Ohakune water work drags on

Ruapehu Bulletin, Volume 12, Issue 562, 15 November 1994, Page 5

Ohakune water work drags on

Ruapehu Construction Limited and council staff have been working together to improve the operation of the Ohakune water treatment plant, the Waimarino Community Board heard at their last meeting. They have been logging the weather, river conditions, status of the plant and the treatment parameters and performance, in the hope that this exercise will "establish the optimum coagulant dose settings for the plant under varying conditions to achieve the best possible filtration

runs and plant performance," according to district engineer Peter Jackson. He said they planned to include a submission to the 1995/96 Draft Annual Plan to install a streaming current detector which will serve to automate the coagulant dosing of the plant to lessen the necessary operator attendance. Insurance payout In his report to the Board, Mr Jackson outlined the insurance issues regarding past damage to the plant. He said as the initial pressure

surge damage events occurred within the construction period of the contract, the plant was repaired at the contractor's cost. The cost of repairs after the contract was completed totalled $43,770, and "an insurance claim for the sum of $26,395 was therefore j made to Council' s underwriters". Because they believe there was only one recorded "damage event to one filter only" the insurers were prepared to offer $13,197, stated TURNTOPAGE6

Ohakune water work drags on

FROMPAGE5 Mr Jackson. However he said the council was disputing this as the contractor had repaired the filters and that it was "only after subsequent events follo wing practical completion were the septum mounting plates rendered unusable". He said they await the insurer's reply. With regard the reservoir failure, he said the council was likely to be reimbursed from the insurers for the reservoir failure totalling $6,490.60 plus GST. He said the replacement of the reservoir liner has now become a separate issue, that it now seemed unlikely that the liner would be replaced but that the contractor would still guarantee it for 15 years.

Liaison Mr Jackson explained that liaison was continuing between the council and W ater Systems Treatment Specialists Ltd over the performance of the treatment plant. "[We] are still experiencing some difficulty with the plant filter backwash system, and the 'blinding-off of the DE filters in adverse river conditions. Council staff have been working in close co-operation with the plant operators to refine the dosing rates to the depth filters which precede the DE filters. " "The problem seems to be that in even moderate river conditions the depth filters do not get the filtered water clean enough for further treatment by the DE filters. Water Systems have generally

been very co-operative and have carried out remedial work at no cost to the council." He said council staff are "seeking the resolution of a number of design/construction/operational problems with the plant prior to issuing the final maintenance certificate, the release of the final maintenance monies and maintenance bond". Chlorination helps "Apart from the problems outlined above and the need to chlorinate the supply for short periods when the filters blind off, the plant usually operates satisfactorily. Chlorination from time to time also serves to remove algal growth in the reticulation and disinfects it," stated Mr Jackson.