Flood remediation to go ahead in Bexley and Woolston

Detailed design work on two further schemes to reduce the flood risk in Bexley and Woolston will go ahead following a Christchurch City Council decision today.

Councillors decided the preferred remediation option, identified for both Bells Creek in Woolston and Knights Drain in Bexley, should progress to the detailed design stage. Both remediation options reduce the frequency and severity of flooding in a 50 year rainfall event and benefit properties at risk of above floor flooding.

Infrastructure, Transport and Environment Committee Chairman Phil Clearwater says, "With this decision the Council is investing in flood remediation schemes that will improve the capacity of the stormwater drainage network and will also contribute to residents' ongoing well-being."

Land Drainage Recovery Programme Working Party Chair Councillor Pauline Cotter says, "Damage to land and stormwater infrastructure in these two areas poses a significant flood risk to homes.

"This is great news for these communities and another step forward for the Council's Land Drainage Recovery Programme. With the decision made to progress this work, we now have a considerable package of work underway and we are making good progress in addressing flood risk across the city," says Cr Cotter.

Council staff will now start work on refining the schemes' designs. This involves more design work, ground investigations, surveying floor levels, validating modelling and talking with and listening to residents. In the coming months, there will be opportunities for residents to be involved and provide feedback on these schemes as part of this work.

In extreme rainfall events both schemes aim to return areas within Bexley and Woolston to their pre-earthquake level of flood risk. However, there will still be flooding of streets, properties and some homes.

The estimated cost for the Bells Creek Stage 1 works is $9 million and Knights Drain $11 million. The costs will be re-estimated during the next design stages.

Bells Creek scheme
For the Bells Creek scheme, the preferred remediation option is expected to reduce the frequency and severity of flooding in a 50 year rainfall event and benefit at least 31 properties that are at risk of above floor flooding, with a further 88 properties experiencing reduced flood levels. Proposed Stage 1 work includes:

* A pump station located on Ferry Road near the Heathcote River.
* Minor re-grading of a short length of Richardson Terrace.
* A new detention pond within the northern half of Edmonds Park (where the sports fields are currently located. The sports fields will only be used to detain flood water in large rainfall events, and will otherwise operate as sports fields).
* A new detention pond within Linwood College's lower fields.
* Upgrade of pipes in the Mackworth Street area.

The Stage 1 area was identified as an early works package to speed up construction. Further investigations are currently underway to identify options for reducing flood risk in the Moorhouse Avenue, Ferry Road, Mackenzie Avenue and Tabart Street areas (Stage 2).

Knights Drain Scheme
The preferred remediation option for Knights Drain will see six of the 13 homes affected by above floor flooding benefit in a predicted 50 year rainfall event. A further 70 of an estimated 230 properties at risk of underfloor flooding will also see flood levels reduce. Another 60 homes will be protected by the proposed pump station during extreme high tide events. Proposed work includes:

* A pump station and pressure main, which is a pipe where the water in it is pumped under pressure, usually, to higher ground (Stage 1).
* Remediation of the existing stormwater basin (Stage 1).
* Modifications to Knights Drain (Stage 1).
* Using a small part of Wainoni Park as detention storage, which will only be used as a detention basin during large rainfall events. The area will be designed to incorporate picnic facilities (Stage 2).

Stage 1 work can be fast tracked as these structures are either already in place or are on Council-owned land. However, as Stage 2 is in a small part of an existing park wider community involvement is required ahead of any proposed work.

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