The site is Lot 1 DP Survey of this lot and Willarong Road and Koonya Circuit is given in Figure 2.

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1 Our Ref : NA L02:BCP/bcp Contact: Dr Brett C. Phillips 8 th May 2015 Cardno (NSW/ACT) Pty Ltd ABN The Manager Bunnings Group Limited, c/- C&M Consulting Engineers 1/142 James Ruse Drive ROSEHILL NSW 2142 Attention: Mr Anthony Mancone Dear Anthony, Level 9, The Forum 203 Pacific Highway St Leonards New South Wales 2065 PO Box 19 St Leonards New South Wales 1590 Australia Telephone: Facsimile: International: Web: FLOOD IMPACT ASSESSMENT FOR PROPOSED BUNNINGS WAREHOUSE RE-DEVELOPMENT, CARINGBAH Bunnings Group Limited is proposing to redevelop a Bulky Goods Warehouse on a site that fronts onto Willarong Road and Koonya Circuit in Caringbah. The site is bounded by Willarong Road and Koonya Circuit (refer Figure 1). The site is Lot 1 DP Survey of this lot and Willarong Road and Koonya Circuit is given in Figure 2. It is proposed to demolish any existing buildings and to construct a new commercial development comprising elevated bulky goods retail space, loading facilities, an multistorey undercroft car park area and access driveways. Drawings of the proposed development are given in Attachment A. 1. PREVIOUS STUDIES 1.1 Sutherland Shire Development Control Plan 2006 Sutherland Shire Development Control Plan 2006 includes a series of maps of various hazards including flooding. The subject site is located on Map 56 which is reproduced in Figure 3. It is noted that the best known extent of flooding (in 2006) crosses the southwest corner of the property. Around 5% of the site is inundated to a shallow depth in a best known 1% AEP flood and would be classified as a Medium Flood Risk. Australia Belgium Canada Colombia Ecuador Germany Indonesia Kenya New Zealand Nigeria Papua New Guinea Peru Philippines Singapore United Arab Emirates United Kingdom United States Operations in over 100 countries

2 8th May Gwawley Bay Catchment Flood Study The purpose of the 2012 Gwawley Bay Catchment Flood Study 1 was to define flood behaviour throughout the Gwawley Bay catchment, including the analysis of surface runoff across the catchment, flows within the major pipe drainage network, and flooding within open drains, Gwawley Creek and Gwawley Bay. Results from the study formed the technical basis for 2015 floodplain management investigations, including the identification of problem areas and assessment of flood mitigation options to reduce the risk of flooding. Study Area The study area was the catchment that drains to Gwawley Bay, at Sylvania Waters. Gwawley Bay is located on the south side of the Georges River, immediately upstream of the Captain Cook Bridge at Taren Point. A smaller catchment area draining to the Production Road Channel, on the east side of Taren Point Road, was also included in the study area. Modelling Approach The modelling approach adopted for this study involved the use of a RAFTS hydrologic model for estimating catchment flows and a TUFLOW hydraulic model to estimate flood levels and velocities. Surface flows are represented in the TUFLOW model through a 2-dimensional grid covering the study area. Major stormwater pipes, drains and creeks are included as 1-dimensional elements within this grid. The drainage network represented in the 1D/2D floodplain model is plotted in Figure 4. It is noted that the major piped drain along the southern section of Koonya Circuit is included in the 1D/2D floodplain model. After extended discussions with Council officers, a 50% blockage factor was applied to the waterway area of all bridges, box culverts, or pipe culverts within the study area where the clear opening is less than 6m.Blockage factors of 20% and 50% were also applied to on-grade and sag pits respectively, in accordance with Sutherland Shire Council policies and industry standards. A 3m x 3 m grid was adopted to limit run times to less than 24 hours. The round topography was sampled from the digital elevation model at 1.5m spacing. There are some 650,000 grid elements within the TUFLOW model. Only major pipelines with a diameter of 750mm or greater were originally included in the model. A number of smaller pipelines were subsequently included where these are critical to the flood behaviour of an area. As stated in the 2012 report: The representation of the terrain surface through the ALS survey has an order of accuracy of 0.15m, and some artificial fluctuation of the terrain surface is evident. Prediction of flood depths that are less than 0.1m is therefore uncertain. 1 Bewsher Consulting (2012) Gwawley Bay Catchment Flood Study, Final Report, prepared for Sutherland Shire Council, November, 43 pp + Apps.

3 8th May Draft Gwawley Bay Catchment Floodplain Risk Management Study and Plan The following summary is drawn from the draft Gwawley Bay Catchment Floodplain Risk Management Study and Plan 2 which was recently placed on exhibition by Council. Written submissions on the report will be accepted by Council until 22 May During 2014 FloodMit Pty Ltd was commissioned to undertake a floodplain management study and plan for the catchment based on the flood study completed in The floodplain management study further reviews flooding problems within the catchment and investigates measures to reduce these problems and better manage the flood risk. The recommended measures to be implemented throughout the catchment are included in a draft floodplain management plan. The measures are anticipated to be progressively implemented by Sutherland Shire over a 5-10 year period. Flood Risk Mapping & Development Controls The estimated extent of inundation in a 100 yr ARI flood is plotted in Figure 5. The area potentially affected by flooding has been divided into three flood risk precincts (high, medium and low). Different development controls are then applied to new development proposals depending on the type of the development and the flood risk precinct in which the development is located. This is a similar approach adopted by Council for the Georges River. An outline of the flood risk precincts is provided below: i) The high flood risk precinct where high flood damages, potential risk to life, or evacuation problems are anticipated. It is recommended that most development is restricted within this area. ii) The medium flood risk precinct where there is still a significant risk of flood damage, but where these damages can be minimised by the application of appropriate development controls. iii) The low flood risk precinct where the risk of flood damage is low. Most land uses would be permitted within this area (subject to other planning considerations). The estimated extent of the flood risk precincts is plotted in Figure 6. Flood Damages A flood damages database was prepared for the study area to quantify the flood problem and to assist in evaluating the merit of a range of flood mitigation measures. The database includes details on over 1,500 properties throughout the study area that could be potentially affected by flooding. The database has further been divided into seven geographical areas to help identify the spatial distribution of the flood problem over the study area. Flood Mitigation Options Problem areas throughout the study area have been identified, and potential floodplain management options investigated, on the basis of: 2 FloodMit (2015) Gwawley Bay Catchment Floodplain Risk Management Study and Plan, Draft Report for Exhibition, prepared for Sutherland Shire Council, March, 95 pp + Apps.

4 8th May i) the extent of inundation experienced throughout the catchment; ii) the location of buildings potentially affected by above floor flooding, based on the flood damages database; iii) problem areas identified by the community, based on results from the community questionnaires and Council s Customer Complaints register; and iv) problem areas identified by Council and Committee members. Specific flood mitigation options for the study area are identified and assessed. Where specific solutions are not feasible, other catchment-wide measures including planning and development controls, public awareness initiatives, emergency management operations, and stormwater maintenance issues are discussed. 2. EXISTING CONDITIONS The estimated extent of inundation in a 100 yr ARI flood is plotted in Figure 5. It is noted the model estimates an area of inundation on the subject site to a depth greater than 0.1 m located at the rear of the current warehouse. This is in an open area that is exposed to rainfall. It is further noted that the 1D/2D model estimates shallow overflows into the subject site in the vicinity of the southern intersection of Koonya Circuit and Willarong Road and further wets along Koonya Circuit. It is further noted that almost all of these shallow overflows into the subject site occur in locations where solid walls would in fact prevent these overflows (refer Plate 1). The only location at which overland flows could spill into the area located at the rear of the current warehouse is at the current driveway entry just west of the southern intersection of Koonya Circuit and Willarong Road (refer Plate 2). As disclosed in Plate 2 there is a local crest in the driveway entry on the south-eastern side of Koonya Circuit which is intended to prevent overland flows entering this corner of the subject site under Existing Conditions. While the estimated depth of overland in this area < 0.1 m, it is not certain that the local crest in the driveway is represented in the model due to the adopted 3 m x 3 m grid which could easily have stepped over the local crest in the driveway. Consequently it is not clear that in fact the driveway crest is overtopped. As stated in the 2012 report: Prediction of flood depths that are less than 0.1m is therefore uncertain It is therefore concluded that the estimated area of inundation on the subject site to a depth greater than 0.1 m located at the rear of the current warehouse is due to the trapping of rain falling in this area and to shallow overflows from Koonya Circuit and Willarong Rd at locations where solid walls would in fact prevent these overflows. It is further concluded that this is a site drainage issue and that an active overland flowpath does not exist through the subject site. The mapped extent of the Medium Flood Risk precinct within the subject site (refer Figure 6) matches the estimated area of inundation on the subject site to a depth greater than 0.1 m located at the rear of the current warehouse.

5 8th May FUTURE CONDITIONS Key floor levels in the proposed re-development are as follows: Parking Level 02 Parking Level 01 Warehouse Level 01 Warehouse Level m AHD 4.00 m AHD 7.80 m AHD (Existing building 7.25 m AHD) m AHD Through the incorporation of low walls and landscaping, driveway grading with local crests and/or flood doors as needed it is intended to exclude floodwaters from the proposed building as indicated in Figure 7. As concluded above it is our view that the estimated area of inundation on the subject site to a depth greater than 0.1 m located at the rear of the current warehouse is a site drainage issue which will be managed by the proposed stormwater drainage measures and will not adversely impact on any adjacent properties. 2. ASSESSMENT OF COUNCIL REQUIREMENTS 2.1 Sutherland Shire Development Control Plan 2006 Section 4 of Sutherland Shire Council s DCP 2006 covers Flood Risk Management. Section 4.a.1 provides Objectives for All Development on Flood Prone Land while Section 4.b.9.1 provides Additional Objectives for Development in Employment Zones on Land with Low and Medium Flood Risk, Except for Dwellings and Vulnerable Development, Communications Facilities, Telecommunication facilities, Hazardous or Offensive Industries or Storage Establishments, Liquid Fuel Depots, Public Utility Undertakings or Utility Installations (Including Generating Works and Waste Disposal) as follows: 1. The following Controls apply; a. Floor Level i. Habitable floor levels shall be no lower than the 1% AEP flood level plus 500mm freeboard. A habitable floor area in an industrial/commercial situation includes all working areas, such as offices, lunch rooms, bathrooms workshops and areas used to store possessions or product susceptible to flood damage. Please advise how this requirement will be met based on the assessed flooding in Koonya Circuit. Will the driveways crests be designed to provide the required freeboard in Koonya Circuit (south)? Any measures need to be guided by the assessed depths given in Figure 5. While the 2012 flood study gives flood level contours these appear to be too coarse and would yield flood dpeths which do not agree with Figure 5 (and are based on ALS data which may be out by 150 mm). ii. Non-habitable floor levels shall be no lower than the 5% AEP flood level. Please advise how the development will exclude the entry of the assessed flooding in Koonya Circuit (south) down driveways and into the car parking levels. b. Floor Level control for medium risk only:

6 8th May i. Where a building is elevated to reduce flood hazard, the undercroft area is to remain open to permit the free flow of water under the building. A restriction shall be placed on the title of the land, pursuant to Section 88B of the Conveyancing Act, where the lowest floor is elevated more than 1.5 metres above finished ground level, confirming that the undercroft area shall not be enclosed. This requirement is noted and is reflected in the proposed design where the undercroft will provide open car parking. The intent of this requirement is satisfied. c. Building Components and Method i. All structures shall have flood compatible building components below the 1% AEP flood level plus 500mm freeboard. It is proposed that where applicable flood compatible building components will be used in accordance with this requirement. d. Structural Soundness i. An engineer's report shall be provided to certify that the structure can withstand the forces of floodwater, debris and buoyancy up to and including a 1% AEP flood level plus 500mm freeboard. It is noted that shallow overland flows only the southern side of the proposed development and that the proposed structure will readily withstand the forces of floodwater, debris and buoyancy up to and including a 1% AEP flood level plus 500 mm freeboard. An engineer s report could be provided if needed as part of the Construction Certificate documentation. e. Flood Effects i. An engineer's report shall be provided to certify that the development will not increase flood effects elsewhere, having regard to: - loss of flood storage; - changes in flood levels, flows and velocities caused by alterations to the flood conveyance; and - the cumulative impact of multiple potential developments in the floodplain. This report satisfies this requirement. As concluded above it is our view that the estimated area of inundation on the subject site to a depth greater than 0.1 m located at the rear of the current warehouse is a site drainage issue which will be managed by the proposed stormwater drainage measures and will not adversely impact on any adjacent properties. Accordingly the proposed development will not adversely reduce flood storage nor change flood levels, flows and velocities or the flood conveyance in Koonya Circuit. The cumulate impact of multiple similar developments (ie. where development is on the fringe of existing overland flowpaths and is not subject to an active overland flowpath would be minor.

7 8th May f. Car Parking and Driveway Access i. The minimum surface level of open car parking spaces or carports shall be no lower than the 1% AEP flood or the level of the crest of the road at the location where the site has access to the road. While the proposed parking levels are lower than the existing ground levels these parking levels will be protected from assessed 1% AEP overland flows in Koonya Circuit (south) which satisfies this requirement. ii. Garages shall have a minimum finished floor level no lower than the 1% AEP flood plus 200mm freeboard. As indicated in the response to requirement (f) (i) the proposed parking levels are protected from flooding which satisfies the intent of this requirement. iii. The level of the driveway providing access between the road and parking space shall be no lower than 300mm below the 1% AEP flood or such that the depth of inundation during a 1% AEP flood is not greater than either the depth at the road or the depth at the car parking space. This requirement is noted. iv. Basement garages and car parking areas with a floor level below the 5% AEP flood or more than 0.8m below the 1% AEP flood level, shall have a pump-out system, adequate warning systems, signage and exits. While this requirement is noted it is also noted that the driveway entries will be protected from assessed 1% AEP overland flows in Koonya Circuit (south). v. Restraints or vehicle barriers shall be provided to prevent floating vehicles leaving a site during a 1% AEP flood. While the proposed parking levels are lower than the existing ground levels the driveway entries are located outside active overland flowpath in Koonya Circuit (south). This requirement is not applicable. vi. The crest of the driveway providing access between the road and basement garages shall be a minimum of 200mm above the level of the 1% AEP flood. g. Evacuation This requirement is noted. i. Reliable access for pedestrians and vehicles shall be provided during a 1% AEP Only the southern side of the proposed development is exposed to shallow 1% AEP overland flows in Koonya Circuit (south). Reliable access is available for both pedestrians and vehicles from Koonya Circuit (north). This requirement is satisfied. ii. Reliable access for pedestrians or vehicles shall be provided from the building, commencing at a minimum level equal to the lowest habitable floor level to an area of refuge above the PMF level. Warehouse Level 02 is located at 14.4 m AHD which provides considerable freeboard above the best known PMF level adjacent to the site. This requirement is not applicable.

8 8th May iii. Adequate flood warning systems, signage and exits shall be available to allow safe and orderly evacuation without increased reliance upon the SES or other authorised emergency services personnel. Reliable access is available for both pedestrians and vehicles from Koonya Circuit (north). This requirement is not applicable. iv. The development shall be consistent with any relevant flood evacuation strategy, Floodplain Risk Management Plan adopted by Council or similar plan. Warehouse Level 02 is located at 14.4 m AHD which provides considerable freeboard above the best known PMF level adjacent to the site. The site could be potentially designated as a flood refuge for others in any relevant flood evacuation strategy or similar plan. h. Management and Design i. An area shall be available within the dwelling to store goods above the 1% AEP flood level plus 500mm freeboard. The western section of Warehouse Level 01 and Warehouse Level 02 provides considerable freeboard above the estimated PMF level. The site could be potentially designated as a flood refuge for others in any relevant flood evacuation strategy or similar plan. ii. No storage of materials which may cause pollution or be potentially hazardous during any flood is permitted below the 1% AEP plus 500mm. This requirement is noted. iii. Where a use of land involves the storage or use of materials that would contaminate stormwater upon inundation by floodwaters, the storage of the materials must be protected up to the level of the PMF. The western section of Warehouse Level 01 and Warehouse Level 02 provides considerable freeboard above the estimated PMF level. This requirement is satisfied. It is concluded that the merit assessment detailed above that the proposed development satisfies the requirements of Section 4.b.9.1 General Controls under Section 4 of Sutherland Shire Council s DCP Yours faithfully Dr Brett C. Phillips Director, Water Engineering for Cardno