cltr-20150656.04c-rev stormwater design council response

SUTHERLAND OFFICE LOCATIONS: SYDNEY-CBD SUTHERLAND WOLLONGONG NOWRA GOULBURN PICTON SINGLETON ABN 51 003 316 032 Suite 45, 40-44 Belmont Street, SUTHERLAND NSW 2232 PO Box 477, SUTHERLAND NSW 1499

Tel: 02 9521 3088 Fax: 02 9521 3066 Email: [email protected] www.jonesnicholson.com.au

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10 May 2018 Our Ref: CLTR-20150656.04C The Gallery at Engadine Pty Ltd Suite 1, Level 9, Strathfield Plaza 11 The Boulevarde Strathfield NSW 2135 ATTENTION: MR CRAIG BENNETT Dear Craig, DEVELOPMENT DESCRIPTION: NEW RESIDENTIAL DEVELOPMENT – “THE GALLERY” CLIENT: THE GALLERY AT ENGADINE PTY LTD LOCATION: 1081-1089 OLD PRINCES HIGHWAY

ENGADINE NSW 2233

Jones Nicholson has been engaged by The Gallery at Engadine Pty Ltd to assess the impact the that the proposed residential development at the above-mentioned site, will have on the existing Council stormwater trunk drainage network. In completing the stormwater assessment of the existing supporting infrastructure and the design of the development stormwater infrastructure, Jones Nicholson reviewed and designed in accordance with relevant Australian Standards and Council policy. To ensure the design is in accordance with Council stormwater requirements, Jones Nicholson has assessed and provided responses to queries raised by Council about the design. We will address all items individually. 1. The latest stormwater plans (C120-6 and C121-5) as shown in the transmittal have not been issued to Council for assessment. Please refer to latest design drawings in Appendix A. 2. Council’s Comments are based on following plans & stormwater report by Jones & Nicholson a. Ground Stormwater Plan C120-5 b. Stormwater Drainage Longitudinal Section C121-4 c. OSD Tank Plan C125-2 Please refer to latest design drawings in Appendix A. 3.Information related to catchment area, flow rates, pervious areas & orifice size shown in the Stormwater Report dated 25 Jan 2018 & plans submitted by Jones Nicholson and DRAINS model is not consistent. Please refer to the latest plans and updated DRAINS model provided for coordinated figures.

10 May 2018 Our Ref: CLTR-20150656.04C

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4.The DRAINS model does not include 10, 25, 30 & 45 min duration storms and shall be updated. The 25-minute storm event was viewed as the worst storm duration and has been adopted within calculations and the models. We have included the additional storm events in updated DRAINS model for your information though. 5.There are inconsistencies with respect to impervious and pervious areas as well as time of concentration for the sub-catchment areas in the DRAINS model. It appears that most of the landscaped areas considered in the model are above the basement car park and paved. The DRAINS model has been updated following the amendments to the landscaping drawings. We have broken the areas down into 3 catchments. These areas are:

Catchment for Building A – Total: 2,072 m2, Landscaping/ impervious: 81 m2 (4%) Catchment for Building B – Total: 1,715 m2, Landscaping/ impervious: 341 m2 (20%) Catchment for Building C – Total: 1,501 m2, Landscaping/ impervious: 451 m2 (30%) Total site area = 5,288 m2.

6. Proposed connection to the existing drainage system in Old Princes Highway requires further investigation into condition and performance of the system, which include supporting calculations to demonstrate the capacity of the system (20%, 5% and 1% AEP storm events). A CCTV inspection of the existing stormwater drain in the Old Princes Highway shall be carried out to assess its condition and potential remedial/upgrade. The inspection shall be carried out from the nearest stormwater pit on the upstream of the site boundary to the existing pit downstream of the site. Council has agreed with Bouvardia Constructions and HYZ Developments on the 23rd April 2018 as per email from HYZ Group dated 8th May 2018 ay 7.07am that the existing 375mm pipe in the Old Princes Highway does not require upsizing. Council also advised that any maintenance of this pipe is Councils responsibility. 7. The discharge from the OSD tank to existing drainage system in the car park in Miyal Place does not meet Council requirements. The criteria for the subject site is to limit post development discharge during 1 in 100-year storm event back to a pre-developed (greenfield state) discharge in 10 year ARI storm event. If the PSD for the site exceeds this amount, it will be a requirement to upsize the OSD system. The DRAINS model and OSD design has been amended so that the post development 100 years ARI storm event runoff, is restricted via the OSD network to control discharge for to the pre development 20 year ARI event runoff. This method was discussed and approved during the meeting held between the Builder, Council and Jones Nicholson on 23/4/18. It was calculated that the 20 year ARI runoff will be 199L/s. This has led to the OSD tank size to increase to a total of 76 cubic metres storage. The orifice size was also required to be increased to 298mm in diameter. Documentation has been adjusted to suit these amendments. 8. The stormwater outlet pipe (375mm RCP) and Orifice size (305mm) from OSD tank are larger than the existing pipe downstream and is not acceptable. See Appendix A for latest drawings. The orifice size is 298mm in diameter. Investigation also identified that we are connecting into a 375mm RCP downstream. Therefore, it will not be larger than existing.

10 May 2018 Our Ref: CLTR-20150656.04C

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9.Proposed connection to the existing drainage system in the Miyal Place car park area requires further investigation into condition and performance of the system, which include supporting calculations to demonstrate the capacity of the system (20%, 5% and 1% AEP storm events). A CCTV inspection of the drainage line shall be carried out to assess its condition. The inspection shall be undertaken from the existing stormwater pit in the Council’s car park area to Stormwater pit in Miyal Place. The proposed connection point in Miyal Place is labelled EX A01 on Jones Nicholson drawing C120 rev 7. Council advised Bouvardia and HYZ Developments on the 23rd April 2018 as per email from HYZ Group dated 8th May 2018, that the proposed connection point, which is a kerb inlet pit and councils 375mm pipe running downstream from this pit does not require upsizing. This is as a result of Bouvardia Constructions revising the OSD system to restrict the flow from the development to the 20 year ARI runoff of 199L/s. Council also confirmed that any maintenance of this kerb inlet pit and 375mm pipe is Councils responsibility. 10. The DRAINS model shows that in 1% AEP event, the overland flow from the site to the Miyal place car park will exceed 150l/s (110+14+20+10) and is not acceptable. There is a misunderstanding in reviewing our model based on the above. The 110L/s overflow is contained within the OSD tank. Within the model, the overflow height is set to the control chamber weir level within the OSD tank. Therefore, this flow will not upwell out of the tank and will instead fall to the tank outlet. The outlet pipe has been sized for the flow from the orifice (20% AEP event) in addition to the weir flow from the 1% AEP event. We have amended our model with the revised landscaping areas. This has reduced the amount of runoff. This leaves 52L/s of runoff from overland flow in the 1% AEP event. For a site this large, this is a very small flow which is the equivalent of one residential kerb discharge drain. Overland from the three building catchment areas are 20L/s, 14L/s and 9L/s respectively. An additional 9L/s is expected from the area around the OSD. 11. Outlets in the DRAINS model are assumed as freely discharging to the atmosphere. The consultant shall demonstrate that the OSD tank will not have a “Drowned Outlet” or downstream controlled. The tailwater influences will affect the discharge rate, which is undesirable. Therefore, Hydraulic Grade Line (HGL) assessment of the proposed drainage system shall be undertaken from the existing kerb inlet pit to determine that the Drowned Outlet does not occur at the OSD tank. This has been updated within the resubmitted DRAINS model to show compliance. There will be no drowned outlet to the OSD. The DRAINS model has also integrated runoff from the existing carpark into the kerb inlet pit that we are connecting into. The Hydraulic Grade Line of the stormwater line connecting to the existing pit can be viewed within the DRAINS model. 12. Supporting calculation for the basement pump out pit shall be provided to Council for assessment. This was provided on the DA and other lodged stormwater drawings C120 in the stormwater calculation details. Below are the details.

10 May 2018 Our Ref: CLTR-20150656.04C

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Should you need any additional information from us, please feel free to contact the undersigned on 02 9521 3088. For and on behalf of Jones Nicholson Pty Ltd

Jackson Bramley BE (Civil), MIEAust Civil/Structural Project Engineer

10 May 2018 Our Ref: CLTR-20150656.04C

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APPENDIX A – Current Design Drawings

120.69 m 2

FUTURE TRANSFER OF LAND

NO WINDOWS WITHIN 3m

x;192.52

x;192.55

x;192.47

x;192.53

x;192.42

x;192.47

x;192.51

x;192.48

x;192.16TIMBER SEAT

TIM

BE

R S

EA

T

TIM

BE

R S

EA

T

1540x2070

1540

x207

0

1540x2070

1540

x207

0

1540

x207

0

NO VENTILATION SYSTEMS WITHIN 6mSERVICES

SUBSTATION

MAIL BOX AREA

TOILETS RAMP

LV PIT HV PIT

x;192.49K

PIT

G

W/

ME

TE

RG

/

ME

TE

RE

LEC

CO

M/

NB

NH

W

DE

S.P

.EX

H

ELEC/COM/

NBN

G/

METER

W/

METER

HW

HW

30.37 m 2

DF3

6.97

%7.

14 %

5.00 %

5.00 %

7.14 %

5.00 %

7.09

%7.

14 %

Ram

p up

1:14

Ram

p up

1:14

Ram

p up

1:14

Ram

p up

1:14

Ram

p up

1:4

Ram

p up

1:8

Ram

p up

1:20

RAMP UP 1:20

RA

MP

UP

1:2

0

RA

MP

UP

1:14

5.00 %Ramp up

1:20

RA

MP

UP

1:4

0

PROPOSED EASEMENTEXISTING EASEMENT

20

FH

4

23

6 FH

1

2

FH

21

20

FH

15

FH

FH

LIFT-C1

FS-C1

F. H

. R.

F. H

. R.

F. H

. R.

OUTLINE

OF SLAB

OVER

450 DIA PIPE

7 8 9

10

1112131415161718191 2 3 4 5

1516171819202122

1 2 3 4 5

1

23

78910

13

1415

11 12 13 14

1 2 3 4 5

1617181920

1718

1920

21

12

34

5

5.00 %

7.09

%7.

14 %

6.97

%7.

14 %

5.00 %

4.90 %

DP

DPDP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

DP

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DP

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DP

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DPDP

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OU

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NE

OF

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RG

OLA

OV

ER

OU

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NE

OF

PE

RG

OLA

OV

ER

OUTLINE OF PERGOLA OVER

OUTLINE OFPERGOLA OVER

STORMWATER EASEMENT

SUB STATION EASEMENT

OU

TLI

NE

OF

PE

RG

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METER

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.

W.M.

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.

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.

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.

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.

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.

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.

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RWO

RWO

RWO

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RWO

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RWO

RWO

RWO

RWO

RWORWORWORWO

RWO

RWO

RWO RWO

RWORWO

RWO

RWO

RWO

RWO

RWO

RWO

RWO

RWO

RWO

RWO

RWO

RWO

RWO

RWO

Ker

b 30

0w x

150

hK

erb

300w

x 1

50h

Ker

b 30

0w x

150

h

hand

rail

hand

rail

hand

rail

hand

rail

handrail

Ker

b 30

0w x

150

hK

erb

300w

x 1

50h

Ker

b 30

0w x

150

h

panel lift door

roller door

RAMP UP 1:40RAMP UP 1:40RAMP UP 1:40RAMP UP 1:40RAMP UP 1:40

A B C D E F G H I J K L M N O P

1

2

3

4

5

6

7

8

9

10

11

12

OSD

1. DECOMMISSION EXISTING STORMWATER LINE ACROSS SITE FOLLOWING INSTALLATION OF DIVERTED LINE REFER TO TELSTRA STORMWATER DIVERSION PLAN.

2. THERE ARE UNDERGROUND SERVICES IN THE VICINITY OF WORKS. IT IS THE CONTRACTORS RESPONSIBILITY TO LOCATE AND LEVEL ALL SERVICES PRIOR TO COMMENCEMENT OF EXCAVATION EARTHWORKS.

3. EXTERNAL PITS TO BE FITTED WITH WATER QUALITY INERTS IN ORDER TO MEET SSC WSUD REQUIREMENTS.

600SQ

600SQ

600SQ

GD1

600SQ 600SQ

600SQ

600SQ

600SQ

600SQ

600SQ

600SQ

. . .EMERGENCY OVERFLOW PATH

EMERGENCY OVERFLOW PATH

REFER TO INGROUND OSD TANK DETAIL. GL 191.30

FROM SUTHERLAND SHIRE COUNCILS STORMWATER POLICY: REDUCE POST-DEVELOPMENT FLOWRATES FOR EVENTS UP TO/ INCLUDING THE 100 YEAR ARI EVENT.

TOTAL SITE AREA = 5,288m2

PRE IMPERVIOUS = 1,522m2 (28.8%)POST IMPERVIOUS (+ ALLOWANCE FOR LANDSCAPING HARDSTAND) = 3,650m2 (69%)

VOLUME STORAGE REQUIRED = 76m3 (DRAINS)* Q 20YR ARI (25MIN EVENT)- PRE = 199L/s* Q 100YR ARI - POST = 199L/s

NOTE: SUTHERLAND SHIRE COUNCIL OSD POLICY (REFER TO DCP SECTION "STORMWATER MANAGEMENT") ALLOWS 33% OF RAINWATER TANK AS OSD DISCOUNT, PROVIDED RE-USE IS CONNECTED TO INTERNAL USES EG TOILETS OR LAUNDRY WASHING.

VOLUME OSD FROM RWT = 5kL X 33% = 1.67kL;OSD TANK = 37.7m3

TOTAL = 39.4m3 OSD STORAGE

SITE DISCHARGE ACHIEVED VIA ORIFICE PLATE ON OSD OUTLET TO EXISTING KERB INLET PIT.ORIFICE = 21.9 X SQRT (PSD/ SQRT (H))H = HEIGHT OF TOP WATER LEVEL FROM CENTRELINE OF ORIFICE (M)H = (INVERT OF 5YR STORAGE) - (OUTLET CENTRELINE LEVEL)H = RL 190.75 - RL 189.175 = 1.575mTHEREFORE, ORIFICE = 298mm DIAM.

SUBSOIL CALCULATIONS

ASSUME SOIL IS SATURATED TO GROUND LEVEL AND INFLOWS CAN BE APPROXIMATED BY SUB-SOIL FLOW NET:Q = 2/3 X K X H (M3/SEC PER M OF SUBSOIL LINE)ASSUMED SUBSOIL INFILTRATION, K = 1.4 X10^-6 (WEATHERED SHALE)H = HEIGHT = 6M DEEP, LENGTH OF SUBSOIL = 386MQ = 2/3 /140,000 X 6 X 386 = 11L/S

THEREFORE SUGGESTED TOTAL PUMP CAPACITY = 1.1 X (7.4 + 11) = 20.2 L/S.

NOTE: CONTRACTOR TO VERIFY FILL MATERIAL INFILTRATION RATES PRIOR TO CONSTRUCTION. SUPERVISING ENGINEER TO VERIFY DESIGN CHANGES IF INFILTRATION RATES DIFFER SIGNIFICANTLY FROM ASSUMED VALUES

PUMPOUT CALCULATIONS

AREA EXPOSED DRIVEWAY = 100m2 APPROX.MIN VOLUME = 50YR, 2HR = 10.5m3SUGGEST ADOPT V = 10.5m3QPEAK 100YR, 5MIN = 7.4 L/s

RAINWATER TANK CALCULATIONS

VOLUME REQUIRED BY BASIX = 5m3VOLUME PROVIDED FOR RWT NEXT TO OSD FOR MIN 5kL TANK.

OSD CALCULATIONSNOTES

EXISTING COUNCIL INLET PIT IN CARPARKGL. 188.02IL. 181.12 (APPROX)

OUTLET AT IL189.05 PROVIDE 260mmØ ORIFFICE PLATE AND TRASH RACK. TOP OF WIER STRUCTURE AT IL190.75. REFER TO OSD TANK DETAIL ON C070

DISCHARGE FROM OSD TO PIT. LIMIT PSD TO 178L/s

O L

D P R

I N

C E

S H

I G

H W

A Y

RO1

RO1RO1

RO1

RO1

RO1

RO1

RO1

RO1 RO1 RO1 RO1

RO1

RO1

RO1RO1RO1

RO1

GD1

<ø2

25 R

CP

@ m

in 1

.0%

ø225 uPVC @ min 1.0% >

ø225

uPV

C @

min

1.0

% >

ø100STW

ø100STW

ø100STW

ø100STW

ø100STW

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STW ø225 @ 1.0% <

STW

ø22

5 @

1.0%

<

STW ø100 @ 1.0% <STW ø225 @ 1.0% <

STW ø225 @ 1.5% <

STW ø225 @

1.5% <

STW ø300 @ 1.0% >

STW

ø22

5 @

1.5

% >

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ø22

5 @

1.5

% >

STW

ø22

5 @

1.0

% >

STW ø150 @ 1.0% <

STW ø150 @ 1.0% <

STW ø100 @ 1.0% <

STW ø100 @ 1.0% <

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-

900mm WIDE INTERLOTMENT EASEMENT FOR RELOCATED STORMWATER LINE, LOCATED WITHIN BOUNDARY

-

2000mm ELECTRICAL CABLE EASEMENT

ø225 RCP @ min 1.0% >BOUNDARY

BOUNDARY

BOUN

DARY

CHAMBER SUBSTATION EASEMENT

BOUN

DARY

STORMWATER LINE A REFER TO DRAWING C121 FOR LOGITUDINAL SECTION.

EX A01

B01

B02

B03 B04

B05

STORMWATER LINE B REFER TO DRAWING C121 FOR LOGITUDINAL SECTION.

PROPOSED KERB INLET PIT TO CONNECT INTO EXISTING STORMWATER DRAINAGE LINE.

EXISTING KERB INLET PIT GL. 190.50IL. 189.31

EXIS

TING

STO

RMW

ATER

PIP

EEX

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NG S

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900x900

5kL RAIN WATER TANK

STW

ø15

0 @

1.0

% <

OVERFLOW TO STORMWATER NETWORK

ø100STW

SCALE :

PROJECT MGR :

DATE :

DRAWN :

DRG SIZE :

DESIGN :

WWW.JONESNICHOLSON.COM.AU

P R

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THE CONCEPTS AND INFORMATION CONTAINED IN THE DOCUMENT ARE THE COPYRIGHT OF JONES NICHOLSON Pty. Ltd. USE OR COPYING OF THE DOCUMENT WITHOUT WRITTEN PERMISSION OF JONES NICHOLSON Pty. Ltd. CONSTITUTES AN INFRINGEMENT OF COPYRIGHT

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ON

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A1

CIVIL DESIGN

ABN: 51 003 316 032CIVIL STRUCTURAL BUILDING SERVICES. . 7 1 : 200

GROUNDSTORMWATER PLAN

C1201081-1091A OLD PRINCESHIGHWAY, ENGADINE

MULTI - RESIDENTIAL

DEVELOPMENT

HYZ GROUP

JB

OCT 2015

JB

KG

2017

150656

SCALE 1 : 200

GROUND FLOOR STORMWATER LAYOUT

AMDT DATE BY DESCRIPTION

4 15.12.17 JH ISSUED FOR EARLY WORKS




STORMWATER LINE A

DN375

4.2%

RCP CLASS 4

191.3

50

0.0

00

189.0

51.3

00

OSD

188.0

246.0

0181.120

0.9

06

0.9

00

EX A01

GRADE %

PIPE SIZE (mm) & CLASS

SCALE 1:200 (HOR)

1:40 (VER)

186.000

CHAINAGE

DESIGN SURFACE LEVEL

INVERT LEVEL

DEPTH TO INVERT

DATUM

BO

UND

AR

Y

EXISTING CARPARK

SURFACE LEVEL

DN225

1.0%

PVC

191.3

50

0.0

00

190

.850

0.6

00

B01

DN225

1.0%

PVC

191.5

50

26.6

64

190

.570

190

.583

0.9

80

0.9

67

B02

DN225

1.0%

PVC

191.5

50

28.4

84

190

.522

190

.552

1.0

28

0.9

98

B03 B04 B05

188.000

STORMWATER LINE BSCALE 1:200 (HOR)

1:40 (VER)

GRADE %

PIPE SIZE (mm) & CLASS

CHAINAGE

DESIGN SURFACE LEVEL

INVERT LEVEL

DEPTH TO INVERT

DATUM

EXISTING ø375 COUNCIL

STORMWATER LINE

BO

UND

AR

Y

EXISTING ROAD

FRONTAGE

SURFACE LEVEL

PROPOSED

LANDSCAPED

SURFACE

PROPOSED

RAMP

DN225

1.0%

PVC

192.2

50

79.3

03

18.9

950

190

.00

1

2.2

41

2.2

21

191.3

52

95.0

53

189.8

36

1.5

16

1.5

16

SCALE :

PROJECT MGR :

DATE :

DRAWN :

DRG SIZE :

DESIGN :


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F

OR

C

ON

ST

RU

CT

ION

A1

CIVIL DESIGN

ABN: 51 003 316 032CIVIL STRUCTURAL BUILDING SERVICES. . 5 1 : 200

STORMWATERDRAINAGE

LONGITUDINALSECTIONS C121

1081-1091A OLD PRINCESHIGHWAY, ENGADINE

MULTI - RESIDENTIAL

DEVELOPMENT

HYZ GROUP

JB

OCT 2015

JB

KG

2017

150656AMDT DATE BY DESCRIPTION

2 10.11.17 KG ISSUED FOR EARLY WORKS




WARNING NOTE :

THERE ARE UNDERGROUND SERVICES IN THE VICINITY

OF WORKS. IT IS THE CONTRACTORS RESPONSIBILITY

TO LOCATE AND LEVEL ALL SERVICES PRIOR TO

COMMENCEMENT OF EXCAVATION EARTHWORKS.

SB

P.M.J

2730

189,050

SFL 189,050

189,050

189,050

C D E

8

9

10

11

STW ø225 @ 1.0% <

STW ø100 @ 1.0% <

STW ø225 @

1.5% <

STW ø300 @ 1.0% >

STW ø1

00 @

1.0%

<

RO1

900x900

ø100STW

1C125

900x900

GRATED LID

MIN 1130mm HIGH BLOCKWORK

CONCRETE WALLS AROUND

CARTRIDGE CHAMBER.

8x 690mm HIGH STORMFILTERS

ø375 RCP @ MIN. 2.5%

<

5kL RAIN WATER

TANK

3C125

2C125

FA

LL

FALL FALL

FALL

INLET PIPE TO BE SLUNG

FROM SOFFIT OF ROOF

OFF OSD TO WATER

QUALITY AREA

INLET PIPE TO BE SLUNG

FROM SOFFIT OF ROOF

OFF OSD TO WATER

QUALITY AREA

STW

ø100

@ 1.

0% <

8

INSTALL LYSAGHT

MAXIMESH RH3030

TRASH RACK

GALVANISED BEARING

ANGLE SURROUNDS.

TYPICAL.

GALVANISED STEP IRONS

IN EACH CHAMBER TO

COUNCIL SPECIFICATIONS.

298Ø Dia CONTROL

OUTLET ORIFICE TO

OVERFLOW

CHAMBER

1% CROSSFALL

- CONTRACTOR IS TO VERIFY THE LEVEL OF ALL EXISTING SERVICES PRIOR

TO COMMENCEMENT OF EXCAVATION FOR DRAINAGE.

REFER STRUCTURAL

ENGINEERS DRAWINGS FOR

SLAB AND WALL DETAILS

900 SQ. PRECAST

CONCRETE LID 191.90

V100:Q100 RL 190.75

375ø DIA OUTLET PIPE

20

0

STORMFILTER WALL CORE

FILLED BLOCKWORK (BY OTHERS)

225ø DIA INLET PIPE

RL 189.05

WEIR WALL TO WATER

QUALITY CHAMBER

SET TO RL190.25


WALL STRUCTURE BEHIND

SECTION EXCLUDED FOR

CLARITY

V100:Q100 RL 190.75

MIN. RL 190.75


MIN. RL 190.75

RL 190.25

RL 189.050

NOTE: FALL TANK

FLOOR TO ORIFICE

OUTLET AT MIN. 0.5%

NOTE: INLET PIPES TO BE SLUNG

TO ROOF TO WATER QUALITY

CHAMBER, AS PER OSD TANK

PLAN. PIPES NOT SHOWN IN

SECTION FOR CLARITY

8

RL 189.050


SCALE :

PROJECT MGR :

DATE :

DRAWN :

DRG SIZE :

DESIGN :


P R

E

L I

M I

N A

R

Y


NO

T

TO

B

E

US

ED

F

OR

C

ON

ST

RU

CT

ION

A1

CIVIL DESIGN

ABN: 51 003 316 032CIVIL STRUCTURAL BUILDING SERVICES. . 4As indicated

OSD TANK PLAN

C1251081-1091A OLD PRINCESHIGHWAY, ENGADINE

MULTI - RESIDENTIAL

DEVELOPMENT

HYZ GROUP

JB

OCT 2015

JB

KG

2017

150656AMDT DATE BY DESCRIPTION





SCALE 1 : 100

OSD TANK PLAN

SECTIONSCALE 1 : 20 C125

1

SECTIONSCALE 1 : 20 C125

3SECTIONSCALE 1 : 20 C125

2

10 May 2018 Our Ref: CLTR-20150656.04C

Page 6 of 6

APPENDIX B – Updated Assessment Report

SUTHERLAND OFFICE LOCATIONS: SYDNEY-CBD SUTHERLAND WOLLONGONG NOWRA GOULBURN PICTON SINGLETON ABN 51 003 316 032 Suite 45, 40-44 Belmont Street, SUTHERLAND NSW 2232 PO Box 477, SUTHERLAND NSW 1499

Tel: 02 9521 3088 Fax: 02 9521 3066 Email: [email protected] www.jonesnicholson.com.au

Page 1 of X

20 April 2018 Our Ref: CLTR-20150656.03B The Gallery at Engadine Pty Ltd Suite 1, Level 9, Strathfield Plaza 11 The Boulevarde Strathfield NSW 2135 ATTENTION: MR CRAIG BENNETT Dear Craig, DEVELOPMENT DESCRIPTION: NEW RESIDENTIAL DEVELOPMENT – “THE GALLERY” CLIENT: THE GALLERY AT ENGADINE PTY LTD LOCATION: 1081-1089 OLD PRINCES HIGHWAY

ENGADINE NSW 2233

Jones Nicholson has been engaged by The Gallery at Engadine Pty Ltd to assess the impact the that the proposed residential development at the above-mentioned site, will have on the existing Council stormwater trunk drainage network. In completing the stormwater assessment of the existing supporting infrastructure and the design of the development stormwater infrastructure, Jones Nicholson reviewed and designed in accordance with relevant Australian Standards and Council policy. To ensure the design is in accordance with Council stormwater requirements, Jones Nicholson has also assessed water quality requirements and introduced measures in the design to ensure compliance. STORMWATER SITE DISCHARGE Currently, the stormwater of the majority of the neighbouring Telstra property, flows through the undeveloped site to the Myall Place drainage network in the neighbouring carpark facility. A majority of the proposed development site also flows to the Myall Place drainage network also. The remaining area of the proposed site, which contains existing commercial buildings (1086 – 1089 Old Princes Highway) along the Old Princes Highway frontage, flows to the Old Princes Highway Council drainage network. The proposed development (1081 – 1089 Old Princes Highway) will have all stormwater on site collected and flow to an onsite detention (OSD) tank within the property boundary. As the neighbouring Telstra property runoff will not be permitted to flow to the Myall Place drainage network because of the proposed development, a stormwater pit and pipe network will need to be constructed to divert this to the Old Princes Highway network. Details of this proposed construction is within Appendix A of this letter. Existing runoff from the proposed development site in the location of the existing commercial buildings will now be diverted to the OSD tank and have flow controlled to the Myall Place drainage network via orifice.

20 April 2018 Our Ref: CLTR-20150656.03B

Page 2 of 6

The site stormwater runoff in various storm events has been assessed for the site in the pre and post development state. The following table summarized the runoff to the Myall Place and Old Princes Highway stormwater infrastructure. PRE-DEVELOPMENT FLOW TO MYALL PLACE Telstra Catchment Flowing to Myall Place = 863m2

5yr ARI runoff = 34.0 L/s 100yr ARI runoff = 55.1 L/s

Development Site Catchment to Myall Place = 4,154m2 (Note: roof runoff of some of existing commercial buildings on this site flows into the Old Princes Highway network)


Total runoff to Myall Place pre-development is 213 L/s in the 5yr ARI storm event and 360.1 L/s in the 100yr ARI event. POST DEVELOPMENT FLOW TO MYALL PLACE Development to Site to Myall Place = 5,288 m2

5yr ARI flow = 175 L/s (controlled via orifice) 100yr ARI flow = 288 L/s (controlled via weir)

Note: Development flow controlled via 22.8m3 OSD tank with 260mm diameter orifice. OSD sized using DRAINS stormwater modelling software. DRAINS model provided. PRE-DEVELOPMENT FLOW TO OLD PRINCES HIGHWAY No flow from the existing Telstra site enters the Old Princes Highway stormwater network. Development Site Catchment to Old Princes Highway = 1,134 m2 (roof runoff of some of existing commercial buildings)


POST DEVELOPMENT FLOW TO OLD PRINCES HIGHWAY Additional Telstra Catchment due to diversion to Old Princes Highway = 863 m2

5yr ARI flow = 34.0 L/s 100yr ARI flow = 55.1 L/s

No flow from the proposed development site will enter the Old Princes Highway stormwater network. Based on the above calculations, the Myall Place and Old Princes Highway stormwater networks will have less runoff enter their systems in the post development state, compared to the predeveloped state. This is due to run off for the proposed development adequately managing flow through the onsite detention tank


Page 3 of 6

and orifice before discharging to the Myall Place stormwater network. As there is no increase on the existing Council stormwater network, no capacity upgrades will be required. The connection of WATER QUALITY MANAGEMENT To ensure compliance with Sutherland Shire Council and DA conditions, all urban stormwater runoff has been directed to the proposed on-site detention tank via the site drainage network. This can be seen in Appendix A of this report. Within the OSD tank, stormwater filter cartridges manage the runoff to required levels before discharging to the kerb. In order to meet Council’s water quality targets specified within the WSUD policy, the proposed development stormwater system requires the following elements to treat runoff so that it meets quality targets:

Roof water to rainwater tank of 5kL. It is proposed that 256kL/yr will be reused for irrigation purposes. Water quality to OSD tank to be provided by the installation of eight (8) filtration cartridges such as Stormwater 360’s PSORB cartridges (or approved equivalent) in the tank. Details of these cartridges proposed for the OSD can be found in Appendix B. Water quality to ground level to be provided by installation of treatment device such as Stormwater 360’s Enviropods (or approved equivalent) to eleven (11) of the external grated inlet pits, which lead to discharging to the OSD tank.

The following nodes and areas were used for the MUSIC model, along with rainfall and model parameters specified within Chapter 37 of Sutherland Shire Council’s Development Control Plan 2015.

Figure 3 – MUSIC model nodes and areas within model.

The above model and treatment devices, lead to the following post development reduction targets which satisfy Sutherland Shire Council’s WSUD technical specifications:

Figure 4 - Post Development load targets


Page 4 of 6

A MUSIC model has been provided as verification of the above results. Should you need any additional information from us, please feel free to contact the undersigned on 02 9521 3088. For and on behalf of Jones Nicholson Pty Ltd

Jackson Bramley BE (Civil), MIEAust Civil/Structural Project Engineer

cltr-20150656.04c-rev stormwater design council response

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