Amohia Street stormwater catchment upgrade
Stage one of a three-stage upgrade of the Paraparaumu stormwater network began in January 2023. The upgrade involves installing larger stormwater pipes to reduce flooding within the Amohia and Ruahine Street catchment areas and help prepare our district to live with more water due to climate change.
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Our contractors will then be installing the new stormwater pipes along Rimu Road in three more stages, arriving at the Kāpiti Road intersection in late September.
We’ll have detours in place, and traffic flows will change as the work moves along Rimu Road. Your journey is likely to take longer than usual. Please take extra care around the work area, and plan ahead for delays.
We 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 1b 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.
Traffic flow is reduced to one lane, and no parking will be available near the work site.
During the April 2023 school holidays, we began installing the new stormwater pipe under the south-east corner of Kāpiti Primary School’s field.
Construction traffic continued to access the yard set up near the Wharemauku Stream in Iver Trask Place, and our contractor took all practical steps to minimise impacts of this work.
Stage 1b: Rimu Road from Iver Trask Place to Kāpiti Road – May–August 2023
We'll install approximately 150 metres of new pipe and two manholes along Rimu Road towards Kāpiti Road. Workers will carry out construction in four stages, and will need to change traffic flows as the work progresses.
From Sunday night 21 May, we'll be closing Rimu Road just north of Iver Trask Place for up to four weeks while crews install a large manhole. We need a full road closure because the trench for the manhole needs to be five metres wide and six metres deep, leaving no room for traffic to move around the worksite during this stage of the project.
We'll have detours in place, and delays are likely. We acknowledge this work will impact traffic flows in the area, and your journey times could be longer than usual.
We apologise for any inconvenience and thank you for your patience and cooperation as we get this important work done.
Rimu Road stage 1 will take up to four weeks: 21 May to 18 June. See larger image[JPG 203 KB].
Detour route while Rimu Road is closed. See larger image[JPG 126 KB].
Rimu Road stage 2 will take approximately four weeks: 18 June to 16 July. See larger image[JPG 147 KB].
Rimu Road stage 3 will take approximately five weeks: 16 July to 20 August. See larger image[JPG 146 KB].
Rimu Road stage 4 will take approximately five weeks: 20 August to 24 September. See larger image[JPG 145 KB].
Stage 1c: Kāpiti Road to Amohia Street, September–December 2023
During August we'll install the stormwater pipe diagonally across the intersection of Rimu and Kāpiti roads, and then 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.
