1211 - Engineering Report Complete C · 132002.220527.1

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DOCUMENT INFORMATION

 

Document Title:

Engineering Report

 

Document Reference No.

ENG_1211

 

Commissioned By:

M &M Charlton

 

Prepared By:

Barlow Shelley Consulting Engineers Pty Ltd

 

Author:

Peter Barlow

 

 

Reviewed & Authorised By:

 

Peter Barlow

 

 

 

DOCUMENT CONTROL
Version Date Author Reviewer
1.0 April 2015 P. Barlow C. Landreth

 

 

 

 

 

“©2015 Barlow Shelley Consulting Engineers Pty Ltd All Rights Reserved. Copyright in the
whole and every part of this document belongs to Barlow Shelley Consulting Engineers Pty Ltd
and may not be used, sold, transferred, copied or reproduced in whole or in part in any manner
or form or in or on any media to any person without the prior written of Barlow Shelley

Consulting Engineers Pty Ltd”

 

 

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CONTENTS

 

1.0 GEOTECHNICAL OVERVIEW .......cccscccsssesceceecneecnsscnsscesssesssessensneesssnssnssansansarseanseanseaneee T

2.0 STORMWATER MANAGEMENT PLAN ............00008
2.1 Existing Stormwater Runoff from Webb Road

 

  
 

2.2 Exisitng Drainage System....
2.3 Proposed Drainage System....

 

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2.4 Stormwater Discharge .......0scceseeccsenerceeeeeeeeeeseeeeeseaeseanaesseneesceeeeseeeseseaeseseaessananssanenseene

3.0 STRUCTURAL ENGINEERING FOR RENOVATIONG.........00ccccssscssses seers seers sseneesseneeseen

APPENDICES

 

APPENDIXA - ENGINEERING DRAWINGS

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1.0 GEOTECHNICAL OVERVIEW

Prior to undertaking any building alterations, one of the most important investigations for
this site is the Geotechnical Investigation. Please refer to the accompanying Geotechnical
Investigation Report No.14169-001-RevO by Tectonic Geotechnical & Environmental

Engineers.

The geotechnical results show that the site has a Low Risk of global slope instability, and
that footings for the new house alterations can be adequately founded on site without any
erosion problems. Additionally this geotechnical report provided permeability results to

aid the stormwater management of the site.

Generally the site is stable and well suited for the residential alterations proposed.

 

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2.0 STORMWATER MANAGEMENT PLAN

2.1 Existing Stormwater Runoff from Webb Road

 

One of the main reasons that the existing residence is often inundated with stormwater
runoff, is because stormwater from Webb Road spills over the kerb and channel and runs

down the private driveway to the house.

As detailed on our Stormwater Management Plan No. 1211/P02 and on our driveway
longsection Plan No. 1211/P03, this existing runoff from Webb Road will be redirected to
the Council Stormwater pit in the kerb and channel as legally intended. This will be
achieved by increasing the flood freeboard in the footpath by lifting the vertical curve crest

in the new driveway, thus providing a bund against stormwater runoff from the road.

2.2 Existing Drainage System

The ground floor level of the existing residence is RL15.85m. The driveway to the
residence drops from RL20.9 at Webb Road to RL15.81m adjacent to the existing house.

Attached Drawing No. 1211/P01 shows the layout of the existing driveway and residence.
Due to the steep drop along the sealed driveway and the sealed forecourt in front of the
house, stormwater runoff velocity is very significant by the time the stormwater reaches

the existing house.

Presently two grated drains, as shown on the attached Drawing No.1211/P01, have been
installed to intercept stormwater runoff from the driveway and forecourt, upstream of the
existing house. There is also a third open concrete drain on the north west boundary

which intercepts stormwater from the adjacent property.

Unfortunately the two grated drains in the driveway and the forecourt are often overtopped
by Stormwater Runoff from storms greater than a 2 year ARI storm. As can be seen the
floor level of the house at RL15.85m, is only 4cm higher than the grated drain which
catches stormwater runoff immediately upstream of the house.

The reason for this inundation is that the drains have not been designed for a 100 year
ARI storm, they are often clogged by debris, and the drain level is only 4cm below the

floor level of the house.

As a consequence the existing residence is often inundated by stormwater runoff during
short heavy storms (over a 2 year ARI storm). This is one of the main reasons the
alterations are proposed for this residence. The only safe drainage system is to have an

 

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overflow drainage path that can never be blocked, and surface levels that grade away

from the ground floor level of the house.

2.3 Proposed Drainage System

Please refer to our attached Drawing No. 1211/P02 which shows the proposed new
drainage system to the altered residence.

There are several features to note:
Firstly, all runoff from the driveway will be directed into a side entry gully pit (Council
standard) which cannot be blocked (i.e the overflow from the grate is still intercepted in

the side letterbox opening which is lower than the paved driveway).

Secondly, the underground drainage system will be designed for a 10 year ARI storm

event, which is much greater capacity than current system.

Thirdly, the finished surface level of the driveway and forecourt will be lowered and graded

away from the ground floor level of the house alterations.

Finally and most importantly, an overflow flow path is diverted around the house.
Therefore even if all the underground pipes become blocked, the surface levels will direct
a 100 year ARI storm runoff away from the house and around the southern part of the
house alteration. Therefore there will be no storm events that can inundate the altered
house floor levels.

2.4 Stormwater Discharge

Please refer to attached Geotechnical Report No.14169-001-RevO by Tectonic
Geotechnical & Environmental Engineers. They were tasked with identifying a safe and
secure method of discharging stormwater from the site, which did not cause erosion or

instability to the site.

To ensure stormwater runoff quality, every stormwater collection pit will be fitted with an

approved filter basket to remove gross pollutants.

Permeability results from the site show that a lined infiltration bore 5 metres downstream
of the house provides the best solution for stormwater discharge. Please refer to our

Drawing No. 1211/P02 which shows the infiltration bore proposed. The proposed

 

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stormwater discharge shown on Drawing No.1211/P02, complies with recommendations

from the Geotechnical Report for the site.

3.0 STRUCTURAL ENGINEERING FOR RENOVATIONS

In order to solve the drainage inundation problem, the floor level of the altered house will
be raised over the existing slab.

Enclosed is our preliminary Drawing No. 1211/P05 which shows the waffle slab system on

top of the existing house slab.

Footings for altered load bearing walls will be taken through the existing slab to
acceptable bearing material as specified in attached Geotechnical Report No.14169-001-

Rev0 by Tectonic Geotechnical & Environmental Engineers.

The structural section of the house enclosed, shows the proposed new retaining wall
external to the house. It has been designed to help resolve the current stormwater
inundation problem.

4.0 CONCLUSION

This report and the accompanying engineering drawings were undertaken at preliminary
building stage to ensure that the proposed house alterations are compatible with the
existing site, and that all engineering issues can be satisfactorily addressed at Building
Application stage.

It is our engineering opinion that the alterations to this house will overcome the current

drainage inundation problems, and that the alterations will be structurally suitable for this
site.

(alow

 

PETER BARLOW -— DIRECTOR (RPEQ 1330)

BEng, MIEAust, CPEng, RPEQ

For and on behalf of:

BARLOW SHELLEY CONSULTING ENGINEERS PTY LTD

 

Engineering Report Page 4 of 11
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ENGINEERING DRAWINGS

 

Drawing Nos 1211/P01 to 1211/P05

Prepared by Barlow Shelley Consulting Engineers

Page 9

 

    

WEBB RD

   

 

 

     
  

  
 

 
 

  
 

= LEGEND
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EXISTING DRIVEWAY

 

 

 

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VS ExistING
FFL 16.01

EXISTING LEVELS

EXISTING TREE

        

EXISTING BULDINGS

 
 

EXISTING CONCRETE

—=>- EXISTING STORMIATER FLOW

SV SW EXISTING STORMWATER PIPE

   

 

   
 

 

        
  
  
 

    

EXISTING LEVEL

 

 

 

x SL-1623

 

 

 

   

FORECOURT

 

 

EXISTING RESIDENCE
EXISTING <
FFL 16.06,

 
   
   
 
 

  

   

EXISTING DRAINAGE
INUNDATION

 

   
   

SL 15.80

   

     

 

 

 

/ EXISTING
FFL 15.85

 
 

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V AT 17 WEBB RD, SUNSHINE BEACH
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Director: PETER BARLOW DRAWING TITLE:

SCALE 1:200 A3. (RPEQ 1330) EXISTING SITE LAYOUT
bsscsinjarinscnirnmescuhesininseminnion | DRAWING STATUS D 5 craic ase w evehenhbjoras STORMWATER DRAINAGE

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Page 10

 

 

    
 
 
  

'WEBB RD /

ON ame TO BE LIFTED

‘200mm TO KEEP WEBB RD
DRAINAGE OUT.

        

 

 

 

LEGEND

 

    

 

PROPOSED DRIVEWAY

 
 
 

EXISTING LOT BOUNDARIES

 
 
 

EXISTINGLEVELS

 
 

 

ISTING TREE

 
 
 

EXISTING BUILDINGS

 
 

PROPOSED HOUSE

 

 
 

 

PROPOSE

 

 

  

 

 

EXISTING LEVEL.

 

 
 

 

PROPOSED GRADE

 

  

 

EXISTING GRADE

 

 
 

  
 
   
   

 

 

 

 

 

INFILTRATION AS PER GEOTECH
REPORT,

 

 

 

 

 

 

 

 

 

 

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‘SCALE 1200 43,

Director: PETER BARLOW
(RPEQ 1330)

DRAWING STATUS

NOT FOR CONSTRUCTION

 

OFFL 14.30

 

PROPOSED
RESIDENCE

 

 

 

 

 

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PROWEGT

PROPOSED RESIDENTIAL ALTERATION
AT 17 WEBB RD, SUNSHINE BEACH
FOR MURRAY & MARGIE CHARLTON

PROPOSED STORMWATER FLOW

 

PROPOSED STORMWATER PIPES
AND PITS:

    
   
    

PROPOSED CENTRELINE.

    

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1211

 

DRAWING TITLE:

PROPOSED SITE LAYOUT
STORMWATER MANAGEMENT PLAN

 

Page 11

 

   

  
 
   

1P.6804, 21.126

JOIN SMOOTHLY TO EXISTING
LP.2.694, 20.963

EXISTING SURFAC:

 

792, 16.500

PROPOSED DRAINAGE PATH

  

P.55.908, 15.100

 
   

12.8% 2.5% ~1.008% -7.140% 1.1444

GRADE

 

 

  

DATUM R.L.13.0

CUT(-)/FILL(+)

 

DESIGN SURFACE
LEVELS

 

NATURAL SURFACE
LEVELS

 

CHAINAGE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DRIVEWAY LONGITUDINAL SECTION

‘Seale - Vert. 1:100
Scale - Horiz, 1:500

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B a rlovw PROPOSED RESIDENTIAL ALTERATION
AT 17 WEBB RD, SUNSHINE BEACH

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Director: PETER BARLOW DRAWING TITLE:

 

 

 

 

 

(RPEQ 1330) “— PROPOSED DRIVEWAY AND DRAINAGE LONGSECTIO!
DRAWING STATUS
NOT FOR CONSTRUCTION

 

 

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Page 12

 

PROPOSED HOUSE
¢
2 OVERLAND DRAINAGE PATH GARAGE

3%

wee
RL14.00
Grade Level 15.100

CH 55.399 Ly

 

SECTION A

7:200 (A3)

  

PROWEGT

PROPOSED RESIDENTIAL ALTERATION

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~ AT 17 WEBB RD, SUNSHINE BEACH
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Be PRELIMINARY CROSS SECTION

SCALE 17200 A3 (APEQ 1330)
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DRAWING STATUS
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Page 13

 

 

PROPOSED HOUSE

 

 

 

 

 

 

 

 

STORMWATER RUNOFF

 

 

 

 

 

 

EXISTING HOUSE SLAB
|

 

 

 

 

 

 

WAFFLE SLAB SYSTENON FETANNG WAL STING OV EXISTING
EXISTING SLAB, ‘SLAB. (NOTE: BEARING NOT ISSUE)

FOOTINGS FOR LOADING WALLS AS
PER GEOTECHNICAL REPORT

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A AT 17 WEBB RD, SUNSHINE BEACH
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° 2 4 6 8 100

 

Director: PETER BARLOW DRAWING TITLE:
‘SCALE 1:20 A3 (RPEQ 1330) A PRELIMINARY SLAB AND RETAINING WALL SECTION
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