Homebush Bay Bridge l Environmental Assessment PART C Assessment of environmental impacts Chapter 7 l Environmental risk analysis 7 Environmental risk analysis This Chapter provides an overview of the potential environmental impacts associated with the proposed bridge, and outlines the mitigation measures to be implemented to minimise these impacts. It specifically addresses the requirement of the Director General that the environmental assessment must include: ∕ An environmental risk analysis to identify potential environmental impacts associated with the project (construction and operation), proposed mitigation measures and potentially significant residual environmental impacts after the application of proposed mitigation measures. ∕ An appropriately detailed impact assessment of any additional key environmental impact that is identified through the environmental risk analysis. 7.1 Risk analysis approach The following methodology was used to identify and assess the potential environmental issues associated with construction and operation of the proposed bridge: ∕ Identify all relevant potential environmental impacts of the development, including the key issues outlined in the Director General’s requirements. ∕ Assess each of the potential environmental impacts using a risk assessment model, taking into consideration their likelihood and consequence. ∕ Outline potential mitigation measures to address the potential environmental impacts, and assess the likely residual environmental impacts after the mitigation measures are to be applied. The risk assessment model used to assess the potential environmental impacts is shown in Table 7.1. This model provides the basis for the detailed assessment of key environmental issues provided in this environmental assessment. Table 7.1 – Environmental risk assessment model Risk category Description A May have high or moderate impacts. Detailed assessment necessary to determine the level of potential impact and to develop appropriate measures to mitigate and manage the impacts. B May have high or moderate impacts. These can be mitigated by the application of standard environmental management measures. C Have low impacts. These can be managed by standard environmental management measures. 7.2 Risk analysis findings The results of the environmental risk analysis are summarised in the Table 7.2. The environmental assessment of the issues identified in this table are presented in Chapters 8 to 18. February 2012 83 Homebush Bay Bridge l Environmental Assessment 84 Table 7.2 – Environmental risk analysis findings Issue DGR Potential impacts Analysis – proposed mitigation measures and impacts remaining after their Risk Location key application cate- in the issue? gory report (Y/N) Traffic Y Construction ∕ The construction environmental management plan would include a A Chapter management ∕ Risk of traffic congestion as a preliminary vehicle access route into the site. Large vehicles would 8 and access result of construction activities, deliver outside of peak periods when feasible and reasonable. Appendix particularly at the Wentworth ∕ A pedestrian and cyclist route based on safe public paths would be G Point construction site. formed around the proposed work sites. ∕ Temporary interruptions to pedestrian and cyclist access on Shoreline Drive and to the footpath that runs parallel to the Rhodes foreshore. Operation ∕ The potential bus operation across the bridge (up to 20 buses per A ∕ Risk of increased traffic hour in the AM peak period) is unlikely to substantially change the congestion on the local road level of service of key intersections. network. ∕ The bridge would include signage and CCTV video surveillance. ∕ Potential for unauthorised vehicles (e.g. private cars) to use the bridge. February 2012 Chapter 7 l Environmental risk analysis Issue DGR Potential impacts Analysis – proposed mitigation measures and impacts remaining after their Risk Location key application cate- in the issue? gory report (Y/N) Public domain Y Rhodes ∕ The north–south foreshore pedestrian and cyclist path would remain A Chapter ∕ Risk of unsafe environment for uninterrupted. 9 bridge users due to the mix of ∕ The landing would be sloped to provide good visibility for bridge Appendix pedestrians, cyclists and buses users. H at the Rhodes landing. ∕ The raised crossing treatment for pedestrians and cyclists would ∕ Potential interruption of have signage to indicate the shared pedestrian and cycling the north–south foreshore environment. pedestrian and cyclist path. ∕ Signage would be installed to convey bus-only and cyclist-only access on Gauthorpe Street, west of Shoreline Drive. Wentworth Point ∕ Uninterrupted foreshore access would continue, with pedestrians A ∕ Risk of providing poor visibility and cyclists able to travel under the bridge along the foreshore path. to drivers and cyclists travelling ∕ A roundabout would be provided to manage bus-only and bicycle- along the westbound bridge only access to and from the bridge and manage the merging of lane and merging with the one- buses and bicycles with other traffic. This would allow most of way traffic travelling west from Footbridge Boulevard to act as a normal street. Foreshore Boulevard. ∕ Signage would allow for bus-only access to the bridge for vehicles ∕ Potential interruption of travelling west to Rhodes. the north–south foreshore ∕ The grade-separated landing of the bridge at Wentworth Point would pedestrian and cyclist path. allow buses and cyclists to merge directly into the street network without potential conflict with pedestrians and cyclists travelling along the foreshore path. ∕ Cycling access to the bridge would follow on-street cycle paths to continue to the bus lanes on the bridge. ∕ Pedestrians would access the bridge from the north, with connections from footpaths adjacent to and through the proposed park and from the foreshore arrival square. Visual amenity Y ∕ Risk of delivering a bridge with ∕ Photomontages from representative vantage points show visual A Chapter unacceptable visual impacts in impacts are likely to be minor. The bridge has been designed with 10 the local and regional area. aesthetic values that fit well with the visual setting of the Homebush Appendix Bay area. H Overshadowing Y ∕ Risk of bridge structures, ∕ Shadow diagrams of the bridge structure, embankments and ramps B Chapter including embankments and at Rhodes and Wentworth Point show impacts would be minimal 10 ramps, creating significant and contained to the immediate area beside and below the bridge. Appendix overshadowing on existing and ∕ The bridge would not overshadow residential areas. H proposed public domain, open space, foreshore areas and residential uses. 85 February 2012 Homebush Bay Bridge l Environmental Assessment 86 Issue DGR Potential impacts Analysis – proposed mitigation measures and impacts remaining after their Risk Location key application cate- in the issue? gory report (Y/N) Climate change Y ∕ Impacts on the structural ∕ Bridge collapse and inundation would be unlikely to occur as the B Chapter integrity of the bridge. majority of the superstructure would be above the 2,000 year ARI 11 ∕ Coastal inundation at bridge event. landing points at Rhodes and ∕ Landing points would be designed to meet existing sea level rise Wentworth Point. predictions as a result of climate change. ∕ Increased restrictions on ∕ Appropriate maritime clearances has been allowed. maritime navigation due to reduced clearance beneath the bridge. Navigation and Y Construction ∕ The construction environmental management plan would address B Chapter safety ∕ Risk of direct impact of vessels the management of maritime traffic with procedures and impact- 12 during placement of new bridge reduction measures to be adopted during construction. piles and piers. ∕ Exclusion zones would be marked around critical areas of ∕ Risk of physical obstruction construction activities and floating construction plant. of vessels from the use of ∕ Boat operators would be sent alerts about ongoing construction construction barges. activities through the issue of a proclaimed Marine Notice via RMS. ∕ Temporary Aids to Navigation would be provided where required (e.g. lighted buoys to mark exclusion zones). Operation ∕ A main navigation channel would be provided, and an appropriate C ∕ Reduced transit options from the vertical and horizontal clearance would be set. north to south side of the bay. ∕ Permanent Aids to Navigation would be provided on the bridge as ∕ Restriction of vessels with an per the relevant standards. air draft larger than can be ∕ There would be allowance for the six lanes of the proposed Rowing permitted by the navigation NSW course to pass under the western bridge spans, as well as channel bridge clearance height. sufficient height clearance. ∕ The bridge would be a new ∕ During Rowing NSW events, temporary exclusion zones would be impact hazard for vessels in the set up around the rowing course and the pier extents would be bay. marked. ∕ Impact on rowing course proposed by Rowing NSW. February 2012 Chapter 7 l Environmental risk analysis Issue DGR Potential impacts Analysis – proposed mitigation measures and impacts remaining after their Risk Location key application cate- in the issue? gory report (Y/N) Soils and Y Construction ∕ The construction environmental management plan would include a A Chapter contamination ∕ Water related construction contamination monitoring program, inspection routines, reporting 13 activities: there is a risk that protocols, roles,