North Shore City wells now grilled

August 12, 2004

North Shore City Council wastewater engineers and safety experts have developed a simple engineering solution that should make a major contribution to protecting the health and safety of its sewer system workers and the general public.

The engineers have developed the design for a standardized safety grille for 69 of the city's sewage pumping station wet wells or sumps - and are working toward having the design accepted and approved by Australasian safety authorities.

Wastewater network operations engineer Pieter Stellingwerf says that in developing the ideal design for a protective cover for the wells - which can be up to six metres deep - it wasn't just a question of designing and installing a simple grille. The challenge was to find out whether there were any existing Australasian standards, establish whether any other local authorities were already working on the problem, and research the literature.

After finding there was little to go on, he says NSCC engineers then worked with design consultant Thor Associates Ltd to develop the design, have it accepted by the industry, approved by the Occupational Safety and Health Service (OSH); and have the grilles built and finally installed in all the city's pumping station wells.

Mr Stellingwerf says almost every council pumping station has a wet well, and these need regular inspection, cleaning and maintenance to function efficiently and reliably.

Previously most wet wells were protected only by a solid metal hatch on the outer opening, and if this was vandalized or broken open, the well could represent a serious hazard to workers or general public.

Even when opened by experienced and properly trained workers, the wells still present a potential hazard as workers could fall, suffering serious injury. And there is potential for fatalities, with one recent death occurring in Australia.

Pieter says the council's design is for a grille of stainless steel that is strong, light, lockable, able to be hinged and lifted, able to take the weight of a person falling on to it, have an opening grille small enough to prevent a boot slipping through the gap, and large enough to allow the well to be water blasted or cleaned by hose through the grille. What's more, provision has to be made to reach down and pull float valves and measuring devices up through the grille for service.

Mr Stellingwerf says the North Shore City grille design is now an accepted OSH solution, which will lead to greater safety for workers in an environment where there are already other potential hazards.

One less hazard will make wet wells safer places for all staff, contractors and public, says Mr Stellingwerf.

Other North Shore City Council staff who have worked long and hard to achieve the result were health and safety co-ordinator Blair McMichael, and wastewater network operations manager Keith Morris.

Mr McMichael says associated training and safe working procedures also apply when cleaning wet wells. Should a worker need to enter a wet well, North Shore City's confined spaces entry requirements apply.

ENDS

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