The science of ‘aquitards’
Canterbury’s aquifers may have made Christchurch the worst place in the world for earthquake liquefaction.
Flooded fields have some worried the site of the new Redcliffs School was a bad choice but the Education Ministry says recent rain is not responsible.
Much of Redcliffs Park was under water this week, appearing to support concerns from neighbouring residents about regular flooding at the reserve and surrounding streets and roads.
The ministry said the park’s flooded state was not because of recent rain, but was caused by work happening on the site.
Ministry education infrastructure service head Kim Shannon said a wastewater main was being installed before work to build the school began next year.
Part of the work involved ‘‘dewatering’’ – or lowering the groundwater table – by pumping groundwater into a sediment tank, then discharging it to nearby playing fields, she said. That allowed the wastewater main to be installed. Once that was done, de-watering equipment would be removed and the groundwater would return to its usual level.
Shannon said the work was approved by Environment Canterbury (ECan) and was expected to be completed by December 14. Further de-watering may be needed when building foundations were installed.
She said the water was spread across the park, rather than pumped into the nearby Avon-Heathcote Estuary, to minimise the potential for sediment build up in the estuary and other linked waterways.
The process complied with Christchurch City Council and ECan requirements.
De-watering was related only to the construction of the new school, and had no impact on future flood management of the site.