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Throughout Qld, NSW and into Victoria, many areas are now damaged by floods. Though most state governments seem unprepared for this event, the Northern Territory Government has a wealth of related fact sheets. Here is a compilation of some that gardeners may find helpful.
[sourced from Northern Territory Government]
CLEANING RAINWATER TANKS INUNDATED WITH FLOODWATER
Cleaning of rainwater tanks presents a number of occupational health and safety risks, such as working in confined spaces and it is only recommended that a tank be emptied if it has been inundated by floodwater. When cleaning a rainwater tank the following recommendations should be considered:
TYPES OF TANKS
CONE SCOUR BASE:
- Are easy to clean by simply opening the cleaning outlet to allow the water to gush out with the sludge then rinse with a hose.
SMALL, FLAT-BOTTOMED:
- Can be cleaned by getting inside the tank with a bucket, shovel and broom and digging out the sludge.
- A second person should always be present to ensure the safety of the person inside the tank.
- Clean the tank early in the morning or when the area is shaded to avoid heat exhaustion.
- For light inside the tank, use a battery lantern not a flame or electric extension.
- If chemicals are being used for repairs inside, a respirator may be necessary.
- Professional tank cleaners are available in some areas.
CONCRETE TANKS:
- Could crack if it dries out. Check with the tank supplier to find out if the type you have can safely remain empty for a few weeks. It might be necessary to put water in the tank to stop it from cracking.
PLASTIC TANKS:
Will need some water or should be tied down to stop them blowing over in strong winds when they are emptied.
Disinfection If you suspect water in the tank has been contaminated
- Chlorinate by adding powdered swimming pool chlorine (calcium hypochlorite, 65% available chlorine) or liquid chlorine – sodium hypochlorite, 12.5% available chlorine).
- You should not use stabilised chlorine (chlorine cyanurates).
- Approximately 5 milligrams of chlorine per litre is needed to disinfect a 5000-litre tank, though more accurate calculations are listed in Environmental Health Information Bulletin No.8 – Disinfection of Water Tanks (NT). (This is equivalent to 7 grams of calcium hypochlorite or 40 millilitres of sodium hypochlorite per 1000 litres of water).
- A level dessertspoon may be used as an approx. measure for 7 grams of powdered calcium hypochlorite.
A lot of the chlorine may be used up during disinfection. There should be at least 0.5 milligrams per litre free chlorine, 30 minutes after the chlorine is added. Note: You can use a pool chlorine test kit to measure how much chlorine is the water. Note that milligrams per litre is the same as parts per million.
CONTACT YOUR LOCAL COUNCIL OR STATE GOVERNMENT FOR MORE INFORMATION AND ASSISTANCE
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