Old pipes threaten new water plant

Ruapehu Bulletin, Volume 10, Issue 476, 9 March 1993, Page 1

Old pipes threaten new water plant

While the new Ohakune water treatment plant is producing good quality water, th,e 30-year old pipes leading to it are causing major problems which, if not fixed, could damage the plant. At their meeting last Thursday the Waimarino Community Board recommended that up to $83,000 be made available to fix

the water main and provide pressure protection for the new plant. Air pockets in the old line leading from the intake to the plant are constricting the flow, leading to pressure waves up to 700 KPa hitting the plant. These massive pressure waves had already damaged one bank of filters at the plant, and could cause

further damage if not stopped, the board heard. The resolution passed was that: • Action be taken to carry out a physical survey of the pipeline and the installation of extra air valves at the estimated cost of between $8000 and $12,000 be approved.

• Depending on the results of the physical survey and air valve installation, extra pressure relief provision be made at an estimated cost of $27,000. • The order of spare parts for the damaged diatomaceous earth filters be made and that repairs and upgrading be carried I out at the estimated cost ; of $44,000 on the satisfactory resolution of the problems with the water main. This is subject to the condition that Council's position as to the insurance and legal liabilities of the contractor (that built the plant) be established before any purchase action is taken. • The additional works be funded by way of a supplementary loan to the Ruapehu District Works Loan 1991 - .$1,100,000. The survey is to find the high spots in the eight-inch asbestos water main where air pockets are believed to build up. Air valves would be installed to release the air. This could cost $12,000. "Extra pressure relief provision" would be to provide protection to the new water plant. It would include a pressure surge valve and a surge tank. The contract to build the plant included the specification to provide

Old pipes lead lo plant damage

From page 1 "appropriate surge protection", but this had proved to be inadequate due to the "excessive and unpredictable nature of the surgings", said the report to the board. This could cost $27,000.

The DE filters would need to be repaired to provide the "required treatment quality". Because of the 10-week delivery time for this equipment, these should be ordered now, said the report. This could cost

$44,000. The council can raise a supplementary loan of up to 10 per cent of the original loan, under local government rules, the board heard. Because of the specification for the treatment plant that "appropriate surge protection to be provided", the contractor or its insurers could be liable for some or all of the costs associated with the extra pressure relicf provision and the repairs to the DE filters. This could. amount to

$71,000. Because of the possibility of further damage to the plant, plus the imminent start to the carrot washing season, the repairs have to be put in train now, the board was told. 'To do nothing is not an option," said council financial director Chris Ryan. At the start of the discussion of the issue board member Ben Goddard stressed that the report was headed "Ohakune Water Supply

Raw Water Main". He said the plant was working fine. Council engineer Peter Jackson confirmed that the plant was working fine, and that the ultra violet treatment plant was working very well, despite the lack of the DE filters. Tests on the water were being carried out weekly rather than the usual monthly round. Mr Jackson said he believed the problem was due to the pipe behaving in a different way to before. Previously it was

gravity feed to the town whereas now the plant uses suction pumps to draw water up to it, in addition to the gravity feed. Mr Goddard said some ex-Ohakune Borough Council staff had talked about pressure waves ih the old pipe. "They said there used to be rumbles down the pipe and that the pressure valve (near Thames Street) would bounce around." 'Tm sure the pressure waves were happening

before but the characteristics of the draw-off has altered," said Mr Jackson. The engineer was asked if another opinion should be sought. "They're very competent and very able people - I don't think you'll get anyone better," Mr Jackson said defending the contractors. "You've got a good contractor and good designer - there are a few flaws but I believe we are going to get around them."

Rangataua drains tenders Tenders for Nei Street, Rangataua drainage construction should be advertised for soon, the Waimarino Community Board heard at their last meeting. Board chairman Colin Webb said the work was urgent and needed to be done soon, before winter. Board member Winstone Oliver called for a report on the feasibility of spraying the Rangataua drains, to avoid later clearing work.