Works Approval Report.pdf - the National Capital Authority

Campbell Section 5 - Works Approval Project Ref: 110029Prepared for the Land Development AgencyAnalysis of the trunk stormwater network has shown that flooding on Constitution Avenue is largely aresult of overland flow from the larger adjacent catchment to the east of the site and overland flowalong Anzac Parade from Blamey Crescent into Constitution Avenue from the west. Overland flowfrom the eastern catchment is approximately double that generated by the Campbell Section 5catchment. It should be noted that, even if the overland flow from Campbell Section 5 werecompletely eliminated, flooding would still occur on Constitution Avenue via overland flows fromAnzac Parade and the eastern catchment.Elimination of flooding on Constitution Avenue in a 100 year ARI storm event by detainingstormwater in the upstream and adjacent catchments and/or increasing the capacity of thestormwater network downstream of Constitution Avenue to Lake Burley Griffin are outside thereasonable scope of this project. However, proposed improvements within the Campbell Section 5site will reduce the amount of overland flow reaching the Constitution Avenue/Creswell Streetintersection low point and thereby provide some reduction, albeit minor, in the expected degree ofponding in Constitution Avenue. InfrastructureAs-built drawings have been reviewed and a detail survey has been conducted to establish thelocation and size of stormwater pipe infrastructure through the site. To resolve some anomalies, aCCTV camera survey was commissioned to confirm the stormwater pipe network.In the northwest corner of the site at the junction of Anzac Park East and Page Street, a manholereduces the 1350mm diameter trunk pipeline draining flows from the upper catchment to a 1050mmdiameter pipeline. The 1050mm diameter pipeline takes stormwater diagonally through to the middleof the site, before enlarging to a 1200mm diameter pipe and heading south to align with WendoureeDrive. This pipe network captures several smaller stormwater pipes as it traverses the site.Local residents have advised that the manhole at the intersection of Anzac Park East and PageStreet surcharges in most storm events, which is a direct result of the reduction in pipe diameterfrom 1350mm to 1050mm.The existing pipe network and overland flow paths through the site are shown in Figure 8.2.November 2012 Cardno 47