NZCF/Hirepool construction award winners - Category 4

CATEGORY 4 WINNER
Projects with a value exceeding $20 million

McConnell Dowell Constructors

Pike River Tunnel Project

The Pike River Tunnel project was both technically and geologically complex, requiring drilling and blasting of a 2.3 kilometre long access and service tunnel under the Southern Alps for Pike River Coal. The site is an hour’s drive northeast of Greymouth over narrow, tortuous access roads, making logistics difficult.

The tunnel portal and head works to service the project were established over an 11 kilometre mine access road, and machinery and materials for tunnelling and for the removal of spoil were purchased taking into account the particular constraints of the project. Most of the equipment was sourced offshore specifically for the project, and some was modified to meet construction requirements.

The tunnel is D shaped, 5.5 metres wide by 4.5 metres high at the crown, and at a constant one in 14 gradient.

The design and build contract was based on specific rock types, however these proved vastly different to those expected and additional tunnel support was required.

Specific work methods and materials were developed for rock bolting and shotcreting to ensure adequate support of the rock strata.

Environmental controls and treatment of spoil and run off formed a large pat of the contract, influenced by the rock types and the increased quantity of shotcrete used.

Initiatives taken by McConnell Dowell ensured the project was completed six months ahead of programme. McConnell Dowell is now working on excavating the pit bottom for the coalmine.