Weir was appointed by Ghella Limited to provide design services on a broad range of enabling works designs to support the construction of the Herne Bay Collector Project. The scope included the design of permanent and temporary service diversions (including all three waters, and other dry utilities such as telecoms, power and gas) over the length of the 1.7km, 2100mm diameter tunnel, including ten manhole shafts, seven engineered overflow points (EOPs) and the control chamber at Point Erin Park. The scope also included obtaining Engineering Plan Approvals (EPA) from Auckland Council for works associated with existing public assets (i.e., diversion of existing three waters infrastructure and works on Auckland Transport’s roading assets).
To date, Weir has successfully completed the service diversion designs for the first 7 manhole sites (including the Control Chamber at Point Erin Park and all relevant EOPs). Our team members are currently also working alongside our sister company Andy O’Sullivan Geotechnical to provide MSQA and temporary works design services, with construction works having already begun at Point Erin Park. Diversion works at Point Erin Park have included two wastewater rising mains (DN 160 and DN110), a water main (DN63) and 100mm UPVC telecommunications duct. As part of this work, the team completed a hydraulic analysis to quantify network losses and confirm revised peak flow rates for each of the diverted pressure pipes. Design services on other sites have included several 50-100mm water main diversions (including the design and specification of relevant valves and fittings), 150-375mm wastewater pipes (including up to DN1500 manholes) and 225-675mm stormwater culverts (including up to DN1800 manholes). Specific design has also been required on several sites with respect to depths of construction (i.e., over 4m deep), accommodation of site constraints such as soft soils, protected trees, space restrictions, complex hydraulic connections including cascades, and connections into aged and vulnerable structures such as brick culverts.
The team is currently working on the design of service diversions for manholes 8-12, and associated EOPs, while also undertaking a peer-review of the permanent works design of the primary infrastructure to support the issue of CS2 Compliance Statements (i.e., Herne Bay Collector and associated infrastructure including the EOPs, Manhole shafts, tunnels, control chamber and plant room).
