Amohia Street stormwater catchment upgrade
The Paraparaumu stormwater network upgrade began in January 2023. The upgrade involves installing almost 900 metres of larger stormwater pipes to reduce flooding to 350 properties in the Amohia and Ruahine Street catchment areas and help prepare our district to live with more water due to climate change.
Latest news
27/11/2023 We'll be opening Kāpiti Road near the Amohia Street intersection in Paraparaumu for travel in both directions on Monday night, 4 December, thanks to the great work of our stormwater crew.
The team are ahead of schedule on Kāpiti Road, despite the challenge of installing the new stormwater pipes around a number of utilities. They're now laying stormwater pipe through the corner site and in the new year, work will head north on Amohia Street.
Please keep an eye out for changing traffic conditions; traffic flows will change at various stages of the works. We expect to finish this project by the end of March. Thank you for your patience and cooperation as we upgrade our infrastructure to reduce flooding and prepare our district to live with more rain.
See Stage 1c for more information.
Work programme
We’re installing approximately 805 metres of new, larger stormwater pipes in stages as funding allows.
Stage 1: Iver Trask Place to Amohia Street
The new stormwater pipe needs to be laid under the road to avoid other services in the area. The stormwater pipes and manholes will be installed at about 4 metres deep in places. Due to the high water table, we need to remove water from the work trench. This means pumps and generators will be running near work sites most of the time.
We'll have traffic management in place, but the work will cause some disruption to traffic around the work area.
Stage 1a: Outfall of the Wharemauku Stream along Iver Trask Place to Rimu Road – January–April 2023
Our first task was to build a new outfall structure in the Wharemauku Stream in Iver Trask Place. Work then progressed along Iver Trask Place in stages towards Rimu Road.
In April 2023 we began installing the new stormwater pipe under the south-east corner of Kāpiti Primary School’s field.
Stage 1b: Rimu Road from Iver Trask Place to Kāpiti Road – May–August 2023
We installed approximately 150 metres of new pipe and two manholes along Rimu Road towards Kāpiti Road.
The first stage required a full road closure of Rimu Road just north of Iver Trask Place while our contractors installed a large manhole in a trench five metres wide and six metres deep.
The other stages saw our contractors installing stormwater pipe along Rimu Road until they reach Kāpiti Road in August 2023. Detours have been in place and traffic flows will change as the work moves along Rimu Road.
On Kāpiti Road, we allowed for one right turn into Rimu Road, where a one-way lane was open to southbound traffic. The left turn from Kāpiti Road into Rimu Road was temporarily closed when works reach the intersection.
Stage 1c: Kāpiti Road to Amohia Street, September–December 2023
During September we'll install the stormwater pipe diagonally across the intersection of Rimu and Kāpiti roads, and then head east along Kāpiti Road towards Amohia Street.
Stage 1d: Amohia Street to near 65 Amohia St, December 2023–March 2024
Activity to be confirmed.
Background
The Amohia stormwater catchment is part of the wider Wharemauku Stream catchment, which drains from the hills behind Paraparaumu through the Wharemauku Stream to the sea. Our investigations showed three main areas of interest within the catchment:
- Several properties on and around Amohia Street have a history of flooding during heavy rainfall, with numerous properties at risk of habitable floor flooding to a level of more than 820 millimetres during a 100-year Average Recurrence Interval (ARI) storm.
- Ruahine Street floods in heavy rain due to runoff from upstream hill catchments. The volume of rainwater exceeds the capacity of the existing stormwater network. While most of this flooding is shallow overland flow, it does back up to a level of more than 1.3 metres deep behind the train line. The runoff flows overland, generally as shallow sheet flows, before reaching an open drain downstream of Tongariro Street.
- Several properties on Kāpiti Road and near the upstream open drain are at risk of habitable floor flooding during a 100-year ARI storm.
We've been investigating this issue for several years, and considered several options and routes before deciding on this plan to install larger stormwater pipes.