Simple solution wins prestigious environmental engineering award

GHD and Auckland Transport are the winners of the 2012 Engineering Excellence Award for Excellence in Environmental Practice for their ‘TetraTrap’ design. The TetraTrap is a simple catchpit filter which prevents the flow of road pollutants to Auckland’s waterways and harbour via the stormwater system.

Initiated in 2005, the New Zealand Engineering Excellence Awards are the premier awards for the engineering professionals of New Zealand. The award for Environmental Practice was introduced this year. The winners of this year’s awards were announced at a black tie function at the Langham Hotel on 30 November.

“We were thrilled with the number and standard of entries for the inaugural Excellence in Environmental Practice award,” said Awards Coordinator Dionne Needham. “The award recognises the changing face of engineering and the more holistic direction the profession is taking.”

In recent years, local councils have explored numerous options for treating stormwater discharge, including both at-source and end-of-line treatment options. Until recently, little thought had been given to the existing road drainage system (catchpits number more than 27,000) as a first point of opportunity for stormwater treatment.

The TetraTrap is a kind of screen which improves the capture of litter and contaminants. It can be retrofitted to catchpits and reduces the discharge of pollutants, sediments and heavy metals into the environment. TetraTraps can manage water flow in excess of 50 L/s and testing shows an outstanding increase of sediment capture of between 75-125% per four-month cycle.

“This is an excellent example of a simple, practical and cost-effective engineering solution that significantly improves the quality of the environment,” said Awards Judge Andrew Read of Pedersen Read Consulting Engineers in Christchurch.

With no moving parts, the filter screens are easy to maintain, require no special cleaning regime, can be manufactured locally and are fully recyclable.

The project raises awareness for cities elsewhere on the benefits of a simple but effective solution to reduce the extent of stormwater contaminants and gross pollutants from entering receiving environments. There is already international interest with the possibility of the traps being used soon in Australia.

The significant achievements of the TetraTrap program were previously recognised by the industry when GHD received the prestigious Institute of Professional Engineers New Zealand Arthur Mead Award for Environment and Sustainability 2011.