Fly Ash

Slurry Pumps

Slurry pumps are commonly used in the “mining, sand, dredging, electric power, metallurgy and coal” industries.

 

Ash left behind from burning coal in the boilers was collected in the slurry pumps, which mixed water with it to create slurry. In thermal power plants like East Perth, “40% of the total coal consumption is converted into ash” but vary in composition due to differences in “the combustion process, the source of coal and precipitation technique”.

 

The slurry was then carried away by high pressure pipes across the Swan River on the Bunbury Bridge to lined settling ponds where Optus Stadium sits today. The solids would sink to the bottom, with the water above being recycled. 

 

Ash Slurry Pumps help reduce airborne ash and contamination in the surrounding environment, compared to dry methods of treatment and disposal. Some industries pump the slurry into disused quarries, whilst the construction industry have found uses for the fly ash before its turned to slurry by mixing it with cement, as what occurred when building the South Fremantle Power Station in the post WW2 years due to a shortage of resources. 

 

Fly ash is still used today as a high-performance substitute for Portland Cement (Class C), due to its self-cementing properties.

 

Lesser known is its continuing uses in grouts, masonry products, roofing tiles, asphalt concrete pavement, “filler in wood and plastic products, paints and metal casings”.

 

If fly ash wasn’t treated properly, nearby waterways were at risk of contamination when it the rained, particularly the Swan River. Some of its toxic elements could include arsenic, mercury, lead and other pollutants from the ash. 

 

It’s highly likely the Slurry Pump process and the adjacent ash ponds weren’t strictly monitored or controlled, nor adequate PPE protection worn by workers, particularly during cleaning, handling and maintenance.

 

It wasn’t until the 1970s and 1980s did the toxicity of fly ash start to be understood. Environmental health scientists began researching its heavy metal contamination, radioactivity and fine particles, resulting from coal combustion by-products. 

 

The Clean Air Act (1970) was passed in the United States, which led to a number of authorities, including the Environmental Protection Agency, researching waste products like fly ash and found it could contain arsenic, lead, cadmium, mercury and selenium. 

 

During the 1980s, as research continued its progression, scientists confirmed that when fly ash was mixed with water, it could release toxic chemicals into the groundwater.

 

In Australia, monitoring the ash ponds and disposal sites didn’t start until the 1980s. By then, the damage would’ve started decades ago in the context of East Perth and Burswood. With this in mind, the power station was just one of many major local industries who would’ve contributed to potentially toxic environmental impacts.

 

Suddenly the 23m stretch of reclaimed foreshore from the edge of the Swan River to the power station’s building, which was made from fly ash, seems so much more serious! It would’ve been so easy for containers of PCB to have also been buried in it and who else knows what!

 

The Swan River Improvement Act (1925) authorised the reclamation of land along the Swan River from East Perth to Maylands, as well as areas on the otherside of the river. The Public Works Department began reclamation work in 1927 but had to stop due to financial constraints brought on by the depression and wouldn’t resume until 1933.

 

Fly ash was used to reclaim the foreshore because there was so much of it available, it was cost effective and easily transported to the river. When added to soils, particularly sandy or silty soils, it binds well and increases the strength of each layer. As beneficial as it was turning a waste product into reclaimed land, environmental risks like leaching would apparently to be managed later.

 

During the 1930s, fly ash from the power plant was collected and bagged for consumers to use in gardens. It was “added to manure to improve the quality of compost and soil for use on mainly vegetable gardens”.

 

The East Perth Rubbish Tip was also used to dispose of fly-ash until the power station’s closure in 1981.