Winch and grill installed

Published 24/11/2021

A new stormwater inlet grill has been fitted at Airlie Road in the Karehana Catchment with an onsite winch so it can be lifted during storm events to improve flood discharge capability.

When debris is clogging the inlet screen, lifting the grill can reduce the flooding impacts on upstream properties, especially in smaller flood events.

North of 22 Airlie Road, Plimmerton

When will it be used?

Lifting of the grill will happen under exceptional circumstances during storm events. The grill is there for safety reasons to prevent people being washed into the culvert and also to prevent blockages occurring within the culvert.

A water level gauge or ‘trigger’ point has been marked on the channel wall next to the grill. Wellington Water is also in the process of installing an electronic gauge, to enable remote monitoring.

Once the water level is close to the trigger point, a trained person will go to the site. They will check whether there is any blockage that can be removed by raking. If there is no blockage that can be removed and the water level reaches the trigger point, then the grill will be opened.

Who will operate the grill?

The stormwater inlet grill is hinged and can be lifted using a mechanical winch.

The winch and grill will be unlocked and operated by authorised people who are trained and equipped to work onsite during flood events. Currently Wellington Water staff are authorised, and once the electronic systems are up and running, the intention is to authorise Porirua City Council staff and local firefighters.

The authorised operators will have a standard procedure to follow and will remain onsite monitoring the flow while the grill is open. Once the water levels have subsided below the trigger point and no heavy rainfall is forecast, the grill will be closed.