We call the water in the old tip site leachate. Leachate is the solution formed when water percolates through a permeable medium. When derived from solid waste, in some cases the leachate may be toxic or carry bacteria.

Objectives and goals

• To improve water quality and public safety



• To treat leachate in house and keep our problems to ourselves



• To utilise natural biological treatment methods where possible



• To improve the amenity of the parklands while incorporating the leachate treatment system



• Protect the Darebin Creek

Constituents of Darebin Parklands Leachate

Although some of the pollutants listed below cause the hairs on the back of your neck to stand up most are at very low levels and are not out of the ordinary for urban areas, especially landfill sites. Several heavy metal readings recorded in the past have been high but recent tests have shown that levels have dropped significantly and these metals are now suspended within the treatment system where they will have to remain for now.

Some of the pollutants beneath the surface of Darebin Parklands

NB: the levels of the components are not indicated.

*Indicates where the level of the constituent has exceeded United Nations recommendations

Pollutants

Oils	Greases	Flocculants
PCBs	Organics	Non-organics
Nitrite	Saltpeter	Preservatives
Polymers	Industrial solvents	Industrial inks and dyes
Resins	Tannins	Ammonium
Nitrate	Phosphates	Boron
Potassium	Arsenic

Heavy Metals

Iron	Nickel*	Zinc*
Chromium*	Mercury	Bromine
Aluminium	Phosphorus	Calcium
Magnesium	Manganese	Sodium
Chlorine	Flourine	Cadmium
Copper	Molybdenum	Lead*
Sulfur

Darebin Parklands Historical Timeline

1906	Quarrying begins for bluestone (basalt)
1933	Spring water struck at south end at depth of 34 metres
1948	Tunnel dug to drain water
1953	North end excavated where the duck pond is located
1963	City of Northcote leases the site as a municipal tip
1964	License is granted for a domestic rubbish tip by State Government
1972	Environmental Protection Authority is formed
1973	Quarry works finish, Rockbeare Conservation Group is Formed
1975	Last rubbish accepted and tip officially closed
1978	Darebin Parklands Interim Committee formed
1978	Capping of the tip site begins
1984	Capping finishes
1987	EPA abatement notice was served to City of Northcote for waste water infringement to Darebin Creek within Darebin Parklands
1989	Treatment system designed by Darebin Parklands ranger
1993	City of Darebin was formed and confronts liabilities
1997	$275 000 allocated by Darebin Council
1998	Treatment system completed
2000	Total leachate generation from the system reaches 30 million litres
2001	Suspicions arise over the excess water supply recorded within the system, subsequent investigations confirm a recharge from the local aquifer
2003	Carbon Trickle Filter program to commence

Problems for leachate treatment at Darebin Parkland

• The system works best in the warmer months and with the best results on hot windy days. During the winter months the metabolism of the plants in the system slows down and their luxury take up ability stops (they use up less water from the system).



• The western wall of the tip site is full of salt peter. This was dumped by abattoirs and directly adds to the sodium making the leachate brackish by the time it reaches the sumps (which are on the eastern side). These salty conditions make plant growth difficult.



• In warmer months various algal blooms can cause dangerous conditions for water birds. These conditions encouraged by the high level of phosphorus that can be present in the water.



• Colour is one of the major problems confronting us in the treatment process.



• Colour is hard to remove and causes water stratification. This means that the light does not penetrate deep into the water bodies, thus dark surface water absorbs much of the heat from sunlight (eg 27°C), and the deeper waters become significantly colder (eg 11°C at one metre).



• Organics in the water can cause bacterial activation. The bacteria use virtually all the oxygen in the water producing an anaerobic (and smelly) incubator.



• Macro invertebrate levels remain very low due to the low amount of oxygen in the water. High populations generally reflect a healthy wetland environment.



• The system was designed to treat far less water than it currently has to deal with. There is currently three times the planned quantity



• Due to the importance of the public open space of Darebin Parklands, allocating more land to increase the capacity of the system.



• Public ignorance toward signage in the park results in rangers having to direct dog walkers away from the leachate treatment ponds. Often dogs are found swimming in the leachate ponds.

Leachate facts, figures and points of interest.

• A system of 12 pumps is dedicated to the leachate system with the most powerful having a capacity of 20,000 litres per hour.



• There is over four kilometres of electrical conduit and pipes servicing the system all of which is underground.



• The system was originally designed to treat 8 million litres per annum, in 2000, 32 million litres were treated.



• Wetland 1 was the first pond in Victoria to be granted permission by the EPA to be constructed on top of a landfill site.



• Darebin Council funded the project with $275 000, and Parks Victoria contributed an extra $10 000 to improve the amenity of the system.



• The boardwalk crossing near wetland one is built on an old hydraulic bus servicing lift.



• 60 000 plants have been planted into the system so far.



• The biofilter was originally filled with 20 tonnes of lignum peat transported from Queensland. As this is a non renewable resource, brown coal char from Bacchus Marsh will now be used.



• The Leachate system costs $20 000 per annum to operate. Most of the costs relate to rebuilding pumps. Wear and tear is significant due to the caustic nature of the water.



• The Ranger in Charge devotes half of his working hours to managing the Leachate system. Subsequently, a Park Assistant has been employed to help maintain the park.


The penalty from the EPA for allowing leachate into the Darebin Creek is $20 000 per day.


• Over 100 mega litres have been through the system in the three years November 1998 - December 2001.



• Salts are the hardest constituents to treat, resulting in brackish water dominating the pond system.



• Ammonium levels at the sumps are 460mg/L, after the treatment process, this has been reduced to 60 mg/L.



• Pumping the leachate into the sewerage system would cost 11 cents per litre and $13 000 per annum in license fees which would amount to $3.3 million a year to Darebin Council.



• The bubbling in the Duck Pond is methane gas that is generated within the tip site from the decomposition of organic materials. It is non-toxic and a viable fuel source if contained in high concentrations.