coffey• geotechnics SPECIALISTS MANAGING THE EARTH

Fraser Thomas limited PO Box 23 273 Hunters Corner Auckland 2155

13 August 2008

Attention: Mr 5 Finnigan

Dear Sean

RE: Proposed Stormwater Treatment Pond at Area 6A and 68 Takanini

1 INTRODUCTION

FolloWing your recent request we have completed our geotechmcal assessment relating to the design and construction of the proposed Stormwater Treatment Pond at the above site and generally in accordance with the Auckland Regional Council (ARC) Publication TP109 "Dam Safety Guidelines". It is understood that the pond will be located in the north-west comer of the proposed development as shown on the appended plan.

It will be constructed mostly from cuts of up to approximately 2.5 metres, however fill batters of up to approximately 2.5 metres will need to be constructed to form the northern pond batter

The details provided to us indicate that the pond embankments will have a crest reduced level of 13.5 metres and the base will have a reduced level of 10.5 metres. Dunng a 1 in 100 year storm event the reduced level of the water in the pond is calculated to reach a maximum of 13.12 metres

2 FIELDWORK AND FINDINGS

The attached cross sections were measured on site and represent the extsting ground profile. It is understood that the flat area in the vicimty of the proposed pond is at a reduced level of approximately 13 metres and our analyses have been based on this.

Anticipated subsoil conditions in the vicimty of the proposed pond have been determtned based on previous hand auger boreholes carried out by this Consultancy (March 2006) and Woodward­Clyde (NZ) Limited (February 2000) as attached. The boreholes encountered soft to hard clayey silts and silty clays with occasional organic inclusions at depth.

Here the thickness of the inorganic raft is variable and significantly organic materials may be encountered away from the borehole locations

The borehole records indicate that the depth to groundwater in the immediate vicinity of the proposed pond varies from 1.1 metres to 3.3 metres below ground level.

Coffey Geotechnlcs (NZ) Limited GEOTNEWP12635 10 Lion Place Epsom 1023 Auckland New Zealand PO Box 9924 Newmar1<et 1149 Aucl<land New Zealand T (+64) (9) 523 5626 F (+64) (9) 523 5627 www coffey.com/geotechnics

GEOTECHNICAL ASSESSMENT .:

3 SLOPE STABILITY

Based on soil type and shear vane dial readings the following parameters have been assessed to be appropriate for the materials encountered on site:

TABLE 1: SOIL PROPERTIES

Description c· "' (kPa) (degrees)

Stiff certified clay filling 10 32

Soft to stiff alluvial materials 5 25

Cross-section A-A was constdered to be the worst case scenario and so was analysed using the Morganstern Price method for circular slips The analyses assessed the worst case groundwater conditions (ie. 1 in 100 year flood level} and determined the lowest factor of safety under these conditions as well as during normal working conditions.

Full details of the stability analyses are shown on the appended computer stability result sheets (Figures 1 to 4) and a summary of critical cases is presented in the following table:

TABLE 2: MINIMUM FACTORS OF SAFETY

Case Conditions of Analysis (on Cross-Section A-A) Factor of Safety

Fully saturated ground conditions after development with minimal fill 1 operations, external batter at approximately 45 degrees - worst case <1

scenario (Figure 1)

Fully saturated ground conditions after development Wlth certified fill 2 embankment, external batter at approxtmately 19 degrees - worst case 1 2

scenano (Figure 2)

Assumed long-term groundwater conditions after development with 3 certified fill embankment, external batter at approximately 19 degrees 1.5

(Figure 3)

4 Rapid drawdown condibons to assess internal batter stability at a >2 gradient of 1 in 4 - worst case scenario (Figure 4)

The above calculations have been carried out with the internal batters of the pond at gradients of 1 in 4 (14 degrees) which is considered the maximum gradient they can be at while maintaining adequate long term factors of safety.

As can be seen from the table 2 results (case 1 ), if cut to fill operations are minimised as much as possible with external batters at approximately 45 degrees, then under fully saturated conditions (during a 1 in 100 year flood) mintmum factors of safety drop below 1 indicating slope failure and the reqwement for eastng of the external batter slopes to flatter grad tents. The slip circle in case 1 extends through the batter filling into the lower strength alluvial materials beneath indicating that the existing ground here needs to be replaced with engineered filling to resist failure on this slip circle.

In case 2. the northern (stream side) embankment has been formed entirely from certified fill (as indicated by the stability results of case 1) with external gradients reduced as much as possible to approximately 1 in 3 which results in a minimum factor of safety of 1.2 being calculated under fully saturated conditions. TP1 09 guidelines suggest maximum batter slopes of up to 1 in 2.2

Coffey Geotechnics GEOTNEWP12635 13 August 2008

2

GEOTECHNICAL ASSESSMENT

Case 3 shows case 2 under assumed long-term groundwater conditions and demonstrates that a factor of safety of 1.5 should be available as requ1red.

Case 4 assesses the internal batter stability under temporary rap1d drawdown cond1t1ons whereby the pond is rapidly drained (e.g. maintenance) while the batters remain saturated for a short time. This represents the worst case scenario here and has returned a calculated factor of safety greater than 2 which is satisfactory

Factors of safety of between 1 2 and 1 5 are undesirable in the long term, although they would be acceptable here under such temporary extreme groundwater conditions.

4 PROJECT EVALUATION AND RECOMMENDATIONS

4.1 General

Our findmgs ind1cate that the site is generally suitable for the proposed stormwater treatment pond provided the following spec1fic comments and recommendations contained herein are adhered to, which are generally aligned with TP109 gUidelines.

4.2 Northern Berm Construction

To limit flows beneath the northern batter a seepage control (cut off) key of eng1neer certified fill approximately 1 metre below the pond invert, 3 metres in w1dth and extending the length of the ponds north em boundary should be created generally in accordance with section 3.2 of TP1 09 (attached). The batters of this cut off key should be no steeper than 1 in 1 (45 degrees).

Toe drainage should also be provided at the base of the external toe slope to minimise the risk of piping failure. We consider that this should take the form of a hardened toe of the embankment comprising a suitable hardfill (GAP40). See TP109 figure 3.7 (attached).

Although not shown to be necessary in the slope stability analyses the mmimum w1dth of the crest as required by section 3.3 of TP109 (attached) is 3 metres or 4 metres if it is to be used as a crossmg and should be suitably protected using hardfill.

The maximum internal batter gradient is assessed to be 1 in 4 (14 degrees) and the maximum external batter gradient is approximately 1 in 3 (18 degrees).

Given the measured groundwater levels it should be expected that temporary groundwater control measures may be required during pond construction. Th1s may include but is not lim1ted to the use of sumps and pumps. In any event an assessment in this regard would need to be made during construction.

As discussed below the near surface site materials are generally assessed to be suitable for use as filling but as they are of low plasticity and typically comprising silts. Permeability values of these materials will need to be assessed by laboratory testing. Depending on the results it may be necessary to place a clay or synthetic liner (eg. Bentafix) on the mternal batters and base of the pond to minimise seepages and erosion. Generally speaking the clay liner should be at least 0.6 metres thick If a synthetic liner is used it will need to be protected by a rock armour covering approx 150mm thick (gab1on rock grade or similar) so that pond maintenance can be carried out without damaging the pond liner.

If a liner is to be used given the existing groundwater levels it may also be necessary to install groundwater drainage measures around the perimeter of the pond to relieve external pressures on the impermeable liner.

For clay liners we should be given the opportumty of Inspecting the imported clay pnor to placement to check its suitability for use here.

Coffey Geotechnics GEOTNEWP12S35 13 August 2008

3

GEOTECHNICAl ASSESSMENT ~

Precautions should also be taken to ensure that the embankment IS not over-topped by an appropriately designed sp1llway I structure

4.3 Earthworks

Prior to earthworks being carried out. the surrounding v1c1nity should be cleared of vegetation. Topsoil should be stripped from all cut and fill areas, with stnppmg operations being planned to extend well beyond cut and fill boundaries to avoid peripheral fill contamination Stockpiles of topsoil and unsuitable materials should be sited well clear of the works on suitable areas of natural ground.

It is anticipated that the cut matenals will be suitable for use as fillm the northem pond berm and across the remainder of the site with conditioning, however if deposits of unsUitable matenals (eg. organics) that are considered unfit for reworking are 1dent1fied, they should be undercut and disposed of off the site or on topsoil stockpiles if appropriate.

Due to the typtcally variable nature of the s1te materials, allowance should always be made for the presence of layers of soft sensitive materials, together with groundwater, especially in the deeper cuts These can cause problems for earthmoving plant but usually the matenals become suitable for inclusion m the earthworks after conditionmg.

All benching of slopes prior to the placement of filling should be m accordance with the normal requirements of NZS 4404 and related documents and should be the subject of Engineering inspections.

4.4 Compaction Control

We propose that compactiOn control is pnncipally m terms of m1n1mum allowable shear strength and maximum allowable air voids criteria.

Based on our experience, we recommend 6% maximum allowable air voids and a minimum allowable shear strength of 140kPa. However, standard compact1on testing (and permeability testing) for the borrow materials is recommended prior to construction

The insitu moisture content of the borrow materials is expected to be slightly higher than the optimum motsture content for maxtmum compaction. However. our expenence will dam fills indicate that materials placed and compacted slightly 'wet of optimum' are preferred. Therefore, minimal conditioning of the fill materials is considered necessary prior to placement and compaction .

Compaction of the filling should be carried out to certifiable standards (NZS 4431) w1th conventional plant and should be under Engineenng control. The Engtneer should not only be g1ven every opportunity to inspect all materials prior to placement, but also to ensure adequate compaction is being achieved throughout the works

4.5 Outlet Conduits

To avoid pip1ng erosion, conduits runnmg beneath the pond should be kept to an absolute minimum. Where they do run beneath the pond bunds then conventional seepage collars should be constructed at regular mtervals along the pipes as recommended in TP1 09 Figure 2.3 (attached).

Careful compaction and backfilling will be required around all pipes and in the pipe trenches to eliminate the possibility of future ptping erosion. A specification for such works should be included with the design and construction drawings.

Coffey Geotechnics GEOTNEWP12635 13 August 2008

4

GEOTECHNICAL ASSESSMENT •

4.6 Plan Review and Inspections

Due to the preliminary nature of the pond proposal we would like to be given the opportumty to rev1ew the final plans and revisit our evaluations and recommendations as necessary

Careful construction observations must be undertaken during construction and appropnate an appropriate Geotechnical Complet1on Report should be prepared confirm1ng the work has been completed m accordance w1th the recommendations contained herein and the general gUidelines ofTP109

Fmally, 1t should be noted that the above analyses have been based on boreholes which by their nature only prov1de mformation about a relatively small volume of subso1ls. there may be spectal conditions pertaining to this site which have not been disclosed by the investigation and so our continued Involvement 10 the des1gn and construction of the pond IS recommended

In any case. tf vanations 1n the subsoils occur from those described or assumed to ex1st then the matter should be referred back to us tmmediately.

5 LIMITATION

This report has been prepared solely for the use of our client. Takanini Structure Plan Area 6 Um1ted thetr professtonal advisers and the relevant Territonal Authorities tn relatton to the specific project described herein No liability is accepted in respect of its use for any other purpose or by any other person or enttty All future owners of thts property should seek professtonal geotechnical advtce to satisfy themselves as to tts ongomg suttab11ity for thetr intended use

If you have any further quenes or comments, please do not hesitate to contact the understgned.

For and on behalf of Coffey Geotechnics (NZ) Limtted

0 A Tookey

ProJect Geotechntcal Engineer

Authorised By·

.,:L~~t% tr s GLander

Office Manager MIPENZ. CPEng

Copies to Nigel Hosken Hosken & Assoctates Um1ted P.O Box 99387 Newmarket 1149

Revoe~By

l !eaumont Sentor Geotechntcal Engmeer

Peter Rawson Harnson Gnerson Consultants Limited P 0 Box 5760 Wellesley Street 1141

Attachments Woodward-Clyde (NZ) limited Borehole Records (February 2000) Coffey Geotechnics Borehole Records

Coffey GeolechntCS GEOTNEWP12635 13 August 2008

Site Plan and Cross-Sections Stability Analyses Results TP109 Supplementary Notes

5

Appendix 1 Woodward-Clyde (NZ) Limited

Borehole Records (February 2000)

... "' .... tt ... C) ::> <

I

IDA Woodward-Clyde ., DRILL HOLE LOG WCHA200

Wooow..a-Ct)'lle (KZIUO I Pnone 09 355 1 JOO Project No • Project Reference: 3M Oueon Stteet Auc:ldan4 : Fa. 09 355 1333

AAAA27 4 7000007/002 Takaninl Structure Plan Oril"'9 Conlnetor.

onn Type. lOQ9•0 8y NS ~nd Ll RelatiVe Level mRL ClteOI

SOmm Handauger Chec:keo ay MH Coo<OIMICJ mN

O~leS~ 4·2..00 mE P;pakur; District Council

OateF~n<~· 4-2..00 Permit N~

. lr 'ii z

§: Q. w 0 w ~ Q. ~r;. w GROUND lr{:: :[ >- z c(l: :!~ SAMPLING WATER wu 1- WI- oz 1-;:, DESCRIPTION OF STRATA UJ

::> J:(.!) c:- AND OTHER DATA AND Ulo: A: !) .J

I cr (/)z I-(/) TES71NG ~~ ~ z

Q. .J ow w~ COMMENTS Q(l) Q. w ~ .J .Ja: zo NZ UJ

(.!) c( ~ ~Iii W.J !!:!O 0

UJ (/) 0 c. co a..o

0 .J - v-v. S~c:.k peaty ~nd oranoe Stll. (FILL)

'()."().

~'().. f.o-'0. '().'().,

'().'().

'Co.'¢. k>-'0.

X • Brown orano• SILT mtxed grey stigMy moosl. firm anlino X X JALLUVIALSJ X .

1- 70122 r X " X .. " . • " X •

" " • X

• • . • • X X • • " • " 58119 • X . X

• " • . • " .. • • .. . .. '-- 77132 f--1 • " " .. G t.om, becomes mo/51 • " X " • " • • . " .. ..

• " . • 0 1.2m. ~comes ~ht cream grey, • .. • " • " . " • " • " • " 50116 . " . .. • X

~ • " GWl@1.Sm . X

• " From t.Sm oc:c:uional s!lea~s bleck pelf . 4/VOO " • y •

" . - - - Cream CLAY plastic:. mc.tst. moderately firm dnllng - -- - -5&135 - -- - -- -- -- -- -- - from 1.8m oc:c:uoonll peat ;u sp0119y brown wood lragments - - -- ---- -- -- -- -- f--2 - -- -- -- -- -64136 - -- -- - -- -- - -

EOB@l2.2m:T ARGET OEPTH

REMARKS: I} Shear Vene OP.2918 i) Boretlole Joc.aleC -o• 200m beyond the ~west end o1 Takantnt School Road

•> SCIUbby area Wf1ll rough $Urface suggesllllg veneer o/1•1

Sheet 1 of t

I

t

/-Jz 11'iS (!)~

Oc: .JO 011)

,ww <!>O

!

..J _, u:

Ill ..J

~ ..J

~ 0. ::;:)

0 c:: 0

~ z ~ ::> <( ... !:2 z <S cr 0 z 0 2

I

j

.J r

-'

Woodward~Ciyde 'W' DRILL HOLE LOG WCHA204

'M>oow.,o.(:lyde fNZ\ Ltc I Phone 00 J$S :300 ProjeCI No PI'Ofecl Reference·

J6.S o ....... Sir-~.,.. Fru. 09 J5S !3lJ

AAAA27 4 7000007/002 Takanini Structure Plan Drilling Conua<:tOr

Onl Type I Logge<l By- NS ~nd LL I Relative \.evef mRL Cliet~l

SOmm Handaug•r Checkeo 3y; MH 1 COOidinates mN

I Dale Stalled 11·2·00 I mE Papakura District Council

Oate Ftntsne<:· 11·2.00 Penn~Nc·

r

I - « I z ~ w UJ §: · c:::X f-

0 c. GROUND a:-

I >- • :c:i :=' w- SAM? LING wf-f- z : ~ 5 ~ e AND orHe

WATER f-(.) DESCRIPTION OF STRATA ::::l R DATA AND -w - c 0:: r- I ~~~ · ;:i ffi I t;;! I TEsnNG -J ot:i a. z a. -J COMMENTS w

-J NZ l!J

I ..J:r zo/ ::! 2 c( (/) Cl -

)

-

-

!:!:!f- W...J 1.:. V) :l. Q)

I I

i . IC5138

I

I I

I lC21~0 I

I

I

~ ~0150

GW..@1.1m 1112/00

!!dO c.(.).

I l

1-1

~

0

(J w _,

;..~;_.

~ ~

~ " " " " " . " . " " .

" " " . " " . " " . . . >< X

X X

" " " . X X

" " " " X X

" " " " " " " .. " " .. " . " " /( X X

" . . " " . . " . " .. " " . X X X X . . X X

" .

TOPSOIL

Dark brown otange SILT Ofy, stiff lltiD111g· {TAURANGA GROUP ALLUVIAlS)

- __ - Ught grey ClAY Moosl, harlf driling

t-_-_­t-_-_-

~ I I E08@2.2m Tlo.RGET DEPTH

~ u

Sheet 1 u1 1

-JZ <0 u-_f-

8~ -J(.) O<n ww (!)c;

g ll ~r-~~--~~--~--~------~--------~--~--~--~------------------------------------~----. :'; REMARKS· i) Shear Vane DR2918 ~ iiJ r opoorapny loMylng, nsing slightly to NQ(1h

§ N z u

-I ~ I Woodward-Clyde DRILL HOLE LOG WCHA205 I .r

WoO<lW.,<I-Ct,oe (NZl Lid I Pnono 09 35~ 1300 Project No.: Protect Reference·

J8S Ou•er S~ool AuolllonQ Fax ~:lSI ~3J3

~2747000007/002 Takaninl Structure Plan :lofting Comractor

Orlll iype. toggeo iJy; N$ ;and Ll Retatlvt Levet

50mm H3ndi1Uger Checkee 3y: MH Coorninaces

:>ace Staned· 17-2·00

Dille ~inished' 17-2.00 Penntt No

if I r I ~i ~ GROUND a:~ ~ I' z ,. ~~ ~g SAMPLING WATER ~g :[ w ::J :r <.!l a:: AND OTHER OA TA AND w a: :r ..J a:: • <ll z 1-w ;;? T~STING ~ 1- I-ll. • ..J I 0 :.lJ > c: COMMENTS 0 (f) a. ~ I ~

1 uja:: ass ~~ ~

V) ' 0 u::tn C.CJ o.u -~~-~~~---+---~~-----+------~~-Ov

I

77128

-

57135

70140

-

71138

GWl@1.lm 1712100

~1

-2

mRL

mN

mE

0 z w (.!) w ....J

Chenr

Papakura Distnct Council

DESCRIPTION OF STRATA

% TO?SOfL

~ ~

. -" " - K " . . "

·,.)C. )C

,.",." " " .. " " " )< "

" " " l(

" " " " ·,.",." ,."~" " " " " " " I( X

" " " X

" " " " l( )C

" " . " l( " " . . " " " >< X " . . " " " " "

----·

- . _,

Black brown organic CLAY: Fttm, moist

Org&nic content comprises amorphous matrix mater!.l

Lrghl grey CLAY, 111m

EOBfo!!l2 2m: TARGET DEPTH

Shaec 1 ell

Q z t; a:: 0

u

~ a:: 0 z 0 z

~r-~~--~----L---~-------L ______ _L __ _L __ _L __ ~------------------------------------L-~ ~

" ~ REMARKS: i) Sheer Vane 0Rl918

Appendix 2 Coffey Geotechnics

Borehole Records

Client: Takanlni Structure Plan Area 6 Llmlted Auger Borehole No. 25

Sheet Project Location : Area 6A & as Plan Change Takanlni Structure Plan

Job Number: Dnlled By: II"Tocesaeo tiY-

12635 PMS DAB

Borehole Location:

mN

DescnpUon:

j mE I Ground R.L.

Refer to site plan

SOIL DESCRIPTION

TOPSOIL

NATURAl Sblf, non-plastic. brown slightly line sandy SILT

Stiff, slightly plastic, Ught bfown streaked orange! bfown slightly nne sandy slightly clayey SILT

- becoming orange/ brown streaked fight grey/ white

S_tltf, moderately.f!.astlc, or~~ t>town ttreaked light grey/ white slightly hne sandy slghUy clayey SILT, wHh occaalonal minor woody Inclusions - b8c0mlng light orange/ brown streaked light grey

--sillf, very}ll_asllc, fight orange/ brown streaked light grey silly CLAY, wtlh occasional minor to moderate woody inclusions

Stltf, moderately.plas1rc, light orange/ brown streaked grey fine sandy aayey SILT • becom4ng brown

• becomlllg son, damp

E.O.B. al 3.0 metres.

E aJ 0!~ j

t=t> ij...J

~J fi ~.9J & 0 ~

~ ~~:':': X· X· X· *>~t:*:· 138

~~~ ~0.5

~~~ ~88 119

~~~ ~ 1.0 i4'\l\l

m 120

§~ ... 1.s 82

8>:.<>:.< t-

·-•-•:-! [@~

.... 2.0 84 ~-·-·-~ t-_,. ___

t-

18~~ 90 >:.<>:.<

~~~ ~2.5

~~~ 30 ~>:.<>:.< XX

~88 3.0 30

~ 3.5

.. 4.0

~4.5

~5.5

...

~FOUNDATION ~~ N 8 I N I ' l I N 0

Comments: Borehole Diameter. Topsoil ~~ Sand ... Sandstone Groundwater nOI encountered 50mm Fll V/h GRY81 ::::::: s Isms

~ --- Organic ~;;..; Clay --- Unestone ---

Silt XXX> Punice .::::: VolcaniC

~ -> ~)

(/)

9.2

66

2.9

2.2

1.9

21

1.4

1.S.

• • • . . .. zzz

vvv

25 ot 31

~ate:

3.3.06

Sample and La bora to~ Test

Oetals

Pkllonlc +++ , ......... No Cere

Client : Project Location :

Job Number:

Borehole Location:

mN

Description:

Takanlm Structure Plan Area 6limited

Area 6A & 68 Plan Change Takanlnl Structure Plan

12635

I mE I Ground R.L.

Refer to s1te plan

SOIL DESCRIPTION

TOPSOIL NATURAL Slllf, noni)lastic, blown slightly fine sandy SILT

Still, slightly plastiC, orange streaked light blown sfigNiy clayey very line sandy "SILT

• becoming lltm

• becoming Ughl grey orangol brown

• becoming orange/ brown and limonite stained grey with occasional minor siltstone clasts

• becoming orange/ blown streaked 8l1d limonite stained brown

• becomilg brown

Commenta: Borehole Diameter.

GroundWater encountered at 50mm

2.8 metres

Ch~)l ~rouNoAnoN lN OI Nf l & t NO

To(»OU

F~l

Clay

Silt

~ 7/~ - - --- --- -,xxx

Auger Borehole No. 26

Drilled By:

PMS

~3.0

-3.5

-4.0

""'4.5 i-

""' 5.0

-~ 5.5

Sand

Gravel

. . .. ... .... ······ ....... OrganiC -M'M'ill'-'

Pulrice ;;;~

Sheet 26 of 31

Processed By: Date·

DAB 10.3.00

140++

112

51

62

48

42

Sandstone

Siltstone

I.Jmestone

VolcaniC

2.2

2.6

2.8

3.7

2.8

. ; . . ;; ~.·~

VVV'I

Sample and Labolatory Test

Details

Pkllonic: + ++ No Core

Client : Takanlni Structure Plan Area 6 Limited

Project Location : Area 6A & 6B Plan Change Takantni Structure Plan

Job Number: 12635

Borehole Location:

mN

Doscrlption:

I mE

Refer to site plan

I Ground R.L.

SOIL DESCRIPTION

NATURAL: Still, non-plastic, brown slightly line sandy SILT

• becom1ng white mottled brown ashy sill

• becoming orange/ brown

Shll, Slightly plastic, dat1< brown (OI'ganlc stained) slightly fibrous clayey SILT Firm, mOderately plastic, o~ brown stteaked brown slightly hne sandy clayey SILT, wllh oa;asional mlnOI' woody inclusions • becoming white speckled and orange/ brown streaked l~t grey

• becOming damp

Shtf, slightly plastic, orange/ brOwn slightly clayey very line sandy SILT, 111olst

• beComing 01'8ngel brown streaked brown/ grey

E.O.B. at 1.8 metres. Too stiff to auger lutther.

I ..J

. ' ·~..:. . :

Auger Borehole No. 29

Sheet 29 ol 31

OriNed By: Processed By: 10ate.

PMS DAB 63 06

I 2'l ~gt -~ Sample and --~ l~ !~

... ~ Laborato~ Test .c <5!~ ! (J)~ ~Q} Q} Oetals

>a: (J)

150+

95 3.3

42 23

150-t-+

.2.0

-2.5

~3.0

~3.5

-4.0

-4.5

~5.0

-

""" 5.5

Comments: Borei\Oie Diameter Topsoi ~ Sand :- :- • Sandstone • ·~ ; • PlutOiliC + + + ~~~~~~--~~~~----~~~~----~~~

somm ., All V/,;j Gra\181 ~:·.:~~·. Slts1one ; ! ! 2 NoCora GroundWater not enCO\Intered

~FOUNDATION ~~HGINC lJoiH G

Check,-d F //1_ Silt

Clay

X X X Pumlct I ::. ::. Volcanic v v v

Client: Project Location :

Job Number:

Borehole Location:

TOPSOIL

mN

OescripUon·

Takaninl Structure Plan Area 6 Umlted . Area 6A & 68 Plan Change Takanlni Structure Plan

12635

I mE Joround A.L.

Aeler to site plan

SOIL DESCRIPTION

NA !l,IRAl : Stiff, sllghUy plastic, orange~ tJrown motued brown slignuy ttne sanely sBghtly ciayey SILT

• becoming 1imoolte stained and orange/ brown streaked grey

• becoming black and orange/ brown mottled

Stiff, slighUy plastic, li!fll grey and orange/ brown streaked cream clayey SILT

son, moderately plastic, dark brown clayey SILT, moist with frequent black fibrous woody Inclusions

Soft, sllghlly plastic, brown very line sandy sightly clayey SILT, wet

W~lilf, sllghtl\'kasUc, orange/ brown streaked green/ gray slightly clayey very line sandY IL T • bocomii\Q ue/ grey

·becoming saturated (seepaoe)

E.O.B. at 2.2 mettes. Too stiff to auger turther

Comments: Borehole ~meter. Topso~

GroundWater encountered at 50mm Fl 1 6 metres.

Clay

I

~""-~ V///

- - -

Auger Borehole No. 30

i ~

..J

Drilled By:

PMS

g 2'! ~t 5

§

~2.5

~3.0

~3.5

-4.0

~ 4.5

-~

~5.0

!1-en~

~5.5

...

Sheet

t'rocesseo t:ty:

DAB

~go 1:--~ Cll~ ~~ i~

>a: (/)

96 6.9

134 4.6

130 4.5

30 2.3

150+-+

Sand Sandstone • •• ... ... • •• Gravel ::::::: s llatone z:z:z:

Organic ~.;.....;j Urnes tone ~

30 of 31

lOtte: 6.3.06

Sample and Laborat~ Test

Dalal s

Plutonic ++ +

No Core ~FOUNDAnON ~~~ lH OI H I( l iH G Sifl X X X~ Pt.mk:e I!I!:~ v olcanic ~vvv

Client : Tal<anmi Structure Plan Area 6 Limitod Auger Borehole No. 31

Sheet 31 ot 31 Project Location : Area 6A & 68 Plan Change Tal<anin. Structure Plan OrHied By: Processed By: Date:

Job Number:

BofetiOie Location:

TOPSOIL

mN

Oescnptlon:

12635

I mE I Ground R.L

Refer to site plan

SOIL DESCRIPTION

NA TUAAL : Still, slightly plastiC, orange/ brO'Nn sllght1y fine sandy sllghlly clayey SILT

• be<:Oming orange/ brown streaked fight orange/ brown

• becoming orange/ brown streake<f light grey/ cream

-SliD, slightly plastic, orBilge/ brown streaked lfght grey slightly clayey fine sandy SILT

Stiff. slighlly plastic, grey very medium shghlly Cfayey very medium sandy SILT

• becoming orange/ brown streaked grey, damp

• becoming while speckled and orange/ brown streaked brown

- be<:0m1ng saturated

• becoming grey streaked or811ge/ brown

?iift~ slightly plastic, bluet grey slightly clayey very hne to medium sandy SILT (weathered sandstone)

E.O.B. at4.4 metres. Too stiff to auger fur1her.

PMS

.... ~ .s c

! §. ~

xx~ 88:~~-1.5 XX 88~

- 4.5

'"' 5.0

-

'"' 5.5

01~ ~~ C'-s~ (/)~

DAB 6.3.06

g,~ ~ Sample and .... ~ t>" ~·u; Laborat~ Test i~ Dalal s c: >a: Jl

150+

108 3.9

130 2.8

121 3.5

150+

150+

150++

150++

150+

150++

150++

TopsoJI ~~ Sand Sandslone •-;-; • Plutonic + + + F1b V/h Gravel .~-.~~~·. Siltstone 1;·;! :~ NoCoca

Boroholo Oiamctor. Comments:

~FOUNDATION ~~ H e I N I I a I N G

Grooodwater encountered at 3.2 metres.

SOmm

Clay ~-:-:-: Organc ~~tww"' Umestone

Sdl x xx P\lm~Ct I I I volcanic v v v ...

Appendix 3 Site Plan and Cross-Sections

~;.,·

' -/_. _,.-..... ....:::::-..... , ./ , __ ...... \ -.,.. ....

... ~

\

,.-'

"-

!'4'- • .... ·. ~ • \ 1

.&. __... \

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·.

'·

0 H.md ,f.wCJC' BJ<Ot~ 1 Ffl dulll\J vi 3 3 061

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·~ ~ O.;pl~ 0 1 lnOtgao•C " R~lt

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?'//.A ZOI;t; I lbllo' ~ lllOIQdiiiC SOol$ L.() t~

t me,o thiC~

r.:-1 ZONE 2: Raltot l!::.:;i:;j IOOigdfltC SOliS hO'\\eetl

1 & 2 meu., tnlck

~ ZONC :.l Aott o t ~ !OCA03r"'C SeilS ·JIOater

th"n 2 mcltes thtk

\: .. if~'

TAKANINI STRUCTURE PLAN AREA 6 WAITED

~ .. , .• ,.~r.•I

SOIL ZONATIONS. TAKANINI STRUCTURE

PLAN. AREA 6

..._...rut ......

Bast dro""ng telerent;e • Ftaur Thomas Lid (dwg no '1U81/IO dated Ap1112008}

detcriP""" ell- _.,_, d•Le "'-0 500 1000 2000 3000 --_..,.. clo ...

IC:IIe I I I

H<ww>t>IMI Scolo (mtltool 0 500 1000 2000 lOOO bJ I I ::::d

Von:col Scait t-rn} utyrWII ....

IND 1

dob

coffey•) --

J' 29010.

geotechnics 1 5000 :»'\.C'"' JSTS MA>IAGING

ft1l fARft1 A3

LEGEND: ----

Legend and/or Notes

~

-lnilows hom

ullllnO--~~~ .... upWunl -ti•J) Relwlodt-.g 31142111

NOOE!I

T8kanlnl Structure Plan Area t1 Limited

ptCjed

Taunlnl Structure Plan, Area tiA & 88

.... Site Plan ----.-

p:<>;eano. GEOTNEWP 12635 119-W•no 1 of 3

descnptJon

B Apply new base drawong

~

~ 5

I

drawn

ss

...

J<r

I>

~ (!

~

approved dale

HE 11/03/09 0 500

0 500 b-

PORC~f~&UR ROAO

1000 2000

Horizontal Sca'e (metres)

1000 2000 I

Ven.cal Scale (meltes)

~ ~ .,

300.0

3000

-----=3

drawn I DAB

approved I JB

dale 29107/01

scaJe T 1:5000 -ong•nat

sa:e

LEGEND·

~ -= Overland Flowpath

coffey•) geotechnics SPECIAUSTS MANAGING THE EARTH

~ ~ ~

:>--C Proposed SW hne. Manhole & In I Outlet

client TAKANINI STRUCTURE PLAN AREA 6 LIMITED

P<OJ<O<'l

TAKANINI STRUCTURE PLAN, AREA 6A & 68

Mle SITE PLAN

p<oaeel no GEOTNEWP12635 r.gure no 1 of 3

0 g g

0 Jo j i !i ! .. ~

.. ~ s J 0 c:

0 0 i g <')

:r

0 0

Appendix 4 Stability Analyses Results

i

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i

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~ •«> "'" tdo' tlo' '"' '"' 1'6o Ho t1o

drawn OT client: Fraser Thomas Limited

approved coffey~ project

Area 6

date 2/0812008 Takanini Structure Plan geotechnics Sf'fCIAll~> I S MANACINC. Iitle: ~

scale NTS IHI:IOAAi t f

~ Fully Saturated • Mi@!l.al Fillin,g

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v

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date 1210812008 I

scale INTS I

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!B Mal•""' C:••UIIOJ F ol SlrtfiQ'J• Tr!» Moi• Coull>«•j 1JM '-"'"'91•1 18 H.Vrn3 Cot.tt•~• 10 !.Pi rrKt·OHAngi8 l~ d8g,t'lt!' I

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coffey -" geotechnics Sf'F.CIAIISlS MANAGING IH[tAfHH

j

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l''"' W019t•r 11 ~,..,rn) •;· uoh•tlatt ~ ~P:.. f nt1.ott Mg!e 2§ ,.J•O'•••

rile~t: project I

I title:

I

j project no: GEOTNEWP 12635

Fraser Thomas Limited

Area 6

Takaninl Structure Plan

1 ngure no: FIG2

~'~• N>me Poopo~..J Pllf'J (I) 5)

NUIIJ)'Its Mi1hoU I \liN

v t.k.f/Mor~t:r•llil'ft-Prtc• ,..,,,1h arl1wnbc • twce fuMI!o'1. t-t•" Sw••

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0 Cohtttah S~P• ;:nc:houAnqr. ~d&fJf•••

t

drawn OT Fraser Thomas Limited

approved coffey~ project:

Area 6

date 2108/2008 Takanini Structure Plan geotechnics

IItie: -- -.- -

scale NTS Sfl!'CIAII::; TS MANAOINO Normal Working Conditions IHf EAJ.HII .

software Slide Ver 5.035 project no

GEOTNEWP 12635 figure no FIG3

); r .. Na.M P•<r<><td Pond Raptd4< .. -M ...... , c ...... dftl

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Fraser Thomas Limited

approved coffey ·~ project:

Area6

date 210812008 Takanim Structure Plan geotechntcs

scale NTS SPt:CIAUS TS MAN AOINQ IItie:

Rapid Drawdown ~ Internal Batter Stability THE EARTH

software Slide Ver 5.035 project no:

GEOTNEWP 12635 I figure no FIG4

Appendix 5 TP1 09 Supplementary Notes

2

2.0 Dam concept

Tne dam conce?t ca:'l be cc:scr:t>cd as L,e overall ty?e•

!'t::-posc a:'ld s:4e ot the !'roposed da:n. as well as

poss:ble efiec:s Ques:tons to cor.side:- mc:ude:

\\'har wr/1 the dam bt usedjor?

:! \\' ha! will any water or other stored m<lterin/

be rl5ed jor!

3 Will the storage be pe:-manentiy full, or wiil levels fluctuate up and down?

4 How much stored water wrl/ be required?

.5 Is there suffic:enc srrean: flow co meer my

needs?

6 If water :s to be raken (rom the dam, how will

this be achieved'

7 Will the extent of fioodmg caused by the

reservoir affect others or myself?

8 How can provision for a spillway best be

achieved for a given srte?

9 Will the dam and ground around r: provtde

an adequate seal?

10 Hovo~ will I provide for any permanenr flow

bypass?

These questions must to be answcrec! dunr.g th.e des:gn

process. Addi::or.al questions may also arise. Ofte:1

examination of other dams :n tne area v,·ill pro\·icie

useful background kno...,·ledge for answen:1g these

questions

) .0 Dam components

A dam consists of seve:-al main cor:1pone::ts whi.:h mus:

wo:k togethe:- to ensure safe operation of the s:ruc:~:-e

o:ten : t is the connection o: ir.:erface between :he

dtffe:e:u cor.1ponenrs tha: a:e the h'eak poims ir. L,e

dar.1 des:g::. Tne ::1a::~ COr!'l?Onen:s of a ca:-:: a::C. t.."le

design c:-l:e:-:0! io:- each are:

) Sto:ag~

) Fol!'1Ca:ion

) ::.mba::k::~e:::

) S!'i);\\'a\'S

::> Pi?CS a;:c concuits

1:1 r:1a:w s;;u<!:ions t:1e c:-::e:-1a g;\·en below could be

undul~· consc:vative. Ob:a:ning expe:: engi:H:e:-ing

ir:?ut w!l. •ypica!ly resuh :."1 a more O!Jtir.1urr.. and hen.:e

cheaper des1g:1 by adci:css.ng sit~ S?ect!ic 1ssues.

3.1 Storage

The purpose of most da:ns is to store wate:- for use. The

volur:1e of storage a;:d extent of flooding caused by the

storage must be assessed. In the case of decorative

ponds and dams, the volume of storage may not oe an

issue .

To dete:"mine the approximate characte:lsttcs of the

dam storage a calculation guideline is provided in

Figures 2.6 and 2.7 a: the back of this pa:-t of the

gu1de!inc

Dam foundation

The foundation of a dam is the natura! sot I or rock on

which It stands. A dean stable fou!'ldatJon of adequate

stre:1gth is vital for dam durability and performance.

.-\n adequate seal must be forr:1cd to reduce leakage

(:om the dam · it may not fill or else the seepage may

cause instability.

Key foundauon requ:rements are:

• remove all topsoil and organic ma:e:ial fro::~

beneath the dam footprin:

• remove an~ soft materials I~ peat or swamp~·

depostts (unless ex?e:-t enginee:ing advice is

obtained on the design)

•

•

excavate a cutoff trench or ·~ey' under the

dam, :-!lore-or-less under the cres: li!'le o~ the

dam. i[be cutoff should extend a minimum

of I. Om into firm natural material. be at leasr•

~.p m w1de and have batter (side) slopes n

uo the side to at least the full water level --- ---pipe a~\· spn~gs or seepages er.col!:ttcec :r:

the doh·:lS:~eam hal:- o~ the dam ioo:?~1:1: to

the do\,·:~s::eam toe.

dam safety Guoce.ines fo• ~ors:ruc:ton, na,nte!'lanct anc morut.:l""!!

3·3 Embanl<ment

The cam er:1bank:ne~t. or til!. for::-:s the biockage

behind which the stored material acct:mt:!a:es. The

embankment must be formed from clean clays and/or

stlts :ree of topsoil or vege:auon. The fill sho~.:ld be

placed at a consistency and moisture content so as to

achieve high compaction standards

The embankment profile should meet the foilowing

minimum standards:

Crest

•

•

• surface to be protected by metal or othe suitable material

Slope angles

The upst:-eam and dow:ts::eam face should be r.o steeper than:

• 1 vertical to~ horizontal for dams under 15m

in height

• 1 vertical to 2 2 horizontal for dams above

1.5m in hetght.

Additional height

An allo\•"ance for settlement of the dam fi!l should

be made by slightly increasing the dam heigh: by

an extra 10%.

:-.:ote: Tracked vehicles should not be used for

compaction of dams g:'ea::: ~~an :.sm in height.

Fill volumes

The volume oi fdl required to build .s dam

increases rapidly wit!"! he:g!lt. The cost of the dam

will simila:ly increase :-.:ormally. f:ll for the cam

embankme:1t is taken from anstde the area t!lat wtll

become the storage reservotr. This mcreases :he

\'Oiume o! s:ored wa:c: behind t!ie da:r. ,,·,::-toe:

:he :~ceJ for in.::easing the Jam hetghl.

Ap?:ox!ma:e fill ,·olumes can be esttr:'latec using

:hl" :net~od ir. F1gu:es 1.8 a:1c ::.9.

3·4 Spillways

Adequate spillways are cructa! lor the sale opcrwo:1 of

darr:s . Two spiJh,·ays sl'lould be tncorporated 1nt0 :.he

dam design · normal ( se~vice) and flood spillwa~·s. I r.

some instances this mav be tmpractical, in which case

specific destgn tnput wtll be requtred. Whe~ever

possible the spi!h\·ays should be cons:ruc:ed in firm

natural ground to the side of the dam. The gradient or'

the spillways should be kept as flat as possible.

Normal or'service' spillways

This spillway takes the normal stream flows Set

the inlet of the service spillway at the normal full

s:oragc water level and size it to take severalumes

the mean winter flow.

The service spillway should consist of:

c~ ,...,. 0 20i)>wtl-.. lOOrrm it&.T<ttl'f

., ·~- ........ u -- eoc..-... -

01 ......... ..,~ .. .....,. Ll

091~~ , ... ·~><: ..... , ... ~1-CNMI'

Fiture 2 /· Sprllway TY(H arrd Typrcal Drmerrsiorrs

• If a nume is 10 be used,' stnglc s«uon oi ptpc or $tr:l!!u shoulc

be msullcd 1: the mlc: to hmo: the flow m to rhc numc.

Construction standards:-

Bee! :he dow:~strea:r. portion of :he pi?ed spi!!ways

from the dam crest om .. ·a~ds, onto a suita:,(e

d:ainage material such to minim!se erosion/

dissipate ene~gy

Keep the gradient and orientation of the spill,\·ar

as constster:t as possible. Changes in dtrection can

cause the tlow to jurr:? oc: of tlur:1e S?ilh"ays o:

damage pipe sptllways.

Stte the tnlet of the sp:tlwJy so as to lim:: :;,e

possibih:y of blockages.

Loca:e :he ou:Iet clea: o:· ::-e do\' mt~ea:n :~c: of

the dam anc a!ig:: it to d:rec: flo\,' Into the s:~e~m

do,,·nstrea:r. of the c!am. P0$1lion :ne ou:IC' so cH

:o rnin::-:1ise e~osio:1 Dis.:ha~g::-:g :he :~o\'' i::to a:1

old :rough se: 1r. the grounc,o: onto la:gc bodce:s

can hel? Jc:-:ieve :h:s.

3

dam safety

3·5 Pipes and conduits

?:?eS a:e of:cn ?U: c!-:rough :;,e bo:tor.-: o:'lhe d.t::: :o: d:-aw:r:g of wa;e:- but pipes throush da:-::s can be \,·ea:­

poims for seej)age. causing erosion of the dam ti!!.

Pipes th:oug~ C:ar:1s should mee: the io!!ow:::g

rec;u:re~en:s:

:) dig lhem into the r.atu :-al mate:-ials uncle: u1e dam,

whereve: possible

:) install cut off collars (or similar) around the p1pe

along the u stream half of the pipes length l:se

at least one collar for dams of less than :! Sm in hei ht, and at least two for higher dams

::> place d:ainage r:1a:e:ial (eg .. :nm c!iar:1e:c:-

gravel) along the p1pe for the downstream half of

its length

'J hand cor.1pact the fill arounc! the pij)e to e:1s:.::e

the pipe is not damaged.

De:ai!s for the design of condui:s through an ea:t.l-: r:;: er.-:bankment are shown in Figure 2.3. Alte:r.a::ve

desig;:s a:-e possible, .... ·ith enginee:ing input.

4.0 Dam construction

The following sec:1on g:ves bnef details on good

prac:ice in small dam const:-uc:10n If any c!i:ricuhies

are encou:Hered duri:1g construc:ion, an eng:nee:

expe:ie:-:ced in da:n design a:1d consrructior. should be

contac:ed.

c.,~c!" :.:a .. l Su :he-•

,._~n.;•J ~t: .. rc :t '~'"' ~.tl

=• .. !=r :e o• '.,. .t• ;:t.l" tl rr I"! ~w""" :' ) r mes :> :-.:,

~ .. ~ ........ ,.. ·o· ·o· ·o· Cutcff De!a1

Site Preparation

5:::? vege:.:1: ion, to?so:l and c:~s:.::taole r:1ate:la!s

from oenea:h :he cam ioot?nnt a:~d rror:1 the a~e.::

to be used as dam fill material. 1\eep the topsoil

for ~sc as .:1 coa::ns for t.~e C.1r:1 to a:C g:as~ gro,,·:..~

Remove t:ees a::d shrubs iro:n 1::side :he tina!

s~orage a:ea.

lns·ream da::ts not reco;-:,mendec.

2 Stream diversion

3

!:· rne s:ream is flowing, divert it a:-ou:1d or through

the c!am site while the dam is built Th1s can be

done by piping orb~· building a cha:tnel to one side.

The pipe option is often more practical anc! the

pipe can then be usee! for drawing wate: f:o:-n the

c!a:n or c!rainbg it ir. the future.

li a channel cive:sion is being used, the dam \~ill

need to be constructed in two halves.

An alternative is to form a te~po:a:~· dar.-:

t:.ps:reil::l a::d pr;mp the tlow f:o;:-: :i":is to downstream of tne wo:-king area.

Foundation

Excava:mg the founc!a:.on for the C:a~ shouid

i:ldude the cu:off trench. or key and pipe. Any

sp:ings o: seepages encountered on the

downst:eam hal:· should be dear of t.~e ex.:a\'a:ior:.

3ackf:!l the fo~.:::da::on a:td as soon as possib:e. to

avoid softe:-:mg or slur:1ping of :he ke>' trench or

valley sit!es.

:., ••• U-. :Ol~c,:·e: =·~t ; .g

,.., .. ·• C·~_,,.e a" :a• =.t~

~·• na;e '•'-Iter., ~~ .. Sc.:r.1 ;_r C,c••st 3-a--~ , .. s.,. a·

Craona~e Oeta" , .. , ...

uramage Deta11

5

12

Typ1cal Emba"1i<men: Drainage Details

F•gurt J. 7· Typical Embankmtnl Drainn~ ~1111l

and the surroundmg !ill can result ir. diffe:-en:ial

settiement. Thts will produce poter.:ial leakage

paths along the line of the cond:.1!t, whtch tr: the

worst case will enlarge with time, leading to fail~re.

In addittor.. It is very d1fficult to adequa~ely

compact arou:1d conduits. exacerba::ng the

problem.

Again. t.he classical a?proach was •o :ry anc s:O? see?age along conduits, tvpically wit.l-: the use oi

cut-off collars Cu:-or:· collars along the ups::-cJn;

po:-tion of :he conduit will retard tiow a :10 pro\· ide

a deg:ee o: support fo· ~e condua. bu: the sa::;e

problem o!· adequate com?a.:tton re:-:1air.s for

material ei:he: side o: the .:ollars For t!':ts :-e::so::

cut-of:' .::o!ius shou.d not be :-e:ied or. as ~~eo:::\·

means of .::on:roliing seepage, :nough t.:,ey are s:ii:

appitca:,le in mam· st:ua:10r.s 1:: r:1ar.v st:ua::ons

alterna:t\'e meas~.:res a:-e more il??llcable s:Jc~ as

:he USe o!· COr:Ge:e encaser::e:1t 0!" OCCC!:lf

Ano:he:- al:e:-nat:ve for s;:;al!e: c:!a:-:-:s wod<.! be

compacted soi l bentonite mixes The Jowns:rc:am sec;.on should however .Jh,·Jys be

-- -

drained in a controlled manner. This ensures t.iese

seepage flows tha~ will occur do not e:-ode t.'le fill

materta! around the condui~. A tvptca! de tall using

collars is shown in Figure 3.8.

Pressurised conduits

The use of pressu:-ised conduns througr. dar..s

should be avoided wneneve:- posstble. lf t.'leir l.Se

ts unavoidaole, the!r design and const:uctton mus;

be considered ve:y carefully. Because set:lemen:

of ±edam f:ll or u;;cicriytng four.cbrions car. ca:Jse

s:ress or disloca:ior.s to conduns pass::1g through

the dam. tn the case o: pressur:sec co:1dui:s higi:

,,·a:e:- ?ress!.lres, equi' aientto t.he '''ate: !eve! 1:0: the

n:se:-\'Otr. cot.:!d !:>e reieased ir.to the se::s:tive da:-::

~:'!t~:-.o: For t:-:!s :-easor. p:-essc::set.! .:o nC...:t~s a::.~

seicio:-:-: used for la:-ge da::lS.

There ts no de:':ni::ve :-de for when pressu:isec

co:1cki:s pose a significar.: rtsk. T~c s:reng1h o:"

:he iounda:io·'lS, :ype o:· condt.1: and conC:l!:'

purpose<!:! influence :he suttabtlin· o:· ?ressu:-tsec

concu::s