Water quality improves at beaches

1 December 2004

Water quality at Sumner and Scarborough beaches is being upgraded to “good” and “fair”, respectively, after upgrades made at  the Christchurch Wastewater Treatment Plant.

Christchurch City Council water quality tests since April at the Treatment Plant show a significant reduction in the number of mico-organisms or bug count after upgrades made to the Treatment Plant oxidation ponds, says Environment Canterbury  coastal water scientist Lesley Bolton-Ritchie.

“The obvious assumption is that there’ll also be fewer micro-organisms discharged into the Estuary and to the beaches,” Dr Bolton-Ritchie says.

Recent upgrades to the oxidation ponds means ECan can discount the Treatment Plant discharge’s influence on Sumner and Scarborough beaches, according to Microbiological Water Quality Guidlelines.

This has allowed ECan to improve the catchment assessment for these beaches in terms of the influence the plant discharge has on the grading system. Beach grading assessments are based on five years of data collected at various points along the coast, taking into account the number of bugs in the water at any one time.

This data is then combined with the number of risks that might influence the bug count, such as the vicinity of a beach to nearby sources of pollution such as stormwater outfalls, large populations of birds, road or industrial run-off or a sewage treatment plant, she says.

Health protection officer for Community and Public Health, Geoff O’Brien, says he has been impressed by improvements made at the Treatment Plant, after seeing the results of tests.

He is confident with the decision to upgrade Sumner and Scarborough, however continued monitoring would be carried out to provide certainty that those beach grades are justified. “The Council, ECan and Community and Public Health will continue to work together to monitor the quality of water at beaches for recreational purposes,” Mr O’Brien says.

City Council Acting Water and Waste Unit Manager, Bruce Henderson says the improved beach grading at Sumner and Scarborough is an excellent outcome for the community as a result of extensive work at the Treatment Plant. 

Although risks at these beaches were not high previously, the removal of the treatment plant as an influence on those grades will provide confidence in the quality of the water at the beaches.

“This improved wastewater discharge quality will also provide confidence that the proposed new Ocean Outfall will have a minimal environmental effect” Mr Henderson says.

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