely weathered sandstone can be excavated using conventional

earthmoving equipment, such as dozers and the buckets of hydraulic excavators.

For effective excavation, the low or stronger sandstone will require use of rock

breaking/ripping equipment, such as hydraulic rock hammers, dozers, ripping hooks

and/or rotary grinders and rock saws. Excavation of the sandstone bedrock of

medium or greater strength as found in BH2 will present ‘very hard rock’ excavation

conditions, requiring the use of heavy rock breaking/ripping equipment.

If rock hammers are to be used, we recommend that the initial excavation in rock be

commenced away from likely critical areas, e.g. boundaries with adjoining structures,

or sensitive services, with instrumental vibration monitoring undertaken. Guideline

levels of vibration velocity for evaluating the effects of vibration in structures are

given in the attached Vibration Emission Design Goals sheet. If it is found that

transmitted vibrations are unacceptable, it may then be necessary to change to a

smaller excavator with a smaller rock hammer, or to a rotary grinder and/or rock

saws.

Only excavation contractors with experience in similar work using a competent

supervisor who is aware of vibration damage risks and rock face instability issues,

etc. should be used. The contractor should have all appropriate statutory and public

liability insurances.


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4.2.2 Groundwater

Excavations deeper than 4.7m in BH1 location will encounter groundwater issues

since this is the highest level of groundwater measured in BH1. It is possible that

this level may not represent the stable groundwater level, which might be

moderately higher. It should be noted that groundwater levels may rise some

hundreds of millimetres following protracted periods of rainfall. The tanks and GPT

may have to be designed to resist hydrostatic uplift pressures. Groundwater was not

encountered in BH2 location but then this borehole terminated at a relatively shallow

depth of 1.7m due to TC auger bit refusal on high or greater strength bedrock; it is

possible that a groundwater level may be found deeper into the sandstone profile.

4.2.3 Retention and Batter Slopes

The following are general guidelines on support options for the tanks and GPT

excavations.

BH1 Location

The full depth of any proposed vertical excavation should be supported by

installation of shoring/retention systems prior to excavation commencing. Suitable

shoring systems may comprise soldier pile or semi-contiguous pile walls.

Augered grout injected piles (or bored piles depending on results of trials to assess

groundwater issues) may be used for the shoring walls. Piles should be socketed for

an appropriate design depth to maintain wall stability, below the base of the

excavation, including below local foundation and service excavations. We

recommend large capacity drilling rigs with rock drilling or coring equipment be used

to drill the piles. The proposed piling contractor must, therefore, be given a copy of

the final detailed geotechnical investigation report to ensure that appropriate

equipment with sufficient power is brought to site. Piles should be poured


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immediately or at the very latest, on the same day, as drilling, cleaning and

inspection. Special tools should be used to roughen the sides of load bearing pile

sockets in the sandstone. Water should be removed from the base of piles prior to

concreting or the concrete placed using tremie methods.

Another support method would be to cut the sides of the excavation at temporary

batter slopes if these can be accommodated within the excavation perimeter, and

any significant surcharge loads are situated well away from the crest of the batter

slopes. Our preliminary advice is to avoid using battered slopes in excavations deeper

than about 4m or below groundwater levels; instead use rigid pile wall systems.

Battered excavation side slopes should be formed at no steeper than 1 Vertical in 1

Horizontal (1V:1H) in the soils and extremely weathered sandstone. These are

suitable only for maintaining temporary stability of excavation sides during

construction period. Flatter batters of no steeper than 1V:2H would be required

where groundwater is encountered. We expect that battered slopes would be

backfilled upon completion of the retaining wall construction. The batters should

remain stable in the short term as long as surcharge loads (including construction

loads) are kept well away from the perimeter of the excavation. The use of batter

slopes are conditional to the geotechnical engineer inspecting the excavation as it

progresses, in no more than 1.5m depth intervals, to check for any destabilising

defects in the sandstone that may require shallower batters and/or other retaining

measures such as anchors or bolts.

BH2 Location

Similar to BH1 location the soils would require retention or battered at shallow

slopes. However, the slightly weathered sandstone of medium or greater strength as

encountered in BH2 from a depth of 1m would be suitable for near vertical,

unsupported excavations. If vertical excavations are attempted, it is recommended


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that the excavation faces be regularly inspected by a geotechnical engineer every

1.5m depth, to identify any features that require stabilisation or support.

4.2.4 Lateral Pressures

The following are guidelines for lateral pressures for design of shoring/retention

systems.

Lateral pressures for design of cantilevered type retaining walls within the fill and

residual clays soils and extremely weathered sandstone may be estimated on the

basis of a coefficient of active earth pressure of at least 0.35 (assuming a horizontal

backfill surface) and a bulk unit weight of 20kN/m3. Where walls are restrained from

some lateral movements, or where it is deemed important to reduce excavation

induced movements, a greater earth pressure coefficient, K, of at least 0.6 should be

used.

K values may be significantly reduced or ignored in slightly weathered sandstone

bedrock of at least medium strength, but as a prudent measure, we recommend that

a uniform pressure of 10kPa be adopted for support to account for potential defects,

but subject to inspection during the early stages of excavation to confirm

bedding/jointing and revision of lateral restraint if appropriate.

The retaining walls should be designed to withstand some hydrostatic pressure

unless measures are taken to introduce complete and permanent drainage of the

ground behind the wall. All surcharge loads should also be considered in the design

of retaining walls. The aforementioned earth pressure parameters apply to a

horizontal backfill surface and, if inclined backfill surfaces are to be designed, then

the above factors would have to be increased or the inclined section of backfill

should be taken as a surcharge load in the design.


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For the design of walls socketed into the sandstone of at least low strength, it is

recommended that a maximum allowable toe resistance of 200kPa may be used

below the base of the excavation, including footing and service excavations, to resist

the lateral pressure.

4.3 Site Classification and Foundation Design Guidelines

In case the tanks are built above ground, the unaltered site as seen is classified as

Class 'P' in accordance with AS2870 due to the presence of the uncontrolled fill.

Where the fill is stripped and/or replaced with engineered controlled fill then the site

can be upgraded to Class H, although we note that abnormal moisture conditions

could exist after removal of surrounding existing trees, resulting once again in a more

severe Class P site classification. Reference should also be made to AS2870 for

design, construction, performance criteria and maintenance precautions on Class P

and Class H sites.

The most competent foundation stratum at the site is the sandstone. One option is

to support the tanks and GPT on the sandstone bedrock. Another option would be to

support the tanks and GPT on engineered fill and/or the residual clays.

4.3.1 Sandstone Bedrock Foundations

The following criteria are recommended geotechnical parameters for design and

construction on the sandstone:

1. If the sandstone is exposed by excavations then the tanks foundation systems

may be checked against an allowable bearing pressure (ABP) of 700kPa when

founded into the sandstone of at least extremely low strength.

2. Alternatively, if higher pressures are desired or if the excavation is taken

deeper to reach the sandstone of low strength (i.e. deeper than 3.5m) then

the ABP may be increased to 1200kPa.


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3. In BH2, an ABP of 1500kPa may be adopted for the slightly weathered

sandstone of at least medium strength. It is possible that much higher bearing

pressures may be adopted in this quality sandstone but this would have to be

confirmed by completing cored boreholes together with strength testing of

recovered sandstone rock cores and examination of defects.

4. An allowable shaft adhesion (ASA) of equivalent to 10% of the above ABP

values may be adopted for design of pier sockets, in compression, through the

sandstone. For uplift or tension, the aforementioned ASA value should be

halved. The shaft adhesion values are recommended on condition that

cleanliness and roughness of pier sockets and bases are achieved.

5. For piers socketed into the deeper sandstone, large capacity drilling rigs with

rock augers would have to be used. Deep sockets should be avoided in the

location of BH2 below 1.7m due to difficulties expected in drilling the high or

greater strength bedrock below this depth (note the TC auger bit refusal).

6. All loose or softened debris should be cleared from the base of all foundation

bases prior to concreting. All foundation concrete should be poured

immediately after excavation/drilling, removal of water, cleaning and

inspection.

4.3.2 Engineered Fill and/or Residual Clay Foundations

An option that may be adopted for the tanks may comprise an above ground option

and then the following guidelines on foundations would be applicable. Another

situation where these guidelines would apply would be if the underground tank

excavation option is of limited depth whereby it does not extend down to the

sandstone and ends in the residual clay.

The existing fill is deemed unsuitable as a bearing stratum for the tanks, GPT or any

other structural footings and slabs. All ‘uncontrolled’ fill may be excavated and


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replaced with controlled, engineered fill. The replacement should extend to at least

1m beyond the boundaries of the loaded area.

After the above replacement with engineered fill, a stiffened raft slab or beam

footings may be founded in the new controlled fill mass and/or the residual clay,

with a maximum allowable bearing pressure of 100kPa. This footing system should

be designed by engineering principles to resist the potential shrink/swell movements,

which are normally 40mm-70mm (free surface movements) in Class H clay sites in

accordance to AS2870. The guidelines given in AS2870 for a Class H site may also

be of assistance in designing the footings. The edge and internal beams of the raft or

beams may be designed for an allowable bearing pressure not exceeding 200kPa

when bearing on the residual clay of at least very stiff strength. Reference should

also be made to AS2870 for design, construction, performance criteria and

maintenance precautions on Class H reactive clay sites.

We note that abnormal moisture conditions could exist after removal of existing

trees, resulting in a more severe Class H or even Class P site classification; further

comments on this issue are provided in Section 4.3.

The foundation base or excavation should be inspected by a geotechnical engineer to

ascertain that the recommended foundation material has been reached and to check

initial assumptions about foundation conditions and possible variations that may

occur between borehole locations. The need for further inspections can be assessed

following the initial visit.


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4.4 General Guidelines on Subgrade Preparation and Engineered Fill

The following are general guidelines mostly to do with treatment of existing site fill;

clearly such treatment is only necessary if the existing fill is to act as a bearing or

supporting foundation or subgrade.

The existing fill is considered to be “uncontrolled” and is considered unsuitable as a

bearing or subgrade stratum for footings/foundations and slabs. We recommend that

the existing fill be fully excavated, then the base of the excavation proof rolled and

the fill re-compacted with at least Level 2 control to an engineering standard. The

latter operation should be implemented under any foundation/slab area and under any

movement sensitive pavements and to a distance of about 1m beyond its loaded

perimeter. In other words, any fill under all slabs must be engineered, controlled fill.

Following excavation for removal of the existing fill or root affected or deleterious fill

or excavation to achieve design levels for the new pavement, the exposed subgrade

should be proof-rolled. Proof rolling should be completed using a vibratory, smooth

steel drum roller of say 8 tonne deadweight. The final pass should be undertaken

without vibration and with the presence of a geotechnician or geotechnical engineer.

The objectives of the proof-rolling are to improve the near-surface compaction of the

subgrade and to assist in detection of any unstable areas. Care should be taken

when operating compaction plant as ground vibrations may be directly transmitted to

sensitive services and structures; possibly the vibrations will need to be reduced or

ceased in these areas.

Any unstable (heaving or wet) areas identified during proof-rolling should be locally

treated or further investigation (eg DCP testing) carried out to determine the extent

and nature of such areas. After proof-rolling, the stable areas may be backfilled with

controlled, engineered fill. The use of lime/cement to dry out and stabilise wet and

soft subgrade or the use of geogrids to act as a bridging and separation layer over

the softer materials may be required before placing and compacting a granular


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capping layer. We expect that further advice and inspections will be required to

assess the most suitable method of subgrade improvement. Allowance should be

made for either, tyning, aerating and drying the subgrade, or removal and

replacement with a select imported fill, or lime/cement stabilisation.

Engineered fill should preferably comprise well-graded granular material (ripped or

crushed sandstone), free of deleterious substances and having a maximum particle

size of 75mm. The well-graded granular fill for backfilling excavations should be

compacted in layers of not greater than 200mm loose thickness, to a density of at

least 98% of Standard Maximum Dry Density (SMDD) or equivalent standard.

The on-site fill may be re-used provided unsuitable (‘over-wet’ and ‘over-size’)

material and any deleterious material, including root affected or organic material, is

excluded. However, we do not recommend the reuse of on-site residual clays due to

their high plasticity and reactivity. Any clay soil should not be used as fill and a

geotechnical engineer should approve any cohesive soil prior to use.

Density testing should be carried out at the frequencies as recommended in AS3798-

2007 “Guidelines on Earthworks for Commercial and Residential Developments” but

at least one test per fill layer per 500m2 or three tests per layer per visit, whichever

is the greater. At least Level 2 testing of earthworks should be carried out in

accordance with AS3798. Preferably, the geotechnical testing authority should be

engaged directly on behalf of the client and not as part of the earthworks contract.

In view of the high reactivity potential of the residual silty clay particular attention

should be given to providing adequate drainage both during construction and for long

term site maintenance. The principal aim of the drainage should be to promote run-

off and minimise ponding. The clay subgrade may become untrafficable when wet.

Placement of a blinding layer of durable granular fill or sub-base material to provide a

trafficable surface during construction may be necessary or desirable. The


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earthworks should be carefully planned and scheduled to maintain cross-falls during

construction. We recommend that reference be made to AS2870 for drainage and

vegetation precautions on Class “H” (highly reactive) site.

The earthworks recommendations provided here should be complemented by

reference to AS3798.

5 GENERAL COMMENTS

The recommendations presented in this report include specific issues to be addressed

during the construction phase of the project. As an example, special treatment of

soft spots may be required as a result of their discovery during proof-rolling, etc.

In the event that any of the construction phase recommendations presented in this

report are not implemented, the general recommendations may become inapplicable

and Jeffery and Katauskas Pty Ltd accept no responsibility whatsoever for the

performance of the structure where recommendations are not implemented in full

and properly tested, inspected and documented.

The long term successful performance of floor slabs and pavements is dependent on

the satisfactory completion of the earthworks. In order to achieve this, the quality

assurance program should not be limited to routine compaction density testing only.

Other critical factors associated with the earthworks may include subgrade

preparation, selection of fill materials, control of moisture content and drainage, etc.

The satisfactory control and assessment of these items may require judgment from

an experienced engineer. Such judgment often cannot be made by a technician who

may not have formal engineering qualifications and experience. In order to identify

potential problems, we recommend that a pre-construction meeting be held so that

all parties involved understand the earthworks requirements and potential difficulties.

This meeting should clearly define the lines of communication and responsibility.


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Occasionally, the subsurface conditions between the completed boreholes may be

found to be different (or may be interpreted to be different) from those expected.

Variation can also occur with groundwater conditions, especially after climatic

changes. If such differences appear to exist, we recommend that you immediately

contact this office.

This report provides advice on geotechnical aspects for the proposed civil and

structural design. As part of the documentation stage of this project, Contract

Documents and Specifications may be prepared based on our report. However, there

may be design features we are not aware of or have not commented on for a variety

of reasons. The designers should satisfy themselves that all the necessary advice

has been obtained. If required, we could be commissioned to review the

geotechnical aspects of contract documents to confirm the intent of our

recommendations has been correctly implemented.

A waste classification will need to be assigned to any soil excavated from the site

prior to offsite disposal. Subject to the appropriate testing, material can be classified

as Virgin Excavated Natural Material (VENM), General Solid, Restricted Solid or

Hazardous Waste. If the natural soil has been stockpiled, classification of this soil as

Excavated Natural Material (ENM) can also be undertaken, if requested. However,

the criteria for ENM are more stringent and the cost associated with attempting to

meet these criteria may be significant. Analysis takes seven to 10 working days to

complete, therefore, an adequate allowance should be included in the construction

program unless testing is completed prior to construction. If contamination is

encountered, then substantial further testing (and associated delays) should be

expected. We strongly recommend that this issue is addressed prior to the

commencement of excavation on site.

If there is any change in the proposed development described in this report then all

recommendations should be reviewed.

CONSULTING GEOTECHNICAL AND ENVIRONMENTAL ENGINEERS A.C.N. 003 550 801

VIBRATION EMISSION DESIGN 'GOALS

German Standard DIN 4150 - Part 3: 1986 provides guideline levels of vibration velocity for evaluating the effects of vibration in structures. The limits presented in this standard are generally recognised t o be conservative.

The DIN 4 1 5 0 values (maximum levels measured in any direction at the foundation, OR, maximum levels measured in (x) or (y l horizontal directions, in the plane of theuppermost floor), are summarised in Table 1 below.

I t should be noted that peak vibration velocities higher than the minimum figures in Table 1 for low frequencies may be quite "safe", depending on the frequency content of the vibration and the actual condition of the structure.

It should also be noted that these levels are "safe limits", up t o which no damage due t o vibration effects has been observed for the particular class of building. "Damage" is defined by DIN 4150 t o include even minor non-structural effects such as superficial cracking in cement render, the enlargement of cracks already present, and the separation of partitions or intermediate walls from load bearing walls. Should damage be observed at vibration levels lower than the "safe limits" then it may be attributed t o other causes. DIN 41 50 also states that when vibration levels higher than the "safe limits" are present, it does not necessarily follow that damage will occur. Values given are only a broad guide.

Table 1 DIN 4150 - Structural Damaqe - Safe Limits for Buildinq Vibration

Note: For frequencies above 100 Hz, the higher values in the 50 Hz t o 100 Hz column should be used.

Ref: F1661 March 1999