CH2M Beca provided assistance by finding practical solutions for a potentially contaminated clearwater pond.
Following the identification of cryptosporidium in Masterton’s reticulated water supply in 2003 CH2M Beca was engaged by Masterton District Council to assist in identifying the source of contamination and to design both interim and permanent solutions.
Time was of the essence, given concerns of local residents and councillors. CH2M Beca soon identified that a potential the source of the parasite lay in the clearwater pond. An interim solution to address the risk consisted of using recycled, locally sourced steel storage tanks to provide the necessary chlorine contact time. This, along with other actions enabled the lifting of the boil water notice and allowed the decommissioning of the old clearwater pond.
The permanent solution consisted of a 1,000 m³ reinforced concrete clearwater tank designed to provide for filter backwash operations, flow balancing and chlorine contact time. The design and construction of the tank was fast tracked to reduce the time that Masterton was dependent on their interim clearwater tank.
The new clearwater tank was designed to fit within the decommissioned clearwater pond and so was able to make use of existing pipe connections and services. The tank designers worked closely with water treatment plant staff and the construction team, Riggs Zschokke Construction Ltd, to help optimise the construction details and so reduce construction time and cost, as well as the impact on the operating water treatment plant. The tanks were completed in May 2004, to Council’s satisfaction and the benefit (and relief) of the serviced community.