Water consultants recommend “preferred solution”

“River Recharge with Groundwater” option recommended as the preferred 50 year water supply solution. 

Technical consultants CH2M Beca has recommended Council proceed with the “River Recharge with Groundwater” option as the preferred 50 year water supply solution for Waikanae, Paraparaumu and Raumati residents.

The consultants have also said Council should buy the land for the proposed Lower Maungakotukutuku Dam to secure the site for the future.

The recommendations are contained in a major report to be considered by Council at a special meeting called for August 19.

The report is the culmination of hundreds of hours of work by consultants, TAG, Council staff, interest groups and members of the public. The final document is huge and bound, stands 60 mm high.

Mayor Jenny Rowan welcomed the report, saying it was a comprehensive review and provided a solid base for Council to make a decision “that will futureproof the source of good quality water for our Waikanae, Paraparaumu and Raumati residents.”

The consultants reviewed 40 options in stage 1. These were cut to 31 and then reduced to a short-list of six in-catchment options in line with Council policy and Otaki community feelings. This list was further reduced to four in June.

The four options were:

River Recharge with Groundwater

This involves water from the bore field being put into the Waikanae River just below the current intake pipe during periods of low river flow. This means residents will be drinking river water.

Lower Maungakotukutuku Dam

This involves creating a reservoir in a natural basin on the Maungakotukutuku Stream behind the hills of Nikau Valley. Water being stored will be released into the Waikanae River to supplement the river’s natural flow as required.

Aquifer storage and recovery

This involves using the aquifer below the Waikanae area as a natural underground storage. During times of high river flow, water will be pumped into the aquifer for storage. During droughts, water will be pumped from the aquifer to supplement the river.

Extended borefield

Under this option, bore water would supplement Waikanae River water during droughts. The bore water would be treated at a new filtration plant which would dramatically improve the quality of the water, including softening to reduce damage to household appliances.

Conclusion

The report looks at each of the options in detail and comes to the conclusion that River Recharge with Groundwater “provides the most sustainable, consentable and cost effective solution.”

It recommends a number of further actions, however, that include improving the groundwater modelling.

The consultants say it is highly likely that a future Council will be faced with an equally challenging task of identifying and securing access to a new water source in the future. Given this, they recommend Council moves to secure the land for the Lower Maungakotukutuku Dam site.