Valves may keep city up if quake hits

Kapi-Mana News - - NEWS - By TESSA JOHNSTONE

A small plas­tic valve in­vented by the Ja­panese could keep Porirua’s res­i­dents flush­ing after a ma­jor earth­quake.

The $ 400 valves are be­ing in­stalled in man­holes in ar­eas of Porirua which might see liq­ue­fac­tion in a large earth­quake – if any part of the waste­water net­work is taken out, the whole sys­tem comes down.

‘‘The mo­ment [man­holes] pop out of the ground you’re done – with th­ese valves you’re down but you’re not out,’’ Ca­pac­ity In­fra­struc­ture Ser­vices en­gi­neer Des Scrim­geour said.

Four valves are put into the sides of the man­holes – in a large earth­quake the lid on the valves pops off, re­liev­ing the pres­sure and let­ting wa­ter in, which stops the pres­sure build­ing up and ‘‘float­ing’’ up above the sur­face, putting them out of ac­tion.

The valves are be­ing in­stalled at 140 lo­ca­tions around the Porirua CBD and Ti­tahi Bay, at a cost of about $3000 per man­hole.

That’s value for money when you con­sider it can cost about $12,000 to fix a man­hole once it’s popped up.

Ja­panese en­gi­neer­ing cor­po­ra­tion Nip­pon Hume in­vented the techonol­ogy and 30,000 man­holes around Tokyo are now fit­ted with the valves – none of the man­holes popped out in the 7.3 earth­quake in 2012.

Porirua is the first to roll out the tech­nol­ogy but Ca­pac­ity, work­ing with im­porter Hynds NZ, is hop­ing other ci­ties in the re­gion will see its ben­e­fits.

‘‘It’s just smart business to take an old net­work and try to re­jig it to get it up to earth­quake stan­dards of to­day with prime tech­nol­ogy,’’ said Scrim­geour.

‘‘Of 30,000 man­holes [us­ing the valves in Tokyo] not one has popped out of the ground, and that’s amaz­ing.’’

Porirua mayor Nick Leggett said he was pleased Porirua was the first to be us­ing the tech- nol­ogy and it backed the re­silience work the coun­cil was do­ing.

‘‘It shows that a re­ally cost ef­fec­tive, re­silient in­vest­ment in our net­work can save you money and time later on,’’ he said.

Photo: FAIR­FAX NZ

Valu­able valve: Porirua mayor Nick Leggett with the Nip­pon Hume en­gi­neers. From left, Toshimi Abe (Nip­pon Hume), Americo dos San­tos (Hynds Pipe Sys­tems), Nick Leggett, Hiro­fumi Hayashi (Nip­pon Hume) and Sho­hei Iwasaki (Nip­pon Hume).

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