Costly reme­dies for Ash­hurst Do­main

The Tribune (NZ) - - YOUR PAPER, YOUR PLACE - JA­NINE RANKIN

The cost of pro­tect­ing the Ash­hurst Do­main from fur­ther ero­sion by the Manawatu River has been es­ti­mated at as much as $800,000, and pos­si­bly ris­ing.

Hun­dreds of me­tres of the lower do­main were swept away in flood­ing caused by the rem­nants of Cy­clone Deb­bie in the first week of April.

It com­pounded dam­age that had oc­curred in two pre­vi­ous win­ters, to the dis­gust of lo­cal man Gary Tan­ner, who said the de­lays in act­ing to pro­tect the banks were ‘‘in­com­pe­tence’’.

On Wed­nes­day, Palmer­ston North City coun­cil City Net­works gen­eral man­ager Ray Swadel will out­line the pro­posed so­lu­tions and costs to coun­cil­lors.

The op­tions pro­posed by Hori­zons Re­gional Coun­cil range from $260,000 to $800,000.

Hori­zons is only pre­pared to con­trib­ute up to $80,000 of the costs, as the area is out­side its flood-man­age­ment scheme bound­aries.

Swadel said there were still ques­tions about why the 700-me­tre sec­tion of the Manawatu River, from where it joined the Po­hang­ina River to the State High­way bridge, were out­side the scheme.

And there were also is­sues about river man­age­ment de­ci­sions that had al­lowed gravel de­posits to build up in the mid­dle of the river, forc­ing the main flow to­ward the do­main.

But he said those is­sues would have to be set aside or worked around in or­der to get a re­sult.

The cheaper of the two op­tions is a se­ries of wil­low-tree struc­tures an­chored with rail­way irons and wire-rope ties, to pre­vent ero­sion.

Hori­zons ad­vice was that the struc­tures, known as groynes, would need a high level of mon­i­tor­ing and main­te­nance, and car­ried some risks of fail­ure.

The more ex­pen­sive op­tion was rock lin­ing of the ex­posed bank.

Swadel said con­tin­ued ero­sion since the price of the works was es­ti­mated meant that the size and cost of the works could have in­creased.

Given the lim­ited bud­get avail­able from Hori­zons, the costs to city coun­cil ratepay­ers could range from $182,000 to $720,000, or more.

The other po­ten­tial source of money could be the New Zealand Trans­port Agency.

Late last year, the agency had con­sid­ered ad­vice that there was no im­me­di­ate risk to the State High­way bridge ap­proaches that would war­rant it con­tribut­ing to the cost of bank pro­tec­tion.

How­ever, the fur­ther ero­sion ex­tend­ing much closer to the western bridge abut­ment this month has prompted the agency to re­con­sider its de­ci­sion.

Swadel said the ero­sion was con­tin­u­ing even dur­ing mod­est river flows and there was clearly a need to do some bank pro­tec­tion work as soon as pos­si­ble.

He said so­lu­tions would be dis­cussed at a three-way meet­ing be­tween the two coun­cils and the agency. ‘‘The lo­cal com­mu­nity is ex­pect­ing ac­tion re­gard­less of which author­ity has jurisdiction over this mat­ter.’’

But Swadel said what­ever so­lu­tion was agreed, noth­ing could be done be­fore Septem­ber at the ear­li­est. ‘‘The op­por­tu­nity to work on the site has now been lost un­til the lower river flows in spring.

‘‘Hori­zons do not be­lieve there are any in­terim works that can be un­der­taken to ar­rest the cur­rent ero­sion.’’

The works would take four to six weeks to com­plete.

PHOTO: DAVID UN­WIN/FAIR­FAX NZ

There is a lot of sig­nif­i­cant dam­age to land around the Manawatu river near Ash­hurst Do­main af­ter heavy rain.

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