GROUNDWORK - City of Swan · PDF fileGROUNDWORK Consulting Engineers ... A higher level pipe...

Huachong Development Pty Ltd Lot 241 Wangalla Pl. Koongamia Summary of Drainage Calculations

1. Modelling Methodology

c GROUNDWORK Consulting Engineers

The methodology comprises quantitative analysis of available data to estimate existing and future flow behaviour from the development site. The analysis involved examination of the surface water hydrology to assess runoff characteristics from the site and sizing of stormwater mitigation devices to mitigate the impact of site development on existing flows and pollutant loads.

1.1 Hydrology

A runoff coefficient of c = 0.35 has been adopted for the Rational Method for the pre-development catchment. A time of concentration of 29.5min was calculated using methods presented in AR&R.

The rainfall intensities have been calculated using the data provided by the City of Swan.

The catchments contributing to runoff within the study area have been identified from survey and planning layout plans. The impervious areas for each sub-catchment have been estimated from the planning layout. Each new lot is modelled with an impervious portion of 65%. We have used a Green Amp infiltration model for the pervious portion of each lot. Roads were given an impervious proportion of 100%. A loss model of l.5mm initial loss and nil continuing loss was used for the impervious portions of the lots. A 15.9mm initial loss was used for the roads to model the 1 in 1 year bio retention pockets.

Runoff hydrographs within the site have been estimated for the 1, 5, 10 and 100 year ARI storms events using the RUNOFF mode of XP-SWMM . The Laurenson routing method for the routing of rainfall excess to the detention basin and outlet was adopted. Various durations have been checked for each catchment and ARI storm and the outlet pipes and detention storages sized to reduce the peak flows back to the Pre-development flows for the particular ARI storm.

1.2 Hydraulics

The routing of flows through the model was undertaken using the HYDRAULICS mode of XPSWMM. Storages and outlet pipe sizes from the storages were adjusted on the post-development model to reduce the post-development flows back to the pre-development flows calculated.

The flows calculated have been summarised on the enclosed tables.

The post-development flows have been checked against the pre-development flows at the outlet from the site . Each ofthe 1, 5, 10 & 100 year peak flows from the post development scenario are less than the pre development peak flows .

PO Box 2165 MARMION WA 6020 p: (08) 9448 6656 f : (08) 9243 0861 web: www.gwk.net.au e: [email protected] GWK Trading Pty Ltd as trustee for The GWK Trust ABN 20 681 635 057 trading as Groundwork Consulting Engineers

c 2. Internal Drainage Proposal

It is proposed to provide each lot with a connection from each roof to the stormwater pipes to run along the proposed roads within the site. These pipes are sized for a 1 in 5 year event. The roadway drainage is proposed to drain along the roadside gutter and into a shallow bio-retention pocket alongside the road. The bio-retention pockets are sized for a 1 in 1 year event. Subsoil drainage will be provided below the bioretention pockets to drain these. Once the 1 inl year event is exceeded a gully pit is provided in each bioretention pocket as an overflow into the stormwater pipes for up to the 1 in 5 year events. A below ground detention basin is provided in the POS at the lower end of the site alongside the entry road . The detention basin will have amended soil and subsoil drainage below it, designed for the 1 in 1 year runoff from the rooves. For a 1 in 1 year event there will only be a base flow from the subsoil drainage from under the detention storage and the bio-retention pockets, taking the treated stormwater flows. The detention basin has an outlet pipe located at the base of the detention storage sized for the 1 in 5 year event. This outlet pipe for the 1 in 5 year event is proposed to connect into the existing culvert at the creek on Wangalla Rd . A higher level pipe is proposed together with a spillway for the 1 in 100 year events. This larger pipe will only extend to the entry road that is at a lower level that the top water level in the detention storage and will allow it to bubble up to the road gutter and flow overland to the creek. The 100 year events from within the site are proposed to travel overland from the lots and roads to the POS and detention storage tank. The detention storage tank area is proposed to be covered with a minimum of 600mm of sand fill to enable the overland flow entering from the roads alongside to pond and soak into the detention tank, providing additional storage and to allow traffic over the top of it for mowing and landscaping maintenance. The area above the detention storage will have a landscaped park area.

PO Box 2165 MARMION WA 6020 p: (08) 9448 6656 f : (08) 9243 0861 web: www.gwk.net.au e: [email protected] GWK Trading Pty Ltd as trustee for The GWK Trust ABN 20 681 635 057 trading as Groundwork Consulting Engineers

c GROUNDWORK C onsulting E.ngineers

Client: Huachong Development Pty Ltd

Project: Lot 241 Wangalla Pl, Koongamia

Title: Summary of Drainage Modelling

Predevelopment Rational Method Catchment Area (Ha} 5.6886 Runoff Coefficient ClO 0.35 Time of Concentration (min) 29.50 ARI 1 5 10 100 Frequency Factor 0.80 0.95 1.00 1.20 Runoff Coefficient C 0.28 0.33 0.35 0.42 Intensity mm/hr 24.80 40.70 46.50 77.00 Q (peak flow) L/s 110 212 257 512

Post Development Catchment 1 2 Total

Total Catchment Area (m2} 35,511 21,375 56,886

Road Area (m2} 6,422 11,600 18,022 Lot Area (m2} 29,089 9,775 38,864 Communal (m2) - - -POS (m2} - - -

- - -

1 in 1 year Regular Event - Quality Treatment Road - Roof -multiple pockets located within POS storage

Base level (RL mAHD} varies 29.50 Base Area (m2} 688 900 Side slopes 1 in -- vertica l vertical Flood Depth (m) 0.40 0.40 TWL Area (m2) 688 900

Storages - Quantity Type Below Ground Base Area (m2) 1,000 Base level (m) 19.50 Side Slope 1 in -- vert ical Outlet Pipe dia 300 Spillway 21.40

450 pipe IL20.20 1 in 5 year Minor Event - Quantity TWL Area (m2} 1,000 Flood Storage (m3) 930 Flood Depth (m) 0.93 TWL (RL m) 20.43 Peak Outflow (L/s) 211

1 in 100 year Major Event - Quantity TWLArea (m2) 1,000 Flood Storage (m3) 313 Flood Depth (m) 0.31 TWL (RL m) 20.99 Peak Outflow (m3/s) 479

6232 summary.xlsx Page 1 of 1

2.4

2.2

2.0

1.8

1.6

1.4

~ 0

LL 1.2

1.0

0.8

0.6

0.4

0.2

0.0 1 Fri

Jan 2010

Node - 1

--J PERTH 5yr10min[Max 0.705]

PERTH 5yr 45min[Max 0.673] --] PERTH 5yr 90min[Max 0.599]

PERTH 5yr 6hr[Max 0.474]

PERTH 1 OOyr 25min[Max 2.342]

PERTH 1OOyr60min[Max 1.730] -- -PERTH 1 OOyr 3hr[Max 1.008]


' 3AM 6AM 9AM 12PM

Time

PERTH 5yr 25min[Max 0.874]

PERTH 5yr 60min[Max 0.64 7]


PERTH 1 OOyr 1 Omin[Max 2.192] --1 PERTH 1OOyr45min[Max 1.696]

LJ PERTH 1 OOyr 90min[Max 1.091]

PERTH 1 OOyr 6hr[Max 0.660]


!

'---- J,----r----~-----j

3PM 6PM 9PM 2 Sat

.,,,

,, , , ,, , Lin~ ,,

,; *"" ,., 300mm OUTLET

,*"' PIPE and 450mm OUTLET PIPE AT HIGHER LEVEL ..,,,,,

2 ,, ,,

.......

;

outlet link to ·determine 100 year flows

.~l' ,-,,

,"' ,, , v SITE FLOWS TO

PARK DETENTION TANKAREA

DETENTION STORAGE TANK

0.50

0.45

0.40

0.35

0.30

3: ~ 0.25

0.20

0.15

0.10

0.05

0.00 1 Fri

Jan 2010

Conduit Link2 from 2 to 3

PERTH 5yr1 Omin[Max 0.075]





PERTH 100yr 60min[Max 0.447] ___!I



3AM

,,, r \ .....

6AM

"· ...... -.. ---...... ,

9AM

·-·1 ·,.

12PM Time

I




PERTH 1OOyr1 Omin[Max 0.213]

PERTH 1OOyr45min[Max 0.4 79]




.,_ ..............

_,;~ ., '· -.. _ -··- ......

·-...... __ -··-

3PM 6PM 9PM 2 Sat

Node - 1

--~ PERTH 5yr1 Omin[Max 19.862]






~ PERTH 1 OOyr 3hr[Max 20.698] ---


21.0

20.8 -· ....

Q) 0) ct!

20.6

20.4

U5 20.2

20.0

19.8

19.6

j\

i

1 Fri

Jan 2010

3AM

, \

6AM 9AM 12PM

Time

--1 PERTH 5yr 25min[Max 20.108]



PERTH 1 OOyr 1 Omin[Max 20.433]





I

I

3PM 6PM 9PM 2 Sat

I .

TYPICAL ROAD LAYOU T DETAIL Kllllt1't -

~

~~ ~~

q~

4

~.:.:~~17 :.:::.:.::".:.:::T-::.:

a.w1 ....... 1 ....

- + --+-+------------- - - -+--+--+--l·-.. - ·--··--• I NnN&All 65l( r-.u-T..:.l:ft l.J J_ f j_ g=;--::==-=--

""''"•• .,, .. , ~ ~,, ~tf

~~ q<J:.'<)

~GROUNDWORK V ' ~-

M..S o.e.a 1 ...... M..S u.ts.a

= ------.. ___ _ ___ ... , _ _...,..._ =---~-----i "tff~:

Li

0

l ~. ~UL 2015 ~-=I" r ...... ...,

"'

,.

6232-(01

• ,'fi~~ d7. k 0 -\

\1,,,,.

~o/

~

~'

1.1-- U .1- 11 I I I I~~~~-.. UiocWl,.-!OWt ..-1 ..... 1-.

~ .. ,, ~~ .. , lfOlmU111 IOMIAl!T fO ~YlillD '-\".~ DllSU"DPfllllMlOVCM....... ....."lllj .wTD Ntl'9SO LOTS ..._~ "f:'?Jr1

~~ ~· "' ~ ~ ~-------<>-«;

G GROUNDWORK I- ---~--==--i C.......,..~ ·- 1; --__ .,..._ ,._r. __

jJJiEND

• y • flll --

PAOf'O'S(OK[AlllH6

CXl5Ttt;KCltllNG P'lll l'OS£0STOllHWATUIOllAW4Ar.f.

PROf'OS(D .JUllCTQI PIT

PltOf'OS(OtOJ(ONllE(TIOllPITANDl'ft'S

PR~O/f){ISTIHGlfUT\IRCSIOf(NTAYPIT

PROPOSED (jRAJ(OPIT TD MU)(.l.lfOttAAlll(iAAOENS

PltOPOSWllAINUAAC(NANOAll(.A

.,, t "'. l

1 5 JUL 20151 I - ,..., ,. ""I

L P~C .... rn '_j

GROUNDWORK - City of Swan · PDF fileGROUNDWORK Consulting Engineers ... A higher level pipe...

Documents

Transcript of GROUNDWORK - City of Swan · PDF fileGROUNDWORK Consulting Engineers ... A higher level pipe...