CCNZ / HIREPOOL CONSTRUCTION EXCELLENCE AWARDS 2017
CAT 1B CONSTRUCTION EXCELLENCE AWARD 2017
WINNER
CATEGORY 1B: Projects with a value of less than $5 million (Companyturnover greater than $10 million) PROJECT: Aniwhenua Dam Head Wall Remediation Works. CONTRACTOR: Waiotahi Contractors
Design-on-the-go approach Remediation of a serious leak in the dam forming the Aniwhenua Power Station head pond in the remote Kaingaroa Forest presented unprecedented challenge, complexity, urgency and risk. In September 2015 a leak was discovered through the lining of the dam which needed to be repaired with urgency due to the associated risks of flooding and damage plus a daily revenue loss of $60,000. Repairing the leak, deep under water amongst 30 years of debris, required a ‘design-on-the-go’ approach to drain the head pond and canal and construct significant and complex flood protection before the onset of high rainfall in late autumn and winter. Nova Energy, reliant on the dam for hydro-electricity production, selected Waiotahi Contractors and consultants Tonkin & Taylor to design and undertake the complex works, with a value of $2.78 million, within an extremely tight timeline. Waiotahi Contractors is a family owned business that started out in 1957 draining the boggy farmlands of Opotiki. Over the years the company has grown to a diversified civil construction, quarrying and trucking company with a turnover
10 Civil Contractors NZ in association with Contractor magazine
of around $20 million. The company says the key to winning the tender was its initiative to work openly with Tonkin & Taylor during pre-tender to devise workable methodologies with many unknowns. Work started in February 2016 and was completed 58 days later. The hydro-electric dam was decommissioned to allow the repair, with high loss of generation costs for the client. Works also needed to be completed before the high winter rainfall. Accordingly, Waiotahi, at one stage of the works, planned and resourced a seven-day-a-week, two-shifts-per-day schedule to ensure this project was completed according to the demanding timeline. Suffice to say, this project was far from a run-of-the-mill project for many reasons. A lot of the technical detail was unknown at the outset as the problem was under water, so it involved complex and technical work under ‘almost impossible’ deadlines. The project was also high risk, requiring close collaboration to allow for shared innovation and IP with all works carefully taking into account health and safety needs. A design-on-the-go approach had to be taken, as the problem area (the leak) was deep under water and amongst
