Milford Dart Ltd's proposal to build an 11.6km, $150 million commercial bus tunnel through two national parks was "technically viable" and the tunnel could be constructed and operated within environmental and safety constraints, the company's engineering expert says.
Last month, the Department of Conservation (Doc) resumed its hearing into the proposal, after Minister of Conservation Kate Wilkinson signalled her intention to grant the company a concession for the tunnel, proposed to run from the Routeburn road in the Mt Aspiring National Park to the Hollyford road in the Fiordland National Park.
However, the company's engineering evidence could not be furnished at that time because it was stuck in a red-stickered building in quake-hit Christchurch.
Yesterday, URS New Zealand Ltd senior principal Ronald Fleming passed his 27-page statement to Doc hearings chairman Paul Green and assistant Chris Visser, completing the submission process.
Mr Fleming has more than 40 years' engineering experience, the majority with tunnel-based development schemes, including the Clyde Dam Power Project, the feasibility stage, design and construction of the second Manapouri tailrace tunnel and the Homer Tunnel passing bays.
He said submitters had made several comments on "perceived design deficiencies" of the tunnel which implied a "lack of understanding" of the stage the project was at in terms of design.
Major civil engineering projects - including tunnels - typically progressed through at least four stages of design development before being committed to construction - the concept design stage, the pre-feasibility design stage, the feasibility design stage and the detailed design stage.
The MDL proposal was at the second of the four stages.
"Each of these stages represents a decision `gate' for the developers, where a `go/no-go' decision is made based on the technical and environmental feasibility and commercial viability.
"Typically, a large number of projects do not advance past stages one or two, for technical or commercial reasons."
Subject to a concession being awarded by Doc, MDL would "consider whether to advance to this staged design process", he said.
His evidence stated the estimated construction period of three to four years for the 11.6km tunnel was "well within the capabilities" of the tunnel-boring machine proposed for excavation of the tunnel.
Progress would average 12m-15m a day.
The cost estimate was "realistic" for the stage of design the tunnel was at, he said.
Another major point of concern for the submitters during the two weeks of hearings held in March related to safety aspects of the tunnel, including the diameter, "fire-life safety" and emergency egress provisions.
Mr Fleming said MDL's proposal was for a bus tunnel, "not a road tunnel", and, as such, New Zealand Transport Authority standards had "no relevance inside the tunnel".
The single-lane bus transportation tunnel was based more on typical underground railway tube tunnels and it would accept only diesel buses which complied with the minimum standards of fitness for purpose and mechanical condition.
The 5m excavated diameter would provide for "sufficient space" for a running surface, side kerbs for bus guidance and passenger egress in an emergency, he said.
Other safety provisions included automatic solid security gates at each portal, preventing "people and animal access" and no uncontrolled vehicle access.
Buses would designed with two-hour fire-rated engine compartments separating the engine, diesel tank and passengers and compartments containing fire-detection and suppression equipment.
The tunnel controller would be in radio contact with buses, which would be staggered at a distance of at least 1km inside the tunnel to mitigate the risk of "bus-to-bus accidents".
The controller would also be able to track the position of buses.
Mr Fleming said there would be no forced ventilation inside the tunnel because the "piston effect" of buses moving through it would provide adequate changes of air within the tunnel.
"An emergency forced ventilation system will be installed in the Hollyford portal structure, which will start automatically in the event of a fire."
Safety and emergency egress procedures would be developed and emergency rescue vehicles stationed at the Hollyford portal.
