History and construction updates for the construction for the Leeston Stormwater Bypass upgrade

Leeston Flood Diversion ProjectLeeston Bypass location and stages

Leeston has always been prone to flooding, the Leeston creek is known to breach banks causing the flooding in high rainfall events in Leeston. Following the June 2013 flood event, a public meeting was held which the community asked the Council to look at options to divert flood waters from the farm land around the township and manage localised flooding within the township.

Following public consultation, a resident’s survey and the review of numerous options and design reports the decision for the bypass was approved by council as the best option going forwards.

The bypass will redirect the main flow of  floodwater away from the town centre for a 1% AEP storm event (1-100yr) through a specifically designed channel following the path indicated in the image below. This will restrict what goes through the centre of town while still keeping the base flow through the Leeston Creek.

The approval is for a multi-stage phased project which started with Stage 1 in 2014 and is expected to be completed by 2023.

Stage 1 Completed 2014/2015 by Grant Hood Contracting.

Stage 1 was the connection of the Ellesmere Hospital drain to Manse Road and widening of the High St Drain.

Stage 2 Completed 2016 by Johnston Civil Ltd.

Stage 2 was the upgrade of the Manse Road Drain and Reids Culverts

Stage oneStage two

Stage 3 construction due to begin onsite October 2020.

Stage 3 involves the replacement of High St culverts and connection of these into Volckman Rd Drain. This will increase the flow capacity to 8.1 m3 per second (from 4.3m3 per second).

What we will be doing is upgrading the existing twin 1200 mm diameter culverts to two parallel box culverts sized 2.5 m x 1 m and increasing the base width of the immediately downstream drain would enable the bypass to operate effectively.

The contract for this work has been awarded to SICON Ltd. Stage 3 - click to enlarge

Stage 4 Work is planned to commence February 2021.

Building of the Leeston Creek Bypass channel. This is what will be diverting flood flows from the 1% AEP through Manse Rd to Volckman Drain.

Council is currently negotiating land access agreements with landowners and completing details design to allow construction.

Stages 5 & 6Stage 5- click to enlarge

Stage 5 has been identified as being required between Harmans Rd and the bypass diversion. This is currently unbudgeted work.

Stage 6 includes creating a wetland to service the new area of development from Pound Rd / Leeston Dunsandel Rd.