Land purchase to allow water storage expansion

Wellington Regional Council is to buy more than 200 hectares of land near its Te Marua water treatment plant to allow for future expansion of water storage capacity

Councillors agreed at a meeting today to initiate negotiations with AgResearch to purchase 207 hectares not far from its two existing water storage lakes at Te Marua.

The decision allows the regional council to exercise an option it has held to buy the land at a yet-to-be-agreed market value.

Chair Fran Wilde said the deal would give the regional council greater flexibility in providing water for a growing population in the four cities – Wellington, Porirua, Lower Hutt and Upper Hutt – to which it supplies bulk water.

“Our Stuart Macaskill lakes have a combined capacity of 3,200 million litres. Buying the land will allow us the option of building a single 5,000 million litre lake at the western end as well as two smaller lakes, with a combined capacity of 3,000 million litres, at the eastern end.

“Geotechnical investigations have already confirmed the feasibility of the single big lake, and we intend to do the same work where we could locate the two smaller ones.

“The great advantage of the smaller lakes is that we could increase our capacity incrementally and with a much smaller increase in debt.”

The smaller lakes could be built for a combined cost of $56 million, or $30 million and $26 million separately, while the single large lake would cost $120 million – which would include $30 million to enlarge capacity at the Te Marua treatment plant.

Construction of the $30 million lake would not be necessary before 2019 and would probably meet demand through till 2031, she said.

Construction of the $120 million lake would remain one of the regional council’s longer-term storage solutions, along with a dam on the Whakatikei River, a tributary of the Hutt River, which has a current projected cost of $198 million.

The existing lakes provide a reserve to use in the event that Hutt River flows are too low to allow sufficient water to be taken to meet demand. The lakes are also useful when heavy rain upstream results in dirty water in the river. Clearer stored water can be drawn into the plant for treatment until the river returns to normal.

Construction of additional lakes would meet the latest earthquake standards.

The regional council is currently earthquake-strengthening the Stuart Macaskill lakes as well as increasing their capacity, at a cost of $15 million. Work is complete on one, while the other is currently being drained in preparation for upgrading. This second stage is expected to be completed by December 2013.

Ms Wilde said the regional council would remain in touch with neighbouring property owners to advise them of its plans regarding the land.