Work starts on water scheme

Ruapehu Bulletin, Volume 9, Issue 419, 14 January 1992, Page 1

Work starts on water scheme

The Auckland based firm of Water Systems Treatment and Design specialist Ltd. has been awarded the contract for the design and building of the proposed new Ohakune water treatment plant and reservoir. Preliminary tenders for the work were called in August 1991. The tender specifications were performance based, requiring the successful contractor to design and build the plant and reservoir to meet the strict performance criteria before it is taken over by the district council. Seven preliminary tenders were received and four of these were selected to present a

strong concept design. These designs were then evaluated by a working party of the Council assisted by Stu Clark, Manager of the Works Consultancy Water Treatment Centre in Trentham .The range of prices for the tenders received were $640,000 to $1.15 million. In evaluating tenders the Council considered the company profile of each tender, the effectiveness of the proposal and the price submitted. The successful tender price was $768,787 and the design was considered the most effective of all the proposals presented. This price, plus the cost of the mains work

will mean the project will cost about $1 million which is $200,000 less than the last estimate. The system consists of a two stage filtration process. The first stage will contain multimedia consisting of anthracite, sand and granite while the second stage is a diatomaceous earthfilter, consisting of finely

ground marine organisms (diatoms) which form a very fine filter capable of removing giardia cysts. The system will use a polyelectrolyte coagulant avoiding the use of the coagulant alum, which has recently received some contentious comment.

The principal means of sterilisation of the supply will be by means of ultraviolet light avoiding the unpleasant tastes sometimes associated with the use of chlorine. Work on the design of the plant started last week and the plant is scheduled to be in operation by July 1992.