IMPROVING ROAD STORMWATER RUNOFF QUALITY THROUGH TETRATRAP IMPLEMENTATION

Michael Fray & Tiannui Wang (GHD Ltd)

POSTER ABSTRACT

Working closely with Auckland Transport (AT), GHD developed an innovative, cost effective, sustainable device to improve the capture of gross pollutants and contaminants in road catchpits. The TetraTrap provides at-source treatment within existing road catchpits, utilising redundant space, and helping deliver an improved maintenance regime. Although the TetraTrap demonstrated promise in field trials, now more than ten years ago, it had not been independently tested until recently. Over 3500 units have been successfully installed across Auckland since its development, including almost 300 in the past four years. Therefore, it is of interest to determine the TetraTrap’s effectiveness in improving stormwater quality, and its suitability for inclusion in continuing stormwater quality improvement initiatives. NIWA led a 2-year comprehensive field evaluation of the TetraTrap, completed in November 2020, to measure its performance under operational conditions. Inclusion of the TetraTraps in catchpits led to an 87% increase in total solid loads capture, a 60% increase in capture of solids >63μm in diameter, and a doubling of the capture of solids <63μm in diameter. The TetraTrap’s performance in the field and its successful widespread implementation to date demonstrate its suitability as part of plans to improve stormwater runoff quality.

Moores, J,. et al. (2020) Albany Highway TetraTrap Trial, Final Report