Savings all round on stormwater upgrade

When Rocla’s NZ-based pipe business, Humes, was called upon to supply the pipe and manholes for a brand new subdivision, they came up with a solution that was both cost effective and environmentally friendly.

With 90 brand new homes being built in a subdivision in Fielding, the Manawatu District Council (NZ) ordered an upgrade of the existing stormwater system in the area to cope with future demands. The upgrade was required to protect Feilding during high rainfall events by diverting stormwater from the Makino Stream to the Oroua River.

Rocla’s NZ-based pipe business (Humes) was called upon to supply the pipe and manholes for the job. However, due to the size of the three manholes required at the Pharazyn Street stage of the upgrade, the freight costs to transport the manholes, including the concrete bases was astronomical.

So a plan was devised to pour the concrete bases for the three manholes on site saving significant freight charges. In addition, the manholes were transported on their sides, as opposed to standing them upright. This avoided the use and cost of a pilot vehicle.

Once at site, the manholes, minus their bases, were easily lifted into place by a digger.

Once installed, a system was required to dissipate the outfall into the river. Gabion baskets – with a sizeable footprint of 127m² – were ruled out with the Humes team designing an alternative concrete precast unit with a more environmentally friendly 35m² footprint.