Dirty job – We have the man for you

I live next door to a man not given to much excitement.  He is a long time Parnell resident and a senior civil engineer with over 40 years of experience.  He talks stormwater and drains and huffs and puffs when Council do not empty the stormwater catchpits that hug the curbs of our urban roads.

Stormwater Engineer of the year

However, John Tetteroo ME, MEngNZ, CPEng, IntPE has had cause for excitement in the last few months as his invention comes to life.  Every year thousands of tonnes of rubbish and sediment flows from the road into our stormwater system and then out into the streams and ultimately into the sea.  If you look at Hobson Bay today and see picture of it 50 years ago you can see the effects that stormwater sediment and rubbish has had.   It is highly degraded and the build up of mangroves is a direct result of sediment runoff from urban development.

Stormwater runoff – in simple terms

Image source: ci.bainbridge-isl.wa.us

The stormwater pond at Martyn Wilson Reserve, on the corner of Shore Rd and Orakei Rd is doing its job in that is collects a lot of the sediment and rubbish before it can escape into Hobson Bay. However, the cost to empty the heavily polluted sediment from the pond to keep it in working order is eye wateringly high.

While he may not say much, John has an active mind and a while back he had a light bulb moment to reduce the contaminants and sediment reaching our waterways from stormwater runoff from our roads.  He helped design the TetraTrap.  The TetraTrap is a stainless-steel device that has be easily retrofitted to roadside catchpits to form a simple but effective barrier which allows water but not rubbish to pass through.  They can also be fitted with a fine mesh bag to collect sediments.  They provide at-source treatment within road stormwater catchpits and are easy to remove for cleaning.  They have been considered an “easy win” for Auckland Transport in its goal to reduce contaminants and pollutants entering our waterways.

TetraTRAP

Image Source: http://www.pwwa.ws/pdfs/WWM_-_Tetteroo,_Rambisheswar.pdf

John is also proud to tell me that they have no moving parts, have a 30-year design life and are 100% recyclable.

Auckland Transport

Auckland Transport is working with John and his team at the specialist water and wastewater firm GHD to expand the rollout of these Tetratraps into Takapuna and Milford with a specific aim to cut down on the pollutants entering these popular beaches.  To date 3000 Tetratraps have been installed throughout the Auckland urban region and over the next 10 tears the implementation programmes looks to install another 7500 of the units.  With the road network being a primary source of stormwater runoff and hence pollution the more “at source” barriers that can be installed to reduce rubbish and pollutants entering the stormwater network and ultimately our streams, rivers and the sea the better.

Furthermore, John and his team are developing a prioritisation matrix to determine the most critical interception points for each catchment.  The matrix considers the proximity of catchpits to sensitive receiving environments such as harbours, beaches and other waterways to determine where the next set of Tetratraps will be installed.  Currently the large catchment around Orakei Rd is being looked at to reduce the pollutants either entering the harbour or silting up the stormwater ponds.

So, if you see a well-dressed man with that look of 40 years-experience peering into stormwater catchpits, give him a toot as he is doing his bit to keep our waterways clean and free of plastic, rubbish and other contaminants.   And if you want catchpits installed in your area, start emailing your local board representative and you never know a shiny, stainless steel TetreTrap may makes its way to your catch pit.

Source: Interview over the fence with Mr Tetteroo and Prioritising to deliver safe waterways and harbours, catchpit by catchpit – a paper written by J Tetteroo and Y Yang, GHD for the 2019 Stormwater conference and Expo